Classical Ideal Curves of Fluid Mixtures and Their Role for the Development of Equations of State

In this work, the calculation of the so-called classical ideal curves was applied to fluid mixtures. These curves are already established as a tool for the development of equations of state (EOS) in terms of the reduced Helmholtz energy for pure fluids, enabling the assessment of their extrapolation behavior. To optimize model development for mixtures, a detailed investigation of the classical ideal curves calculated from different equations of state for alkane and CO ₂ -alkane mixtures was carried out. Various mixture models were investigated, including the GERG-2008 model of Kunz and Wagner and the cubic equation of Peng and Robinson, which are highlighted in this article. In addition, different mixing approaches were considered within this investigation. As a result, characteristics of the ideal curves of the above-mentioned mixtures were identified, which offer potential as new constraints for fitting mixture models, allowing for a general optimization of the development of equations of state for mixtures.