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R. Z. Wang - One of the best experts on this subject based on the ideXlab platform.
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dehumidification assessment for desiccant coated heat exchanger systems in different buildings and climates fast choice of Desiccants
Energy and Buildings, 2020Co-Authors: Xu Zheng, R. Z. WangAbstract:Abstract Energy conservation and emission reduction have become a global consensus. As a novel promising energy-saving dehumidification technology, desiccant coated heat exchanger (DCHE)-based air conditioning systems have attracted immense attention recently. This paper provides a quick and reasonable selection of desiccant materials for DCHE systems using water as the cooling medium in different buildings and climates. By the theoretical calculation of moisture needed to be removed in three types of buildings (offices, residential buildings and restaurants) and the analysis of the dehumidification capacity of Desiccants in DCHEs reported in the literature, optimal Desiccants for different building types and ambient air conditions under given parameters are recommended. Salt-supported porous composite Desiccants possess flexible dehumidification performance and can be utilized in most climates and building types, except for extremely humid indoor environments with high requirement for fresh air. Zeolites are especially suitable for return air states, American Air-Conditioning and Refrigeration Institute (ARI) summer and ARI humid climates in buildings with moderate indoor moisture gain, such as offices or residential buildings. Polyelectrolytes can be applied in humid climates and buildings with high indoor wet loads, such as restaurants. This paper offers a promising route to the applications of desiccant materials in novel energy-saving air conditioning technologies.
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Investigation on energy consumption of desiccant coated heat exchanger based heat pump: Limitation of adsorption heat of desiccant
Energy Conversion and Management, 2019Co-Authors: X Zheng, R. Z. Wang, Y.d. TuAbstract:Abstract DCHE (Desiccant coated heat exchanger) based heat pump systems can handle sensible and latent loads simultaneously and separately within one single component via flowing refrigerant and coated desiccant. Their characteristics have a crucial impact on the performance of the whole system. To ensure energy efficiency of DCHE based systems, the restriction between refrigerant and desiccant is discussed based on energy consumption analysis. Results show that energy consumption of the DCHE based heat pump is intimately related with its coefficient of performance and adsorption heat of coated desiccant. R410A and R32 are found to be promising refrigerants for DCHE systems. Maximum allowable values of adsorption heat under different ambient air conditions and sensible heat ratios are obtained. Desiccant materials with adsorption heat of 2300–3000 kJ/kg such as various silica gels, all-silica zeolites and salt supported composites are within maximum allowable values of adsorption heat for most conditions. When applying the majority of zeolite type Desiccants that possess adsorption heat more than 4000 kJ/kg, great attention should be paid to the determination of supply-air temperature difference. This paper provides the underlying insights needed to guide a fast and proper selection of refrigerants and Desiccants for DCHE based systems.
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experimental study and performance predication of carbon based composite Desiccants for desiccant coated heat exchangers
International Journal of Refrigeration-revue Internationale Du Froid, 2016Co-Authors: X Zheng, R. Z. Wang, T.s. GeAbstract:Abstract A DCHE (desiccant coated heat exchanger) is a novel solid desiccant cooling component with desiccant coated onto the surface of a fin-tube heat exchanger. In the paper, carbon based composite Desiccants were developed and studied for DCHE systems. Composite Desiccants were fabricated by impregnating LiCl into pores of activated carbon and activated carbon fiber. Due to impregnated salt, composite Desiccants were found to have smaller surface area and pore volume. Sorption isotherms were measured and simulated based on Polanyi potential theory. Water sorption isotherms showed that composite Desiccants possessed enhanced sorption quantity. Sorption kinetics was also investigated and fitted with the linear driving model. Composite Desiccants showed higher dynamic water uptakes and reasonable rate coefficients. Finally, to predict dehumidification performance of composite Desiccants in DCHE systems, a mathematical model was built. Simulation results showed that composite desiccant coated DCHEs can remove more moisture from the process air.
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performance study of sapo 34 and fapo 34 Desiccants for desiccant coated heat exchanger systems
Energy, 2015Co-Authors: X Zheng, T.s. Ge, R. Z. Wang, Liguo HuAbstract:A DCHE (desiccant coated heat exchanger) is a novel solid desiccant component with desiccant coated onto the surface of a fin-tube heat exchanger, in which desiccant coated aluminum-fin is an important part. It has an impact on overall performance of the whole desiccant cooling system. In this study, different zeolite-like powders (SAPO-34 and FAPO-34) coated aluminum sheets were fabricated. Their performance was tested and analyzed to investigate the feasibility in a DCHE system. Experimental values of surface area and pore parameters for desiccant coatings had a slight reduction because of the existence of binder solution. Adsorption kinetics indicated that the binder solution would not affect water adsorption capacity or adsorption kinetics of original desiccant powder. Moreover, SAPO-34 and FAPO-34 coated aluminum sheets had higher adsorption capacity than that of silica gel. Sorption isotherms were also measured and fitting equations were developed based on Polanyi principle. Finally, their dehumidification performance in DCHE systems was predicted with a mathematical model. Simulation results indicated that the DCHE prepared from FAPO-34 can have 2–3 times larger dehumidification capacity than those from SAPO-34 and silica gel at low regeneration temperatures.
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development and characterization of mesoporous silicate licl composite Desiccants for solid desiccant cooling systems
Industrial & Engineering Chemistry Research, 2015Co-Authors: X Zheng, T.s. Ge, L M Hu, R. Z. WangAbstract:Solid composite Desiccants are fabricated by impregnating LiCl into pores of SBA-15 and MCM-41 mesoporous silicates. In the study, characteristics including textural properties and equilibrium and dynamic water sorption were tested and analyzed. Research on nitrogen adsorption suggested that because of the impregnated salt, composite Desiccants were different from pure silicates. Sorption isotherms were measured and simulated based on Polanyi potential theory. Composite samples had water uptake much higher than that of pure hosts under low and middle relative pressure owing to mutual contribution of both physical and chemical sorption. Sorption kinetics were also tested and fitted with a linear driving force model. The composite desiccant prepared from SBA-15 exhibited higher dynamic sorption quantity and a reasonable diffusion rate constant. Finally, dehumidification performance of the composite desiccant in a novel solid desiccant cooling component was evaluated with a mathematical model. Simulation res...
X Zheng - One of the best experts on this subject based on the ideXlab platform.
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Investigation on energy consumption of desiccant coated heat exchanger based heat pump: Limitation of adsorption heat of desiccant
Energy Conversion and Management, 2019Co-Authors: X Zheng, R. Z. Wang, Y.d. TuAbstract:Abstract DCHE (Desiccant coated heat exchanger) based heat pump systems can handle sensible and latent loads simultaneously and separately within one single component via flowing refrigerant and coated desiccant. Their characteristics have a crucial impact on the performance of the whole system. To ensure energy efficiency of DCHE based systems, the restriction between refrigerant and desiccant is discussed based on energy consumption analysis. Results show that energy consumption of the DCHE based heat pump is intimately related with its coefficient of performance and adsorption heat of coated desiccant. R410A and R32 are found to be promising refrigerants for DCHE systems. Maximum allowable values of adsorption heat under different ambient air conditions and sensible heat ratios are obtained. Desiccant materials with adsorption heat of 2300–3000 kJ/kg such as various silica gels, all-silica zeolites and salt supported composites are within maximum allowable values of adsorption heat for most conditions. When applying the majority of zeolite type Desiccants that possess adsorption heat more than 4000 kJ/kg, great attention should be paid to the determination of supply-air temperature difference. This paper provides the underlying insights needed to guide a fast and proper selection of refrigerants and Desiccants for DCHE based systems.
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experimental study and performance predication of carbon based composite Desiccants for desiccant coated heat exchangers
International Journal of Refrigeration-revue Internationale Du Froid, 2016Co-Authors: X Zheng, R. Z. Wang, T.s. GeAbstract:Abstract A DCHE (desiccant coated heat exchanger) is a novel solid desiccant cooling component with desiccant coated onto the surface of a fin-tube heat exchanger. In the paper, carbon based composite Desiccants were developed and studied for DCHE systems. Composite Desiccants were fabricated by impregnating LiCl into pores of activated carbon and activated carbon fiber. Due to impregnated salt, composite Desiccants were found to have smaller surface area and pore volume. Sorption isotherms were measured and simulated based on Polanyi potential theory. Water sorption isotherms showed that composite Desiccants possessed enhanced sorption quantity. Sorption kinetics was also investigated and fitted with the linear driving model. Composite Desiccants showed higher dynamic water uptakes and reasonable rate coefficients. Finally, to predict dehumidification performance of composite Desiccants in DCHE systems, a mathematical model was built. Simulation results showed that composite desiccant coated DCHEs can remove more moisture from the process air.
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performance study of sapo 34 and fapo 34 Desiccants for desiccant coated heat exchanger systems
Energy, 2015Co-Authors: X Zheng, T.s. Ge, R. Z. Wang, Liguo HuAbstract:A DCHE (desiccant coated heat exchanger) is a novel solid desiccant component with desiccant coated onto the surface of a fin-tube heat exchanger, in which desiccant coated aluminum-fin is an important part. It has an impact on overall performance of the whole desiccant cooling system. In this study, different zeolite-like powders (SAPO-34 and FAPO-34) coated aluminum sheets were fabricated. Their performance was tested and analyzed to investigate the feasibility in a DCHE system. Experimental values of surface area and pore parameters for desiccant coatings had a slight reduction because of the existence of binder solution. Adsorption kinetics indicated that the binder solution would not affect water adsorption capacity or adsorption kinetics of original desiccant powder. Moreover, SAPO-34 and FAPO-34 coated aluminum sheets had higher adsorption capacity than that of silica gel. Sorption isotherms were also measured and fitting equations were developed based on Polanyi principle. Finally, their dehumidification performance in DCHE systems was predicted with a mathematical model. Simulation results indicated that the DCHE prepared from FAPO-34 can have 2–3 times larger dehumidification capacity than those from SAPO-34 and silica gel at low regeneration temperatures.
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development and characterization of mesoporous silicate licl composite Desiccants for solid desiccant cooling systems
Industrial & Engineering Chemistry Research, 2015Co-Authors: X Zheng, T.s. Ge, L M Hu, R. Z. WangAbstract:Solid composite Desiccants are fabricated by impregnating LiCl into pores of SBA-15 and MCM-41 mesoporous silicates. In the study, characteristics including textural properties and equilibrium and dynamic water sorption were tested and analyzed. Research on nitrogen adsorption suggested that because of the impregnated salt, composite Desiccants were different from pure silicates. Sorption isotherms were measured and simulated based on Polanyi potential theory. Composite samples had water uptake much higher than that of pure hosts under low and middle relative pressure owing to mutual contribution of both physical and chemical sorption. Sorption kinetics were also tested and fitted with a linear driving force model. The composite desiccant prepared from SBA-15 exhibited higher dynamic sorption quantity and a reasonable diffusion rate constant. Finally, dehumidification performance of the composite desiccant in a novel solid desiccant cooling component was evaluated with a mathematical model. Simulation res...
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Development and Characterization of Mesoporous Silicate–LiCl Composite Desiccants for Solid Desiccant Cooling Systems
Industrial & Engineering Chemistry Research, 2015Co-Authors: X Zheng, L M Hu, Tianshu Ge, Ruzhu WangAbstract:Solid composite Desiccants are fabricated by impregnating LiCl into pores of SBA-15 and MCM-41 mesoporous silicates. In the study, characteristics including textural properties and equilibrium and dynamic water sorption were tested and analyzed. Research on nitrogen adsorption suggested that because of the impregnated salt, composite Desiccants were different from pure silicates. Sorption isotherms were measured and simulated based on Polanyi potential theory. Composite samples had water uptake much higher than that of pure hosts under low and middle relative pressure owing to mutual contribution of both physical and chemical sorption. Sorption kinetics were also tested and fitted with a linear driving force model. The composite desiccant prepared from SBA-15 exhibited higher dynamic sorption quantity and a reasonable diffusion rate constant. Finally, dehumidification performance of the composite desiccant in a novel solid desiccant cooling component was evaluated with a mathematical model. Simulation res...
A A Alfarayedhi - One of the best experts on this subject based on the ideXlab platform.
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evaluation of heat and mass transfer coefficients in a gauze type structured packing air dehumidifier operating with liquid desiccant
International Journal of Refrigeration-revue Internationale Du Froid, 2002Co-Authors: A A Alfarayedhi, Palanichamy Gandhidasan, M A AlmutairiAbstract:Abstract In this paper, high performance packing, namely, structured packing that has good heat and mass transfer characteristics, is proposed for dehumidification of air using liquid Desiccants and for regeneration of liquid Desiccants. In order to design a structured packing tower for liquid desiccant — air contacting operations, heat and mass transfer coefficients for each phase are required. This paper is concerned with the interface transfer of heat and mass when air is brought into contact with the liquid desiccant solution. A theoretical study of evaluating heat and mass coefficients in an air-desiccant contact system employing three liquid Desiccants, namely calcium chloride, lithium chloride, and a mixture of 50% calcium chloride and 50% lithium chloride (called cost effective liquid desiccant, CELD) is investigated. Moreover, air phase transfer coefficients are correlated with flow rates of air and liquid and the temperature of air, whereas liquid phase coefficients are correlated with rates of air and liquid flow, and the temperature and concentration of the liquid. The findings for the three liquid Desiccants are compared and discussed.
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regeneration of liquid Desiccants using membrane technology
Energy Conversion and Management, 1999Co-Authors: A A Alfarayedhi, P Gandhidasan, Younus S AhmedAbstract:Liquid Desiccants used for many industrial and domestic applications have to be reconcentrated for reuse. Instead of using thermal energy, a method is proposed in this paper to use mechanical energy for regeneration of weak Desiccants. The osmotic pressure required to regenerate two such Desiccants, namely calcium chloride and lithium chloride, for given operating conditions is predicted, and correlations are developed. It is found that the pressure required for calcium chloride is much less than that of lithium chloride for the same operating conditions.
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thermodynamic analysis of liquid Desiccants
Solar Energy, 1998Co-Authors: Younus S Ahmed, Palanichamy Gandhidasan, A A AlfarayedhiAbstract:Liquid Desiccants are widely used in many solar applications. In order to analyze the performance of the system using desiccant technology, the thermophysical properties of Desiccants are essential. In particular, the vapor pressure of the liquid desiccant is one of the important properties in air dehumidification. In this paper, an attempt is made to predict this property based on a classical thermodynamics approach and it is found that the predicted values for lithium chloride agree very well with the experimental results. The desired sorption properties can also be obtained by mixing the Desiccants, which is another method of developing a new cost-effective liquid desiccant. In this paper, simple mixing rules are used to predict the vapor pressure, density, and viscosity of the desiccant mixture, namely calcium chloride and lithium chloride. It is found that the interaction parameter need not be included in calculating the density and vapor pressure of the above mixture but must be included in predicting the viscosity.
T.s. Ge - One of the best experts on this subject based on the ideXlab platform.
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experimental study and performance predication of carbon based composite Desiccants for desiccant coated heat exchangers
International Journal of Refrigeration-revue Internationale Du Froid, 2016Co-Authors: X Zheng, R. Z. Wang, T.s. GeAbstract:Abstract A DCHE (desiccant coated heat exchanger) is a novel solid desiccant cooling component with desiccant coated onto the surface of a fin-tube heat exchanger. In the paper, carbon based composite Desiccants were developed and studied for DCHE systems. Composite Desiccants were fabricated by impregnating LiCl into pores of activated carbon and activated carbon fiber. Due to impregnated salt, composite Desiccants were found to have smaller surface area and pore volume. Sorption isotherms were measured and simulated based on Polanyi potential theory. Water sorption isotherms showed that composite Desiccants possessed enhanced sorption quantity. Sorption kinetics was also investigated and fitted with the linear driving model. Composite Desiccants showed higher dynamic water uptakes and reasonable rate coefficients. Finally, to predict dehumidification performance of composite Desiccants in DCHE systems, a mathematical model was built. Simulation results showed that composite desiccant coated DCHEs can remove more moisture from the process air.
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performance study of sapo 34 and fapo 34 Desiccants for desiccant coated heat exchanger systems
Energy, 2015Co-Authors: X Zheng, T.s. Ge, R. Z. Wang, Liguo HuAbstract:A DCHE (desiccant coated heat exchanger) is a novel solid desiccant component with desiccant coated onto the surface of a fin-tube heat exchanger, in which desiccant coated aluminum-fin is an important part. It has an impact on overall performance of the whole desiccant cooling system. In this study, different zeolite-like powders (SAPO-34 and FAPO-34) coated aluminum sheets were fabricated. Their performance was tested and analyzed to investigate the feasibility in a DCHE system. Experimental values of surface area and pore parameters for desiccant coatings had a slight reduction because of the existence of binder solution. Adsorption kinetics indicated that the binder solution would not affect water adsorption capacity or adsorption kinetics of original desiccant powder. Moreover, SAPO-34 and FAPO-34 coated aluminum sheets had higher adsorption capacity than that of silica gel. Sorption isotherms were also measured and fitting equations were developed based on Polanyi principle. Finally, their dehumidification performance in DCHE systems was predicted with a mathematical model. Simulation results indicated that the DCHE prepared from FAPO-34 can have 2–3 times larger dehumidification capacity than those from SAPO-34 and silica gel at low regeneration temperatures.
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development and characterization of mesoporous silicate licl composite Desiccants for solid desiccant cooling systems
Industrial & Engineering Chemistry Research, 2015Co-Authors: X Zheng, T.s. Ge, L M Hu, R. Z. WangAbstract:Solid composite Desiccants are fabricated by impregnating LiCl into pores of SBA-15 and MCM-41 mesoporous silicates. In the study, characteristics including textural properties and equilibrium and dynamic water sorption were tested and analyzed. Research on nitrogen adsorption suggested that because of the impregnated salt, composite Desiccants were different from pure silicates. Sorption isotherms were measured and simulated based on Polanyi potential theory. Composite samples had water uptake much higher than that of pure hosts under low and middle relative pressure owing to mutual contribution of both physical and chemical sorption. Sorption kinetics were also tested and fitted with a linear driving force model. The composite desiccant prepared from SBA-15 exhibited higher dynamic sorption quantity and a reasonable diffusion rate constant. Finally, dehumidification performance of the composite desiccant in a novel solid desiccant cooling component was evaluated with a mathematical model. Simulation res...
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experimental study on silica gel licl composite Desiccants for desiccant coated heat exchanger
International Journal of Refrigeration-revue Internationale Du Froid, 2015Co-Authors: X Zheng, T.s. Ge, Yu Jiang, R. Z. WangAbstract:Abstract Desiccant coated aluminum-fin is an important part in desiccant coated heat exchanger (DCHE). It will affect the overall performance of this novel solid desiccant component. In the paper, different silica gel-LiCl composite desiccant coated aluminum sheets were fabricated and some key parameters were studied. Nitrogen adsorption suggested that texture properties of composite Desiccants were different from silica gel due to impregnated salt and combined action of silica sol and silica gel. The highest thermal conductivity of composite sheets was 5.8 Wm−1K−1, which is twice of silica gel coated one. Sorption kinetics indicated that composite sheets exhibited higher dynamic sorption quantities and faster sorption rates. Sorption isotherms were also obtained and fitted with Dubinin–Astakhov equation. Besides, dehumidification capacity of composite DCHE was tested and compared with silica gel one. Results indicated that enhanced dehumidification capacity can be achieved with use of composite desiccant in the DCHE system.
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Recent progress on desiccant materials for solid desiccant cooling systems
Energy, 2014Co-Authors: Xin Qian Zheng, T.s. Ge, R. Z. WangAbstract:SDC (Solid desiccant cooling) systems have gained increasing interest as an alternative air conditioning technology. Performance of desiccant plays a crucial role in overall performance of the whole system, especially in terms of dehumidification and regeneration capacity. It is desirable to explore desiccant possessing high adsorption capacity and good regeneration ability. Thus, this review summarizes recent researches and developments on novel solid desiccant materials that can be adopted in SDC systems. The materials include composite Desiccants, nanoporous inorganic materials and polymeric Desiccants. Adsorption isotherms are concluded and compared. Regeneration ability is also considered for full use of low grade thermal energy. Results show that by proper selection of host matrix and immersed salts, composite Desiccants have improved capacity of dehumidification and regeneration. Besides, a good balance can be reached between regeneration and adsorption capacity by tailoring textural properties of nanoporous inorganic materials. For polymeric Desiccants, especially MIL type (materials of Institute Lavoisier Frameworks), further progress in adsorptive dehumidification will be anticipated. Though some novel materials approach requirements for SDC systems, no material currently available can perfectly satisfy all the required demands. In this case, more intensive researches in the field of development and evaluation of advanced materials are still required.
K J Chua - One of the best experts on this subject based on the ideXlab platform.
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a review of metal organic frameworks mofs as energy efficient Desiccants for adsorption driven heat transformation applications
Applied Energy, 2020Co-Authors: Avishek Karmakar, Vivekh Prabakaran, Dan Zhao, K J ChuaAbstract:Abstract Energy-efficient alternative cooling technologies are necessary to reduce the sharp rise in building energy requirements. The currently employed vapor compression air-conditioners are non-environmentally friendly and exhibit low efficiency due to the concurrent handling of sensible and latent cooling loads. Adsorption chillers and desiccant dehumidifiers are promising alternatives that can trim the overall carbon footprint. Their cooling energy efficiency is dependent on the adsorption characteristics of the employed Desiccants. Conventional Desiccants suffer from low equilibrium capacity, slow adsorption-desorption dynamics, the needs for high regeneration temperatures, and the lack of hydrothermal and cyclic stabilities. With excellent hydrophilicity, exceptional structural integrity, and specific host-guest interactions, metal-organic frameworks (MOFs) are deemed to be the next generation of advanced materials with tailorable structures for specific applications. In this review article, we focus on the recent developments in MOFs and their potential employment in several state-of-the-art applications such as heat transformation, energy storage, and water harvesting. The advantages of MOFs over conventional pure and composite desiccant materials are discussed, and the key factors necessary for synthesizing stable MOFs are reviewed comprehensively. The experimental and computational characterization techniques employed to investigate the properties of MOFs are studied. Lastly, factors that are essential to screen MOFs for specific applications are analyzed, and key research gaps and technological advancements pertaining to material development and engineering demands are also highlighted. In sum, this review article offers an extensive update on the latest trends in water-sorbing MOFs and is intended to serve as a one-stop archive for its potential applicability.
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heat and mass transfer of composite Desiccants for energy efficient air dehumidification modelling and experiment
Applied Thermal Engineering, 2015Co-Authors: K J ChuaAbstract:Abstract Desiccant dehumidification technology provides a method of drying air before it enters a conditioned space. When combined with conventional cooling systems, desiccant dehumidification provides an energy-efficient way of supplying thermal comfort air. This paper presents a combined experimental–analytical study on the heat and mass transfer dynamics of composite Desiccants during air dehumidification. The composite Desiccants are silica gel–calcium chloride, silica gel–lithium chloride, and silica gel–polyvinyl alcohol (PVOH). The derived model is validated against experimental observations of different desiccant types with silica-gel as the host desiccant. Predictions are shown to agree well with extensive experimental measurements conducted using an in-house experimental setup as well as data published in the literature. Experiments were conducted on several promising composite Desiccants. The effects of process air velocity, inlet air temperature and humidity on moisture removal capacity, regeneration rates and the associated pressure drops were investigated. Relying on a holistic energy performance index, desiccant coefficient of performance (DCOP), results have indicated that the moisture removal capacity, regeneration rates and the associated pressure drops of composite Desiccants outperformed that of pure silica gel by at least 11%.