SOLID DESICCANT-VAPOR COMPRESSION HYBRID COOLING SYSTEM WITH CONDENSER EXHAUST RECOVERY

Abstract

Desiccant assisted air conditioning systems are considered as the best alternative for hot and humid regions compared to conventional cooling system such as vapor compression refrigeration cooling system. This is due to their environment friendly nature as they eliminate the use of chlorofluorocarbons (CFCs) which are one of the major responsible causes in depletion of ozone layer. Further, desiccant cooling system is cost effective when used with waste heat source for regeneration of the system. The objectives of the thesis consist of ➢ Experimental investigation for solid desiccant - vapor compression hybrid cooling system without and with heat recovery from condenser exhaust. ➢ Mathematical model for effective start of dehumidification process and theoretical prediction of steady state temperature profile inside the porous channels of desiccant wheel along its length and finally. ➢ Development of mathematical model and its validation with the experimental results for unavoidable mixing phenomenon occurring due to rotation between two counter flowing fluids in heat recovery wheel. Experimental investigation starts with the usual solid desiccant-vapour compression hybrid cooling system without heat recovery from condenser exhaust to have the initial practical understanding of experimental set up. Factors affecting the performance, purpose and working behaviour of the system have been investigated. Unavoidable mass transfer in heat wheel, regeneration temperature and moisture content in regeneration air before entering to the desiccant wheel, dew point temperature (DPT) of air entering to the cooling coil of vapor compression refrigeration (VCR) unit and the modes of system (ventilation or recirculation) have been observed to have significant impacts. Next, experimental approach for solid desiccant - vapour compression hybrid cooling system with useful utilization of condenser exhaust heat recovery has been carried out to investigate the performance of such cooling systems for hot and humid climate for different values of regeneration temperatures for both modes of operations (ventilation and recirculation). Intuitive analytical approach backed up with derivations of mathematical relations starting with the help of fundamental governing equations along with explanations by psychrometric chart, provide us a new look towards dehumidification process that takes place inside the parallel porous passages of rotating solid desiccant wheel on process side when humid air allowed to pass through these. A hypothesis has been put forth and the interpretations of mathematical relations derived, mutually support each other’s claim in explaining the physical mechanism associated with dehumidification process. This research work brings a new insight