Performance simulation of the indoor unit of a heat pump with low-GWP alternative refrigerants

The aim of this study is to compare the performance of different low-GWP alternative refrigerants in the indoor unit of a heat pump with that of R410A. The indoor unit heat exchanger is simulated with refrigerants R410A, R32, R466A, R454B, R454C, and R455A for both cooling and heating cases, assuming an ideal thermodynamic cycle. Refrigerants R32, R466A, and R454B exhibit performance similar to R410A in both cooling and heating, with HTC deviating by no more than 3 % and 5.8 %, respectively. In contrast, low-pressure refrigerants R454C and R455A exhibit significantly reduced HTCs due to their lower thermal conductivity, specific heat, higher viscosity, and reduced mass flux in their circuits. Specifically, R454C and R455A exhibit 50.5 % and 38.6 % lower HTCs in cooling, and 35.8 % and 15.4 % lower in heating, compared to R410A, leading to reduced performance. Further analysis revealed that refrigerants with a high GTD produced temperature profiles similar to parallel flow configurations, resulting in a high temperature gradient between the air and refrigerant. To enhance heat transfer efficiency in these scenarios, circuitry optimization is essential for R454C and R455A when utilizing these low-GWP refrigerants in indoor units.