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COMSOL startup help

COMSOL startup help

COMSOL startup help

Hello, this might be a long shot but here we go. I am looking for someone to assist me with some questions about the FEM software COMSOL. Specifically i am creating a single phase cable model which should be able to anticipate temperature rise at diffrent amps through the cable.

I've build the model and figured out some of the basics, but i cannot seem to get the model to show a connection between current density and temperature rise.

I wonna start by doing a 3D stationary model. A solid 2meter cylinder acting as a cable. But i'am not sure how to get comsol to know that i want to have current flowing throgh it.
I have grounded one end of the wire, and put a Normal current density through the other.

My results shows a voltage as a resuslt of the predefined current/resistance which is great.

But the temperature is wierd. The core fo the cable is shows a color which should be a higher temperature than the color of the cable skin.
But the temperature max min is the same.

Can somebody say something about my simple model from the attached screenshots maybe?.

Thanks in advance!
Best regards Jens.

RE: COMSOL startup help

Make sure that the mesh is sufficiently dense. Check the material properties and other values carefully, there might be a mistake somewhere. Add convection if you haven’t already. Some thermal boundary conditions at the ends (other than insulation) might be necessary.

Is it a strady-state analysis ?

Analytical solution of this simple Joule heating problem might be helpful here.

RE: COMSOL startup help

Hi, thanks you for the answer.

The analysis/study is steady state yes.
I've added a Heat flux boundary to air with 5 W/m2 to all boundaries except input and output end. A screenshot of this is attached.
I have no thermal conditions at the end of the cable yet. I would think that would require me to know which type of material the terminal connection will be made of?. or is there a general cable shoe W/m2 value?

I will double check the values now, but i suspect some silly mistake to be the culprit which makes my temperature value even everywhere, even tho i can se the color variations.

RE: COMSOL startup help

Try running a time dependent study and add a convection boundary condition to both ends of the bar as well. Make sure that the value of electrical conductivity is correct, a lot depends on it here.

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