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Negative temperature (T-293)K for a positive heat source w..r.t time
Posted 21 mar 2011, 09:36 GMT-4 Electromagnetic Heating, Heat Transfer & Phase Change 5 Replies
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Hi,
I want to study the temp distribution with respect to time using electro-thermal model. I am using jh interface in comsol.
All the boundaries are thermally insulated. Assume potential is some how applied to the top and bottom faces. So electromagnetic power loss density or resistive loss (sigma* |E|^2) is distributed every where in the bulk. It is of the order of at least 10^5. You can check from the model attached. So I expect an increase in temp w.r.t time or voltage magnitude of the source. It is rather opposite I am observing. These negative values are consistently increasing with increase in time and voltage. So it can not be noise.
Another issue is, there is some patch kind of thing is seen in the results? What is this and why?How to avoid this?
Has anyone got any idea? I do not seem to find any problem.
Thanks,
venkat
I want to study the temp distribution with respect to time using electro-thermal model. I am using jh interface in comsol.
All the boundaries are thermally insulated. Assume potential is some how applied to the top and bottom faces. So electromagnetic power loss density or resistive loss (sigma* |E|^2) is distributed every where in the bulk. It is of the order of at least 10^5. You can check from the model attached. So I expect an increase in temp w.r.t time or voltage magnitude of the source. It is rather opposite I am observing. These negative values are consistently increasing with increase in time and voltage. So it can not be noise.
Another issue is, there is some patch kind of thing is seen in the results? What is this and why?How to avoid this?
Has anyone got any idea? I do not seem to find any problem.
Thanks,
venkat
Attachments:
5 Replies Last Post 22 mar 2011, 02:54 GMT-4
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Posted:
1 decade ago
Hi
try to define 2 periodic conditions with only one source + destination pair per item i believe that will help
--
Good luck
Ivar
try to define 2 periodic conditions with only one source + destination pair per item i believe that will help
--
Good luck
Ivar
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Posted:
1 decade ago
Hi Ivar,
Thanks for the reply. I have defined 2 periodic conditions with only one source + destination pair per item. But this time it is not even converging. Earlier it was properly converging and giving negative temp.
The error message is
Repeated error test failures. May have reached a singularity.
Time : 0
Last time step is not converged.
What is the problem. Can you pl,. check the model?
Thanks,
Thanks for the reply. I have defined 2 periodic conditions with only one source + destination pair per item. But this time it is not even converging. Earlier it was properly converging and giving negative temp.
The error message is
Repeated error test failures. May have reached a singularity.
Time : 0
Last time step is not converged.
What is the problem. Can you pl,. check the model?
Thanks,
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Posted:
1 decade ago
Hi
I did a quick check, and I believe I only changed that, but I'm running the latest patch, that might make a difference ;)
--
Good luck
Ivar
I did a quick check, and I believe I only changed that, but I'm running the latest patch, that might make a difference ;)
--
Good luck
Ivar
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Posted:
1 decade ago
Did you mean version influence on results?
check the attached latest model with the periodic BCs defined as suggested.
The same error message is seen. There are no time varying sources and I have even changed the time stepping also. Not successful.
I have even run the modified model in V4.1 also and it says property solnum out of range. One more difference I have seen in 4.1. In 4.0 all the faces are defined as thermally insulated but if we open the same model in 4.1 then only top and bottom faces are considered as thermally insulated. Others faces it simply does not allow to define as thermally insulated as they are defined as periodic. But in 4.0 it allows thermal insulation for all other faces as well.
Your help is appreciated,
Thanks,
check the attached latest model with the periodic BCs defined as suggested.
The same error message is seen. There are no time varying sources and I have even changed the time stepping also. Not successful.
I have even run the modified model in V4.1 also and it says property solnum out of range. One more difference I have seen in 4.1. In 4.0 all the faces are defined as thermally insulated but if we open the same model in 4.1 then only top and bottom faces are considered as thermally insulated. Others faces it simply does not allow to define as thermally insulated as they are defined as periodic. But in 4.0 it allows thermal insulation for all other faces as well.
Your help is appreciated,
Thanks,
Attachments:
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Posted:
1 decade ago
Hi
What I clearly understood from the COMSOL conferences about two years ago now, was that V4.0 was a preliminary release to allow you to learn the new approach and to get feedback, so I used it in this way too. Since the 4.1 is here I have fully dropped 4.0, and I do not even try to import 4.0, I rebuild them in the latest version. With the last version I have no major issues, so I'm happy like that.
Now back to your issue. The solnum error appears for me if you do not clear correctly the solution, I mostly DELETE the solution of a old version when I try to load them.
If I run your model as is I get the same errors and "0" as result, if I delete the solution and solve it, it stops at 19.98 sec and hangs there. If I restart and stop it after 3-4 seconds it show clearly it has started to solve correctly, so there must be something else too in there ;
--
Good luck
Ivar
What I clearly understood from the COMSOL conferences about two years ago now, was that V4.0 was a preliminary release to allow you to learn the new approach and to get feedback, so I used it in this way too. Since the 4.1 is here I have fully dropped 4.0, and I do not even try to import 4.0, I rebuild them in the latest version. With the last version I have no major issues, so I'm happy like that.
Now back to your issue. The solnum error appears for me if you do not clear correctly the solution, I mostly DELETE the solution of a old version when I try to load them.
If I run your model as is I get the same errors and "0" as result, if I delete the solution and solve it, it stops at 19.98 sec and hangs there. If I restart and stop it after 3-4 seconds it show clearly it has started to solve correctly, so there must be something else too in there ;
--
Good luck
Ivar