Thermodynamic properties of mixtures of R-32, R-125, R-134a, and R-152a

A mixture model explicit in Helmholtz energy has been developed that is cap able of predicting thermodynamic properties of refrigerant mixtures contain ing R-32, R-125, R-134a, and R-152a. The Helmholtz energy of the mixture is the sum of the ideal gas contribution, the compressibility (or real gas) c ontribution, and the contribution from mixing. The contribution from mixing is given by a single equation that is applied to all mixtures used in this work. The independent variables are the density, temperature, and composit ion. The model may be used to calculate thermodynamic propel ties of mixtur es, including dew and bubble point properties and critical points, generall y within the experimental uncertainties of the available measured propertie s. It incorporates the most accurate published equation of state for each p ure fluid. The estimated uncertainties of calculated properties are +/-0.25 % in density, +/-0.5% in the speed of sound, and +/-1% in heat capacities. Calculated bubble point pressures are generally accurate to within +/-1%.