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Unphysical critical curves of binary mixtures predicted with GERG models



Ian H. Bell, Ulrich K. Deiters


When applied to asymmetric binary mixtures (e.g., methane + pentane or heavier alkanes, hydrogen-containing mixtures), the GERG equation of state (GERG-2004 or GERG-2008) predicts critical curves with physically unreasonable temperature maxima above the critical temperature of the heavier component. These maxima are associated with physically impossible vapor–liquid equilibria. The phenomenon is probably caused by corrections for critical anomalies that were built into the empirical pure-fluid equations of state forming the foundation of the GERG model. These corrections ensure that the model represents thermodynamic data of pure fluids quite well even close to their critical points. For mixtures, however, the corrections can cause artifacts.
International Journal of Thermophysics


critical points, mixtures, thermodynamics


Bell, I. and Deiters, U. (2020), Unphysical critical curves of binary mixtures predicted with GERG models, International Journal of Thermophysics, [online], (Accessed May 20, 2024)


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Created October 18, 2020, Updated October 20, 2020