"Infinite loop" for distillation column with HX between feed & bottoms
Simulate chemical processes using advanced thermodynamic models
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#146 "Infinite loop" for distillation column with HX between feed & bottoms
Creating a simple distillation column (Peng-Robinson, Water/Propylene Glycol/Isopropanol) with a fully specified feed stream and a heat exchanger between this feed & the distillation column's bottom output results in an "Infinite loop" error, suggesting recycle blocks. However this still solvable iteratively (as proprietary sim packages confirms), if the column takes a guess feed temperature & updates the bottoms temperature afterwards.
Tested on 64bit Windows 7.
This is by design. Current flowsheet solver code is designed to stop solving when an object is about to be added to the list for the second time, according to the process flow.
So how then should this process be drawn & solved with DWSIM?
The column won't converge because its feed stream (which comes from the heat exchanger) isn't calculated, and the feed stream won't calculate because the heat exchanger isn't solved, and the heat exchanger won't calculate because the bottoms stream from the column isn't calculated, and that won't calculate because the column isn't solve.
Or equivalently, as a hack, how can I "suggest" to the column what its feed temperature will be after the flowsheet has converged, even though DWSIM won't let me constrain it from the flowsheet?