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Thermal diffusion coefficient empirical formula

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Old   May 14, 2018, 08:38
Default Thermal diffusion coefficient empirical formula
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Chris
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Hello,

The empirical formula for the thermal diffusion coefficient provided by Fluent when using the kinetic theory option for thermal diffusivity is supposedly derived from "Principles of Combustion" by K. K. Kuo (1986). I am sitting with the book in front of me and I cannot find anything that resembles this formula. Kuo mentions under the multicomponent diffusion equation that thermal diffusion was not considered. The link to the thermal diffusion coefficients page in the Fluent 17.2 manual is below:

https://www.sharcnet.ca/Software/Ans...diffusion.html

Is there somebody who can explain for me how they have arrived at the formula on this page? Thank you.
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Old   May 14, 2018, 15:15
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I don't have the book in front of me.

But if they mentioned that thermal diffusion was not considered, then you shouldn't expect to find the equation that would describe it. Look for the section that does have thermal diffusion (or Soret effects).

Also I think you have misunderstood something. The thermal diffusion coefficient (or thermodiffusion coefficient) is the mass diffusion coefficient which is attributable to thermal diffusion (diffusion of species concentration due to temperature gradients), hence it has the symbol D. This is not the thermal diffusivity (which is the heat diffusion due to temperature gradients), which normally has the greek symbol alpha.
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Old   May 14, 2018, 17:30
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It's strange that Fluent refers to Kuo if the formula is not there. That is if they haven't done some major derivation based on something in the book, or I just can't seem to find it. Would be nice with a page number for what they've used.
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Old   May 15, 2018, 11:40
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Anyone who has any thoughts on this? That'd be deeply appreciated.
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Old   May 16, 2018, 11:32
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A reference to the formula in litterature is all I need, anyone? Thanks
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Old   May 17, 2018, 08:34
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bump, please help
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Old   September 11, 2018, 18:49
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I think this is the wrong reference. I found the formula in the book
"Applications of Turbulent and Multiphase Combustion" (page 248) also by Kuo.

Have you found other references?
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