Development of models for prediction of solubility for HFC working fluids in pentaerythritol ester compressor oils

This study aims to further develop a model of the group contribution type that can predict the solubility of mixtures of HFC working fluids and pentaerythritol ester compressor oils. The investigation is based on solubility data for 20 systems of five different HFCs in four different pentaerythritol esters. First, five different activity factor-based thermodynamic models were investigated to determine to what extent they can describe the solubility data. Two promising models were selected and extended with group contribution parameters to be able to predict solubility data. The first model, a modified Flory–Huggins based predictive model (termed MFH), needs only 15 general parameters to describe the data with a relative deviation of less than 3.4%. The second model, a predictive Unifac model with an extended temperature dependence, needs 33 general parameters to describe the solubility data for the 20 systems with a relative deviation of less than 3.5%.