Performance assessment of optimized heat pump water heaters using low-GWP refrigerants for high- and low-temperature applications

In this study, performance improvements of optimized heat pump water heaters (HPWHs) employing low global warming potential refrigerants are numerically evaluated against the performance of the conventional R-410A HPWH. A simulation model for HPWHs is developed and validated based on experimental results obtained in the R-410A and R-32 HPWHs. The performances of the HPWHs employing R-32, R-446A, and L-41b are simulated considering for high-temperature applications (HTAs) and low-temperature applications (LTAs) based on EN 14511. The heat exchanger design parameters of the HPWHs are optimized for achieving the maximum coefficient of performance (COP) for each alternative refrigerant. The optimized L-41b HPWH exhibits the highest COP, and the COP improvements thereof are 6.3% and 4.6% in the HTA and LTA conditions, respectively, compared with those of the R-410A HPWH. Moreover, the total equivalent warming impacts of the optimized HPWHs employing the alternative refrigerants are 5.9–9.9% lower than those of the R-410A HPWH.