Research on geothermal-driven single-effect absorption refrigeration systems with different working fluids: energy and exergy analysis

Abstract

Abstract Geothermal energy is not only environmentally friendly and has low carbon but also represents a nonintermittent technology. It is anticipated that its utilization in human society will experience rapid growth in the coming decades. Absorption refrigeration can be employed for the recovery of geothermal resources. However, the low performance of absorption refrigeration systems has hindered their development. In order to advance absorption refrigeration technology suitable for geothermal energy recovery, this study developed a mathematical model for an absorption refrigeration system using 55% lithium bromide (LiBr) and 35% lithium chloride (LiCl) solutions as working fluids. The impact of various parameters, including cooling water conditions, chilled water conditions, heat source parameters, and working fluid concentration, on the thermodynamic performance, system efficiency, and exergy efficiency of a single-effect absorption refrigeration system was analyzed. The results reveal that the cooling water inlet temperature and flow, chilled water inlet temperature, heat source inlet temperature, and working fluid concentration are the primary factors affecting the thermodynamic performance and exergy efficiency of the absorption refrigeration system. The coefficient of performance (COP) of the system increases with higher cooling water flow, chilled water inlet temperature, and working fluid concentration, but decreases with higher cooling water inlet temperature. Within a certain temperature range, the COP increases with higher heat source temperature. The effective COP (ECOP) increases with higher cooling water inlet temperature, cooling water flow, chilled water inlet temperature, and working fluid concentration, while it decreases with higher heat source temperature. The highest COP values for the LiBr and LiCl solution single-effect absorption refrigeration systems are 0.795 and 0.785, respectively, while the highest ECOP values are 0.694 and 0.684, respectively.