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Fixing spurious DoF in Gibbs reactor model #1393

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merged 3 commits into from
Apr 11, 2024
Merged

Fixing spurious DoF in Gibbs reactor model #1393

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01319d7
Catching unneccessary terms in lagrange multiplier expression
Apr 9, 2024
01d2fca
Better implementation
Apr 9, 2024
59dc412
Adding tests for filtering inert elements
Apr 10, 2024
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4 changes: 4 additions & 0 deletions idaes/models/unit_models/gibbs_reactor.py
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Original file line number Diff line number Diff line change
Expand Up @@ -249,6 +249,10 @@ def gibbs_minimization(b, t, p, j):
j
][e]
for e in b.control_volume.config.property_package.element_list
if b.control_volume.properties_out[
t
].config.parameters.element_comp[j][e]
!= 0
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Should we use 0, or a very small value? Does the Pyomo solver writer specifically check for "exactly 0" values and filter those variables out?

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@andrewlee94 andrewlee94 Apr 9, 2024 •
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This is only for exact zero (and a fixed value at that). The issue is that the solver writer is filtering these out for us, but when we use the degrees_of_freedom function we still see these (and hence see spurious DoF).

This is to catch cases where the multiplier is a constant of 0 and filter them out of the expression.

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@andrewlee94 andrewlee94 Apr 9, 2024 •
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I also just worked out a better solution to remove the unneeded multipliers entirely (so that they don't end up as unused variables).

)
)

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