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Non stop heating source

Posted Jun 22, 2011, 10:02 a.m. EDT Heat Transfer & Phase Change Version 4.1 3 Replies

Yoann Many
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Hello,

I'm trying to build a 2D model of a tube heated by a helicoïdal solenoid through which goes electricity (the solenoid). The whole system is surounding by air.

My problem is that I did the math to evaluate the heat flux density disipated by joule effect for a 2V potential (which is for my case rather small) and I obtain 1.38e8 W/m3. So I created in my model a corresponding heat source (I also did it with the joule heating module and it gave me similar results) and i did an analysis for 60 sec. And I have a temperature in my solenoid and in the surrounding air above 2000°C and I can't figure why.
There is no air flow so maybe it doesn't take into account free convection and that's wy hot air stay close to the heating source, but I'm not sure. I tried to add a laminar flow to see if air was moving but it didn't.
I'm kind of freaking out because it's the topic of my internship and none of my teachers would help me..

Find my model enclosed, take a look at it if you got time.
Thanks

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3 Replies Last Post Jun 23, 2011, 5:40 a.m. EDT
Lars Gregersen COMSOL Employee

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Posted: 1 decade ago Jun 22, 2011, 11:11 a.m. EDT
Hi

I know next to nothing about helicoïdal solenoids, but here are two immediate comments:

- Your geometry isn't a solenoid. You should perhaps create an axisymmetrical model for this

- Air is one of the best isolators that exist. Not taking its movement into account - in some way - is a mistake.


Lars Gregersen
Comsol Denmark
Hi I know next to nothing about helicoïdal solenoids, but here are two immediate comments: - Your geometry isn't a solenoid. You should perhaps create an axisymmetrical model for this - Air is one of the best isolators that exist. Not taking its movement into account - in some way - is a mistake. Lars Gregersen Comsol Denmark
Yoann Many
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Posted: 1 decade ago Jun 23, 2011, 2:53 a.m. EDT
Hi,

thanks for the reply and maybe I mistook in my translation (not a regular english-speaker), what I meant was a resistive component with circular section, winding round the tube. So the circles are like a cut view of my component which makes 5 spins. And you are right I only did half of the model, there is an horizontal symmetry to have the tube and the resistance fully, the fact is that I didn't know if it would have any importance for now.

And I don't know how to imitate a free convection, I just put some air with a large aera hoping that it would do, but the fluid isn't moving and pressure is constant. How should I do to add convection ?? With volume force ?
Thanks



Hi, thanks for the reply and maybe I mistook in my translation (not a regular english-speaker), what I meant was a resistive component with circular section, winding round the tube. So the circles are like a cut view of my component which makes 5 spins. And you are right I only did half of the model, there is an horizontal symmetry to have the tube and the resistance fully, the fact is that I didn't know if it would have any importance for now. And I don't know how to imitate a free convection, I just put some air with a large aera hoping that it would do, but the fluid isn't moving and pressure is constant. How should I do to add convection ?? With volume force ? Thanks
Yoann Many
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Posted: 1 decade ago Jun 23, 2011, 5:40 a.m. EDT
Ok so i managed to add heat convection in my air (I'm actually proud of myself) and I see that the heat is evacuated upwards, but I still have more than 2000 K in 3 minutes in my resistance, which is impossible and I wonder what I'm missing (the resistive component is 2500W)

Have someone any idea?? (I put my model below)
Ok so i managed to add heat convection in my air (I'm actually proud of myself) and I see that the heat is evacuated upwards, but I still have more than 2000 K in 3 minutes in my resistance, which is impossible and I wonder what I'm missing (the resistive component is 2500W) Have someone any idea?? (I put my model below)

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