Vapor–Liquid Equilibrium and Azeotrope Mechanisms in Binary Refrigerant Blends: A COSMO-RS Study

Refrigerants are essential in refrigeration systems, yet ozone-depleting potential and global warming impacts drive persistent research into sustainable alternatives. Vapor–liquid equilibrium (VLE) data are critical for developing alternative refrigerant blends and optimizing refrigeration thermodynamics. In this work, ASHRAE-named refrigerant blends were systematically collected. The VLE behavior of these blends was predicted by COSMO-RS and compared with experimental data. Results showed that the overall accuracy of COSMO-RS prediction was 79.22%, and the accuracy of COSMO-RS prediction of azeotropes was 85.71%, confirming the effectiveness of COSMO-RS. Analysis based on screening charge density and excess free energy (HsumE) showed that except for some HFCs–HFCs, homologous blends basically did not form azeotropes. For heterologous blends, the formation of azeotropes required that boiling point difference (ΔTBP) was close enough and HsumE needed to exceed a certain range. Furthermore, the prediction for new low-GWP refrigerant blends provided theoretical guidance for the development of environmentally friendly refrigerant blends.