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How to write a udf of htc function in fluent

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Old   July 21, 2021, 05:11
Default How to write a udf of htc function in fluent
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Hi everyone...
I have a function of heat transfer coefficient

htc=(0.0487)+(0.581)V-(0.00646) V^2

where V is the velocity of air, and its value should extract from the solver of fluent first, and then substituted it in the function above to compute the value of htc at different velocities. How could I write this function in UDF to compile it in fluent?
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Old   July 21, 2021, 14:30
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Do you use a no-slip BC at the wall? Hick makes your velocity zero? In that case, HTC is also zero...

Be clear about which V you are exactly talking!
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Old   July 21, 2021, 22:44
Default How to write a udf of htc function in fluent
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Thank you very much for replay...
Yes, I use a no-slip BC at the wall. But the HTC that I want is overall my domain (that is, in every cell in the domain).
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Old   July 22, 2021, 00:17
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Sure, you can calculate a HTC everywhere, but isn't the only place where it is used for anything at a solid-fluid interface?

In my view, you are just requesting a complicated way to get adiabatic conditions...
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Old   July 22, 2021, 00:57
Default How to write a udf of htc function in fluent
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I have a file including a porous medium with heat transfer. And in a second file I test the HTC that must be in the porous medium with different velocities by making a real wall and fluid (without porous medium in second file). Finally, I get the function which I wrote aboveÖ

In the first file, the values of velocities is unknown (it depending on the operating fluid). What did you think should I do? Iím really appreciate your reply... thank you very much.
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Old   July 22, 2021, 01:41
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Quote:
Originally Posted by ymya View Post
And in a second file I test the HTC that must be in the porous medium with different velocities by making a real wall and fluid (without porous medium in second file).
Different velocities where? At the wall? Far away? At the inlet?

Be clear about which V you are exactly talking!
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Old   July 22, 2021, 03:08
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At inlet, in the second file the domain is very simple, just a vertical rectangular, the outlet and inlet at top and bottom respectively, and thermal wall at one side. And then I want to apply the above function at the wall of the first domain. Can I do that
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Old   July 22, 2021, 09:00
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Heat transfer is best described by local properties. Not by velocities at a distance... So I don't understand why you decided to link the heat transfer at the wall to the velocity at the inlet. It's like coupling the HTC to the free disk space on your hard drive. Sure, you could do it, but why? A local property, such as wall shear stress or velocity gradient at the wall, makes much more sense...

Edit: but possibly I completely misunderstand the porous zone. Probably.
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Old   July 22, 2021, 11:50
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thank you pakk... thank you very much for your reply.
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