A method for the prediction of vapour-liquid equilibria of refrigerant mixtures at low and moderate pressure

This paper is a contribution to the development of a method for the prediction of the thermodynamic behaviour of refrigerant mixtures at low and moderate pressure, for which experimental data are not always available. The proposed model is based on a modified Redlich-Kwong-Soave equation of state, with mixing rules as proposed by Huron and Vidal. The calculation of the attractive parameter is based on infinite-pressure activity coefficients according to Soave et al. Activity coefficients are expressed by a group-contribution model derived from UNIFAC. A list of groups and subgroups is proposed for CFCs, HCFCs, HFCs and FCs. Two interaction parameters are regressed from experimental infinite-dilution activity coefficients of binary mixtures. As a result, only the structure, critical constants and vapour pressure of pure components are needed to calculate thermodynamic properties of refrigerant mixtures. The proposed approach is able to predict experimental data with satisfactory accuracy over the full composition range. © 1995.