Mixture Properties from Helmholtz Energy Equations of State

2 Mixture Properties from Helmholtz Energy Equations of State 

The Helmholtz energy for mixtures of fluids can be calculated with the equation 

In this equation, C is the number of components in the mixture, A i is the ideal gas Helmholtz energy for component i, and is the pure fluid residual Helmholtz energy of component i evaluated at a reduced density and temperature defined below. 

The excess contribution to the Helmholtz energy from mixing is 

All single-phase thermodynamic properties can be calculated from the Helmholtz energy as described in Sec. 12.5 with the relations 

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