# FLUENT: Pure Conduction???

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February 24, 2015, 09:13
FLUENT: Pure Conduction???
#1
Member

Anh
Join Date: Sep 2014
Posts: 69
Rep Power: 7
I am doing the pure conduction by Fluent. The calculation domain is as in the picture below. It include: core region (UO2) which is covered by Tank. All material are air.
The border wall outside is convective boundary condition.
The material of core is UO2, and the condition for this core is Heat generation Rate 8000w/m3.
The wall of Tank is Al.

So in Fluent, I specify the the Heat Generation Rate for the core region in the tap: Cell Zone Condition - Source tap. For the wall boundary of the core and Tank, It is the coupled wall condition.
The solve is only Energy equation (No flow).

But the solution give the temperature of core reach to maximum limit of temperature: 10000K. This results is inaccurate, analysis results is about 3000K.
I think the error may be caused by wrong boundary condition.

Attached Images
 Untitled.jpg (20.8 KB, 17 views)

 February 25, 2015, 17:56 #2 Senior Member   Lucky Tran Join Date: Apr 2011 Location: Orlando, FL USA Posts: 3,970 Rep Power: 47 What's your viscous model? Is it inviscid? I've had problems simulating pure conduction with inviscid model, have to select laminar or turbulent.

 February 26, 2015, 16:34 #3 Senior Member   JSM Join Date: Mar 2009 Location: India Posts: 168 Rep Power: 16 Hi, If you defined the source term for volume, then no need to specify the source in walls also. By defining like this, you are applying double the time of source in your simulation. Remove the source in the walls and rerun it. It might be the one of the reason for more temperature in the domain. __________________ With regards, JSM

February 27, 2015, 06:01
#4
Member

Anh
Join Date: Sep 2014
Posts: 69
Rep Power: 7
Quote:
 Originally Posted by LuckyTran What's your viscous model? Is it inviscid? I've had problems simulating pure conduction with inviscid model, have to select laminar or turbulent.
Thank you, LuckyTran.

February 27, 2015, 06:05
#5
Member

Anh
Join Date: Sep 2014
Posts: 69
Rep Power: 7
Quote:
 Originally Posted by jsm Hi, If you defined the source term for volume, then no need to specify the source in walls also. By defining like this, you are applying double the time of source in your simulation. Remove the source in the walls and rerun it. It might be the one of the reason for more temperature in the domain.
Thank you, jsm.
Actually, I did not specify the source in walls. The boundary for the wall is coupled wall (which are used when that wall is between two different material).
Fluent have one tutorial similar (heat generation on the chip), but the different is that have flow instead of pure conduction. My case is pure conduction. So It may be the problems?

 February 28, 2015, 10:11 #6 Senior Member   JSM Join Date: Mar 2009 Location: India Posts: 168 Rep Power: 16 Then, I don't know the reason for high temperature. If solution is converged and there is no issues in case setup, there might be other reasons. 1. Double check the volume of zone in Fluent and input source value (8000 W/m3) 2. Check the modeling 3. Incorrect energy value in Watts __________________ With regards, JSM

March 1, 2015, 05:01
#7
Member

Anh
Join Date: Sep 2014
Posts: 69
Rep Power: 7
Quote:
 Originally Posted by jsm Then, I don't know the reason for high temperature. If solution is converged and there is no issues in case setup, there might be other reasons. 1. Double check the volume of zone in Fluent and input source value (8000 W/m3) 2. Check the modeling 3. Incorrect energy value in Watts
I checked all comments of you. It is Ok. I dont what probelm is.
I upload the full domain of my calculation as in the picture below. Maybe you can understand my situation better.
Attached Images
 heat-job-1.4-flow.jpg (37.8 KB, 10 views)

 March 2, 2015, 13:32 #8 Senior Member   JSM Join Date: Mar 2009 Location: India Posts: 168 Rep Power: 16 What is "Heat source 44 m3". Even if is heat source volume then, 44 m3 is huge. Is your domain really than much big in size. Also check the properties of solids. other than this, I don't know the reason for high temperature. __________________ With regards, JSM