Phase and volumetric behavior of binary systems containing carbon dioxide and lubricants for transcritical refrigeration cycles

In this work we have studied the ability of PC-SAFT to correlate gas solubility data and to predict the phase diagrams of mixtures of CO2 with long alkanes (octacosane and squalane) or esters (pentaerythritol esters, PEs, and commercial polyol esters, POEs). PC-SAFT parameters were optimized using a database containing vapor pressures and saturated liquid densities of the alkanes. The agreement between calculated and measured properties (vapor pressures or saturated liquid densities) is satisfactory. PC-SAFT predicts the temperature dependence of the compressed densities quite well but the slope of ρ(P) is higher than the experimental one. For several PEs and commercial POEs the intermolecular potential model parameters were obtained from published linear relationships of m, mσ3 and mɛ, with the molecular weight.For the binary mixtures PC-SAFT with a unique binary interaction parameter gave vapor–liquid equilibria with AADx's lower than 0.05 in the mole fraction of CO2 in the liquid phase. This equation also predicts the barotropic effect for the systems of CO2 with long alkane. For CO2 + commercial POE mixtures PC-SAFT has represented successfully solubility data.