Simulation of binary refrigerant mixture vapor-liquid equilibria using a quasi-regular nonrandom fluid theory and local composition mixing rules

Abstract

A new model and a novel approach are presented for correlation/prediction of refrigerant mixture phase equilibria. The excess Gibbs free energy in binary halogenated alkane mixtures is described by a recently proposed two-liquid theory with a regular solution reference for mixtures of nonpolar species. The single g E model parameter, obtained by correlating near-ambient binary vapor-liquid equilibria (VLE), is used in Wong-Sandler mixing rules in the Peng-Robinson-Stryjek-Vera equation of state to predict binary VLE at elevated temperatures. This model is applied to the tetrafluoromethane-chlorotrifluoromethane (R14-R13), tetrafluoromethane-trifluoromethane (R14-R23), and the trifluoromethane-chlorotrifluoromethane (R23-R13) binary systems. The one-parameter quasi-regular g E model provides good correlation of VLE for the binary systems at near ambient conditions. However, successful prediction of high temperature VLE depends on the accuracy of the g E model, the consistency of the EOS mixing rule model, and the method used to solve the model equations and associated material balances.