Aspen Physical Property System - Physical Property Models

Parameter Name/
Element
2 Thermodynamic Property Models 25
Symbol Default MDS Lower
Limit
Upper
Limit
Units
TC T ci — — 5.0 2000.0 TEMPERATURE
PC p ci — — 10 5
RGYR r i gyr
— — 10 -11
10 8
5x10 -9
MUP p i — — 0.0 5x10 -24
HOCETA �� 0.0 X — — —
PRESSURE
LENGTH
DIPOLEMOMENT
The binary parameters HOCETA for many component pairs are available in the
Aspen Physical Property System. These parameters are retrieved
automatically when you specify any of the following property methods: NRTL-
HOC, UNIF-HOC, UNIQ-HOC, VANL-HOC, and WILS-HOC.
References
J.G. Hayden and J.P. O'Connell, "A Generalized Method for Predicting Second
Virial Coefficients," Ind. Eng. Chem., Process Des. Dev., Vol. 14,No. 3,
(1975), pp. 209 – 216.
HF Equation-of-State
HF forms oligomers in the vapor phase. The non-ideality in the vapor phase is
found in important deviations from ideality in all thermodynamic properties.
The HF equation accounts for the vapor phase nonidealities. The model is
based on chemical theory and assumes the formation of hexamers.
Species like HF that associate linearly behave as single species. For example,
they have a vapor pressure curve, like pure components. The component on
which a hypothetical unreacted system is based is often called the apparent
(or parent) component. Apparent components react to the true species.
Electrolyte Calculation in Physical Property Methods discusses apparent and
true species. Abbott and van Ness (1992) provide details and basic
thermodynamics of reactive systems.
The temperature-dependent hexamerization equilibrium constant, can fit the
experimentally determined association factors. The built-in functionality is:
The constants C0 and C1 are from Long et al. (1943), and C2 and C3 are set to
0. The correlation is valid between 270 and 330 K, and can be extrapolated to
about 370 K (cf. sec. 4). Different sets of constants can be determined by
experimental data regression.
Molar Volume Calculation
The non-ideality of HF is often expressed using the association factor, f,
indicating the ratio of apparent number of species to the real number or
species. Assuming the ideal gas law for all true species in terms of (p, V, T)
behavior implies:
(1)