Energy performance evaluation of two-phase injection heat pump employing low-GWP refrigerant R32 under various outdoor conditions

Abstract The refrigerant R32 has been receiving significant attention as an alternative to R410A used in heat pumps, owing to its lower global warming potential. The two-phase injection (TPI) technique is introduced to achieve improved energy performance along with high system reliability in R32 heat pumps, owing to their high discharge temperature. The objectives of this study are to compare the performances as well as reliabilities of the R32 and R410A TPI heat pumps and provide the design guidelines for achieving the best performance with safe operation. The performances of the R32 and R410A TPI heat pumps are measured by varying compressor frequency and outdoor temperature. The TPI technique enables the R32 heat pump to operate at a higher compressor frequency under severe weather conditions. At low outdoor temperatures of –10 °C and –15 °C, the R32 TPI heat pump demonstrates a superior heating capacity and coefficient of performance (COP) compared with the R410A TPI heat pump. In addition, the injection parameters in the R32 TPI heat pump are optimized under various operating conditions.