VLE measurements and modeling for the strongly positive azeotropic R32+propane system

In an effort to identify suitable substitutes for CFCs and HCFCs in HVAC&R applications, particular attention has to be paid to mixtures between hydrocarbons and hydrofluorocarbons, as stressed by the IUPAC project on halocarbons. The aim of the present work is to measure the vapor-liquid equilibria (VLE) for the difluoromethane (R32) + propane (R290) system in the range of temperature between 248.13 and 294.91 K. This choice has been inspired by the fact that existing literature data on the VLE for this system are clearly not consistent each other [1-3]. In addition, Holcomb et al. [1] observed a liquid phase split at a quite high temperature (3 10 K) that is not confirmed in [2,3] papers. The measurements are performed at isothermal conditions in a vapor recirculation apparatus. The composition of the equilibrium phases is measured by gas-chromatographic analysis. The estimated accuracies of the measured data are +/- 0.02 K for temperature, +/- 1 kPa for pressure, +/- 0.002 in mol fraction for both liquid and vapor phase. No liquid phase splitting was observed within the experimental temperature range, as confirmed by the VLE data reduction performed using a RKS EoS with the Huron-Vidal (HV) mixing rule and NRTL model for the excess energy. (C) 2002 Elsevier Science B.V. All rights reserved.