Experimental study on CO2/R32 blends in a water-to-water heat pump system

The purpose of this study is to evaluate the cooling and heating performance as well as the compressor operating conditions of CO2/R32 blends in a water-to-water heat pump system. Experiments were conducted to reveal the effects of the refrigerant compositions, heat source temperatures, and internal heat exchanger (IHX) on the performance of the system. The results show that 23.3% and 65.2% maximum improvement in heating coefficient of performance (COPh) and cooling coefficient of performance (COPc) of the system were obtained when the mass fraction of CO2 was 0.6, respectively. Meanwhile, heating capacity, cooling capacity, and the compressor discharge pressure of CO2/R32 blends were decreased significantly. The thermal matching between the heat source and CO2/R32 blends significantly affected the overall performance of the system. In addition, IHX is recommended in the water-to-water heat pump to improve the system performance.