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Heat Transfer by Conduction
Posted Feb 3, 2010, 7:22 a.m. EST 1 Reply
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Hi!
I'm new to Comsol and I'm using Heat Transfer by Conduction. The setup is a piece of stainless steel in touch with another material. Now here come the two questions.
1. Right now I'm assigning to the piece of metal a constant temperature on the boundaries or rather a function with a linear increase to a constant value which will remain over time. But I've read in a paper that people instead assigned a value for Q (Heat source in subdomain) or a function for Q. I don't get the difference.
2. The simulation runs but I want to dislpay isotherms after the processing, i.e. to display a zone that is frozen. Is that possible?
Thank you in advance!
Flo
I'm new to Comsol and I'm using Heat Transfer by Conduction. The setup is a piece of stainless steel in touch with another material. Now here come the two questions.
1. Right now I'm assigning to the piece of metal a constant temperature on the boundaries or rather a function with a linear increase to a constant value which will remain over time. But I've read in a paper that people instead assigned a value for Q (Heat source in subdomain) or a function for Q. I don't get the difference.
2. The simulation runs but I want to dislpay isotherms after the processing, i.e. to display a zone that is frozen. Is that possible?
Thank you in advance!
Flo
1 Reply Last Post Feb 4, 2010, 12:59 a.m. EST
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Posted:
1 decade ago
Hi
I can (again) insist: read carefully the documentation a couple of times and do the exercises, when you are a newcomer, I know it's more fun to try out your own cases, but you will progress quicker that way.
Anyhow I hop I can give you some replies:
1) the difference between imposed temperature and T and a heat source Q, well in one case you do as said: impose the temperature independently of how much power is required, the power is adapted implicitely to get the imposed temperature. If you do this on a volume, you will see no gradients, if you do this on a edge /surface of a volume you might get temperature differences in a temporal analysis, and if you do not impose any losses you will also see a constant temperature for a stationary analysis as you are waiting an infinite long time, which allows the temperature to settle everywhere.
In a transient analysis (depending on "t" see your equations) you can define a temperature BC (boundary condition) as a function of time, what I understand you do.
2) imposing the "Q" heat source (or sink depends on sign) you input some energy, possibly with a time variation, that is transfomed into heat (hence a temperature change) via the material heat capacity and its density (check the units they are very usefull to helpt to get the logic right). Imposing a volume=subdomain heat source is an even energy distributed over the subdomain, if you apply it on a boundary it's like heating the surface with an external heatsource. With a heat source and sink you get about always T gradients, in stationary and in the time domain analysis.
By the way, when you look at the time dependent plots, do no forget to select the moment of interest in the postprocessing plot general tab
Good luck
Ivar
I can (again) insist: read carefully the documentation a couple of times and do the exercises, when you are a newcomer, I know it's more fun to try out your own cases, but you will progress quicker that way.
Anyhow I hop I can give you some replies:
1) the difference between imposed temperature and T and a heat source Q, well in one case you do as said: impose the temperature independently of how much power is required, the power is adapted implicitely to get the imposed temperature. If you do this on a volume, you will see no gradients, if you do this on a edge /surface of a volume you might get temperature differences in a temporal analysis, and if you do not impose any losses you will also see a constant temperature for a stationary analysis as you are waiting an infinite long time, which allows the temperature to settle everywhere.
In a transient analysis (depending on "t" see your equations) you can define a temperature BC (boundary condition) as a function of time, what I understand you do.
2) imposing the "Q" heat source (or sink depends on sign) you input some energy, possibly with a time variation, that is transfomed into heat (hence a temperature change) via the material heat capacity and its density (check the units they are very usefull to helpt to get the logic right). Imposing a volume=subdomain heat source is an even energy distributed over the subdomain, if you apply it on a boundary it's like heating the surface with an external heatsource. With a heat source and sink you get about always T gradients, in stationary and in the time domain analysis.
By the way, when you look at the time dependent plots, do no forget to select the moment of interest in the postprocessing plot general tab
Good luck
Ivar