Hydrocarbons as natural refrigerants for heat pump water heating applications.

Growing awareness of the potential environmental impacts of conventional refrigerants (CFCs and HFCs) has led to efforts to identify suitable refrigerants for various heat pump applications with minimum environmental impact. This study is focused on the performance evaluation of pure propane and isobutane 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. Appropriate experiments are conducted to validate the finding from model. Simulation and experimental 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.