Conjugate Heat Transfer

saisanthoshm88 · April 23, 2012, 10:08

Iam working on a CHT analysis. I carried out a test run with a pure tet mesh with out any prisms.

Radiation is invoked and Buoyancy settings are applied.

I see that there is a drastic difference in the temperatures on the Fluid side and solid side of the Fluid Solid interface.

The maximum temperature on the Fluid side is around 192 [C] and on the Solid side it is around 980 [C] and this is with reference to the conservative values.

However when the Hybrid values are used , the temperatures on the Fluid side match with those on the solid side.

Could some one please provide an explanation to this

singer1812 · April 23, 2012, 12:39

It is working as it is supposed to.

Hybrid values in cfx enforce display of fluid results to take on boundary condition values. Conservative values are the results from the fluid finite volume at the wall.

You are probably concerned with the extremely high temperature of your solid. Since you are not inflating at the wall you are relying purely on the wall functions for your near wall values. This can have a drastic effect on your results at the wall, and will particularly be noticable in natural convection dominated problems.

Even if the wall functions correctly model your near wall conditions, these temps might not be unrealistic. Did you do a hand calc based on the wall heat flux of your problem, perhaps simplifying it down to vertical and horizontal walls? Might just be too much heat to pull out for the condition you are running.

April 23, 2012, 10:08	Conjugate Heat Transfer	#1
saisanthoshm88 Senior Member --------- Join Date: Oct 2010 Posts: 303 Rep Power: 17	Iam working on a CHT analysis. I carried out a test run with a pure tet mesh with out any prisms. Radiation is invoked and Buoyancy settings are applied. I see that there is a drastic difference in the temperatures on the Fluid side and solid side of the Fluid Solid interface. The maximum temperature on the Fluid side is around 192 [C] and on the Solid side it is around 980 [C] and this is with reference to the conservative values. However when the Hybrid values are used , the temperatures on the Fluid side match with those on the solid side. Could some one please provide an explanation to this __________________ Best regards, Santhosh.

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April 23, 2012, 12:39		#2
singer1812 Senior Member Edmund Singer P.E. Join Date: Aug 2010 Location: Minneapolis, MN Posts: 511 Rep Power: 20	It is working as it is supposed to. Hybrid values in cfx enforce display of fluid results to take on boundary condition values. Conservative values are the results from the fluid finite volume at the wall. You are probably concerned with the extremely high temperature of your solid. Since you are not inflating at the wall you are relying purely on the wall functions for your near wall values. This can have a drastic effect on your results at the wall, and will particularly be noticable in natural convection dominated problems. Even if the wall functions correctly model your near wall conditions, these temps might not be unrealistic. Did you do a hand calc based on the wall heat flux of your problem, perhaps simplifying it down to vertical and horizontal walls? Might just be too much heat to pull out for the condition you are running.