Wall shadows

crinoid · September 25, 2019, 12:29

Hi,
I am studying a convection problem in which I have a heat flux through a wall and, in the other side of the wall, a flow of water cooling it.
Fluent creates a wall-shadow face between the solid and the liquid, so I have: SOLID INTERIOR - WALL - WALL SHADOW (coupled wall) - FLUID INTERIOR.
My question is the following:
Which surface should I use for the heat transfer results (ht coef, wall temperature...): WALL or WALL-SHADOW?

I also used some convection correlations and the WALL results make no sense to me (ht coef = 25 W/m2K instead of 600W/m2K, T=350ºC instead of 50ºC).
In this regard, the WALL-SHADOW face results seem to be ok. Why is there that difference?

LuckyTran · September 26, 2019, 01:22

As you have discovered, Fluent creates a wall and wall-shadow pair on a solid|fluid interface. One wall will belong to the solid domain and the other will belong to the fuid domain. Depending on the order the surfaces are assigned, either the wall or the wall-shadow will belong to one or the other.

It shouldn't matter, but you should select the wall/wall-shadow that is assigned to the fluid domain just to be safe.

Make sure you have specified the correct reference temperature in the reference values pane. It is also a good idea to check the heat flux value to see if it makes sense. If the heat flux makes no sense, then you probably messed up something in your setup. Check your boundary conditions, etc.

crinoid · September 26, 2019, 03:07

Thank you very much for your answer! You were right, I messed up with the boundary conditions... One thermal boundary condition wasn't coupled

September 25, 2019, 12:29	Wall shadows	#1
crinoid New Member crinoid Join Date: Jan 2019 Posts: 22 Rep Power: 7	Hi, I am studying a convection problem in which I have a heat flux through a wall and, in the other side of the wall, a flow of water cooling it. Fluent creates a wall-shadow face between the solid and the liquid, so I have: SOLID INTERIOR - WALL - WALL SHADOW (coupled wall) - FLUID INTERIOR. My question is the following: Which surface should I use for the heat transfer results (ht coef, wall temperature...): WALL or WALL-SHADOW? I also used some convection correlations and the WALL results make no sense to me (ht coef = 25 W/m2K instead of 600W/m2K, T=350ºC instead of 50ºC). In this regard, the WALL-SHADOW face results seem to be ok. Why is there that difference?

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September 26, 2019, 01:22		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,761 Rep Power: 66	As you have discovered, Fluent creates a wall and wall-shadow pair on a solid\|fluid interface. One wall will belong to the solid domain and the other will belong to the fuid domain. Depending on the order the surfaces are assigned, either the wall or the wall-shadow will belong to one or the other. It shouldn't matter, but you should select the wall/wall-shadow that is assigned to the fluid domain just to be safe. Make sure you have specified the correct reference temperature in the reference values pane. It is also a good idea to check the heat flux value to see if it makes sense. If the heat flux makes no sense, then you probably messed up something in your setup. Check your boundary conditions, etc.

September 26, 2019, 03:07		#3
crinoid New Member crinoid Join Date: Jan 2019 Posts: 22 Rep Power: 7	Thank you very much for your answer! You were right, I messed up with the boundary conditions... One thermal boundary condition wasn't coupled