Calculation of vapour—liquid equilibrium data for binary chlorofluorocarbon mixtures using the Peng-Robinson equation of state

Abstract

Chlorofluorocarbons (CFCs) and their mixtures are of great importance as refrigerants, solvents and degreasing agents in the aerospace and electronics industries. The use of some CFCs in aerosols is now restricted owing to the possibility of their accumulation in the upper atmosphere and their effect on the Earth's ozone layer. These active uses and potential effects on health, safety and the environment have created a need for accurate methods to calculate vapour—liquid equilibrium (VLE) data using the readily available pure-component critical properties. The Peng-Robinson (P-R) equation of state has been used in this study to calculate vapour—liquid equilibrium data for several binary fluorocarbon—fluorocarbon and gas—fluorocarbon mixtures. The binary interaction parameters required for this equation have been fitted by the minimization of either the sum of the squares of the residuals in fugacities or the sum of the squares of relative errors in pressure, for comparison. The results of these calculations have been compared with the corresponding experimental data as well as with those calculated using other equations of state or combinations of them. It is found that the VLE data calculated by the P—R equation of state are in good agreement with the experimental VLE data, need less computation time, and their accuracy is acceptable compared with VLE data calculated by those equations.