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Aspen Physical Property System - Physical Property Models

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Extended Antoine Equation<br />

Parameters for many components are available for the extended Antoine<br />

equation from the <strong>Aspen</strong> <strong>Physical</strong> <strong>Property</strong> <strong>System</strong> pure component databank.<br />

This equation can be used whenever the parameter PLXANT is available.<br />

The equation for the extended Antoine vapor pressure model is:<br />

Extrapolation of ln pi *,l versus 1/T occurs outside of temperature bounds.<br />

Parameter<br />

Name/ Element<br />

2 Thermodynamic <strong>Property</strong> <strong>Models</strong> 183<br />

Symbol Default MDS Lower<br />

Limit<br />

Upper<br />

Limit<br />

Units<br />

PLXANT/1 C 1i x PRESSURE,<br />

TEMPERATURE<br />

PLXANT/2 C 2i x TEMPERATURE<br />

PLXANT/3, . . . , 7 C 3i, ..., C 7i 0 x TEMPERATURE<br />

PLXANT/8 C 8i 0 x TEMPERATURE<br />

PLXANT/9 C 9i 1000 x TEMPERATURE<br />

If C5i, C6i, or C7i is non-zero, absolute temperature units are assumed for all<br />

coefficients C1i through C7i. The temperature limits are always in user input<br />

units.<br />

Barin<br />

See Barin Equations for Gibbs Energy, Enthalpy, Entropy, and Heat Capacity<br />

for details about this submodel.<br />

Wagner Vapor Pressure Equation<br />

The Wagner vapor pressure equation is the best equation for correlation. The<br />

equation can be used if the parameter WAGNER is available:<br />

Where:<br />

Tri = T / Tci<br />

pri *,l = pi *,l / pci<br />

Linear extrapolation of ln pi *,l versus T occurs outside of temperature bounds.<br />

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

temperature units.<br />

PPDS Modified Wagner Vapor Pressure Equation<br />

The PPDS equation also uses the same parameter WAGNER as the standard<br />

Wagner equation:

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