Measurement of the relative permittivity of the liquid phase of R454C with vapor quality change under two-phase condition

The capacitance-based method is an alternative method for measuring the void fraction of refrigerants. The relative permittivity of the liquid phase is an essentially required property for the capacitance-based method. Unlike pure refrigerants, the composition in the liquid phase of zeotropic refrigerants and their saturation temperature depend on the vapor quality; therefore, zeotropic refrigerants have a change in the relative permittivity of the liquid phase during the phase change process. To generally apply the capacitance-based method to zeotropic refrigerants for which relative permittivity information is relatively insufficient, it is necessary to accurately predict the relative permittivity of liquid zeotropic refrigerants during phase change based on the relative permittivity of pure refrigerants. In this study, the relative permittivity of the liquid phase of a two-phase refrigerant was measured using the parallel plate method. And the measured results were compared to that estimated by five types of mixing rules. The measurements were performed at saturation pressures of 1.04–1.72 MPa and vapor qualities of 0–0.7 for R454C refrigerant. The saturation temperature variation ranged from 18 to 44 °C. Landau and Lifshitz's mixing rule best predicts the relative permittivity with a mean percentage error (MAPE) of 1.02% as the vapor quality of R454C varies.