High pressure vapor-liquid equilibria of binary mixtures composed of HFC-32, 125, 134a, 143a, 152a, 227ea and R600a (isobutane)

The vapor-liquid equilibrium data for six binary mixtures of isobutane + HFC-32, +HFC-125, +HFC-134a, +HFC-143a, +HFC-152a, and +HFC-227ea were correlated with the Peng-Robinson-Stryjek-Vera (PRSV) EOS combined with the NRTL excess free energy model and original Huron-Vidal (HVO) mixing rules. Almost all the calculated values with these models give good agreement with the experimental data. In addition, the nonideality of these binary mixtures was discussed by calculating the excess Gibbs energy at 303.15 K. Among these mixtures, four mixtures (isobutane + HFC-32, +HFC-134a. +HFC-152a, and +HFC-227ea) exhibit azeotropes. The measured azeotropic points were compared with calculated values by using the simple equations derived in this work from the fundamental equation-of-state and NRTL model. They show relatively good agreement with each other. In the range of experimental temperature, the NRTL parameters and azeotrope data were presented. (C) 2002 Elsevier Science B.V. All rights reserved.