Alternative refrigerants, Hydrocarbons, hydroflourocarbon
Growing awareness of the potential environmental impacts of conventional refrigerants (CFCs and HFCs) has led to efforts to identify suitable alternative refrigerants for various heat pump applications with minimum environmental impact. This study is focused on the performance evaluation of various alternatives including hydrocarbon (HC), hydroflouroolefins (HFO), and CO2 as drop-in-replacement for R134a for heat pump water heating (HPWH). Fundamental thermophysical properties have been used to highlight the important performance characteristics of the systems when such fluids are deployed working medium. Key performance parameters such as unified energy factor, first hour rating and thermal stratification in the water tank are investigated using simulation and experimental approaches. The findings suggest that both alternative refrigerants could provide comparable system performance to that of the baseline system containing R134a. System refrigerant charge and the condenser discharge temperature are established to investigate the potential of hydrocarbon refrigerants to substitute R134a without significant system modifications. The overall objective is to identify the major challenges and opportunities for alternative refrigerants for heat pump water heater in terms of performance, required infrastructure and potential for drop-in-replacement.