Investigation on the Performance Change of a Heat Pump System with Refrigerant Mixtures during Leakage Process

In a heat pump system, refrigerant mixtures are presented as promising alternative refrigerants. However, their main drawback is a change in composition during refrigerant leakage. Moreover, in an operating system with zeotropic mixtures, the circulating concentration is different from the originally charged concentration. In this study, the numerical method to estimate circulation concentration is proposed, and the leakage model based on the proposed method is established to properly predict the performance change during the leakage process. As a working fluid, a R32/1234yf zeotropic mixture is chosen. The assumption is that the leakage occurs in single-phase regions such as inlet or outlet of compressor or condenser. The deviation from the original composition during leakage affects the system performance change, even though the change is mainly caused by insufficient charge. From the simulation results, the circulation concentration is estimated as 51.25% for the initial condition, in which R32/1234yf is 50/50 by mass. When the 70% of the initial charge amount leaks out of the system, R32/1234yf has composition of 47.3/52.7 and the coefficient of performance (COP) decreases by 52.9%.