Solubility and Diffusivity of Hydrofluoroolefin Refrigerants in a Polyol Ester Lubricant

To support the phaseout of high global warming potential working fluids commonly used in air-conditioning and refrigeration systems, detailed knowledge about the thermodynamic and transport properties of replacements, for example, hydrofluoroolefins (HFOs), in lubricant oils is required. In this context, isothermal experimental vapor–liquid equilibrium (PTx) and diffusivity measurements for 2,3,3,3-tetrafluoropropene (R-1234yf) and trans-1,3,3,3-tetrafluoropropene (R-1234ze (E)) in a synthetic polyol ester lubricant (ISO VG 32) were performed using a gravimetric microbalance over a temperature range from 248.15 to 348.15 K and pressures of up to 0.6 MPa. A nonrandom two liquid (NRTL) activity coefficient model was applied to correlate the measured solubility for each HFO/lubricant mixture. The diffusivities of R-1234yf and R-1234ze (E) in ISO VG 32 oil were determined from time-dependent absorption data based on a one-dimensional diffusion equation. The calculated diffusivities ranged from 10–12 to 10–10 m2·s–1 and were dependent on temperature and refrigerant composition.