Thermodynamic properties of 1,1,1,2-tetrafluoroethane (R-134a) + 2,3,3,3-tetrafluoropropene (R-1234yf) mixtures: Measurements of the critical parameters and a mixture model based on the multi-fluid approximation

• The critical parameters of R-134a + R-1234yf mixtures were measured for three different compositions.
• The parameters were successfully correlated with simple correlations.
• A mixture model explicit in the Helmholtz energy was developed for the mixtures.
• The mixture model calculates the vapor–liquid equilibrium and densities of the mixtures with reasonable accuracies.
• The model is fully applicable to assess refrigeration systems using the mixtures.

Thermodynamic properties are discussed for 1,1,1,2-tetrafluoroethane (R-134a) + 2,3,3,3-tetrafluoropropene (R-1234yf) mixtures. The critical temperatures, densities, and pressures experimentally determined are first presented with their uncertainties. Subsequently a mixture model for calculations of thermodynamic properties is formulated using the multi-fluid approximation. Comparisons to experimental data show that the mixture model calculates the vapor–liquid equilibrium and densities of the mixtures with reasonable accuracies. The critical parameters are also well represented by the mixture model.