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Heat source simulation

Posted 16.01.2019, 11:37 MEZ Heat Transfer & Phase Change, Results & Visualization Version 4.4 2 Replies

Nadav Pevzner
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Hi, I'm a complete comsol newbie. I'm trying to run a simulation that seems to be quite simple yet somehow I keep getting errors upon computing (usually the error is "The Relative Residual (x) Is Greater Than The Relative Tolerance"). Basically I'm trying to get the temp on a simplified transformer model (which I'v imported from an .stp file if it matters), which consists of a ferrite core, copper windings and a surrounding block of air I've added, and calculate it based on known losses. I created a steady-state project with the heat transfer in solids physic. Each relevant component was assigned as a heat source with a total power of the given losses. I left all other settings as default. I also assigned each component with its material and added missing properties as instructed by the software. Your assistance would be highly appreciated as I keep feeling as if I'm missing some basic consepts, given the fact that I'm failing to do some things that seem quite trivial. I'm attaching my model here.

Thank you

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2 Replies Last Post 16.01.2019, 14:29 MEZ
Jeff Hiller COMSOL Employee

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Posted: 5 years ago 16.01.2019, 14:22 MEZ

Hello Nadav,

The fundamental problem here is that you have heat sources and nowhere for the heat to leave: all your outside boundaries are insulated. So no stationary solution exists.

I also noticed that you have set up your model in such a way that any convection heat transfer in the air is neglected (because you're solving the heat transfer in solids equation in the air domain). Maybe you made that simplification knowingly, but I wanted to point it out in case that was not your intention.

The Introduction to COMSOL Multiphysics manual includes a tutorial that shows how to set up a model of an electric component cooled down by air. Another great training resource in the Learning Center, which has videos covering all the fundamentals of the software.

Best,

Jeff

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Jeff Hiller
Hello Nadav, The fundamental problem here is that you have heat sources and nowhere for the heat to leave: all your outside boundaries are insulated. So no stationary solution exists. I also noticed that you have set up your model in such a way that any convection heat transfer in the air is neglected (because you're solving the heat transfer in solids equation in the air domain). Maybe you made that simplification knowingly, but I wanted to point it out in case that was not your intention. The [Introduction to COMSOL Multiphysics manual](https://www.comsol.com/documentation) includes a tutorial that shows how to set up a model of an electric component cooled down by air. Another great training resource in the [Learning Center](https://www.comsol.com/learning-center), which has videos covering all the fundamentals of the software. Best, Jeff
Sergei Yushanov Certified Consultant
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Posted: 5 years ago 16.01.2019, 14:29 MEZ

Nadav,

You have Thermal Insulation boundary condition at all exterior boundaries - all generated heat cannot leave computational domain. For steady-state study type this will give infinite temperature. Apply meaningfull boundary conditions at exterior boundaries to allow heat flux leave computational domain.

Regards,

Sergei

Nadav, You have Thermal Insulation boundary condition at all exterior boundaries - all generated heat cannot leave computational domain. For steady-state study type this will give infinite temperature. Apply meaningfull boundary conditions at exterior boundaries to allow heat flux leave computational domain. Regards, Sergei

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