When evaluating warnings for a fluid mixture, extrapolation warnings may indicate that temperatures or pressures are outside the valid range and appear much lower than the values reported on the associated component or node. Why can the warning values differ from the final reported results, and do these warnings use partial pressures or values from earlier solution iterations before convergence?
Several factors may contribute to this behavior. Flownex does use partial pressures in its calculations; for example, if the mass fraction of a species is zero, the corresponding partial pressure would also be zero. However, this condition should not normally generate an extrapolation warning.
Warnings are generally issued only during the final iteration of the solution process, so they are not expected to originate from earlier unconverged iterations. Another possibility is that certain calculations, such as choking calculations, may temporarily evaluate fluid properties at pressures or temperatures that differ from the final values displayed on the component. These intermediate calculation values can sometimes be lower than the reported operating conditions. Such cases should typically not trigger extrapolation warnings, and if they do, further investigation may be required to determine whether the behavior is expected or whether it should be addressed.