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Aspen Physical Property System - Physical Property Models

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The mixture surface tension is then calculated as a mole-fraction-weighted<br />

average of these surface tensions.<br />

Parameter Symbol Default MDS Lower Upper Units<br />

Name/Element<br />

Limit Limit<br />

TB T bi — — 4.0 2000.0 TEMPERATURE<br />

SG SG — — 0.1 2.0 —<br />

TC T ci — — 5.0 2000 TEMPERATURE<br />

IAPS Surface Tension for Water<br />

The IAPS surface tension model was developed by the International<br />

Association for Properties of Steam. It calculates liquid surface tension for<br />

water and steam. This model is used in option sets STEAMNBS and STEAM-<br />

TA.<br />

The general form of the equation for the IAPS surface tension model is:<br />

�w=fcn(T, p)<br />

Where:<br />

fcn = Correlation developed by IAPS<br />

The model is only applicable to water. No parameters are required.<br />

General Pure Component Liquid Surface<br />

Tension<br />

The <strong>Aspen</strong> <strong>Physical</strong> <strong>Property</strong> <strong>System</strong> has several submodels for calculating<br />

liquid surface tension. It uses parameter TRNSWT/5 to determine which<br />

submodel is used. See Pure Component Temperature-Dependent Properties<br />

for details.<br />

If TRNSWT/5 is This equation is used And this parameter is<br />

used<br />

0 Hakim-Steinberg-Stiel —<br />

106 DIPPR SIGDIP<br />

301 PPDS SIGPDS<br />

401 IK-CAPE polynomial<br />

equation<br />

505 NIST TDE Watson<br />

equation<br />

3 Transport <strong>Property</strong> <strong>Models</strong> 289<br />

SIGPO<br />

SIGTDEW<br />

511 NIST TDE expansion SIGISTE<br />

512 NIST PPDS14 Equation SIGPDS14<br />

Hakim-Steinberg-Stiel<br />

The Hakim-Steinberg-Stiel equation is:<br />

Where:

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