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Local heat transfer coefficient around a cylinder

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Old   January 14, 2012, 12:29
Question Local heat transfer coefficient around a cylinder
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Benjamin
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Hello,

I'm trying to get the local Nusselt number around one cylinder in an external air flow.
(http://siam51.free.fr/air_flow.bmp)

The mesh is fine enough to have y+~1 near the wall.

I got the total temperature near the wall, the heat flux near the wall (W/mē) and the total heat flux exchanged (W)

To calculate the local heat transfer coefficient, I tried two methods :

h1 = [ heat flux near the wall (W/mē) ] / (383-263)
h2 = [ total heat flux exchanged (W) ] / (383-total temperature near the wall)

Values are completely different!
h1~50-450
h2~250-600

I wonder what would be the best formula to use?

Thanks in advance!
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Old   January 20, 2012, 14:23
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You have to use static temperature in your calculation not the total temperature.


Quote:
Originally Posted by dal_fry View Post
Hello,

I'm trying to get the local Nusselt number around one cylinder in an external air flow.
(http://siam51.free.fr/air_flow.bmp)

The mesh is fine enough to have y+~1 near the wall.

I got the total temperature near the wall, the heat flux near the wall (W/mē) and the total heat flux exchanged (W)

To calculate the local heat transfer coefficient, I tried two methods :

h1 = [ heat flux near the wall (W/mē) ] / (383-263)
h2 = [ total heat flux exchanged (W) ] / (383-total temperature near the wall)

Values are completely different!
h1~50-450
h2~250-600

I wonder what would be the best formula to use?

Thanks in advance!
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Old   March 29, 2013, 14:35
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Quote:
Originally Posted by dal_fry View Post
Hello,

I'm trying to get the local Nusselt number around one cylinder in an external air flow.
(http://siam51.free.fr/air_flow.bmp)

The mesh is fine enough to have y+~1 near the wall.

I got the total temperature near the wall, the heat flux near the wall (W/mē) and the total heat flux exchanged (W)

To calculate the local heat transfer coefficient, I tried two methods :

h1 = [ heat flux near the wall (W/mē) ] / (383-263)
h2 = [ total heat flux exchanged (W) ] / (383-total temperature near the wall)

Values are completely different!
h1~50-450
h2~250-600

I wonder what would be the best formula to use?

Thanks in advance!
hi
i have the same problem!
but i have a problem in calculating the local heat transfer around the cylinder!
should i choose some points by surface-point-coordinate?i think cartesian coordinate isn't accurate! plz help me!
thanks in advance!
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