Adding constant heat flux along the boundary of fluid channel

Ghada · February 16, 2018, 19:06

Hello everybody!

So I'm trying to simulate the water sub-channel between the fuel rods in the spent fuel pool of a nuclear reactor.

The question is that how can I add a constant heat flux along the boundary wall of the channel and not only at the center of it?

ghorrocks · February 17, 2018, 06:32

If you use a heat flux boundary condition on a wall boundary it gets applied evenly over the entire boundary by default.

But the temperature for this type of heat flux on a wall boundary will probably have a hot patch in the middle and cooler patches on the edges. Is this what you mean?

Ghada · February 17, 2018, 06:39

Yes exactly!
So I can't have a constant flux along the boundary? only constant temperatures?

ghorrocks · February 17, 2018, 06:44

You can define a wall boundary to have constant heat flux or constant temperature.

Make sure you know the difference between heat flux and temperature: a constant heat flux will give you a hot bit in the middle, and constant temperature will mean the heat flux will be reduced in the middle.

Ghada · February 17, 2018, 06:55

Okay got it .

So can I, by any means, make the flux constant long the wall boundary from the bottom to the top of the channel (assume the channel is vertical)?
Because in my case, there is a heat flux generated from the fuel to the water all the way long..

Ghada · February 17, 2018, 07:26

Actually I'm looking for a "uniform" heat flux..can you help me?

ghorrocks · February 17, 2018, 18:41

So then use a wall heat flux condition for the thermal model on the wall boundary. The default is a specified temperature. It is just a different option on the GUI, nothing difficult.

Ghada · February 19, 2018, 17:36

It worked very well! Thank you very much.

February 16, 2018, 19:06	Adding constant heat flux along the boundary of fluid channel	#1
Ghada New Member Ghada Join Date: Feb 2018 Posts: 8 Rep Power: 8	Hello everybody! So I'm trying to simulate the water sub-channel between the fuel rods in the spent fuel pool of a nuclear reactor. The question is that how can I add a constant heat flux along the boundary wall of the channel and not only at the center of it?

February 17, 2018, 06:32		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	If you use a heat flux boundary condition on a wall boundary it gets applied evenly over the entire boundary by default. But the temperature for this type of heat flux on a wall boundary will probably have a hot patch in the middle and cooler patches on the edges. Is this what you mean? __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

February 17, 2018, 06:44		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	You can define a wall boundary to have constant heat flux or constant temperature. Make sure you know the difference between heat flux and temperature: a constant heat flux will give you a hot bit in the middle, and constant temperature will mean the heat flux will be reduced in the middle. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

February 17, 2018, 18:41		#7
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	So then use a wall heat flux condition for the thermal model on the wall boundary. The default is a specified temperature. It is just a different option on the GUI, nothing difficult. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

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February 17, 2018, 06:39		#3
Ghada New Member Ghada Join Date: Feb 2018 Posts: 8 Rep Power: 8	Yes exactly! So I can't have a constant flux along the boundary? only constant temperatures?

February 17, 2018, 06:55		#5
Ghada New Member Ghada Join Date: Feb 2018 Posts: 8 Rep Power: 8	Okay got it . So can I, by any means, make the flux constant long the wall boundary from the bottom to the top of the channel (assume the channel is vertical)? Because in my case, there is a heat flux generated from the fuel to the water all the way long..

February 17, 2018, 07:26		#6
Ghada New Member Ghada Join Date: Feb 2018 Posts: 8 Rep Power: 8	Actually I'm looking for a "uniform" heat flux..can you help me?

February 19, 2018, 17:36		#8
Ghada New Member Ghada Join Date: Feb 2018 Posts: 8 Rep Power: 8	It worked very well! Thank you very much.