Aspen Physical Property System - Physical Property Models

using the values in parameter UNIFPS, instead of the constant value from
GMUFB used above, so that:
Where a, b, and c are the three elements of UNIFPS.
References
Aa. Fredenslund, J. Gmehling and P. Rasmussen, "Vapor-Liquid Equilibria
using UNIFAC," (Amsterdam: Elsevier, 1977).
Aa. Fredenslund, R.L. Jones and J.M. Prausnitz, AIChE J., Vol. 21, (1975), p.
1086.
H.K. Hansen, P. Rasmussen, Aa. Fredenslund, M. Schiller, and J. Gmehling,
"Vapor-Liquid Equilibria by UNIFAC Group Contribution. 5 Revision and
Extension", Ind. Eng. Chem. Res., Vol. 30, (1991), pp. 2352-2355.
UNIFAC (Dortmund Modified)
The UNIFAC modification by Gmehling and coworkers (Weidlich and
Gmehling, 1987; Gmehling et al., 1993), is slightly different in the
combinatorial part. It is otherwise unchanged compared to the original
UNIFAC:
With:
The temperature dependency of the interaction parameters is:
Parameter
Name/Element
UFGRPD (k,� k, m, � m, ...)
174 2 Thermodynamic Property Models
Symbol Default MDS Lower
Limit
Upper
Limit
— — — — —
GMUFDQ Q k — — — — —
GMUFDR R k — — — — —
Units
UNIFDM/1 a mn,1 0 — — — TEMPERATURE
UNIFDM/2 a mn,2 0 — — — TEMPERATURE
UNIFDM/3 a mn,3 0 — — — TEMPERATURE
The parameter UFGRPD stores the group number and the number of
occurrences of each group. UFGRPD is stored in the Aspen Physical Property
System pure component databank. For nondatabank components, enter
UFGRPD on the Properties Molecular Structure Functional Group sheet. See
Physical Property Data, Chapter 3, for a list of the Dortmund modified UNIFAC
functional groups.