VLLE measurements and correlation for the pentafluoroethane (R125) + n-butane (R600) system

Hydrocarbon and hydrofluorocarbon mixtures are possible substitutes for chlorinated refrigerants. This family of mixtures, as pointed out in our studies on VLLE for the difluoromethane (R32) + propane (R290) and (R32) + n-butane (R600) systems, shows the possibility of liquid–liquid phase splitting. In this work, the liquid immiscibility of the pentafluoroethane (R125) + (R600) system has been measured with the cloud-point method down to 200 K in a sealed glass cell of about 30 cm3 and equipped with magnetic stirrers. The temperature is maintained at ±3 mK and measured to within ±0.1 K. Uncertainty in pressure is estimated to be within ±4 kPa. The bulk composition is gravimetrically measured with an uncertainty of ±0.005 in mole fraction. measured P–T–x data, the VLLE parameters are derived using the Redlich–Kwong–Soave (RKS) and Peng–Robinson (PR) equations of state (EoS), both with the Huron–Vidal mixing rule with the NRTL equation for the excess Gibbs free energy at infinite pressures.