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Changing dependent variable

Posted Mar 14, 2012, 5:16 p.m. EDT Heat Transfer & Phase Change Version 4.2 3 Replies

Sonya Konzak
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I am working with a 2D heat transfer model for a solid cylindrical conductor. The dependent variable is the temperature throughout the 2D cylindrical cross section (shaped as a circle) , which is calculated based on the heat balance equation (taking into account heat gain from conduction and solar radiation as well as heat losses from convection and radiative cooling). I would like to modify the model such that the conductor core temperature be set (to 80degC, for example) and the current be calculated. In other words, I am trying to calculate the conductor's current carrying capacity for a series of set parameter values. Do you have any insight on how I can get this done? I tried changing the dependent variable of my model, but it seems fixed to the temperature.

Thanks,
Sonya
3 Replies Last Post Mar 15, 2012, 9:54 a.m. EDT
Edgar Kaiser
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Posted: 1 decade ago Mar 15, 2012, 8:39 a.m. EDT
Sonya,

I am not sure if I understand you properly.

You want to set the whole heat conductor to constant temperature? Then there won't be any heat flow, because heat flow needs a temperature gradient.

Or do you want to have a heat source (or sink) at a certain temperature inside the conductor. Then you can define appropriate geometry and set boundary temperature.

Cheers
Edgar


Cheers
Edgar
Sonya, I am not sure if I understand you properly. You want to set the whole heat conductor to constant temperature? Then there won't be any heat flow, because heat flow needs a temperature gradient. Or do you want to have a heat source (or sink) at a certain temperature inside the conductor. Then you can define appropriate geometry and set boundary temperature. Cheers Edgar Cheers Edgar
Sonya Konzak
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Posted: 1 decade ago Mar 15, 2012, 9:33 a.m. EDT
Thanks for your reply. I don't want to set the entire conductor temperature, just the core (the center point). I agree with you that I can likely do this by setting a heat source, but then how can I calculate the current? I imagine I would have to enter a new dependent variable?
Thanks for your reply. I don't want to set the entire conductor temperature, just the core (the center point). I agree with you that I can likely do this by setting a heat source, but then how can I calculate the current? I imagine I would have to enter a new dependent variable?
Edgar Kaiser
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Posted: 1 decade ago Mar 15, 2012, 9:54 a.m. EDT

You can't use the center point, this would result in a singularity. But you can define a small cylinder around the center and subtract it from the big cylinder. This gives you a cylinder with a bore hole. Now set the inner boundary to a certain temperature. Then integrate the normal heat flow on this inner boundary or on the outside boundary. The result should be the same with opposite sign.

cheers
Edgar
You can't use the center point, this would result in a singularity. But you can define a small cylinder around the center and subtract it from the big cylinder. This gives you a cylinder with a bore hole. Now set the inner boundary to a certain temperature. Then integrate the normal heat flow on this inner boundary or on the outside boundary. The result should be the same with opposite sign. cheers Edgar

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