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-   -   chtMultiRegionFoam, fixed convection coefficient between fluid and solid (http://www.cfd-online.com/Forums/openfoam-solving/107178-chtmultiregionfoam-fixed-convection-coefficient-between-fluid-solid.html)

romain.h September 19, 2012 14:43

chtMultiRegionFoam, fixed convection coefficient between fluid and solid
 
Hello,
I was wondering if I could use a fixed convection coefficient as a boundary condition.
Here is my simulation :
http://img15.hostingpics.net/pics/80...convection.jpg
For now, I use

solid_to_air
{
type compressible::turbulentTemperatureCoupledBaffleMix ed;
value uniform 300;
neighbourFieldName T;
K solidThermo;
KName none;
as it is done in the tutorial chtMultiRegionHeater.
}

From what I understand, with this boundary condition, the coefficient of convection h is automatically calculated from the nature of the flow.
But is it possible to impose a value ?

I tried to use fixed gradient since Q=h*S*DT (q=h*DT, thus DT=q/h), but it does not seem to work.

If I use,
solid_to_air
{
type fixedGradient:
gradient 5;
}
and
air_to_solid
{
type fixedValue:
value uniform 300;
}

the gradient does not seem to be taken between the solid and the air, but between the two walls of the solid, and since one of the side of the solid is heated, the simulation does not reach convergence.
http://img15.hostingpics.net/pics/73...mfixedGrad.jpg

When I use solid_to_air : fixed value or type compressible::turbulentTemperatureCoupledBaffleMix ed; on both solid_to_air and air_to_solid
my simulation is working.
http://img15.hostingpics.net/thumbs/...ionconverg.jpg

If it was an exterior wall, I could have use

type externalWallHeatFluxTemperature;
K solidThermo; // solidThermo or lookup
// q uniform 62500; // Heat flux / [W/m2]
Ta uniform 300.0; // Tambient temperature /[K]
h uniform 100.0; // Heat transfer coeff /[W/Km2]
value uniform 300.0; // Initial temperature / [K]
KName none;
But with this condition, Ta is fixed and does not use the value of Tair

Thanks in advance,
Romain


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