Theoretical performance assessment of low-GWP refrigerant R1233zd(E) applied in high temperature heat pump system

With the enactment of the Kigali amendment regarding the phase-down of substances with Global Warming Potential (GWP), refrigerants based on HFCs are falling into disuse and low-GWP refrigerants are proposed as replacements. R1233zd(E) is a promising new working fluid for High-temperature Heat Pumps (HTHPs) with low GWP which has yet to be further developed. A proper model needs to be imperatively constructed to predict the characteristics of R1233zd(E) applied in HTHPs. This paper proposes a mathematical model of two-stage compression and vapor injection heat pump system, and analyzes the compression ratio, injection mass flow rate, power consumption, discharge temperature, heating capacity and Coefficient of Performance (COP) under variable working conditions. When recovering 50 °C waste heat and supplying 60–130 °C hot water, the heating capacity increases from 2.09 to 2.22 MW and the COP decreases from 23 to 2.93. When recovering 80 °C waste heat and supplying 90–160 °C hot water, the heating capacity increases from 4.11 to 4.23 MW and the COP decreases from 24.4 to 2.7. The detailed model of heat exchangers can demonstrate the inner heat transfer process clearly, such as refrigerant temperature and gas content ratio, which would be instructive for component optimization. The above results indicate that the studied R1233zd(E)-based HTHP has excellent performance and broad application prospects, which plays a positive role in further development of HTHPs.