Estimating the viscosity of pure refrigerants and their mixtures by free-volume theory

•The FVT is extended to viscosities of 24 hydrofluorocarbon refrigerants and their mixtures.•It is the first time to apply the FVT to ternary mixtures of hydrofluorocarbon refrigerants.•Three mixing rules without more parameters were tested and compared.

In this work, the free-volume theory (FVT) was extended to modeling the viscosities of 24 hydrofluorocarbon refrigerants, and applied to predict the viscosities for the mixtures of hydrofluorocarbon refrigerants. It is the first time to apply the FVT to the viscosities of ternary mixtures of hydrofluorocarbon refrigerants. Hydrofluoro-olefins (HFOs) are a new class of refrigerants, which are identified as promising refrigerants because they have low global warming potential, were studied in this paper. For the viscosity of pure refrigerants, the average absolute relative deviations between the FVT calculation and experiment are less than 1.5%. When calculating the viscosities of the mixtures of hydrofluorocarbon refrigerants, three mixing rules without more parameters were tested and compared, the average absolute relative deviations between the FVT coupled with the best mixing rule and experiment are less than 6.5%.