[CFXv11]contact thermal conductance

mactech001 · August 17, 2010, 11:35

Dear all,

i would like to perform a CHT analysis on a multi-body model. comparing simulation and test, i found that test has a higher temperature than simulated, letting me to think that probably due to insufficient contact between bodies, heat transfer from inside of body to fluid was not good due to some contact thermal resistance/conductance.

but, how can i implement contact thermal resistance/conductance in CFX please? the defined solid-solid interface boundary has no option for me to define a thermal resistance.

please help.

regards,
mactech001

DukeLeto · August 17, 2010, 15:31

How many place do you know the temperature in the test? It could be that CFX is over predicting the heat transfer at the surface.

- Try the SST model with suitable Y+ (say, less than 100 to begin with, possibly down to as low as 2).

- It is best to have a GGI interface between the solid and the fluid regions.

If the surface temperature at the fluid is good, but the internal solidtemperatures are too low, you have no alternative but to add a thin solid region and assign a suitable thermal conductivity.

ghorrocks · August 17, 2010, 19:50

CFX V12 has contact resistance between solid bodies. Looks like it is time to upgrade to the current version.

There is no support for contact resistance in CFX V11 or earlier, the easiest way to do it is by inserting a thin region of elements and adjust the conductivity of these elements to give the correct contact resistance. Not recommended.

August 17, 2010, 11:35	[CFXv11]contact thermal conductance	#1
mactech001 Senior Member Join Date: Nov 2009 Posts: 125 Rep Power: 17	Dear all, i would like to perform a CHT analysis on a multi-body model. comparing simulation and test, i found that test has a higher temperature than simulated, letting me to think that probably due to insufficient contact between bodies, heat transfer from inside of body to fluid was not good due to some contact thermal resistance/conductance. but, how can i implement contact thermal resistance/conductance in CFX please? the defined solid-solid interface boundary has no option for me to define a thermal resistance. please help. regards, mactech001 __________________ Thank you for your kind attention. Kind regards, mactech001 Currently using: ANSYS v13

August 17, 2010, 15:31	CHT problem	#2
DukeLeto New Member Dr. Richard R. Lange Join Date: Jun 2010 Location: Pittsburgh Posts: 5 Rep Power: 16	How many place do you know the temperature in the test? It could be that CFX is over predicting the heat transfer at the surface. - Try the SST model with suitable Y+ (say, less than 100 to begin with, possibly down to as low as 2). - It is best to have a GGI interface between the solid and the fluid regions. If the surface temperature at the fluid is good, but the internal solidtemperatures are too low, you have no alternative but to add a thin solid region and assign a suitable thermal conductivity.

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August 17, 2010, 19:50		#3
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	CFX V12 has contact resistance between solid bodies. Looks like it is time to upgrade to the current version. There is no support for contact resistance in CFX V11 or earlier, the easiest way to do it is by inserting a thin region of elements and adjust the conductivity of these elements to give the correct contact resistance. Not recommended.