2PVDW model

This results in the selection of 2PVDW model for the VLE calculations. Next the message below will appear on the screen.) 

S, Nonquadracic Combining Rules for the van der Waals One-Fluid Model (2PVDW Model) 

The combinations of eqns. (3.3.4, 3.3.6, 3.3.8, and 3.5.5) will be referred to as the 2PVDW model. This model has been shown to provide a good correlation of VLE data of highly nonideal systems that previously could be correlated only with activity coefficient models. 

For highly nonideal and polar mixtures of organic compounds, the IPVDW model is inadequate, and the various forms of the 2PVDW model have limitations as a correlative method and suffer from computational problems such as the dilution effect and the Michelsen-Kistenmacher syndrome mentioned in Section 3.5. Such models should only be used with caution as semipredictive methods, and they have little utility as 

With this selection, the user can enter new VLE data from the keyboard, or use previously entered VLE data for correlation with IPVDW or 2PVDW models.) 

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