Abstract

Vapor–liquid equilibrium (VLE) of binary refrigerant blends, HFO1123 + CF₃I and HFC125 + CF₃I, were measured at temperature range from 263 to 323 K by the recirculation method. A sample was filled into an equilibrium cell of the experimental apparatus equipped with optical windows in the vapor–liquid equilibrium condition, and the saturated vapor and liquid were extracted from each phase in small quantities. The compositions of the samples were measured by a gas chromatograph with a thermal conductivity detector and a Porapak-Q column. The expanded uncertainties in temperature, pressure, and composition are estimated to be 10 mK, 3.0 kPa, and 0.007 mol·mol⁻¹, respectively. Based on the experimental data, mixing parameters of a cubic equation of state (PR EOS) and Helmholtz energy EOSs were determined. The VLE behavior (temperature, pressure, and composition relation) calculated from the PR EOS and the Helmholtz energy EOSs show good agreement with each other. The PR EOS reasonably represents the VLE data with an absolute average deviation (AAD) of 1.8% for HFO1123 + CF₃I and that of 1.1% for HFC125 + CF₃I in pressure, and with an AAD of 0.012 mol·mol⁻¹ in mole fraction for both mixtures. In addition, PVTx properties of HFO1123 + CF₃I and HFC125 + CF₃I blends were measured from 300 to 400 K and at pressures up to 6.9 MPa by the isochoric method. The expanded uncertainties in temperature and pressure are estimated to be 5 mK and 1.0 kPa (k = 2). The relative expanded uncertainties in density and mass fraction are estimated to be 0.0015 and 0.0005 (k = 2), respectively. The Helmholtz energy EOSs with the mixing parameters determined on the basis of the VLE data were compared with the experimental PVTx property data, and the EOSs represent them in the vapor phase except for the isochores near the critical density with an AAD of 0.9% in density.