Bubble point pressure for binary mixtures of difluoromethane with pentafluoroethane and 1,1,1,2-tetrafluoroethane

Bubble point pressures for the two binary hydrofluorocarbon mixtures difluoromethane, CH2F2 with pentafluoroethane CHF2CF3 and 1,1,1,2-tetrafluoroethane CF3CH2F were measured using an acoustic absorption technique. Results cover the temperature range from 243 K to 333 K with an uncertainty of ±20 kPa except at 333.15 K. For the (1−x) CH2F2+xCHF2CF3 system, bubble point pressures show a maximum around x=0.2 at 248.15 K, corresponding to the azeotropic mixture. This point shifts to the CH2F2-rich region with increasing temperature, and finally vanishes out at temperatures higher than 313.15 K. Bubble pressures for the (1−x) CH2F2+xCF3CH2F system decrease monotonously with increasing composition of CF3CH2F at each temperature. These experimental data were fairly well correlated with the Peng–Robinson equation of state including the azeotropic point.