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Radiation model

Posted 25 apr 2013, 11:40 GMT-4 Heat Transfer & Phase Change Version 4.1 3 Replies

Pablo López de uralde
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Hi,

I am starting to use Comsol and have problems making a simple model. It consists on a heat source ( rectangle for example) and a thin sheet of aluminum where I want to see how the temperature changes to locate any defect.
I have tried with surface-to-surface radiation, surface-to-ambient radiation and the result is that the is heated but nothing happens on the sheet.
I don´t know how to make it work and would appreciate some help.

Thank you

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3 Replies Last Post 26 apr 2013, 07:19 GMT-4
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 26 apr 2013, 02:13 GMT-4
Hi

first advice: when you add in physics, check the dependent variables, you will notice that HT solves for T and for J (radiousity) while the RAD physics solves also for "J" so you double up. For me only HT is enough, but to get the surface to surface exchange you need to turn it on by selecting it in the main HT physics node

Then when you want to turn on or off a heat source use rather a SMOOTH step function (Model - Definitions Functions) and be aware in transient, if you start at t=0 your initial conditions should be coherent, else run first a stationary case to settle all fluxes correctly, then run a temporal study from the steady state results


--
Good luck
Ivar
Hi first advice: when you add in physics, check the dependent variables, you will notice that HT solves for T and for J (radiousity) while the RAD physics solves also for "J" so you double up. For me only HT is enough, but to get the surface to surface exchange you need to turn it on by selecting it in the main HT physics node Then when you want to turn on or off a heat source use rather a SMOOTH step function (Model - Definitions Functions) and be aware in transient, if you start at t=0 your initial conditions should be coherent, else run first a stationary case to settle all fluxes correctly, then run a temporal study from the steady state results -- Good luck Ivar
Pablo López de uralde
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Posted: 1 decade ago 26 apr 2013, 06:58 GMT-4


I have made the model with HT but still the source is heated but not the sheet. I have added a rectangle of air to simulate the room and now the sheet is heated.

My problem now is that the source continues heating even when it is supposed to be turned off and the same happens with the sheet.


Thank you for your help.

Pablo
I have made the model with HT but still the source is heated but not the sheet. I have added a rectangle of air to simulate the room and now the sheet is heated. My problem now is that the source continues heating even when it is supposed to be turned off and the same happens with the sheet. Thank you for your help. Pablo
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 26 apr 2013, 07:19 GMT-4
Hi

try using the Model Definitions Probe plots to monitor what is happening, use also the solver plot while solving to follow relevant variables. This helps to debug more complex models

--
Good luck
Ivar
Hi try using the Model Definitions Probe plots to monitor what is happening, use also the solver plot while solving to follow relevant variables. This helps to debug more complex models -- Good luck Ivar

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