Annual performance analysis of an air source heat pump water heater using a new eco-friendly refrigerant mixture as an alternative to R134a

Abstract The air source heat pump water heater (ASHPWH) is an efficient and environmentally friendly system that is widely used in China. In this study, a refrigerant mixture R290/R600a/R13I1 with low global warming potential (GWP) and no ozone depletion potential (ODP) is proposed as drop-in replacement for R134a in ASHPWH. A theoretical model for an ASHPWH is developed based on MABLAB linking with REFPROP. The cycle performances of the proposed mixture, a contrast mixture, and R134a are analyzed under different working conditions, to investigate the feasibility of substitution. The annual performances of the ASHPWH that uses different refrigerants are also studied for comparison. The results show that compared with R134a, the proposed mixture has better performance with lower condensing pressure and compression ratio, and higher specific heating capacity and coefficient of performance (COP). The discharge temperature is also reasonable. Therefore, it is feasible to replace R134a with the proposed mixture. The ASHPWH using the proposed mixture has obvious advantages when the ambient temperature is very low. The annual average COP with the proposed mixture is 4.65, which is about 6.2% higher than with R134a, and the total equivalent warming impact (TWEI) can be reduced by 18.99%.