Shape Factors from Generalized Equations of State

3 Shape Factors from Generalized Equations of State 

Although we do not normally think of these modified van der Waals types of equations of state in terms of shape factors, they all contain a prescription for their determination. To illustrate this, consider the Soave-Redlich-Kwong equation discussed in Chapter 4 and given as 

The parameters Qa and are universal for this equation of state and m (o) is a simple quadratic function of the acentric factor. The residual compressibility factor and dimensionless residual Helmholtz energy are given by 

An examination of the corresponding-states relations, eqs 6.29 and 6.31 show that, if the equivalent-substance reducing ratios are given by 

As an example of a more complex modified van der Waals-type model, we have also made shape factor calculations with the generalizied Camahan-Star-ling-De Santis (GCSD) equation which in dimensionless residual form is given by 

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