Aspen Physical Property System - Physical Property Models

2 Thermodynamic Property Models 121
(15)
(16)
where I is the component index, i is the segment index, ri,I is the number of
segment i in component I, xI is the mole fraction of component I, xi is the
segment fraction of segment i, and ns is the total number of all segments in
the system.
Since there is only a single 1-1 electrolyte segment, the pair parameters
between a molecular segment and the electrolyte segment can be simplified
as follows:
We can then rewrite the excess Gibbs free energy as follows:
with
(17)
(18)
(19)
(20)
(21)
(22)
The local composition contribution to the segment activity coefficient can be
calculated as follows:
(23)
The local composition contribution to the activity coefficients for molecular
segments, the cationic segment, and the anionic segment can be calculated
out as follows: