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Conjugate Heat Transfer from reacting fluid to Catalyst Wall

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Old   July 16, 2013, 09:54
Default Conjugate Heat Transfer from reacting fluid to Catalyst Wall
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Hey guys I'm new to the CFD and I am desperate simulating the heat-transfer in a catalyst.
Hope someone can help me out!
I would be the happiest ingeneer of the world.

So heres the problem:

I am doing a project on the partial oxidation of Methan in a Rhodium Catalyst in order to create syngas. The Gas-flow inserts with a velocity of 0.072m/s and a temperature of 873K and a certain fixed mole-fraction.

So I created the Geometry Mesh and everything. I took the surface remesher and trimmer. Started with about 400.000 cells to begin with. The catalyst is 11mm long and I am only calculating one channel and 8 partially sliced channels.

In the beginning I set the Catalyst wall to a constant temperature. (973 K) Imported CHEMKIN Files with 38 Reactions.
Used the following physic models:

-DARS-Cfd ideal Gas
-DARS-Cfd reaction
-Gradients
-Homogeneous reactor with surface chemistry
-Laminar
-Laminar flame concept
-Multi Component gas
-Operator Splitting (set to 51 Iterations)
-Premixed combustion
-Reacting
-Segregated flow
-Segregated Fluid Enthalpy
-Segregated species
-Steady
-Surface chemistry
-Three-Dimensional

Set the Initial Conditions to u=0.72, Mole fraction N2= 0.8005, O2=0.0665, CH4=0.133, Pressure 0.0 Bar, Static Temp. 873K.
Reference pressure 101300Pa.

I ran the simulation and everything worked out totally fine. I got excellent results.

But now as I wanted to include the heat transfer through the walls of the Catalyst I am getting nonsense results.

Here is what i did:

I created an Interface (in-place, contact interface boundary) , and another physics contium.

Models:

-constant density
-gradients
-segregated solid energy
-solid: I took Al, though i really have an Rh-coated monolith. I fed the program with the proper density and other data so i thought that is ok. Is it?
-steady
-three dimensional

As initial Conditions under the Physics node of the solid catalyst i put for the Temperature 873 K, since the reaction is only starting from a certain temperature level.

I changed the Fluid Region Physic Conditions for the boundary of fluid and Catalyst from "temperature" to "adiabatic".

I changed under the newly created Interface Boundary in the Fluid Region node the Surface mechanism option from "None" to "Catalyst" like it is set in the boundary of Fluid and Catalyst.

Under the Solid Region node I put under the boundary node of fluid and solid for the thermal specification "adiabatic".

Running the Simulation it gives me Outlet Velocities of 0 m/s and temperatures of 0 K.

Under the Interface node I put for the Energy Source option "none".


I know i might not have explained my problem and the adjustment of the program too exactly for you to be able to find the fault i did.

Anyways i wanna thank you guys for even trying to help me out since I am really stuck here and dont know what to do.

Thanks alot!!!
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Old   July 16, 2013, 15:57
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It's hard to say without looking at your model, but interfaces can cause problems by taking over the boundary types. If the inlet or outlet have an interface attached to the boundary, then you won't have any flow. If this isn't an issue, put up a screen shot of the model.
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Old   July 17, 2013, 09:45
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Hello Kasey,

Thank you for your quick response.

I dont have a interface connected to the inlet or outlet.
I have an picture attached to display my model.
I defined my interface only where the Catalyst and the Fluid are in contact.
The Catalyst Body is therefore devided in an interface and a symmetry plane.
The inlet is placed on the right side of the object in the pictures and the pressure outlet on the left side.
The fluid enters the Catalyst after 5mm in order to not have turbulances etc.

Hope the pictures help.

Regards

Fritz
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File Type: jpg Bildschirmfoto1.jpg (81.3 KB, 7 views)
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catalyst, conjugate heat transfer, cpox, reacting flow

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