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.