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Aspen Physical Property System - Physical Property Models

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References<br />

G.M. Wilson, J. Am. Chem. Soc., Vol. 86, (1964), p. 127.<br />

Wilson Model with Liquid Molar Volume<br />

This Wilson model (used in the method WILS-VOL) calculates liquid activity<br />

coefficients using the original formulation of Wilson (Wilson 1964) except that<br />

liquid molar volume is calculated at system temperature, instead of at 25�C.<br />

It is recommended for highly nonideal systems, especially alcohol water<br />

systems. It can be used in any activity coefficient property method or in the<br />

advanced equation of state mixing rules, such as Wong Sandler and MHV2.<br />

This model cannot be used for liquid liquid equilibrium calculations.<br />

The equation for the Wilson model is:<br />

Where:<br />

ln Aij<br />

2 Thermodynamic <strong>Property</strong> <strong>Models</strong> 181<br />

=<br />

Vj and Vi are pure component liquid molar volume at the system temperature<br />

calculated using the General Pure Component Liquid Molar Volume model. The<br />

extended form of ln Aij provides more flexibility in fitting phase equilibrium<br />

and enthalpy data. aij, bij, cij, dij, and eij are unsymmetrical. That is, aij may<br />

not be equal to aji, etc.<br />

The binary parameters aij, bij, cij, dij, and eij must be determined from data<br />

regression of VLE and/or heat-of-mixing data. There are no built in binary<br />

parameters for this model.<br />

Parameter<br />

Name/Element<br />

SymbolDefault MDS Lower<br />

Limit<br />

Upper<br />

Limit<br />

WSNVOL/1 a ij 0 x -50.0 50.0 —<br />

†<br />

Units<br />

WSNVOL/2 b ij 0 x -15000.0 15000.0 TEMPERATURE<br />

††<br />

WSNVOL/3 c ij 0 x — — TEMPERATURE<br />

††<br />

WSNVOL/4 d ij 0 x — — TEMPERATURE<br />

††<br />

WSNVOL/5 e ij 0 x — — TEMPERATURE<br />

††<br />

WSNVOL/6 T lower 0 K x — — TEMPERATURE<br />

WSNVOL/7 T upper 1000 K x — — TEMPERATURE<br />

Pure component parameters for the General Pure Component Liquid Molar<br />

Volume model are also required.<br />

† In the original formulation of the Wilson model, aij = cij = dij = eij = 0 and<br />

. Vj and Vi are calculated at 25�C.

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