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Aspen Physical Property System - Physical Property Models

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Van Laar Activity Coefficient Model<br />

The Van Laar model (Van Laar 1910) calculates liquid activity coefficients for<br />

the property methods: VANLAAR, VANL-2, VANL-HOC, VANL-NTH, and VANL-<br />

RK. It can be used for highly nonideal systems.<br />

Where:<br />

zi<br />

Ai<br />

Bi<br />

Ci<br />

Aij<br />

Cij<br />

178 2 Thermodynamic <strong>Property</strong> <strong>Models</strong><br />

=<br />

=<br />

=<br />

=<br />

=<br />

=<br />

Cij = Cji<br />

Aii = Bii = Cii = 0<br />

aij and bij are unsymmetrical. That is, aij may not be equal to aji, and bij may<br />

not be equal to bji.<br />

Parameters Symbol DefaultMDS Lower Limit Upper<br />

Name/Element<br />

Limit<br />

VANL/1 a ij 0 x -50.0 50.0 —<br />

Units<br />

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

VANL/3 c ij 0 x -50.0 50.0 —<br />

VANL/4 d ij 0 x -15000.0 15000.0 TEMPERATURE<br />

The VANL-2 property method uses data set 2 for VANL. All other Van Laar<br />

methods use data set 1.<br />

References<br />

J.J. Van Laar, "The Vapor Pressure of Binary Mixtures," Z. Phys. Chem., Vol.<br />

72, (1910), p. 723.<br />

R.C. Reid, J.M. Prausnitz, and B.E. Poling, The Properties of Gases and<br />

Liquids, 4th ed. (New York: McGraw-Hill, 1987).

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