.MultiPhaseMixture.Interfaces.ActivityCoefficient

Information

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

Overview

In a solution the activity coefficent is a measure of how much the mixture differs from an ideal solution. For an ideal solution the activity coefficent gamma=1.

Definition

gamma_i=f_i/(xi*f0_i)

where

f_i= fugacity of component i in mixture

xi=mole fraction of species i in vapor phase

f0_i= standard fugacity of pure component i

Usage

The acitivity coefficient is used as an alternative to an equation of state method to derive properties for calculation of phase equilibrium. It's typically used for highly-nonlinear liquids at low pressure such as alcohol-water mixtures where equation of states methods such as Redlich-Kwong-Soave don't give satisfactory result.

References

[1] Chemical Engineering Therodynamics, Pradeep Ahuja, 2009,

[2] Aspen Physical Property System, Physical Property Methods and Models 11.1

Note