Aspen Physical Property System - Physical Property Models

equations (3, 4). This is the main step to evaluate all the properties needed
for a calculation.
Specific Volume of the Gas Phase
The compressibility factor is defined by the ratio between the number of
complexes and the number of monomers in the complexes.
The compressibility factor itself is
Fugacity Coefficient
66 2 Thermodynamic Property Models
(9)
(10)
As is well-known from thermodynamics, the fugacity coefficient can be
calculated by
Isothermal Enthalpy Departure
(11)
According to the ASPEN enthalpy model, an equation of state must supply an
expression to compute the isothermal molar enthalpy departure between zero
pressure and actual pressure. In the following section this enthalpy
contribution per mole monomers is abbreviated by �ha.
Taking this sort of gas phase non-ideality into account, the specific enthalpy
per mole can be written as
with
(12)
(13)
to evaluate �ha, a mixture consisting of N monomers integrated in the
complexes is considered. The quota of monomers i being integrated in a
complex of degree n is given by