Aspen Physical Property System - Physical Property Models

The reference enthalpy is calculated at T ref as:
Where:
Hi *,ig
Hi *,v - Hi *,ig
= Ideal gas enthalpy
236 2 Thermodynamic Property Models
= Vapor enthalpy departure from equation of state
�vapHi *,l = Heat of vaporization from General model
T ref
= Reference temperature, specified by user. Defaults to
298.15 K
See General Pure Component Heat of Vaporization for parameter requirement
and additional details.
Enthalpies Based on Different Reference
States
Two property methods, WILS-LR and WILS-GLR, are available to calculate
enthalpies based on different reference states. The WILS-LR property method
is based on saturated liquid reference state for all components. The WILS-GLR
property method allows both ideal gas and saturated liquid reference states
for different components.
These property methods use an enthalpy method that optimizes the accuracy
tradeoff between liquid heat capacity, heat of vaporization, and vapor heat
capacity at actual process conditions. This highly recommended method
eliminates many of the problems associated with accurate thermal properties
for both phases, especially the liquid phase.
The liquid enthalpy of mixture is calculated by the following equation (see the
table labeled Liquid Enthalpy Methods):
Where:
Hm ig
Hi *,ig
= Enthalpy of ideal gas mixture
=
= Ideal gas enthalpy of pure component i
(Hm l -Hm ig ) = Enthalpy departure of mixture
For supercritical components, declared as Henry's components, the enthalpy
departure is calculated as follows: