MEA PHE tests failing with Pyomo 6.7.0

[lbianchi-lbl]

Observed on:

• Windows (GHA)
• Linux (by @andrewlee94 on his local machine)

FAILED idaes/models_extra/column_models/tests/test_plate_heat_exchanger.py::TestPHE::test_solve - AssertionError
FAILED idaes/models_extra/column_models/tests/test_plate_heat_exchanger.py::TestPHE::test_solution - AssertionError
FAILED idaes/models_extra/column_models/tests/test_plate_heat_exchanger.py::TestPHE::test_conservation - AssertionError

[andrewlee94]

Initial symptoms suggest a scaling issue (platform dependent failures). Further investigations (using a local Linux build that fails) showed:

• The associated change in Pyomo should only change variable ordering, which is observed.
• However, inspecting the NL file also showed that the solution from the model initialization was significantly different, indicating that the source of the problem occurs during initialization.

[dallan-keylogic]

Unable to reproduce problem on my machine. @jsiirola suggested checking whether Pyomo presolve to remove trivial equality constraints might make this problem go away on its own.

[lbianchi-lbl]

No progress on this as of today.

[dallan-keylogic]

Need to try running this after the new Pyomo release when the presolve is added. Note that we might need to manually enable the presolve initially.