Modelling of pure refrigerant thermodynamic properties and vapor-liquid equilibrium of refrigerant mixtures with the UMR-PRU model

Abstract

In this work, the UMR-PRU model is extended to refrigerant mixtures. Key properties of pure refrigerants, such as vapor pressure, saturated volume, heat capacity and enthalpy of vaporization are examined with the Peng-Robinson equation of state, to which UMR-PRU reverts for pure components, and appropriate modifications to the attractive and repulsive terms are made. For the extension of UMR-PRU to refrigerant mixtures, four new UNIFAC groups are introduced and binary UNIFAC interaction parameters are fitted to experimental vapor-liquid equilibrium data. The predictive capability of the model is tested in ternary refrigerant mixtures. A comparison is made between UMR-PRU and the REFPROP model, which is currently considered as the state-of-the-art model for refrigerants. The results reveal that UMR-PRU describes the vapor-liquid equilibrium of refrigerant mixtures with similar accuracy as REFPROP. Both models are also employed for performing process simulations of vapor compression refrigeration cycles, yielding very comparable results regarding the COP and mass flowrate of the working fluid.