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

摘要

Bubble point pressures for the two binary hydrofluorocarbon mixtures difluoromethane, CH_2F_2 with pentafluoroethane CHF_2CF_3 and 1,1,1,2-tetrafluoroethane CF_3CH_2F 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) CH_2F_2+xCHF_2CF_3 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 CH_2F_2-rich region with increasing temperature, and finally vanishes out at temperatures higher than 313.15 K. Bubble pressures for the (1-x) CH_2F_2+xCF_3CH_2F system decrease monotonously with increasing composition of CF_3CH_2F at each temperature. These experimental data were fairly well correlated with the Peng-Robinson equation of state including the azeotropic point.