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-   -   Local heat transfer coefficient around a cylinder (http://www.cfd-online.com/Forums/fluent/96165-local-heat-transfer-coefficient-around-cylinder.html)

dal_fry January 14, 2012 11:29

Local heat transfer coefficient around a cylinder
 
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!

mali28 January 20, 2012 13:23

You have to use static temperature in your calculation not the total temperature.


Quote:

Originally Posted by dal_fry (Post 339313)
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!


elham-u March 29, 2013 14:35

Quote:

Originally Posted by dal_fry (Post 339313)
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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