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Aspen Physical Property System - Physical Property Models

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Letsou-Stiel<br />

The Letsou-Stiel model calculates liquid viscosity at high temperatures for<br />

0.76 � Tr � 0.98. This model is used in PCES.<br />

Note: Reduced temperature Tr is always calculated using absolute<br />

temperature units.<br />

The general form for the model is:<br />

� l � = (� l �) 0 + �(� l �) 1<br />

Where:<br />

(� l �) 0 =<br />

(� l �) 1 =<br />

�<br />

�<br />

3 Transport <strong>Property</strong> <strong>Models</strong> 265<br />

=<br />

=<br />

Parameter<br />

Name/Element<br />

Symbol Default MDS Lower<br />

Limit<br />

Upper<br />

Limit<br />

MW M i — — 1.0 5000.0 —<br />

Units<br />

TC T ci — — 5.0 2000.0 TEMPERATURE<br />

PC p ci — — 10 5<br />

OMEGA � i<br />

References<br />

10 8<br />

— — -0.5 2.0 —<br />

PRESSURE<br />

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

Liquids, 4th ed., (New York: McGraw-Hill, 1987), p. 471.<br />

Lucas Vapor Viscosity<br />

The equation for the Lucas vapor viscosity model is:<br />

Where the dimensionless low pressure viscosity is given by:<br />

The dimensionless-making group is:<br />

The pressure correction factor Y is:

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