Aspen Physical Property System - Physical Property Models

Parameter Name Symbol No. of Elements Default Units
Ionic Unary Parameters
GMBPB1 � (1) 5 0 —
Working Equations
The complete Pitzer equation (Fürst and Renon, 1982) for the excess Gibbs
energy is (see also equation 4):
Where:
G E
88 2 Thermodynamic Property Models
= Excess Gibbs energy
R = Gas constant
T = Temperature
nw = Kilograms of water
zi = Charge number of ion i
Where:
= molality of ion i
xi = Mole fraction of ion i
xw = Mole fraction of water
Mw = Molecular weight of water (g/mol)
ni = Moles of ion i
B, C, � and � are interaction parameters, and f(I) is an electrostatic term as
a function of ionic strength; these terms are discussed in Pitzer Activity
Coefficient Model, which has a detailed discussion of the Pitzer model.
The C term and the � term are dropped from equation 1 to give the
simplified Pitzer equation.
Where:
Bij = f(�ij (0) ,�ij (1) ,�ij (2) ,�ij (3) )
(2)
(1)