Experiment and simulation study on performances of heat pump water heater using blend of R744/R290

The feasibility of applying natural eco-friendly blend of R744 (CO2) with R290 (propane) in a heat pump water heater (HPWH) system with large heat sink temperature lift was presented. The experiment and simulation investigations on the performances of the HPWH system using the R744/R290 blend and the one using R22 were carried out under variable operating conditions by using the water-water heat pump test rig and theoretical model, respectively. The experiment and simulation results indicate that the blend R744/R290 with mass fraction of 12%/88%, Mopt for short, is the appropriate substitute refrigerant for R22 in the HPWH system mainly because of its excellent performances such as superior heating COP and heating capacity and much lower compressor discharge temperature, etc. The heat source inlet temperature has striking effects on both the heating COP and the heating capacity, and the heat sink temperature lift has an obvious impact on heating COP but little impact on heating capacity.