High-pressure vapor-liquid equilibrium of binary systems with R236fa

Within the European Union Joule project aimed at the substitution of R114 i n high temperature heat pumps with chlorine-free, environmentally benign fl uids, R236fa has been chosen as one of the components of mixtures to consid er as alternative fluids for R114 (1,2-dichlorotetrafluoroethane). The resu lts of VLE measurements performed at our laboratory on mixtures including R 236fa are summarized and discussed for the systems R600a (isobutane) + R236 fa (1, 1,1,3,3,3-hexafluoropropane) at 303 K, RE170 (dimethyl ether) + R236 fa at 303 and 323 K, R134a (1,1,1,2-tetrafluorethane) + R236fa at 283 and 3 03 K, R32 (difluoromethane) + R236fa and R125 (pentafluoroethane) + R236fa, both at 303 and 323 K. All data were correlated by means of the CSD EOS. G enerally small deviations between experimental and calculated vapor composi tions confirm the thermodynamic consistency of the experimental results and the model used for data reduction. An extensive discussion of the deviatio ns from Raoult's law is performed through analysis of the excess Gibbs ener gy. All systems formed by HFCs show a very small g(E), with small deviation from Raoult's law. A much higher gE is shown by the systems R600a + R236fa , with a positive deviation from Raoult's law, and RE170 + R236fa, with a n egative deviation clearly coming from the hydrogen bonding. (C) 1999 Elsevi er Science B.V. All rights reserved.