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-   -   Shadow Wall and temperature (http://www.cfd-online.com/Forums/fluent/104937-shadow-wall-temperature.html)

norger July 19, 2012 02:47

Shadow Wall and temperature
 
Hey,

I have two bodies in a room with air. One body has on one specific surface a defined temperature and I want to see how the temperature influences the two bodies and the air in the room.

My question is how I rightly set the boundary conditions for the shadow walls?

I read some things about the setting "coupled" but I can not use it for the surface with the defined temperature because by using "coupled", I can not set the temperature.

My idea:
I set the surface with the temperature and its shadow wall to a wall with the same defined constant temperature and not "coupled".
The air in the room gets a starting temperature.
The other bodies and their shadow walls are defined as "coupled".
Is that correct?

Is the temperature at the coupled walls set as a zero-point and, therefore do I have to use the temperature difference from 0 K to my defined temperature?

Thank you very much in advance for your answers

flotus1 July 19, 2012 03:07

If you model the Fluid (the air inside the room) and the solid bodies together, things are a bit different.

The wall between the solid body and the fluid acts as an interface. If you want them to exchange heat, the coupled option is indeed the right choice.
Now the temperature would have to be set in the solid domain if you want the wall to remain at a constant temperature.

norger July 19, 2012 03:45

Ok, so I have to set a temperature at: Cell Zone Boundaries -> Fixed Values -> constant Temperature.

But what could I do if my wall will not have a volume? The temperature is just at a surface on the body.

flotus1 July 19, 2012 04:00

You mean if there is no solid volume on the other side of the wall, but the wall is just a boundary for the fluid phase?
There shouldn't even be a shadow wall.

In this case, you don't need an interface. Just set the boundary type to wall and set the temperature value.

norger July 19, 2012 04:07

There is a shadow wall because this surface with the defined temperature is on the solid body and, therefore, it is between the fluid and the solid. It is just a surface and has no volume.

mactech001 January 17, 2013 22:29

Dear Flotus1,

I've a simple model which consist of 2 bodies: aluminum body and fluid body which is fluid.

from Workbench, i've created 2 Named Selections which FLUENT has read in:
pipe2fluid: the face on the pipe which interfaces with the fluid
fluid2pipe: the face on the fluid which interfaces with the pipe

In Fluent, under 'Boundary Conditions' i've defined the above Named Selections as type= 'interface', Then, in 'Mesh Interfaces', i've created fluidpipe having
Interface Zone 1 = fluid2pipe
Interface Zone 2 = pipe2fluid
Selected 'Coupled Wall', which then Fluent automatically creates the corresponding walls and shadow-walls:
Boundary Zone 1 = wall-14
Boundary Zone 2 = wall-15
Interface Wall Zone 1 = wall-7
Interface Wall Zone 2 = wall-7-shadow
Interface Interior Zone has nothing defined

WHen i go to the 'Boundary Conditions' section, and view the properties of created walls, i find that:
wall-14: Adjacent cell zone=fluid, Material Name=aluminum
wall-15: adjacent cell zone=pipe, Material Name=aluminum
wall-7: adjacent cell zone=fluid, shadow face zone=wall-7-shadow, material name=aluminum
wall-7-shadow: adjacent cell zone=pipe, shadow face zone=wall-7, material name=aluminum

My enquiries are:
1) in the 'Boundary Conditions' section where wall-14 and wall-7 have Adjacent Zone=fluid, why is MAterial name=aluminum and i can't change to the material name for fluid?
2) should i bother changing the Material name for fluid please?

Grandup April 22, 2016 09:08

hello , i face same probleme here
solution please ?

Grandup April 22, 2016 09:09

hello , i face same probleme here
solution please ?

LuckyTran April 22, 2016 10:51

The default material name in the wall is aluminum.

The material is used for modelling shell conduction at a wall, or for modelling wall thermal resistance. There is also a wall thickness (the default thickness is 0 m). The wall material plays no role in the hydrodynamics (only the heat transfer) and in the case where the thickness is 0, there is no influence on the heat transfer because the shell conduction model is not invoked.


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