Hybrid absorption-compression heat pump with two-stage rectification and subcooler

Abstract

Conventional hybrid absorption-compression heat pumps are difficult to efficiently upgrade waste heat to a heating temperature of above 90 °C. In this paper, to solve this problem, two novel approaches, namely a two-stage rectification and a subcooler, are specially proposed for the hybrid heat pump. By designing a two-stage rectification to reduce the suction temperature of compressor, thereby lowering its discharge temperature, commercially available normal-temperature compressors can be employed in the hybrid heat pump for high-temperature heating. By utilizing a subcooler proposed to reduce the irreversible loss during the throttling process, the energy efficiency of the hybrid heat pump is improved. Moreover, the hybrid heat pump with multi-stage subcoolers is also proposed and analyzed. Thermodynamic analysis exhibits that, at a heating temperature of 120 °C and a solution heat exchanger effectiveness of 0.8, the hybrid heat pump with a two-stage rectification and a subcooler brings about an energy efficiency improvement of 17.4% in comparison to the conventional one.