Vapor−Liquid Equilibria Predictions for New Refrigerant Mixtures Based on Group Contribution Theory

Abstract

Vapor−liquid equilibria (VLE) for new refrigerant mixtures containing hydrofluorocarbons, alkanes, alkenes, dimethyl ether, CO 2, and perfluoroalkanes are of great interest. Those mixtures generally exhibit azeotropes, high nonideality, association effects, and contain supercritical compounds. The modified Soave−Redlich−Kwong equation of state is used with zero reference pressure G E −EoS mixing rules and the UNIFAC group contribution model in this study to form a group contribution model for predicting vapor−liquid equilibria. A new functional group assignment strategy is used, and the values of interaction parameters between groups are provided. These parameters are optimized from selected binary vapor−liquid equilibria data to give good representations of the experimental VLE data. A ternary system was also accurately predicted using the group contribution model. The method is totally predictive because only the structures and the critical constants of the pure components are needed to calculate the thermodynamic properties of new refrigerant mixtures.