Thermodynamic Properties of 3,3,3-Trifluoropropene and Polyol Ester Lubricant Mixtures

This study investigates the thermophysical characteristics of binary mixtures involving the low-global warming potential refrigerant 3,3,3-trifluoropropene (R-1243zf) and two polyol ester (POE) lubricants (RL 32 and RL 68). Experimental measurements of solubility, liquid density, and dynamic viscosity were conducted over a temperature range of 298–353 K. These outcomes imply that R-1243zf exhibits complete miscibility with both POE oils across the studied conditions, with higher solubility observed in POE RL 32 compared to POE RL 68. The dissolution of R-1243zf significantly reduces the flow characteristics of the lubricants, particularly in the oil-rich phase, while its effect on liquid density is relatively minor. A satisfactory correlation of the phase equilibrium data was achieved with the non-random two-liquid model, and mixture densities and viscosities were accurately represented using an excess-property approach combined with Redlich–Kister expansions. Additionally, Daniel charts were constructed to illustrate the viscosity–pressure–temperature–concentration relationships for both mixtures, providing practical guidance for the selection of lubricating oils in R-1243zf-based refrigeration systems. The findings suggest that POE RL 68 offers better viscosity retention under high-temperature conditions, making it more suitable for severe operating environments.