Isothermal vapour-liquid equilibrium data for the binary systems of CHF3 with (n-nonane, n-decane, or n-undecane) and C2F6 with (n-nonane or n-decane)

Abstract

The isothermal vapour-liquid and vapour-liquid-liquid equilibria of five binary refrigerant + n-alkane systems at near ambient temperatures were measured using a static-analytic apparatus and a static-synthetic apparatus. The phase equilibrium data for the systems of trifluoromethane (R-23) + n-nonane and hexafluoroethane (R-116) + n-decane were measured using the static-analytic apparatus, whereas bubble point data were measured with the static-synthetic apparatus for the systems of R-23 + n-decane, R-23 + n-undecane and R-116 + n-nonane. The temperatures that were investigated for these systems ranged between (272.9 and 323.1) K.The experimental phase equilibrium data were modelled with the PR EOS and the MC alpha function. The WS mixing rule, incorporating either the NRTL or the UNIQUAC activity coefficient model, was used to apply the model to the mixture data. The temperature independent forms of the thermodynamic model were found to provide a more accurate representation of the experimental data than the temperature dependent forms. A single mixture critical point was determined using the indirect extended scaling laws of Ungerer et al. (2005). The calculation procedure of Heidemann and Khalil (1980) was used to estimate segments of the critical locus curves for the binary systems for which data were measured close to the critical locus curve. The van Konynenburg and Scott classification for each system was defined, based upon the characteristics of the critical locus curves within the temperature ranges that were studied.