Performance evaluation of a low-temperature waste heat driven multi-bed adsorption chiller

Abstract

This study aims at improving the performance of thermally activated silica gel–water adsorption refrigeration cycle by applying multi-bed scheme. In this paper, a three-bed non-regenerative silica gel–water adsorption chiller design is outlined along with the performance evaluation of the innovative chiller. The three-bed chiller will be able to work as high efficient single-stage adsorption chiller where driving source temperature is between 60 and 95 °C along with a coolant at 30 °C. The three-bed cycle comprises with three adsorber/desorber heat exchangers, one evaporator and one condenser. Waste heat or renewable energy sources will power the high temperature desorber. If two beds are in desorption mode, the hot water outlet from the lead desorber will drive the lag desorber before being released to ambient. This facilitates the maximum utilization of the waste stream. On the contrary, if two adsorber or desorber beds are in adsorption mode, the cooling water outlet from the lead adsorber will cool down the lag adsorber. In this circumstance, two adsorber beds will be connected with the evaporator and will enhance evaporation. A cycle simulation computer program is developed to analyze the influence of operating temperatures (hot and cooling water temperatures, adsorption/desorption cycle time) on cooling capacity and coefficient of performance (COP) of the innovative three-bed cycle in parallel flow configuration of the heat transfer fluids. The cycle simulation calculation indicates that the COP value of the three-bed chiller is 0.38 with a driving source temperature at 80 °C in combination with coolant inlet and chilled water inlet temperatures at 30 and 14 °C, respectively. The delivered chilled water temperature is about 6 °C with this operation condition. Simulation results also show that from the two to three beds, waste heat recovery efficiency, η is boosted by about 35%.