Model Comparison

Relative deviations between experimental and predicted data for 3300 consistent VLE data sets

A comparison of the results obtained from original UNIFAC and Modified UNIFAC (Dortmund) demonstrates the improvements already obtained for Modified UNIFAC (Dortmund). This is illustrated in the figures above:
The first figure shows the calculated deviations in vapor mole fraction y, temperature T and pressure P for 3300 thermodynamically consistent isothermal / isobaric VLE data sets.

Besides the predictions using UNIFAC and Modified UNIFAC (Dortmund), the results obtained by a direct fit of the VLE data using the UNIQUAC method are given. It can be seen from deviations between the direct fit and the prediction that the error is reduced dramatically for all three criteria when UNIFAC or especially Modified UNIFAC (Dortmund) is used.

Assembly ideal behavior (Raoults law) enlarges the errors by a factor of 5 compared to Modified UNIFAC (Dortmund).
Similar improvements of the predictiv capability are also achieved for process enthalpies, activity coefficients at infinite dilution (see second figure), liquid-liquid equilibria, azeotropic data and solid-liquid equilibria of eutectic systems.

Relative deviations between experimental and predicted activity coefficients at infinite diluton (data base: 12 600 data points)*