Prediction of the viscosity of dense fluid mixtures

Abstract

The Vesovic-Wakeham (VW) method of predicting the viscosity of dense fluid mixtures has been improved by implementing new mixing rules based on the rigid sphere formalism. The proposed mixing rules are based on both Lebowitz's solution of the Percus-Yevick equation and on the Carnahan-Starling equation. The predictions of the modified VW method have been compared with experimental viscosity data for a number of diverse fluid mixtures:natural gas, hexane + hheptane, hexane + octane, cyclopentane + toluene, and a ternary mixture of hydrofluorocarbons (R32 + R125 + R134a). The results indicate that the proposed improvements make possible the extension of the original VW method to liquid mixtures and to mixtures containing polar species, while retaining its original accuracy.

Reference Correlation of the Viscosity of meta-Xylene from 273 to 673 K and up to 200 MPa

“…Nevertheless, the proposed correlation is well-behaved within the two-phase region, where no data are available to constrain the correlation; for all isotherms, viscosity exhibits monotonic increase with density except at low densities, of up to 1.0 mol l -1 , where the decreasing initial-density dependence extends into the two-phase region. The behavior at densities corresponding to the two-phase region makes the present correlation suitable as the basis of developing a reference corresponding-states correlation for cyclic hydrocarbons 92 or as part of the VW model [97][98][99] to predict the viscosity of mixtures containing m-xylene. Figure 11 summarize the deviations of the selected secondary data, consisting of at least four data points, measured at atmospheric pressure, from the current correlation.…”

“…Hence, it precludes their use in corresponding states 92 or in VW models. [97][98][99] In this work we have constrained the fitting of the experimental viscosity data in such a way that the resulting correlation within the two-phase region is a continuous, monotonically increasing function of density at all temperatures, except at low densities where the decreasing initial-density dependence extends partially into the two-phase region. The residual viscosity is represented as a function in reduced temperature, T r =T/T c , and reduced density, ρ r = ρ/ρ c , as,…”

Reference Correlation of the Viscosity of Cyclohexane from the Triple Point to 700 K and up to 110 MPa

“…Nevertheless, the proposed correlation is well-behaved within the two-phase region, where no data are available to constrain the correlation; for all isotherms, viscosity exhibits a monotonic increase with density. The behavior at densities corresponding to the two-phase region makes the present correlation suitable as the basis of developing a reference corresponding-states correlation for cyclic hydrocarbons 210 or as part of the VW model [222][223][224] to predict the viscosity of mixtures containing cyclohexane. …”

“…Hence, it precludes their use in corresponding states 210 or in VW models. [222][223][224] In this work, we have constrained the fitting of the experimental viscosity data in such a way that the resulting correlation within the two-phase region is a continuous, monotonically increasing function of density at all temperatures.…”

Reference Correlation of the Viscosity of n-Hexadecane from the Triple Point to 673 K and up to 425 MPa

“…Nevertheless, the proposed correlation is well-behaved within the two-phase region, where no data are available to constrain the correlation; for all isotherms, viscosity exhibits monotonic increase with density except at low densities, of up to 0.7 mol L -1 , where the decreasing initial-density dependence extends into the two-phase region. The behavior at densities corresponding to the two-phase region makes the present correlation suitable as the basis of developing a reference corresponding-states correlation for n-alkanes [114][115] or as part of the VW model [120][121][122] to predict the viscosity of mixtures containing n-hexadecane. Based on deviations of the primary data, we have estimated the overall uncertainty of the correlation defined as the combined expanded uncertainty with a coverage factor of 2 as follows: (i) in the liquid phase we estimate the uncertainty to be 2.5%, except at atmospheric pressure or below where we estimate it to be 1% (ii)…”