Wall Shadow condition???
 

Dear friends, I am doing an analysis of cooling in ducts. In this I have an rect shaped duct which is an solid (aluminum) material maintained at 40 deg cel. Inside that air flowing at an temp of 23 deg cel. I have modeled this when I exported to fluent. It shows some wall shadow created near that solid region. So pls can any one tell me what conditions should I give for this shadow. Pls give ur comments. Thanks for ur time. With reg, Shanthi

Re: Wall Shadow condition???
 

Hi Shanthi

Fluent has two options to solve the conduction for solid materials

1) By modelling the Thickness and meshing it as solid part

2) By Shell conduction i.e. in shell conduction you can specify the thickness to the zero thickness wall.

Now fluent whereevr it finds wall it creates a shadow. If your are modelling with the first approach do not specify any thermal b.c. leave it as it is. If you are modelling by second approach look for adjacent zone and accordingly specify the b.c for emissivity and convection ....

it depends on the case modelled as i don't knw how you have modelled .......

Hope this reply useful.

Re: Wall Shadow condition???
 

Hi uday,

First of all thanks for ur reply and ur time. But still i have some doubts regarding this, so pls if u dont mind can u give me ur mail id. So that i will upload the picture of my model and few deails about that to clarify my doubts. So that i will be gratefull to u.

Regards, Shanthi

Re: Wall Shadow condition???
 

Hello

Use default values to the wall shadow region and assign the same material.

two seperate domain for solid and fluid
 

friends, i created two domain for solid and fluid with tetra mesh and saved separately. i imported both the files into fluent 6.3, wall and wall .1 was created automatically for solid and fluid domain respectively.

some face of the fluid domain and solid domain do not have contact between them in my model.

in boundary condition i chosen interface for wall and wall .1.

then in define gird interface i created the interface using this wall and wall .1. and coupled.

is this correct procedure?

"some face of the fluid domain and solid domain do not have contact between them in my model" weather this needs any other procedure to define it?

thanks

hi shanthi,

when two volumes have a face in common fluent creates the face as face and face shadow ... so if u want the heat transfer be there between the volumes which share this common face then the boundary condition should be coupled.. also if u have any volumetric heat generation at the common face ( say like heat dissipated from a PCB or some chemical reaction ) then specify the volumetric heat generation in w/m^3.
but i dont think in ur problem there is any such thing so keep the default values and just make sure that the face and face shadow are coupled..

When you have a volume inside other volume, the Fluent put this condition of shadow. It don't difficult the convergence.