THE USE OF AN MHV-2 EQUATION OF STATE FOR MODELING THE THERMODYNAMIC PROPERTIES OF REFRIGERANT MIXTURES

This paper reports on the development and application of a thermodynam ic model based on the second-order Modified Huron Vidal equation of st ate (MHV-2) to predict the properties of ternary mixtures of the refri gerants R32, R125, and R134a. The mixing rules of this equation of sta te have been used to incorporate directly an activity-coefficient mode l for the excess Gibbs free energy. The parameters for the activity-co efficient model have been derived from experimental VLE data for binar y mixtures. This methodology has enabled the production of a thermodyn amically consistent model which can be used to predict the phase equil ibria of R32/R125/R134a mixtures. The input data used in the model are presented in the paper and the predictions of the model are compared with available experimental data. The model has been used to predict t he behavior of ternary refrigerant blends of R32/R125/R134a in fractio nation scenarios, such as liquid charging and vapor leakage, which are of direct interest to the refrigeration industry. Details of these ap plications and comparisons with experimental data are discussed, along with other general uses of the thermodynamic model.