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Very High Temperature in Joule Heating Simulation

Posted 4 giu 2021, 10:03 GMT-4 Electromagnetic Heating, Low-Frequency Electromagnetics, MEMS & Nanotechnology Version 5.6 3 Replies

Omar Othman
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Hi When I am simulating a 3D electrical heater using joule heating physics on comsol I faced a problem that when I am using an electrical potential of 12V the Temperature increase to the 10^6 K. I have tried the examples of comsol about joule heating and I noticed that if I change set V=12V in these example without changing anything on the example they gave me also a Temperature 10^6. If anybody find the solution of this problem please reply! Thank You!

3 Replies Last Post 7 giu 2021, 02:46 GMT-4
Jeff Hiller COMSOL Employee

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Posted: 3 years ago 4 giu 2021, 10:16 GMT-4

Hi Omar,

If a device has a low resistance, applying a 12V voltage drop to it can cause large current densities and therefore a high heat source.

In addition to that, if the boundary conditions or other temperature-limiting mechanisms are such that the device cannot cool efficiently, even a modest heat source can cause the temperature to rise a lot.

So, I would recommend you look at what the resistance of the device is and how realistic your modeling of the thermal BCs is.

Best,

Jeff

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Jeff Hiller
Hi Omar, If a device has a low resistance, applying a 12V voltage drop to it can cause large current densities and therefore a high heat source. In addition to that, if the boundary conditions or other temperature-limiting mechanisms are such that the device cannot cool efficiently, even a modest heat source can cause the temperature to rise a lot. So, I would recommend you look at what the resistance of the device is and how realistic your modeling of the thermal BCs is. Best, Jeff
Omar Othman
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Posted: 3 years ago 4 giu 2021, 18:20 GMT-4
Updated: 3 years ago 5 giu 2021, 04:52 GMT-4

Hi Jeff,

Thanks for your reply and help! I am using Nichrome as a wire of the electrical heater (Material properties are Add-In from Comsol material properties) and the BC of the thermal BC's is only convection at the all sides (hair=5 w/m2.K and T=25 degC) and still the Temp is 10^4~5. However in real life application (nichrome wires and MgO outline) the heater required approx. V=12.6V and I=3.2A and the resistivity is 4ohm and the maximum Temperature reached is 350 degC with insulator on the boundary. So how can I simulate this heater (with the exact geometry) to get solution close to the real life application without changing the material.

Thank you for your considreation!

Omar

Hi Jeff, Thanks for your reply and help! I am using Nichrome as a wire of the electrical heater (Material properties are Add-In from Comsol material properties) and the BC of the thermal BC's is only convection at the all sides (hair=5 w/m2.K and T=25 degC) and still the Temp is 10^4~5. However in real life application (nichrome wires and MgO outline) the heater required approx. V=12.6V and I=3.2A and the resistivity is 4ohm and the maximum Temperature reached is 350 degC with insulator on the boundary. So how can I simulate this heater (with the exact geometry) to get solution close to the real life application without changing the material. Thank you for your considreation! Omar
Lars Gregersen COMSOL Employee

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Posted: 3 years ago 7 giu 2021, 02:46 GMT-4

The resistance is not constant. When the temperature increases the resistance increases as well (for metals). You need to include that effect in your model.

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Lars Gregersen
Comsol Denmark
The resistance is not constant. When the temperature increases the resistance increases as well (for metals). You need to include that effect in your model.

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