#1957 return heat source in isothermal models

[rtimms]

Description

Fixes a bug where the isothermal submodel doesn't calculate any heat source terms. There is a new option "calculate heat source for isothermal models" that is "false" by default and "true" otherwise. Default is "false" since this option may require additional parameters not needed by the electrochemical model (specifically current collector parameters).

Fixes #1957

Type of change

Please add a line in the relevant section of CHANGELOG.md to document the change (include PR #) - note reverse order of PR #s. If necessary, also add to the list of breaking changes.

• New feature (non-breaking change which adds functionality)
• Optimization (back-end change that speeds up the code)
• Bug fix (non-breaking change which fixes an issue)

Key checklist:

• No style issues: $ flake8
• All tests pass: $ python run-tests.py --unit
• The documentation builds: $ cd docs and then $ make clean; make html

You can run all three at once, using $ python run-tests.py --quick.

Further checks:

• Code is commented, particularly in hard-to-understand areas
• Tests added that prove fix is effective or that feature works

[codecov]

Codecov Report

Merging #1958 (9a1f455) into develop (fb76610) will increase coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 9a1f455 differs from pull request most recent head 2de921e. Consider uploading reports for the commit 2de921e to get more accurate results

@@           Coverage Diff            @@
##           develop    #1958   +/-   ##
========================================
  Coverage    99.32%   99.32%           
========================================
  Files          346      346           
  Lines        19058    19064    +6     
========================================
+ Hits         18930    18936    +6     
  Misses         128      128           

Impacted Files	Coverage Δ
...m/models/full_battery_models/base_battery_model.py	99.76% <ø> (ø)
pybamm/models/submodels/thermal/isothermal.py	100.00% <100.00%> (ø)

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[brosaplanella]

Looks good! I didn't review the last PR, so is there any tests that checks that the heat source terms are calculated correctly?

[rtimms]

Do you mean to test if the variables have the correct expression (i.e. zero or not)? Or some numerical check on the actual values?

[brosaplanella]

Do you mean to test if the variables have the correct expression (i.e. zero or not)? Or some numerical check on the actual values?

I guess both, though just realised I don't know if we are testing this for the other variables anyway haha

[rtimms]

I guess both, though just realised I don't know if we are testing this for the other variables anyway haha

We compare outputs across different models that should be the same and have some tests on variables for things like conservation or checking that things that should be increasing are increasing etc., but we don't test for correct values.

I'll merge this for now, but maybe we can revisit if there are any useful extra tests on variables.