Crate unifac[][src]

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The unifac crate allows to calculate non-ideal vapor-liquid-equilibria (VLE) using the Universal Quasichemical Functional Group Activity Coefficients (UNIFAC) model. This model, first published by Fredenslund et. al. in November 1975 in AIChE Journal, calculates the fractions of each substance in a mixture for a given temperature. Therefore, it only requires each subtance to be described as a combination of functional groups. Relying on empirical data for these groups, the model does not need substance-specific data. Therefore, it can be used to predict VLE without any further substance / mixture specific data.

The following table explains used terms in this crate

SubstanceA chemical substance, based on covalent bonds (e.g. ethane C2H6)
Functional GroupA characteristic group of bonded atoms in organic substances. These are pre-defined by UNIFAC model.
MixtureA set of substances, leading to a VLE at given temperature.


As UNIFAC model itself, unifac crate will calculate results even if the given mixture does not have a VLE present at all or at given temperature. The project owners / devs / users are required to make sure the calculated results do apply.


All UNIFAC parameters are obtained from UNIFAC Consortium as published here. These parameters are published originally within the following articles:

Skjold-Joergensen S., Kolbe B., Gmehling J., Rasmussen P., “Vapor-Liquid Equilibria by UNIFAC Group Contribution. Revision and Extension”, Ind.Eng.Chem. Process Des.Dev., 18(4), 714-722, 1979
Gmehling J., Rasmussen P., Fredenslund Aa., “Vapor-Liquid Equilibria by UNIFAC Group Contribution. Revision and Extension. 2”, Ind.Eng.Chem. Process Des.Dev., 21(1), 118-127, 1982
Macedo E.A., Weidlich U., Gmehling J., Rasmussen P., “Vapor-Liquid Equilibria by UNIFAC Group-Contribution. Revision and Extension. 3”, Ind.Eng.Chem. Process Des.Dev., 22(4), 676-678, 1983
Tiegs D., Gmehling J., Rasmussen P., Fredenslund A., “Vapor-Liquid Equilibria by UNIFAC Group Contribution. 4. Revision and Extension”, Ind.Eng.Chem.Res., 26(1), 159-161, 1987
Hansen H.K., Rasmussen P., Fredenslund A., Schiller M., Gmehling J., “Vapor-Liquid Equilibria by UNIFAC Group-Contribution. 5. Revision and Extension”, Ind.Eng.Chem.Res., 30(10), 2352-2355, 1991
Wittig R., Lohmann J., Gmehling J., “Vapor-Liquid Equilibria by UNIFAC Group Contribution. 6. Revision and Extension”, Ind.Eng.Chem.Res., 42(1), 183-188, 2003

As cited from DDBST. Used parameters have been fetched on Oct 6, 2020.

Please not that all data is created by the listed articles’ authors and maintained by DDBST / UNIFAC Consortium. When using this crate, you are required to reference to not only the crate but also the data sources.



Functional group as building block of a substance


A substance within a VLE



Calculates activity coeficients for the given mixture