No heat transfer between solid and fluid regions

lilweasel · October 10, 2016, 00:07

Hello All,

I have a heat generating sample that is in a double walled cylindrical container. The sample is in the inner cylinder with air. The inner cylinder is inside another cylinder with powder between the two. Water flows over the double walled container.
I have added a total heat of 10,000 W to the sample (this is a very exaggerated number to show that there was heat transfer going between my regions). There are interfaces between all the connecting parts with "conjugate heat transfer" applied. The only boundary conditions applied are mass flow inlet and a pressure outlet.
However, when I run the simulation I get temperature results in the air region due to the heat from the sample but there is no heat transfer from the air to the inner cylinder container.
I've searched on these forums, googled, asked my supervisor, but nothing has helped get this to work. Any advice or suggestions is greatly appreciated.
If there is additional information needed please let me know. Attached is a picture of the type of solution I am getting.

Thank you

me3840 · October 13, 2016, 14:52

Is your interface actually working? How many faces does the code put in to it? If you highlight the interface, does it have holes in it or not show up at all?

lilweasel · October 13, 2016, 22:16

Thank you for your response.

When I highlight the interface it does show up and there are not any holes in it that I can see. There was an interface created for each side of the cylindrical space, meaning the top, bottom and cylindrical wall all have separate interfaces.

I assume the interface is working, the reason I say this is because I changed the fluid region to a solid region and ran the simulation again and with that there is a temperature gradient shown across all of the regions.

If I change it back to fluid however, I get the issue again. Is there some extra model or buttonI need to turn on to allow for heat transfer between fluid/solid regions?

kirrer · October 14, 2016, 15:36

It looks like the "air" region is taking the entire gradient, from hot to cold. The contour plot shows blue/green colors near the edges. How long has the simulation run - is it converged? Or is it transient?

If converged, does the air contain any buoyancy (ideal gas or Bousinessq, with gravity simulated)? Is the air laminar or turbulent? I would model the air with gravity + Bousinessq, plus the appropriate turbulence model (check Grashof number, others in the literature, but likely the default K-e model will work).

Finally, give us some clues of the conductivity in materials for inner container, powder, and outer container. Also sizes would be helpful.

Other tip is, have you created a report at the interface which has heat transfer - it's possible to have all 10000W transferred, without a change in the temperature field (at the scale you've shown).

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October 13, 2016, 14:52		#2
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 25	Is your interface actually working? How many faces does the code put in to it? If you highlight the interface, does it have holes in it or not show up at all?

October 13, 2016, 22:16		#3
lilweasel New Member R. Lovelace Join Date: Sep 2016 Posts: 3 Rep Power: 10	Thank you for your response. When I highlight the interface it does show up and there are not any holes in it that I can see. There was an interface created for each side of the cylindrical space, meaning the top, bottom and cylindrical wall all have separate interfaces. I assume the interface is working, the reason I say this is because I changed the fluid region to a solid region and ran the simulation again and with that there is a temperature gradient shown across all of the regions. If I change it back to fluid however, I get the issue again. Is there some extra model or buttonI need to turn on to allow for heat transfer between fluid/solid regions?

October 14, 2016, 15:36		#4
kirrer New Member Kevin Join Date: Oct 2012 Posts: 29 Rep Power: 14	It looks like the "air" region is taking the entire gradient, from hot to cold. The contour plot shows blue/green colors near the edges. How long has the simulation run - is it converged? Or is it transient? If converged, does the air contain any buoyancy (ideal gas or Bousinessq, with gravity simulated)? Is the air laminar or turbulent? I would model the air with gravity + Bousinessq, plus the appropriate turbulence model (check Grashof number, others in the literature, but likely the default K-e model will work). Finally, give us some clues of the conductivity in materials for inner container, powder, and outer container. Also sizes would be helpful. Other tip is, have you created a report at the interface which has heat transfer - it's possible to have all 10000W transferred, without a change in the temperature field (at the scale you've shown).