Interface Model:None or zero thermal conductance?

mak86 · October 10, 2010, 11:16

Dear all,
In defining domain interfaces in CFX there are 3 options for interface model: None,Thermal conductance and Thin Material.
what is the difference between choosing none or a zero thermal conductance?
I have solved the same problem with these two options and I got different results.
Thanks

gardian · October 11, 2010, 05:04

I think you should have a look in the help . the physics is different in every case. in case you have a solid immersed in a fluid you should check also what the conjugate heat transfer is ..

mak86 · October 11, 2010, 15:41

I read the documentation but there is no description for the none option.
The two others do the same job in different ways.

"Heat Transfer

Determines whether or not heat transfer models are applied between the sides of the interface.
The options are:

Conservative Interface Flux
This option enables you to define the Thermal Contact Resistance or Thin Material, which are two ways of defining the same characteristics. That is, if you do not know the contact resistance, you can define the thin material and its thickness and have the solver derive the resistance"

ghorrocks · October 11, 2010, 19:09

None means no interface material, and heat is transferred across the interface with no loss or resistance. The other options add thermal resistance, they just calculate the thermal resistance different ways.

mak86 · October 12, 2010, 02:43

Dear ghorroks,
If so None and a zero thermal resistance must give the same result, I have tried this and the results were different!

ghorrocks · October 12, 2010, 19:18

I have not used these options so do not know in detail. But I would have assumed zero thermal resistance then should be the same as the none option. If you have a case which shows it is not the same then talk to CFX Support as you may have found a bug.

michael_owen · October 12, 2010, 23:15

Quote:

Originally Posted by mak86

Dear ghorroks,
If so None and a zero thermal resistance must give the same result, I have tried this and the results were different!

How different? Provide plots.

October 10, 2010, 11:16	Interface Model:None or zero thermal conductance?	#1
mak86 New Member Join Date: Jul 2010 Posts: 23 Rep Power: 16	Dear all, In defining domain interfaces in CFX there are 3 options for interface model: None,Thermal conductance and Thin Material. what is the difference between choosing none or a zero thermal conductance? I have solved the same problem with these two options and I got different results. Thanks

October 11, 2010, 15:41		#3
mak86 New Member Join Date: Jul 2010 Posts: 23 Rep Power: 16	I read the documentation but there is no description for the none option. The two others do the same job in different ways. "Heat Transfer Determines whether or not heat transfer models are applied between the sides of the interface. The options are: Conservative Interface Flux This option enables you to define the Thermal Contact Resistance or Thin Material, which are two ways of defining the same characteristics. That is, if you do not know the contact resistance, you can define the thin material and its thickness and have the solver derive the resistance"

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October 11, 2010, 05:04		#2
gardian New Member anton.gardi Join Date: Aug 2010 Posts: 21 Rep Power: 16	I think you should have a look in the help . the physics is different in every case. in case you have a solid immersed in a fluid you should check also what the conjugate heat transfer is ..

October 11, 2010, 19:09		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	None means no interface material, and heat is transferred across the interface with no loss or resistance. The other options add thermal resistance, they just calculate the thermal resistance different ways.

October 12, 2010, 02:43		#5
mak86 New Member Join Date: Jul 2010 Posts: 23 Rep Power: 16	Dear ghorroks, If so None and a zero thermal resistance must give the same result, I have tried this and the results were different!

October 12, 2010, 19:18		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	I have not used these options so do not know in detail. But I would have assumed zero thermal resistance then should be the same as the none option. If you have a case which shows it is not the same then talk to CFX Support as you may have found a bug.