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A theoretically based departure function for multi-fluid mixture models



Ian H. Bell, Andreas Jaeger, Cornelia Breitkopf


Multi-fluid models for highly accurate multiparameter equations of state have been applied very successfully in the past years in order to accurately model thermophysical properties of mixtures. However, the predictive capabilities of this type of mixture model is rather limited, as demonstrated in this work. Therefore, a new model is proposed, which is a combination of the multi-fluid model with excess Gibbs energy models. This new approach results in a theoretically based formulation for the so-called departure function of the multi-fluid model. It is shown that the new model yields very good results for the description of binary mixtures of the components ethanol, ethane, carbon dioxide, propylene, and benzene. While the state-of-the-art multi-fluid model with predictive linear or Lorenth-Berthelot mixing rules for the parameters of the reducing functions does not represent the phase equilibria for the investigated binary mixtures well, and in case of the azeotropes predicts quantitatively wrong mixture behavior, the new model is capable of accurately representing the phase equilibria of all binary mixtures investigated.
Fluid Phase Equilibria


Bell, I. , Jaeger, A. and Breitkopf, C. (2018), A theoretically based departure function for multi-fluid mixture models, Fluid Phase Equilibria, [online], (Accessed June 16, 2024)


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Created August 15, 2018, Updated June 2, 2021