Influence of cycle time and collector area on solar driven adsorption chillers

Abstract

Dynamic performance of a single-stage, two-bed, silica gel+water adsorption chiller operating in Bangalore, India is studied. Driving thermal energy is provided directly by an evacuated tube solar collector field. System dynamics are evaluated in the absence of thermal storage, which causes intra-day fluctuations in heat source and evaporator temperatures, which in turn influence the system performance. These dynamics are demonstrated for representative days in the months of April (summer) and December (winter). The focus is on the effect of variation of the collector area and the adsorption cycle time on the system performance. The maximum temperature of heat transfer fluid (water) is limited to 95°C. The cyclic and daily averages of solar coefficient of performance (DACOPsol) and cooling capacity (DACC) are used as key performance indicators. One of the key aspects of the this study is to show that both of them can be maximized by suitably choosing the collector area and cycle time. Further, it is demonstrated that the solar driven adsorption chiller described here is ideally suited for cascading with an air-cooled R-134a vapour compression refrigeration system (VCRS). The variable throughput obtained from the solar adsorption chiller can help in liquid sub-cooling and hence to cover the deficit in cooling capacity of the VCRS arising due to high ambient temperature.