Determination of Group Contributions
Group contributions are obtained from known experimental data of well defined pure components and mixtures. Common sources are thermophysical data banks like the Dortmund Data Bank, Beilstein database, or the DIPPR data bank (from AIChE). The given pure component and mixture properties are then assigned to the groups by statistical correlations like e. g. (multi-)linear regression.
Important steps during the development of a new method are the
- evaluation of the quality of available experimental data, elimination of wrong data, finding of outliers
- construction of groups
- searching additional simple and easily accessible properties that can be used to correlate the sum of group contributions with the examined property
- finding a good but simple mathematical equation for the relation of the group contribution sum with the wanted property. The critical pressures, for example, is often determined as Pc=f(ΣGi2)
- fitting the group contribution
The reliability of a method mainly relies on a comprehensive data bank where sufficient source data have been available for all groups. A small data base may lead to a precise reproduction of the used data but will lead to significant errors when the model is used for the prediction of other systems.
Read more about this topic: Group Contribution Method
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