A perturbed-hard-sphere-chain equation of state for phase equilibria of mixtures containing a refrigerant and a lubricant oil

A modification of the perturbed-hard-sphere-chain equation of state (EOS) is used to describe vapor–liquid (VLE) and liquid–liquid equilibria (LLE) of mixtures containing new-generation refrigerants and a lubricant oil. For refrigerants, pure-component parameters are obtained from thermodynamic data. For the oil, they are predicted by a group-contribution method, and the calculation is checked on liquid density values of polyol-ester lubricants. Extension to mixtures is performed by using conventional one-fluid mixing rules with binary interaction parameters regressed from VLE experimental data. VLE calculations are reported for mixtures containing a refrigerant and a polyol-ester lubricant over wide temperature and concentration ranges. The thermodynamic condition for LLE is checked. If two liquid phases are present, LLE is calculated and compared with experimental measurements.