A New Excess Free Energy Mixing Rule for Representing Vapor-Liquid Equilibria of Mixed Refrigerants

A suitable mixing rule is important for vapor liquid equilibrium (VLE) investigations for mixed refrigerants. In this work, a new excess free energy mixing rule (MRv) was proposed at zero pressure based on the linear relationship between dimensionless parameter 1/(u–1) and α. MRv mixing rule was explicit adopted variable liquid molar volume. The applicable temperature range of MRv could be extended by means of an empirical method to estimate the liquid molar volume for components at high temperatures. Three mixing rules modified Huron-Vidal mixing rule (MHV1), Wong-Sandler mixing rule (WS), and MRv at two reference pressures were used to compare the VLE data in the calculation of 37 mixed refrigerants. Results demonstrated that MRv had a relatively similar accuracy to MHV1 and WS for component and pressure calculation. Moreover, the average excess Gibbs free energy using the MRv mixing rule for the 37 selected mixed refrigerants (0.0013) was much lower than those using the MHV1 (0.0078) and WS (0.0809) mixing rules, which was very valuable for the design and optimization of thermodynamic systems using mixed refrigerants.