Aspen Physical Property System - Physical Property Models

Where:
The parameter is the mole fraction vector; fcn is a corresponding states
correlation based on the model for vapor and liquid viscosity TRAPP, by the
National Bureau of Standards (NBS, currently NIST) . The model can be used
for both pure components and mixtures. The model should be used for
nonpolar components only.
Parameter
Name/Element
3 Transport Property Models 267
Symbol Default MDS Lower
Limit
Upper
Limit
MW M i — — 1.0 5000.0 —
Units
TCTRAP T ci TC x 5.0 2000.0 TEMPERATURE
PCTRAP p ci PC x 10 5
10 8
PRESSURE
VCTRAP V ci VC x 0.001 3.5 MOLE-VOLUME
ZCTRAP Z ci ZC x 0.1 1.0 —
OMGRAP � i
References
OMEGA x -0.5 3.0 —
J.F. Ely and H.J.M. Hanley, "Prediction of Transport Properties. 1. Viscosities
of Fluids and Mixtures," Ind. Eng. Chem. Fundam., Vol. 20, (1981), pp. 323–
332.
Twu Liquid Viscosity
The Twu liquid viscosity model is based upon the work of C.H. Twu (1985).
The correlation uses n-alkanes as a reference fluid and is capable of
predicting liquid viscosity for petroleum fractions with normal boiling points up
to 1340 F and API gravity up to -30.
Given the normal boiling point Tb and the specific gravity SG of the system to
be modeled, the Twu model estimates the viscosity of the n-alkane reference
fluid of the same normal boiling point at 100 F and 210 F, and its specific
gravity. These are used to estimates the viscosity of the system to be
modeled at 100 F and at 210 F, and these viscosities are used to estimate the
viscosity at the temperature of interest.