3.20: Changing the status of phases and constituents

ChemApp contains subroutines that enable the status of phases or constituents to be changed; that is, to be either excluded from or re-entered into an equilibrium calculation (see Table 10). The default status is that stored in the thermodynamic data-file. The status for a phase can be changed implicitly, dependent on the explicit changes of the statuses of its constituents. For example, if all constituents of a phase are made dormant, the phase will also be dormant.

Whereas complete phases can always be set ENTERED, DORMANT or ELIMINATED, some restrictions apply for phase constituents (see the notes for TQCSPC).

A common reason for changing the status of a phase is for instance the desire to calculate a metastable equilibrium (see TQGSP) or to increase the computational speed in systems containing miscibility gaps (see Appendix E.2).

Table 10: ChemApp subroutines for changing the status of phases and constituents

Subroutine Function
TQGSP Gets the status of a phase
TQCSP Changes the status of a phase
TQGSPC Gets the status of a phase constituent
TQCSPC Changes the status of a phase constituent

Table 11: Possible statuses for phases and constituents

Option Comment
ENTERED The phase or constituent is included in the equilibrium calculation. An included phase is not necessarily stable at equilibrium.
DORMANT The phase or constituent is excluded from the mass balances (it will appear with zero amount at equilibrium), but its activity is calculated. If the calculated activity for a phase is greater than one, it would be stable if entered.
ELIMINATED The phase or constituent is ignored in the equilibrium calculation


ChemApp Programmer's Manual, Edition 3.6© GTT-Technologies, 2003