Isothermal Vapor–Liquid Equilibrium for the Tetrafluoromethane (R14) + Octafluoropropane (R218) Binary Mixture at Five Temperatures from 173.150 to 213.150 K

Abstract

Tetrafluoromethane (R14) and octafluoropropane (R218) are essential nonflammable refrigerants for mixed-refrigerant Joule Thomson refrigerators. In this paper, the vapor–liquid equilibrium (VLE) data were acquired for the R14 + R218 binary mixture from 173.150 to 213.150 K by a vapor-phase single-cycle method. The VLE data were regressed by the Soave–Redlich–Kwong (SRK) equation of state plus van der Waals (vdW) mixing rule model (SRK-vdW) and the Soave–Redlich–Kwong (SRK) equation of state combined with modified Huron–Vidal first-order (MHV1) mixing rule plus non-random two liquids (NRTL) activity coefficient model (SRK-MHV1-NRTL). The maximum average absolute relative deviation of pressure (AARDp) and the maximum average absolute deviation of vapor-phase mole concentration (AADy) are 2.42% and 0.0019 for the SRK-vdW model, respectively. A better correlation result was obtained by the SRK-MHV1-NRTL model, and the maximum AARDp and AADy are 1.04% and 0.0019, respectively. Based on the experimental and calculated results, a strong non-azeotropic behavior was found.