18 May 2017
In this paper, the system simulation and exergy analysis of multi-stage compression high temperature heat pump (HTHP) systems with R1234ze(Z) working fluid are conducted. Both the single-stage and multi-stage compression cycles are analysed to compare the system performance with 120°C pressurized hot water supply based upon waste heat recovery. Energy and exergy efficiencies of the systems are calculated to study the influences of operating conditions on the system performance. Variation of the HTHP performance with increasing waste heat source temperature is investigated. The exergy destruction ratios of every component for different stage compression systems are compared. The results showed the exergy loss ratios of compressor is big than that of evaporator and condenser for single-stage compression system. The multi-stage compression system has better energy and exergy efficiencies with the increase of compression stage number. Compared with single-stage compression system, the COP improvements of two-stage and three-stage compression system are 9.1% and 14.6%, respectively. When the waste heat source temperature is 60°C, the exergy efficiency increase about 6.9% and 11.8% for two-stage and three-stage compression system respectively.