Aspen Physical Property System - Physical Property Models

‡ RKUC0, RKUC1, and RKUC2 are treated as having units m 3 /kmol. No unit
conversion to other molar volume units is done.
References
G. Soave, "Equilibrium Constants for Modified Redlich-Kwong Equation-ofstate,"
Chem. Eng. Sci., Vol. 27, (1972), pp. 1196 - 1203.
J. Schwartzentruber and H. Renon, "Extension of UNIFAC to High Pressures
and Temperatures by the Use of a Cubic Equation-of-State," Ind. Eng. Chem.
Res., Vol. 28, (1989), pp. 1049 – 1955.
A. Peneloux, E. Rauzy, and R. Freze, "A Consistent Correction For Redlich-
Kwong-Soave Volumes", Fluid Phase Eq., Vol. 8, (1982), pp. 7–23.
Soave-Redlich-Kwong
The Soave-Redlich-Kwong equation-of-state is the basis of the SRK property
method. This model is based on the same equation of state as the Redlich-
Kwong-Soave model. However, this model has several important differences.
� A volume translation concept introduced by Peneloux and Rauzy is used to
improve molar liquid volume calculated from the cubic equation of state.
� Improvement in water properties is achieved by using the NBS Steam
Table.
� Improvement in speed of computation for equation based calculation is
achieved by using composition independent fugacity.
� Optional Kabadi-Danner mixing rules for improved phase equilibrium
calculations in water-hydrocarbon systems (see SRK-Kabadi-Danner)
� Optional Mathias alpha function
Note: You can choose any of the available alpha functions, but you cannot
define multiple property methods based on this model using different alpha
functions within the same run.
This equation-of-state can be used for hydrocarbon systems that include the
common light gases, such as H2S, CO2 and N2.
The form of the equation-of-state is:
Where:
a0 is the standard quadratic mixing term:
Where:
2 Thermodynamic Property Models 59
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