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Re: Modeling thermal path through screw
The heat transfer is a function of a lot of things, especially the torque. Bolt heat transfer values are usually empirical--modeling dos not necessarily give accurate results.
The way I do it is with this spreadsheet. It is based on a document developed in the sixties by Norden aircraft company. If you enter the information in green, you get the information in blue. This includes the apparent diameter and the K*m^2/W. I model the apparent diameter with split lines and apply the k*m^2/W as a contact resistance. This is very computationally efficient, because you can just suppress all of the screws. In my experience this method is accurate.
This spreadsheet also gives you a back of the envelope estimate of how many screws you might need to get the heat out.
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Re: Modeling thermal path through screw
nice.
addision, from a solidwork simulation perspective, the method that you're using is a good approximation. you could model the threads and then use a cavity but i think that would be overkill.
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Re: Modeling thermal path through screw
Thanks.
I had a feeling that might be the case. I will proceed with my original path then.
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Re: Modeling thermal path through screw
Hello, I have the same problem, could you please tell me the document you are referencing at?
Thank you,
Dario
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Re: Modeling thermal path through screw
It is attached to my post. It produces a thermal resistance value that you can apply between the bolt holes.
Create a split face around each bolt hole at the apparent diameter listed in the spreadsheet. The apply the thermal resistance between the split faces of connected holes. Do not model the actual bolt or washer at all.
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Re: Modeling thermal path through screw
Dear Mike, yes I have already downloaded your spreadsheet and it seems to be really well done. I was asking for the Norden document, just to understand the meaning of some terms.
If I understand right ,you suggest to create two split circles in the region of the 2 parts which are interested by the contact, and the diameter of this 2 split surfaces should be the apparent diameter right? Actually I'm already doing something like this, even if I do not compute exactly the apparent diameter.
But my question is: what about the thermal path which goes from the bottom surface of the screw head, trough its shank, to the threaded swurface of the connected part?
This is accounted in some way?
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Re: Modeling thermal path through screw
Oh nos. I lost my Norden pdf. I'll see if I can find it at home or if an old colleague can send it to me.
To answer your question here, the thermal conductance curve is measured empirically, and the equation you see is just a curve-fit. So conduction through all paths is rolled into the result you see.
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