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error occurred while solving a heat problem

Posted 8 mars 2010, 06:55 UTC−5 5 Replies

Ziv Seemann
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Hello I'm a new user with comsol,
I need to solve a heating problem in a closed space.

In order to do so I'm using comsol multiphysics - incompressible naviar stokes and convection and conduction.

Defining the geometry, boundary and subdomains I first solved it only with convection and conduction to simplify thing for the solver and when I tried to use solve the whole problem I got an error something like sqrt(-1).

Where did I go wrong?

And another question:
If I'm trying to use a fan and I want to set the boundary I have only velocity boundary that fits,
But I need to enter a source (Q) to the equation so how do I do it?

I'm attaching the file that i made

Thanx!!!!!!!
5 Replies Last Post 10 mars 2010, 09:31 UTC−5
Ziv Seemann
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Posted: 1 decade ago 10 mars 2010, 02:19 UTC−5
help anyone???
help anyone???
Ziv Seemann
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Posted: 1 decade ago 10 mars 2010, 02:30 UTC−5
i forgot the file:
rapidshare.com/files/361389700/didnt_work.mph

thanx
i forgot the file: http://rapidshare.com/files/361389700/didnt_work.mph thanx
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 10 mars 2010, 02:32 UTC−5
Hi

first of all you did not attach any file and ist difficult to understand your true problem, as when you are mixing several physics many things can arrive.

the sqrt(-1) sas that you are getting imaginary solutions, while COMSOL did not expect so, there is an option in the solver to turn on "imaginary" when they arrive unexpected for COMSOL, but it would be best to understand why and if it "is expected" (it typically arrives in RF with EM waves and so)

You talk about closed space (for me means isolated) and heat exchange, then be sure you balance well your in/out heat exchange as this will fully define your steady state temperature

Try it out on a simpler model going step by step, that is the best way, mixing all physics is not that obvious in the beginning

good luck
Ivar
Hi first of all you did not attach any file and ist difficult to understand your true problem, as when you are mixing several physics many things can arrive. the sqrt(-1) sas that you are getting imaginary solutions, while COMSOL did not expect so, there is an option in the solver to turn on "imaginary" when they arrive unexpected for COMSOL, but it would be best to understand why and if it "is expected" (it typically arrives in RF with EM waves and so) You talk about closed space (for me means isolated) and heat exchange, then be sure you balance well your in/out heat exchange as this will fully define your steady state temperature Try it out on a simpler model going step by step, that is the best way, mixing all physics is not that obvious in the beginning good luck Ivar
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 10 mars 2010, 03:52 UTC−5
Hi

an advice for easier downloads:

remove the slution and zip te file, then you can easily attach it directly to the forum ;)
Ivar
Hi an advice for easier downloads: remove the slution and zip te file, then you can easily attach it directly to the forum ;) Ivar
Ziv Seemann
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Posted: 1 decade ago 10 mars 2010, 09:31 UTC−5
thanx,

when im talking about closed space i meen a space filled with nitrogen at 50 KPa (0.5 atm)

i understand that there is a problem but i cant find it,

the phisics is heat insied and tempreture outside so i will get the temp that will heppend.
there is no heat exchengers only a heat source,fan and outsidew temp.

im sorry but i cant upload the file even when its .zip
the file is at rapidshare.com/files/361389700/didnt_work.mph

thanx!!!!!
thanx, when im talking about closed space i meen a space filled with nitrogen at 50 KPa (0.5 atm) i understand that there is a problem but i cant find it, the phisics is heat insied and tempreture outside so i will get the temp that will heppend. there is no heat exchengers only a heat source,fan and outsidew temp. im sorry but i cant upload the file even when its .zip the file is at http://rapidshare.com/files/361389700/didnt_work.mph thanx!!!!!

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