A hybrid formulation for fast explicit calculation of thermodynamic properties of refrigerants

When simulating refrigeration systems or equipment, knowledge of refrigerant thermodynamic properties is required. Even though the traditional equations of state have the ability to yield all of the thermodynamic properties, these formulations present the disadvantage of their low computational speed and that most of the thermodynamic properties equations are implicit and require iterations. In this paper a hybrid formulation for the calculation of thermodynamic properties of pure refrigerants and refrigerant mixtures is presented. Explicit formulations are obtained to model some properties that are used to predict other thermodynamic properties through differentiation, which assures a fast and stable calculation. As an example the equations for R1234yf and R407C are presented in the paper. The source data for regressing was obtained from REFPROP 9.0. The accuracy of the thermodynamic properties formulae is satisfactory for applications in which computation speed and stability are preferred rather than accuracy.