Solubility of RE170 in polyol ester lubricants and the mixing thermodynamic properties

Dimethyl ether (RE170) is generally used as a component in mixed refrigerants due to its excellent thermodynamic properties. However, the phase behavior of RE170 with lubricants is still scarce at present. Therefore, this work systematically investigates the solubility of RE170 in four polyol ester lubricants (POE32, POE46, POE75, POE85) and evaluates its thermodynamic performance in evaporator. The solubility measurements were carried out using isochoric saturation method over the temperature range of 283.15 K to 343.15 K. Results show that the maximum solubility of RE170 in four POE lubricants exceeds 0.75. The non-random two-liquid (NRTL) model and Wilson model were employed to correlate the solubility data, the average absolute relative deviation between experimental and calculated values is lower than 0.8% for the studied mixtures. In addition, for comparison purpose, the p-h-X diagrams of RE170/POE32 and R134a/POE32 mixtures were plotted and discussed. For RE170/POE32, the critical vapor qualities are approximately 0.8 and 0.7 at lubricant circulation mass fractions of 2% and 4%. For R134a/POE32, the critical vapor qualities are approximately 0.7 and 0.6 under the same conditions. At the same oil circulation mass ratio and superheat degree, RE170/POE32 exhibits higher enthalpy change ratio and lower non-evaporated quantity compared with R134a/POE32a.