(25e) Solubility and Diffusivity for Hydrofluorocarbon and Hydrofluoroolefin Refrigerants in Poe ISO Vg 32 Lubricant Oil

Detailed knowledge about the thermodynamic properties of alternative refrigerant/lubricant oil systems, such as solubility and diffusivity, are required for the design, operation, and long-time reliability of HVAC&R equipment. In the present work, gaseous absorption measurements of HFCs (1,1,1,2-tetrafluoromethane (R-134a), difluoromethane (R-32) and pentafluoroethane (R-125)) and hydrofluoroolefins (HFOs) (2,3,3,3-tetrafluoropropene (R-1234yf) and 1,3,3,3-tetrafluoropropene (R-1234ze (E)) in a polyol ester oil (ISO VG 32) were measured using a gravimetric microbalance at temperatures ranging from 248.15 to 348.15 K. The experimental solubility data for each refrigerant/lubricant oil system were successfully correlated using a non-random two liquid (NRTL) activity coefficient model and Soave-Redlich-Kwong equation of state with Wong-Sander mixing rules. The R-1234ze (E) was the most soluble refrigerant, while R- 32 was the least soluble among all the refrigerants studied at a given temperature and pressure. A one-dimensional diffusion equation was applied on time-dependent absorption data to determine binary diffusion coefficients (D) for the refrigerants in the lubricant. The observed D varied from 10^-10 and 10^-12 m²/s for the refrigerants studied. Diffusing radius calculations based on the Stokes-Einstein correlation support the hypothesis that the refrigerants dissolve into ISO VG 32 lubricant as individual refrigerant molecules.