# constant temperature heat source in subdomain

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 October 8, 2010, 07:22 constant temperature heat source in subdomain #1 Member   Sanyo Join Date: Apr 2009 Location: India Posts: 62 Rep Power: 17 Dear All, I want to specify the fixed value of temperature to a specific volume/zone in CFX. I searched on net & I knew that it can be done in fluent but I was not able to find anything for CFX. I can specify the heat source for a subdomain but then how would I keep the temperature constant? Thanks in advance. Regards, Sanyo

 October 8, 2010, 16:09 #2 Senior Member   Join Date: Mar 2009 Location: Europe Posts: 169 Rep Power: 17 What do you intend to model?

 October 9, 2010, 02:14 #3 Member   Sanyo Join Date: Apr 2009 Location: India Posts: 62 Rep Power: 17 Dear Joey, Thank you for your reply. I want to model fluidized bed combustion. However, combustion is not in our scope as well necessary data for combustion is not available. We know the temperature of the gas leaving the fluidized bed. So we thought that we might be able to model fluidized bed as subdomain with appropriate momentum loss & defining the fixed temperature to subdomain. Is it possible to define fixed temperature or should I use energy source? With energy source, we doubt that we wont be able to achieve exact temperature of gases. Thank you for your help. Regards, Sanyo

 October 9, 2010, 06:00 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,731 Rep Power: 143 Yes, you can fix a regions temperature with an energy source. I think there is an example of how to do it in the documentation. It has been ages since I did it but it is something like: Set the source term to -C(t-tSET) where tSET is your specified temperature. You then set the source term coefficient to -C (or is it +C, can't remember). C is a constant chosen to be large relative to any possible t, 1e6 should do the trick. This is from my flaky memory so I might have got some signs wrong but that is the basic idea. It is something like that.

October 12, 2010, 15:13
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Michael P. Owen
Join Date: Mar 2009
Posts: 196
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Quote:
 Originally Posted by ghorrocks Yes, you can fix a regions temperature with an energy source. I think there is an example of how to do it in the documentation. It has been ages since I did it but it is something like: Set the source term to -C(t-tSET) where tSET is your specified temperature. You then set the source term coefficient to -C (or is it +C, can't remember). C is a constant chosen to be large relative to any possible t, 1e6 should do the trick. This is from my flaky memory so I might have got some signs wrong but that is the basic idea. It is something like that.
Glenn, the source coefficient should be negative. However, no worries, if you forget and make it positive CFX will multiply it by -1.