Aspen Physical Property System - Physical Property Models

Where:
�i
2 Thermodynamic Property Models 93
= Activity coefficient of component i
�i SG = Staverman-Guggenheim model for combinatorial
contribution to �i
�i(�m)
�S(�m)
pi(�m)
pi(�m)
�
�W(�m,�n)
�W HB (�m,�n)
= Segment activity coefficient of segment �m in
component i
= Segment activity coefficient of segment �m in
solvent mixture
= Sigma profile of component i
= Sigma profile of solvent mixture
= Surface charge density
= Exchange energy between segments �m and �n
= Hydrogen-bonding contribution to exchange energy
between segments �m and �n
z = Coordination number, 10
Vi
Ai
aeff
Veff
Aeff
�'
= Molecular volume of component i
= Molecular surface area of component i
= Standard segment surface area, 7.50 Å 2
= Standard component volume, 66.69 Å 3
= Standard component surface area, 79.53 Å 2
= Misfit energy constant
The Cosmo-SAC model does not require binary parameters. For each
component, it has six input parameters. CSACVL is the component volume
parameter which is always defined in cubic angstroms, regardless of chosen
units sets. SGPRF1 to SGPRF5 are five component sigma profile parameters;
each can store up to 12 points of sigma profile values. All six input
parameters are obtained from COSMO calculation. The Aspen Physical
Property System includes a database of sigma profiles for over 1400
compounds from Mullins et al. (2006). The parameters were obtained by
permission from the Virginia Tech Sigma Profile Database website
(http://www.design.che.vt.edu/VT-2004.htm). Aspen Technology, Inc. does
not claim proprietary rights to these parameters.
Note: Starting in version V7.2, additional parameters SGPRF6 through
SGPRF9 and SGPR10 through SGPR14 are available in Aspen Plus and
Aspen Properties, as part of a planned expansion to allow larger sigma
profiles to be used. However, the model is not yet updated to use these
parameters and you should not yet try to use sigma profiles larger than 51
elements.