Learning Forum

[FeRo220]

Hello,

I have a basic system of two cylinders acting as heat sources (set to 320C) that sit on three layers of objects each, which in turn are both sitting in a box. So from top to bottom, it is the cylinder, top spacer, a block, bottom spacer, then the box floor.

The issue I am having is that whenever I set the temperature of the cylinder, the solution isn't showing any heat flow to the box. It only shows the cylinders, spacers, and blocks as the prescribed temperature of the cylinder (320), then the pocket is at ambient temperature. Below shows an image what I am referring to:

[peteroznewman]

Please show your model tree. Is this done in Steady State Thermal?
What are the other boundary conditions? Are you using Convection on any of the surfaces in contact with air?
Use File Archive and save a .wbpz file and attach that to your reply along with the version of Ansys you are using.

[FeRo220]

Thank you for replying and offering your help, I greatly appreciate it.
Here is a photo of the tree:

Yes, it is done in Steady State Thermal - Mechanical Enterprise.
For Boundary Conditions, I have the Temperature of the Cylinders to be 320C, I have radiation going to the cubes and the box as well, both with emissivity of 0.80, with surface-to-surface correlation, and ambient temperature of -271.
No, I don't account for Convection because this problem is supposed to be in space, so no natural convection. I was reading that an option is to set convection on the outer surface with a very low heat transfer coefficient, but didn't know if this was the best way to proceed.
I'm using ANSYS 2021 R1, and attached is a copy, as requested.

[peteroznewman]

The Pocket is not Solid, it is just surfaces.
Use the Missing Faces button on the Repair tab in SpaceClaim to Solidify the Box, then use the Share button on the Workbench tab.


In Mechanical, suppress all the Contacts and the model will solve.

[FeRo220]

I forgot to mention, the file I provided is simpler than the one in question, mainly it doesn't have the top and bottom spacers, just the cylinders, cubes, and boxes. The same error is on both, so I figured they share the same errors

[FeRo220]

Thank you for your help.
I followed your instructions (i.e. solidifying the box) and was able to get results that make sense.
However, whenever I tried to suppress the connections, I got the same, incorrect results.
When I left them un-suppressed, the results appeared.
Do you happen to know why this is?
I trust you know more about the program than I do, but don't we want contacts to tell ANSYS that these pieces are touching each other?
I have the results either way, but just curious.
I appreciate your time regardless.

[peteroznewman]

If you used the Share button and the surfaces that are supposed to be touching light up, then you don't need contacts.
If you don't use the Share button, then you do need contacts and the default is to assign zero thermal resistance.
If there is zero thermal resistance at the interface of two materials, then using the Share button gives you that effect.
If you want to insert a nonzero thermal resistance at the interface, you can do that on a bonded contact in the details panel.

[FeRo220]

Great, that makes sense. For my purposes I'm okay with zero thermal resistance so I'll keep the contacts as is