Exergy analysis of combined absorption-compression heat pump with ammonia-water mixture as working fluid.

In this paper, investigations on the development of industrial high temperature heat pumps are carried out based on the exergy analysis of different compressor configurations. The combined absorption-compression heat pump (CACHP) combines technologies of an absorption and vapor compression heat pump with an ammonia-water mixture as refrigerant. In this study, an exergy analysis of a CACHP system with different operating conditions is investigated with the aim to identify possible compressor configurations for the development of a CACHP test facility that can operate at high pressure levels and achieve heat sink outlet temperatures of around 120 °C. Simulations with different compressor configurations with respect to the amount of lean solution injected into the ammonia vapor compression process are performed. Subsequently, an exergy analysis is conducted for all components within the CACHP cycle. Main sources of irreversibility were identified and the effect of the injection was investigated. The results demonstrated that besides reducing the compressor discharge temperature, liquid injection can improve the overall system efficiency.