CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   OpenFOAM Running, Solving & CFD (http://www.cfd-online.com/Forums/openfoam-solving/)
-   -   externalWallHeatFluxTemperature in turbulence models (http://www.cfd-online.com/Forums/openfoam-solving/103802-externalwallheatfluxtemperature-turbulence-models.html)

irw June 27, 2012 06:40

externalWallHeatFluxTemperature in turbulence models
 
I wish to apply a nonuniform heat-transfer-coefficient boundary coefficient to a wall. I have used the following boundary condition for temperature:

my-boundary
{
type externalWallHeatFluxTemperature;
K basicThermo;
KName none;
Ta 300;
value 300;
gradient 0;
h nonuniform List<scalar>
....
}

If I specify 'h' with units [W/m2/K] I get far too much heat leaving the boundary.

I'm having trouble following the units through externalWallHeatFluxTemperatureFvPatchScalarField. C

00210 q = (Ta_ - *this)*h_;

I think this implies [q] = [K - K]*[W/m2/K] = [W/m2].

Then...

00224 if (q[i] > 0) //in
00225 {
00226 this->refGrad()[i] = q[i]/K(*this)()[i];
00227 this->refValue()[i] = 0.0;
00228 this->valueFraction()[i] = 0.0;
00229 }
00230 else //out
00231 {
00232 this->refGrad()[i] = 0.0;
00233 this->refValue()[i] = KDelta[i]*q[i] + patchInternalField()()[i];00234 this->valueFraction()[i] = 1.0;
00235 }

For the heat input case, I see [refGrad]=[W/m2] / [W/m/K] = [K/m], which is good.

For the heat output case, I think the units of kDelta are [W/m/K]*[1/m]=[W/m2/K] based on mesh.surfaceInterpolation.c and
00202 scalarField KDelta(K(*this)*patch().deltaCoeffs());

Doesn't this imply the units of refValue are [refValue] = [W/m2/K] * [W/m/K] + [K] ?

Is this a bug or have I mis-understood something?

Thanks,
irw

gruenertee July 20, 2013 05:29

Hi foamers,

first i want to say that i am interested in getting the problem solved from the first post "If I specify 'h' with units [W/m2/K] I get far too much heat leaving the boundary" too. Can anyone explain the question from the first post?

My question deals with the problem how to read out data for Ta from a .dat file; is it in general possible?

type externalWallHeatFluxTemperature;
K solidThermo; // solidThermo or lookup
q uniform 1000; // Heat flux / [W/m2]
Ta uniform 300.0; // Tambient temperature /[K]
h uniform 10.0; // Heat transfer coeff /[W/Km2]
value uniform 300.0; // Initial temperature / [K]
KName none;

Can i combine this type with:


{

type uniformFixedValue;
uniformValue tableFile;
tableFileCoeffs
{
fileName "inlet.dat";
outOfBounds warn;
}
}

Thank you very much!


All times are GMT -4. The time now is 05:36.