(37b) High-Pressure Viscosity and Density of HFC and HFO Refrigerants in a Synthetic Polyol Ester Lubricant Oil

Hydrofluoroolefins (HFOs) are currently being developed to replace some high Global Warming Potential (GWP) hydrofluorocarbons (HFCs) in air-conditioning and refrigeration applications. The development of low-GWP HFOs, which will replace HFCs in air-conditioning and refrigeration compressors, requires detailed knowledge of the key thermophysical properties of the refrigerants in lubricating oil at varying pressure / temperature conditions. In this work, the high-pressure viscosity and density data for the commonly used HFCs (1,1,1,2-tetrafluoroethane, R-134a; pentafluoroethane, R-125; and difluoromethane, R-32) and the recently developed HFOs (2,3,3,3-tetrafluoropropene, R-1234yf and 1,3,3,3-tetrafluoropropene, R-1234ze (E)) in a synthetic polyol ester lubricating oil (ISO VG 32) will be reported over a temperature range from 248.15 to 348.15 K and pressures of up to 0.6 MPa. In addition, the experimental viscosity and density data for each refrigerant / lubricating oil system were successfully modeled using models for excess viscosity and volume, resulting in an absolute average relative deviation (AARD %) lower than 9.2 % and 0.6 % for viscosity and density, respectively. These models, in combination with previously published solubility correlations,^1,2 are used to compile so-called Daniel Plots that are used by compressor manufacturers to graphically determine the working kinematic viscosity at compressor working conditions. This work will assist in the development of new HFO / lubricant oil systems and operating conditions that allow the replacement of HFCs in existing air-conditioning and refrigeration compressors.

References

1. Morais, A. R. C.; Simoni, L. D.; Douglas, J. T.; Scurto, A. M.; Shiflett, M. B.; “Phase equilibrium and diffusivities of hydrofluorocarbons in a synthetic polyol ester lubricant oil”, AIChE J. 2020. DOI: 10.1002/aic.16241.

2. Morais, A. R. C.; Simoni, L. D.; Scurto, A. M.; Shiflett, M. B.; “Phase behavior and diffusion properties of hydrofluoroolefin refrigerants in a polyol ester lubricant’”, Ind. Eng. Chem. Res. 2020, 59, 13, 6279-6287.