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COMSOL help needed. (RF module - Heating of water using waveguide)

Hello there, I am a relatively new COMSOL user who is in the process of validating a paper, to be able to get a better grasp at COMSOL. The paper I am trying to validate using my simulation can be...

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Re: COMSOL help needed. (RF module - Heating of water using waveguide)

In the model that you have uploaded you have not defined the imaginary part of the permittivity of the water. This is exactly the parameter that defines the losses.

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Re: COMSOL help needed. (RF module - Heating of water using waveguide)

But I have defined the real part and the loss tangent(delta) Shouldn't that be enough?

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Re: COMSOL help needed. (RF module - Heating of water using waveguide)

It is enough information because the imaginary part can indeed be calculated from the real part, the loss tangent and the conductivity (en.wikipedia.org/wiki/Dielectric_loss). But maybe COMSOL does not...

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Re: COMSOL help needed. (RF module - Heating of water using waveguide)

I took your advice Pieter and included the imaginary part too.. which is simple tan(delta) * real part. However there is no difference in the results obtained. The water body seems to be not heating up...

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Re: COMSOL help needed. (RF module - Heating of water using waveguide)

I see. I cannot evaluate your model myself, i get the error Nonlinear solver did not converge. In segregated group 1: Time : 10.02836128938059 Segregated group 1 Undefined value found. Undefined value...

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Re: COMSOL help needed. (RF module - Heating of water using waveguide)

I included in the attachment a solution to the error you are getting. This should not give you any errors. However the results as you can see if you go to study are incorrect.

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Re: COMSOL help needed. (RF module - Heating of water using waveguide)

You have no electric field inside your water. Maybe you should include the water domain (2) in the 'wave equation, electric 1' node.

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Re: COMSOL help needed. (RF module - Heating of water using waveguide)

I am not so sure about that Pieter. Because The domain for the water body is assigned to Microwave heating model. THe wave equation, electric is only there to show that the air domains need not take...

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Re: COMSOL help needed. (RF module - Heating of water using waveguide)

Well, what I see in the potato heating example from the model library is that the electric field node is defined also in the material that is heated. Subsequently the electromagnetic heat source is...

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Re: COMSOL help needed. (RF module - Heating of water using waveguide)

Yes that's correct Pieter. I tried to use the rf waveguide model, to try and simulate this situation. Everything runs and simulation converges now, however the results are impossible.. in 60 seconds...

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Re: COMSOL help needed. (RF module - Heating of water using waveguide)

Yes this indeed strange, even if all the energy inserted at Port 1 would go into the water, 60 s at 300 Watt should only increase the temperature of this amount of water by something like 35 K. What is...

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Re: COMSOL help needed. (RF module - Heating of water using waveguide)

Port 2 is unexcited, so it would be a way to absorb the incoming microwaves from port 1 I believe.

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Re: COMSOL help needed. (RF module - Heating of water using waveguide)

Ok, so that is what would happen if you would hack your microwave oven to work with the door open. But that is no explanation of why your water heats so fast, I would instead expect a lot of energy to...

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COMSOL help needed. (RF module - Heating of water using waveguide)

Hello there, I am a relatively new COMSOL user who is in the process of validating a paper, to be able to get a better grasp at COMSOL. The paper I am trying to validate using my simulation can be...

View Article


Re: COMSOL help needed. (RF module - Heating of water using waveguide)

In the model that you have uploaded you have not defined the imaginary part of the permittivity of the water. This is exactly the parameter that defines the losses.

View Article

Re: COMSOL help needed. (RF module - Heating of water using waveguide)

But I have defined the real part and the loss tangent(delta) Shouldn't that be enough?

View Article


Re: COMSOL help needed. (RF module - Heating of water using waveguide)

It is enough information because the imaginary part can indeed be calculated from the real part, the loss tangent and the conductivity (en.wikipedia.org/wiki/Dielectric_loss). But maybe COMSOL does not...

View Article

Re: COMSOL help needed. (RF module - Heating of water using waveguide)

I took your advice Pieter and included the imaginary part too.. which is simple tan(delta) * real part. However there is no difference in the results obtained. The water body seems to be not heating up...

View Article

Re: COMSOL help needed. (RF module - Heating of water using waveguide)

I see. I cannot evaluate your model myself, i get the error Nonlinear solver did not converge. In segregated group 1: Time : 10.02836128938059 Segregated group 1 Undefined value found. Undefined value...

View Article
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