Comparison on the Absorption Capacity of Dipentaerythritol Esters for HFC-134a and HFO-1234ze(E): Solubility Measurement and Modelling

Due to the extremely low global warming potential (GWP) and good performance, trans-1,3,3,3-tetrafluoropropene (HFO-1234ze(E)) is considered as one of the substitutions for widely used 1,1,1,2-tetrafluoroethane (HFC-134a) in refrigeration industry. The solubility of HFO-1234ze(E) with lubricant is essential for the optimization of refrigeration system. Dipentaerythritol ester (DiPE) is one of the pure components of polyol ester (POE) lubricant. In order to elucidate the absorption capacity of DiPEs for HFO-1234ze(E), its solubilities in three DiPEs including dipentaerythritol hexapentanoate (DiPEC5), dipentaerythritol hexaheptanoate (DiPEC7), and dipentaerythritol isononanoate (DiPEiC9) were measured from 283.15 K to 343.15 K in this work. Meanwhile, for comparison purpose, the solubilities of HFC-134a in DiPEs were also determined. The measurement was carried out using isochoric saturation method. The experimental data were correlated using the non-random two-liquid (NRTL) model, achieving an absolute average relative deviation of less than 1% for HFO-1234ze(E)/DiPEs and HFC-134a/DiPEs mixtures. In addition, the comparison for absorption capacity of DiPE for HFO-1234ze(E) and HFC-134a was conducted. At the same conditions, HFO-1234ze(E) is more soluble in DiPEs than HFC-134a.