Vapor−Liquid Equilibrium Measurements and Correlation of the Binary Refrigerant Mixture Propane (HC-290) + 1,1,1,2,3,3,3-Heptafluoropropane (HFC-227ea) at 278.15, 293.15, and 308.15 K

Isothermal vapor−liquid equilibria for the binary system propane (HC-290) + 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea) were measured at 278.15, 293.15, and 308.15 K using a recirculation apparatus in which the vapor phase was forced through the liquid. The phase composition at equilibrium was measured by gas chromatography; calibration of the response was made with gravimetrically prepared mixtures. The system shows a major deviation from Raoult's law, with the formation of a homogeneous azeotrope at a mole fraction of propane of about 0.8. The uncertainties in pressure, temperature, and vapor- and liquid-phase composition measurements were estimated to be no more than ±1 kPa, ±0.02 K, and ±0.002 in the mole fraction, respectively. The data were reduced using the Carnahan Starling De Santis (CSD) equation of state (EoS) and the Lemmon−Jacobsen (LJ) Helmholtz energy mixture model. A comparison was made with VLE calculations from REFPROP 6.0 for both the experimental data and the data reduction models.