Transport properties of refrigerants R32, R125, R134a, and R125+R32 mixtures in and beyond the critical region

Abstract

A practical representation for the transport coefficients of pure refrigerants R32, R125, R134a, and R125+R32 mixtures is presented which is valid in the vapor–liquid critical region. The crossover expressions for the transport coefficients incorporate scaling laws near the critical point and are transformed to regular background values far away from the critical point. The regular background parts of the transport coefficients of pure refrigerants are obtained from independently fitting pure fluid data. For the calculation of the background contributions of the transport coefficients in binary mixtures, corresponding-states correlations are used. The transport property model is compared with thermal conductivity and thermal diffusivity data for pure refrigerants, and with thermal conductivity data for R125+R32 mixtures. The average relative deviations between the calculated values of the thermal conductivity and experimental data are less than 4–5% at densities ρ⩾0.1 ρ c and temperatures up to T=2 T c.