.MultiPhaseMixture.Interfaces.Fugacity

Information

Model that calculates the fugacity coefficient for each phase. To avoid an extra iteration (the fugacitymay be a function of p,T or d,T) the inputs are p,T,d and overall molar substance for the specified phase.

Background information

Fugacity is the effective pressure which replaces the true mechanical pressure in accurate chemical equilibrium calculations.

Definition

The fugacity of species i in a mixture, is defined with reference to the ideal gas mixture as follows:

f_i(T,P,x)=x_i*P*exp*(1/(RT)*integral_0_to_P(V_i-V_i_IGM)dp)

Fugacities can be determined from an equation of state or determined experimentally. When the pressure goes to zero all mixtures become ideal gas mixtures.

Usage

Fugacities or more often the logFugacityCoefficient arises often in thermodynamic models due to it's part of one of rthe criteria for phase equilibrium:

f_i_V=f_i_L (fugacity of component i in all present phases should be equal)

The logarithmic fugacity coefficient is the natural quantity that arises from most thermodynamic models of mixtues . Unlike the fugacity itself this quantity is also well-concentration of a compound and the logarithmic form allows a wider range of numerical values to be represented [2]

References

[1] Chemical and engineering thermodynamics, third edition, Stanley I. Sandler

[2] CAPE-OPEN, Thermodynamic and Physical Properties v1.1