Study on Condensation Heat Transfer Characteristics of Nonazeotropic Binary Refrigerant Mixture R1234yf/R32 Inside Small-Scale Horizontal Smooth Tubes

In this study, condensation heat transfer characteristics of nonazeotropic mixtures R1234yf and R32 (mass fractions of 0.52:0.48 and 0.77:0.23, respectively) inside a horizontal smooth tube (inner diameter 2 mm) were experimentally investigated at mass fluxes ranging from 100 to 400 kg/m² s and at a saturation temperature of 40 °C. A prediction model using a modified heat transfer correlation for pure refrigerant was constructed, the details of which are presented here. The heat transfer characteristics, especially the heat transfer deterioration caused by the mass transfer difference of the nonazeotropic refrigerant mixture, were evaluated by combining the correlations of heat transfer and mass transfer on both the vapor side and the liquid side. Through comparison with experimental data, the obtained prediction results were found to agree reasonably with the experimental condensation heat transfer coefficient of binary refrigerant mixtures using R1234yf and R32.