Investigation on Density Measurement of R1234yf-CF₃I Refrigerant Mixture near the Saturation State

A density measurement system was developed for the low-GWP refrigerant mixture R1234yf-CF₃I, measuring densities near the saturation state across three nominal mass ratios: 7:3, 5:5, and 3:7. This system included a vapor-liquid equilibrium (VLE) cell and a vibrating-tube density meter, both housed within a thermostatic chamber maintained at a temperature within ±0.1 K. Using reference fluids, we established a correlation between the resonant period and density for both the vapor and liquid phases, enabling the construction of a density measurement system specific to the mixture near saturation. The system was validated by measuring the near-saturation densities of the R32-R125 mixture, yielding small mean absolute percentage errors (MAPE) of 0.31% for the vapor phase and 0.08% for the liquid phase, compared to REFPROP10 data. We measured the densities of the R1234yf-CF₃I mixtures at three near-saturation points, extrapolating the saturation densities from the trends observed in these data. The near-saturation density data obtained in this study are expected to enhance the accuracy of the equation of state (EOS) for these mixtures.