Vapor-Liquid Equilibrium Prediction of Refrigerant Mixtures with Peng-Robinson Equation of State and Binary Interaction Parameters Calculated Through Group Contribution Model

Vapor-liquid equilibrium (VLE) properties of refrigerant mixtures are essential to the analysis of thermodynamic cycle performance. The accurate value of binary interaction parameter (k(ij)) for classical Van der Waals (VDW) mixing rules is highly significant for the VLE prediction of mixtures. Therefore, in this contribution, a theoretical correlation for k(ij) is derived as a function of the activity coefficients, which are obtained from the group contribution model UNIFAC. So that, the widely applied Peng-Robinson equation of state with the VDW mixing rule can be predictable for any refrigerant mixtures, according to the existing group contribution values. 18 alternative refrigerant mixtures and two G(E) models, namely MHV1 and WS are used to exhibit the capacities and limitations of the proposed VDW. The calculated results show that the developed VDW can correlate the VLE experimental data well in most cases. Compared with the MHV1 and WS, the proposed model has better VLE prediction, especially for HFCs+HFCs/HFOs mixtures. Thereafter, VLE of 6 refrigerant mixtures are obtained by GC-VTPR. The comparison shows that the accuracy of VDW model is comparable with that of GC-VTPR. Furthermore, mixture densities at different temperatures and pressures are predicted by the developed VDW and GC-VTPR. Results show that GC-VTPR has better density prediction than VDW and the largest deviation of VDW between predicted results and experimental data is 7.04% for R125+R143a.