Thermal Simulation help - setup loads

[corsair2014]

So I am working with thermal situations for the first time, and am having some trouble with setup. An example screenshot is posted below.

This is a rubber grommet (rubber, black - material) and I applied 1 load, a 300F contact thermal load on the bottom of the grommet. So what exactly happens now? When I run the simulation the whole grommet becomes 300F. In another example I am using these grommets to isolate a circuit board but the entire design becomes 300F. In a tutorial video I saw that you might need to apply a 'convection' load to where heat will escape from the design? So that helps set the ambient temperature.

I guess I have two main questions:

1. How do I setup a thermal simulation to see if this rubber grommet could help isolate something, say, a circuit board from a piece of aluminum?
2. If I need to apply 'convection' loads to allow heat to escape in the simulation, how do I know what the convection rate is for various materials? Example: 6061-T6 aluminum

[John_Holtz · Accepted solution]

Hi @corsair2014 . Welcome to thermal analysis in Fusion.

You are correct that a heat transfer analysis needs a source of heat and a way to remove the heat. Otherwise, the temperature is uniform.

In your case, you should be modeling the circuit board, grommet, and plate. What you are trying to calculate is how the heat conducts through the various pieces.

The convection coefficient can be calculated by using an engineering textbook that covers the subject of heat transfer. For example, J.P. Holman's book "Heat Transfer" has 3 chapters on convection. (At least my 5th Edition, 1981 book has 3 chapters. The current version may be different.) The value of the convection coefficient depends on the fluid surrounding the model (air), whether it is blowing or stationary (force or natural convection), the orientation (horizontal, vertical), temperature of the fluid, and so on.

If you just want a comparison of how one size grommet behaves compared to another, then your approach may be acceptable. Depending on the full details of the physical parts, the analysis may need to be more complex if you need to calculate accurate values. 300 F is rather hot, so other factors may be important depending on what you are trying to calculate. Is the model inside an enclosure? Does the heat cause the air to move because warm air is buoyant? Is radiation between parts important? Some of these factors may require an analysis with more capable software such as Autodesk CFD.