Modeling Phase Behavior with the Peng-Robinson Equation of State

Modeling Phase Behavior with the Peng-Robinson Equation of State 

The Peng-Robinson equation of state (eos) [27] is one of the most frequently used semi-empirical cubic equations of state, and is able to describe high-pressure and supercritical fluid systems. The Peng-Robinson eos expresses pressure as a summation of a repulsive term and a attractive term and is given by 

For the description of multi-component systems, the parameters a and b can be obtained from mixing rules  

Various expressions have been proposed for the cross coefficients a,j and hij, which are shown in Table 14.2. 

It includes an excess Helmholtz free energy at infinite pressure, which allows the mixing rale to consist of interaction parameters, equation-of-state coefficients and mole fractions only. 

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