High temperature heat pumps – Theoretical study on low GWP HFO and HCFO refrigerants

High temperature heat pumps with heat sink temperatures of 100 to 160 °C have great application potential in the food, paper, and chemical industries for heat recovery and process heat generation in drying, sterilization, and evaporation processes. The present study compares the theoretical performance of the low GWP refrigerants R1336mzz(Z), R1224yd(Z), R1234ze(Z), and R1233zd(E) in common one- and two-stage heat pump cycles (IHX, economizer, flash tank, cascade) at different temperature levels. The thermodynamic simulations reveal that, depending on the refrigerant and cycle, a trade-off between system complexity (e.g. control, number of components), efficiency, and volumetric heating capacity (VHC) has to be found. Optimal COPs are reached depending on the refrigerant and its heat outlet temperature. R1336mzz(Z) is suggested as the closest drop-in replacement for R365mfc, while R1224yd(Z), R1234ze(Z), and R1233zd(E) are closer to R245fa in terms of COP and VHC. A two-stage cascade with IHX and R1336mzz(Z) in both stages achieved the highest COP for high temperature lifts.