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Conjugate Heat Transfer: Wall Heat Flux at Coupled Walls?

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Old   December 5, 2012, 12:55
Default Conjugate Heat Transfer: Wall Heat Flux at Coupled Walls?
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Max
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Hi everbody,

I have problems post-processing a conjugate heat transfer problem in Fluent / CFX-Post.

I set the adjecent fluid-solid walls to "interface", then created a "coupled walls"-interface. The thermal boundary-condition for the new created wall and shadow-wall where set to "coupled" aswell.

The solution works fine, I can see the solid being warmed up by the hot fluid.

I am interested in the HTCs at the solid-fluid interface wall. Since I manually calculate the HTC in Excel as

HTC = q_wall/(T_bulk(x)-T_wall(x))

, I need to export data samples for the local wall heat flux and the local wall temperature along the X-coordinate at that wall.

The problem: CFX-Post shows no value for "Wall Heat Flux" at the coupled wall interface, neither does FLUENT show values for "Total Surface heat Flux" (which is the equivalent for the CFX "Wall Heat Flux").

Does anybody know how to get the local wall heat fluxes at a coupled wall in a HTC problem?

Regards,

Max
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Old   April 16, 2013, 18:09
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Alexey Zakharov
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Hi, Max!

Do you solve this peoblem? I too recently faced with them.

And I have noted, that FLUENT Reports => Surface are given good results on coupled wall, but CFD-post do not take me value of "WallHeatFlux"!

Thanks in advance,

Alex.
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Old   April 18, 2013, 15:13
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Alexey Zakharov
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Hello!

When modeling coupled heat transfer in the program Fluent 14.5 having some difficulties.

Statement of the problem:

1. Modeled annular channel with a twisted ribbon. Heated inner wall. As an example, the test strip with very low thermal conductivity (0.001 W / m ^ 2). By using K-E model of turbulence.

2. The working area is quite complex and build her a grid exclusively through the blocks was not possible. Grid constructed in ICEM 14.5 by rotating and extruding the two-dimensional grid on the axis of rotation. Then, using the ICEM Repair Mesh => Associate Mesh with Geometry grid tied to a pre-built geometry. Thus between the ribbon and the liquid material formed one surface section.

3. After loading the prepared grid in Fluent, solver automatically shared interface into two, with, unfortunately, did not create a wall of wall-shadow, and the necessary interface coupled wall I had to ask a mesh interface. Thus was formed a few extra invisible walls.

4. The solution of the problem with the help of Fluent shows excellent results in the fields of speed, and
temperature.

And now the questions:

1. After loading the calculation results in CFD-post for some reason can not be calculated using the areaAve average heat flux on the surface of the ribs. Also, the calculation using the lengthAve average heat flux on the vertical edge of the tape is very different result from the expected zero heat flow.

Why is this happening? How can this be overcome? It was also noted that using the Reports => Surface Integrals => Area-Weigthed-Average average heat flux on the surface of the tape is true in the Fluent post.

2. Why despite the fact that it is possible to create an interface node to node, fluent not stroitwall-shadow and coupled inteface on the interface? How is it possible to correct? It seems to me to overcome this difficulty and will be the solution to my problem.

Help me!
Alexey Zakharov.
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Old   April 21, 2013, 18:22
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Alexey Zakharov
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Unfortunetly I found that it impossible(((

// User's Guide :: 0 // 7. CFD-Post File Menu // 7.15. File Types Used and Produced by CFD-Post // 7.15.10. Limitations with FLUENT Files

CFD-Post will not display any shear stress values
on coupled non-conformal interfaces as shear stresses are undefined on such interfaces.

And also wall heat flux in my experience.

Then I forced used FLUENT for postprocessing.
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