Vapor-liquid equilibrium measurement and critical line prediction for carbon dioxide (CO2) + fluoroethane (R161) binary mixtures

CO2-based binary mixtures are excellent alternative working fluids due to their environmentally friendly and thermodynamically favorable properties. The vapor -liquid equilibrium properties of mixtures are necessary to determine the enthalpy and entropy of the dew point and bubble point. Isothermal vapor -liquid equilibrium data for the CO2/R161 are measured at temperatures ranging from 283.15 K to 323.15 K and at pressures ranging from 1.28 MPa to 7.30 MPa. The temperature and pressure of the mixtures are measured using a static thermostatic analysis vapor -liquid equilibrium system. Two electromagnetic capillary samplers repeatedly collect the vapor -liquid phase components from the equilibrium cell for analysis via gas chromatograph. The standard uncertainties for mole fractions, pressure, and temperature are 0.004, 0.002 MPa, and 0.06 K, respectively. The Peng-Robinson equation, incorporating the Wong -Sandler mixing rule and the Non -Random Two -Liquid model, is utilized to fit the obtained vapor -liquid equilibrium data. The average absolute relative deviation of pressure is 0.56%, and the average absolute deviation of vapor phase molar fractions is 0.0049. The relative volatility under the five isotherms is also calculated, and most of the experimental data fall within a deviation of +/- 5% from experimental values/ calculated results. In addition, this model accurately predicts the critical point line of the CO2 and R161 binary mixtures through the binary interaction parameters.