Energy and environmental performance of vapor injection heat pumps using R134a, R152a, and R1234yf under various injection conditions

Vapor injection heat pumps have been used to mitigate performance degradation under severe operating con-ditions. Low-global-warming-potential (GWP) refrigerants have been used to replace R134a in heat pumps to comply with F-gas regulations. However, experimental and optimization analyses of vapor-injection heat pumps with low-GWP refrigerants are limited in terms of injection conditions. In this study, the energy and environ-mental performance of vapor-injection heat pumps containing low-GWP refrigerants were experimentally investigated under various injection conditions. The capacity and coefficient of performance (COP) of the vapor-injection heat pumps using R152a and R1234yf were optimized and compared to those using R134a under various injection conditions. The optimized vapor-injection heat pump using R152a increased the heating and cooling COPs by 5.7% and 1.3%, respectively, compared to those using R134a because of its lower power consumption. In addition, the life-cycle climate performance (LCCP) of the optimized vapor-injection heat pumps using R152a and R1234yf were 4.7% lower and 3.0% higher, respectively, than those using R134a under practical conditions. Overall, R152a is recommended as a preferred alternative for vapor-injection heat pumps because of its high COP and low LCCP.