Mixing rules
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Mixing rules
[edit] van der Waals mixing rules
The van der Waals equation of state can be written as
\[\left(p + \frac{an^2}{V^2}\right)\left(V-nb\right) = nRT\]
For mixtures one replaces \(a\) and \(b\) with expressions that depend on the composition:
\[a \rightarrow \sum_i^n \sum_j^n x_i x_j a_{ij}\]
and
\[b \rightarrow \sum_i^n \sum_j^n x_i x_j b_{ij}\]
where
\[a_{ij} = (1-k_{ij}) \sqrt{(a_{ii} a_{jj})} ~~~~~~~~ i\neq j\]
and
\[b_{ij} = \frac{(b_{ii} b_{jj})}{2} ~~~~~~~~ i\neq j\]
where \(k_{ij}\) is obtained from a fit.
See also
[edit] References
- ↑ T. W. Leland, J. S. Rowlinson, G. A. Sather and I. D. Watson "Statistical thermodynamics of two-fluid models of mixtures", Transactions of the Faraday Society 65 pp. 2034-2043 (1969)
- Related reading
- T. Y. Kwak and G. A. Mansoori "Van der waals mixing rules for cubic equations of state. Applications for supercritical fluid extraction modelling", Chemical Engineering Science 41 pp. 1303-1309 (1986)
- Kenneth R. Hall, Gustavo A. Iglesias-Silva, and G. Ali Mansoori "Quadratic mixing rules for equations of state: Origins and relationships to the virial expansion", Fluid Phase Equilibria 91 pp. 67-76 (1993)
