Thermodynamics Research Center / ThermoML | Fluid Phase Equilibria

ABSTRACT

The isothermal vapour-liquid and vapour-liquid-liquid equilibria of five binary refrigerant + nalkane 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 activity coefficient model 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 of each of the systems were defined, based upon the characteristics of the critical locus curves within the temperature ranges that were studied. Highlights: Binary static-analytic and variable-volume synthetic phase equilibrium measurements R-23 with n-nonane, n-decane or n-undecane and R-116 with n-nonane or n-decane Thermodynamic models regressed from experimental data Critical locus estimation and van Konynenburg and Scott classification of each of the systems were defined, based upon the characteristics of the critical locus curves within the temperature ranges that were studied.