Liquid Density of Alkanes and Halogenated Alkanes Mixtures in a Corresponding States Format

The Corresponding States (CS) density models for mixture proposed here, one for saturated and one for compressed liquid, are analytically similar to the pure fluid liquid density exposed in the former paper, but now with critical constants and 8,, replacing wm , as from the mixing rules. The mixing rules present two adjustable interaction coefficients for each binary pair, but they are set to unity making the two models completely predictive: both in fact do not preliminarily require any density data for the mixture of interest. To improve the prediction accuracy a correlative mode is here proposed in which the om parameter is substituted with a 8,, (x) function which parameters are regressed from saturated liquid data, when available, for the binary mixture of interest. The two models are validated with mixtures experimental data for the families of alkanes and hydrofluoroalkanes (HFC) and the prediction accuracy obtained is significatively better with respect to the existing predictive liquid density models for mixtures. The result is particularly useful for the studies about the new generation refrigerants applications. INTRODUCTION The prediction of thermodynamic properties of pure fluids and mixtures through accurate models is essential for the study and design of refrigeration components and systems. The need for these models is greatly increased in the last times particularly for alkanes and halogenated alkanes mixtures due to their interest as new generation refrigerants. In the present work a three parameters CS model is proposed for the saturated and compressed liquid density prediction of alkanes and HFC mixtures. For both these two families of fluids a conformality has been formerly ascertained by the Authors, as it is required in a CS domain modelling. DENSITY MODEL Mixture Models The density of a saturated liquid mixture is represented through a model which structure is similar to that used for the pure fluids [ l]: logpr,si(T,o) = Iogpr)c!)(:z;_) + ~~ [1ogpr,)c2)(:z;_ )-logpr)ct)(r,. )] r (1) In this equation with cl and c2 are indicated the mixture components and their reduced saturated liquid densities Pr,sl are obtained from the pure fluid model formerly proposed in [I]. In eq. (1) 5 and or are both obtained from the definition of 5, already utilized in the same pure fluids density models: [ (P:), l 5 = -log10 (p:) 1 ~