HFOs, Heat Pump, Water Heating, Refrigerants
Recently there has been a growing interest in utilization of alternative refrigerants for residential and commercial HVAC&R systems due to the potential environmental impacts of conventional fluids (CFCs and HFCs). Hydrofluoroolefins such as R1234yf and R1234ze(E) has shown promising performance and are being extensively considered for range of heat pump applications. This study illustrates the performance evaluation of R1234yf and R1234ze(E) as drop-in-replacement for R134a for heat pump water heating (HPWH). A component-based model is used to predict the performance. Key performance parameters such as unified energy factor, first hour rating and thermal stratification in the water tank are investigated. Along with system modeling appropriate experiments to demonstrate the performance improvements. Both modeling and experimental efforts suggest that HFOs when deployed as alternative refrigerants can provide comparable system performance to that of the baseline system containing R134a. Other concerning parameters such as total system refrigerant charge, the condenser discharge temperature and thermal stratification in water storage tank are established to investigate the potential retrofit of the system to further improve the performance of the system.