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Posted:
1 decade ago
May 21, 2014, 11:42 a.m. EDT
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.
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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Posted:
1 decade ago
May 21, 2014, 12:02 p.m. EDT
But I have defined the real part and the loss tangent(delta)
Shouldn't that be enough?
But I have defined the real part and the loss tangent(delta)
Shouldn't that be enough?
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Posted:
1 decade ago
May 22, 2014, 2:59 a.m. EDT
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 do this calculation and you have to do it yourself?
It is enough information because the imaginary part can indeed be calculated from the real part, the loss tangent and the conductivity (http://en.wikipedia.org/wiki/Dielectric_loss). But maybe COMSOL does not do this calculation and you have to do it yourself?
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Posted:
1 decade ago
May 22, 2014, 9:23 a.m. EDT
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 at all.
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 at all.
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Posted:
1 decade ago
May 22, 2014, 9:32 a.m. EDT
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 found in the stiffness matrix.
For mesh-case 1 there are 316 equations giving NaN/Inf in the matrix rows for the variable mod1.E10.
and similarly for the degrees of freedom, NaN/Inf in the matrix columns.
Last time step is not converged.
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 found in the stiffness matrix.
For mesh-case 1 there are 316 equations giving NaN/Inf in the matrix rows for the variable mod1.E10.
and similarly for the degrees of freedom, NaN/Inf in the matrix columns.
Last time step is not converged.
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Posted:
1 decade ago
May 22, 2014, 9:34 a.m. EDT
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.
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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Posted:
1 decade ago
May 22, 2014, 11:04 a.m. EDT
You have no electric field inside your water. Maybe you should include the water domain (2) in the 'wave equation, electric 1' node.
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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Posted:
1 decade ago
May 22, 2014, 11:33 a.m. EDT
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 part in the microwave heating physics.
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 part in the microwave heating physics.
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Posted:
1 decade ago
May 23, 2014, 2:39 a.m. EDT
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 only defined in the potato so that only there the heating happens.
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 only defined in the potato so that only there the heating happens.
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Posted:
1 decade ago
May 23, 2014, 3:01 p.m. EDT
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 the maximum temperature reached is 120 degC..
Perhaps there is something wrong with the physics again.
Another thing that I noted is if I change from loss tangent to relative permittivity in the microwave model physics, my solution does not converge(doesnt give me an error but keeps runnign, I left it on for 2 nights..)
Any help would be greatly appreciated.
Edit: I have included in the attachment the new model.
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 the maximum temperature reached is 120 degC..
Perhaps there is something wrong with the physics again.
Another thing that I noted is if I change from loss tangent to relative permittivity in the microwave model physics, my solution does not converge(doesnt give me an error but keeps runnign, I left it on for 2 nights..)
Any help would be greatly appreciated.
Edit: I have included in the attachment the new model.
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Posted:
1 decade ago
May 26, 2014, 3:35 a.m. EDT
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 the purpose of Port 2?
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 the purpose of Port 2?
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Posted:
1 decade ago
May 26, 2014, 10:38 a.m. EDT
Port 2 is unexcited, so it would be a way to absorb the incoming microwaves from port 1 I believe.
Port 2 is unexcited, so it would be a way to absorb the incoming microwaves from port 1 I believe.
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Posted:
1 decade ago
May 28, 2014, 7:32 a.m. EDT
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 escape through port 2, so that less of it ends up in your water. Frankly I have no idea of why your results are not correct. Have you tried if mesh refinement/coarsening has any influence on the result?
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 escape through port 2, so that less of it ends up in your water. Frankly I have no idea of why your results are not correct. Have you tried if mesh refinement/coarsening has any influence on the result?
