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Aspen Physical Property System - Physical Property Models

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Debye-Hückel Volume<br />

The Debye-Hückel model calculates liquid molar volume for aqueous<br />

electrolyte solutions.<br />

The equation for the Debye-Hückel volume model is:<br />

Where:<br />

�<br />

Vk is the molar volume for water and is calculated from the ASME steam<br />

table.<br />

Vk is calculated from the Debye-Hückel limiting law for ionic species. It is<br />

assumed to be the infinite dilution partial volume for molecular solutes.<br />

Where:<br />

�<br />

Vk = Partial molar ionic volume at infinite dilution<br />

zk = Charge number of ion k<br />

Av = Debye-Hückel constant for volume<br />

b = 1.2<br />

I =<br />

mk = Molarity of ion k<br />

Av is computed as follows:<br />

Where:<br />

2 Thermodynamic <strong>Property</strong> <strong>Models</strong> 201<br />

the ionic strength, with<br />

A� = Debye-Hückel constant for the osmotic<br />

coefficients (Pitzer, 1979)<br />

�w = Density of water (kg / m 3 )<br />

�w = Dielectric constant of water (Fm -1 ), a function<br />

of pressure and temperature (Bradley and<br />

Pitzer, 1979)<br />

Parameter Name Applicable<br />

Components<br />

Symbol Default Units<br />

VLBROC Ions, molecular Solutes �<br />

Vk 0 MOLE-VOLUME

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