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Kyaw Thu Last modified date：2023.11.27

Associate Professor / Department of Advanced Environmental Science and Engineering / Faculty of Engineering Sciences


Papers
1. Uthpara Perera, Kyaw Thu, Takahiko Miyazaki, Naoya Sakoda, Yukihiro Higashi, Saturation pressure measurements of the new refrigerant HFO1132(E), Proceedings of 2nd Conference on HFOs and Low GWP blends, 10.18462/iir.HFO.2021.1023, 12-19, 2021.06.
2. Animesh Pal, Kutub Uddin, Bidyut Baran Saha, Kyaw Thu, Hyun Sig Kil, Seong Ho Yoon, Jin Miyawaki, A benchmark for CO2 uptake onto newly synthesized biomass-derived activated carbons, Applied Energy, 10.1016/j.apenergy.2020.114720, 264, 2020.04, 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..
3. Kohei Matsui, Kyaw Thu, Takahiko Miyazaki, A hybrid power cycle using an inverted Brayton cycle with an indirect evaporative device for waste-heat recovery, Applied Thermal Engineering, 10.1016/j.applthermaleng.2020.115029, 170, 2020.04, 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..
4. Jun Tanimoto, Kyaw Thu, Nasruddin, Yudan Whulanza, Radon Dhelika, Editorial, Evergreen, 7, 1, iii-iv, 2020.03.
5. Indri Yaningsih, Agung Tri Wijayanta, Kyaw Thu, Takahiko Miyazaki, Influence of phase change phenomena on the performance of a desiccant dehumidification system, Applied Sciences (Switzerland), 10.3390/app10030868, 10, 3, 2020.02, 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..
6. Kaiser Ahmed Rocky, Md Amirul Islam, Animesh Pal, Sampad Ghosh, Kyaw Thu, Nasruddin, Bidyut Baran Saha, Experimental investigation of the specific heat capacity of parent materials and composite adsorbents for adsorption heat pumps, Applied Thermal Engineering, 10.1016/j.applthermaleng.2019.114431, 164, 2020.01, Specific heat capacity (Cp) of the adsorbents plays a vital role in the adsorption heat pump (AHP) systems design. This paper focuses on the experimental investigation of the Cp 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 Cp 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 Cp 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..
7. Sebastiano Tomassetti, Uthpala A. Perera, Giovanni Di Nicola, Mariano Pierantozzi, Yukihiro Higashi, Kyaw Thu, Two-Phase and Vapor-Phase Thermophysical Property (pvTz) Measurements of the Difluoromethane + trans-1,3,3,3-Tetrafluoroprop-1-ene Binary System, Journal of Chemical and Engineering Data, 10.1021/acs.jced.9b00995, 2020.01, 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..
8. Jun Tanimoto, Kyaw Thu, Hiroshi Furuno, Editorial, Evergreen, 10.5109/2547344, 6, 4, ii-iii, 2019.12.
9. K. Uddin, A. Pal, K. Thu, B. B. Saha, Adsorption of CO2 and Ethanol by a Spherical Activated Carbon in a Heat Pump, Journal of Engineering Physics and Thermophysics, 10.1007/s10891-019-02076-5, 92, 6, 1575-1581, 2019.11, 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..
10. Jun Tanimoto, Kyaw Thu, Hiroshi Furuno, Editorial, Evergreen, 6, 3, ii-iii, 2019.09.
11. Jun Tanimoto, Kyaw Thu, Hiroshi Furuno, Nasruddin, Mohd Fairus Mohd Yasin, Muhammad Arif Budiyanto, Editorial, Evergreen, 10.1007/s11282-007-0065-z, 6, 2, iii-iv, 2019.06.
12. Md Amirul Islam, Animesh Pal, Kyaw Thu, Bidyut Baran Saha, Study on performance and environmental impact of supermarket refrigeration system in Japan, Evergreen, 10.5109/2321014, 6, 2, 168-176, 2019.06, 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..
13. Jung Gil Lee, Chul u. Bak, Thu Kyaw, Noreddine Ghaffour, Young Deuk Kim, Effect of seawater-coolant feed arrangement in a waste heat driven multi-stage vacuum membrane distillation system, Separation and Purification Technology, 10.1016/j.seppur.2018.11.012, 12-20, 2019.04, 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..
14. Ahmad Imam Rifa'I, Muhammad Faisal Hasan, Budi Kristiawan, Agung Tri Wijayanta, Takahiko Miyazaki, Thu Kyaw, Koji Enoki, Experimental study of heat transfer enhancement and pressure drop using TiO 2 /distilled water nanofluid inside counter flow double tube heat exchanger, 4th International Conference on Industrial, Mechanical, Electrical, and Chemical Engineering, ICIMECE 2018 4th International Conference on Industrial, Mechanical, Electrical, and Chemical Engineering, 10.1063/1.5098218, 2019.04, 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..
15. Bidyut Baran Saha, Thu Kyaw, Nasruddin, Mohd Fairus Mohd Yasin, Muhammad Arif Budiyanto, Editorial, Evergreen, 6, 1, iii-v, 2019.03.
16. Animesh Pal, Kutub Uddin, Thu Kyaw, Bidyut Baran Saha, Activated carbon and graphene nanoplatelets based novel composite for performance enhancement of adsorption cooling cycle, Energy Conversion and Management, 10.1016/j.enconman.2018.10.092, 134-148, 2019.01, 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..
17. Mahbubul Muttakin, Animesh Pal, Kutub Uddin, Thu Kyaw, Kazuhide Ito, Bidyut Baran Saha, Experimental study on the effect of adsorbent height on adsorption dynamics, 10th International Meeting of Advances in Thermofluids - Smart City: Advances in Thermofluid Technology in Tropical Urban Development, IMAT 2018 10th International Meeting of Advances in Thermofluids, IMAT 2018 - Smart City Advances in Thermofluid Technology in Tropical Urban Development, 10.1063/1.5086549, 2019.01, 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...
18. Animesh Pal, Anett Kondor, Sourav Mitra, Thu Kyaw, Harish Sivasankaran, Bidyut Baran Saha, On surface energy and acid–base properties of highly porous parent and surface treated activated carbons using inverse gas chromatography, Journal of Industrial and Engineering Chemistry, 10.1016/j.jiec.2018.09.046, 69, 432-443, 2019.01, 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..
19. Frederick L. Sutherland, Khin Zaw, Sebastien Meffre, Jay Thompson, Karsten Goemann, Kyaw Thu, Than Than Nu, Mazlinfalina Mohd Zin, Stephen J. Harris, Diversity in ruby geochemistry and its inclusions
Intra-and inter-continental comparisons from Myanmar and Eastern Australia, Minerals, 10.3390/min9010028, 9, 1, 2019.01, 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 6). The diverse results emphasize ruby’s potential for geographic typing..
20. Bidyut Baran Saha, Thu Kyaw, Naoko Mae, Editorial, Evergreen, 10.5109/2174851, 5, 4, ii-iii, 2018.12.
21. Shinnosuke Maeda, Thu Kyaw, Tomohiro Maruyama, Takahiko Miyazaki, Critical review on the developments and future aspects of adsorption heat pumps for automobile air conditioning, Applied Sciences (Switzerland), 10.3390/app8112061, 8, 11, 2018.10, 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..
22. Fatin Hazwani M. Azahar, Sourav Mitra, Akihiro Yabushita, Akira Harata, Bidyut Baran Saha, Thu Kyaw, Improved model for the isosteric heat of adsorption and impacts on the performance of heat pump cycles, Applied Thermal Engineering, 10.1016/j.applthermaleng.2018.07.131, 143, 688-700, 2018.10, 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..
23. Bidyut Baran Saha, Thu Kyaw, Agung Tri Wijayanta, Kyushu university institutional repository, Evergreen, 10.5109/1957499, 5, 3, ii-iii, 2018.09, 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..
24. Mahbubul Muttakin, Sourav Mitra, Thu Kyaw, Kazuhide Ito, Bidyut Baran Saha, Theoretical framework to evaluate minimum desorption temperature for IUPAC classified adsorption isotherms, International Journal of Heat and Mass Transfer, 10.1016/j.ijheatmasstransfer.2018.01.107, 122, 795-805, 2018.07, 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..
25. Animesh Pal, Kutub Uddin, Thu Kyaw, Bidyut Baran Saha, Environmental assessment and characteristics of next generation refrigerants, Evergreen, 10.5109/1936218, 5, 2, 58-66, 2018.06, 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..
26. Muhammad Faisal Hasan, Md Sayeed Ur Rahim Mahadi, Takahiko Miyazaki, Shigeru Koyama, Thu Kyaw, Exergy analysis of serpentine thermosyphon solar water heater, Applied Sciences (Switzerland), 10.3390/app8030391, 8, 3, 2018.03, 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..
27. Bidyut Baran Saha, Thu Kyaw, Selected Papers from the 4th International Symposium on Innovative Materials for Processes in Energy Systems (IMPRES2016), Heat Transfer Engineering, 10.1080/01457632.2018.1450325, 1-2, 2018.03.
28. Sourav Mitra, Mahbubul Muttakin, Thu Kyaw, Bidyut Baran Saha, Study on the influence of adsorbent particle size and heat exchanger aspect ratio on dynamic adsorption characteristics, Applied Thermal Engineering, 10.1016/j.applthermaleng.2018.01.015, 133, 764-773, 2018.03, 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..
29. Thu Kyaw, S. Mitra, Bidyut Baran Saha, S. Srinivasa Murthy, Thermodynamic feasibility evaluation of hybrid dehumidification – mechanical vapour compression systems, Applied Energy, 10.1016/j.apenergy.2018.01.024, 213, 31-44, 2018.03, 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..
30. Kutub Uddin, Md Amirul Islam, Sourav Mitra, Jong boong Lee, Thu Kyaw, Bidyut Baran Saha, Shigeru Koyama, Specific heat capacities of carbon-based adsorbents for adsorption heat pump application, Applied Thermal Engineering, 10.1016/j.applthermaleng.2017.09.057, 129, 117-126, 2018.01, 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..
31. Md Matiar Rahman, Animesh Pal, Kutub Uddin, Thu Kyaw, Bidyut Baran Saha, Statistical analysis of optimized isotherm model for maxsorb III/ethanol and silica gel/water pairs, Evergreen, 10.5109/2174852, 5, 4, 1-12, 2018.01, 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..
32. Md Amirul Islam, K. Srinivasan, Thu Kyaw, Bidyut Baran Saha, Assessment of total equivalent warming impact (TEWI) of supermarket refrigeration systems, International Journal of Hydrogen Energy, 10.1016/j.ijhydene.2017.07.035, 42, 43, 26973-26983, 2017.10, 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..
33. Bidyut Baran Saha, Thu Kyaw, Editorial, Evergreen, 4, 2-3, i-iii, 2017.09.
34. T. D. Bui, Y. Wong, Thu Kyaw, S. J. Oh, M. Kum Ja, K. C. Ng, I. Raisul, K. J. Chua, Effect of hygroscopic materials on water vapor permeation and dehumidification performance of poly(vinyl alcohol) membranes, Journal of Applied Polymer Science, 10.1002/app.44765, 134, 17, 2017.05, 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..
35. Animesh Pal, Hyun Sig Kil, Sourav Mitra, Thu Kyaw, Bidyut Baran Saha, Seong-Ho Yoon, Jin Miyawaki, Takahiko Miyazaki, Shigeru Koyama, Ethanol adsorption uptake and kinetics onto waste palm trunk and mangrove based activated carbons, Applied Thermal Engineering, 10.1016/j.applthermaleng.2017.04.099, 122, 389-397, 2017.01, 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..
36. Thu Kyaw, Jayaprakash Saththasivam, Bidyut Baran Saha, Kian Jon Chua, S. Srinivasa Murthy, Kim Choon Ng, Experimental investigation of a mechanical vapour compression chiller at elevated chilled water temperatures, Applied Thermal Engineering, 10.1016/j.applthermaleng.2017.05.091, 123, 226-233, 2017.01, 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..
37. Animesh Pal, Maisara Shahrom Raja Shahrom, Muhammad Moniruzzaman, Cecilia Devi Wilfred, Sourav Mitra, Thu Kyaw, Bidyut Baran Saha, Ionic liquid as a new binder for activated carbon based consolidated composite adsorbents, Chemical Engineering Journal, 10.1016/j.cej.2017.06.031, 326, 980-986, 2017.01, 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..
38. Thu Kyaw, Bidyut Baran Saha, Sourav Mitra, Kian Jon Chua, Modeling and Simulation of Mass Recovery Process in Adsorption System for Cooling and Desalination, 8th International Conference on Applied Energy, ICAE 2016 Energy Procedia, 10.1016/j.egypro.2017.03.574, 105, 2004-2009, 2017.01, 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..
39. Sourav Mitra, Thu Kyaw, Bidyut Baran Saha, Kandadai Srinivasan, Pradip Dutta, Modeling study of two-stage, multi-bed air cooled silica gel + water adsorption cooling cum desalination system, Applied Thermal Engineering, 10.1016/j.applthermaleng.2016.12.011, 114, 704-712, 2017.01, 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..
40. Sourav Mitra, Thu Kyaw, Bidyut Baran Saha, Pradip Dutta, Modeling the Effect of Heat Source Temperature on the Performance of Two-stage Air Cooled Silica Gel + Water Adsorption System, 8th International Conference on Applied Energy, ICAE 2016 Energy Procedia, 10.1016/j.egypro.2017.03.575, 105, 2010-2015, 2017.01, Adsorption systems can utilize low grade waste heat (temperature
41. Sourav Mitra, Thu Kyaw, Bidyut Baran Saha, Pradip Dutta, Performance evaluation and determination of minimum desorption temperature of a two-stage air cooled silica gel/water adsorption system, Applied Energy, 10.1016/j.apenergy.2017.08.198, 206, 507-518, 2017.01, 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..
42. Thu Kyaw, Hideharu Yanagi, Bidyut Baran Saha, Kim Choon Ng, Performance investigation on a 4-bed adsorption desalination cycle with internal heat recovery scheme, Desalination, 10.1016/j.desal.2016.09.027, 402, 88-96, 2017.01, 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..
43. Animesh Pal, Thu Kyaw, Sourav Mitra, Ibrahim I. El-Sharkawy, Bidyut Baran Saha, Hyun Sig Kil, Seong-Ho Yoon, Jin Miyawaki, Study on biomass derived activated carbons for adsorptive heat pump application, International Journal of Heat and Mass Transfer, 10.1016/j.ijheatmasstransfer.2017.02.081, 110, 7-19, 2017.01, 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..
44. Seung Jin Oh, Kim Choon Ng, Thu Kyaw, Marip Kum Ja, Md Raisul Islam, Wongee Chun, Kian Jon Ernest Chua, Studying the performance of a dehumidifier with adsorbent coated heat exchangers for tropical climate operations, Science and Technology for the Built Environment, 10.1080/23744731.2016.1218234, 23, 1, 127-135, 2017.01, 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..
45. Kyaw Thu, Khin Zaw, Gem deposits of Myanmar, Geological Society Memoir, 10.1144/M48.23, 497-529, 2017.01.
46. Bidyut Baran Saha, Thu Kyaw, Editorial, Evergreen, 4, 1, ii-iii, 2017.
47. Q. Chen, Thu Kyaw, T. D. Bui, Y. Li, K. C. Ng, K. J. Chua, Development of a model for spray evaporation based on droplet analysis, Desalination, 10.1016/j.desal.2016.08.017, 399, 69-77, 2016.12, 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..
48. Thu Kyaw, Bidyut Baran Saha, Kian Jon Chua, Kim Choon Ng, Performance investigation of a waste heat-driven 3-bed 2-evaporator adsorption cycle for cooling and desalination, International Journal of Heat and Mass Transfer, 10.1016/j.ijheatmasstransfer.2016.05.127, 101, 1111-1122, 2016.10, 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..
49. J. Lin, Thu Kyaw, T. D. Bui, R. Z. Wang, K. C. Ng, M. Kumja, K. J. Chua, Unsteady-state analysis of a counter-flow dew point evaporative cooling system, Energy, 10.1016/j.energy.2016.07.036, 113, 172-185, 2016.10, 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..
50. Young Deuk Kim, Thu Kyaw, Kim Choon Ng, Gary L. Amy, Noreddine Ghaffour, A novel integrated thermal-/membrane-based solar energy-driven hybrid desalination system
Concept description and simulation results, Water Research, 10.1016/j.watres.2016.05.002, 100, 7-19, 2016.09, 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%..
51. Seung Jin Oh, Kim Choon Ng, Thu Kyaw, Wongee Chun, Kian Jon Ernest Chua, Forecasting long-term electricity demand for cooling of Singapore's buildings incorporating an innovative air-conditioning technology, Energy and Buildings, 10.1016/j.enbuild.2016.05.073, 127, 183-193, 2016.09, 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..
52. Thu Kyaw, Bidyut Baran Saha, Kian Jon Chua, Thuan Duc Bui, Thermodynamic analysis on the part-load performance of a microturbine system for micro/mini-CHP applications, Applied Energy, 10.1016/j.apenergy.2016.06.106, 178, 600-608, 2016.09, 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..
53. Muhammad Wakil Shahzad, Thu Kyaw, Kim Choon Ng, Chun WonGee, Recent development in thermally activated desalination methods
achieving an energy efficiency less than 2.5 kWhelec/m3, Desalination and Water Treatment, 10.1080/19443994.2015.1035499, 57, 16, 7396-7405, 2016.04, 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 kWhelec/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 kWhelec/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 kWhthermal/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 kWhthermal/m3 would result in an electrical equivalent of less than 2.5 kWhelec/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..
54. Bidyut Baran Saha, Ibrahim I. El-Sharkawy, Muhammad Wakil Shahzad, Thu Kyaw, Li Ang, Kim Choon Ng, Fundamental and application aspects of adsorption cooling and desalination, Applied Thermal Engineering, 10.1016/j.applthermaleng.2015.09.113, 97, 68-76, 2016.03, 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..
55. J. Lin, Thu Kyaw, T. D. Bui, R. Z. Wang, K. C. Ng, K. J. Chua, Study on dew point evaporative cooling system with counter-flow configuration, Energy Conversion and Management, 10.1016/j.enconman.2015.11.059, 109, 153-165, 2016.02, 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..
56. Ang Li, Thu Kyaw, Azhar Bin Ismail, Kim Choon Ng, A heat transfer correlation for transient vapor uptake of powdered adsorbent embedded onto the fins of heat exchangers, Applied Thermal Engineering, 10.1016/j.applthermaleng.2015.09.057, 93, 668-677, 2016.01, 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..
57. Muhammad Wakil Shahzad, Kim Choon Ng, Thu Kyaw, Future sustainable desalination using waste heat
Kudos to thermodynamic synergy, Environmental Science: Water Research and Technology, 10.1039/c5ew00217f, 2, 1, 206-212, 2016.01, 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..
58. Ang Li, Thu Kyaw, Azhar Bin Ismail, Muhammad Wakil Shahzad, Kim Choon Ng, Performance of adsorbent-embedded heat exchangers using binder-coating method, International Journal of Heat and Mass Transfer, 10.1016/j.ijheatmasstransfer.2015.08.097, 92, 149-157, 2016.01, 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..
59. Bidyut Baran Saha, Thu Kyaw, Editorial, Evergreen, 3, 2, ii-iii, 2016.
60. Thu Kyaw, Young Deuk Kim, Muhammad Wakil Shahzad, Jayaprakash Saththasivam, Kim Choon Ng, Performance investigation of an advanced multi-effect adsorption desalination (MEAD) cycle, Applied Energy, 10.1016/j.apenergy.2015.09.035, 159, 469-477, 2015.12, 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..
61. Young Deuk Kim, Thu Kyaw, Seung Hak Choi, Solar-assisted multi-stage vacuum membrane distillation system with heat recovery unit, Desalination, 10.1016/j.desal.2015.04.003, 367, 161-171, 2015.07, 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..
62. Muhammad Wakil Shahzad, Thu Kyaw, Yong deuk Kim, Kim Choon Ng, An experimental investigation on MEDAD hybrid desalination cycle, Applied Energy, 10.1016/j.apenergy.2015.03.062, 148, 273-281, 2015.06, 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..
63. Kim Choon Ng, Thu Kyaw, Seung Jin Oh, Li Ang, Muhammad Wakil Shahzad, Azhar Bin Ismail, Recent developments in thermally-driven seawater desalination
Energy efficiency improvement by hybridization of the MED and AD cycles, Desalination, 10.1016/j.desal.2014.10.025, 356, 255-270, 2015.01, 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..
64. Young Deuk Kim, Thu Kyaw, Kim Choon Ng, Evaluation and parametric optimization of the thermal performance and cost effectiveness of active-indirect solar hot water plants, Evergreen, 2, 2, 50-60, 2015, 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 Ac= 1140 m2and Vt= 32 m3, 5.91 years with Ac= 750 m2and Vt= 24 m3and 8.39 years with Ac= 1050 m2and Vt= 28 m3, respectively..
65. F. Lin Sutherland, Khin Zaw, Sebastien Meffre, Tzen Fui Yui, Kyaw Thu, Advances in trace element “fingerprinting” of gem corundum, ruby and sapphire, Mogok area, Myanmar, Minerals, 10.3390/min5010061, 5, 1, 61-79, 2014.12, 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 (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..
66. Thu Kyaw, Young Deuk Kim, Azhar Bin Ismil, Bidyut Baran Saha, Kim Choon Ng, Adsorption characteristics of methane on Maxsorb III by gravimetric method, Applied Thermal Engineering, 10.1016/j.applthermaleng.2014.04.076, 72, 2, 200-205, 2014.11, 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..
67. Azhar Bin Ismail, Thu Kyaw, Kandadai Srinivasan, Kim Choon Ng, Adsorption kinetics of propane on energetically heterogeneous activated carbon, Applied Thermal Engineering, 10.1016/j.applthermaleng.2014.07.023, 72, 2, 206-210, 2014.11, 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..
68. Muhammad Wakil Shahzad, Kim Choon Ng, Thu Kyaw, Bidyut Baran Saha, Won Gee Chun, Multi effect desalination and adsorption desalination (MEDAD)
A hybrid desalination method, Applied Thermal Engineering, 10.1016/j.applthermaleng.2014.03.064, 72, 2, 289-297, 2014.11, 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..
69. Ang Li, Azhar Bin Ismail, Thu Kyaw, Kim Choon Ng, Wai Soong Loh, Performance evaluation of a zeolite-water adsorption chiller with entropy analysis of thermodynamic insight, Applied Energy, 10.1016/j.apenergy.2014.01.086, 130, 702-711, 2014.10, 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..
70. Young Deuk Kim, Thu Kyaw, Kim Choon Ng, Adsorption characteristics of water vapor on ferroaluminophosphate for desalination cycle, Desalination, 10.1016/j.desal.2014.04.009, 344, 350-356, 2014.07, 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..
71. Young Deuk Kim, Thu Kyaw, Moawya E. Masry, Kim Choon Ng, Water quality assessment of solar-assisted adsorption desalination cycle, Desalination, 10.1016/j.desal.2014.03.021, 344, 144-151, 2014.07, 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..
72. X. Cui, K. J. Chua, W. M. Yang, K. C. Ng, Thu Kyaw, V. T. Nguyen, Studying the performance of an improved dew-point evaporative design for cooling application, Applied Thermal Engineering, 10.1016/j.applthermaleng.2013.11.070, 63, 2, 624-633, 2014.02, 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%..
73. Azhar Bin Ismail, Ang Li, Wai Soong Loh, Thu Kyaw, Kim Choon Ng, A modeling and experimental study of a low-temperature application miniature Pressurized Adsorption Chiller (PAC), 7th Asian Conference on Refrigeration and Air Conditioning, ACRA 2014 ACRA 2014 - Proceedings of the 7th Asian Conference on Refrigeration and Air Conditioning, 2014.01, 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 (
74. Thu Kyaw, Young Deuk Kim, Gary Amy, Won Gee Chun, Kim Choon Ng, A synergetic hybridization of adsorption cycle with the multi-effect distillation (MED), Applied Thermal Engineering, 10.1016/j.applthermaleng.2013.09.023, 62, 1, 245-255, 2014.01, 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..
75. Muhammad Wakil Shahzad, Thu Kyaw, Bidyut Baran Saha, Kim Choon Ng, An emerging hybrid multi-effect adsorption desalination system, Evergreen, 1, 2, 30-36, 2014.01, 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..
76. Ang Li, Azhar Bin Ismail, Thu Kyaw, Muhammad Wakil Shahzad, Kim Choon Ng, Wongee Chun, Improvement of adsorbent embeded heat transfer through introduction of binder, 7th Asian Conference on Refrigeration and Air Conditioning, ACRA 2014 ACRA 2014 - Proceedings of the 7th Asian Conference on Refrigeration and Air Conditioning, 2014.01, 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..
77. Azhar Bin Ismail, Ang Li, Thu Kyaw, Kim Choon Ng, Wongee Chun, Pressurized adsorption cooling cycles driven by solar/waste heat, Applied Thermal Engineering, 10.1016/j.applthermaleng.2014.02.063, 67, 1-2, 106-113, 2014.01, 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..
78. Khin Zaw, Lin Sutherland, Tzen Fu Yui, Sebastien Meffre, Thu Kyaw, Vanadium-rich ruby and sapphire within Mogok Gemfield, Myanmar
implications for gem color and genesis, Mineralium Deposita, 10.1007/s00126-014-0545-0, 50, 1, 25-39, 2014.01, 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..
79. J. Saththasivam, Young Deuk Kim, Thu Kyaw, Kim Choon Ng, A study on the applicability of adsorption desalination cum cooling cycles in zero liquid discharge process, 7th Asian Conference on Refrigeration and Air Conditioning, ACRA 2014 ACRA 2014 - Proceedings of the 7th Asian Conference on Refrigeration and Air Conditioning, 2014, 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..
80. Aug Li, Azhar Bin Ismail, Thu Kyaw, Muhammad Wakil Shahzad, Kim Choon Ng, Bidyut Baran Saha, Formulation of water equilibrium uptakes on silica gel and ferroaluminophosphate zeolite for adsorption cooling and desalination applications, Evergreen, 1, 2, 37-45, 2014, 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..
81. Young Deuk Kim, Thu Kyaw, Jayaprakash Saththasivam, Kim C. Ng, Noreddine Ghaffour, Performance evaluation of multi-stage vacuum membrane distillation
The effect of seawater-coolant feed arrangement, 7th Asian Conference on Refrigeration and Air Conditioning, ACRA 2014 ACRA 2014 - Proceedings of the 7th Asian Conference on Refrigeration and Air Conditioning, 2014, 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..
82. Hpone Phyo Kan-Nyunt, Stefanos Karampelas, Klemens Link, Kyaw Thu, Lore Kiefert, Pierre Hardy, Blue sapphires from the baw mar mine in mogok, Gems and Gemology, 10.5741/GEMS.49.4.223, 49, 4, 223-232, 2013.12, 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..
83. Azhar Bin Ismail, Ang Li, Thu Kyaw, K. C. Ng, Wongee Chun, On the thermodynamics of refrigerant + heterogeneous solid surfaces adsorption, Langmuir, 10.1021/la403330t, 29, 47, 14494-14502, 2013.11, 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 (ha), entropy (sa), and the specific heat capacity (cp,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 (qs), 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..
84. Azhar bin Ismail, Wai Soong Loh, Thu Kyaw, Kim Choon Ng, A study on the kinetics of propane-activated carbon
Theory and experiments, 5th International Meeting on Advances of Thermofluids, IMAT 2012 Advances in Thermofluids, 10.4028/www.scientific.net/AMM.388.76, 76-82, 2013.10, 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..
85. Thu Kyaw, Young Deuk Kim, Bao Juan Xi, Azhar Bin Ismail, Kim Choon Ng, Thermophysical properties of novel zeolite materials for sorption cycles, 5th International Meeting on Advances of Thermofluids, IMAT 2012 Advances in Thermofluids, 10.4028/www.scientific.net/AMM.388.116, 116-122, 2013.10, 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..
86. Thu Kyaw, Hideharu Yanagi, Bidyut Baran Saha, Kim Choon Ng, Performance analysis of a low-temperature waste heat-driven adsorption desalination prototype, International Journal of Heat and Mass Transfer, 10.1016/j.ijheatmasstransfer.2013.06.053, 65, 662-669, 2013.07, 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..
87. Thu Kyaw, Anutosh Chakraborty, Bidyut Baran Saha, Kim Choon Ng, Thermo-physical properties of silica gel for adsorption desalination cycle, Applied Thermal Engineering, 10.1016/j.applthermaleng.2011.09.038, 50, 2, 1596-1602, 2013.02, 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..
88. Thu Kyaw, Young Deuk Kim, Gary Amy, Won Gee Chun, Kim Choon Ng, A hybrid multi-effect distillation and adsorption cycle, Applied Energy, 10.1016/j.apenergy.2012.12.007, 104, 810-821, 2013.01, 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..
89. Kim Choon Ng, Thu Kyaw, Youngdeuk Kim, Anutosh Chakraborty, Gary Amy, Adsorption desalination
An emerging low-cost thermal desalination method, Desalination, 10.1016/j.desal.2012.07.030, 308, 161-179, 2013.01, 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..
90. Thu Kyaw, Young Deuk Kim, Aung Myat, Won Gee Chun, Kim Choon Ng, Entropy generation analysis of an adsorption cooling cycle, International Journal of Heat and Mass Transfer, 10.1016/j.ijheatmasstransfer.2012.12.055, 60, 1, 143-155, 2013.01, 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..
91. Aung Myat, Ng Kim Choon, Thu Kyaw, Young Deuk Kim, Experimental investigation on the optimal performance of Zeolite-water adsorption chiller, Applied Energy, 10.1016/j.apenergy.2012.08.005, 102, 582-590, 2013.01, 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..
92. Thu Kyaw, Anuthosh Chakraborty, Young Deuk Kim, Aung Myat, Bidyut Baran Saha, Kim Choon Ng, Numerical simulation and performance investigation of an advanced adsorption desalination cycle, Desalination, 10.1016/j.desal.2012.04.021, 308, 209-218, 2013.01, 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..
93. Young Deuk Kim, Thu Kyaw, Aung Myat, Kim Choon Ng, Numerical simulation of solar-assisted multi-effect distillation (SMED) desalination systems, Desalination and Water Treatment, 10.1080/19443994.2012.695044, 51, 4-6, 1242-1253, 2013.01, 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..
94. Young Deuk Kim, Thu Kyaw, Noreddine Ghaffour, Kim Choon Ng, Performance investigation of a solar-assisted direct contact membrane distillation system, Journal of Membrane Science, 10.1016/j.memsci.2012.10.008, 427, 345-364, 2013.01, 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%..
95. Thu Kyaw, Young Deuk Kim, Aung Myat, Anutosh Chakraborty, Kim Choon Ng, Performance investigation of advanced adsorption desalination cycle with condenser-evaporator heat recovery scheme, Desalination and Water Treatment, 10.1080/19443994.2012.693659, 51, 1-3, 150-163, 2013.01, 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..
96. Aung Myat, Thu Kyaw, Young Deuk Kim, Ng Kim Choon, The performance investigation of a temperature cascaded cogeneration system equipped with adsorption desalination unit, Desalination and Water Treatment, 10.1080/19443994.2012.714580, 51, 7-9, 1900-1907, 2013.01, 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%..
97. Aung Myat, Thu Kyaw, Young Deuk Kim, Ng Kim Choon, The performance of a temperature cascaded cogeneration system producing steam, cooling and dehumidification, Desalination and Water Treatment, 10.1080/19443994.2012.694232, 51, 7-9, 1915-1921, 2013.01, 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%..
98. Muhammad Wakil Shahzada, Kim Choon Ng, Thu Kyaw, Aung Myat, Chun Won Gee, An improved film evaporation correlation for saline water at sub-atmospheric pressures, 4th International Meeting of Advances in Thermofluids, IMAT 2011 4th International Meeting of Advances in Thermofluids, IMAT 2011, 10.1063/1.4704324, 1085-1091, 2012.12, 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..
99. Aung Myat, Thu Kyaw, Young Deuk Kim, Ng Kim Choon, Performance investigation of a cogeneration plant with the efficient and compact heat recovery system, 4th International Meeting of Advances in Thermofluids, IMAT 2011 4th International Meeting of Advances in Thermofluids, IMAT 2011, 10.1063/1.4704299, 880-888, 2012.12, 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%..
100. Anutosh Chakraborty, Thu Kyaw, Bidyut Baran Saha, Kim Choon Ng, Adsorption-Desalination Cycle, Advances in Water Desalination, 10.1002/9781118347737.ch5, 377-451, 2012.10.
101. Aung Myat, Thu Kyaw, Ng Kim Choon, The experimental investigation on the performance of a low temperature waste heat-driven multi-bed desiccant dehumidifier (MBDD) and minimization of entropy generation, Applied Thermal Engineering, 10.1016/j.applthermaleng.2012.01.041, 39, 70-77, 2012.06, 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..
102. A. Myat, Thu Kyaw, K. C. Ng, Y. D. Kim, An entropy generation and genetic algorithm optimization of two-bed adsorption cooling cycle, Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering, 10.1177/0954408911416439, 226, 2, 142-156, 2012.05, 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..
103. Kim Choon Ng, Thu Kyaw, Bidyut Baran Saha, Anutosh Chakraborty, Study on a waste heat-driven adsorption cooling cum desalination cycle, International Journal of Refrigeration, 10.1016/j.ijrefrig.2011.01.008, 35, 3, 685-693, 2012.05, 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..
104. Young Deuk Kim, Thu Kyaw, Hitasha Kaur Bhatia, Charanjit Singh Bhatia, Kim Choon Ng, Thermal analysis and performance optimization of a solar hot water plant with economic evaluation, Solar Energy, 10.1016/j.solener.2012.01.030, 86, 5, 1378-1395, 2012.05, 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..
105. Aung Myat, Thu Kyaw, Young Deuk Kim, Bidyut Baran Saha, Kim Choon Ng, Entropy generation minimization
A practical approach for performance evaluation of temperature cascaded co-generation plants, Energy, 10.1016/j.energy.2012.07.062, 46, 1, 493-521, 2012.01, 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..
106. Aung Myat, Thu Kyaw, Young Deuk Kim, A. Chakraborty, Won Gee Chun, Kim Choon Ng, A second law analysis and entropy generation minimization of an absorption chiller, Applied Thermal Engineering, 10.1016/j.applthermaleng.2011.04.004, 31, 14-15, 2405-2413, 2011.10, 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..
107. Anutosh Chakraborty, Kai Choong Leong, Thu Kyaw, Bidyut Baran Saha, Kim Choon Ng, Theoretical insight of adsorption cooling, Applied Physics Letters, 10.1063/1.3592260, 98, 22, 2011.05, 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..
108. Awaludin Martin, Wai Soong Loh, Kazi Afzalur Rahman, Thu Kyaw, Bambang Surayawan, M. Idrus Alhamid, Nasruddin, Kim Choon Ng, Adsorption isotherms of CH4 on activated carbon from Indonesian low grade coal, Journal of Chemical and Engineering Data, 10.1021/je100495w, 56, 3, 361-367, 2011.03, 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..
109. Lau Hao Wen, Azhar Bin Ismail, P. M. Menon, Jayaprakash Saththasivam, Thu Kyaw, Ng Kim Choon, Case studies of microbubbles in wastewater treatment, Desalination and Water Treatment, 10.5004/dwt.2011.1217, 30, 1-3, 10-16, 2011.01, 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..
110. Thu Kyaw, Bidyut Baran Saha, Anutosh Chakraborty, Won Gee Chun, Kim Choon Ng, Study on an advanced adsorption desalination cycle with evaporator-condenser heat recovery circuit, International Journal of Heat and Mass Transfer, 10.1016/j.ijheatmasstransfer.2010.09.065, 54, 1-3, 43-51, 2011.01, 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..
111. Anutosh Chakraborty, Thu Kyaw, Kim Choon Ng, Advanced adsorption cooling cum desalination cycle
A thermodynamic framework, ASME 2011 International Mechanical Engineering Congress and Exposition, IMECE 2011 ASME 2011 International Mechanical Engineering Congress and Exposition, IMECE 2011, 4, 605-610, 2011, 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..
112. Thu Kyaw, A. Chakraborty, Bidyut Baran Saha, Won Gee Chun, K. C. Ng, Life-cycle cost analysis of adsorption cycles for desalination, Desalination and Water Treatment, 10.5004/dwt.2010.1187, 20, 1-3, 1-10, 2010.01, 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..
113. Kim Choon Ng, Thu Kyaw, Hideharu Yanagi, Anutosh Chakraborty, Bidyut Baran Saha, Won Gee Chun, Performance analysis of a low temperature waste heat-driven adsorption desalination prototype plant, 5th Asian Conference on Refrigeration and Air Conditioning - Green Breeze from Asia: Frontiers of Refrigerants, Heat Transfer and System, ACRA 2010 5th Asian Conference on Refrigeration and Air Conditioning, ACRA 2010 - Green Breeze from Asia Frontiers of Refrigerants, Heat Transfer and System, 2010.01, 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..
114. Aung Myat, Kim Choon Ng, Hideharu Yanagi, Thu Kyaw, Won Gee Chun, Experimental investigation on the performance of a waste heat-driven advanced desiccant dehumidifier without moving parts, 5th Asian Conference on Refrigeration and Air Conditioning - Green Breeze from Asia: Frontiers of Refrigerants, Heat Transfer and System, ACRA 2010 5th Asian Conference on Refrigeration and Air Conditioning, ACRA 2010 - Green Breeze from Asia: Frontiers of Refrigerants, Heat Transfer and System, 2010, 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%..
115. Kim Choon Ng, Thu Kyaw, Anutosh Chakraborty, Bidyut Baran Saha, Won Gee Chun, Solar-assisted dual-effect adsorption cycle for the production of cooling effect and potable water, International Journal of Low-Carbon Technologies, 10.1093/ijlct/ctp008, 4, 2, 61-67, 2009.06, 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..
116. Thu Kyaw, Kim Choon Ng, Bidyut Baran Saha, Anutosh Chakraborty, Shigeru Koyama, Operational strategy of adsorption desalination systems, International Journal of Heat and Mass Transfer, 10.1016/j.ijheatmasstransfer.2008.10.012, 52, 7-8, 1811-1816, 2009.03, 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..
117. Thu Kyaw, Kim Choon Ng, Bidyut Baran Saha, Anutosh Chakraborty, Shigeru Koyama, Waste heat-driven dual-purpose adsorption cycle for cooling and desalination, 4th Asian Conference on Refrigeration and Air-Conditioning, ACRA 2009 4th Asian Conference on Refrigeration and Air-Conditioning, ACRA 2009, 299-304, 2009.01, 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..
118. Yun Ke Chang, Miguel A.Morales Arroyo, Amanda Spink, Myat Thu Aung, Kyaw Thu, Ya Lwin, Zaw Win Htike, Search engines' help systems, International Conference on Information Technology: New Generations, ITNG 2008 Proceedings - International Conference on Information Technology New Generations, ITNG 2008, 10.1109/ITNG.2008.219, 309-314, 2008.05, 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..


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