heat transfer coefficient not available in laminar

Loorsa · November 16, 2019, 07:42

Hi all,
I'm performing a simulation with Fluent and i need to compare the heat transfer coefficient with the analytical one.
In CFD-post I have a contour, on a plane placed at 0.01 mm from the wall, reporting that variable.
If i chose a turbulent model the contour works fine and the "wall heat transfer coefficient" variable appears in the list when i modify the contour, while if i chose the laminar model it doesn't appear at all.

To give some background, i'm simulating a spiralitic channel, 3mm thick and 45mm wide, with inlets and outlets perpendicular to the main faces and cylinders here and there in the channel.
The flow is mostly (70-80% i guess) laminar (analytical Re about 1000 assuming straight channels though), but goes definitely turbulent near inlet/outlets and on the cylinders trails.
The laminar model continuity does not converge (and the mesher is struggling/unable to refine the mesh on the main faces due to the high grade splines in the geometry i think), while the k-epsilon one do.
Any suggestion would be appreciated.

Thanks

LuckyTran · November 16, 2019, 12:17

Because that's the wall function heat transfer coefficient and there are no wall functions in a laminar model.

Find the regular heat transfer coefficient and plot it on the wall.

Loorsa · November 16, 2019, 14:52

Quote:

Originally Posted by LuckyTran

Because that's the wall function heat transfer coefficient and there are no wall functions in a laminar model.

Find the regular heat transfer coefficient and plot it on the wall.

Thanks for the reply.
I imagined something like this, but i'm not familiar with these models.
Since i have to hurry on this work i will ask now the following question, even though i will try to figure out and update if i succeed.
How can i do what you're suggesting? have i to select the very wall instead of a plane created with "location" in CFD-post?
In the dropdown "variable" menu, when i'm defining the contour, anything involving a heat transfer coefficient is missing.
Have i to do this in fluent and not CFD-post?

Many thanks

Loorsa · November 18, 2019, 10:23

Ok in fluent i can plot the contour of "surface heat transfer coef." on the walls between the fluid and the exchanger wall plate.
Why i'm unable to do the same on CFD-post?

November 16, 2019, 07:42	heat transfer coefficient not available in laminar	#1
Loorsa New Member Luca Join Date: Nov 2019 Posts: 5 Rep Power: 6	Hi all, I'm performing a simulation with Fluent and i need to compare the heat transfer coefficient with the analytical one. In CFD-post I have a contour, on a plane placed at 0.01 mm from the wall, reporting that variable. If i chose a turbulent model the contour works fine and the "wall heat transfer coefficient" variable appears in the list when i modify the contour, while if i chose the laminar model it doesn't appear at all. To give some background, i'm simulating a spiralitic channel, 3mm thick and 45mm wide, with inlets and outlets perpendicular to the main faces and cylinders here and there in the channel. The flow is mostly (70-80% i guess) laminar (analytical Re about 1000 assuming straight channels though), but goes definitely turbulent near inlet/outlets and on the cylinders trails. The laminar model continuity does not converge (and the mesher is struggling/unable to refine the mesh on the main faces due to the high grade splines in the geometry i think), while the k-epsilon one do. Any suggestion would be appreciated. Thanks

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November 16, 2019, 12:17		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,675 Rep Power: 66	Because that's the wall function heat transfer coefficient and there are no wall functions in a laminar model. Find the regular heat transfer coefficient and plot it on the wall.

November 18, 2019, 10:23		#4
Loorsa New Member Luca Join Date: Nov 2019 Posts: 5 Rep Power: 6	Ok in fluent i can plot the contour of "surface heat transfer coef." on the walls between the fluid and the exchanger wall plate. Why i'm unable to do the same on CFD-post?