Evaluation and Prediction on the VLE of Binary Systems Containing HFO Refrigerants and PEC Lubricants

As one of the most promising environmentally friendly refrigerants, hydrofluorolefins (HFOs) refrigerants will be widely used in mechanical vapor compression refrigeration systems. Thus, an understanding and accurate quantitative description of the phase equilibrium behavior of binary refrigerant–lubricant mixtures is important. In this article, the vapor liquid phase equilibrium (VLE) of binary systems containing four types of HFO refrigerants and six pentaerythritol esters (PEC) lubricants was critically investigated. The applicability of quadratic and excess free energy based mixing rules was systematically investigated for the HFO/PEC system. Calculation results indicate that the vdW mixing rule showed the least applicability, while the vdW-II mixing rule, which considers intermolecular differences, demonstrated better calculation accuracy with an average pressure deviation of 0.96%. The WS-NRTL and HVOS-Wilson models have the smallest average pressure deviations, both less than 0.7%. In order to further extend the predictive performance of the established model, the UNIFAC model based on the group contribution method was used to fit and correlate the experimental data. By using the group interaction parameter obtained from data reduction, several binary systems were predicted, and the average pressure deviation was less than 6%.