Huge Heat Transfer Coefficient with SST turbulence model

andoss · September 14, 2009, 05:13

Hello!

I am modelling conjugate heat transfer at a pipe - the pipe is cooled by air, which flows through the pipe. Therefor I use the SST turbulence model. The y+ value is y+ <1 (around 0.5) The number of nodes in the boundary layer is about 15. The value for the wall heat transfer coefficient which i got from the simulation is very high with 26105,7 W/m²K (From analytical calculations I got a value around 650 W/m²K)

Does someone know what the reason could be?

Thank you in advance,
Andy

denizen · September 14, 2009, 06:10

try to check reference temperature for calculation of HTC

andoss · September 15, 2009, 10:23

The temperatures are ok. I did the simulation also with the k epsilon turbulence model (with scaleable wall functions) and then I got much better results than with the sst model. So I dont understand why the results with use of the sst turbulence modell are so high.

ghorrocks · September 15, 2009, 19:29

I don't think you have understood denizen's point. HTC is by default referenced to a local temperature which is another variable available for viewing in CFD-Post called "Wall Adjacent Temperature". This variable is often miles away from the reference temperature an engineer would use in the bulk flow.

andoss · January 9, 2010, 08:40

Thank you! This was very helpful!

September 14, 2009, 05:13	Huge Heat Transfer Coefficient with SST turbulence model	#1
andoss New Member Andi Join Date: Aug 2009 Location: Austria/Graz Posts: 5 Rep Power: 17	Hello! I am modelling conjugate heat transfer at a pipe - the pipe is cooled by air, which flows through the pipe. Therefor I use the SST turbulence model. The y+ value is y+ <1 (around 0.5) The number of nodes in the boundary layer is about 15. The value for the wall heat transfer coefficient which i got from the simulation is very high with 26105,7 W/m²K (From analytical calculations I got a value around 650 W/m²K) Does someone know what the reason could be? Thank you in advance, Andy

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Huge Wall Heat Transfer Coefficients with SST Mode	Marco MÃ¼ller	CFX	3	December 19, 2008 08:55
How can I increase Heat Transfer at Domain Interf?	B.Simon	CFX	3	October 28, 2008 19:53
heat transfer with s2s radiation model in fluent	D. L.	FLUENT	3	July 31, 2008 08:40
Natural convection - Inlet boundary condition	max91	CFX	1	July 29, 2008 21:28
Overall heat transfer coefficient	Nav	CFX	3	July 15, 2008 10:01

September 14, 2009, 06:10		#2
denizen New Member Join Date: Mar 2009 Posts: 25 Rep Power: 0	try to check reference temperature for calculation of HTC

September 15, 2009, 10:23		#3
andoss New Member Andi Join Date: Aug 2009 Location: Austria/Graz Posts: 5 Rep Power: 17	The temperatures are ok. I did the simulation also with the k epsilon turbulence model (with scaleable wall functions) and then I got much better results than with the sst model. So I dont understand why the results with use of the sst turbulence modell are so high.

September 15, 2009, 19:29		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	I don't think you have understood denizen's point. HTC is by default referenced to a local temperature which is another variable available for viewing in CFD-Post called "Wall Adjacent Temperature". This variable is often miles away from the reference temperature an engineer would use in the bulk flow.

January 9, 2010, 08:40		#5
andoss New Member Andi Join Date: Aug 2009 Location: Austria/Graz Posts: 5 Rep Power: 17	Thank you! This was very helpful!