Aspen Physical Property System - Physical Property Models

These mixing rules are discussed separately in the following sections. They
have major advantages over other composition-dependent equation-of-state
mixing rules.
References
M.- J. Huron and J. Vidal, "New Mixing Rules in Simple Equations of State for
representing Vapour-liquid equilibria of strongly non-ideal mixtures," Fluid
Phase Eq., Vol. 3, (1979), pp. 255-271.
MHV2 Mixing Rules
Dahl and Michelsen (1990) use a thermodynamic relationship between excess
Gibbs energy and the fugacity computed by equations of state. This
relationship is equivalent to the one used by Huron and Vidal:
The advantage is that the expressions for mixture and pure component
fugacities do not contain the pressure. They are functions of compacity V/b
and �:
Where:
and
With:
The constants �1 and �2, which depend only on the equation-of-state (see
Huron-Vidal Mixing Rules) occur in equations 2 and 4.
Instead of using infinite pressure for simplification of equation 1, the condition
of zero pressure is used. At p = 0 an exact relationship between the
compacity and � can be derived. By substitution the simplified equation q(�)
is obtained, and equation 1 becomes:
2 Thermodynamic Property Models 81
(1)
(2)
(3)
(4)
(5)
(6)