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Coupling Heat Transfer w/ RF Module

Posted 19 ago 2015, 16:37 GMT-4 RF & Microwave Engineering, Heat Transfer & Phase Change 5 Replies

Lawrence Lau
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Hi

I am wondering if it is possible to use the RF module as a heating source, similar to the tutorial model that uses joule heating. I am attempting to do so, but I keep running in to this error.

Failed to evaluate variable Jacobian.
- Variable: freq
- Geometry: 1
- Domain: 1

I think that means that there is some kind of an undefined variable in Domain 1, but when I look at the specified material, all the properties are defined.

Any help at all is much appreciated. Thank you.
5 Replies Last Post 20 ago 2015, 12:49 GMT-4
Dennis Brown
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Posted: 9 years ago 20 ago 2015, 08:36 GMT-4
Check the model library for the microwave heating file. Also check the archive of videos as there are a couple versions that show microwave heating with the same waveguide.
Check the model library for the microwave heating file. Also check the archive of videos as there are a couple versions that show microwave heating with the same waveguide.
Sergei Yushanov Certified Consultant
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Posted: 9 years ago 20 ago 2015, 10:20 GMT-4
Lawrence,

Try to define global parameter "freq" to get rid of error message. Make sure that global parameter "freq" has the same numerical value as the frequency specified in the RF physics.

Regards,
Sergei
Lawrence, Try to define global parameter "freq" to get rid of error message. Make sure that global parameter "freq" has the same numerical value as the frequency specified in the RF physics. Regards, Sergei
Walter Frei COMSOL Employee

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Posted: 9 years ago 20 ago 2015, 10:49 GMT-4
Hello,

Yes, Dennis is correct, the appropriate place to start here would be to look at the Application Gallery examples related to RF Heating, in particular:

www.comsol.com/model/rf-heating-6078
www.comsol.com/model/microwave-oven-1424
www.comsol.com/model/microwave-heating-of-a-cancer-tumor-30

You should follow the study settings in these examples, rather than redefining any built-in variables such as "freq".
Hello, Yes, Dennis is correct, the appropriate place to start here would be to look at the Application Gallery examples related to RF Heating, in particular: http://www.comsol.com/model/rf-heating-6078 http://www.comsol.com/model/microwave-oven-1424 http://www.comsol.com/model/microwave-heating-of-a-cancer-tumor-30 You should follow the study settings in these examples, rather than redefining any built-in variables such as "freq".
Lawrence Lau
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Posted: 9 years ago 20 ago 2015, 12:41 GMT-4
Thank you Sergei, that worked for me.

I'm running into another error now that reads:

Failed to evaluate variable Jacobian.
- Variable: mod1.emw.Qh
- Geometry: 1
- Domain: 1

I've separated domain 1 from the Electromagnetic Waves module because that domain should not be supplying any heating in the model. I've opened up equation view and can see emw.Qh under Wave Equation, but the expression for emw.Qh applies only domains 2, 3, 4, 5, and 6, so I do not see why I would be getting an error concerning emw.Qh for domain 1.

I'm still a beginner at using COMSOL so any help at all is appreciated.
Thank you Sergei, that worked for me. I'm running into another error now that reads: Failed to evaluate variable Jacobian. - Variable: mod1.emw.Qh - Geometry: 1 - Domain: 1 I've separated domain 1 from the Electromagnetic Waves module because that domain should not be supplying any heating in the model. I've opened up equation view and can see emw.Qh under Wave Equation, but the expression for emw.Qh applies only domains 2, 3, 4, 5, and 6, so I do not see why I would be getting an error concerning emw.Qh for domain 1. I'm still a beginner at using COMSOL so any help at all is appreciated.
Sergei Yushanov Certified Consultant
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Posted: 9 years ago 20 ago 2015, 12:49 GMT-4
Lawrence,

Could you upload the model? Make sure you Clear Solutions before uploading.

Regards,
Sergei
Lawrence, Could you upload the model? Make sure you Clear Solutions before uploading. Regards, Sergei

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