Thermodynamic analysis of a high-temperature heat pump using R1233zd(E) refrigerant with multi-stage-evaporation/compression

The temperature mismatch between the hot and cold fluids in the evaporator is the fundamental reason for the low thermodynamic efficiency of waste heat-driven high-temperature heat pumps. To tackle this issue, this paper analyzed the thermodynamic performance of a high-temperature steam heat pump system using R1233zd(E) refrigerant with multi-stage-evaporation/compression by means of EBSILON software simulation. The thermodynamic performance of each configuration is also assessed through coupling regenerative and flash processes. It is found that under the conditions of a fixed-temperature heat source (70 °C) and a heat sink (140 °C), the high-temperature steam heat pump with a dual-stage-evaporation/dual-stage-compression/regeneration configuration achieves the highest coefficient of performance (COP) of 2.804, with the corresponding exergy efficiency reaching up to 91.8%. Through analyzing the heat transfer characteristics, it is found that the COP is negatively correlated with the average temperature matching factor (ATMF) of all the heat exchangers in the system. For the high-temperature steam heat pump system with multi-stage-evaporation/compression configuration, optimal performance is achieved when the minimum ATMF is 1.117. The research results can provide theoretical guidance for the prototype development of the 140 °C high-temperature steam heat pump driven by waste heat.