الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
The electric energy demand by HVAC systems in the buildings sector, both residential and commercial, is in persistent increase and accounts for nearly 37% of the total electricity consumption of this sector worldwide. Accordingly, many scholars have recently introduced liquid desiccant (LD) air-conditioning systems as an alternative solution for conventional vapor compression air conditioning systems in high moisture removal applications. The previous studies showed that up to 30% reduction in energy consumption could be achieved. This is due to extracting the moisture from air using the difference in water vapor pressure between liquid desiccant and air in LD systems, instead of deep cooling under the dew point temperature in conventional systems. In this study, a new configuration for a heat-and-mass energy exchanger is proposed to enhance the performance of LD systems. The new exchanger is a modified liquid-to-air membrane energy exchanger (LAMEE), where evaporator/condenser coils of a heat pump are embedded in the liquid desiccant channels. The modified LAMEE utilizes thermal energy of evaporating/condensing refrigerant to control LD temperature along the solution channels at desired points, for cooling/regeneration purposes. The new module is designed to be functioned in a heat pump liquid desiccant (HPLD) air conditioning system, where two units of the novel membrane energy exchangers are used in the system. The first energy exchanger is used to cool and dehumidify the process air, using the evaporator coils embedded in the low moisture content LD channels. While the second energy exchanger is used to release the moisture gained in the LD by the first energy exchanger into the exhaust air, using the condenser coils embedded in the high moisture content LD channels. A detailed mathematical model of the proposed unit has been presented, then it has been extended to simulate the whole HPLD system. Accordingly, the performance has been investigated at a system level, not for a standalone module, in which the two energy exchangers were simultaneously modeled using a numerical approach considering the effect of the embedded heat pump circuit. The numerical model was defined and solved using COMSOL Multiphysics software. In this modeling, the real conjugate boundary conditions between domains were considered, for each new energy exchanger. The validation of developed model in this study was examined using experimental results of a published work, and a good agreement was attained. II The design operating conditions of extreme relative humidity in Sharm El Sheikh, Egypt, were used as a case study. The proposed energy exchangers and the overall system attained high energy efficiency with outstanding dehumidification capability. It was found that, fresh air at (30°C, 19 g/kg) was cooled and dehumidified to (20.18°C, 6.52 g/kg) with system coefficient of performance (𝐶𝑂𝑃𝑠𝑦𝑠𝑡𝑒𝑚) as high as 6.38 and HP energy efficiency ratio (EER) as high as 14.88. Moreover, much higher dehumidification capacities were reachable by varying the key operating parameters at the expense of 𝐶𝑂𝑃𝑠𝑦𝑠𝑡𝑒𝑚.