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Difference OF7 to OF8 - hconst to econst

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Old   December 8, 2020, 12:46
Default Difference OF7 to OF8 - hconst to econst
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I recently tried to switch from OF7 to OF8. When I tried to run my chtMultiRegionFoam case I got the error messages of "Unknown solidThermo Type", so I had to change in thermophysicalProperties from "hConst" to "eConst", from "sensibleEnthalpy" to "sensibleInternalEnergy" and in fvSolution as well from h to e.

With this changes the case ran.

Checking here: https://cfd.direct/openfoam/user-gui...hermophysical/
the Thermodynamic models gives this explanation:

hConst
assumes a constant cp and a heat of fusion Hf which is simply specified by a two values cp Hf, given by keywords Cp and Hf.

eConst
assumes a constant cv and a heat of fusion Hf which is simply specified by a two values cv Hf, given by keywords Cv and Hf.

Running the case for 1000 seconds, gives me a tiny difference in results, but there is a difference. I know that OF6 and OF7 did not produce the same results either, but since I had to change from "hconst" to "econst", I would like to know, if there is any physical difference between cp and cv.
So is the difference in results just "normal", as I changed from OF7 to OF8, or is it a difference produced by different physical setting?
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Old   December 8, 2020, 13:11
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Domenico Lahaye
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Heat capacity of solid at constant volume (cv) or constant pressure (cp) can (and typically are) different. Tabular data will typically list both.
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Old   December 9, 2020, 03:40
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Thank you for your help!
Since liquids and solids can practically assumed to be incompressible, Cp and Cv for them have almost same values at least at moderate temperatures?
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Old   January 21, 2021, 07:32
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I noticed the same. Cp and Cv are practically the same for solid, so I guess the developers thought that for a solid it makes more sense eConst.

For the change of sensibleInternalEnergy, it seems to be for numerical reasons

https://github.com/OpenFOAM/OpenFOAM...25ab9817b3ec62

source: When choose sensibleInternalEnergy or sensibleEnthalpy in thermophysicalProperties
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Old   February 4, 2021, 09:17
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I noticed the same problem. I am solving a heat transfer model with two solids of different diffusivities and I get differences. I am still investigating where the trick is.
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