Aspen Physical Property System - Physical Property Models

Binary Parameters
158 2 Thermodynamic Property Models
(27)
The adjustable binary parameters for these models include moleculemolecule,
molecule-electrolyte, and electrolyte-electrolyte binary parameters,
where electrolyte here means an ion-pair composed of a cationic species and
an anionic species. For each of these types, there are asymmetric binary
interaction energy parameters, �, and symmetric non-random factor
parameters, � (for calculating G). That is to say that the following are the
adjustable parameters:
(28)
However, as seen in the preceding equations, we need these parameters for
molecule-molecule, molecule-cation, molecule-anion, and cation-anion pairs.
The molecule-molecule parameters are given directly by the model's
adjustable binary parameters. The remaining parameters �cm, �am, �mc, �ma,
�ca, �ac, �cm, �am, �mc, �ma, �ca, and �ac, are calculated from these parameters.
The � parameters for pairs involving cations and anions are calculated from
the adjustable binary parameters by applying a simple composition-average
mixing rule.
(29)
(30)
(31)
(32)
where Yc is a cationic charge composition fraction and Ya is an anionic charge
composition fraction, defined as follows:
(33)