Language：Others   Publishing type：Research paper (scientific journal)  

The typical solar flat plate collector relies on materials like rock wool for insulation to minimize heat loss. However, the use of such inorganic materials raises substantial concerns for both the industry and the environment. Therefore, it is crucial to decrease the reliance on these inorganic materials and instead adopt readily available biodegradable materials that pose no environmental risks to the system. The current research presents the usage of agricultural waste as insulating materials for S-FPC fabrication. The novelty of this current research work is the effective utilization of agriculture waste (rice husk, stubble fibre, coco-peat, and nitrile rubber) as an insulating material for the fabrication of S-FPC. Experiments were performed with insulating thicknesses of 50 mm and 70 mm. The optimum temperature was recorded to be 50–53 °C with an average thermal efficiency of 64–66 % by using rice husk as the insulating material at 70 mm thick.

DOI： 10.1016/j.rineng.2023.101681

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In the present study, the adsorption isotherms of difluoromethane (R32) on the activated carbon (MSC 30) throughout a temperature range of 25 °C to 150 °C and pressures up to 3000 kPa are measured for possible application in adsorption cooling systems. The Dubinin-Astakhov model was used to fit the experimental data. A thermodynamic model is proposed in this study to investigate the adsorption potential under supercritical conditions. The model is validated using the isotherm data from the experiments and literatures for different working pairs. The validation results exhibited a good agreement between the proposed model and the experimental data, signifying the precision and dependability of the model. The corresponding adsorption isosteric heat model was derived and verified, taking into account both the inclusion and exclusion of the adsorbed volume correction. Furthermore, the developed models were utilized in the equilibrium analysis of an adsorption heat pump to evaluate the performance of the system in terms of the theoretical coefficient of performance (COP) and specific cooling energy (SCE). The analysis covered the driving heat source temperature ranging from 30 °C to 150 °C, with different evaporation temperatures and adsorption temperatures. The results showed that the maximum COP value of 0.47 for the adsorption heat pump system employing the MSC30+R32 pair was achieved at a desorption temperature of 115 °C, at which the SCE was 315.5 kJ·kg−1. The results can potentially improve the accuracy of predicting adsorption behavior and contribute to the development of more efficient and effective adsorption systems.

DOI： 10.1016/j.ijheatmasstransfer.2023.124873

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Activated carbon, due to its notable porosity and cost-effectiveness, emerges as a promising desiccant material. This research delves into the utilization of pinecones as a precursor for the production of activated carbon through steam activation. The resultant activated carbon samples presented a porous structure and exhibited a high water adsorption capacity, with the highest adsorption capacity reaching 0.35 kg/kg, placing it in competition with commercial silica gel. Various experimental parameters were systematically manipulated during the production process to optimize both the pore structure and water adsorption capacity of the activated carbon samples. Elevating the carbonization temperature from 700 °C to 900 °C proved effective in enhancing pore distribution and elevating water adsorption capacity. Furthermore, higher activation temperatures contributed to the formation of additional mesopores and macropores, possibly attributable to micropore enlargement through steam activation. Nevertheless, these elevated activation temperatures resulted in an undesired increment in mesopores concerning water adsorption. The extension of activation time led to increased micropore formation, albeit with concurrent disruption, culminating in heightened total pore volume and surface area. This extension shifted the water adsorption-desorption isotherm to higher relative pressure ranges, accompanied by a larger hysteresis loop. Moreover, an increased steam mass flow rate was found to enhance the pore structure and water adsorption capacity of the activated carbon. The activated carbons exhibited sigmoid-shaped isotherms, signifying their suitability for both open-cycle and closed-cycle adsorption systems.

DOI： 10.1016/j.powtec.2023.119084

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This study investigates the influence of different functional parameters of V-SP blocks on flow characteristics and heat enhancement in a rectangular duct via experimental analysis. The main focus of this work is on designing SAH using a novel multi-criteria decision-making (MCDM) method. The influence of the different geometrical parameter's e/H = 0.4–1.0, β = 5%–25 %, P/e = 4–12 on the f, Nu and η was investigated and optimized. The combination of Re = 16000, β = 0.2, P/e = 8, e/H = 0.8yielded the most significant Nu (303.70). In contrast, the combination of Re = 16000, e/H = 0.6, P/e = 12, β = 0.15 yield the lowest f (0.083). The maximum η of 2.74 was obtained using Re = 4000, β = 0.2, P/e = 8, e/H = 0.8. Choosing the most suitable SAH design alternative is a challenging task as no single option can fulfil all the attain performance criteria. To address this, a hybrid MCDM approach, namely hybrid BWM-CODAS architecture, was utilized. The design alternative A-20, having geometric and flow arrangement as Re = 16,000, β = 0.2, P/e = 8 and e/H = 0.8 gives the overall performance in addition to another examined alternative. Additionally, the implicit of the proposed decision-making framework was validated with other MCDM approaches, indicating the results' robustness.

DOI： 10.1016/j.solmat.2023.112627

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Solar energy is an important energy source for a sustainable future. The advancements of solar cells for electricity production require improvements in the cooling technology. Conventional air cooling is not able to cool the photovoltaic (PV) panels effectively. On the other hand, dew-point evaporative cooling (DPEC) can bring down the inlet air temperature below its wet bulb which makes itself an excellent candidate for PV cooling. In this work, a novel cooling configuration that consists of two wet channels: one in the cooler (conventional DPEC) to produce the pre-cooled supply air and the other at the back of the PV panel, was proposed. A physics-based mathematical model utilizing local weather conditions was developed for the system to investigate its transient performance. The cooling performance and subsequent improvement in the PV's energy efficiency of the proposed system were compared with a traditional DPEC-based cooling approach. It was observed that the proposed system can maintain an efficiency of more than 15% (with 16.7% maximum) under two environmental conditions in summer, which is an increase of 16.4% compared to air cooling. The proposed PV cooling method will help to improve the overall performance of the solar PV systems and increase renewable energy utilizations.

DOI： 10.1016/j.applthermaleng.2023.121695

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The thermogravimetric method was employed to measure the adsorption kinetics of difluoromethane (R32) on MSC30 activated carbon powder adsorbent over a wide range of temperatures (25 °C to 150 °C) and pressures (up to 3000 kPa). The accuracy of various adsorption kinetics models, including FD model, LDF model, semi-infinite model, and modified adsorption kinetics models, were assessed to compare their suitability for predicting the kinetics uptake of the MSC30/R32 working pair. Based on the fitting of the Arrhenius equation, the activation energy Ea and pre-exponential coefficient [Formula presented] were calculated to be 6262.37 (kJ·kg−1) and 0.00853 (s−1), respectively. The MSC30/R32 pair exhibited the highest diffusion time constant and adsorption rate among the common MSC30/refrigerant pairs. Furthermore, a new mass transfer coefficient model was proposed to enhance the accuracy and broaden the range of applicability of the existing model (Jribi model). Comprehensive validations were carried out using various adsorbent-adsorbate pairs over a wide temperature range. The Jribi model in conjunction with the proposed mass transfer coefficient model achieved high accuracy and precision in predicting the adsorption dynamics of diverse working pairs, both during the initial stage and near the saturation state. This study provides valuable insight into the adsorption kinetics analysis, which is essential in accurately simulating adsorption systems for various applications, including refrigeration and air conditioning.

DOI： 10.1016/j.icheatmasstransfer.2023.107148

Language：Others   Publishing type：Research paper (other academic)  

The Power-to-Gas (PTG) is one of the progressing technologies that enables the conversion of electrical energy into hydrogen or methane gas. This study focuses on the comprehensive analysis of energy efficiency, exergy efficiency, and exergy destruction rate within the PTG overall system. The investigation covers the evaluation of the wind turbine for power generation, the proton exchange membrane (PEM) employed in hydrogen production, and the methanation unit dedicated to methane production. The analysis examines the overall system as well as each individual component. By quantifying the energy and exergy efficiencies, this study provides potential improvements for maximizing the PTG system's overall effectiveness. The outcomes of this study contribute to the advancement and deployment of PTG technologies, thereby facilitating the integration of renewable energy sources and promoting sustainable energy solutions.

DOI： 10.1051/e3sconf/202346501011

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Using green biofilters can help eliminate air pollutants and improve urban air quality. In the current study, Prunus × Yedoensis capacity of phytoremediation was investigated as a bio filter of Particulate matter (PM) in spring and summer seasons in Japan. Two samples were analysed to extract three fractions of PM (coarse, fine and ultra-fine). Results showed lower deposition of PM in spring season with total of 20.2 μg.cm-2 and high proportion for fine fraction (2.5-10μm), comparing with summer season which showed a higher deposition of PM with total of 31.9 μg.cm-2. Ultra-fine fraction (0.2–2.5μm) recorded the highest values with a percentage of 23.9% of the total PM deposition. Leaf micromorphological characteristics such as, rough surface and serrated margin can enhance the Prunus × Yedoensis ability of particulate matter accretion. This study confirms that vegetation has an efficient role in improving the quality of urban air. Further structural analysis should be included to deepen the understanding of phytoremediation phenomena in plants.

DOI： 10.1051/e3sconf/202346502030

Language：Others  

Nature is still the main focus of scientific and technological research, particularly in nanotechnology and because of its remarkable properties; nanotechnology has acquired much interest in recent years. This review focuses on up-to-date overview of classification of nanoparticles, characterization, methods of preparation, characterization and application of nanoparticles. Initial section of the review gives insight on various techniques for the synthesis nanoparticles, encompassing both bottom-up and top-down approaches. Different methods for the synthesis of nanoparticles are discussed in details. Highlighting the importance of controlling shape, size, and composition to develop nanoparticles and enhance the properties of nanoparticles. These properties include enhanced surface area, unique optical, electronic, and magnetic characteristics, as well as improved mechanical properties. Understanding these attributes is essential for harnessing nanoparticles in different applications effectively. Broad spectrum of applications for nanoparticles is also discussed. Additionally, nanoparticles have found applications in catalysis, environmental remediation, and antimicrobial coatings, contributing to sustainable development and environmental protection. Overall, nanoparticles represent a progressive area of research with tremendous potential for innovation and societal impact. Our evaluation will serve as a solid reference, assisting the scientific community to comprehend the discussed topic better by showing the role of each technique in a comparable manner. As the field of nanoparticles is constantly evolving, this review incorporates the latest research, developments, and advancements up to the time of its publication. A comprehensive understanding of their properties, synthesis and applications is decisive for realizing the full potential of nanoparticles in various scientific and industrial domains.

DOI： 10.1016/j.jmrt.2023.09.291

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Heat rejection pressure is an important factor influencing the performance of a CO2 (R-744) transcritical vapor compression system. Previous relevant studies have investigated the optimum heat rejection pressure ensuring the maximum coefficient of performance (COP) and operating parameters affecting the optimum pressure value. However, studies presenting quantitatively how much energy can save when an R-744 transcritical system operates in the optimum heat rejection pressure are still rather limited. This work aims to investigate an energy-saving potential gain achieved by managing heat rejection pressure in an R-744 transcritical system and provides quantitatively how much energy can save with that. In that way, this work tries to fill out the research gap. Simulations were carried out employing prevalidated model, the system COP was investigated in various operating conditions, and the optimum heat rejection pressure securing the maximum COP was found. The optimum heat rejection pressure found in this work was compared to the existing correlations, thereby the comparison results are provided in this paper. The system's dynamic performance was also investigated in two different cases: when the expansion valve opening was regulated for the optimum heat rejection pressure, and when the valve opening was adjusted with a thermostatic expansion valve conventionally. In this study, it is observed the given system reduces the compressor power consumption by 62% when the refrigerant temperature at the main gas cooler outlet varies within a range of 33 ℃ to 45 ℃ and the evaporator temperature of 1 ℃. Consequently, in terms of energy-saving potential, this paper highlights the importance of heat rejection pressure management in an R-744 transcritical system and the significance of proper selection for the control target of an expansion valve depending on the system's operating regime.

DOI： 10.1016/j.applthermaleng.2023.121397

Language：Others   Publishing type：Research paper (scientific journal)  

Some of the previous investigations neglect the mass transfer contribution of the hydrophilic layer for modeling the Janus membrane that is used for direct contact membrane distillation (DCMD). This work studies the impact of adding such resistance on the performance of the DCMD, especially on the temperature polarization coefficient (TPC), thermal efficiency, and permeate flux. The commercial software Ansys 2020 was used to describe the transport behavior through the Janus membrane. The bulk-flow model was employed to evaluate the permeate flow through the hydrophilic layer for the first time. Simulation results were compared with the experimental results from the literature for validating the model, and a satisfactory agreement was found. Results demonstrated that the permeate flux increased by about 61.3 % with changing the porosity of the hydrophilic layer from 0.5 to 0.9 for the membrane with the lowest hydrophilic layer thickness. Moreover, the thermal conductivities of both layers contribute significantly to the DCMD's overall performance enhancement. Vapour flux might be enhanced by increasing the hydrophilic layer's thermal conductivity while decreasing the hydrophobic layer's thermal conductivity. Finally, the DCMD thermal efficiency was investigated, for the first time, in terms of both layer characteristics.

DOI： 10.1515/jnet-2023-0037

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Solar water heater (SWH) is important and low-cost technology for transforming solar radiation into heat energy that is utilized for commercial and industrial purposes. However, due to different advantages, this technology still suffers from poor thermal efficiency and thermal losses from the collector. The various reasons responsible for the poor heat transfer rate of SWH are heat losses from the system and different geometrical shapes of hindrance promoters. The researcher is working on various innovative methods to ameliorate the effectiveness of solar water heating systems (SWHS) by using various heat enhancement methods. The solar thermal conversion efficiency is found to be 70% as compared to solar electrical direct conversion system, which is around 17%. The different heat enhancement techniques, like twisted tape turbulator and their shape, etc., play a very remarkable role in ameliorating the effectiveness of SWHS. This review work abridges the previous research work with different heat enhancement techniques, including the coating effect of pipes, collector design, use of PCM, and different geometrical shapes of turbulence promoters. The twisted tape provides better η as compared to other heat enhancement techniques.

DOI： 10.1016/j.seta.2023.103293

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R-1132a is increasingly being considered as a low global warming potential component in alternative mixtures to R-23 in specialized low temperature and ultra-low temperature refrigeration systems. Though the thermodynamic properties of R-1132a were investigated in several studies up to 2018, reinvestigations have been carried out in recent years. In order to contribute toward these renewed measurements, the critical parameters of R-1132a were experimentally re-determined. Thirty-two vapor pressures from 240 K to the critical temperature, fifteen saturated vapor and six saturated liquid densities above 254 K and the PvT properties in both the vapor phase (98 points) and liquid phase (34 points) from densities of 50 kg·m−3 to 760 kg·m−3 were also measured. Specific correlations for each of these properties were optimized and compared to previously available data from the literature. Additionally, the Peng–Robinson equation of state was used to represent the aforementioned properties and further utilized to determine the enthalpy and entropy of R-1132a.

DOI： 10.1007/s10765-023-03184-4

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Adsorption heat transformer (AHT) cycles, unlike adsorption cooling cycles, upgrade the heat source to a higher temperature. Despite the renewed interest in the AHT cycles, its performance enhancement schemes along with their impacts are yet to be explored extensively. Heat and mass recovery schemes on the adsorption cooling/heating cycles have been extensively studied. However, AHT cycles are fundamentally different from those cycles since the AHT cycles employ isothermal-adiabtic processes. Thus, similar impacts of the heat and mass recovery scheme as in the cooling/heating cycles cannot be expected in AHT cycles. Therefore, the impacts and limitations of the internal heat recovery scheme on the AHT cycle are investigated in the current study. The heat recovery scheme aims to minimize the requisite uptake consumption for preheating the adsorber bed by recovering the sensible heat between two adsorber beds having different temperatures. This sensible heat exchange is modeled using modified energy-balance equations to capture the non-linearity of the adsorption process. The preheating uptake loss decreases from 0.014 kg/kg to 0.007 kg/kg at the heat source-heat supply temperature combination of 60 °C–80 °C due to the maximum possible heat recovery in the AHT cycle. As a result of the reduced preheating uptake loss, approximately 5% and 10% increase in the useful heat ratio and exergy efficiency of the AHT cycle, respectively are obtained. This modified AHT cycle further improves the performance ratio of the hybrid AHT-MED (multi-effect distillation) system from 4.6 to 4.9 at the heat source temperature of 58 °C. Furthermore, a parametric analysis of the cycle's performance metrics has been conducted for various degrees of heat recovery, representing the effect of realistic heat exchanger effectiveness during the recovery process. This study will help propel the theoretical development of the adsorption-based thermodynamic systems.

DOI： 10.1016/j.icheatmasstransfer.2023.106774

Language：Others   Publishing type：Research paper (scientific journal)  

Thermal management is critical to safety, stability, and durability of battery energy storage systems. Existing passive and active air cooling are not competent when the cooling performance, energy efficiency and cost of the thermal management system are drawing concurrent concerns. Here we propose dew-point evaporative cooling as a novel active air-cooling approach for large battery systems. Its capability of cooling the air towards its dew-point temperature with simple working principle and great electrical efficiency offers an ideal solution. Therefore, a scalable dew-point evaporative cooling technology was developed, and a large-scale cooler was constructed which could deliver 2.9–6.7 kW cooling capacity with 8.9–28.9 coefficient of performance (COP). To demonstrate its performance for battery thermal management, we took a 20 Ah lithium iron phosphate (LFP) prismatic pouch cells for a case study whose complex dynamic electrochemical and thermal responses were investigated via lock-in thermography experiments and electrochemical-thermal modeling. The potential of dew-point evaporative cooling for battery cooling was explored via the multi-physics coupling of battery and cooler models. This study elucidates that dew-point evaporative cooling can efficiently cool a battery by 3.0–13.6 °C lower than the cases with only forced convection, and control the battery operating temperature within an ideal operating range of 20–40 °C.

DOI： 10.1016/j.enconman.2023.116948

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A new isochoric apparatus was developed for measuring PvT properties of refrigerants from 240 K to 410 K. This temperature range extends measurements below ambient (~ 300 K) and overlaps with the range of other isochoric apparatuses in NEXT-RP centre of I2CNER, Kyushu University. PvT properties of four refrigerants (1,1,1,2-tetrafluoroethane, R-134a; pentafluoroethane, R-125; trifluoromethane, R-23 and 2,3,3,3-tetrafluoropropene, R-1234yf) were measured for the inner volume calculation and validation exercise. Vapour pressures of 1,1-difluoroethene (R-1132a) were measured between 240 K and 296 K (14 data points). All property measurements were conducted for heating up and cooling down phases. The expanded uncertainty values of temperature, pressure and density using the new isochoric apparatus are U(T) = 10 mK, U(p) = 1 kPa and Ur(ρ) = 0.002, respectively, where the coverage of 2 was adopted for 95% confident levels. The measured vapour pressures were fitted using Wagner-type and Antoine-type equations and compared with the published data.

DOI： 10.1007/s10765-023-03167-5

Language：Others   Publishing type：Research paper (scientific journal)  

Dew-point evaporative cooling can efficiently bring down the air temperature to near dew point through water evaporation. Most dew-point evaporative coolers employing conventional plate type configurations have approached their limit and leveled off. To further improve the performance of dew-point evaporative cooling, a novel counter-flow tubular architecture is proposed in this paper. Based on the momentum, energy and mass balances, a rotating axisymmetric mathematical model is established for the new cooler. The heat and mass transfer process in the cooler is analyzed and compared with that of a conventional plate-type cooler. The cooling intensity, evaporation intensity and convective heat and mass transfer coefficient are discussed to elucidate the advanced cooling behavior of a tubular cooler. The results show that: (1) for ambient air with 30.0–38.0 ℃ temperature and 12.0–20.0 g/kg humidity, the product air temperature of a tube-type dew-point evaporative cooler is 1.6–3.0 ℃ lower than that of a plate-type, and the dew-point effectiveness is 0.18 higher; (2) the working air of the tubular cooler reaches humidity saturation at 0.05 m after entering the wet channel, which is significantly shorter than the plate structure by 0.25 m; (3) in the tubular wet channel, the channel length that achieves active cooling is longer than that of a plate-type cooler, and its convective heat and mass transfer coefficient are above 150 W/(m2·K) and 0.04 m/s respectively, i.e., 30 W/(m2·K) higher and 2.7 times to the plate-type cooler.

DOI： 10.1016/j.applthermaleng.2023.120064

Language：English  

DOI： 10.60203/ngrfr_en.2023

Language：Japanese  

DOI： 10.60203/ngrfr_ja.2023

Language：Others   Publishing type：Research paper (scientific journal)  

Thermally driven desiccant- and evaporative cooling-based technologies are promising greener and cheaper alternatives to compressor-based systems due to the separate handling of latent and sensible loads. Desiccant air-conditioning (DAC) systems comprise a desiccant dehumidifier, a sensible cooling unit, a heat source for regeneration, and a heat recovery unit. These components of a DAC system can be arranged in various ways to give different configurations with varying advantages and disadvantages. In this study, five configurations of thermally driven desiccant dehumidifier- and dew point evaporative cooling (DPEC)-based DAC systems were investigated. Seven evaluation criteria namely regeneration temperature, desiccant moisture removal capacity, COPt, DPEC L/H, heat exchanger UA, system size, and fan power requirement were employed. Results show that the standard cycle in ventilation mode offers the highest COPt despite having the highest regeneration temperature. Recirculation of the return room air can operate at a significantly lower regeneration temperature at the expense of larger equipment size and much lower COPt. DAC with an internally cooled dehumidification can operate at low regeneration temperature at the expense of higher fan power and slightly lower COPt. Dividing the dehumidification process into two stages can offer operation at moderately lower regeneration temperature without severely affecting the other criteria. This study can serve as a guide for the selection of an appropriate DAC configuration for space cooling depending on the objective criteria and the resources available.

DOI： 10.1007/s44189-022-00011-7

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Humidification-dehumidification desalination (HDD) systems offer a feasible approach for the production of fresh water in inaccessible areas as they can be operational using renewable energy and require little maintenance. Various studies are being carried out to boost the system performance. In this paper, an open air open water HDD system is proposed that exploits the enhanced evaporation and condensation processes by implementing with the Maisotsenko cycle (M-cycle). The system utilizes solar energy as the energy input to heat the saline water. A thermodynamic model is formulated under steady-state conditions, considering the first and second law of thermodynamics. The energetic and exergetic performance of the system is studied. The model is first validated with the experimental data and a good agreement is found where the maximum discrepancy is about 6.0 %. Effects of different operating conditions on key performance parameters such as the Gain Output Ratio (GOR), specific energy consumption (SEC), exergy destruction, and exergy efficiency are analyzed. An improvement is observed in the GOR when the inlet air temperature is raised at constant humidity ratio. The system exhibits better performance in dry air environment when compared with humid air environment. The analysis shows a maximum mass flow rate of desalinated water of 22.3 kg/h, recovery ratio (RR) of 0.223, GOR of 3, SEC of 0.23 kWh/kg and an exergy efficiency of 43.21 %.

DOI： 10.1016/j.seta.2022.102141

Language：Others   Publishing type：Research paper (scientific journal)  

PvT properties, saturated densities, and critical parameters of R1132(E) were measured with two kinds of experimental apparatus. Along eight isochores between 65 and 832 kg m−3, PvT property measurements were carried out in the temperature range from 310 to 400 K and at pressures up to 6.5 MPa by the isochoric method. The saturated-vapor and saturated-liquid densities were determined by the visual observation of meniscus disappearance and by the break point of the PvT property isochores in the temperature range from 304 K to the critical temperature and in the density range from 65 to 833 kg m−3. The critical temperature and density were also determined as Tc = 348.82 ± 0.01 K and ρc = 438 ± 3 kg m−3 on the basis of the meniscus disappearing level as well as the intensity of the critical opalescence.

DOI： 10.1016/j.ijrefrig.2022.05.012

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Recovery of the low-temperature waste heat for electricity generation has been gaining a significant interest. An Inverted Brayton Cycle (IBC) is often employed to convert the low-temperature waste-heat to electricity while the thermal efficiency and specific work output are poor. In this paper, a new energy recovery scheme is introduced incorporating the IBC with a Regenerative Heat and Mass Exchanger (RHME). The RHME is a heat and mass exchanger that consolidates a recuperator (for thermal efficiency improvement) and an Indirect Evaporative Cooler (for enhanced specific work). Numerical models for RHME and the IBC were judiciously developed where possible condensation in the product air channel was accounted for. The model was validated with the experimental data and the cycle was investigated for various waste-heat sources (50–150 °C). When compared to a conventional air-cooling IBC system, incorporating the current energy recovery scheme increases the thermal efficiency from 8.13% to 14.36% and specific work output from 10.38 to 12.46 kJ/kg equivalent to 76.63% and 20.1% improvements, respectively. The unprecedented performance improvement is realised from the exploitation of the regenerative and air-saturation (cooling) mechanisms for both energy recovery and cooling of the working fluid.

DOI： 10.1016/j.energy.2022.123726

Language：Others   Publishing type：Research paper (scientific journal)  

Adsorption process can be initiated either by Large Temperature Jump (LTJ) or Large Pressure Jump (LPJ). In this study, a theoretical analysis of coupled heat and mass transfer process during LPJ driven adsorption has been carried out using scaling principles of the governing conservation equations. A columnar domain consisting of silica gel (adsorbent) and water vapour (adsorbate) pair has been considered with heat and mass transfer directions orthogonal to each other. This domain is subjected to a sudden LPJ with isothermal boundary condition. Adsorption process has been divided into three phases for scaling analysis viz. i) pressure equalization ii) adsorption accompanied by heat generation and iii) heat removal phase. From order of magnitude arguments, various important physical scales for each phase have been derived and validated with a 2-dimensional computational fluid dynamics (CFD) study. The temperature rise in the adsorber bed is found to be 14.5 K, and the time scale to attain peak temperature is ~100 s from the initiation of adsorption. This justifies the short cycle time deployed in practical PSA systems to operate near isothermal condition. The outcomes of this investigation serve as a fundamental insight into LPJ driven adsorption process and help identify the various factors which practically effect this mode of adsorption.

DOI： 10.1016/j.icheatmasstransfer.2022.106101

Language：Others   Publishing type：Research paper (scientific journal)  

Measurements of PvT properties, saturated pressures, saturated densities, and critical parameters were carried out for R-13I1 (trifluoroiodomethane; CF3I). Forty-seven PvT property data in the one-phase region along seven isochores for R-13I1 were obtained in the temperatures between 310 and 405 K, pressures up to 6392 kPa, and densities between 48 and 1784 kg·m-3using the isochoric method. Thirty-seven saturation pressure data for R-13I1 were obtained in the temperatures between 240 K and the critical temperature and pressures between 58 kPa and the critical pressure. Twenty-six saturated density data for R-13I1 were obtained by the observation of meniscus disappearance and the inflection points of the isochore in the densities between 48 and 1784 kg·m-3. On the basis of these measurements, the critical temperature, critical density (critical molar volume), and critical pressure of R-13I1 were determined as Tc= 396.495 ± 0.010 K (with a coverage factor, k = 2), ρc= 865 ± 5 kg·m-3(vc= 226.5 ± 1.3 cm3·mol-1) (bracketed interval), and Pc= 3971 ± 3 kPa (with a coverage factor, k = 2), respectively. Moreover, a correlation for the saturation pressure and correlations for the vapor liquid coexistence curve were established by optimization techniques.

DOI： 10.1021/acs.jced.2c00182

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The authors regret the typo error of one data at T=320.11 K in Table 3. The corrected table is as follow; No other error is found. All figures and equations in this article were made based on the correct data set. The authors would like to apologise for any inconvenience caused.

DOI： 10.1016/j.ijrefrig.2021.01.027

Language：Others   Publishing type：Research paper (scientific journal)  

R1132(E) (trans-1,2-difluoroethylene, C2H2F2) is a potential next generation refrigerant to be utilized in air conditioning applications. This hydrofluoroolefin (HFO) refrigerant possesses an extremely low-GWP value below 1 and it is an excellent candidate for replacing R32 in blends such as R410A, which are subjected to local and international greenhouse gas regulations for limiting global warming. Two isochoric apparatus were used to measure the saturation pressures of R1132(E) from 240 K to its critical temperature. At the critical temperature, the critical pressure of R1132(E) was also directly measured. Twenty-four saturation pressures including the critical point were used for optimizing a Wagner-type equation representing the saturation pressure curve. The absolute average deviation of the saturation pressures of R1132(E) predicted by the model using the fitted parameters and the experimental data is 0.02%. The optimized Wagner-type equation of saturation pressures is used for determining the acentric factor of R1132(E) as 0.2433, which is further utilized for the prediction of the saturation pressures using the Peng-Robinson cubic equation of state within an absolute average deviation of 0.31%.

DOI： 10.1016/j.ijrefrig.2021.12.014

Language：Others   Publishing type：Research paper (scientific journal)  

Multi-effect distillation (MED) systems are considered to be the most energy-efficient thermal desalination methods. This paper introduces the development of a novel thermal desalination system for performance superior to MED systems for the same operating temperature limits. Such an unprecedented achievement was attained by upgrading the heat source using the chemical potential of adsorption phenomena. The proposed Adsorption Heat Transformer (AHT) cycle hybridized with Multi-effect distillation system (AHT-MED) exhibits higher performance ratio and water production rate than a conventional MED system for the same heating source and sink. The heat generated by the heat of adsorption with the temperature higher than the heat source is supplied to the first effect of the MED system, thus, extending the temperature difference between the Top Brine Temperature (TBT) and Bottom Brine Temperature (BBT). The higher temperature difference offers more number of effects, with the equivalent temperature difference between the effects (ΔTe) as the design parameter. Using the low-temperature heat source (as low as 58 °C), the system can employ an increased number of effects (as high as 11) due to the supply of heat at an increased temperature of around 80 °C. The proposed system achieves a higher performance ratio (approximately 5.4) and water production rate (2 kg/s) compared to the standalone MED system (PR: 4.2, WPR: 1 kg/s) with the number of effects of the hybrid system as 10 at constant interstage temperature difference between the standalone and hybrid systems. This novel AHT-MED system opens up new possibilities for low-temperature heat source-driven thermal desalination with significantly improved performance.

DOI： 10.1016/j.apenergy.2021.117744

Language：Others   Publishing type：Research paper (scientific journal)  

Desiccant dehumidification systems can be utilized for decoupling moisture removal duty from the conventional mechanical vapor compression systems. Dehumidification using desiccant dehumidifiers is expected to exhibit a better energy efficiency. However, the high energy needed in the regeneration process limits its applicability. To realize the full potential of this technology, it is necessary to develop materials that can be regenerated using heat sources under 70 °C. In this study, activated carbons (ACs) derived from waste biomass were developed as desiccant materials. The ability of activated carbon (AC) to remove the moisture was controlled by carefully preparing the material to achieve the right operation window for optimum moisture sorption processes. The porous and surface characteristics of the newly-prepared AC were analyzed and compared with those of silica gel. The adsorption isotherm measurements were conducted, and the data were fitted with Henry–Sips and Do–Do isotherm models. The current ACs exhibit an excellent water adsorption capacity (up to 0.41 g/g). The efficacy of the ACs for dehumidification applications was assessed using the weather data from several regions of Indonesia, from North Sumatera to Papua. The results revealed that under the studied conditions, the new desiccant material showed a better dehumidification capacity than silica gel. Moreover, the reported AC can be regenerated using temperatures as low as 40 °C, which is readily available from waste heat, including the heat rejection from the condenser of an air-conditioning unit.

DOI： 10.1016/j.egyr.2021.09.003

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This paper presents a rigorous exergy analysis of a vapor compression refrigeration system (VCRS) for the AHRI standard cooling operating conditions assessed with a constant cooling load of 50 kW. A comprehensive mathematical model has been developed to evaluate thermodynamic variables of the major components. The analysis is carried out for widely used refrigerants, namely R12, R22, R134a, R152a, R410A; next-generation low GWP refrigerants R32, R1234yf, R1234ze(E); and two natural refrigerants R600a and R744 (CO2). First law analysis and exergetic efficiency at cycle and component level are investigated for all the refrigerants. The results indicate that R600a is the best, followed by R152a, R1234ze(E), and R1234yf in terms of COP, total exergy destruction, and exergetic efficiency. Moreover, the total equivalent warming impact (TEWI), which is the aggregation of direct impact due to refrigerant leakage and indirect impact due to electricity usage, from each system has also been assessed. The lowest and highest amount of TEWI has been found for R600a and R12 systems, respectively. This study also indicates that CO2 is a prospective future refrigerant for its lower emission, affordability, availability, non-toxicity, non-flammability, and system compactness when the VCRS is powered by electricity generated from nuclear/renewable sources.

DOI： 10.1016/j.ijrefrig.2021.08.014

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Indoor air humidity plays a vital role in determining occupants’ health and industrial product quality. Removing excess humidity by adsorption dehumidification is still facing a challenge in finding a suitable material with high adsorption capacity and low regeneration temperature. In this study, the theoretical dehumidification capacity of prepared acorn nutshell-based activated carbons was calculated and compared with silica gel type RD and RD-2060. The calculation was based on the outdoor air condition in two Asian capital cities: Jakarta and Tokyo. The theoretical study found that prepared activated carbon has better dehumidification performance under Jakarta conditions using regeneration temperatures of less than 60°C. Under Tokyo conditions, activated carbon shows auspicious performance during the summer season. Compared with silica gels, acorn nutshell-based activated carbon has a better dehumidification capacity to process high humidity ambient air with a lower regeneration temperature.

DOI： 10.1016/j.ijrefrig.2021.08.012

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Owing to its high energy efficiency without using greenhouse gases, dew point evaporative cooling offers a desired solution for thermal management of electronic and electrical devices. This paper elucidates the transient behavior of a dew point evaporative cooler and its significant influence on the dynamic cooling performance. A large time constant (400 s) of the product air temperature was observed under a zero-state response, leading to a pronounced deviation of the time-average cooling performance below its steady state by 13.8%–26.4% over a long period (2500 s). To capture this phenomenon, a modified transient lumped parameter model and a new partial differential exergy model were developed. An air mixing process in the dry channel was identified to account for the slow cooler's transient responses. A detailed exergy analysis revealed that the specific exergy destruction at the dry channel entrance was above 400 W/kg, owing to the air mixing. This finding demonstrates that the transient behavior should be judiciously considered in the cooler design and optimization, together with the steady-state performance. Accordingly, a detailed sensitivity analysis of the cooler's objective variables is proposed to gain insights into the future improvement of the dew point evaporative cooler.

DOI： 10.1016/j.enconman.2021.114471

Language：English  

DOI： 10.18462/iir.HFO.2021.1023

Language：Others   Publishing type：Research paper (scientific journal)  

The energy consumption during the start-up and cabin pull-down operation of an air-conditioning system (A/C) for electric cars was studied in this work. An entire system model consisting of a CO vapor compression system (VCS), air handling unit (AHU), and the cabin was established utilizing an acausal, object-oriented, and equation-based modeling platform. A previously validated model was adopted for the VCS. AHU and cabin models were established by paying attention to the latent heat load, humidity, and dehumidification. The models were validated against the data from three different studies. A set of transient simulations was carried out for the start-up and cabin pull-down operation periods. It is found that the initial temperature of the cabin significantly influences the energy consumption and pull-down time. When the cabin target temperature decreases from 25 °C to 21 °C, the compressor consumes 58% more energy, and the pull-down time increases by 23%. Increasing the initial temperature 35 °C to 55 °C leads to 150% longer pull-down time, and 289% more energy consumption. The initial RH of the cabin air has a negligible impact on the pull-down time, but affects energy consumption. Increasing the RH from 33% to 66% results in 9% energy consumption. 2

DOI： 10.1016/j.applthermaleng.2021.116825

Language：Others   Publishing type：Research paper (scientific journal)  

Low-temperature refrigeration (aka, deep-freezing) have an essential role in the food and pharmaceutical industries. Considering environmental and economic concerns, Carbon Dioxide (R744) has presented itself as a competent refrigerant. Even though many researchers performed extensive investigations on the performance of the low-temperature refrigeration cycles, the innovations in this field still exist, and refinement and examination of new layouts remain a hot topic, among which coupling an ejector with the cycle is a popular method that has shown promising results. This article proposes a new layout for low-temperature refrigeration together with the thermodynamic studies on the effects of changing pressures before and after the ejector by introducing an additional compressor, gas cooler, and turboexpander to the conventional layout of transcritical CO ejector cycle. The coefficient of performance (COP) around 1.4 was obtained for evaporation at −45 °C. The first law analysis of the cycle was conducted, and optimal values for pressures before and after the ejector were identified. It was found that using a compressor and a gas cooler before the secondary entrance of the ejector is beneficial to COP, and the expansion process right after the ejector will affect the COP. It was discovered that the instant expansion after ejector is unnecessary at optimum conditions, and the phase condition of the ejector's discharge has a huge impact on the performance. Optimization and parametric analysis of the cycle was conducted, and the effects of efficiencies of the cycle's components on COP were investigated. A simple and comprehensive second Law analysis of the proposed system is included, and the performance of the setup was briefly compared with other cycles in low-temperature refrigeration. It was revealed that this single-refrigerant proposed cycle not only can reach a reasonable performance for deep-freezing applications, but also it has 10% less compression ratio than its R744 counterparts. 2

DOI： 10.1016/j.applthermaleng.2020.116531

Language：Others   Publishing type：Research paper (scientific journal)  

In this study, we evaluated the performance of low Global Warming Potential (GWP) refrigerant R1234yf on the activated carbon (MSC‐30) for adsorption heating applications. The ad-sorption isotherms of MSC‐30/R1234yf were measured using a constant‐volume–variable‐pressure (CVVP) method from very low relative pressure to the practical operating ranges. The data were fitted with several isotherm models using non‐linear curve fitting. An improved equilibrium model was employed to investigate the influence of dead thermal masses, i.e., the heat exchanger assembly and the non‐adsorbing part of the adsorbent. The model employed the model for the isosteric heat of adsorption where the adsorbed phase volume was accounted for. The performance of the heat pump was compared with MSC‐30/R134a pair using the data from the literature. The analysis cov-ered the desorption temperature ranging from 60 °C to 90 °C, with the evaporation temperature at 5 °C and the adsorption temperature and condensation temperature set to 30 °C. It was observed that the adsorption isotherms of R1234yf on MSC‐30 were relatively lower than those of R134a by approximately 12%. The coefficient of performance (COP) of the selected pair was found to vary from 0.03 to 0.35 depending on the heat source temperature. We demonstrated that due to lower latent heat, MSC‐30/R1234yf pair exhibits slightly lower cycle performance compared to the MSC‐ 30/R134a pair. However, the widespread adaptation of environmentally friendly R1234yf in auto-mobile heat pump systems may call for the implementation of adsorption systems such as the direct hybridization using a single refrigerant. The isotherm and performance data presented in this work will be essential for such applications.

DOI： 10.3390/app11052279

Language：Others   Publishing type：Research paper (scientific journal)  

In conventional ejector refrigeration cycles, the ejector mostly operates at fixed pressure points in the secondary stream and outlet. Studying the sensitivity of the system to the pressure alternation of the mentioned points has not been investigated. To cover this gap, an extra turboexpander, compressor, and gas cooler were introduced to the conventional ejector layout. It was found that pressurizing the secondary entrance of the ejector could be beneficial to COP if it is not warmer than the gas coolers. Also using the expansion process right after the ejector has the potential to increase the efficiency of the system if the discharge pressure of the ejector reaches supercritical or superheat condition.

DOI： 10.5109/4372280

Language：Others   Publishing type：Research paper (scientific journal)  

Adsorption cycles have been gaining significant interest in waste-heat recovery and renewable energy utilization. Adsorption isotherm data and the equilibrium cycle analysis are crucial steps in evaluating a typical adsorbent + adsorbate pair. In this paper, the performance of Maxsorb III + R245fa and spherical activated carbon, SAC-2 + R245fa were studied for adsorption cooling and adsorption heat transformer (AHT) cycles. Adsorption isotherms of these pairs were measured using the constant-volume-variable-pressure apparatus for temperatures ranging from 30 °C to 60 °C, and fitted with the Dubinin–Astakhov (D–A) and the Tóth isotherm model. An improved equilibrium model was developed, accounting the effects of thermal masses. The specific cooling energy (SCE) and the coefficient of performance (COP) of the adsorption cooling cycle were evaluated for various thermal mass to adsorbent mass ratios. It is observed that SAC-2 + R245fa pair offers better SCEs (20 kJ kg and 160 kJ kg at 60 °C and 90 °C, respectively) when compared to that of Maxsorb III + R245fa. The impact of thermal mass is found to be significant for all regeneration temperatures for Maxsorb III + R245fa while the deterioration of COP in SAC-2 + R245fa is notable for high regeneration temperatures (> 75 °C). When employed in the AHT cycle, Maxsorb III offers a slightly higher useful heat while SAC-2 provides a better Q /Q albeit by a small margin. The Q /Q values for both studied pairs are more than 0.6 for all regeneration temperatures for the heat extraction at 120 °C. −1 −1 uh QR uh QR

DOI： 10.1016/j.ijrefrig.2020.12.005

Language：Others   Publishing type：Research paper (scientific journal)  

Research trends in the heat pump systems can mainly be categorized into the developments of the cycle and the working fluids. Regional and global watchdogs regulate the fate of working fluids in the name of environmental issues, especially global warming. Examples include the Montreal Protocol, the Kyoto protocol, and lately, the European “F Gas” Directive (No. 542/2006). The urgent and pressing call is next-generation refrigerants that are benign to the environment without compromising the performance. Pure substances are known to be limited, while refrigerant mixtures have been gaining significant attention due to their flexibility in tuning flammability, stability, and low GWP values. In this work, we investigated a ternary mixture of HFC-32/HFO-1234yf/R744 (22/72/6mass%) with the targeted GWP less than 150. Three operation modes (cooling for summer, Cooling, low-temperature heating, Heating#1, and high-temperature heating, Heating#2 for winter) were investigated experimentally. Optimal refrigerant charge amounts for all operation modes followed by the system performance were evaluated from part-load to full-load operations. The system is further scrutinized using the 2 Law of Thermodynamics by tracking exergy destructions in major components. Among the selected operation modes, Heating#1 provides the highest system COPs for all loads due to the lower lift and smaller temperature difference between the inlet and outlet of the coolant to the condenser. The cycle exergetic efficiencies were 31.7%, 37.8%, and 43.3% for Cooling, Heating#1, and Heating#2 modes, respectively. The results presented in this work will be useful in the refrigerant design (ternary mixtures) and the system development for low-GWP refrigerant applications. nd

DOI： 10.1016/j.ijrefrig.2020.10.009

Language：Others   Publishing type：Research paper (scientific journal)  

Domestic heat pumps constitute a significant part of the global heat pump industry. R401A offers excellent performance with no influence on the ozone depletion and has been a dominant refrigerant in most domestic heat pumps. However, R410A has a significant impact on the climate due to its high global warming potential (GWP). Thus, the heat pump industry has been focusing on the development of R410A substitutes. Pure refrigerant alternates, such as HFC32, and the blends mixed with low-GWP refrigerants, such as HFO1234yf and HFO1234ze(E), are widely reported. Besides the direct impact of refrigerants (which is estimated as GWP), domestic heat pumps indirectly affect the environment from the energy consumption and manufacturing processes. Hence the life cycle climate performance (LCCP) analysis accounts for all emissions through the lifetime of a heat pump. This article reports the LCCP evaluation of various low-GWP refrigerants for R410A replacement on domestic heat pumps. Six refrigerants, i.e., HFC32, binary blends of HFC32 and HFO1234yf (with GWP values of 300, 200 and 150), and HFC32 and HFO1234ze(E) with GWP values of 300 and 200, were compared against R410A. The performance data of these refrigerants from the experimental heat pump facility were utilized to evaluate the LCCP. Among the selected refrigerants, the binary blend of HFC32/HFO1234ze(E) with GWP 300 shows the lowest LCCP. Low-GWP refrigerants would become more competitive than R410A when CO emission from energy generations can be reduced by the optimization of the system or the usage of renewable energy. 2

DOI： 10.1016/j.ijrefrig.2020.09.020

Language：Others   Publishing type：Research paper (scientific journal)  

Refrigeration and air-conditioning systems become an integral part of modern society. Electricity-driven vapour compression systems have been dominating the heating, ventilation, air conditioning and refrigeration (HVAC&R) industry. The working fluids of these systems often contribute to the environmental issues in the forms of direct and indirection emissions. Pure refrigerants are often limited in meeting criteria such as efficiency, flammability, toxicity, and compatibility. Meanwhile, refrigerant mixtures offer flexibilities to tune these criteria, and the reusability of the existing hardware is often a priority in practice. We evaluated a binary mixture of HFC32 and HFO1234yf with a target global warming potential (GWP) under 150 for domestic heat pumps. Drop-in tests were conducted for two modes; Heating#1 and Heating#2 at different condensing temperatures. The performance of the current binary refrigerant was compared with those of target refrigerants, i.e., R410A, HFC32 and the binary mixture of HFC32/HFO1234yf (22/78 mass%, GWP = ~300) for part- and full-load operations. Experimental results showed that the performance of the present refrigerant is comparable with R410A and HFC32 for high condensing temperatures, especially at part-load operations. The system COP of the current binary blend exhibits from 6 to 14% drop as compared to that of R410A. A significant increase in the system irreversibility losses was observed with the increasing percentage of HFO1234yf. Despite the relatively low performance, the GWP of the present refrigerant is below 150, and it can be used in the existing systems without significant hardware changes while meeting tighter environmental regulations.

DOI： 10.1016/j.applthermaleng.2020.115952

Language：Others   Publishing type：Research paper (scientific journal)  

A high-pressure lift often triggers an increased power input to the vapor compression systems. The increased power consumption becomes a bottleneck in R-744 refrigeration systems for freezing and refrigeration applications. Meanwhile, phase change materials (PCM) offer operation flexibility in the form of the compressor run-time from the energy storage potential. In this article, the energy-saving potential of the PCMs on a cascade refrigeration system using CO is investigated focusing on the impacts of charge amounts and the thermal resistance of the PCM. The validated dynamic model in Simscape™/MATLAB for an R-744 vapor compression system is adopted for a cascade refrigeration system together with the validated PCM model. In the studied system, the PCM is installed in the storage compartment as a thermal buffer. The comprehensive model employed an acausal, object-oriented, and equation-based paradigm adopting detailed heat transfer characteristics. The effect of PCM on the compressor running time was investigated under the cyclic steady-state operating conditions. The results showed that the compressor “On-time” ratio decreases when using the PCM; subsequently, the power reduction. The system consumes about 6.76 kWh (without PCM) and 5.93 kWh with PCM; thus, the power consumption decreases by 12.3%. The threshold PCM charge ratio is observed to be 1. Increasing the PCM charge value above this threshold does not trigger a significant decrease in power reduction. The increase in the overall thermal resistance of PCM has a negative impact on the “On-time” ratio and power consumption. The benefit of PCM is insignificant for thermal resistance above 0.02 K W . Despite the shortcomings of several assumptions involved, the present results clearly highlight the positive impacts of the PCM in terms of power savings for low-temperature refrigeration applications using R-744. 2 −1

DOI： 10.1016/j.applthermaleng.2020.116104

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.5109/6622876

Language：Others   Publishing type：Research paper (scientific journal)  

Adsorption thermal energy storage plays a vital role in supporting the availability of renewable energy. Activated carbons produced from local waste biomass have been attracting considerable attention in adsorption technology due to their unique properties and sustainability. However, their limitation in water vapor uptake hinders the practical application of this material. In this work, acorn nutshells were utilized as a base material to produce activated carbon. Air oxidation was performed as a versatile and low-cost technique to enhance the material's properties and water adsorption capacity. By applying air oxidation as a post-treatment during material production, the amount of active functional groups and the water adsorption on activated carbon has been successfully enhanced. From the theoretical calculation, it is found that activated carbon–water working pairs shown promising performance to be used for adsorption thermal energy storage applications. The adsorption of water vapor on the post-treated-activated carbon releases the isosteric heat between 2400 kJ/kg to 2500 kJ/kg. Moreover, this study's working pair can be driven by a temperature of less than 50 °C. From the results, it is confirmed that by controlling the adsorbent's surface properties, activated carbon–water working pairs can be a promising way to provide alternative material and reduce the energy demand for driving the system.

DOI： 10.1016/j.egyr.2020.11.038

Language：Others   Publishing type：Research paper (scientific journal)  

The vapor–liquid equilibrium properties of R32/R1123 binary refrigerant mixtures were precisely determined. Such mixtures have the potential to provide a reduced global warming potential although data regarding their properties is extremely limited, especially with regard to vapor–liquid equilibrium characteristics such as boiling point and dew point pressures, for which no actual experimental data exist. The present study acquired such data by means of two recirculation type apparatuses located at different universities. One apparatus, which was used to measure data in high temperature region, is installed at Toyama Prefectural University and includes an optical cell and two circulation loops with a thermostatted liquid bath. After thermal equilibration, a part of the sample in both loops is sandwiched between two valves and mixed with helium, following which the compositions are determined using gas chromatograpy. The other apparatus, which was for lower temperature region, at Kyushu University, has a similar design. The vapor–liquid equilibrium data were obtained between 300 and 330 K using the apparatus for high temperatures and from 273 to 313 K using the apparatus for low temperatures. These data were compared with predictions from the Helmholtz-type equation of state and a systematic deviation of approximately 1% was observed at low temperatures. A regression analysis using the binary interaction parameter k for the modified Peng–Robinson equation of state more accurately reproduced the present measurement results. ij

DOI： 10.1016/j.ijrefrig.2020.07.005

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.5109/4842514

Language：Others   Publishing type：Research paper (scientific journal)  

A new model of adsorption isotherms Type IV and V is proposed as a basis for theoretical calculations and modelling of adsorption systems such as adsorption heat storage and heat pumps. As the current models have decent yet limited applicability, in this work, we present a new combined model with universal use for micro-mesoporous silica/water adsorption systems. Experimental measurement of adsorption isotherm of water onto seven different samples of micro and mesoporous silica and aluminium-silica were used to fit new adsorption models based on a combination of classical theories and a distribution function related to the pore-size distribution of the selected materials. The fitting was conducted through a repeated non-linear regression using Trust Region Reflective algorithm with weighting factors to compensate for the scalability of the adsorption amount at low relative pressure with optimization of the absolute average deviation fitting parameter. The results display a significant improvement for most of the samples and fitting indicators compared to more common models from the literature with average absolute deviation as low as AAD = 0.0025 g g for material with maximum uptake of q = 0.38 g g . The newly suggested model, which is based on a combination of BET theory and adjusted normal distribution function, proved to bring a higher degree of precision and universality for mesoporous silica materials with different levels of hydrophilicity. − 1 − 1

DOI： 10.3390/en13164247

Language：Others   Publishing type：Research paper (scientific journal)  

The objective of the present manuscript is to develop a dynamic model to simulate the transient performance of a heat pump system that utilizes environmental-friendly refrigerant, Carbon Dioxide (R-744). Exploiting the high customizability of the modeling tools supporting acausal, equation-based, and object-oriented modeling approach, a dynamic model for a transcritical heat pump system was developed. The model was validated with the experimental results with particular attention to the refrigerant mass flow rate, cooling/heating capacity, compressor power, and the coefficient of performance.

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.5109/6792805

Language：English   Publishing type：Research paper (scientific journal)  

To properly address the threat of global warming, there is an urgent need to reduce CO₂ from the atmosphere through the development of environment-friendly technologies. Therefore, capturing/storage and utilization of CO₂ as a refrigerant for adsorption cooling/heating technologies have been gaining momentum in the last decades. This study focuses on the development of novel activated carbons (ACs) with extremely large pore volume and high surface area from environment-friendly and abundantly available biomass precursor seeking higher CO₂ adsorption capacity. Four AC samples are synthesized from the two biomass precursor's namely waste palm trunk (WPT) and mangrove (M) employing potassium hydroxide as an activating agent. The porous properties of the synthesized ACs are investigated from the N₂ adsorption/desorption data. It is praiseworthy to elucidate that the highest surface area and pore volume for biomass-derived ACs (BACs) are obtained 2927 m² g⁻¹ and 2.87 cm³ g⁻¹, respectively. CO₂ adsorption characteristics are investigated using a high precision magnetic suspension balance unit at five different temperatures ranging from 25 to 70 °C with various pressures. The WPT-AC (C500)/CO₂ pair shows the highest adsorption uptake as high as 1.791 g g⁻¹ (excess adsorption) and 2.172 g g⁻¹ (absolute adsorption) at 25 °C and 5.04 MPa, which is superior to any other ACs reported to date. To the best of our knowledge, porous properties and adsorption uptake of CO₂ reported in this study are the up-to-date benchmarks. The results show that novel BACs/CO₂ pairs possess remarkably high adsorption performance, which will contribute towards the advancement of various adsorption-based technologies.

DOI： 10.1016/j.apenergy.2020.114720

Language：Others   Publishing type：Research paper (scientific journal)  

In this paper, 182 pvTz data (28 data in the two-phase region and 154 data in the superheated vapor region) of mixtures containing difluoromethane (R32) and trans-1,3,3,3-tetrafluoroprop-1-ene (R1234ze(E)) are reported. The measurements were carried out along 10 isochores (0.013173, 0.039422, 0.043115, 0.046522, 0.062966, 0.068225, 0.068959, 0.110447, 0.115156, and 0.121732 m ·kg ) in the temperature range from 263 to 373 K for 10 R32 mole fractions (0.1677, 0.2360, 0.2551, 0.4634, 0.5374, 0.6715, 0.7383, 0.7544, 0.9532, and 0.9533). The flash method with three equations of state (EoSs) was used to assess the vapor-liquid equilibrium of the binary mixture under analysis. The calculated vapor-liquid equilibrium behavior for the R32 + R1234ze(E) binary system agreed with the experimental data collected from the open literature. The vapor-phase measurements were correlated through the aforementioned EoSs and a truncated virial EoS. These pvTz points agreed with both the values provided by the EoSs and REFPROP 10.0. 3 -1

DOI： 10.1021/acs.jced.9b00995

Language：Others   Publishing type：Research paper (scientific journal)  

The inverted Brayton cycle can be applied to exploit the exergy content of the waste heat. The cycle can be operational at low heat source temperatures, and it is particularly suitable for recovering the low-temperature waste heat. Being low temperature-driven, the thermal efficiency of such an inverted Brayton cycle is considerably low. In this study, an attempt has been made to improve the performance of the cycle by hybridizing with an indirect evaporative cooling (IEC) device. A counter-flow type indirect evaporative cooler is introduced to the inverted Brayton cycle to condition the working fluid prior to the compressor inlet. Detailed numerical models for both cycles were developed and validated with the experimental data of Riangvilaikul and Kumar for a counter flow IEC. The performance of the present configuration is compared with various methods of cooling the working fluid such as the conventional air cooling and a recuperator. The proposed cycle exhibits a significant improvement in terms of the specific work output (45%) for all turbine inlet temperatures regardless of the inlet air conditions, while a higher thermal efficiency can be realized for low-temperature heat source below 85 °C.

DOI： 10.1016/j.applthermaleng.2020.115029

Language：Others   Publishing type：Research paper (scientific journal)  

To properly address the threat of global warming, there is an urgent need to reduce CO from the atmosphere through the development of environment-friendly technologies. Therefore, capturing/storage and utilization of CO as a refrigerant for adsorption cooling/heating technologies have been gaining momentum in the last decades. This study focuses on the development of novel activated carbons (ACs) with extremely large pore volume and high surface area from environment-friendly and abundantly available biomass precursor seeking higher CO adsorption capacity. Four AC samples are synthesized from the two biomass precursor's namely waste palm trunk (WPT) and mangrove (M) employing potassium hydroxide as an activating agent. The porous properties of the synthesized ACs are investigated from the N adsorption/desorption data. It is praiseworthy to elucidate that the highest surface area and pore volume for biomass-derived ACs (BACs) are obtained 2927 m g and 2.87 cm g , respectively. CO adsorption characteristics are investigated using a high precision magnetic suspension balance unit at five different temperatures ranging from 25 to 70 °C with various pressures. The WPT-AC (C500)/CO pair shows the highest adsorption uptake as high as 1.791 g g (excess adsorption) and 2.172 g g (absolute adsorption) at 25 °C and 5.04 MPa, which is superior to any other ACs reported to date. To the best of our knowledge, porous properties and adsorption uptake of CO reported in this study are the up-to-date benchmarks. The results show that novel BACs/CO pairs possess remarkably high adsorption performance, which will contribute towards the advancement of various adsorption-based technologies. 2 2 2 2 2 2 2 2 2 −1 3 −1 −1 −1

DOI： 10.1016/j.apenergy.2020.114720

Language：English   Publishing type：Research paper (scientific journal)  

The inverted Brayton cycle can be applied to exploit the exergy content of the waste heat. The cycle can be operational at low heat source temperatures, and it is particularly suitable for recovering the low-temperature waste heat. Being low temperature-driven, the thermal efficiency of such an inverted Brayton cycle is considerably low. In this study, an attempt has been made to improve the performance of the cycle by hybridizing with an indirect evaporative cooling (IEC) device. A counter-flow type indirect evaporative cooler is introduced to the inverted Brayton cycle to condition the working fluid prior to the compressor inlet. Detailed numerical models for both cycles were developed and validated with the experimental data of Riangvilaikul and Kumar for a counter flow IEC. The performance of the present configuration is compared with various methods of cooling the working fluid such as the conventional air cooling and a recuperator. The proposed cycle exhibits a significant improvement in terms of the specific work output (45%) for all turbine inlet temperatures regardless of the inlet air conditions, while a higher thermal efficiency can be realized for low-temperature heat source below 85 °C.

DOI： 10.1016/j.applthermaleng.2020.115029

Language：English   Publishing type：Research paper (scientific journal)  

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.5109/4774209

Language：English   Publishing type：Research paper (scientific journal)  

Demands of standalone dehumidification systems have been increasing in order to realize energy savings in air-conditioning processes. In a desiccant dehumidification system, the water vapor from the moist air undergoes a phase change phenomenon, this being from vapor to adsorbed phase, a process analogous to latent heat exchange. The energy exchange involved in such a process is often significant-up to 80% of the total energy exchange. In this study, the influence of the phase change phenomena involved in a desiccant dehumidification system was evaluated experimentally, along with the performance investigation under low desorption air temperatures of 308, 318, 328, 338, and 345 K. The system was driven by a constant adsorption temperature of 293 K. The dehumidification ability, latent heat ratio, and latent effectiveness were employed as key performance indexes. The results showed that with the increased desorption temperature, the latent heat ratio decreased, whereas the dehumidification ability and latent effectiveness increased. The highest latent heat ratio was found to be 0.61 at the desorption temperature of 308 K, whereas the highest latent effectiveness was obtained at the desorption temperature of 345 K. A suitable temperature for the effective and efficient dehumidification was observed to be 318 K for the current system.

DOI： 10.3390/app10030868

Language：Others   Publishing type：Research paper (scientific journal)  

Demands of standalone dehumidification systems have been increasing in order to realize energy savings in air-conditioning processes. In a desiccant dehumidification system, the water vapor from the moist air undergoes a phase change phenomenon, this being from vapor to adsorbed phase, a process analogous to latent heat exchange. The energy exchange involved in such a process is often significant-up to 80% of the total energy exchange. In this study, the influence of the phase change phenomena involved in a desiccant dehumidification system was evaluated experimentally, along with the performance investigation under low desorption air temperatures of 308, 318, 328, 338, and 345 K. The system was driven by a constant adsorption temperature of 293 K. The dehumidification ability, latent heat ratio, and latent effectiveness were employed as key performance indexes. The results showed that with the increased desorption temperature, the latent heat ratio decreased, whereas the dehumidification ability and latent effectiveness increased. The highest latent heat ratio was found to be 0.61 at the desorption temperature of 308 K, whereas the highest latent effectiveness was obtained at the desorption temperature of 345 K. A suitable temperature for the effective and efficient dehumidification was observed to be 318 K for the current system.

DOI： 10.3390/app10030868

Language：English   Publishing type：Research paper (scientific journal)  

Specific heat capacity (C_p) of the adsorbents plays a vital role in the adsorption heat pump (AHP) systems design. This paper focuses on the experimental investigation of the C_p of parent materials and consolidated composite adsorbents at a temperature ranging from 30 to 120 °C. Here, the parent materials are highly porous adsorbent, namely Maxsorb III, thermal conductivity enhancers (TCEs) such as expanded graphites and graphene nanoplatelets, and binders, namely polyvinyl alcohol and polyvinylpyrrolidone. In addition, several consolidated composites are synthesized by varying the mass fraction of the adsorbent, TCE, and binder materials. Experimental C_p data of parent materials and composites are fitted with a widely used Tomeczek and Palugniok (TP) equation, and fittings show good agreements. Moreover, a generalized equation is proposed to calculate the C_p of composite adsorbents. Finally, experimental data of composites are fitted with the proposed equation, and the fittings show good agreements. These experimental data and the proposed equation are very crucial for the researchers to perform accurate AHP simulation, analysis, and compact system design.

DOI： 10.1016/j.applthermaleng.2019.114431

Language：Others  

This article presents the thermophysical properties and adsorption characteristics of high grade activated carbons (ACs) derived from waste biomass. The thermophysical properties include surface area, pore volume, pore size distribution, and thermal conductivity. The adsorption characteristics of ethanol and CO2 onto biomass-derived ACs are experimentally investigated for a wide range of temperatures and pressures for adsorption heat pump and CO2 capture applications. The porous properties and adsorption performance analysis confirmed that these ACs are superior to any other ACs reported in open literature. Moreover, these ACs are low-cost and made from renewable precursor materials, namely waste palm trunk (WPT) and mangrove (M). The presented information is an invaluable resource for the students, academics and industrial scientist interested in characterizing new ACs for various energy conversion and conservation applications.

DOI： 10.1016/B978-0-12-803581-8.10832-X

Language：Others  

This article presents the detailed synthesis procedure of high grade activated carbons (ACs) derived from biomass precursors, namely waste palm trunk (WPT), and mangrove (M) which are abundantly available in nature. For synthesizing ACs, the possible activation methods such as physical and chemical along with various activating agents are discussed in detail. In this article, ACs are synthesized by chemical activation method under an inert atmosphere using potassium hydroxide (KOH) as an activation agent in the temperature range of 600-900°C. The carbonization process is also performed under an inert atmosphere at temperatures 500 and 600°C. The yield for every stage of the synthesis, elemental composition, and scanning electron microscopy (SEM) images of both carbonized and activated samples are presented.

DOI： 10.1016/B978-0-12-803581-8.11341-4

Language：Others   Publishing type：Research paper (scientific journal)  

Specific heat capacity (C ) of the adsorbents plays a vital role in the adsorption heat pump (AHP) systems design. This paper focuses on the experimental investigation of the C of parent materials and consolidated composite adsorbents at a temperature ranging from 30 to 120 °C. Here, the parent materials are highly porous adsorbent, namely Maxsorb III, thermal conductivity enhancers (TCEs) such as expanded graphites and graphene nanoplatelets, and binders, namely polyvinyl alcohol and polyvinylpyrrolidone. In addition, several consolidated composites are synthesized by varying the mass fraction of the adsorbent, TCE, and binder materials. Experimental C data of parent materials and composites are fitted with a widely used Tomeczek and Palugniok (TP) equation, and fittings show good agreements. Moreover, a generalized equation is proposed to calculate the C of composite adsorbents. Finally, experimental data of composites are fitted with the proposed equation, and the fittings show good agreements. These experimental data and the proposed equation are very crucial for the researchers to perform accurate AHP simulation, analysis, and compact system design. p p p p

DOI： 10.1016/j.applthermaleng.2019.114431

Language：English   Publishing type：Research paper (scientific journal)  

In this paper, 182 pvTz data (28 data in the two-phase region and 154 data in the superheated vapor region) of mixtures containing difluoromethane (R32) and trans-1,3,3,3-tetrafluoroprop-1-ene (R1234ze(E)) are reported. The measurements were carried out along 10 isochores (0.013173, 0.039422, 0.043115, 0.046522, 0.062966, 0.068225, 0.068959, 0.110447, 0.115156, and 0.121732 m³·kg^-1) in the temperature range from 263 to 373 K for 10 R32 mole fractions (0.1677, 0.2360, 0.2551, 0.4634, 0.5374, 0.6715, 0.7383, 0.7544, 0.9532, and 0.9533). The flash method with three equations of state (EoSs) was used to assess the vapor-liquid equilibrium of the binary mixture under analysis. The calculated vapor-liquid equilibrium behavior for the R32 + R1234ze(E) binary system agreed with the experimental data collected from the open literature. The vapor-phase measurements were correlated through the aforementioned EoSs and a truncated virial EoS. These pvTz points agreed with both the values provided by the EoSs and REFPROP 10.0.

DOI： 10.1021/acs.jced.9b00995

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.5109/2547344

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.5109/2547344

Language：English   Publishing type：Research paper (scientific journal)  

A promising adsorbent representing a phenol resin activated with potassium hydroxide, which can be used in innovative next-generation adsorption cooling and heating pump systems, is proposed.

DOI： 10.1007/s10891-019-02076-5

Language：Others   Publishing type：Research paper (scientific journal)  

A promising adsorbent representing a phenol resin activated with potassium hydroxide, which can be used in innovative next-generation adsorption cooling and heating pump systems, is proposed.

DOI： 10.1007/s10891-019-02076-5

Language：Others   Publishing type：Research paper (scientific journal)  

Adsorption cooling system using composite adsorbent and high energy density adsorbate (CO₂) provides a significant advantage to reduce the system geometry. This study presents the adsorption characteristics of CO₂ onto synthesized composites employing graphene nanoplatelets (GNPs) and activated carbon (AC). The influence of GNPs in the composite is investigated in terms of porous properties, thermal conductivity, and CO₂ adsorption capacity. The composite 3 (50 wt% AC and 40 wt% H-25) achieves the highest thermal conductivity enhancement which is 23.5 times higher than parent AC powder. The CO₂ adsorption uptakes onto different composites are measured gravimetrically at adsorption temperatures 20–70 °C. The measured data are fitted with modified D-A and Tóth models. The specific cooling effect (SCE) and coefficient of performance (COP) are estimated for various driving heat source temperatures and two evaporation temperatures of 5 and 10 °C with a fixed adsorption/condenser temperature of 30 °C. AC-GNPs based composites are found suitable for developing compact adsorption cooling systems.

DOI： 10.1016/j.ijrefrig.2019.04.022

Language：Others   Publishing type：Research paper (scientific journal)  

Adsorption cooling system using composite adsorbent and high energy density adsorbate (CO ) provides a significant advantage to reduce the system geometry. This study presents the adsorption characteristics of CO onto synthesized composites employing graphene nanoplatelets (GNPs) and activated carbon (AC). The influence of GNPs in the composite is investigated in terms of porous properties, thermal conductivity, and CO adsorption capacity. The composite 3 (50 wt% AC and 40 wt% H-25) achieves the highest thermal conductivity enhancement which is 23.5 times higher than parent AC powder. The CO adsorption uptakes onto different composites are measured gravimetrically at adsorption temperatures 20–70 °C. The measured data are fitted with modified D-A and Tóth models. The specific cooling effect (SCE) and coefficient of performance (COP) are estimated for various driving heat source temperatures and two evaporation temperatures of 5 and 10 °C with a fixed adsorption/condenser temperature of 30 °C. AC-GNPs based composites are found suitable for developing compact adsorption cooling systems. 2 2 2 2

DOI： 10.1016/j.ijrefrig.2019.04.022

Language：English   Publishing type：Research paper (scientific journal)  

Repository Public URL： http://hdl.handle.net/2324/4480700

Language：Others   Publishing type：Research paper (scientific journal)  

The performance of an adsorption system using Maxsorb III + ethanol pair is investigated for practical heat pump applications. An adsorption system using a single bed with a single evaporator/condenser is employed and the performance of the system is assessed for various regeneration temperatures (80 °C, 70 °C and 60 °C). The impact of the adsorption time on the performance of the selected pair is further evaluated. The potential application of the present adsorbent + adsorbate pair is the automobile air-conditioning system where the exhaust waste heat will be recovered to operate the adsorption system. Thus, antifreeze fluid is employed as the heat transfer medium for the adsorber and the evaporator/condenser heat exchanger. A mathematical model is developed to estimate the uptake amount from the experimental data. The sensible heat change (thermal mass), the superheating of the refrigerant in the adsorber, the adsorber heat leak and the heat rejection to the heat transfer medium are accounted for. The uptake amount is further verified using the classical p–T–q diagram. For operation using 30 °C adsorber coolant inlet and 15 °C chilled water inlet, the cooling capacity of the present system ranges from 15 to 35 W for the adsorption times of 600 s and 300 s, respectively. It is observed that the regeneration temperature significantly influences the net uptake of the system. The maximum net uptake is recorded to be about 0.995 kg/kg for the regeneration temperature of 80 °C. The system is further assessed using the ratio of the cooling capacity to the adsorption heat.

DOI： 10.1016/j.ijrefrig.2018.06.009

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.5109/2349293

Language：Others   Publishing type：Research paper (scientific journal)  

This article discusses a direct approach for assessing irregularly shaped pore distribution of porous materials using Atomic Force Microscopy (AFM). Using the tapping mode, AFM is employed to obtain the surface topographic information of the porous materials commonly used in adsorption applications. Three different types of silica gels, commercially used silica–alumina and acetaminophen samples are investigated using an image processing technique to capture the pore size-related information. Macro and mesopores in a specified region are visualized then quantified and counted using 2-D Fast Fourier Transformation (2D FFT) technique. The results obtained by the AFM technique are then compared with the BET surface area and pore size distribution (NLDFT) extracted from the N adsorption isotherms. 2

DOI： 10.1016/j.ijrefrig.2018.08.017

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.1080/01457632.2018.1450325

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s11282-007-0065-z

Language：Others   Publishing type：Research paper (scientific journal)  

Season change significantly influences the cooling requirement and electricity consumption of supermarket refrigeration systems. Monthly total equivalent warming impact (TEWI) and system performance parameters (COP, discharge gas temperature-pressure, work of compression etc.) have been assessed for a typical supermarket refrigeration system of Tokyo, Japan. A medium temperature (–7 °C, 200 kW) and a low temperature (–25 °C, 50 kW) cooling load have been considered for the assessment. The results indicate that the monthly lowest TEWI is found in February and highest is in July for single cycle refrigeration system. The possibility of cascading for low temperature cooling load is also considered for smooth operation and longer lifetime. TEWI of past twenty years is presented to give an overview of how much global warming is originated by a mid-size supermarket.

DOI： 10.5109/2321014

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s11282-007-0065-z

Language：English   Publishing type：Research paper (scientific journal)  

Season change significantly influences the cooling requirement and electricity consumption of supermarket refrigeration systems. Monthly total equivalent warming impact (TEWI) and system performance parameters (COP, discharge gas temperature-pressure, work of compression etc.) have been assessed for a typical supermarket refrigeration system of Tokyo, Japan. A medium temperature (–7 °C, 200 kW) and a low temperature (–25 °C, 50 kW) cooling load have been considered for the assessment. The results indicate that the monthly lowest TEWI is found in February and highest is in July for single cycle refrigeration system. The possibility of cascading for low temperature cooling load is also considered for smooth operation and longer lifetime. TEWI of past twenty years is presented to give an overview of how much global warming is originated by a mid-size supermarket.

DOI： 10.5109/2321014

Language：English   Publishing type：Research paper (scientific journal)  

This paper proposes two types of seawater-coolant feed arrangements of a heat recovery unit (HRU) for improving the performance of a multi-stage vacuum membrane distillation (VMD) system: backward feed (BF) and parallel feed (PF). Theoretical studies were performed to assess the effect of the BF and PF feed arrangements on the system performance. In addition, to comprehensively understand the thermochemical phenomena in both the BF and PF arrangements, spatial variations in the temperature, permeate pressure, permeate flux, and salinity were investigated using a rigorous simulation model that considered the heat and mass transfer across the hollow fibers coupled with the transport behavior on the feed side. To determine the superior HRU configuration between BF and PF, the water production, recovery ratio, and specific energy consumption of the multi-stage VMD system were investigated. It was found that the total water production in the PF arrangement was approximately 2.94 m³/d, which was approximately 6% higher than in the BF arrangement; however, the BF arrangement was more efficient for the production of freshwater than the PF arrangement when a smaller number of module stages was employed. Furthermore, the optimum number of HRUs in the BF arrangement was determined based on this theoretical study.

DOI： 10.1016/j.seppur.2018.11.012

Language：Others   Publishing type：Research paper (other academic)  

Nowadays nanofluids are widely used for heat transfer enhancement. Nanometer-sized particles added to base fluid enhance the thermal conductivity and thus increase the heat transfer rate. In the present study TiO nanoparticle with the average diameter, 21 nm is used. Titanium dioxide (TiO ) nanofluid prepared by dispersing nanoparticles in distilled water using the two- step method with volume concentration (0.05% - 0.3%), has been investigated. The force convective heat transfer coefficient and friction factor of the TiO /Distilled water nanofluid with different volume concentration and Reynolds number for flow in a counterflow double tube heat exchanger are studied in this research. The result shows that the convective heat transfer coefficient of nanofluid is higher than base fluid for the same mass flow rate and same inlet temperature of nanofluid. The Nusselt number increases with Reynolds number and volume concentration TiO /Distilled water of nanofluid. Meanwhile, micro-fin tube increases pressure drop in the flow path. 2 2 2 2

DOI： 10.1063/1.5098218

Language：Others   Publishing type：Research paper (scientific journal)  

This paper proposes two types of seawater-coolant feed arrangements of a heat recovery unit (HRU) for improving the performance of a multi-stage vacuum membrane distillation (VMD) system: backward feed (BF) and parallel feed (PF). Theoretical studies were performed to assess the effect of the BF and PF feed arrangements on the system performance. In addition, to comprehensively understand the thermochemical phenomena in both the BF and PF arrangements, spatial variations in the temperature, permeate pressure, permeate flux, and salinity were investigated using a rigorous simulation model that considered the heat and mass transfer across the hollow fibers coupled with the transport behavior on the feed side. To determine the superior HRU configuration between BF and PF, the water production, recovery ratio, and specific energy consumption of the multi-stage VMD system were investigated. It was found that the total water production in the PF arrangement was approximately 2.94 m /d, which was approximately 6% higher than in the BF arrangement; however, the BF arrangement was more efficient for the production of freshwater than the PF arrangement when a smaller number of module stages was employed. Furthermore, the optimum number of HRUs in the BF arrangement was determined based on this theoretical study. 3

DOI： 10.1016/j.seppur.2018.11.012

Language：Others   Publishing type：Research paper (scientific journal)  

In this study, new composite adsorbent with enhanced thermal conductivity and adsorption capacity was synthesized and analyzed comprehensively for the development of compact CO based adsorption cooling system. The consolidated composite was prepared employing activated carbon, graphene nanoplatelets and hydroxyl cellulose as a parent adsorbent, thermal conductivity enhancer, and binder, respectively. The surface area and pore volume of the composite were found to be 1778 ± 13 m g and 1.014 cm g , respectively. In addition, the composite showed 233% higher thermal conductivity compared to the parent activated carbon. Adsorption characteristics of CO were measured at temperature ranging from 20 to 70 °C and pressures up to 5 MPa. Absolute uptake was evaluated from excess adsorption based on the following two methods: (i) the adsorbed phase volume is equal to the pore volume of the adsorbent; and (ii) the adsorbed phase volume is almost zero under low pressure and/or high temperature conditions. Furthermore, the averaging of above two methods was also taken for avoiding these two extreme assumptions. Obtained absolute adsorption uptake data were fitted with modified Dubinin-Astakhov and Tóth models. Results indicated good approximation between data points and models. The average isosteric heats of adsorption estimated using modified D-A and Tóth model were found to be 19.742 kJ mol and 19.023 kJ mol , respectively. The obtained characteristics of composite adsorbent are prerequisites for designing compact CO based adsorption cooling systems. 2 2 2 2 −1 3 −1 −1 −1

DOI： 10.1016/j.ijrefrig.2019.01.014

Language：Others   Publishing type：Research paper (scientific journal)  

In this study, new composite adsorbent with enhanced thermal conductivity and adsorption capacity was synthesized and analyzed comprehensively for the development of compact CO ₂ based adsorption cooling system. The consolidated composite was prepared employing activated carbon, graphene nanoplatelets and hydroxyl cellulose as a parent adsorbent, thermal conductivity enhancer, and binder, respectively. The surface area and pore volume of the composite were found to be 1778 ± 13 m ² g ⁻¹ and 1.014 cm ³ g ⁻¹ , respectively. In addition, the composite showed 233% higher thermal conductivity compared to the parent activated carbon. Adsorption characteristics of CO ₂ were measured at temperature ranging from 20 to 70 °C and pressures up to 5 MPa. Absolute uptake was evaluated from excess adsorption based on the following two methods: (i) the adsorbed phase volume is equal to the pore volume of the adsorbent; and (ii) the adsorbed phase volume is almost zero under low pressure and/or high temperature conditions. Furthermore, the averaging of above two methods was also taken for avoiding these two extreme assumptions. Obtained absolute adsorption uptake data were fitted with modified Dubinin-Astakhov and Tóth models. Results indicated good approximation between data points and models. The average isosteric heats of adsorption estimated using modified D-A and Tóth model were found to be 19.742 kJ mol ⁻¹ and 19.023 kJ mol ⁻¹ , respectively. The obtained characteristics of composite adsorbent are prerequisites for designing compact CO ₂ based adsorption cooling systems.

DOI： 10.1016/j.ijrefrig.2019.01.014

Language：English   Publishing type：Research paper (other academic)  

Nowadays nanofluids are widely used for heat transfer enhancement. Nanometer-sized particles added to base fluid enhance the thermal conductivity and thus increase the heat transfer rate. In the present study TiO ₂ nanoparticle with the average diameter, 21 nm is used. Titanium dioxide (TiO ₂ ) nanofluid prepared by dispersing nanoparticles in distilled water using the two- step method with volume concentration (0.05% - 0.3%), has been investigated. The force convective heat transfer coefficient and friction factor of the TiO ₂ /Distilled water nanofluid with different volume concentration and Reynolds number for flow in a counterflow double tube heat exchanger are studied in this research. The result shows that the convective heat transfer coefficient of nanofluid is higher than base fluid for the same mass flow rate and same inlet temperature of nanofluid. The Nusselt number increases with Reynolds number and volume concentration TiO ₂ /Distilled water of nanofluid. Meanwhile, micro-fin tube increases pressure drop in the flow path.

DOI： 10.1063/1.5098218

Language：English   Publishing type：Research paper (scientific journal)  

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.5109/2320994

Language：Others   Publishing type：Research paper (scientific journal)  

The motivation of the present paper is to synthesis high packing density and thermal conductivity consolidated composite using silica gel powder (SGP) almost without affecting its porous properties. The effect of packing density, binder type and amount on porous properties as well as thermal conductivity were studied. Four types of binder, namely Hydroxyethyl cellulose (HEC), Polyvinyl alcohol (PVA), Polyvinyl pyrrolidone (PVP) and gelatin were chosen. SGP composite with PVP 2 wt% as binder showed better performance for both porous and thermal properties. Thermal conductivity for PVP 2 wt% composite was found 32% higher than SGP. Adsorption uptake of water onto SGP and PVP 2 wt% composite at 30–70 °C adsorption temperatures were measured using gravimetric method. Tóth equation is found suitable to fit the isotherm data. Results showed that there is no change in water adsorption uptake between SGP and PVP 2 wt% composite whereas the volumetric uptake increased by 12.5% for the composite. The studied composites were found to be suitable for designing high performance adsorption cooling systems.

DOI： 10.1016/j.ijrefrig.2018.09.003

Language：Others   Publishing type：Research paper (scientific journal)  

The motivation of the present paper is to synthesis high packing density and thermal conductivity consolidated composite using silica gel powder (SGP) almost without affecting its porous properties. The effect of packing density, binder type and amount on porous properties as well as thermal conductivity were studied. Four types of binder, namely Hydroxyethyl cellulose (HEC), Polyvinyl alcohol (PVA), Polyvinyl pyrrolidone (PVP) and gelatin were chosen. SGP composite with PVP 2 wt% as binder showed better performance for both porous and thermal properties. Thermal conductivity for PVP 2 wt% composite was found 32% higher than SGP. Adsorption uptake of water onto SGP and PVP 2 wt% composite at 30–70 °C adsorption temperatures were measured using gravimetric method. Tóth equation is found suitable to fit the isotherm data. Results showed that there is no change in water adsorption uptake between SGP and PVP 2 wt% composite whereas the volumetric uptake increased by 12.5% for the composite. The studied composites were found to be suitable for designing high performance adsorption cooling systems.

DOI： 10.1016/j.ijrefrig.2018.09.003

Language：English   Publishing type：Research paper (scientific journal)  

Adsorption cooling systems powered by low-grade thermal or renewable energy are considered as a potential alternative to the vapor compression systems. To improve the performance and compactness of the system, this study focuses on the synthesis and characterization of activated carbon (AC) composite employing graphene nanoplatelets (GNPs) namely H-grade and C-grade, and polyvinyl alcohol. The influence of GNPs on the porous properties, thermal conductivity, and ethanol adsorption characteristics of composites have been experimentally investigated. Porous properties results show that the studied composites possess high surface area and pore volume with microporous nature. The C-grade contained composite shows the higher porous properties compared to H-grade, however, thermal conductivity for the later one is the highest. The highest thermal conductivity is found to be 1.55 W m⁻¹ K⁻¹ for H-grade (40 wt%) contained composite which is 23.5 times higher than that of powder AC. Ethanol adsorption characteristics on studied composites are conducted gravimetrically at adsorption temperatures 30–70 °C. Experimental data are also fitted with Tóth and Dubinin-Astakhov (D-A) isotherm models within ±5% RMSD and found 23% improvement of effective volumetric uptake for H25 (20 wt%) composite compared to parent AC. The instantaneous ethanol adsorption uptake onto composites has also been presented for adsorption temperature 30 °C and evaporator pressure at 1.8 kPa.

DOI： 10.1016/j.enconman.2018.10.092

Language：Others   Publishing type：Research paper (scientific journal)  

This study provides the surface characteristics (surface energy and the acid–base properties) of surface treated activated carbons (ACs) using inverse gas chromatography. The surface energy and the acid–base characteristic of studied adsorbents are determined by the retention time using several non-polar and polar probes at 140 °C. It is observed that the dispersive surface energy dominates for all AC samples. The treatment of Maxsorb III with H exhibits the highest basicity due to lower oxygen content on the surface. The presented results express further insights and useful information in functionalizing the activated carbon for various industrial applications. 2

DOI： 10.1016/j.jiec.2018.09.046

Language：Others   Publishing type：Research paper (other academic)  

This study experimentally investigated the effect of adsorbent height on adsorption dynamics for carbon dioxide gas (CO ) adsorption onto commercially available highly porous activated carbon powder, named as Maxsorb III. The experiments were conducted using a magnetic suspension adsorption measurement unit. Three different heights of the Maxsorb III adsorbent were used in the experiments. Experimental data were reported for adsorption temperatures of 30 °C and 70 °C and for 2 different pressure steps. It had been observed that the adsorption rate strongly depended on the height of the adsorbent. This signifies that the kinetic parameters obtained by the similar experimental measurements may not be directly applicable in designing an adsorption heat exchanger. The lower height of the adsorbent provided faster adsorption kinetics. Key performance parameter, such as the specific cooling capacity for an adsorption refrigeration system was also calculated from the experimental data. The results of the present study suggested that the adsorbent height needs to be considered while using kinetics parameters in designing adsorption heat exchanger.. 2

DOI： 10.1063/1.5086549

Language：Others   Publishing type：Research paper (scientific journal)  

Ruby in diverse geological settings leaves petrogenetic clues, in its zoning, inclusions, trace elements and oxygen isotope values. Rock-hosted and isolated crystals are compared from Myanmar, SE Asia, and New South Wales, East Australia. Myanmar ruby typifies metasomatized and metamorphic settings, while East Australian ruby xenocrysts are derived from basalts that tapped underlying fold belts. The respective suites include homogeneous ruby; bi-colored inner (violet blue) and outer (red) zoned ruby; ruby-sapphirine-spinel composites; pink to red grains and multi-zoned crystals of red-pink-white-violet (core to rim). Ruby ages were determined by using U-Pb isotopes in titanite inclusions (Thurein Taung; 32.4 Ma) and zircon inclusions (Mong Hsu; 23.9 Ma) and basalt dating in NSW, >60–40 Ma. Trace element oxide plots suggest marble sources for Thurein Taung and Mong Hsu ruby and ultramafic-mafic sources for Mong Hsu (dark cores). NSW rubies suggest metasomatic (Barrington Tops), ultramafic to mafic (Macquarie River) and metasomatic-magmatic (New England) sources. A previous study showed that Cr/Ga vs. Fe/(V + Ti) plots separate Mong Hsu ruby from other ruby fields, but did not test Mogok ruby. Thurein Taung ruby, tested here, plotted separately to Mong Hsu ruby. A Fe-Ga/Mg diagram splits ruby suites into various fields (Ga/Mg < 3), except for magmatic input into rare Mogok and Australian ruby (Ga/Mg > 6). The diverse results emphasize ruby’s potential for geographic typing.

DOI： 10.3390/min9010028

Language：Others   Publishing type：Research paper (scientific journal)  

Adsorption cooling systems powered by low-grade thermal or renewable energy are considered as a potential alternative to the vapor compression systems. To improve the performance and compactness of the system, this study focuses on the synthesis and characterization of activated carbon (AC) composite employing graphene nanoplatelets (GNPs) namely H-grade and C-grade, and polyvinyl alcohol. The influence of GNPs on the porous properties, thermal conductivity, and ethanol adsorption characteristics of composites have been experimentally investigated. Porous properties results show that the studied composites possess high surface area and pore volume with microporous nature. The C-grade contained composite shows the higher porous properties compared to H-grade, however, thermal conductivity for the later one is the highest. The highest thermal conductivity is found to be 1.55 W m K for H-grade (40 wt&#37;) contained composite which is 23.5 times higher than that of powder AC. Ethanol adsorption characteristics on studied composites are conducted gravimetrically at adsorption temperatures 30–70 °C. Experimental data are also fitted with Tóth and Dubinin-Astakhov (D-A) isotherm models within ±5&#37; RMSD and found 23&#37; improvement of effective volumetric uptake for H25 (20 wt&#37;) composite compared to parent AC. The instantaneous ethanol adsorption uptake onto composites has also been presented for adsorption temperature 30 °C and evaporator pressure at 1.8 kPa. −1 −1

DOI： 10.1016/j.enconman.2018.10.092

Language：English   Publishing type：Research paper (scientific journal)  

Ruby in diverse geological settings leaves petrogenetic clues, in its zoning, inclusions, trace elements and oxygen isotope values. Rock-hosted and isolated crystals are compared from Myanmar, SE Asia, and New South Wales, East Australia. Myanmar ruby typifies metasomatized and metamorphic settings, while East Australian ruby xenocrysts are derived from basalts that tapped underlying fold belts. The respective suites include homogeneous ruby; bi-colored inner (violet blue) and outer (red) zoned ruby; ruby-sapphirine-spinel composites; pink to red grains and multi-zoned crystals of red-pink-white-violet (core to rim). Ruby ages were determined by using U-Pb isotopes in titanite inclusions (Thurein Taung; 32.4 Ma) and zircon inclusions (Mong Hsu; 23.9 Ma) and basalt dating in NSW, >60–40 Ma. Trace element oxide plots suggest marble sources for Thurein Taung and Mong Hsu ruby and ultramafic-mafic sources for Mong Hsu (dark cores). NSW rubies suggest metasomatic (Barrington Tops), ultramafic to mafic (Macquarie River) and metasomatic-magmatic (New England) sources. A previous study showed that Cr/Ga vs. Fe/(V + Ti) plots separate Mong Hsu ruby from other ruby fields, but did not test Mogok ruby. Thurein Taung ruby, tested here, plotted separately to Mong Hsu ruby. A Fe-Ga/Mg diagram splits ruby suites into various fields (Ga/Mg < 3), except for magmatic input into rare Mogok and Australian ruby (Ga/Mg > 6). The diverse results emphasize ruby’s potential for geographic typing.

DOI： 10.3390/min9010028

Language：English   Publishing type：Research paper (scientific journal)  

This study provides the surface characteristics (surface energy and the acid–base properties) of surface treated activated carbons (ACs) using inverse gas chromatography. The surface energy and the acid–base characteristic of studied adsorbents are determined by the retention time using several non-polar and polar probes at 140 °C. It is observed that the dispersive surface energy dominates for all AC samples. The treatment of Maxsorb III with H
₂
exhibits the highest basicity due to lower oxygen content on the surface. The presented results express further insights and useful information in functionalizing the activated carbon for various industrial applications.

DOI： 10.1016/j.jiec.2018.09.046

Language：English   Publishing type：Research paper (other academic)  

This study experimentally investigated the effect of adsorbent height on adsorption dynamics for carbon dioxide gas (CO
₂
) adsorption onto commercially available highly porous activated carbon powder, named as Maxsorb III. The experiments were conducted using a magnetic suspension adsorption measurement unit. Three different heights of the Maxsorb III adsorbent were used in the experiments. Experimental data were reported for adsorption temperatures of 30 °C and 70 °C and for 2 different pressure steps. It had been observed that the adsorption rate strongly depended on the height of the adsorbent. This signifies that the kinetic parameters obtained by the similar experimental measurements may not be directly applicable in designing an adsorption heat exchanger. The lower height of the adsorbent provided faster adsorption kinetics. Key performance parameter, such as the specific cooling capacity for an adsorption refrigeration system was also calculated from the experimental data. The results of the present study suggested that the adsorbent height needs to be considered while using kinetics parameters in designing adsorption heat exchanger..

DOI： 10.1063/1.5086549

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.5109/2174851

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.5109/2174851

Language：English   Publishing type：Research paper (scientific journal)  

Emission and heat rejection from automobiles are largely responsible for urban environmental issues. Adsorption systems driven by engine waste heat exhibit huge potential to meet the demand for cabin thermal comfort while improving fuel economy. However, the mechanical vapour compression (MVC) systems are still the undisputed champions in automobile air conditioning. This paper provides a critical review on the development and progress of adsorption heat pumps specifically for automobile air conditioning. In doing so, some of the progress and development in land-based adsorption chillers (heat pump), which are not realistically relevant to automobile adsorption systems, are explicitly excluded. Matching the energy density, durability, and reliability of the MVC systems remain major hurdles. The importance of improving the energy density based on the overall system weight or volume, real-world tests under various driving modes and durability aspects are discussed.

DOI： 10.3390/app8112061

Language：Others   Publishing type：Research paper (scientific journal)  

The isosteric heat of adsorption strongly associates with the energetics of the adsorption processes. Being a direct function of the uptake amount, accurate modelling of the isosteric heat of adsorption is crucial in the design and development of adsorption systems. The isosteric heat of adsorption is often calculated using the Clausius-Clayperon equation with the perfect gas assumption and negligible adsorbed phase volume. We present a thermodynamic model of the isosteric heat of adsorption that addresses the non-ideal behaviour and the variation in the adsorbed phase density. The model is first validated using experimental data in comparison with the available models in the literature that invoke the ideal gas assumption with negligible adsorbed phase volume. Using these models, the isosteric heat for adsorption processes is examined from partial vacuum to high pressure as well as adsorption temperatures above the critical point. The impact of the prediction by each model on the system performance is then assessed in terms of the theoretical COP. For the realistic evaluation of system COP, an improved equilibrium cycle model is developed and the system performance is investigated using various models for the isosteric heat of adsorption. For adsorption at partial vacuum conditions, the COP values predicted by the ideal model are up to 1.8&#37; higher when compared to the calculations using the present model. For high-pressure adsorption below the critical temperature, for example, Maxsorb III + R134a pair, the present model predicts 13&#37; lower COP than the models available in the literature. The variation in the adsorbed phase density addressed in the present model leads to a higher value of isosteric heat (3.8&#37;–8.6&#37;) for adsorption above the critical temperature.

DOI： 10.1016/j.applthermaleng.2018.07.131

Language：English   Publishing type：Research paper (scientific journal)  

The isosteric heat of adsorption strongly associates with the energetics of the adsorption processes. Being a direct function of the uptake amount, accurate modelling of the isosteric heat of adsorption is crucial in the design and development of adsorption systems. The isosteric heat of adsorption is often calculated using the Clausius-Clayperon equation with the perfect gas assumption and negligible adsorbed phase volume. We present a thermodynamic model of the isosteric heat of adsorption that addresses the non-ideal behaviour and the variation in the adsorbed phase density. The model is first validated using experimental data in comparison with the available models in the literature that invoke the ideal gas assumption with negligible adsorbed phase volume. Using these models, the isosteric heat for adsorption processes is examined from partial vacuum to high pressure as well as adsorption temperatures above the critical point. The impact of the prediction by each model on the system performance is then assessed in terms of the theoretical COP. For the realistic evaluation of system COP, an improved equilibrium cycle model is developed and the system performance is investigated using various models for the isosteric heat of adsorption. For adsorption at partial vacuum conditions, the COP values predicted by the ideal model are up to 1.8% higher when compared to the calculations using the present model. For high-pressure adsorption below the critical temperature, for example, Maxsorb III + R134a pair, the present model predicts 13% lower COP than the models available in the literature. The variation in the adsorbed phase density addressed in the present model leads to a higher value of isosteric heat (3.8%–8.6%) for adsorption above the critical temperature.

DOI： 10.1016/j.applthermaleng.2018.07.131

Language：English   Publishing type：Research paper (scientific journal)  

This is the Issue No. 3 for Evergreen-Joint Journal of Novel Carbon Resource Sciences & Green Asia Strategy, in 2018. The present edition contains four articles diversified with review paper, catalyst performance, wind turbine performance and simulation of microwave propagation. We acknowledge contributions by the authors, reviewers, editorial team and the management team for the successful publication of this issue.

DOI： 10.5109/1957499

Language：English   Publishing type：Research paper (scientific journal)  

An adsorption chiller requires thermal energy to regenerate the adsorbent by desorbing the refrigerant vapor. Minimum desorption temperature is the parameter which defines the lowest possible heat source temperature required for driving adsorption chiller. In this study minimum desorption temperature is evaluated for different types of adsorption isotherms classified by International Union of Pure and Applied Chemistry (IUPAC). For each type, adsorption isotherm model is utilized to estimate the minimum desorption temperature and then compared to the mathematical expression reported in literature derived using Dubinin-Astakhov isotherm model. This allows for critical scrutiny of the universal validity of mathematical expression. It is observed that this expression can estimate the minimum desorption temperature with reasonable accuracy for all isotherm models.

DOI： 10.1016/j.ijheatmasstransfer.2018.01.107

Language：Others   Publishing type：Research paper (scientific journal)  

An adsorption chiller requires thermal energy to regenerate the adsorbent by desorbing the refrigerant vapor. Minimum desorption temperature is the parameter which defines the lowest possible heat source temperature required for driving adsorption chiller. In this study minimum desorption temperature is evaluated for different types of adsorption isotherms classified by International Union of Pure and Applied Chemistry (IUPAC). For each type, adsorption isotherm model is utilized to estimate the minimum desorption temperature and then compared to the mathematical expression reported in literature derived using Dubinin-Astakhov isotherm model. This allows for critical scrutiny of the universal validity of mathematical expression. It is observed that this expression can estimate the minimum desorption temperature with reasonable accuracy for all isotherm models.

DOI： 10.1016/j.ijheatmasstransfer.2018.01.107

Language：English   Publishing type：Research paper (scientific journal)  

Heat pump systems are often considered as one of the major contributors to environmental problems due to the usage of chlorofluoro, hydrochlorofluoro, and hydrofluoro carbon-based refrigerants. Earlier versions of refrigerants used to have high ODP as well as GWP. However, next generation refrigerants that are environmentally benign with excellent thermophysical properties are still under development stage. This study reviews the historical development of refrigerants, their environmental impacts and observes the viewpoint for present options in terms of Montreal Protocol, Kyoto Protocol, and EU F-gas regulation. The discussion extends to the actions of international agreements on the phase-out of hydrochlorofluorocarbons for developed and developing countries. This study also highlights the approach of large heat pump industries in Asia region regarding the use of various refrigerants. The direct CO₂ emission per year from air-conditioning and refrigeration sectors due to the system leakage is assessed. It also examines the major contributors of CO₂ emission in every year among the various sectors for providing per kilowatt cooling effect. Finally, the ideal cycle performance is compared to various refrigerants and stated the current best option.

DOI： 10.5109/1936218

Language：Others   Publishing type：Research paper (scientific journal)  

Heat pump systems are often considered as one of the major contributors to environmental problems due to the usage of chlorofluoro, hydrochlorofluoro, and hydrofluoro carbon-based refrigerants. Earlier versions of refrigerants used to have high ODP as well as GWP. However, next generation refrigerants that are environmentally benign with excellent thermophysical properties are still under development stage. This study reviews the historical development of refrigerants, their environmental impacts and observes the viewpoint for present options in terms of Montreal Protocol, Kyoto Protocol, and EU F-gas regulation. The discussion extends to the actions of international agreements on the phase-out of hydrochlorofluorocarbons for developed and developing countries. This study also highlights the approach of large heat pump industries in Asia region regarding the use of various refrigerants. The direct CO emission per year from air-conditioning and refrigeration sectors due to the system leakage is assessed. It also examines the major contributors of CO emission in every year among the various sectors for providing per kilowatt cooling effect. Finally, the ideal cycle performance is compared to various refrigerants and stated the current best option. 2 2

DOI： 10.5109/1936218

Language：English   Publishing type：Research paper (scientific journal)  

The performance of a solar hot water system is assessed for heat pump and domestic heating applications. Thermodynamic analysis on a serpentine-type thermosyphon flat-plate solar heater is conducted using the Second Law of thermodynamics. Exergetic optimization is first performed to determine the parameters for the maximum exergy efficiency using MATLAB optimization toolbox. Geometric parameters (collector surface area, dimensions, and pipe diameter), optical parameters (transmittance absorptance product), ambient temperature, solar irradiation and operating parameters (mass flow rate, fluid temperature, and overall heat transfer (loss) coefficient) are accounted for in the optimization scheme. The exergy efficiency at optimum condition is found to be 3.72%. The results are validated using experimental data and found to be in good agreement. The analysis is further extended to the influence of various operating parameters on the exergetic efficiency. It is observed that optical and thermal exergy losses contribute almost 20%, whereas approximately 77% exergy destruction is contributed by the thermal energy conversion. Exergy destruction due to pressure drop is found negligible. The result of this analysis can be used for designing and optimization of domestic heat pump system and hot water application.

DOI： 10.3390/app8030391

Language：Others   Publishing type：Research paper (scientific journal)  

Air conditioning approach using two separate units for latent heat and sensible heat removal opens up opportunities and challenges for improved efficiency. In such systems, the dehumidification device removes moisture from the air stream usually without condensation whilst the remaining sensible load is handled by a conventional mechanical vapour compression (MVC) machine. This article investigates the thermodynamic feasibility of such hybrid dehumidifier + MVC systems as potential replacements for the conventional MVC devices. We shed some light on the minimum efficacy requirement in terms of COP or simply the breakeven COP for the coupled dehumidification system. Thermodynamic investigation has been conducted using classical Carnot, endoreversible technique and the experimental approaches. The breakeven COPs for a dehumidifier + MVC system where the latter using HFC-R14a, HFC-R32 and HFO-R1234yf as refrigerants have been investigated at assorted outdoor air ratios. Performance enhancement in terms of COP and the cooling capacity at elevated temperatures for sensible cooling are accounted for. It is observed that the breakeven COP for the dehumidification system ranges from 9 to 17 (Carnot approach) and 4.3 to 6.8 (Ideal cycle) in order to be realistically competitive with the current efficiency offered by a MVC system for the both dehumidification and sensible cooling. The life cycle cost (LCC) analysis is further performed to assess the fresh air-handling systems using a conventional MVC system and a dehumidifier + MVC system. The unprecedented improvement in the performance of the MVC systems further raises the ceiling for the breakeven COP of the dehumidification systems.

DOI： 10.1016/j.apenergy.2018.01.024

Language：Others   Publishing type：Research paper (scientific journal)  

Adsorption heat exchanger comprises of the adsorbent granules/particles packed in between heat exchanging surfaces. The refrigerant vapor flow as well as heat transfer occurs through the adsorbent column. A 2-dimensional transient CFD study is employed to simulate the adsorption dynamics of ethanol vapor on loosely packed activated carbon. The adsorbent chosen for this study is activated carbon and the refrigerant is ethanol. In this paper, the efficacy of the refrigerant vapor transport through the porous adsorbent bed is studied in terms of flow resistance and thermal diffusion along with the mass diffusion through adsorbent particles. Three heat exchanging domains with same area but different aspect ratios (fin height to fin pitch ratio) along with two particle sizes are evaluated. The dynamic uptake predicted by this CFD study shows strong dependency on flow resistance of porous media for smaller particle size whereas a weak dependency on thermal and intra-particle mass diffusion is observed for larger particles. Furthermore, a comparison on the adsorption dynamics predicted by the present CFD study and the lumped kinetics model is carried out to determine the validity of the lumped model with respect to the adsorber geometry and particle size.

DOI： 10.1016/j.applthermaleng.2018.01.015

Language：Others   Publishing type：Research paper (scientific journal)  

This is the Issue No. 3 for Evergreen-Joint Journal of Novel Carbon Resource Sciences & Green Asia Strategy, in 2018. The present edition contains four articles diversified with review paper, catalyst performance, wind turbine performance and simulation of microwave propagation. We acknowledge contributions by the authors, reviewers, editorial team and the management team for the successful publication of this issue.

DOI： 10.5109/1936951

Language：Others   Publishing type：Research paper (scientific journal)  

The performance of a solar hot water system is assessed for heat pump and domestic heating applications. Thermodynamic analysis on a serpentine-type thermosyphon flat-plate solar heater is conducted using the Second Law of thermodynamics. Exergetic optimization is first performed to determine the parameters for the maximum exergy efficiency using MATLAB optimization toolbox. Geometric parameters (collector surface area, dimensions, and pipe diameter), optical parameters (transmittance absorptance product), ambient temperature, solar irradiation and operating parameters (mass flow rate, fluid temperature, and overall heat transfer (loss) coefficient) are accounted for in the optimization scheme. The exergy efficiency at optimum condition is found to be 3.72&#37;. The results are validated using experimental data and found to be in good agreement. The analysis is further extended to the influence of various operating parameters on the exergetic efficiency. It is observed that optical and thermal exergy losses contribute almost 20&#37;, whereas approximately 77&#37; exergy destruction is contributed by the thermal energy conversion. Exergy destruction due to pressure drop is found negligible. The result of this analysis can be used for designing and optimization of domestic heat pump system and hot water application.

DOI： 10.3390/app8030391

Language：English   Publishing type：Research paper (scientific journal)  

Air conditioning approach using two separate units for latent heat and sensible heat removal opens up opportunities and challenges for improved efficiency. In such systems, the dehumidification device removes moisture from the air stream usually without condensation whilst the remaining sensible load is handled by a conventional mechanical vapour compression (MVC) machine. This article investigates the thermodynamic feasibility of such hybrid dehumidifier + MVC systems as potential replacements for the conventional MVC devices. We shed some light on the minimum efficacy requirement in terms of COP or simply the breakeven COP for the coupled dehumidification system. Thermodynamic investigation has been conducted using classical Carnot, endoreversible technique and the experimental approaches. The breakeven COPs for a dehumidifier + MVC system where the latter using HFC-R14a, HFC-R32 and HFO-R1234yf as refrigerants have been investigated at assorted outdoor air ratios. Performance enhancement in terms of COP and the cooling capacity at elevated temperatures for sensible cooling are accounted for. It is observed that the breakeven COP for the dehumidification system ranges from 9 to 17 (Carnot approach) and 4.3 to 6.8 (Ideal cycle) in order to be realistically competitive with the current efficiency offered by a MVC system for the both dehumidification and sensible cooling. The life cycle cost (LCC) analysis is further performed to assess the fresh air-handling systems using a conventional MVC system and a dehumidifier + MVC system. The unprecedented improvement in the performance of the MVC systems further raises the ceiling for the breakeven COP of the dehumidification systems.

DOI： 10.1016/j.apenergy.2018.01.024

Language：English   Publishing type：Research paper (scientific journal)  

Adsorption heat exchanger comprises of the adsorbent granules/particles packed in between heat exchanging surfaces. The refrigerant vapor flow as well as heat transfer occurs through the adsorbent column. A 2-dimensional transient CFD study is employed to simulate the adsorption dynamics of ethanol vapor on loosely packed activated carbon. The adsorbent chosen for this study is activated carbon and the refrigerant is ethanol. In this paper, the efficacy of the refrigerant vapor transport through the porous adsorbent bed is studied in terms of flow resistance and thermal diffusion along with the mass diffusion through adsorbent particles. Three heat exchanging domains with same area but different aspect ratios (fin height to fin pitch ratio) along with two particle sizes are evaluated. The dynamic uptake predicted by this CFD study shows strong dependency on flow resistance of porous media for smaller particle size whereas a weak dependency on thermal and intra-particle mass diffusion is observed for larger particles. Furthermore, a comparison on the adsorption dynamics predicted by the present CFD study and the lumped kinetics model is carried out to determine the validity of the lumped model with respect to the adsorber geometry and particle size.

DOI： 10.1016/j.applthermaleng.2018.01.015

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1080/01457632.2018.1450325

Language：Others   Publishing type：Research paper (scientific journal)  

This article discusses a direct approach for assessing irregularly shaped pore distribution of porous materials using Atomic Force Microscopy (AFM). Using the tapping mode, AFM is employed to obtain the surface topographic information of the porous materials commonly used in adsorption applications. Three different types of silica gels, commercially used silica–alumina and acetaminophen samples are investigated using an image processing technique to capture the pore size-related information. Macro and mesopores in a specified region are visualized then quantified and counted using 2-D Fast Fourier Transformation (2D FFT) technique. The results obtained by the AFM technique are then compared with the BET surface area and pore size distribution (NLDFT) extracted from the N₂ adsorption isotherms.

DOI： 10.1016/j.ijrefrig.2018.08.017

Language：Others   Publishing type：Research paper (scientific journal)  

The performance of an adsorption system using Maxsorb III + ethanol pair is investigated for practical heat pump applications. An adsorption system using a single bed with a single evaporator/condenser is employed and the performance of the system is assessed for various regeneration temperatures (80 °C, 70 °C and 60 °C). The impact of the adsorption time on the performance of the selected pair is further evaluated. The potential application of the present adsorbent + adsorbate pair is the automobile air-conditioning system where the exhaust waste heat will be recovered to operate the adsorption system. Thus, antifreeze fluid is employed as the heat transfer medium for the adsorber and the evaporator/condenser heat exchanger. A mathematical model is developed to estimate the uptake amount from the experimental data. The sensible heat change (thermal mass), the superheating of the refrigerant in the adsorber, the adsorber heat leak and the heat rejection to the heat transfer medium are accounted for. The uptake amount is further verified using the classical p–T–q diagram. For operation using 30 °C adsorber coolant inlet and 15 °C chilled water inlet, the cooling capacity of the present system ranges from 15 to 35 W for the adsorption times of 600 s and 300 s, respectively. It is observed that the regeneration temperature significantly influences the net uptake of the system. The maximum net uptake is recorded to be about 0.995 kg/kg for the regeneration temperature of 80 °C. The system is further assessed using the ratio of the cooling capacity to the adsorption heat.

DOI： 10.1016/j.ijrefrig.2018.06.009

Language：English   Publishing type：Research paper (scientific journal)  

In this study, five error evaluation functions are used to calculate the error deviation between the experimental data and the predicted data for Maxsorb III/ethanol and RD silica gel/water pairs when the isotherm data fitted with six isotherm models. An error analysis based on the sum of normalized error (SNE) is performed to observe the effect of different error evaluation functions for the determination of isotherm parameters. On the basis of error values, Tòth isotherm provides less error compared to other models for both pairs. Error analysis using SNE advocates that HYBRID error evaluation function is suitable for D-A, Freundlich, and Hill models for both pairs whereas ARED error evaluation function is appropriate for Tòth and Langmuir models for Maxsorb III/ethanol pairs. However, RMSD for Redlich-Peterson and SSE for Tòth are appropriate for Maxsorb III/ethanol and silica gel/water pairs, respectively. Seven statistical tools are employed to predict the best isotherm model for the studied pairs. It is found that, except F-test, all other functions provide agreeable results for the better fitting of Tòth model for Maxsorb III/ethanol pair. More or less, similar findings are observed for the RD silica gel/water pair. Moreover, seven information criteria (IC’s) are also performed in order to find the optimum isotherm model. On the basis of IC’s, Tòth model provides less information loss compared to other models for the studied pairs.

DOI： 10.5109/2174852

Language：English   Publishing type：Research paper (scientific journal)  

Microporous adsorbents have been extensively employed in various sorption cycles. The specific heat capacity of such porous materials is an important parameter in adsorption simulation and system design. This article discusses the experimental evaluation of the specific heat capacities of several carbon-based adsorbents for cooling applications. The studied adsorbents include (i) parent Maxsorb III with different particle sizes, (ii) surface treated Maxsorb III (H₂ and KOH-H₂) (iii) recently developed spherical activated carbon (KOH treated phenol resin, KOH6-PR) and (iv) expanded graphite. The specific heat capacity of these materials is measured at temperatures ranging from 30 °C to 150 °C using a heat flux type differential scanning calorimeter (DSC). Within the experimental conditions, no phase transition or thermal anomaly is detected for all the adsorbents. Surface treated adsorbent exhibits higher specific heat capacities whilst KOH treated phenol resin (KOH6-PR) has the lowest value among the studied adsorbents. High specific heat capacities in the surface treated Maxsorb III might be attributed to the effect of surface treatment and the presence of surface functional group. The model given by Perry and Green is employed to fit the experimental data. These experimental data together with the fitted parameters are essential in the design and simulation of adsorption heat pump systems.

DOI： 10.1016/j.applthermaleng.2017.09.057

Language：English   Publishing type：Research paper (scientific journal)  

Refrigeration system of supermarket applications significantly contributes to direct and indirect global warming. The aim of this paper is to present a methodology of assessing such systems in terms of refrigerants, machinery and operational protocol to minimize the total equivalent warming impact (TEWI). Another perspective is painted for the refrigeration industry to ameliorate environmental impact. Air-cooled refrigeration system is analyzed for low temperature (LT) evaporation at −20 °C and medium temperature one (MT) at 0 °C with condensation at 40 °C. The effects of suction superheat and subcooling have also been accounted for. Various refrigerants such as HFC 134a, HFC blend 507A and their combinations are considered as working fluids for catering to a LT load of 50 kW and MT load of 250 kW. It is observed that HFC 134a for LT and MT gives the best combination. In addition, the impacts of COP on the TEWI for transcritical CO₂ systems were also estimated. Based on our results, HFC blend 507A refrigerants have the highest TEWI along with the maximum economic loss. Transcritical CO₂ refrigeration system with conceivably higher COP in the operating conditions are found to be the best from the TEWI perspectives with minimum economic loss due to refrigerant leakage because of its abundance availability.

DOI： 10.1016/j.ijhydene.2017.07.035

Language：Others   Publishing type：Research paper (scientific journal)  

Refrigeration system of supermarket applications significantly contributes to direct and indirect global warming. The aim of this paper is to present a methodology of assessing such systems in terms of refrigerants, machinery and operational protocol to minimize the total equivalent warming impact (TEWI). Another perspective is painted for the refrigeration industry to ameliorate environmental impact. Air-cooled refrigeration system is analyzed for low temperature (LT) evaporation at −20 °C and medium temperature one (MT) at 0 °C with condensation at 40 °C. The effects of suction superheat and subcooling have also been accounted for. Various refrigerants such as HFC 134a, HFC blend 507A and their combinations are considered as working fluids for catering to a LT load of 50 kW and MT load of 250 kW. It is observed that HFC 134a for LT and MT gives the best combination. In addition, the impacts of COP on the TEWI for transcritical CO systems were also estimated. Based on our results, HFC blend 507A refrigerants have the highest TEWI along with the maximum economic loss. Transcritical CO refrigeration system with conceivably higher COP in the operating conditions are found to be the best from the TEWI perspectives with minimum economic loss due to refrigerant leakage because of its abundance availability. 2 2

DOI： 10.1016/j.ijhydene.2017.07.035

Language：English   Publishing type：Research paper (scientific journal)  

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.5109/1936948

Language：English   Publishing type：Research paper (scientific journal)  

In this study, two hygroscopic materials, inorganic lithium chloride (LiCl) and organic triethylene glycol (TEG) were separately added to poly(vinyl alcohol) (PVA) to form blend membranes for air dehumidification. Water vapor permeation, dehumidification performance and long-term durability of the membranes were studied systematically. Membrane hydrophilicity and water vapor sorbability increased significantly with higher the hygroscopic material contents. Water vapor permeance of the membranes increased with both added hygroscopic material and absorbed water. Water permeation energy varied from positive to negative with higher hygroscopic content. This observation is attributed to a lower diffusion energy and a relatively constant sorption energy when hygroscopic content increases. Comparatively, PVA/TEG has less corrosive problems and is more environmentally friendly than PVA/LiCl. A membrane with PVA/TEG is observed to be highly durable and is suitable for dehumidification applications.

DOI： 10.1002/app.44765

Language：Others   Publishing type：Research paper (scientific journal)  

In this study, two hygroscopic materials, inorganic lithium chloride (LiCl) and organic triethylene glycol (TEG) were separately added to poly(vinyl alcohol) (PVA) to form blend membranes for air dehumidification. Water vapor permeation, dehumidification performance and long-term durability of the membranes were studied systematically. Membrane hydrophilicity and water vapor sorbability increased significantly with higher the hygroscopic material contents. Water vapor permeance of the membranes increased with both added hygroscopic material and absorbed water. Water permeation energy varied from positive to negative with higher hygroscopic content. This observation is attributed to a lower diffusion energy and a relatively constant sorption energy when hygroscopic content increases. Comparatively, PVA/TEG has less corrosive problems and is more environmentally friendly than PVA/LiCl. A membrane with PVA/TEG is observed to be highly durable and is suitable for dehumidification applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44765.

DOI： 10.1002/app.44765

Language：English   Publishing type：Research paper (scientific journal)  

Equilibrium adsorption uptake and kinetics of ethanol onto highly porous activated carbons (ACs) derived from two types of biomass namely waste palm trunk (WPT) and mangrove (M) have been experimentally measured at adsorption temperatures ranging from 30 to 70 °C for various evaporation pressures. A magnetic suspension adsorption measurement unit has been used for the experimental measurements. Four well-known adsorption isotherm models have been employed to fit the experimental data whilst two classical adsorption kinetics models i.e. Linear driving force (LDF) model and Fickian diffusion (FD) model are used to predict the experimental kinetics data. Among the four isotherm models Dubinin Astakhov (D-A), and Tóth equations agree well with the experimental uptake data for both ACs. The diffusion time constants are calculated at each adsorption temperature for WPT-AC/ethanol and M-AC/ethanol pairs. Moreover, activation energy and pre-exponential constant have been determined from the Arrhenius equation.

DOI： 10.1016/j.applthermaleng.2017.04.099

Language：English   Publishing type：Research paper (scientific journal)  

A solid desiccant dehumidifier equipped with adsorbent coated heat exchangers has been developed and investigated experimentally. The main component of the solid desiccant dehumidifier included two heat exchangers that were coated with silica gel regular density (RD) type powder in order to increase water adsorption uptake by improving its heat transfer. A series of experiment were conducted to evaluate two key performance indices, namely, moisture removal capacity and thermal performance, under various operating conditions. Results revealed that the reduction of dehumidification process time by 50% can lead to significant improvement of the mean humidity ratio at outlet up to 9.3 g/kg. The maximum moisture removal was found to decrease from 14.8 to 13.2 g/kg with higher airflow rates arising from the reduced residence time of the process air. It was further observed that the water moisture removal was highly affected by inlet humidity ratio. In addition, marked improvement in thermal performance can be achieved by a lowered hot water regeneration temperature.

DOI： 10.1080/23744731.2016.1218234

Language：English   Publishing type：Research paper (scientific journal)  

Biomasses are renewable resources and suitable precursors for synthesis of activated carbons (ACs). Two biomass sources: (i) Waste Palm Trunk (WPT) and (ii) Mangrove (M) are employed to synthesis activated carbons with huge surface area by chemical activation with potassium hydroxide (KOH). Thermophysical characteristics of the derived activated carbons namely thermal conductivity, particle size distribution, pore size distribution, surface area and pore volume are assessed. The total surface area of WPT-derived AC and mangrove-derived AC are found to be as high as 2927 m² g⁻¹ and 2924 m² g⁻¹, respectively. The adsorption capacities of the synthesized biomass-derived ACs for ethanol are evaluated for assorted temperature and pressure conditions. It is observed that WPT-AC shows an ethanol uptake of 1.90 kg kg⁻¹ whilst the M-AC can adsorb up to 1.65 kg kg⁻¹. The isosteric heat of adsorption associated with the present adsorbents/adsorbate (ACs/ethanol) calculated at different coverages showed only marginal difference. For a typical operating condition of adsorption heat pump, both biomass derived ACs showed similar net ethanol uptake which is significantly higher than the net uptake of commercially prevalent Maxsorb III AC.

DOI： 10.1016/j.ijheatmasstransfer.2017.02.081

Language：English   Publishing type：Research paper (scientific journal)  

Multi-bed adsorption cycle with the internal heat recovery between the condenser and the evaporator is investigated for desalination application. A numerical model is developed for a 4-bed adsorption cycle implemented with the master-and-slave configuration and the aforementioned internal heat recovery scheme. The present model captures the reversed adsorption/desorption phenomena frequently associated with the unmatched switching periods. Mesoporous silica gel and water vapor emanated from the evaporation of the seawater are employed as the adsorbent and adsorbate pair. The experimental data and investigation for such configurations are reported for the first time at heat source temperatures from 50 °C to 70 °C. The numerical model is validated rigorously and the parametric study is conducted for the performance of the cycle at assorted operation conditions such as hot and cooling water inlet temperatures and the cycle times. The specific daily water production (SDWP) of the present cycle is found to be about 10 m³/day per tonne of silica gel for the heat source temperature at 70 °C. Performance comparison is conducted for various types of adsorption desalination cycles. It is observed that the AD cycle with the current configuration provides superior performance whilst is operational at unprecedentedly low heat source temperature as low as 50 °C.

DOI： 10.1016/j.desal.2016.09.027

Language：English   Publishing type：Research paper (scientific journal)  

This paper presents an in-depth numerical and thermodynamic study of a two-stage, 2-bed silica gel/water adsorption system for simultaneous generation of cooling power and potable water. The system is air cooled where the ambient temperature remains constant at 36 °C. The first part of this paper investigates the effect of cycle time, chilled water inlet and heat source temperature on system performance viz. specific cooling capacity (SCC), specific daily water production (SDWP) and coefficient of performance (COP). A significant outcome of this study is to show that decrease in heat source temperature not only reduces the specific throughput but also increases the optimum cycle time, whereas COP is relatively insensitive to such alterations. The second part of this paper discusses the estimation of the minimum desorption temperature from the simulated system throughput results as well as from fundamental thermodynamic analysis of a two-stage adsorption cycle. This thermodynamic analysis provides a theoretical limit for minimum desorption temperature and optimal inter-stage pressure for a two-stage adsorption cycle.

DOI： 10.1016/j.apenergy.2017.08.198

Language：English   Publishing type：Research paper (scientific journal)  

Adsorption systems can utilize low grade waste heat (temperature <100°C) or energy from renewable sources like solar for cogeneration i.e. cooling and desalination. The throughput and performance of such systems are sensitive to the available temperature difference between heat source and sink. This paper presents a modelling study of two-stage 2-bed air cooled silica gel + water adsorption system wherein the effect of heat source temperature variation in the range of 65-85°C on system performance parameters viz. SCC, SDWP and COP are investigated for the first time. It is shown that the optimum half cycle time for SCC and SDWP increases from 1800 s to 2700 s as the source temperature decreases from 85°C to 65°C; thereby necessitating the use of adaptive cycle time control for maximum throughput. However, it is observed that the COP is relatively insensitive to such alterations.

DOI： 10.1016/j.egypro.2017.03.575

Language：English   Publishing type：Research paper (scientific journal)  

This paper presents a transient numerical study of two-stage, air-cooled silica gel + water adsorption system producing cooling and potable water. The key aspect of the present study is an attempt to model the inter-stage pressure dynamics when two beds exchange mass in terms of vapors across the stages. This is an important improvement over prior models wherein the inter-stage pressure was assumed to be either constant or user input. Furthermore, the evaporator and condenser pressures are also allowed to vary in this study in contrast to the previous papers. The simulation results are compared with the experimental data for various cycle times and chilled water inlet temperatures in the range of 11.5–20.0 °C, while having the heat source temperature fixed at 85 °C and air temperature at 36 °C. Depending on the chilled water inlet temperature and cycle time, the SCC is found to be between 2 and 7 Rton/tonne of silica gel; SDWP ranges within 0.3–0.9 m³/day/tonne of silica gel and COP varies between 0.05 and 0.26.

DOI： 10.1016/j.applthermaleng.2016.12.011

Language：English   Publishing type：Research paper (scientific journal)  

The intrinsic nature of adsorption cycles calls for heat and mass recovery schemes to improve the performance of the system. Energy recovery schemes become highly crucial for adsorption chiller cum desalination plants due to the unavoidable, frequent switching between the heating and cooling phases of the adsorber beds. A comprehensive numerical model for the mass recovery scheme by pressure equalization is developed and the validation with the experimental data is reported. The present model is able to capture the transient pressure response by the adsorbers during the pressure equalization process. It is observed that the specific equalization time exists for optimum mass recovery otherwise the reverse phenomenon occurs tarnishing the positive effect of the mass recovery scheme. Both the experimental and simulation results show that optimum mass recovery time is about 15 to 20 s depending on the heating/cooling temperature sources. The specific daily water production (SDWP) improvement can be as high as 5% by the mass recovery scheme which requires no additional hardware and heat source.

DOI： 10.1016/j.egypro.2017.03.574

Language：English   Publishing type：Research paper (scientific journal)  

Consolidated composite adsorbents have gained much attention as next generation adsorbents in adsorption heat pump (AHP) applications due to some of their salient features such as improved uptake to volume ratio and high thermal conductivity. Synthetic polymers, which are generally used as binders for the composite adsorbents impose negative impact on adsorption capacity resulting from poor affinity for the refrigerant and pore blockage. To address these issues, a polymerized ionic liquid (IL) was explored as a potential binder in making consolidated activated carbon composite. Polymerized IL [VBTMA][Ala] (vinylbenzyltrimethyl ammonium alanate) was synthesized and characterized. The composite adsorbent was prepared with a mass ratio of 90% Maxsorb III and 10% of Poly IL [VBTMA][Ala]. It is observed that surface area and pore volume of new composite were increased to more than 11% and 18%, respectively, compared to polyvinyl alcohol (PVA) as a binder. Sorption tests for ethanol uptake were performed using thermogravimetric technique at 303.15 K, 323.15 K and 343.15 K with various evaporator pressures. For a typical operating condition of AHP system, composite using polymerized IL as binder showed 22% higher net ethanol uptake than the net uptake of parent material Maxsorb III whereas a remarkably high 85% increase in thermal conductivity was observed. Thus, polymerized IL could be considered as strong candidate for making consolidated composite adsorbents in AHP applications.

DOI： 10.1016/j.cej.2017.06.031

Language：English   Publishing type：Research paper (scientific journal)  

The performance of a Mechanical Vapour Compression (MVC) chiller is experimentally investigated under operating conditions suitable for sensible cooling. With the emergence of the energy efficient dehumidification systems, it is possible to decouple the latent load from the MVC chillers which can be operated at higher chilled water temperatures for handling sensible cooling load. In this article, the performance of the chiller is evaluated at the elevated chilled water outlet temperatures (7–17 °C) at various coolant temperatures (28–32 °C) and flow rates (ΔT = 4 and 5 °C) for both full- and part-load conditions. Keeping the performance at the AHRI standard as the baseline condition, the efficacy of the chiller in terms of compression ratio, cooling capacity and COP at aforementioned conditions is quantified experimentally. It is observed that for each one-degree Celsius increase in the chilled water temperature, the COP of the chiller improves by about 3.5% whilst the cooling capacity improvement is about 4%. For operation at 17 °C chilled water outlet temperature, the improvements in COP and cooling capacity are between 37–40% and 40–45%, respectively, compared to the performance at the AHRI standards. The performance of the MVC chiller at the abovementioned operation conditions is mapped on the chiller performance characteristic chart.

DOI： 10.1016/j.applthermaleng.2017.05.091

Language：English  

DOI： 10.1144/M48.23

Language：Others   Publishing type：Research paper (scientific journal)  

A solid desiccant dehumidifier equipped with adsorbent coated heat exchangers has been developed and investigated experimentally. The main component of the solid desiccant dehumidifier included two heat exchangers that were coated with silica gel regular density (RD) type powder in order to increase water adsorption uptake by improving its heat transfer. A series of experiment were conducted to evaluate two key performance indices, namely, moisture removal capacity and thermal performance, under various operating conditions. Results revealed that the reduction of dehumidification process time by 50&#37; can lead to significant improvement of the mean humidity ratio at outlet up to 9.3 g/kg. The maximum moisture removal was found to decrease from 14.8 to 13.2 g/kg with higher airflow rates arising from the reduced residence time of the process air. It was further observed that the water moisture removal was highly affected by inlet humidity ratio. In addition, marked improvement in thermal performance can be achieved by a lowered hot water regeneration temperature.

DOI： 10.1080/23744731.2016.1218234

Language：Others   Publishing type：Research paper (scientific journal)  

Multi-bed adsorption cycle with the internal heat recovery between the condenser and the evaporator is investigated for desalination application. A numerical model is developed for a 4-bed adsorption cycle implemented with the master-and-slave configuration and the aforementioned internal heat recovery scheme. The present model captures the reversed adsorption/desorption phenomena frequently associated with the unmatched switching periods. Mesoporous silica gel and water vapor emanated from the evaporation of the seawater are employed as the adsorbent and adsorbate pair. The experimental data and investigation for such configurations are reported for the first time at heat source temperatures from 50 °C to 70 °C. The numerical model is validated rigorously and the parametric study is conducted for the performance of the cycle at assorted operation conditions such as hot and cooling water inlet temperatures and the cycle times. The specific daily water production (SDWP) of the present cycle is found to be about 10 m /day per tonne of silica gel for the heat source temperature at 70 °C. Performance comparison is conducted for various types of adsorption desalination cycles. It is observed that the AD cycle with the current configuration provides superior performance whilst is operational at unprecedentedly low heat source temperature as low as 50 °C. 3

DOI： 10.1016/j.desal.2016.09.027

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Extreme flash evaporation occurs when superheated liquid is sprayed into a low pressure zone. This method has high potential to improve the performance of thermally-driven desalination plants. To enable a more in-depth understanding on flash evaporation of a superheated feed water spray, a theoretical model has been developed with key considerations given to droplet motion and droplet size distribution. The model has been validated against 14 experimental data sets from literature sources to within 12% discrepancy. This model is capable of accurately predicting the water productivity and thermal efficiency of existing spray evaporator under specific operating conditions. Employing this model, the effect of several design parameters on system performance was investigated. Key results revealed that smaller droplet enabled faster evaporation process while higher initial droplet velocity promoted water productivity. Thermal utilization marginally changes with the degree of superheat, which renders a quick design calculation of the brine temperature without the need for iterations.

DOI： 10.1016/j.desal.2016.08.017

Language：Others   Publishing type：Research paper (scientific journal)  

Extreme flash evaporation occurs when superheated liquid is sprayed into a low pressure zone. This method has high potential to improve the performance of thermally-driven desalination plants. To enable a more in-depth understanding on flash evaporation of a superheated feed water spray, a theoretical model has been developed with key considerations given to droplet motion and droplet size distribution. The model has been validated against 14 experimental data sets from literature sources to within 12&#37; discrepancy. This model is capable of accurately predicting the water productivity and thermal efficiency of existing spray evaporator under specific operating conditions. Employing this model, the effect of several design parameters on system performance was investigated. Key results revealed that smaller droplet enabled faster evaporation process while higher initial droplet velocity promoted water productivity. Thermal utilization marginally changes with the degree of superheat, which renders a quick design calculation of the brine temperature without the need for iterations.

DOI： 10.1016/j.desal.2016.08.017

Language：English   Publishing type：Research paper (scientific journal)  

Environment-friendly adsorption (AD) cycles have gained much attention in cooling industry and its applicability has been extended to desalination recently. AD cycles are operational by low-temperature heat sources such as exhaust gas from processes or renewable energy with temperatures ranging from 55 °C to 85 °C. The cycle is capable of producing two useful effects, namely cooling power and high-grade potable water, simultaneously. This article discusses a low temperature, waste heat-powered adsorption (AD) cycle that produces cooling power at two temperature-levels for both dehumidification and sensible cooling while providing high-grade potable water. The cycle exploits faster kinetics for desorption process with one adsorber bed under regeneration mode while full utilization of the uptake capacity by adsorbent material is achieved employing two-stage adsorption via low-pressure and high-pressure evaporators. Type A⁺⁺ silica gel with surface area of 863.6 m²/g and pore volume of 0.446 cm³/g is employed as adsorbent material. A comprehensive numerical model for such AD cycle is developed and the performance results are presented using assorted hot water and cooling water inlet temperatures for various cycle time arrangements. The cycle is analyzed in terms of key performance indicators i.e.; the specific cooling power (SCP), the coefficient of performance (COP) for both evaporators and the overall system, the specific daily water production (SDWP) and the performance ratio (PR). Further insights into the cycle performance are scrutinized using a Dühring diagram to depict the thermodynamic states of the processes as well as the vapor uptake behavior of adsorbent. In the proposed cycle, the adsorbent materials undergo near saturation conditions due to the pressurization effect from the high pressure evaporator while faster kinetics for desorption process is exploited, subsequently providing higher system COP, notably up to 0.82 at longer cycle time while the COPs for low-pressure and high-pressure evaporators are recorded to be 0.33 and 0.51, respectively.

DOI： 10.1016/j.ijheatmasstransfer.2016.05.127

Language：Others   Publishing type：Research paper (scientific journal)  

Understanding the dynamic behavior of the dew point evaporative cooler is crucial in achieving efficient cooling for real applications. This paper details the development of a transient model for a counter-flow dew point evaporative cooling system. The transient model approaching steady conditions agreed well with the steady state model. Additionally, it is able to accurately predict the experimental data within 4.3&#37; discrepancy. The transient responses of the cooling system were investigated under different inlet air conditions. Temporal temperature and humidity profiles were analyzed for different transient and step responses. The key findings from this study include: (1) the response trend and settling time is markedly dependent on the inlet air temperature, humidity and velocity; (2) the settling time of the transient response ranges from 50 s to 300 s when the system operates under different inlet conditions; and (3) the average transient wet bulb effectiveness (1.00–1.06) of the system is observed to be higher than the steady state wet bulb effectiveness (1.01) for our range of study.

DOI： 10.1016/j.energy.2016.07.036

Language：Others   Publishing type：Research paper (scientific journal)  

Environment-friendly adsorption (AD) cycles have gained much attention in cooling industry and its applicability has been extended to desalination recently. AD cycles are operational by low-temperature heat sources such as exhaust gas from processes or renewable energy with temperatures ranging from 55 °C to 85 °C. The cycle is capable of producing two useful effects, namely cooling power and high-grade potable water, simultaneously. This article discusses a low temperature, waste heat-powered adsorption (AD) cycle that produces cooling power at two temperature-levels for both dehumidification and sensible cooling while providing high-grade potable water. The cycle exploits faster kinetics for desorption process with one adsorber bed under regeneration mode while full utilization of the uptake capacity by adsorbent material is achieved employing two-stage adsorption via low-pressure and high-pressure evaporators. Type A silica gel with surface area of 863.6 m /g and pore volume of 0.446 cm /g is employed as adsorbent material. A comprehensive numerical model for such AD cycle is developed and the performance results are presented using assorted hot water and cooling water inlet temperatures for various cycle time arrangements. The cycle is analyzed in terms of key performance indicators i.e.; the specific cooling power (SCP), the coefficient of performance (COP) for both evaporators and the overall system, the specific daily water production (SDWP) and the performance ratio (PR). Further insights into the cycle performance are scrutinized using a Dühring diagram to depict the thermodynamic states of the processes as well as the vapor uptake behavior of adsorbent. In the proposed cycle, the adsorbent materials undergo near saturation conditions due to the pressurization effect from the high pressure evaporator while faster kinetics for desorption process is exploited, subsequently providing higher system COP, notably up to 0.82 at longer cycle time while the COPs for low-pressure and high-pressure evaporators are recorded to be 0.33 and 0.51, respectively. ++ 2 3

DOI： 10.1016/j.ijheatmasstransfer.2016.05.127

Language：English   Publishing type：Research paper (scientific journal)  

Understanding the dynamic behavior of the dew point evaporative cooler is crucial in achieving efficient cooling for real applications. This paper details the development of a transient model for a counter-flow dew point evaporative cooling system. The transient model approaching steady conditions agreed well with the steady state model. Additionally, it is able to accurately predict the experimental data within 4.3% discrepancy. The transient responses of the cooling system were investigated under different inlet air conditions. Temporal temperature and humidity profiles were analyzed for different transient and step responses. The key findings from this study include: (1) the response trend and settling time is markedly dependent on the inlet air temperature, humidity and velocity; (2) the settling time of the transient response ranges from 50 s to 300 s when the system operates under different inlet conditions; and (3) the average transient wet bulb effectiveness (1.00–1.06) of the system is observed to be higher than the steady state wet bulb effectiveness (1.01) for our range of study.

DOI： 10.1016/j.energy.2016.07.036

Language：English   Publishing type：Research paper (scientific journal)  

In this paper, a hybrid desalination system consisting of vacuum membrane distillation (VMD) and adsorption desalination (AD) units, designated as VMD-AD cycle, is proposed. The synergetic integration of the VMD and AD is demonstrated where a useful effect of the AD cycle is channelled to boost the operation of the VMD process, namely the low vacuum environment to maintain the high pressure gradient across the microporous hydrophobic membrane. A solar-assisted multi-stage VMD-AD hybrid desalination system with temperature modulating unit is first designed, and its performance is then examined with a mathematical model of each component in the system and compared with the VMD-only system with temperature modulating and heat recovery units. The total water production and water recovery ratio of a solar-assisted 24-stage VMD-AD hybrid system are found to be about 21% and 23% higher, respectively, as compared to the VMD-only system. For the solar-assisted 24-stage VMD-AD desalination system having 150 m ² of evacuated-tube collectors and 10 m ³ seawater storage tanks, both annual collector efficiency and solar fraction are close to 60%.

DOI： 10.1016/j.watres.2016.05.002

Language：Others   Publishing type：Research paper (scientific journal)  

A gas turbine system is extensively investigated for micro/mini-Combine Heat and Power (CHP) applications. The prime mover in the system, i.e., the microturbine, has a nameplate electrical capacity of 65 kW while the coupled Waste Heat Recovery System (WHRS) produces 112 kW. Experiments were conducted for assorted power demands spanning from part-load to full-load operations. A simple thermodynamic model together with a nonlinear optimization scheme is applied to determine the properties at various state points that are not provided by the manufacturer. The second law analysis and the Energy Utilization Factor (EUF) technique are employed to assess the efficacy of the system. The actual chemical compositions of the CNG, the exhaust gas, the moist air and subsequently the amount of water condensation at the dead state are accounted for in the analysis. Here, the excess air usage in the combustion process at various loads is quantitatively reported for the first time. The results show that the combustor is responsible for almost 70&#37; of the total exergy destruction followed by the recuperator, the compressor, and the turbine in the descending order. The first law efficiency of the system varies from 15.7&#37; at 25&#37; load to 28.95&#37; for full load operation. The itemized exergetic efficiency for all the processes is evaluated while the second law efficiency of the overall system is found to be around 30.4&#37; at full load condition. The presented results pinpoint the bottleneck of the microturbine operation, particularly at part-load conditions and are crucial in designing and performance mapping of an optimized cogeneration system.

DOI： 10.1016/j.apenergy.2016.06.106

Language：Others   Publishing type：Research paper (scientific journal)  

In an effort to accurately plan for investment on energy production and distribution, this paper proposes a long-term electricity consumption forecasting model for buildings' cooling by employing a high energy conservative scenario. The key aspect of the high energy conservative scenario is to adopt an innovative adsorbent-based dehumidifier and an indirect evaporative cooling (AD-IEC) technology as opposed to conventional mechanical vapor compression system. Bottom-up equations were developed to identify the cooling load and electricity consumption of both residential and non-residential buildings for the period 2002-2013. Based on the time-series electricity consumption, a multiple linear regression model is developed to forecast electricity demand for the future period of 2014-2030. It is found that the electricity demands for cooling in the building sectors account for 31 ± 2&#37; of the total electricity consumption in Singapore, This study concluded that the high conservative scenario realizes the best potential of electricity saving of 21,096 GWh until 2030. Using a CO emission factor of 4.49 × 10 metric tons CO /kWh, the total carbon footprint saving from all power plants is estimated to be 9491,264 t of CO . This work evolves a new forecasting methodology to predict buildings' cooling energy consumption involving the use of novel cooling technologies. 2 2 2 -4

DOI： 10.1016/j.enbuild.2016.05.073

Language：Others   Publishing type：Research paper (scientific journal)  

In this paper, a hybrid desalination system consisting of vacuum membrane distillation (VMD) and adsorption desalination (AD) units, designated as VMD-AD cycle, is proposed. The synergetic integration of the VMD and AD is demonstrated where a useful effect of the AD cycle is channelled to boost the operation of the VMD process, namely the low vacuum environment to maintain the high pressure gradient across the microporous hydrophobic membrane. A solar-assisted multi-stage VMD-AD hybrid desalination system with temperature modulating unit is first designed, and its performance is then examined with a mathematical model of each component in the system and compared with the VMD-only system with temperature modulating and heat recovery units. The total water production and water recovery ratio of a solar-assisted 24-stage VMD-AD hybrid system are found to be about 21&#37; and 23&#37; higher, respectively, as compared to the VMD-only system. For the solar-assisted 24-stage VMD-AD desalination system having 150 m of evacuated-tube collectors and 10 m seawater storage tanks, both annual collector efficiency and solar fraction are close to 60&#37;. 2 3

DOI： 10.1016/j.watres.2016.05.002

Language：English   Publishing type：Research paper (scientific journal)  

A gas turbine system is extensively investigated for micro/mini-Combine Heat and Power (CHP) applications. The prime mover in the system, i.e., the microturbine, has a nameplate electrical capacity of 65 kW while the coupled Waste Heat Recovery System (WHRS) produces 112 kW. Experiments were conducted for assorted power demands spanning from part-load to full-load operations. A simple thermodynamic model together with a nonlinear optimization scheme is applied to determine the properties at various state points that are not provided by the manufacturer. The second law analysis and the Energy Utilization Factor (EUF) technique are employed to assess the efficacy of the system. The actual chemical compositions of the CNG, the exhaust gas, the moist air and subsequently the amount of water condensation at the dead state are accounted for in the analysis. Here, the excess air usage in the combustion process at various loads is quantitatively reported for the first time. The results show that the combustor is responsible for almost 70% of the total exergy destruction followed by the recuperator, the compressor, and the turbine in the descending order. The first law efficiency of the system varies from 15.7% at 25% load to 28.95% for full load operation. The itemized exergetic efficiency for all the processes is evaluated while the second law efficiency of the overall system is found to be around 30.4% at full load condition. The presented results pinpoint the bottleneck of the microturbine operation, particularly at part-load conditions and are crucial in designing and performance mapping of an optimized cogeneration system.

DOI： 10.1016/j.apenergy.2016.06.106

Language：English   Publishing type：Research paper (scientific journal)  

In an effort to accurately plan for investment on energy production and distribution, this paper proposes a long-term electricity consumption forecasting model for buildings' cooling by employing a high energy conservative scenario. The key aspect of the high energy conservative scenario is to adopt an innovative adsorbent-based dehumidifier and an indirect evaporative cooling (AD-IEC) technology as opposed to conventional mechanical vapor compression system. Bottom-up equations were developed to identify the cooling load and electricity consumption of both residential and non-residential buildings for the period 2002-2013. Based on the time-series electricity consumption, a multiple linear regression model is developed to forecast electricity demand for the future period of 2014-2030. It is found that the electricity demands for cooling in the building sectors account for 31 ± 2% of the total electricity consumption in Singapore, This study concluded that the high conservative scenario realizes the best potential of electricity saving of 21,096 GWh until 2030. Using a CO₂ emission factor of 4.49 × 10^-4 metric tons CO₂/kWh, the total carbon footprint saving from all power plants is estimated to be 9491,264 t of CO₂. This work evolves a new forecasting methodology to predict buildings' cooling energy consumption involving the use of novel cooling technologies.

DOI： 10.1016/j.enbuild.2016.05.073

Language：English   Publishing type：Research paper (scientific journal)  

Water-Energy-Environment nexus is a crucial consideration when designing seawater desalination processes, particularly for the water-stressed countries where the annual water availability is less than 250 m³ per capita. Despite the thermodynamics limit for seawater desalination at normal conditions is about 0.78 to 1.09 kWh_elec/m³, the specific energy consumption of desalination of real plants is found to operate at several folds higher. Today’s technological advancement in membranes, namely the reverse osmosis processes, has set an energy consumption of around 3.5–5 kWh_elec/m³, while the conventional perception of thermally activated processes such as MSF and MED tends to be higher. Although the higher energetic specific consumption of MED or MSF processes appeared to be higher at 60–100 kWh_thermal/m³, their true electricity equivalent has been converted, hitherto, using the energetic analyses where the work potential of working steam of the processes cannot be captured adequately. Thermally activated processes, such as MED and MSF, form the bottoming cycle of a cogeneration plant where both electricity and desalination processes operate in tandem in a cascaded manner. Only the bled-steam at lower exergy is extracted for the desalination processes. In this presentation, we demonstrate that in a cogen plant with 30% bled-steam for MED processes, the exergy destruction ratio is found to be less than 7% of the total available exergy that emanated from the boilers. By the exergetic approach, the equivalent electricity consumption of an average 75 kWh_thermal/m³ would result in an electrical equivalent of less than 2.5 kWh_elec/m³. Also in this presentation, the authors will elaborate the latest developments in the use of hybridization concept where the MED and the AD cycles are thermodynamically integrated and enhancing the overall efficiency of desalination.

DOI： 10.1080/19443994.2015.1035499

Language：Others   Publishing type：Research paper (scientific journal)  

Water-Energy-Environment nexus is a crucial consideration when designing seawater desalination processes, particularly for the water-stressed countries where the annual water availability is less than 250 m per capita. Despite the thermodynamics limit for seawater desalination at normal conditions is about 0.78 to 1.09 kWh /m , the specific energy consumption of desalination of real plants is found to operate at several folds higher. Today’s technological advancement in membranes, namely the reverse osmosis processes, has set an energy consumption of around 3.5–5 kWh /m , while the conventional perception of thermally activated processes such as MSF and MED tends to be higher. Although the higher energetic specific consumption of MED or MSF processes appeared to be higher at 60–100 kWh /m , their true electricity equivalent has been converted, hitherto, using the energetic analyses where the work potential of working steam of the processes cannot be captured adequately. Thermally activated processes, such as MED and MSF, form the bottoming cycle of a cogeneration plant where both electricity and desalination processes operate in tandem in a cascaded manner. Only the bled-steam at lower exergy is extracted for the desalination processes. In this presentation, we demonstrate that in a cogen plant with 30&#37; bled-steam for MED processes, the exergy destruction ratio is found to be less than 7&#37; of the total available exergy that emanated from the boilers. By the exergetic approach, the equivalent electricity consumption of an average 75 kWh /m would result in an electrical equivalent of less than 2.5 kWh /m . Also in this presentation, the authors will elaborate the latest developments in the use of hybridization concept where the MED and the AD cycles are thermodynamically integrated and enhancing the overall efficiency of desalination. 3 3 3 3 3 3 elec elec thermal thermal elec

DOI： 10.1080/19443994.2015.1035499

Language：English   Publishing type：Research paper (scientific journal)  

Adsorption (AD) cycle is recently pioneered for cooling and desalination applications. For water treatment, the cycle can be used to treat highly concentrated feed water, ranging from seawater to ground water and to chemically-laden waste water. This paper presents a review of the recent development of AD cycle and its hybridization with known conventional cycles such as the MED and MSF. We begin by looking at the basic sorption theory for different adsorbent-adsorbate pairs, namely (i) silica gel-water, (ii) the zeolite-water, (iii) parent Maxsorb III/ethanol, (iv) KOH-H₂ surface treated Maxsorb III/ethanol, and (v) a metal organic framework (MOF) material namely, MIL-101Cr/ethanol. We also present the basic AD cycle for seawater desalination as well as its hybridization with known conventional thermally-driven cycles for efficiency improvement. We demonstrate the water production improvement by 2-3 folds by hybridization in a pilot comprising a 3-stage MED and AD plant and the top-brine temperature 50 °C.

DOI： 10.1016/j.applthermaleng.2015.09.113

Language：Others   Publishing type：Research paper (scientific journal)  

Adsorption (AD) cycle is recently pioneered for cooling and desalination applications. For water treatment, the cycle can be used to treat highly concentrated feed water, ranging from seawater to ground water and to chemically-laden waste water. This paper presents a review of the recent development of AD cycle and its hybridization with known conventional cycles such as the MED and MSF. We begin by looking at the basic sorption theory for different adsorbent-adsorbate pairs, namely (i) silica gel-water, (ii) the zeolite-water, (iii) parent Maxsorb III/ethanol, (iv) KOH-H surface treated Maxsorb III/ethanol, and (v) a metal organic framework (MOF) material namely, MIL-101Cr/ethanol. We also present the basic AD cycle for seawater desalination as well as its hybridization with known conventional thermally-driven cycles for efficiency improvement. We demonstrate the water production improvement by 2-3 folds by hybridization in a pilot comprising a 3-stage MED and AD plant and the top-brine temperature 50 °C. 2

DOI： 10.1016/j.applthermaleng.2015.09.113

Language：English   Publishing type：Research paper (scientific journal)  

Dew point evaporative cooling has great potential as a disruptive process for sensible cooling of air below its entering wet bulb temperature. This paper presents an improved mathematical model for a single-stage dew point evaporative cooler in a counter-flow configuration. Longitudinal heat conduction and mass diffusion of the air streams, channel plate and water film, as well as the temperature difference between the plate and water film, are accounted for in the model. Predictions of the product air temperature are validated using three sets of experimental data within a discrepancy of 4%. The cooler's heat and mass transfer process is analyzed in terms of its cooling capacity intensity, water evaporation intensity, and overall heat transfer coefficient along the channel. Parametric studies are conducted at different geometric and operating conditions. For the conditions evaluated, the study reveals that (1) the saturation point of the working air occurs at a fixed point regardless of the inlet air conditions, and it is mainly influenced by the working air ratio and channel height; (2) the intensity of the water evaporation approaches a minimum at 0.2 to 0.3 m from the entrance; (3) the wet channel can be separated into two zones, and the overall heat transfer coefficient is above 100 W/(m²·K) after the temperature of water film becomes higher than the working air temperature.

DOI： 10.1016/j.enconman.2015.11.059

Language：Others   Publishing type：Research paper (scientific journal)  

Dew point evaporative cooling has great potential as a disruptive process for sensible cooling of air below its entering wet bulb temperature. This paper presents an improved mathematical model for a single-stage dew point evaporative cooler in a counter-flow configuration. Longitudinal heat conduction and mass diffusion of the air streams, channel plate and water film, as well as the temperature difference between the plate and water film, are accounted for in the model. Predictions of the product air temperature are validated using three sets of experimental data within a discrepancy of 4&#37;. The cooler's heat and mass transfer process is analyzed in terms of its cooling capacity intensity, water evaporation intensity, and overall heat transfer coefficient along the channel. Parametric studies are conducted at different geometric and operating conditions. For the conditions evaluated, the study reveals that (1) the saturation point of the working air occurs at a fixed point regardless of the inlet air conditions, and it is mainly influenced by the working air ratio and channel height; (2) the intensity of the water evaporation approaches a minimum at 0.2 to 0.3 m from the entrance; (3) the wet channel can be separated into two zones, and the overall heat transfer coefficient is above 100 W/(m ·K) after the temperature of water film becomes higher than the working air temperature. 2

DOI： 10.1016/j.enconman.2015.11.059

Language：English   Publishing type：Research paper (scientific journal)  

We present a detailed study on the transient heat transfer phenomena of powdered-adsorbent mixed with an organic binder for adherence to the fins of a heat exchanger. The transient performance of such an adsorbent-heat exchanger configuration has significant application potential in the adsorption desalination plants and chillers but is seldom addressed in the literature. An experiment is designed to measure the heat transfer for several adsorption temperatures under a single vapor component environment. Analysis on the experimental data indicates that the adsorbent-adsorbate interactions contribute about 75% of the total thermal resistances throughout the uptake processes. It is found that the initial local adsorption heat transfer coefficients are significantly higher than the average values due primarily to the thermal mass effect of the adsorbent-adsorbate interaction layers. From these experiments, a correlation for the transient local adsorption heat transfer coefficients is presented at the sub-atmospheric pressures and assorted application temperatures.

DOI： 10.1016/j.applthermaleng.2015.09.057

Language：Others   Publishing type：Research paper (scientific journal)  

The performance of adsorption (AD) chillers or desalination cycles is dictated by the rates of heat and mass transfer of adsorbate in adsorbent-packed beds. Conventional granular-adsorbent, packed in fin-tube heat exchangers, suffered from poor heat transfer in heating (desorption) or cooling (adsorption) processes of the batch-operated cycles, with undesirable performance parameters such as higher footprint of plants, low coefficient of performance (COP) of AD cycles and higher capital cost of the machines. The motivation of present work is to mitigate the heat and mass "bottlenecks" of fin-tube heat exchangers by using a powdered-adsorbent cum binder coated onto the fin surfaces of exchangers. Suitable adsorbent-binder pairs have been identified for the silica gel adsorbent with pore surface areas up to 680 m²/g and pore diameters less than 6 nm. The parent silica gel remains largely unaffected despite being pulverized into fine particles of 100 μm, and yet maintaining its water uptake characteristics. The paper presents an experimental study on the selection and testing processes to achieve high efficacy of adsorbent-binder coated exchangers. The test results indicate 3.4-4.6 folds improvement in heat transfer rates over the conventional granular-packed method, resulting a faster rate of water uptake by 1.5-2 times on the suitable silica gel type.

DOI： 10.1016/j.ijheatmasstransfer.2015.08.097

Language：Others   Publishing type：Research paper (scientific journal)  

We present a detailed study on the transient heat transfer phenomena of powdered-adsorbent mixed with an organic binder for adherence to the fins of a heat exchanger. The transient performance of such an adsorbent-heat exchanger configuration has significant application potential in the adsorption desalination plants and chillers but is seldom addressed in the literature. An experiment is designed to measure the heat transfer for several adsorption temperatures under a single vapor component environment. Analysis on the experimental data indicates that the adsorbent-adsorbate interactions contribute about 75&#37; of the total thermal resistances throughout the uptake processes. It is found that the initial local adsorption heat transfer coefficients are significantly higher than the average values due primarily to the thermal mass effect of the adsorbent-adsorbate interaction layers. From these experiments, a correlation for the transient local adsorption heat transfer coefficients is presented at the sub-atmospheric pressures and assorted application temperatures.

DOI： 10.1016/j.applthermaleng.2015.09.057

Language：English   Publishing type：Research paper (scientific journal)  

The performance of adsorption (AD) chillers or desalination cycles is dictated by the rates of heat and mass transfer of adsorbate in adsorbent-packed beds. Conventional granular-adsorbent, packed in fin-tube heat exchangers, suffered from poor heat transfer in heating (desorption) or cooling (adsorption) processes of the batch-operated cycles, with undesirable performance parameters such as higher footprint of plants, low coefficient of performance (COP) of AD cycles and higher capital cost of the machines. The motivation of present work is to mitigate the heat and mass "bottlenecks" of fin-tube heat exchangers by using a powdered-adsorbent cum binder coated onto the fin surfaces of exchangers. Suitable adsorbent-binder pairs have been identified for the silica gel adsorbent with pore surface areas up to 680 m²/g and pore diameters less than 6 nm. The parent silica gel remains largely unaffected despite being pulverized into fine particles of 100 μm, and yet maintaining its water uptake characteristics. The paper presents an experimental study on the selection and testing processes to achieve high efficacy of adsorbent-binder coated exchangers. The test results indicate 3.4-4.6 folds improvement in heat transfer rates over the conventional granular-packed method, resulting a faster rate of water uptake by 1.5-2 times on the suitable silica gel type.

DOI： 10.1016/j.ijheatmasstransfer.2015.08.097

Language：English   Publishing type：Research paper (scientific journal)  

There has been a plethora of published literature on thermally-driven adsorption desalination (AD) cycles for seawater desalination due to their favorable environmentally friendly attributes, such as the ability to operate with low-temperature heat sources, from either the renewable or the exhaust gases, and having almost no major moving parts. We present an AD cycle for seawater desalination due to its unique ability to integrate higher water production yields with the existing desalination methods such as reverse osmosis (RO), multi-stage flashing (MSF) and multi-effect distillation (MED), etc. The hybrid cycles exploit the thermodynamic synergy between processes, leading to significant enhancement of the systems' performance ratio (PR). In this paper, we demonstrate experimentally the synergetic effect between the AD and MED cycles that results in quantum improvement in water production. The unique feature is in the internal latent heat recovery from the condenser unit of AD to the top-brine stage of MED, resulting in a combined, or simply termed as MEAD, cycle that requires no additional heat input other than the regeneration of an adsorbent. The batch-operated cycles are simple to implement and require low maintenance when compared with conventional desalination methods. Together, they offer a low energy and environmentally friendly desalination solution that addresses the major issues of the water-energy-environment nexus.

DOI： 10.1039/c5ew00217f

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

This article presents the development of an advanced adsorption desalination system with quantum performance improvement. The proposed multi-effect adsorption desalination (MEAD) cycle utilizes a single heat source i.e., low-temperature hot water (as low as 55°C). Passive heating of the feed water (no direct heating) is adopted using total internal heat recovery from the kinetic energy of desorbed vapor and water vapor uptake potential of the adsorbent. Thus, the evaporation in the MEAD cycle ensues at low temperatures ranging from 35°C to 7°C yet providing significantly high performance ratio. The energy from the regenerated vapor is recovered for multiple evaporation/condensation of saline water by a water-run-around circuit between the top brine temperature (TBT) effect and the AD condenser. The adsorbent material is the hydrophilic mesoporous silica gel with high pore surface area. Numerical simulation for such a cycle is developed based on experimentally verified model extending to multi-effect cycle. The system is investigated under several operation conditions such as cycle time allocation, heat source temperature and the number of intermediate effects. It is observed that most of the evaporating-condensing effects operate at low temperature i.e., below 35°C as opposed to conventional multi-effect distillation (MED) cycle. For a MEAD cycle with 7 intermediate effects, the specific water production rate, the performance ratio and the gain output ratio are found to be 1.0m³/htonne of silica gel, 6.3 and 5.1, respectively. Low scaling and fouling potentials being evaporation at low temperatures yet high recovery ratio makes the cycle suitable for effectively and efficiently handling highly concentrated feed water such as produced water, brine rejected from other desalination plants and zero liquid discharge (ZLD) system.

DOI： 10.1016/j.apenergy.2015.09.035

Language：English   Publishing type：Research paper (scientific journal)  

This paper describes the development of a solar-assisted multi-stage vacuum membrane distillation (SMVMD) system. The proposed system employs heat recovery unit (HRU) for the energy recovery from the permeate vapor to the feed seawater. Temperature modulating (TM) scheme is also implemented for the attenuation of temperature fluctuations of the feed seawater. A commercial shell-and-tube capillary membrane module consisting of an array of polypropylene hydrophobic fibers has been adopted for the system design and mathematical model development. The SMVMD system is studied for the different numbers of HRUs using a mathematical model. For a solar-assisted VMD system with 24-stage, the total water production of SMVMD system with 10 HRUs is found to be 3.37m³/day, which is about 34% higher as compared to the system with a single HRU. For a VMD system without solar-thermal unit, the overall specific thermal energy consumption (OSTEC) decreases by 20% with an increase in the number of HRUs from 1 to 10. For the different numbers of HRUs in the range of 1-10, the system OSTECs with solar-thermal system having 150m² of evacuated-tube collectors and 16m³ seawater storage tanks are 28%-36% lower compared to those without the solar thermal system.

DOI： 10.1016/j.desal.2015.04.003

Language：Others   Publishing type：Research paper (scientific journal)  

This paper describes the development of a solar-assisted multi-stage vacuum membrane distillation (SMVMD) system. The proposed system employs heat recovery unit (HRU) for the energy recovery from the permeate vapor to the feed seawater. Temperature modulating (TM) scheme is also implemented for the attenuation of temperature fluctuations of the feed seawater. A commercial shell-and-tube capillary membrane module consisting of an array of polypropylene hydrophobic fibers has been adopted for the system design and mathematical model development. The SMVMD system is studied for the different numbers of HRUs using a mathematical model. For a solar-assisted VMD system with 24-stage, the total water production of SMVMD system with 10 HRUs is found to be 3.37m³/day, which is about 34&#37; higher as compared to the system with a single HRU. For a VMD system without solar-thermal unit, the overall specific thermal energy consumption (OSTEC) decreases by 20&#37; with an increase in the number of HRUs from 1 to 10. For the different numbers of HRUs in the range of 1-10, the system OSTECs with solar-thermal system having 150m² of evacuated-tube collectors and 16m³ seawater storage tanks are 28&#37;-36&#37; lower compared to those without the solar thermal system.

DOI： 10.1016/j.desal.2015.04.003

Language：English   Publishing type：Research paper (scientific journal)  

This paper presents an advanced desalination cycle called "MEDAD" desalination which is a hybrid of the conventional multi-effect distillation (MED) and an adsorption cycle (AD). The combined cycles allow some of MED stages to operate below ambient temperature, as low as 5. °C in contrast to the conventional MED. The MEDAD cycle results in a quantum increase of distillate production at the same top-brine condition. Being lower than the ambient temperature for the bottom stages of hybrid cycle, ambient energy can now be scavenged by the MED processes whilst the AD cycle is powered by low temperature waste heat from exhaust or renewable sources. In this paper, we present the experiments of a 3-stage MED and MEDAD plants. These plants have been tested at assorted heat source temperatures from 15. °C to 70. °C and with portable water as a feed. All system states are monitored including the distillate production and power consumption and the measured results are expressed in terms of performance ratio (PR). It is observed that the synergetic matching of MEDAD cycle led to a quantum increase in distillate production, up to 2.5 to 3 folds vis-a-vis to a conventional MED of the same rating.

DOI： 10.1016/j.apenergy.2015.03.062

Language：Others   Publishing type：Research paper (scientific journal)  

This paper presents an advanced desalination cycle called "MEDAD" desalination which is a hybrid of the conventional multi-effect distillation (MED) and an adsorption cycle (AD). The combined cycles allow some of MED stages to operate below ambient temperature, as low as 5. °C in contrast to the conventional MED. The MEDAD cycle results in a quantum increase of distillate production at the same top-brine condition. Being lower than the ambient temperature for the bottom stages of hybrid cycle, ambient energy can now be scavenged by the MED processes whilst the AD cycle is powered by low temperature waste heat from exhaust or renewable sources. In this paper, we present the experiments of a 3-stage MED and MEDAD plants. These plants have been tested at assorted heat source temperatures from 15. °C to 70. °C and with portable water as a feed. All system states are monitored including the distillate production and power consumption and the measured results are expressed in terms of performance ratio (PR). It is observed that the synergetic matching of MEDAD cycle led to a quantum increase in distillate production, up to 2.5 to 3 folds vis-a-vis to a conventional MED of the same rating.

DOI： 10.1016/j.apenergy.2015.03.062

Language：English   Publishing type：Research paper (scientific journal)  

The energy, water and environment nexus is a crucial factor when considering the future development of desalination plants or industry in the water-stressed economies. New generation of desalination processes or plants has to meet the stringent environment discharge requirements and yet the industry remains highly energy efficient and sustainable when producing good potable water. Water sources, either brackish or seawater, have become more contaminated as feed while the demand for desalination capacities increase around the world. One immediate solution for energy efficiency improvement comes from the hybridization of the proven desalination processes to the newer processes of desalination: For example, the integration of the available thermally-driven to adsorption desalination (AD) cycles where significant thermodynamic synergy can be attained when cycles are combined. For these hybrid cycles, a quantum improvement in energy efficiency as well as in increase in water production can be expected. The advent of MED with AD cycles, or simply called the MEDAD cycles, is one such example where seawater desalination can be pursued and operated in cogeneration with the electricity production plants: The hybrid desalination cycles utilize only the low exergy bled-steam at low temperatures, complemented with waste exhaust or renewable solar thermal heat at temperatures between 60 and 80. °C. In this paper, the authors have reported their pioneered research on aspects of AD and related hybrid MEDAD cycles, both at theoretical models and experimental pilots. Using the cogeneration of electricity and desalination concept, the authors examined the cost apportionment of fuel cost by the quality or exergy of working steam for such cogeneration configurations.

DOI： 10.1016/j.desal.2014.10.025

Language：English   Publishing type：Research paper (scientific journal)  

In the study, an investigation and comparison of the thermal performance and cost effectiveness of an active-indirect solar hot water plant (SHWP) at Incheon (Korea), Jeddah (Saudi Arabia) and Changi (Singapore) international airports are carried out. Plant performances are analyzed for various collector areas and storage tank volumes at the ASHRAE standard flow rate and are reported in terms of the annual solar fraction, solar thermal rating, as well as the capital payback period and annualized life cycle savings. The main objective of this study is to optimize a SHWP that supplies water at 65°C to a flight kitchen for the economic benefits for an average daily energy demand. For the energy demand of 100 m³/day, the minimum payback periods of SHWPs at Incheon, Jeddah and Changi airports are 8.94 years with A_c= 1140 m²and V_t= 32 m³, 5.91 years with A_c= 750 m²and V_t= 24 m³and 8.39 years with A_c= 1050 m²and V_t= 28 m³, respectively.

Language：English   Publishing type：Research paper (scientific journal)  

Mogok gem corundum samples from twelve localities were analyzed for trace element signatures (LA-ICP-MS method) and oxygen isotope values (δ¹⁸O, by laser fluorination). The study augmented earlier findings on Mogok gem suites that suggested the Mogok tract forms a high vanadium gem corundum area and also identified rare alluvial ruby and sapphire grains characterised by unusually high silicon, calcium and gallium, presence of noticeable boron, tin and niobium and very low iron, titanium and magnesium contents. Oxygen isotope values (δ¹⁸O) for the ruby and high Si-Ca-Ga corundum (20‰–25‰) and for sapphire (10‰–20‰) indicate typical crustal values, with values >20‰ being typical of carbonate genesis. The high Si-Ca-Ga ruby has high chromium (up to 3.2 wt % Cr) and gallium (up to 0. 08 wt % Ga) compared to most Mogok ruby (<2 wt % Cr; <0.02 wt % Ga). In trace element ratio plots the Si-Ca-Ga-rich corundum falls into separate fields from the typical Mogok metamorphic fields. The high Ga/Mg ratios (46–521) lie well within the magmatic range (>6), and with other features suggest a potential skarn-like, carbonate-related genesis with a high degree of magmatic fluid input The overall trace element results widen the range of different signatures identified within Mogok gem corundum suites and indicate complex genesis. The expanded geochemical platform, related to a variety of metamorphic, metasomatic and magmatic sources, now provides a wider base for geographic typing of Mogok gem corundum suites. It allows more detailed comparisons with suites from other deposits and will assist identification of Mogok gem corundum sources used in jewelry.

DOI： 10.3390/min5010061

Language：Others   Publishing type：Research paper (scientific journal)  

Mogok gem corundum samples from twelve localities were analyzed for trace element signatures (LA-ICP-MS method) and oxygen isotope values (δ O, by laser fluorination). The study augmented earlier findings on Mogok gem suites that suggested the Mogok tract forms a high vanadium gem corundum area and also identified rare alluvial ruby and sapphire grains characterised by unusually high silicon, calcium and gallium, presence of noticeable boron, tin and niobium and very low iron, titanium and magnesium contents. Oxygen isotope values (δ O) for the ruby and high Si-Ca-Ga corundum (20‰–25‰) and for sapphire (10‰–20‰) indicate typical crustal values, with values >20‰ being typical of carbonate genesis. The high Si-Ca-Ga ruby has high chromium (up to 3.2 wt &#37; Cr) and gallium (up to 0. 08 wt &#37; Ga) compared to most Mogok ruby (<2 wt &#37; Cr; <0.02 wt &#37; Ga). In trace element ratio plots the Si-Ca-Ga-rich corundum falls into separate fields from the typical Mogok metamorphic fields. The high Ga/Mg ratios (46–521) lie well within the magmatic range (>6), and with other features suggest a potential skarn-like, carbonate-related genesis with a high degree of magmatic fluid input The overall trace element results widen the range of different signatures identified within Mogok gem corundum suites and indicate complex genesis. The expanded geochemical platform, related to a variety of metamorphic, metasomatic and magmatic sources, now provides a wider base for geographic typing of Mogok gem corundum suites. It allows more detailed comparisons with suites from other deposits and will assist identification of Mogok gem corundum sources used in jewelry. 18 18

DOI： 10.3390/min5010061

Language：English   Publishing type：Research paper (scientific journal)  

Adsorption characteristics of CH₄ on the carbonaceous porous material is evaluated for possible application in adsorbed natural gas (ANG) system. Adsorption uptakes at assorted temperatures (25-80 °C) and pressures ranging from ambient to relatively high pressure i.e., 8.0 MPa are experimentally investigated. Surface characteristics such as pore surface area, micropore volume and pore size distribution of the adsorbent (Maxsorb III) are first evaluated using Classical Volumetric Method i.e., the manometric method with N₂ gas adsorption at 77 K. The sorption measurements for methane, CH₄ gas are carried out by thermogravimetric (TGA) method using magnetic suspension balance coupled with the automatic dosing system. The buoyancy measurements were first conducted using Helium gas as adsorbate. Buoyancy correction is applied to all sets of measured data and the specific uptake capacities (g/g of adsorbent) at various temperatures and pressures were calculated. The isotherm data were then fitted using Langmuir and Tòth isotherm models. It is observed that the data can be satisfactorily fitted using Tòth model with excellent fitting accuracy around 2.2% within the experimental range. The outcome of the present study especially the adsorption data at high pressures is applicable to accurate design and modeling of Adsorbed Natural Gas (ANG) systems.

DOI： 10.1016/j.applthermaleng.2014.04.076

Language：Others   Publishing type：Research paper (scientific journal)  

This paper presents an advanced desalination cycle that hybridizes a conventional multi-effect distillation (MED) and an emerging yet low-energy adsorption cycle (AD). The hybridization of these cycles, known as MED + AD or MEDAD in short, extends the limited temperature range of the MED, typically from 65 °C at top-brine temperature (TBT) to a low-brine temperature (LBT) of 40 °C to a lower LBT of 5 °C, whilst the TBT remains the same. The integration of cycles is achieved by having vapor uptake by the adsorbent in AD cycle, extracting from the vapor emanating from last effect of MED. By increasing the range of temperature difference (DT) of a MEDAD, its design can accommodate additional condensation-evaporation stages that capitalize further the energy transfer potential of expanding steam. Numerical model for the proposed MEDAD cycle is presented and compared with the water production rates of conventional and hybridized MEDs. The improved MEDAD design permits the latter stages of MED to operate below the ambient temperature, scavenging heat from the ambient air. The increase recovery of water from the seawater feed may lead to higher solution concentration within the latter stages, but the lower saturation temperatures of these stages mitigate the scaling and fouling effects.

DOI： 10.1016/j.applthermaleng.2014.03.064

Language：Others   Publishing type：Research paper (scientific journal)  

The modeling of the adsorption isotherms and kinetics of the adsorbent + adsorbate pair is essential in simulating the performance of a pressurized adsorption chiller. In this work, the adsorption kinetics is analyzed from data measured using a magnetic suspension balance. The Statistical Rate Theory describes the Dubinin-Astakhov (DA) equation and extended to obtain an expression for transient analysis. Hence both the experimental excess equilibria data and the adsorption kinetics data may then be fitted to obtain the necessary parameters to fit the curves. The results fit the data very well within 6&#37; of the error of regression.

DOI： 10.1016/j.applthermaleng.2014.07.023

Language：Others   Publishing type：Research paper (scientific journal)  

Adsorption characteristics of CH on the carbonaceous porous material is evaluated for possible application in adsorbed natural gas (ANG) system. Adsorption uptakes at assorted temperatures (25-80 °C) and pressures ranging from ambient to relatively high pressure i.e., 8.0 MPa are experimentally investigated. Surface characteristics such as pore surface area, micropore volume and pore size distribution of the adsorbent (Maxsorb III) are first evaluated using Classical Volumetric Method i.e., the manometric method with N gas adsorption at 77 K. The sorption measurements for methane, CH gas are carried out by thermogravimetric (TGA) method using magnetic suspension balance coupled with the automatic dosing system. The buoyancy measurements were first conducted using Helium gas as adsorbate. Buoyancy correction is applied to all sets of measured data and the specific uptake capacities (g/g of adsorbent) at various temperatures and pressures were calculated. The isotherm data were then fitted using Langmuir and Tòth isotherm models. It is observed that the data can be satisfactorily fitted using Tòth model with excellent fitting accuracy around 2.2&#37; within the experimental range. The outcome of the present study especially the adsorption data at high pressures is applicable to accurate design and modeling of Adsorbed Natural Gas (ANG) systems. 4 2 4

DOI： 10.1016/j.applthermaleng.2014.04.076

Language：English   Publishing type：Research paper (scientific journal)  

This paper presents an advanced desalination cycle that hybridizes a conventional multi-effect distillation (MED) and an emerging yet low-energy adsorption cycle (AD). The hybridization of these cycles, known as MED + AD or MEDAD in short, extends the limited temperature range of the MED, typically from 65 °C at top-brine temperature (TBT) to a low-brine temperature (LBT) of 40 °C to a lower LBT of 5 °C, whilst the TBT remains the same. The integration of cycles is achieved by having vapor uptake by the adsorbent in AD cycle, extracting from the vapor emanating from last effect of MED. By increasing the range of temperature difference (DT) of a MEDAD, its design can accommodate additional condensation-evaporation stages that capitalize further the energy transfer potential of expanding steam. Numerical model for the proposed MEDAD cycle is presented and compared with the water production rates of conventional and hybridized MEDs. The improved MEDAD design permits the latter stages of MED to operate below the ambient temperature, scavenging heat from the ambient air. The increase recovery of water from the seawater feed may lead to higher solution concentration within the latter stages, but the lower saturation temperatures of these stages mitigate the scaling and fouling effects.

DOI： 10.1016/j.applthermaleng.2014.03.064

Language：English   Publishing type：Research paper (scientific journal)  

The modeling of the adsorption isotherms and kinetics of the adsorbent + adsorbate pair is essential in simulating the performance of a pressurized adsorption chiller. In this work, the adsorption kinetics is analyzed from data measured using a magnetic suspension balance. The Statistical Rate Theory describes the Dubinin-Astakhov (DA) equation and extended to obtain an expression for transient analysis. Hence both the experimental excess equilibria data and the adsorption kinetics data may then be fitted to obtain the necessary parameters to fit the curves. The results fit the data very well within 6% of the error of regression.

DOI： 10.1016/j.applthermaleng.2014.07.023

Language：English   Publishing type：Research paper (scientific journal)  

This paper presents an environment-friendly adsorption chiller using Zeolite FAM Z01-water pair as opposed to the conventional silica gel and water pair. The adsorbent, zeolite, is thinly coated onto the surfaces of fin-tube heat exchanger for faster rates of heat and mass transfer. Another feature of the adsorption chiller is the use of a lever-countered weighted valve which can be open or closed by the pressure difference between the reactors and the condenser or evaporator. Experiments are conducted to evaluate the performance of zeolite-based chiller in terms of total heat input, cooling capacity, and coefficient of performance (COP) with respect to heat source temperature and adsorption/desorption cycle time where an optimal operational zone can be determined: (i) hot water inlet temperatures range from 65. °C to 85. °C, (ii) adsorption/desorption cycle times of 200-300. s at optimum cooling and COP, Entropy analyses have been conducted to understand the irreversibility contributed by both the desorption and adsorption beds at assorted hot water inlet temperatures and cycle time.

DOI： 10.1016/j.apenergy.2014.01.086

Language：Others   Publishing type：Research paper (scientific journal)  

This paper presents an environment-friendly adsorption chiller using Zeolite FAM Z01-water pair as opposed to the conventional silica gel and water pair. The adsorbent, zeolite, is thinly coated onto the surfaces of fin-tube heat exchanger for faster rates of heat and mass transfer. Another feature of the adsorption chiller is the use of a lever-countered weighted valve which can be open or closed by the pressure difference between the reactors and the condenser or evaporator. Experiments are conducted to evaluate the performance of zeolite-based chiller in terms of total heat input, cooling capacity, and coefficient of performance (COP) with respect to heat source temperature and adsorption/desorption cycle time where an optimal operational zone can be determined: (i) hot water inlet temperatures range from 65. °C to 85. °C, (ii) adsorption/desorption cycle times of 200-300. s at optimum cooling and COP, Entropy analyses have been conducted to understand the irreversibility contributed by both the desorption and adsorption beds at assorted hot water inlet temperatures and cycle time. © 2014 Elsevier Ltd.

DOI： 10.1016/j.apenergy.2014.01.086

Language：English   Publishing type：Research paper (scientific journal)  

The adsorption characteristics of microporous ferroaluminophosphate adsorbent (FAM-Z01, Mitsubishi Plastics) are evaluated for possible application in adsorption desalination and cooling (AD) cycles. A particular interest is its water vapor uptake behavior at assorted adsorption temperatures and pressures whilst comparing them to the commercial silica gels of AD plants. The surface characteristics are first carried out using N₂ gas adsorption followed by the water vapor uptake analysis for temperature ranging from 20°C to 80°C. We propose a hybrid isotherm model, composing of the Henry and the Sips isotherms, which can be integrated to satisfactorily fit the experimental data of water adsorption on the FAM-Z01. The hybrid model is selected to fit the unusual isotherm shapes, that is, a low adsorption in the initial section and followed by a rapid vapor uptake leading to a likely micropore volume filling by hydrogen bonding and cooperative interaction in micropores. It is shown that the equilibrium adsorption capacity of FAM-Z01 can be up to 5 folds higher than that of conventional silica gels. Owing to the quantum increase in the adsorbate uptake, the FAM-Z01 has the potential to significantly reduce the footprint of an existing AD plant for the same output capacity.

DOI： 10.1016/j.desal.2014.04.009

Language：Others   Publishing type：Research paper (scientific journal)  

This study focuses on the water quality assessment (feed, product and brine) of the pilot adsorption desalination (AD) plant. Seawater from the Red Sea is used as feed to the AD plant. Water quality tests are evaluated by complying the Environmental Protection Agency (EPA) standards with major primary and secondary inorganic drinking water pollutants and other commonly tested water quality parameters. Chemical testing of desalinated water at the post desalination stage confirms the high quality of produced fresh water. Test results have shown that the adsorption desalination process is very effective in eliminating all forms of salts, as evidenced by the significant reduction of the TDS levels from approximately 40,000. ppm in feed seawater to less than 10. ppm. Test results exhibit extremely low levels of parameters which are generally abundant in feed seawater. The compositions of seawater and process related parameters such as chloride, sodium, bromide, sulfate, calcium, magnesium, and silicate in desalinated water exhibit values of less than 0.1. ppm. Reported conductivity measurements of desalinated water are comparable to distilled water conductivity levels and ranged between 2 and 6. μS/cm while TOC and TIC levels are also extremely low and its value is less than 0.5. ppm. © 2014 Elsevier B.V.

DOI： 10.1016/j.desal.2014.03.021

Language：Others   Publishing type：Research paper (scientific journal)  

The adsorption characteristics of microporous ferroaluminophosphate adsorbent (FAM-Z01, Mitsubishi Plastics) are evaluated for possible application in adsorption desalination and cooling (AD) cycles. A particular interest is its water vapor uptake behavior at assorted adsorption temperatures and pressures whilst comparing them to the commercial silica gels of AD plants. The surface characteristics are first carried out using N gas adsorption followed by the water vapor uptake analysis for temperature ranging from 20°C to 80°C. We propose a hybrid isotherm model, composing of the Henry and the Sips isotherms, which can be integrated to satisfactorily fit the experimental data of water adsorption on the FAM-Z01. The hybrid model is selected to fit the unusual isotherm shapes, that is, a low adsorption in the initial section and followed by a rapid vapor uptake leading to a likely micropore volume filling by hydrogen bonding and cooperative interaction in micropores. It is shown that the equilibrium adsorption capacity of FAM-Z01 can be up to 5 folds higher than that of conventional silica gels. Owing to the quantum increase in the adsorbate uptake, the FAM-Z01 has the potential to significantly reduce the footprint of an existing AD plant for the same output capacity. © 2014 Elsevier B.V. 2

DOI： 10.1016/j.desal.2014.04.009

Language：English   Publishing type：Research paper (scientific journal)  

This study focuses on the water quality assessment (feed, product and brine) of the pilot adsorption desalination (AD) plant. Seawater from the Red Sea is used as feed to the AD plant. Water quality tests are evaluated by complying the Environmental Protection Agency (EPA) standards with major primary and secondary inorganic drinking water pollutants and other commonly tested water quality parameters. Chemical testing of desalinated water at the post desalination stage confirms the high quality of produced fresh water. Test results have shown that the adsorption desalination process is very effective in eliminating all forms of salts, as evidenced by the significant reduction of the TDS levels from approximately 40,000. ppm in feed seawater to less than 10. ppm. Test results exhibit extremely low levels of parameters which are generally abundant in feed seawater. The compositions of seawater and process related parameters such as chloride, sodium, bromide, sulfate, calcium, magnesium, and silicate in desalinated water exhibit values of less than 0.1. ppm. Reported conductivity measurements of desalinated water are comparable to distilled water conductivity levels and ranged between 2 and 6. μS/cm while TOC and TIC levels are also extremely low and its value is less than 0.5. ppm.

DOI： 10.1016/j.desal.2014.03.021

Language：Others   Publishing type：Research paper (scientific journal)  

This article presents the performance analysis of single-stage two bed adsorption refrigeration cycles working at pressurized conditions. Four specimens of activated carbon adsorbent and refrigerant pairs, which are Maxsorb III with Propane, n-butane, HFC-134a, R-32, and R507a are studied. The relationships between equilibrium pressures, adsorbent temperatures and equilibrium adsorption concentrations (Dühring diagram) are presented. Parametric analyses have been carried by varying the regeneration, cooling water and evaporation temperatures. Theoretical analysis for these adsorption cycles working pairs shows that the choice of refrigerants amongst these pairs depends on the operational requirements and conditions. The authors thus present in a graphical representation of the choice based on these requirements. At higher required chilling temperatures and lower ambient temperatures, R-32 is preferred with higher specific cooling capacities. When lower temperature cooling is required while the ambient temperature is high, Propane is preferred. © 2014 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.applthermaleng.2014.02.063

Language：English   Publishing type：Research paper (scientific journal)  

The performance of a novel dew-point evaporative air cooler is theoretically investigated in this paper. The novel dew-point evaporative air cooler, based on a counter-flow closed-loop configuration, is able to cool air to temperature below ambient wet bulb temperature and approaching dew-point temperature. A computational model for the cooler has been developed. We validated the model by comparing the temperature distribution and outlet air conditions against experimental data from literature. The model demonstrated close agreement with the experimental findings to within ±7.5%. Employing the validated model, we studied the cooler performance due to the effects of (i) varying channel dimensions; (ii) employing room return air as the working fluid; and (iii) installing of physical ribs along the channel length. Using these means, we have demonstrated improved performance of the dew-point cooler - enabling it to achieve higher efficiencies. Operating under variant inlet air temperature and humidity conditions, simulated results showed that the wet bulb effectiveness ranged from 122% to 132% while dew-point effectiveness spanned 81%-93%.

DOI： 10.1016/j.applthermaleng.2013.11.070

Language：Others   Publishing type：Research paper (scientific journal)  

The performance of a novel dew-point evaporative air cooler is theoretically investigated in this paper. The novel dew-point evaporative air cooler, based on a counter-flow closed-loop configuration, is able to cool air to temperature below ambient wet bulb temperature and approaching dew-point temperature. A computational model for the cooler has been developed. We validated the model by comparing the temperature distribution and outlet air conditions against experimental data from literature. The model demonstrated close agreement with the experimental findings to within ±7.5&#37;. Employing the validated model, we studied the cooler performance due to the effects of (i) varying channel dimensions; (ii) employing room return air as the working fluid; and (iii) installing of physical ribs along the channel length. Using these means, we have demonstrated improved performance of the dew-point cooler - enabling it to achieve higher efficiencies. Operating under variant inlet air temperature and humidity conditions, simulated results showed that the wet bulb effectiveness ranged from 122&#37; to 132&#37; while dew-point effectiveness spanned 81&#37;-93&#37;. © 2013 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.applthermaleng.2013.11.070

Language：English   Publishing type：Research paper (other academic)  

This paper presents the modeling and successful operation of a miniaturized Pressurized Adsorption Chiller (PAC) which utilizes Propane as the adsorbate and activated carbon as the adsorbent. The Propane + Activated Carbon Pair has previously been found to be able to function under adverse conditions where low temperature refrigeration is required, placed at high ambient temperature locales. This work focuses on the modeling of the pressure equalization process, and the feasibility of the working pair. A maximum cooling load of 7W is tested for the various cycle times. Experimentally, it has been found to successfully provide cooling, albeit with a low COP (<0.5), typical of waste heat driven systems.

Language：Others   Publishing type：Research paper (scientific journal)  

Rubies and sapphires are of both scientific and commercial interest. These gemstones are corundum colored by transition elements within the alumina crystal lattice: Cr yields red in ruby and Fe , Fe , and Ti ionic interactions color sapphires. A minor ion, V induces slate to purple colors and color change in some sapphires, but its role in coloring rubies remains enigmatic. Trace element and oxygen isotope composition provide genetic signatures for natural corundum and assist geographic typing. Here, we show that V can dominate chromophore contents in Mogok ruby suites. This raises implications for their color quality, enhancement treatments, geographic origin, exploration and exploitation and their comparison with rubies elsewhere. Precise LA-ICP-MS analysis of ruby and sapphire from Mogok placer and in situ deposits reveal that V can exceed 5,000 ppm, giving V/Cr, V/Fe and V/Ti ratios up to 26, 78, and 97 respectively. Such values significantly exceed those found elsewhere suggesting a localized geological control on V-rich ruby distribution. Our results demonstrate that detailed geochemical studies of ruby suites reveal that V is a potential ruby tracer, encourage comparisons of V/Cr-variation between ruby suites and widen the scope for geographic typing and genesis of ruby. This will allow more precise comparison of Asian and other ruby fields and assist confirmation of Mogok sources for rubies in historical and contemporary gems and jewelry. 3+ 2+ 3+ 4+ 3+

DOI： 10.1007/s00126-014-0545-0

Language：English   Publishing type：Research paper (scientific journal)  

Rubies and sapphires are of both scientific and commercial interest. These gemstones are corundum colored by transition elements within the alumina crystal lattice: Cr³⁺ yields red in ruby and Fe²⁺, Fe³⁺, and Ti⁴⁺ ionic interactions color sapphires. A minor ion, V³⁺ induces slate to purple colors and color change in some sapphires, but its role in coloring rubies remains enigmatic. Trace element and oxygen isotope composition provide genetic signatures for natural corundum and assist geographic typing. Here, we show that V can dominate chromophore contents in Mogok ruby suites. This raises implications for their color quality, enhancement treatments, geographic origin, exploration and exploitation and their comparison with rubies elsewhere. Precise LA-ICP-MS analysis of ruby and sapphire from Mogok placer and in situ deposits reveal that V can exceed 5,000 ppm, giving V/Cr, V/Fe and V/Ti ratios up to 26, 78, and 97 respectively. Such values significantly exceed those found elsewhere suggesting a localized geological control on V-rich ruby distribution. Our results demonstrate that detailed geochemical studies of ruby suites reveal that V is a potential ruby tracer, encourage comparisons of V/Cr-variation between ruby suites and widen the scope for geographic typing and genesis of ruby. This will allow more precise comparison of Asian and other ruby fields and assist confirmation of Mogok sources for rubies in historical and contemporary gems and jewelry.

DOI： 10.1007/s00126-014-0545-0

Language：English   Publishing type：Research paper (scientific journal)  

This article presents the performance analysis of single-stage two bed adsorption refrigeration cycles working at pressurized conditions. Four specimens of activated carbon adsorbent and refrigerant pairs, which are Maxsorb III with Propane, n-butane, HFC-134a, R-32, and R507a are studied. The relationships between equilibrium pressures, adsorbent temperatures and equilibrium adsorption concentrations (Dühring diagram) are presented. Parametric analyses have been carried by varying the regeneration, cooling water and evaporation temperatures. Theoretical analysis for these adsorption cycles working pairs shows that the choice of refrigerants amongst these pairs depends on the operational requirements and conditions. The authors thus present in a graphical representation of the choice based on these requirements. At higher required chilling temperatures and lower ambient temperatures, R-32 is preferred with higher specific cooling capacities. When lower temperature cooling is required while the ambient temperature is high, Propane is preferred.

DOI： 10.1016/j.applthermaleng.2014.02.063

Language：English   Publishing type：Research paper (other academic)  

Adsorption process forms the core of adsorption chiller and desiccant dehumidifier. In the conventional adsorption machines, adsorbent is embedded in between heat exchanger fins by wire meshes. Poor contact between adsorbent material and metal fins, and among adsorbent solids incurred in such method significantly impedes heat transfer efficiency, and hence the performance of the adsorption machines. The presented work is aimed to improve heat transfer of an adsorbent embedded heat exchanger by introducing binder. Several organic or inorganic binders are tested with adsorbent silica gel 3A and aluminium pieces, among which it is found that Hydroxyethyl cellulose (HEC) is the most suitable. Experiment is conducted to study the influence of the binder on the overall heat transfer coefficient of the heat exchanger. The results show that a significant improvement of heat transfer is observed with respect to both value and time.

Language：English   Publishing type：Research paper (scientific journal)  

This paper presents an advanced desalination cycle called “MEDAD” desalination which is a hybrid of the traditional multi-effect distillation (MED) and the adsorption cycle (AD). The combined cycles break the operating regime of conventional MED system and allow some stages to operate below ambient temperature, as low as 5°C in contrast to the conventional MED: The MED AD cycle results in a quantum increase of distillate production at the same top-brine condition. Being lower than the ambient temperature for the bottom stages of hybrid, ambient energy can now be scavenged by the MED processes whilst the AD cycle is powered by low temperature waste heat from exhaust or renewable sources. In this paper, we present the experiments of a 3-stage MED and MED AD plants that were fabricated and installed in the air-conditioning laboratory of the National University of Singapore. These plants have been tested at assorted heat source temperatures ranging from 15°C to 70°C. All system states are monitored including the stages temperature and distillate production. It is observed that the synergetic matching of MED AD cycle led to a quantum increase in distillate production, up to 2.5 to 3 folds vis-a-vis to a conventional MED of the same rating.

Language：English   Publishing type：Research paper (scientific journal)  

Multi-effect distillation (MED) systems are proven and energy efficient thermally-driven desalination systems for handling harsh seawater feed in the Gulf region. The high cycle efficiency is markedly achieved by latent energy re-use with minimal stage temperature-difference across the condensing steam and the evaporating saline seawater in each stage. The efficacies of MED system are (i) its low stage-temperature-difference between top brine temperature (TBT) and final condensing temperature, (ii) its robustness to varying salinity and ability to handle harmful algae Blooming (HABs) and (iii) its compact foot-print per unit water output. The practical TBT of MED systems, hitherto, is around 65 C for controllable scaling and fouling with the ambient-limited final condenser temperature, usually from 30 to 45 C. The adsorption (ADC) cycles utilize low-temperature heat sources (typically below 90 C) to produce useful cooling power and potable water. Hybridizing MED with AD cycles, they synergistically improve the water production rates at the same energy input whilst the AD cycle is driven by the recovered waste heat. We present a practical AD + MED combination that can be retrofitted to existing MEDs: The cooling energy of AD cycle through the water vapor uptake by the adsorbent is recycled internally, providing lower temperature condensing environment in the effects whilst the final condensing temperature of MED is as low as 5-10 C, which is below ambient. The increase in the temperature difference between TBT and final condensing temperature accommodates additional MED stages. A detailed numerical model is presented to capture the transient behaviors of heat and mass interactions in the combined AD + MED cycles and the results are presented in terms of key variables. It is observed that the water production rates of the combined cycle increase to give a GOR of 8.8 from an initial value of 5.9.

DOI： 10.1016/j.applthermaleng.2013.09.023

Language：English   Publishing type：Research paper (other academic)  

Adsorption Desalination cum Cooling (ADC) process is a cost effective and environmental-friendly fresh water resource. In contrast to the conventional thermal desalination systems such as multi-stage flash (MSF) and multi-effect distillation (MED), the evaporation of feed water (seawater or brackish water) occurs at lower temperatures, typically from 5°C to 30°C. The salient advantages of the ADC cycle over the other desalination technologies are: (i) it can be powered by a low-temperature heat source, (ii) it has almost no major moving parts, (iii) it has low maintenance, (iv) it is environmental-friendly with lowest CO2 emission at 0.64 kg/m3 of water, 5 times lesser emission than a RO plant, and more than 10 times lesser with the MSF, (v) it utilizes zero chemicals in the pretreatment step and (vi) it can achieve high recovery ratio (over 80%). ADC cycles utilize the lowtemperature heat sources to perform simultaneous desalination and cooling power production, i.e., 8 to 22 m3 per day and 24 to 35 Rton per ton of silica gel. The implementation of adsorption-desorption principles to evaporation-condensation of seawater enables the AD cycles to achieve low specific energy consumption of 1.38 kWh/m3. In this study, it has been shown that AD cycle can be operated at higher feed salinity compared to conventional thermal- or membrane-based desalination technologies, thus could play a pertinent role in zero liquid discharge process.

Language：English   Publishing type：Research paper (other academic)  

In this paper, a multi-stage vacuum membrane distillation (VMD) system has been developed for seawater desalination process where the feed seawater is employed as the coolant medium. A rigorous mathematical model for such system is formulated to investigate the performance in terms of distillate production with respect to the seawater-coolant feed flow configurations such as the backward feed and the parallel feed. The VMD model is developed based on the commercially available capillary membrane module (MD020CP2N, Mycrodyn), which consists of an array of porous hydrophobic membranes, assembled together in a shell-and-tube module. The proposed multi-stage VMD desalination system consists of 24 stages with multiple recoveries of condensation heat to the feed seawater, i.e., coolant for the condensation, with the shell diameter of 0.03 m, fiber length of 0.5 m and 100 hollow fibers. It is observed that total distillate production of multi-stage VMD system with parallel feed arrangement is relatively superior as compared to that with backward feed type.

Language：English   Publishing type：Research paper (scientific journal)  

This paper studies the water equilibrium uptake on two lype of adsorbents, namely silica gel RD powder and Zeolite FAM Z01. A novel adsorption isotherm model is proposed to regress the experimental data of the both adsorbents. For the silica gel-water pair, die proposed model generates more precise data regression than the classic DA and Tóth equations. In the case of the zeolite-water pair, the new model well fits its unique S-shape isotherms at various adsorption temperatures. The linear behavior at both low and high relative pressure regions, and the sharp rise in between the two regions arc accurately captured. The model produces R²value 0.997 and NRMSE error 3.15% for the former pair, and 0.997 R²and 6.05% error for the zeolite-water pair in the experiment range.

Language：English   Publishing type：Research paper (scientific journal)  

In the last five years, fine Burmese blue sapphires from the Baw Mar area of Mogok have reached the market. The faceted stones typically show a strong pleochroism from greenish to violetish blue when viewed perpendicular and parallel to the c-axis, respectively, with medium to strong saturation and medium to dark tone. Most of the samples were relatively clean under the microscope, showing multiple twinning with whitish needle-like inclusions (presumably boehmite) at the intersections. Often, these inclusions were associated with stress tension fissures. Needles, most likely rutile, were found only occasionally, but small platelets and needle-like particles, probably ilmenite, appeared more frequently. Most of the stones contained surface-reaching open and healed fissures, but crystal inclusions of K-feldspar and mica (identified by Raman) were occasionally encountered. The sapphires also had a relatively high iron content, low gallium, and very low titanium. Their Ga/Mg ratio varied from 0.6 to 17. Their UV-Vis- NIR spectra displayed intense iron-related absorptions, and the FTIR absorption spectra presented mainly boehmite- and mica-related bands. Based on careful microscopic observations, combined with spectroscopic and chemical analysis, the sapphire from Baw Mar can, in most cases, be distinguished from the blue sapphire of other localities.

DOI： 10.5741/GEMS.49.4.223

Language：Others   Publishing type：Research paper (scientific journal)  

In the last five years, fine Burmese blue sapphires from the Baw Mar area of Mogok have reached the market. The faceted stones typically show a strong pleochroism from greenish to violetish blue when viewed perpendicular and parallel to the c-axis, respectively, with medium to strong saturation and medium to dark tone. Most of the samples were relatively clean under the microscope, showing multiple twinning with whitish needle-like inclusions (presumably boehmite) at the intersections. Often, these inclusions were associated with stress tension fissures. Needles, most likely rutile, were found only occasionally, but small platelets and needle-like particles, probably ilmenite, appeared more frequently. Most of the stones contained surface-reaching open and healed fissures, but crystal inclusions of K-feldspar and mica (identified by Raman) were occasionally encountered. The sapphires also had a relatively high iron content, low gallium, and very low titanium. Their Ga/Mg ratio varied from 0.6 to 17. Their UV-Vis- NIR spectra displayed intense iron-related absorptions, and the FTIR absorption spectra presented mainly boehmite- and mica-related bands. Based on careful microscopic observations, combined with spectroscopic and chemical analysis, the sapphire from Baw Mar can, in most cases, be distinguished from the blue sapphire of other localities. © 2013 Gemological Institute of America.

DOI： 10.5741/GEMS.49.4.223

Language：English   Publishing type：Research paper (scientific journal)  

This Article presents a theoretical framework for the understanding of pressurized adsorption systems using the statistical rate methodology. Utilizing results from the statistical rate theory, basic thermodynamic variables including enthalpy (h_a), entropy (s_a), and the specific heat capacity (c_p,a) of the adsorbed phase are derived using the thermodynamic requirements of chemical equilibrium, Gibbs law, as well as Maxwell relations. A built-in constant (K) describes the adsorbed molecular partition function (q^s), and it captures the heterogeneous properties of the adsorbent + adsorbate pair at equilibrium states. Improved adsorbed-phase volume considerations were incorporated in the formulations of these variables where they could be utilized with relative ease for analyzing the energetic performances of any practical adsorption system. In this Article, we have demonstrated how derived thermodynamic quantities can bridge the information gap with respect to the states of adsorbed phase, as well as resolved some theoretical inconsistencies that were found in previously derived quantities. Experimentally, the adsorption isotherms of propane (refrigerant) on activated carbon powder (Maxsorb III) for temperatures from 5 to 75 C and pressures up to 8 bar are presented, and they are used to illustrate the behaviors of the adsorbed-phase during uptakes, temperatures, and pressure excursions or changes.

DOI： 10.1021/la403330t

Language：Others   Publishing type：Research paper (scientific journal)  

This Article presents a theoretical framework for the understanding of pressurized adsorption systems using the statistical rate methodology. Utilizing results from the statistical rate theory, basic thermodynamic variables including enthalpy (h ), entropy (s ), and the specific heat capacity (c ) of the adsorbed phase are derived using the thermodynamic requirements of chemical equilibrium, Gibbs law, as well as Maxwell relations. A built-in constant (K) describes the adsorbed molecular partition function (q ), and it captures the heterogeneous properties of the adsorbent + adsorbate pair at equilibrium states. Improved adsorbed-phase volume considerations were incorporated in the formulations of these variables where they could be utilized with relative ease for analyzing the energetic performances of any practical adsorption system. In this Article, we have demonstrated how derived thermodynamic quantities can bridge the information gap with respect to the states of adsorbed phase, as well as resolved some theoretical inconsistencies that were found in previously derived quantities. Experimentally, the adsorption isotherms of propane (refrigerant) on activated carbon powder (Maxsorb III) for temperatures from 5 to 75 C and pressures up to 8 bar are presented, and they are used to illustrate the behaviors of the adsorbed-phase during uptakes, temperatures, and pressure excursions or changes. © 2013 American Chemical Society. a a p,a s

DOI： 10.1021/la403330t

Language：English   Publishing type：Research paper (other academic)  

Experimental kinetics results of propane in Maxsorb III activated carbon is obtained at temperatures of 10°C and 30°C, and pressures up to 800kPa using a magnetic suspension balance. A multi-gradient linear driving force (LDF) approximation is used for adsorbate uptake as a function of time. The LDF mass-transfer-rate coefficients were thus determined. Using this approach, the experimentally derived LDF coefficients based on independently measured kinetic parameters for propane in the activated-carbon bed agree very well with experimental results. The computational efficiency is gained by adopting this extended LDF model.

DOI： 10.4028/www.scientific.net/AMM.388.76

Language：English   Publishing type：Research paper (other academic)  

his article discusses the thermophysical properties of zeolite-based adsorbents. Three types of zeolite (Z-01, Z-02 and Z-05) with different chemical compositions developed by Mitsubishi Plastics, Inc. are analyzed for possible applications in adsorption chillers and desalination cycles driven by low-temperature waste heat sources. The experiments are performed using static volumetric method with N₂ gas sorption at 77 K. Thermophysical properties such as pore surface area, micropore volume and pore size distribution are evaluated using standard multipoint Brunauer-Emmett-Teller (BET) and Non-Local Density Functional Theory (NLDFT) methods. It is observed that Aluminosilicate functionalized Z-02 exhibits the highest surface area with huge micropore volume.

DOI： 10.4028/www.scientific.net/AMM.388.116

Language：English   Publishing type：Research paper (scientific journal)  

This paper discusses the performance analysis of an advanced adsorption desalination (AD) cycle with an internal heat recovery between the condenser and the evaporator. The AD cycle employs the adsorption-desorption principles to convert sea or brackish water into high-grade potable water with total dissolved solids (TDS) less than 10 ppm (mg/L) utilizing low-temperature heat source. The salient features of the AD cycle are the utilization of low temperature waste heat (typically 55 C to 85 C) with the employment of an environment-friendly silica gel/water pair and the low maintenance as it has no major moving parts other than the pumps and valves. For improved performance of the AD pilot plant, the internal heat recovery scheme between the condenser and evaporator has been implemented with a run-about water circuit between them. The efficacy of the scheme is analyzed in terms of key performance indicators such as the specific daily water production (SDWP) and the performance ratio (PR). Extensive experiments were performed for assorted heat source temperatures ranging from 70 C to 50 C. From the experiments, the SDWP of the AD cycle with the proposed heat recovery scheme is found to be 15 m
³
of water per ton of silica gel that is almost twice that of the yield obtained by a conventional AD cycle for the same operation conditions. Another important finding of AD desalination plant is that the advanced AD cycle could still be operational with an inlet heat source temperature of 50 C and yet achieving a SDWP of 4.3 m
³
- a feat that never seen by any heat-driven cycles.

DOI： 10.1016/j.ijheatmasstransfer.2013.06.053

Language：Others   Publishing type：Research paper (scientific journal)  

This paper describes the development of a simple hybrid desalination system of a Multi-Effect Distillation (MED) and an adsorption (AD) cycle operating at sub-atmospheric pressures and temperatures. By hybridizing the conventional MED with an AD cycle, there is a symbiotic enhancement of performances of both cycles. The performance enhancement is attributed to (i) the cascade of adsorbent's regeneration temperature and this extended the usage of thermal energy emanating from the brine heater and (ii) the vapor extraction from the last MED stage by AD cycle which provides the effect of lowering saturation temperatures of all MED stages to the extent of 5°C, resulting in scavenging of heat leaks into the MED stages from the ambient. The combined effects of the hybrid cycles increase the water production capacity of the desalination plant by nearly twofolds.In this paper, we demonstrate a hybrid cycle by simulating an 8-stage MED cycle which is coupled to an adsorption cycle for direct vapor extraction from the last MED stage. The sorption properties of silica gel is utilized (acting as a mechanical vapor compressor) to reduce the saturation temperatures of MED stages. The modeling utilizes the adsorption isotherms and kinetics of the adsorbent. +. adsorbate (silica-gel. +. water) pair along with the governing equations of mass, energy and concentration. For a 8-stage MED and AD cycles operating at assorted temperatures of 65-90°C, the results show that the water production rate increases from 60&#37; to twofolds when compared to the MED alone. The performance ratio (PR) and gain output ratio (GOR) also improve significantly. © 2012 Elsevier Ltd.

DOI： 10.1016/j.apenergy.2012.12.007

Language：English   Publishing type：Research paper (scientific journal)  

Thermo-physical properties, surface characteristics and water vapor uptake capacity are key parameters in the selection of adsorbent for an adsorption desalination (AD) cycle. In the AD cycles, silica gel is used as adsorbent due to their high water vapor uptake capacity, reliability, repeatability and inexpensiveness as compared to other adsorbents. Three types of commercially available silica gels (Type-RD 2560,Type-A5BW and Type-A⁺⁺) are investigated using a surface characteristic analyzer and their thermo-physical properties are evaluated using several analysis methods. The instrument used in this investigation employs the static volumetric method with liquid Nitrogen at 77 K as the filing fluid. The surface area of each adsorbent is studied using Brunauer-Emmett-Teller (BET) method whilst the pore size distribution (PSD) analysis is conducted with the Non-Local Density Functional Theory (NLDFT). It is observed that the Type-A⁺⁺ silica gel (granular type) possesses the highest surface area of 863.6 m²/g amongst the three parent silica gels studied. It has a two-maxima or bimodal distribution pattern where the pore diameters are distributed mostly between 10 Å and 30 Å. Water vapor uptake capacity of silica gels are studied with water vapor dosage apparatus and the results show that the Type-A⁺⁺ silica gel exhibits a highest equilibrium uptake at 537 cm³/g. These thermo-physical properties are essential for the design and the numerical simulation of AD cycles.

DOI： 10.1016/j.applthermaleng.2011.09.038

Language：Others   Publishing type：Research paper (other academic)  

Thermo-physical properties, surface characteristics and water vapor uptake capacity are key parameters in the selection of adsorbent for an adsorption desalination (AD) cycle. In the AD cycles, silica gel is used as adsorbent due to their high water vapor uptake capacity, reliability, repeatability and inexpensiveness as compared to other adsorbents. Three types of commercially available silica gels (Type-RD 2560,Type-A5BW and Type-A ) are investigated using a surface characteristic analyzer and their thermo-physical properties are evaluated using several analysis methods. The instrument used in this investigation employs the static volumetric method with liquid Nitrogen at 77 K as the filing fluid. The surface area of each adsorbent is studied using Brunauer-Emmett-Teller (BET) method whilst the pore size distribution (PSD) analysis is conducted with the Non-Local Density Functional Theory (NLDFT). It is observed that the Type-A silica gel (granular type) possesses the highest surface area of 863.6 m /g amongst the three parent silica gels studied. It has a two-maxima or bimodal distribution pattern where the pore diameters are distributed mostly between 10 Å and 30 Å. Water vapor uptake capacity of silica gels are studied with water vapor dosage apparatus and the results show that the Type-A silica gel exhibits a highest equilibrium uptake at 537 cm /g. These thermo-physical properties are essential for the design and the numerical simulation of AD cycles. © 2012 Published by Elsevier Ltd. ++ ++ 2 ++ 3

DOI： 10.1016/j.applthermaleng.2011.09.038

Language：English   Publishing type：Research paper (scientific journal)  

This paper describes the development of a simple hybrid desalination system of a Multi-Effect Distillation (MED) and an adsorption (AD) cycle operating at sub-atmospheric pressures and temperatures. By hybridizing the conventional MED with an AD cycle, there is a symbiotic enhancement of performances of both cycles. The performance enhancement is attributed to (i) the cascade of adsorbent's regeneration temperature and this extended the usage of thermal energy emanating from the brine heater and (ii) the vapor extraction from the last MED stage by AD cycle which provides the effect of lowering saturation temperatures of all MED stages to the extent of 5°C, resulting in scavenging of heat leaks into the MED stages from the ambient. The combined effects of the hybrid cycles increase the water production capacity of the desalination plant by nearly twofolds.In this paper, we demonstrate a hybrid cycle by simulating an 8-stage MED cycle which is coupled to an adsorption cycle for direct vapor extraction from the last MED stage. The sorption properties of silica gel is utilized (acting as a mechanical vapor compressor) to reduce the saturation temperatures of MED stages. The modeling utilizes the adsorption isotherms and kinetics of the adsorbent. +. adsorbate (silica-gel. +. water) pair along with the governing equations of mass, energy and concentration. For a 8-stage MED and AD cycles operating at assorted temperatures of 65-90°C, the results show that the water production rate increases from 60% to twofolds when compared to the MED alone. The performance ratio (PR) and gain output ratio (GOR) also improve significantly.

DOI： 10.1016/j.apenergy.2012.12.007

Language：Others   Publishing type：Research paper (scientific journal)  

This paper presents a solar-assisted direct contact membrane distillation (DCMD) system with novel energy recovery concepts for a continuous 24-h-a-day operation. A temperature modulating scheme is introduced to the solar-thermal system that supplies feed seawater to the DCMD modules. This scheme attenuates extreme temperature fluctuations of the feed water by storing the collected energy during solar-peak hours and reutilizing it throughout the day. Thus, the energy savings is realized yet the feed seawater temperature is maintained within the desired range. Additionally, the system employs heat recovery from the permeate and brine streams to the feed seawater. The simulations for such a system with a shell-and-tube type DCMD modules are carried out to examine the spatial property variations and the sensitivity of system performance (i.e., transmembrane pressure, permeate flux and performance ratio) to the operating conditions (inlet temperature and flow rate) and the fiber dimensions (fiber length and packing density). It is found that there are trade-offs between mean permeate flux and performance ratio with respect to permeate inlet temperature and flow rate and between total distillate production and performance ratio with respect to packing density. For the solar-assisted DCMD system having evacuated-tube collectors of 3360m with 160m seawater storage tanks and 50 DCMD modules, the annual solar fraction and the collector efficiency are found to be 77&#37; and 53&#37;, respectively, whilst the overall permeate production capacity is 31m /day. The overall specific thermal energy consumption of the DCMD system with heat recovery is found to be 436kWh/m and it is about 43&#37; lower as compared to the system without heat recovery. It is observed that the specific thermal energy consumption decreases significantly by 55&#37; with increased collector area from 1983m to 3360m whereas the specific electrical energy consumption increases slightly by 16&#37;. © 2012 Elsevier B.V. 2 3 3 3 2 2

DOI： 10.1016/j.memsci.2012.10.008

Language：Others   Publishing type：Research paper (scientific journal)  

Low temperature waste heat-driven adsorption desalination (AD) cycles offer high potential as one of the most economically viable and environmental-friendly desalination methods. This article presents the development of an advanced adsorption desalination cycle that employs internal heat recovery between the evaporator and the condenser, utilizing an encapsulated evaporator-condenser unit for effective heat transfer. A simulation model has been developed based on the actual sorption characteristics of the adsorbent-adsorbate pair, energy and mass balances applied to the components of the AD cycle. With an integrated design, the temperature in the evaporator and the vapor pressurization of the adsorber are raised due to the direct heat recovery from the condenser, resulting in the higher water production rates, typically improved by as much as three folds of the conventional AD cycle. In addition, the integrated design eliminates two pumps, namely, the condenser cooling water and the chilled water pumps, lowering the overall electricity consumption. The performance of the cycle is analyzed at assorted heat source and cooling water temperatures, and different cycle times as well as the transient heat transfer coefficients of the evaporation and condensation. © 2012 Elsevier B.V.

DOI： 10.1016/j.desal.2012.04.021

Language：Others   Publishing type：Research paper (scientific journal)  

Desalination, other than the natural water cycle, is hailed as the panacea to alleviate the problems of fresh water shortage in many water stressed countries. However, the main drawback of conventional desalination methods is that they are energy intensive. In many instances, they consumed electricity, chemicals for pre- and post-treatment of water. For each kWh of energy consumed, there is an unavoidable emission of Carbon Dioxide (CO ) at the power stations as well as the discharge of chemically-laden brine into the environment. Thus, there is a motivation to find new direction or methods of desalination that consumed less chemicals, thermal energy and electricity.This paper describes an emerging and yet low cost method of desalination that employs only low-temperature waste heat, which is available in abundance from either the renewable energy sources or exhaust of industrial processes. With only one heat input, the Adsorption Desalination (AD) cycle produces two useful effects, i.e., high grade potable water and cooling. In this article, a brief literature review, the theoretical framework for adsorption thermodynamics, a lumped-parameter model and the experimental tests for a wide range of operational conditions on the basic and the hybrid AD cycles are discussed. Predictions from the model are validated with measured performances from two pilot plants, i.e., a basic AD and the advanced AD cycles. The energetic efficiency of AD cycles has been compared against the conventional desalination methods. Owing to the unique features of AD cycle, i.e., the simultaneous production of dual useful effects, it is proposed that the life cycle cost (LCC) of AD is evaluated against the LCC of combined machines that are needed to deliver the same quantities of useful effects using a unified unit of &#36;/MWh. In closing, an ideal desalination system with zero emission of CO is presented where geo-thermal heat is employed for powering a temperature-cascaded cogeneration plant. © 2012 Elsevier B.V. 2 2

DOI： 10.1016/j.desal.2012.07.030

Language：English   Publishing type：Research paper (scientific journal)  

This paper discusses the performance of a temperature-cascaded cogeneration plant (TCCP), equipped with an efficient waste heat recovery system. The TCCP, also called a cogeneration system, produces four types of useful energy-namely, (i) electricity, (ii) steam, (iii) cooling and (iv) dehumidification-by utilizing single fuel source. The TCCP comprises a Capstone C-30 micro-turbine that generates nominal capacity of 26 kW of electricity, a compact and efficient waste heat recovery system and a host of waste-heat-activated devices, namely (i) a steam generator, (ii) an absorption chiller, (iii) an adsorption chiller and (iv) a multi-bed desiccant dehumidifier. The performance analysis was conducted under different operation conditions such as different exhaust gas temperatures. It was observed that energy utilization factor could be as high as 70% while fuel energy saving ratio was found to be 28%.

DOI： 10.1080/19443994.2012.694232

Language：English   Publishing type：Research paper (scientific journal)  

This paper presents the performance investigation of a temperature cascaded cogeneration plant, shortly in TCCP, equipped with an efficient waste heat recovery system. The TCCP or cogeneration system produces four types of useful energy namely (i) electricity, (ii) steam, (iii) cooling, and (iv) dehumidification and distilled water by utilizing single energy source. The TCCP comprises a Capstone C30 micro-turbine that generates nominal capacity of 26 kW of electricity, a compact and efficient waste heat recovery system and a host of waste heatactivated devices namely (i) a steam generator, (ii) an absorption chiller, (iii) an adsorption desalination system, and (iv) a multi-bed desiccant dehumidifier. The analysis is performed under different operation conditions such as heat source temperatures, flow rates of heat transfer fluids and chilled water inlet temperatures. The only single heat source for TCCP is obtained from exhaust gas of micro-turbine and it is channeled to a series of waste heat recovery heat exchangers to steam and hot water at different temperatures. Hot water produced by such a compact heat exchangers is the driving heat source to produce steam of 15 kg/h, cooling of 2 Rton, dehumidification of 2 Rton, and distilled water of 0.7 m³/day. A set of experiments, both part load and full load, of micro-turbine is conducted to examine the electricity generation and the exhaust gas temperature. It is observed that energy utilization factor could achieve as high as 70% while fuel energy saving ratio is found to be 28%.

DOI： 10.1080/19443994.2012.714580

Language：English   Publishing type：Research paper (scientific journal)  

Energy or heat recovery schemes are keys for the performance improvement of any heat-activated cycles such as the absorption and adsorption cycles. We present two innovative heat recovery schemes between the condensing and evaporating units of an adsorption desalination (AD) cycle. By recovering the latent heat of condenser and dumping it into the evaporative process of the evaporator, it elevates the evaporating temperature and hence the adsorption pressure seen by the adsorbent. From isotherms, this has an effect of increasing the vapour uptake. In the proposed configurations, one approach is simply to have a run-about water circuit between the condenser and the evaporator and a pump is used to achieve the water circulation. This run-around circuit is a practical method for retrofitting purposes. The second method is targeted towards a new AD cycle where an encapsulated condenser-evaporator unit is employed. The heat transfer between the condensing and evaporative vapour is almost immediate and the processes occur in a fully integrated vessel, thereby minimizing the heat transfer resistances of heat exchangers.

DOI： 10.1080/19443994.2012.693659

Language：English   Publishing type：Research paper (scientific journal)  

This paper presents a solar-assisted direct contact membrane distillation (DCMD) system with novel energy recovery concepts for a continuous 24-h-a-day operation. A temperature modulating scheme is introduced to the solar-thermal system that supplies feed seawater to the DCMD modules. This scheme attenuates extreme temperature fluctuations of the feed water by storing the collected energy during solar-peak hours and reutilizing it throughout the day. Thus, the energy savings is realized yet the feed seawater temperature is maintained within the desired range. Additionally, the system employs heat recovery from the permeate and brine streams to the feed seawater. The simulations for such a system with a shell-and-tube type DCMD modules are carried out to examine the spatial property variations and the sensitivity of system performance (i.e., transmembrane pressure, permeate flux and performance ratio) to the operating conditions (inlet temperature and flow rate) and the fiber dimensions (fiber length and packing density). It is found that there are trade-offs between mean permeate flux and performance ratio with respect to permeate inlet temperature and flow rate and between total distillate production and performance ratio with respect to packing density. For the solar-assisted DCMD system having evacuated-tube collectors of 3360m² with 160m³ seawater storage tanks and 50 DCMD modules, the annual solar fraction and the collector efficiency are found to be 77% and 53%, respectively, whilst the overall permeate production capacity is 31m³/day. The overall specific thermal energy consumption of the DCMD system with heat recovery is found to be 436kWh/m³ and it is about 43% lower as compared to the system without heat recovery. It is observed that the specific thermal energy consumption decreases significantly by 55% with increased collector area from 1983m² to 3360m² whereas the specific electrical energy consumption increases slightly by 16%.

DOI： 10.1016/j.memsci.2012.10.008

Language：English   Publishing type：Research paper (scientific journal)  

We present a simulation model for the transient behavior of solar-assisted seawater desalination plant that employs the evacuated-tube collectors in conjunction with a multieffect distillation plant of nominal water production capacity of 16m³/day. This configuration has been selected due to merits in terms of environment-friendliness and energy efficiency. The solar-assisted multi-effect distillation system comprises 849 m² of evacuated-tube collectors, 280 m³ water storage tanks, auxiliary heater, and six effects and a condenser. The present analysis employs a baseline configuration, namely; (i) the local solar insolation input (Jeddah, Saudi Arabia), (ii) a coolant flow rate through the headers of collector based on ASHRAE standards, (iii) a heating water demand, and (iv) the augmentation of water temperature by auxiliary when the supply temperature from the solar tank drops below the set point. It is observed that the annual collector efficiency and solar fraction decrease from 57.3 to 54.8% and from 49.4 to 36.7%, respectively, with an increase in the heating water temperature from 80 to 90 °C. The overall water production rate and the performance ratio increase slightly from 0.18 to 0.21 kg/s and from 4.11 to 4.13, respectively.

DOI： 10.1080/19443994.2012.695044

Language：English   Publishing type：Research paper (scientific journal)  

Low temperature waste heat-driven adsorption desalination (AD) cycles offer high potential as one of the most economically viable and environmental-friendly desalination methods. This article presents the development of an advanced adsorption desalination cycle that employs internal heat recovery between the evaporator and the condenser, utilizing an encapsulated evaporator-condenser unit for effective heat transfer. A simulation model has been developed based on the actual sorption characteristics of the adsorbent-adsorbate pair, energy and mass balances applied to the components of the AD cycle. With an integrated design, the temperature in the evaporator and the vapor pressurization of the adsorber are raised due to the direct heat recovery from the condenser, resulting in the higher water production rates, typically improved by as much as three folds of the conventional AD cycle. In addition, the integrated design eliminates two pumps, namely, the condenser cooling water and the chilled water pumps, lowering the overall electricity consumption. The performance of the cycle is analyzed at assorted heat source and cooling water temperatures, and different cycle times as well as the transient heat transfer coefficients of the evaporation and condensation.

DOI： 10.1016/j.desal.2012.04.021

Language：English   Publishing type：Research paper (scientific journal)  

This paper presents the performance testing of Zeolite adsorption cooling system driven by low grade waste heat source extracted from prime mover's exhaust, power plant's exhaust and the solar energy. The adsorbent FAM Z01 is used as an adsorbent in the adsorption chiller facility. Owing to its large equilibrium pore volume, it has the high affinity for the water vapor adsorbate. The key advantages of the Zeolite adsorption cooling system are: (i) it has no moving parts rendering less maintenance, (ii) the energy efficient means of cooling by the adsorption process with a low temperature heat source, (iii) the use of vapor pipes are replaced by self actuating vapor valves rendering smaller footprint area and (iv) it is environmental friendly with low carbon footprint. The experimental investigations were carried out for Zeolite adsorption chiller at different key operating conditions namely (i) heat source temperature, (ii) the cycle time and (iii) the heat recovery time. It is investigated that performance of coefficient (COP) of this system could be as high as 0.48 while the waste heat source temperature is applicable as low as 55 °C.

DOI： 10.1016/j.apenergy.2012.08.005

Language：English   Publishing type：Research paper (scientific journal)  

This paper discusses the analysis of an adsorption (AD) chiller using system entropy generation as a thermodynamic framework for evaluating total dissipative losses that occurred in a batch-operated AD cycle. The study focuses on an adsorption cycle operating at heat source temperatures ranging from 60 to 85 °C, whilst the chilled water inlet temperature is fixed at 12.5 °C,-a temperature of chilled water deemed useful for dehumidification and cooling. The total entropy generation model examines the processes of key components of the AD chiller such as the heat and mass transfer, flushing and de-superheating of liquid refrigerant. The following key findings are observed: (i) The cycle entropy generation increases with the increase in the heat source temperature (10.8 to 46.2 W/K) and the largest share of entropy generation or rate of energy dissipation occurs at the adsorption process, (ii) the second highest energy rate dissipation is the desorption process, (iii) the remaining energy dissipation rates are the evaporation and condensation processes, respectively. Some of the noteworthy highlights from the study are the inevitable but significant dissipative losses found in switching processes of adsorption-desorption and vice versa, as well as the de-superheating of warm condensate that is refluxed at non-thermal equilibrium conditions from the condenser to the evaporator for the completion of the refrigeration cycle.

DOI： 10.1016/j.ijheatmasstransfer.2012.12.055

Language：English   Publishing type：Research paper (scientific journal)  

Desalination, other than the natural water cycle, is hailed as the panacea to alleviate the problems of fresh water shortage in many water stressed countries. However, the main drawback of conventional desalination methods is that they are energy intensive. In many instances, they consumed electricity, chemicals for pre- and post-treatment of water. For each kWh of energy consumed, there is an unavoidable emission of Carbon Dioxide (CO₂) at the power stations as well as the discharge of chemically-laden brine into the environment. Thus, there is a motivation to find new direction or methods of desalination that consumed less chemicals, thermal energy and electricity.This paper describes an emerging and yet low cost method of desalination that employs only low-temperature waste heat, which is available in abundance from either the renewable energy sources or exhaust of industrial processes. With only one heat input, the Adsorption Desalination (AD) cycle produces two useful effects, i.e., high grade potable water and cooling. In this article, a brief literature review, the theoretical framework for adsorption thermodynamics, a lumped-parameter model and the experimental tests for a wide range of operational conditions on the basic and the hybrid AD cycles are discussed. Predictions from the model are validated with measured performances from two pilot plants, i.e., a basic AD and the advanced AD cycles. The energetic efficiency of AD cycles has been compared against the conventional desalination methods. Owing to the unique features of AD cycle, i.e., the simultaneous production of dual useful effects, it is proposed that the life cycle cost (LCC) of AD is evaluated against the LCC of combined machines that are needed to deliver the same quantities of useful effects using a unified unit of $/MWh. In closing, an ideal desalination system with zero emission of CO₂ is presented where geo-thermal heat is employed for powering a temperature-cascaded cogeneration plant.

DOI： 10.1016/j.desal.2012.07.030

Language：English   Publishing type：Research paper (other academic)  

This paper presents an investigation of heat transfer correlation in a falling-film evaporator working with saline water at sub-atmospheric pressures. The experiments are conducted at different salinity levels ranging from 15000 to 90000 ppm, and the pressures were maintained between 0.92 to 2.81 kPa (corresponds to saturation temperatures of 5.9 - 23 ⁰C). The effect of salinity, saturation pressures and chilled water temperatures on the heat transfer coefficient are accounted in the modified film evaporation correlations. The results are fitted to the Han & Fletcher's and Chun & Seban's falling-film correlations which are used in desalination industry. We modify the said correlations by adding salinity and saturation temperature corrections with respective indices to give a better agreement to our measured data.

DOI： 10.1063/1.4704324

Language：English   Publishing type：Research paper (other academic)  

This paper presents the performance investigation of a cogeneration plant equipped with an efficient waste heat recovery system. The proposed cogeneration system produces four types of useful energy namely: (i) electricity, (ii) steam, (iii) cooling and (iv) dehumidification. The proposed plant comprises a Capstone C30 micro-turbine which generates 24 kW of electricity, a compact and efficient waste heat recovery system and a host of waste heat activated devices namely (i) a steam generator, (ii) an absorption chiller, (iii) an adsorption chiller and (iv) a multi-bed desiccant dehumidifier. The numerical analysis for the host of waste heat recovery system and thermally activated devices using FORTRAN power station linked to powerful IMSL library is performed to investigate the performance of the overall system. A set of experiments, both part load and full load, of micro-turbine is conducted to examine the electricity generation and the exhaust gas temperature. It is observed that energy utilization factor (EUF) could achieve as high as 70% while Fuel Energy Saving Ratio (FESR) is found to be 28%.

DOI： 10.1063/1.4704299

Language：English  

DOI： 10.1002/9781118347737.ch5

Language：Others   Publishing type：Research paper (scientific journal)  

We present a practical tool that employs entropy generation minimization (EGM) approach for an in-depth performance evaluation of a co-generation plant with a temperature-cascaded concept. Co-generation plant produces useful effect production sequentially, i.e., (i) electricity from the micro-turbines, (ii) low pressure steam at 250 °C or about 8-10 bars, (iii) cooling capacity of 4 refrigeration tones (Rtons) and (iv) dehumidification of outdoor air for air conditioned space. The main objective is to configure the most efficient configuration of producing power and heat. We employed entropy generation minimization (EGM) which reflects to minimize the dissipative losses and maximize the cycle efficiency of the individual thermally activated systems. The minimization of dissipative losses or EGM is performed in two steps namely, (i) adjusting heat source temperatures for the heat-fired cycles and (ii) the use of Genetic Algorithm (GA), to seek out the sensitivity of heat transfer areas, flow rates of working fluids, inlet temperatures of heat sources and coolant, etc., over the anticipated range of operation to achieve maximum efficiency. With EGM equipped with GA, we verified that the local minimization of entropy generation individually at each of the heat-activated processes would lead to the maximum efficiency of the system. © 2012.

DOI： 10.1016/j.energy.2012.07.062

Language：Others  

DOI： 10.1002/9781118347737.ch5

Language：English   Publishing type：Research paper (scientific journal)  

We present the experimental investigation on the performance of multi-bed desiccant dehumidification system (MBDD) using a thermodynamic framework with an entropy generation analysis. The cyclic steady state performance of adsorption-desorption processes at the assorted heat source temperatures, and typical ambient humidity conditions was carried out. MBDD unit uses type-RD silica gel pore surface area with of 720 m ²/g. It has a nominal diameter range of 0.4 to 0. 7 mm. The key advantages of MBDD are: (i) it has no moving parts rendering less maintenance, (ii) energy-efficient means of dehumidification by adsorption process with low temperature heat source as compared to the conventional methods, (iii) although it is a pecked bed desiccant, a laminar chamber is employed by arranging the V-shaped configuration of heat exchangers and (iv) it is environmental friendly with the low-carbon footprint. Entropy generation analysis was performed at the assorted heat source temperatures to investigate the performance of MBDD. By conducting the entropy minimization, it is now able to locate the optimal operating conditions of the system while the specific entropy generation is found to be minimal. This analysis shows that the minimization of entropy generation in the dehumidification cycle leads to the maximization of COP in the MBDD and thus, higher delivery of useful effects at the same input resources.

DOI： 10.1016/j.applthermaleng.2012.01.041

Language：Others   Publishing type：Research paper (scientific journal)  

We present the experimental investigation on the performance of multi-bed desiccant dehumidification system (MBDD) using a thermodynamic framework with an entropy generation analysis. The cyclic steady state performance of adsorption-desorption processes at the assorted heat source temperatures, and typical ambient humidity conditions was carried out. MBDD unit uses type-RD silica gel pore surface area with of 720 m /g. It has a nominal diameter range of 0.4 to 0. 7 mm. The key advantages of MBDD are: (i) it has no moving parts rendering less maintenance, (ii) energy-efficient means of dehumidification by adsorption process with low temperature heat source as compared to the conventional methods, (iii) although it is a pecked bed desiccant, a laminar chamber is employed by arranging the V-shaped configuration of heat exchangers and (iv) it is environmental friendly with the low-carbon footprint. Entropy generation analysis was performed at the assorted heat source temperatures to investigate the performance of MBDD. By conducting the entropy minimization, it is now able to locate the optimal operating conditions of the system while the specific entropy generation is found to be minimal. This analysis shows that the minimization of entropy generation in the dehumidification cycle leads to the maximization of COP in the MBDD and thus, higher delivery of useful effects at the same input resources. © 2011 Elsevier Ltd. All rights reserved. 2

DOI： 10.1016/j.applthermaleng.2012.01.041

Language：English   Publishing type：Research paper (scientific journal)  

This article presents the performance analysis of adsorption cooling, shortly AD, system using a thermodynamic framework with an entropy generation analysis. The model captures the transient and the cyclic steady-state performances of the adsorption-desorption cycles operating under assorted heat source temperatures. Type-RD silica gel, with a pore surface area of 720 m2/g and diameters 0.4-0.7 mm, is used as an adsorbent and its high affinity for thewater vapour adsorbate gives a high equilibrium uptake. The key advantages of the AD are (a) it has no moving parts rendering less maintenance and (b) the energy efficient means of cooling by the adsorption process with a low-temperature heat source and (c) it is environmental friendly with low carbon footprint. By incorporating the genetic algorithm onto the entropy minimization technique, it is possible to locate the optimal system performance point or the global minima with respect to entropy generation using the system parameters such as coolant and heat source water temperatures, heat transfer areas, etc. The system analysis shows that the minimization of entropy generation in the AD cycle leads to the maximization of the coefficient of performance and this translates into a higher delivery of useful cooling effects at the particular input resource temperature.

DOI： 10.1177/0954408911416439

Language：Others   Publishing type：Research paper (scientific journal)  

The main objective of this study is to optimize the long-term performance of an existing active-indirect solar hot water plant (SHWP), which supplies hot water at 65 °C for use in a flight kitchen, using a micro genetic algorithm in conjunction with a relatively detailed model of each component in the plant and solar radiation model based on the measured data. The performance of SHWP at Changi International Airport Services (CIASs), Singapore, is studied for better payback period using the monthly average hourly diffuse and beam radiations and ambient temperature data. The data input for solar radiation model is obtained from the Singapore Meteorological Service (SMS), and these data have been compared with long-term average data of NASA (surface meteorology and solar energy or SSE). The comparison shows a good agreement between the predicted and measured hourly-averaged, horizontal global radiation. The SHWP at CIAS, which comprises 1200m of evacuated-tube collectors, 50m water storage tanks and a gas-fired auxiliary boiler, is first analyzed using a baseline configuration, i.e., (i) the local solar insolation input, (ii) a coolant flow rate through the headers of collector based on ASHRAE standards, (iii) a thermal load demand pattern amounting to 100m /day, and (iv) the augmentation of water temperature by auxiliary when the supply temperature from solar tank drops below the set point. A comparison between the baseline configuration and the measured performance of CIAS plant gives reasonably good validation of the simulation code. Optimization is further carried out for the following parameters, namely; (i) total collector area of the plant, (ii) storage volume, and (iii) three daily thermal demands. These studies are performed for both the CIAS plant and a slightly modified plant where the hot water supply to the load is adjusted constant at times when the water temperature from tank may exceed the set temperature. It is found that the latter configuration has better thermal and economic performances over the conventional design. © 2012. 2 3 3

DOI： 10.1016/j.solener.2012.01.030

Language：Others   Publishing type：Research paper (scientific journal)  

This article presents the performance analysis of a waste heat-driven adsorption cycle. With the implementation of adsorption-desorption phenomena, the cycle simultaneously produces cooling energy and high-grade potable water. A mathematical model is developed using isotherm characteristics of the adsorbent/adsorbate pair (silica gel and water), energy and mass balances for the each component of the cycle. The cycle is analyzed using key performance parameters namely (i) specific cooling power (SCP), (ii) specific daily water production (SDWP), (iii) the coefficient of performance (COP) and (iv) the overall conversion ratio (OCR). The numerical results of the adsorption cycle are validated using experimental data. The parametric analysis using different hot and chilled water temperatures are reported. At 85°C hot water inlet temperature, the cycle generates 3.6 m of potable water and 23 Rton of cooling at the produced chilled water temperature of 10°C. © 2012 Elsevier Ltd and IIR. All rights reserved. 3

DOI： 10.1016/j.ijrefrig.2011.01.008

Language：Others   Publishing type：Research paper (scientific journal)  

This article presents the performance analysis of adsorption cooling, shortly AD, system using a thermodynamic framework with an entropy generation analysis. The model captures the transient and the cyclic steady-state performances of the adsorption-desorption cycles operating under assorted heat source temperatures. Type-RD silica gel, with a pore surface area of 720 m2/g and diameters 0.4-0.7 mm, is used as an adsorbent and its high affinity for thewater vapour adsorbate gives a high equilibrium uptake. The key advantages of the AD are (a) it has no moving parts rendering less maintenance and (b) the energy efficient means of cooling by the adsorption process with a low-temperature heat source and (c) it is environmental friendly with low carbon footprint. By incorporating the genetic algorithm onto the entropy minimization technique, it is possible to locate the optimal system performance point or the global minima with respect to entropy generation using the system parameters such as coolant and heat source water temperatures, heat transfer areas, etc. The system analysis shows that the minimization of entropy generation in the AD cycle leads to the maximization of the coefficient of performance and this translates into a higher delivery of useful cooling effects at the particular input resource temperature. © Authors 2011.

DOI： 10.1177/0954408911416439

Language：English   Publishing type：Research paper (scientific journal)  

The main objective of this study is to optimize the long-term performance of an existing active-indirect solar hot water plant (SHWP), which supplies hot water at 65 °C for use in a flight kitchen, using a micro genetic algorithm in conjunction with a relatively detailed model of each component in the plant and solar radiation model based on the measured data. The performance of SHWP at Changi International Airport Services (CIASs), Singapore, is studied for better payback period using the monthly average hourly diffuse and beam radiations and ambient temperature data. The data input for solar radiation model is obtained from the Singapore Meteorological Service (SMS), and these data have been compared with long-term average data of NASA (surface meteorology and solar energy or SSE). The comparison shows a good agreement between the predicted and measured hourly-averaged, horizontal global radiation. The SHWP at CIAS, which comprises 1200m ² of evacuated-tube collectors, 50m ³ water storage tanks and a gas-fired auxiliary boiler, is first analyzed using a baseline configuration, i.e., (i) the local solar insolation input, (ii) a coolant flow rate through the headers of collector based on ASHRAE standards, (iii) a thermal load demand pattern amounting to 100m ³/day, and (iv) the augmentation of water temperature by auxiliary when the supply temperature from solar tank drops below the set point. A comparison between the baseline configuration and the measured performance of CIAS plant gives reasonably good validation of the simulation code. Optimization is further carried out for the following parameters, namely; (i) total collector area of the plant, (ii) storage volume, and (iii) three daily thermal demands. These studies are performed for both the CIAS plant and a slightly modified plant where the hot water supply to the load is adjusted constant at times when the water temperature from tank may exceed the set temperature. It is found that the latter configuration has better thermal and economic performances over the conventional design.

DOI： 10.1016/j.solener.2012.01.030

Language：English   Publishing type：Research paper (scientific journal)  

This article presents the performance analysis of a waste heat-driven adsorption cycle. With the implementation of adsorption-desorption phenomena, the cycle simultaneously produces cooling energy and high-grade potable water. A mathematical model is developed using isotherm characteristics of the adsorbent/adsorbate pair (silica gel and water), energy and mass balances for the each component of the cycle. The cycle is analyzed using key performance parameters namely (i) specific cooling power (SCP), (ii) specific daily water production (SDWP), (iii) the coefficient of performance (COP) and (iv) the overall conversion ratio (OCR). The numerical results of the adsorption cycle are validated using experimental data. The parametric analysis using different hot and chilled water temperatures are reported. At 85°C hot water inlet temperature, the cycle generates 3.6 m
³
of potable water and 23 Rton of cooling at the produced chilled water temperature of 10°C.

DOI： 10.1016/j.ijrefrig.2011.01.008

Language：English   Publishing type：Research paper (scientific journal)  

We present a practical tool that employs entropy generation minimization (EGM) approach for an in-depth performance evaluation of a co-generation plant with a temperature-cascaded concept. Co-generation plant produces useful effect production sequentially, i.e., (i) electricity from the micro-turbines, (ii) low pressure steam at 250 °C or about 8-10 bars, (iii) cooling capacity of 4 refrigeration tones (Rtons) and (iv) dehumidification of outdoor air for air conditioned space. The main objective is to configure the most efficient configuration of producing power and heat. We employed entropy generation minimization (EGM) which reflects to minimize the dissipative losses and maximize the cycle efficiency of the individual thermally activated systems. The minimization of dissipative losses or EGM is performed in two steps namely, (i) adjusting heat source temperatures for the heat-fired cycles and (ii) the use of Genetic Algorithm (GA), to seek out the sensitivity of heat transfer areas, flow rates of working fluids, inlet temperatures of heat sources and coolant, etc., over the anticipated range of operation to achieve maximum efficiency. With EGM equipped with GA, we verified that the local minimization of entropy generation individually at each of the heat-activated processes would lead to the maximum efficiency of the system.

DOI： 10.1016/j.energy.2012.07.062

Language：English   Publishing type：Research paper (scientific journal)  

This paper presents performance analysis of absorption refrigeration system (ARS) using an entropy generation analysis. A numerical model predicts the performance of absorption cycle operating under transient conditions along with the entropy generation computation at assorted heat source temperatures, and it captures also the dynamic changes of lithium bromide solution properties such as concentration, density, vapor pressure and overall heat transfer coefficients. An optimization tool, namely the genetic algorithm (GA), is used as to locate the system minima for all defined domain of heat source and cooling water temperatures. The analysis shows that minimization of entropy generation the in absorption cycle leads to the maximization of the COP.

DOI： 10.1016/j.applthermaleng.2011.04.004

Language：Others   Publishing type：Research paper (scientific journal)  

This paper presents performance analysis of absorption refrigeration system (ARS) using an entropy generation analysis. A numerical model predicts the performance of absorption cycle operating under transient conditions along with the entropy generation computation at assorted heat source temperatures, and it captures also the dynamic changes of lithium bromide solution properties such as concentration, density, vapor pressure and overall heat transfer coefficients. An optimization tool, namely the genetic algorithm (GA), is used as to locate the system minima for all defined domain of heat source and cooling water temperatures. The analysis shows that minimization of entropy generation the in absorption cycle leads to the maximization of the COP. © 2011 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.applthermaleng.2011.04.004

Language：Others   Publishing type：Research paper (scientific journal)  

In this study, a physical separation method using a flotation system employing microbubbles was designed and tested as an alternative to conventional dissolved air flotation (DAF) systems. The proposed system is an environmentally friendly microbubble treatment using air, ozone, and CO gases and requiring virtually no chemicals. Three case studies have been investigated in this paper which verify the efficacy of microbubbles in treating wastewater, namely, (i) treatment of oily wastewater derived from cleaning the hull of a tanker ship, (ii) treatment of hotel laundry water, and (iii) treatment of fish pond water. After microbubble treatment, the treated water was determined to be suitable for recycling or discharge to the environment. The test results show that both air and ozone microbubble in wastewater treatments achieved large reductions in TSS, BOD and COD in the tested samples. © 2011 Desalination Publications. 2

DOI： 10.5004/dwt.2011.1217

Language：English   Publishing type：Research paper (scientific journal)  

This letter proposes and presents a thermodynamic formulation to calculate the energetic performances of an adsorption cooler as a function of pore widths and volumes of solid adsorbents. The simulated results in terms of the coefficient of performance are validated with experimental data. It is found from the present analysis that the performance of an adsorption cooling device is influenced mainly by the physical characteristics of solid adsorbents, and the characteristics energy between the adsorbent-adsorbate systems. The present study confirms that there exists a special type of silica gel having optimal physical characteristics that allows us to obtain the best performance.

DOI： 10.1063/1.3592260

Language：Others   Publishing type：Research paper (scientific journal)  

This letter proposes and presents a thermodynamic formulation to calculate the energetic performances of an adsorption cooler as a function of pore widths and volumes of solid adsorbents. The simulated results in terms of the coefficient of performance are validated with experimental data. It is found from the present analysis that the performance of an adsorption cooling device is influenced mainly by the physical characteristics of solid adsorbents, and the characteristics energy between the adsorbent-adsorbate systems. The present study confirms that there exists a special type of silica gel having optimal physical characteristics that allows us to obtain the best performance. © 2011 American Institute of Physics.

DOI： 10.1063/1.3592260

Language：English   Publishing type：Research paper (scientific journal)  

This article presents an experimental approach for the determination of the adsorption isotherms of methane on activated carbon that is essential for methane storage purposes. The experiments incorporated a constant-volume- variable-pressure (CVVP) apparatus, and two types of activated carbon have been investigated, namely, activated carbon derived from the low rank coal of the East of Kalimantan, Indonesia, and a Carbotech activated carbon. The isotherm results which cover temperatures from (300 to 318) K and pressures up to 3.5 MPa are analyzed using the Langmuir, Tóth, and Dubinin-Astakhov (D-A) isotherm models. The heat of adsorption for the single component methane-activated carbon system, which is concentration- and temperature-dependent, is determined from the measured isotherm data.

DOI： 10.1021/je100495w

Language：Others   Publishing type：Research paper (scientific journal)  

This article presents an experimental approach for the determination of the adsorption isotherms of methane on activated carbon that is essential for methane storage purposes. The experiments incorporated a constant-volume- variable-pressure (CVVP) apparatus, and two types of activated carbon have been investigated, namely, activated carbon derived from the low rank coal of the East of Kalimantan, Indonesia, and a Carbotech activated carbon. The isotherm results which cover temperatures from (300 to 318) K and pressures up to 3.5 MPa are analyzed using the Langmuir, Tóth, and Dubinin-Astakhov (D-A) isotherm models. The heat of adsorption for the single component methane-activated carbon system, which is concentration- and temperature-dependent, is determined from the measured isotherm data. © 2011 American Chemical Society.

DOI： 10.1021/je100495w

Language：English   Publishing type：Research paper (scientific journal)  

In this study, a physical separation method using a flotation system employing microbubbles was designed and tested as an alternative to conventional dissolved air flotation (DAF) systems. The proposed system is an environmentally friendly microbubble treatment using air, ozone, and CO₂ gases and requiring virtually no chemicals. Three case studies have been investigated in this paper which verify the efficacy of microbubbles in treating wastewater, namely, (i) treatment of oily wastewater derived from cleaning the hull of a tanker ship, (ii) treatment of hotel laundry water, and (iii) treatment of fish pond water. After microbubble treatment, the treated water was determined to be suitable for recycling or discharge to the environment. The test results show that both air and ozone microbubble in wastewater treatments achieved large reductions in TSS, BOD and COD in the tested samples.

DOI： 10.5004/dwt.2011.1217

Language：Others   Publishing type：Research paper (scientific journal)  

This paper presents the results of an investigation on the efficacy of a silica gel-water based advanced adsorption desalination (AD) cycle with internal heat recovery between the condenser and the evaporator. A mathematical model of the AD cycle was developed and the performance data were compared with the experimental results. The advanced AD cycle is able to produce the specific daily water production (SDWP) of 9.24 m /tonne of silica gel per day at 70 °C hot water inlet temperature while the corresponding performance ratio (PR) is comparatively high at 0.77. It is found that the cycle can be operational at 50 °C hot water temperature with SDWP 4.3. The SDWP of the advanced cycle is almost twice that of the conventional AD cycle. © 2010 Elsevier Ltd. All rights reserved. 3

DOI： 10.1016/j.ijheatmasstransfer.2010.09.065

Language：English   Publishing type：Research paper (scientific journal)  

This paper presents the results of an investigation on the efficacy of a silica gel-water based advanced adsorption desalination (AD) cycle with internal heat recovery between the condenser and the evaporator. A mathematical model of the AD cycle was developed and the performance data were compared with the experimental results. The advanced AD cycle is able to produce the specific daily water production (SDWP) of 9.24 m³/tonne of silica gel per day at 70 °C hot water inlet temperature while the corresponding performance ratio (PR) is comparatively high at 0.77. It is found that the cycle can be operational at 50 °C hot water temperature with SDWP 4.3. The SDWP of the advanced cycle is almost twice that of the conventional AD cycle.

DOI： 10.1016/j.ijheatmasstransfer.2010.09.065

Language：English   Publishing type：Research paper (other academic)  

We have developed a thermodynamic framework to calculate adsorption cooling cum desalination cycle performances as a function of pore widths and pore volumes of highly porous adsorbents, which are formulated from the rigor of thermodynamic property surfaces of adsorbent-adsorbate system and the adsorption interaction potential between them. Employing the proposed formulations, the coefficient of performance (COP) and overall performance ratio (OPR) of adsorption cycle are computed for various pore widths of solid adsorbents. These results are compared with experimental data for verifying the proposed thermodynamic formulations. It is found from the present analysis that the COP and OPR of adsorption cooling cum desalination cycle is influenced by (i) the physical characteristics of adsorbents, (ii) characteristics energy and (iii) the surface-structural heterogeneity factor of adsorbent-water system. The present study confirms that there exists a special type of adsorbents having optimal physical characteristics that allows us to obtain the best performance.

Language：Others   Publishing type：Research paper (scientific journal)  

This paper presents the thermo-economic analysis of the adsorption desalination (AD) cycle that is driven by low-temperature waste heat from exhaust of industrial processes or renewable sources. The AD cycle uses an adsorbent such as the silica gel to desalt the sea or brackish water. Based on an experimental prototype AD plant, the life-cycle cost analysis of AD plants of assorted water production capacities has been simulated and these predictions are translated into unit cost of water production. Our results show that the specific energy consumption of the AD cycle is 1.38 kWh/m which is the lowest ever reported. For a plant capacity of 1000 m /d, the AD cycle offers a unit cost of &#36;0.457/m as compared to more than &#36;0.9 for the average RO plants. Besides being cost-effective, the AD cycle is also environment-friendly as it emits less CO emission per m generated, typically 85&#37; less, by comparison to an RO process. © 2010 Desalination Publications. 3 3 3 3 2

DOI： 10.5004/dwt.2010.1187

Language：English   Publishing type：Research paper (scientific journal)  

This paper presents the thermo-economic analysis of the adsorption desalination (AD) cycle that is driven by low-temperature waste heat from exhaust of industrial processes or renewable sources. The AD cycle uses an adsorbent such as the silica gel to desalt the sea or brackish water. Based on an experimental prototype AD plant, the life-cycle cost analysis of AD plants of assorted water production capacities has been simulated and these predictions are translated into unit cost of water production. Our results show that the specific energy consumption of the AD cycle is 1.38 kWh/m³ which is the lowest ever reported. For a plant capacity of 1000 m³/d, the AD cycle offers a unit cost of $0.457/m³ as compared to more than $0.9 for the average RO plants. Besides being cost-effective, the AD cycle is also environment-friendly as it emits less CO₂ emission per m³ generated, typically 85% less, by comparison to an RO process.

DOI： 10.5004/dwt.2010.1187

Language：English   Publishing type：Research paper (other academic)  

This paper discusses the performance analysis of adsorption desalination cycles with different configurations. The salient features of the AD cycle are the ability to the utilization of low temperature waste heat (typically less than 85°C), the deployment of environmentally friendly adsorbent/adsorbate pair (silica gel/water pair) and no major moving parts. The advanced AD cycle that incorporates the internal heat recovery between the condenser and evaporator by a heat recovery circuit is compared with conventional two-bed and four-bed AD cycles. Mathematical models to investigate the performance of the cycles are also presented. Extensive experiments have been conducted to explore the performance of such systems and are analysed in terms of key performance indicators namely the specific daily water production (SDWP) and the performance ratio (PR). Based on the experimental data, it is found that the SDWP of the advanced AD cycle with the condenser-evaporator heat recovery circuit is about 15 m³ of potable water per tonne of silica gel which is nearly two times that of the conventional AD cycles. Moreover, it is also found that the advanced AD cycle can be operational at 50°C hot water temperature with SDWP 4.3.

Language：English   Publishing type：Research paper (other academic)  

This paper presents the experimental investigation on the performance of a low temperature waste heat driven advanced desiccant dehumidifier (ADD) which has almost no moving parts. Type RD silica gel is selected as the adsorbent material for the innovative ADD. The advantages of the current dehumidifier are i) no major moving parts rendering no maintenance and ii) energy saving through dehumidification. The performance of the dehumidifier is investigated at different relative humidity and air flow rates. The optimal contact time of the air with the adsorbent that gives the highest performance has been experimentally evaluated. Finally, the energy saving by the advanced dehumidifier is analyzed and is found to be around 25~30%.

Language：English   Publishing type：Research paper (scientific journal)  

This paper investigates the performance of a solar-assisted adsorption (AD) cycle which produces two useful effects, namely cooling and desalination, with only a low-temperature heat input such as thermal energy from solar collectors. Heat sources varying from 65 to 80°C can be obtained from 215-m² flat plate-type solar collectors to regenerate the proposed silica gel-water-based AD cycle. In this paper, both mathematical modelling and experimental results from the AD cycle operation are discussed, in terms of two key parameters, namely specific daily water production (SDWP) and specific cooling capacity (SCC). The experimental results show that the AD cycle is capable of producing chilled water at 7 to 10°C with varying SCC range of 25-35 Rton/tonne of silica gel. Simultaneously, the AD cycle produces a SDWP of 3-5 m³ per tonne of silica gel per day, rendering it as a dual-effect machine that has an overall conversion or performance ratio of 0.8-1.1.

DOI： 10.1093/ijlct/ctp008

Language：Others   Publishing type：Research paper (scientific journal)  

This paper investigates the performance of a solar-assisted adsorption (AD) cycle which produces two useful effects, namely cooling and desalination, with only a low-temperature heat input such as thermal energy from solar collectors. Heat sources varying from 65 to 80°C can be obtained from 215-m flat plate-type solar collectors to regenerate the proposed silica gel-water-based AD cycle. In this paper, both mathematical modelling and experimental results from the AD cycle operation are discussed, in terms of two key parameters, namely specific daily water production (SDWP) and specific cooling capacity (SCC). The experimental results show that the AD cycle is capable of producing chilled water at 7 to 10°C with varying SCC range of 25-35 Rton/tonne of silica gel. Simultaneously, the AD cycle produces a SDWP of 3-5 m per tonne of silica gel per day, rendering it as a dual-effect machine that has an overall conversion or performance ratio of 0.8-1.1. © The Author 2009. Published by Oxford University Press. All rights reserved. 2 3

DOI： 10.1093/ijlct/ctp008

Language：English   Publishing type：Research paper (scientific journal)  

This paper presents the performances of an adsorption desalination (AD) system in two-bed and four-bed operational modes. The tested results are calculated in terms of key performance parameters namely, (i) specific daily water production (SDWP), (ii) cycle time, and (iii) performance ratio (PR) for various heat source temperatures, mass flow rates, cycle times along with a fixed heat sink temperature. The optimum input parameters such as driving heat source and cycle time of the AD cycle are also evaluated. It is found from the present experimental data that the maximum potable water production per tonne of adsorbent (silica gel) per day is about 10 m³ whilst the corresponding performance ratio is 0.61, and a longer cycle time is required to achieve maximum water production at lower heat source temperatures. This paper also provides a useful guideline for the operational strategy of the AD cycle.

DOI： 10.1016/j.ijheatmasstransfer.2008.10.012

Language：Others   Publishing type：Research paper (scientific journal)  

This paper presents the performances of an adsorption desalination (AD) system in two-bed and four-bed operational modes. The tested results are calculated in terms of key performance parameters namely, (i) specific daily water production (SDWP), (ii) cycle time, and (iii) performance ratio (PR) for various heat source temperatures, mass flow rates, cycle times along with a fixed heat sink temperature. The optimum input parameters such as driving heat source and cycle time of the AD cycle are also evaluated. It is found from the present experimental data that the maximum potable water production per tonne of adsorbent (silica gel) per day is about 10 m whilst the corresponding performance ratio is 0.61, and a longer cycle time is required to achieve maximum water production at lower heat source temperatures. This paper also provides a useful guideline for the operational strategy of the AD cycle. © 2008 Elsevier Ltd. All rights reserved. 3

DOI： 10.1016/j.ijheatmasstransfer.2008.10.012

Language：English   Publishing type：Research paper (other academic)  

This paper discusses the performance of an adsorption cycle (AD) that produces two useful effects namely: cooling and desalination. Low temperature hot water typically below 85°C extracted from waste heat is utilized to operate the adsorption cycle. The mathematical modeling and experimental results of the cycle are discussed. The performance of the Adsorption cycle is analyzed using key parameters such as the specific daily water production (SDWP), the specific cooling capacity (SCC), the coefficient of performance (COP), the performance ratio (PR) and the overall conversion ratio (OCR). The performance of the cycle across different hot water inlet temperatures ranging from 65 to 85°C for different configurations of the plant i.e., 2-bed and 4-bed mode operations, are investigated. The experimental results showed that the AD cycle is capable of producing the chilled water at 7 to 10°C with specific cooling capacity (SCC) ranging from 25 to 35 Rton /tonne of silica gel. Simultaneously, the AD cycle produces a specific daily water production (SDWP) of 3 to 5 m3 per tonne of silica gel per day, rendering it as a dual-effect machine that has an overall conversion or performance ratio of 0.8 to 1.2.

Language：English   Publishing type：Research paper (other academic)  

The HELP information provided by search engines can facilitate its user's information seeking process or hinder it. This study analyzed 20 search engines on how their HELP Systems are placed and organized. Help systems are separated into pre-search help system, and postsearch help system, and six aspects of help systems were investigated, including navigation, design elements, technical help, conceptual help, terminological, and strategic aspects. A general taxonomy of existing help systems of search engines is provided as the result. The proposed taxonomy may be used as the framework to develop questionnaire for further study in stereotyping search engine users.

DOI： 10.1109/ITNG.2008.219

Type：Competition, symposium, etc. 

Number of participants：155

Type：Academic society, research group, etc. 

Type：Peer review 

Number of peer-reviewed articles in foreign language journals：10

Type：Academic society, research group, etc. 

Type：Peer review 

Number of peer-reviewed articles in foreign language journals：10

Type：Competition, symposium, etc. 

Number of participants：88

Type：Competition, symposium, etc. 

Number of participants：90

Type：Competition, symposium, etc. 

Number of participants：120

Type：Academic society, research group, etc. 

Type：Peer review 

Number of peer-reviewed articles in foreign language journals：10

Type：Peer review 

Number of peer-reviewed articles in foreign language journals：10

Type：Peer review 

Number of peer-reviewed articles in foreign language journals：10

Type：Academic society, research group, etc. 

Type：Peer review 

Number of peer-reviewed articles in foreign language journals：10

"INSTITUTIONS OF ENGINEERS SINGAPORE (IES) PRESTIGIOUS ENGINEERING ACHIEVEMENT AWARDS 2009" with the project titled "Adsorption Technology for Desalination and Cooling".