page_title: Non-random two-liquid model
hierarchical_section_title: Non-random two-liquid model
caption_attribution_description: English: Vapor-Liquid Equilibrium of the Mixture of Chloroform and Methanol with NRTL Fit and Extrapolation to Different Pressures Deutsch: Dampf-Flüssig-Gleichgewicht des Gemischs aus Chloroform und Methanol mit NRTL-Anpassung und Extrapolation zu anderen Drücken
context_page_description: The non-random two-liquid model is an activity coefficient model that correlates the activity coefficients of a compound with its mole fractions in the liquid phase concerned. It is frequently applied in the field of chemical engineering to calculate phase equilibria. The concept of NRTL is based on the hypothesis of Wilson that the local concentration around a molecule is different from the bulk concentration. This difference is due to a difference between the interaction energy of the central molecule with the molecules of its own kind and that with the molecules of the other kind. The energy difference also introduces a non-randomness at the local molecular level. The NRTL model belongs to the so-called local-composition models. Other models of this type are the Wilson model, the UNIQUAC model, and the group contribution model UNIFAC. These local-composition models are not thermodynamically consistent for a one-fluid model for a real mixture due to the assumption that the local composition around molecule i is independent of the local composition around molecule j. This assumption is not true, as was shown by Flemr in 1976.
context_section_description: The non-random two-liquid model (abbreviated NRTL model) is an activity coefficient model that correlates the activity coefficients  of a compound with its mole fractions  in the liquid phase concerned. It is frequently applied in the field of chemical engineering to calculate phase equilibria. The concept of NRTL is based on the hypothesis of Wilson that the local concentration around a molecule is different from the bulk concentration. This difference is due to a difference between the interaction energy of the central molecule with the molecules of its own kind  and that with the molecules of the other kind . The energy difference also introduces a non-randomness at the local molecular level. The NRTL model belongs to the so-called local-composition models. Other models of this type are the Wilson model, the UNIQUAC model, and the group contribution model UNIFAC. These local-composition models are not thermodynamically consistent for a one-fluid model for a real mixture due to the assumption that the local composition around molecule i is independent of the local composition around molecule j. This assumption is not true, as was shown by Flemr in 1976.  However, they are consistent if a hypothetical two-liquid model is used.
caption: VLE of the mixture of chloroform and methanol plus NRTL fit and extrapolation to different pressures
exif: {}