Equation of State and Real Gas Factor

In the industry, predominantly cubic equations of state are used, because a large number of coefficients are tabulated (Table 15.2). They can be reduced back to a basic equation  

a and b are material-specific parameters that are adapted to measured data or can be calculated from the thermodynamic critical data of the gas  

The real gas factor Z is calculated from the equation of state by adjustment of Eq. (15.22) with the specific volume v = ZRTfp. Eor example, for the Soave-Redlich-Kwong equation, we have 

The thermodynamic critical data of certain gases are reproduced in Table 15.4. 

Nearby the thermodynamic critical temperature (T, = 1.05), the real gas factor drops off, at first very strongly, reaches a minimum at a reduced pressure of somewhat over 1, and then increases again. The further away the temperature of the gas is from the thermodynamic critical point, the less strongly pronounced the minimum is. 

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