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Fix pressure dependence in IdealSolidSolnPhase::getPartialMolarEnthalpies#1087

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speth merged 3 commits intoCantera:mainfrom
decaluwe:IdealSolid
Sep 16, 2021
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Fix pressure dependence in IdealSolidSolnPhase::getPartialMolarEnthalpies#1087
speth merged 3 commits intoCantera:mainfrom
decaluwe:IdealSolid

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@decaluwe decaluwe commented Aug 19, 2021 •
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Changes proposed in this pull request

  • Adds proper pressure dependence to IdealSolidSolnPhase::getPartialMolarEnthalpies

If applicable, fill in the issue number this pull request is fixing

Closes #1080

If applicable, provide an example illustrating new features this pull request is introducing
Previously, the partial molar enthalpies had no pressure dependence for this class. As a check, the sum of partial molar enthalpy times mole fraction should equal the average phase molar enthalpy. Prior to this change:

import cantera as ct
import numpy as np

gas = ct.Solution('IdealSolidSolnPhaseExample.yaml',"solidSolutionExample")

# At standard pressure: h_mole = sum(X_k*h_k)
h_mole = gas.enthalpy_mole
h_check = np.dot(gas.partial_molar_enthalpies, gas.X)
print(h_mole - h_check)
0

# At non-standard pressure, h_mole shows the correct pressure dependence, but the partial molar enthalpies do not:
gas.TP = None, 3*ct.one_atm
h_mole = gas.enthalpy_mole
h_check = np.dot(gas.partial_molar_enthalpies, gas.X)
print(h_mole, h_check)
303975

With the implemented correction:

import cantera as ct
import numpy as np

gas = ct.Solution('IdealSolidSolnPhaseExample.yaml',"solidSolutionExample")

# At standard pressure: h_mole = sum(X_k*h_k)
h_mole = gas.enthalpy_mole
h_check = np.dot(gas.partial_molar_enthalpies, gas.X)
print(h_mole - h_check)
0

# At non-standard pressure, h_mole shows the correct pressure dependence, but the partial molar enthalpies do not:
gas.TP = None, 3*ct.one_atm
h_mole = gas.enthalpy_mole
h_check = np.dot(gas.partial_molar_enthalpies, gas.X)
print(h_mole, h_check)
0

Checklist

  • The pull request includes a clear description of this code change
  • Commit messages have short titles and reference relevant issues
  • Build passes (scons build & scons test) and unit tests address code coverage
  • Style & formatting of contributed code follows contributing guidelines
  • The pull request is ready for review

@decaluwe decaluwe force-pushed the IdealSolid branch 2 times, most recently from 01b0710 to 6892199 Compare August 19, 2021 12:46
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decaluwe commented Aug 19, 2021

One question: I moved the "multiply by RT" step into the for loop. Would it be faster, computationally, to keep this outside the loop, using scale?

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codecov bot commented Aug 19, 2021 •
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Codecov Report

Merging #1087 (e0f84fa) into main (78f893f) will increase coverage by 0.01%.
The diff coverage is 87.85%.

❗ Current head e0f84fa differs from pull request most recent head f09de99. Consider uploading reports for the commit f09de99 to get more accurate results
Impacted file tree graph

@@            Coverage Diff             @@
##             main    #1087      +/-   ##
==========================================
+ Coverage   73.45%   73.46%   +0.01%     
==========================================
  Files         362      364       +2     
  Lines       47554    47626      +72     
==========================================
+ Hits        34929    34987      +58     
- Misses      12625    12639      +14
Impacted Files Coverage Δ
include/cantera/base/global.h 93.33% <ø> (ø)
include/cantera/kinetics/GasKinetics.h 100.00% <ø> (ø)
include/cantera/kinetics/Kinetics.h 55.88% <0.00%> (ø)
include/cantera/kinetics/MultiRate.h 82.60% <ø> (ø)
include/cantera/kinetics/Reaction.h 100.00% <ø> (ø)
src/clib/ct.cpp 8.29% <0.00%> (-0.06%) ⬇️
src/thermo/IdealSolidSolnPhase.cpp 68.65% <83.33%> (+0.23%) ⬆️
src/kinetics/GasKinetics.cpp 92.61% <85.71%> (-0.43%) ⬇️
src/kinetics/Reaction.cpp 89.20% <85.71%> (-1.24%) ⬇️
src/kinetics/ReactionRateFactory.cpp 93.33% <93.33%> (ø)
... and 18 more

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decaluwe commented Aug 19, 2021

FYI, I'm going to add a test to check that h_mole = sum(h_k * X_k), as in the commit message.

@decaluwe
Test molar enthalpy for IdealSolidSolnPhas
f09de99 
- Test that `enthalpy_mole = sum(X_k * h_k)` for `IdealSolidSolnPhase`
class, where `X_k` is mole fraction and `h_k` partial molar enthalpy.
- Also test the pressure independence of this equality, by verifying at
pressures 1 atm and 2 atm.
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decaluwe commented Aug 19, 2021

Okay, once the tests finish running, this should be ready for review.

@decaluwe decaluwe requested a review from speth August 19, 2021 21:45
speth
speth approved these changes Sep 16, 2021
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Looks good to me.

As to the question about calling scale versus multiplying by RT() inside the loop, I think the latter (as you've opted for) is better, as it involves only one loop -- the scale function would have to loop internally anyway.

@speth speth merged commit 457b1a4 into Cantera:main Sep 16, 2021
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IdealSolidSolnPhase::getPartialMolarEnthalpies - needs pressure dependence?

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@decaluwe @speth