Performance evaluation of a two-stage air-cooled silica gel + water adsorption cooling system: Effect of key operational parameters

Abstract

The primary objective of this work is to extract some design criteria of the upper-stage adsorber bed in a two-stage two-bed adsorption cooling system. The second objective is to experimentally investigate the effects of air-cooled heat sink, and hot water source temperatures on the chiller performance. These studies are important as the adsorber bed design together with the input operational parameters determines the chiller performance. It was observed that the performance indicators, namely, cooling capacity (CC) and coefficient of performance (COP) exhibit opposite trends with the reduction in the temperature of the sink where heat of adsorption is rejected. The performance parameters are evaluated for heat source temperatures in the range of 75–85 °C against different half-cycle times. The CC and COP are found to vary between 148 - 324 W and 0.09–0.11 respectively depending on the heat source temperature and half cycle time. The novelty of the present work is in providing experimental evidence on influence of heat source temperatures on two-stage adsorption chillers when air cooling is adopted for all heat rejections to the ambient. Another key finding is that the upper stage performance is critical because of smaller volume and lower heat transfer area available in it compounded by higher uptake differences across which it operates.