For users of ChemApp versions prior to 3.2.0: The values returned by TQSTXP (Get – Thermodynamic – Property – Of – A – Stream) always refer to the last calculated equilibrium state. If TQSTXP is called before the first equilibrium calculation has been performed using TQCE (Calculate – Equilibrium) or TQMAP (Calculate – One – Dimensional – Phase – Map), the value returned will be zero.
As of ChemApp version 3.2.0, TQSTXP can be called to get the calculated thermodynamic properties of a stream also before an equilibrium calculation has been performed.
If you are wondering about what exactly ChemApp takes into account when calculating extensive properties of streams, please refer to the section Advanced topics in the appendix of the Programmer’s Manual (Edition 3.2 and later) (-> ChemApp documentation light/regular).