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-   -   problem with constant wall heat flux (http://www.cfd-online.com/Forums/openfoam/72396-problem-constant-wall-heat-flux.html)

openfoam1 February 4, 2010 08:46

problem with constant wall heat flux
 
hi foamers

i want to use a fixed heat flux boundary condition in a conjugate heat transfer problem i use fixedGradient boundary condition on T ;

bottom
{
type fixedGradient;
gradient uniform 10.417;
}

i know that

heatflux = thermal conductivity (k) * tempreature gradient (dT/dN)

so for k=12 , heatflux=125 w/m2 >> gradient=heatflux/k=10.417

please help me ,, is that right to describe my constant heat flux (125 w/m2) in OpenFOAM ..

thank you very much ..

herbert February 4, 2010 10:46

Hi,

this is the right way. Go on like this. ;)

Regards
Stefan

superian June 23, 2014 14:23

hello, i am trying to set up something similar where i have a constant heat flux.
in my case i have lamps heating up air in a room.

my question is: would k be a property of the air? or of the lamp

Barbara June 24, 2014 03:07

It depends on where you are fixing the heat flux. If you have simulated the lamp then you use the conductivity of the lamp. If you haven't simulated the lamp then you have to calculate the convective heat transfer coefficient (hc) or you can fix a HeatFlux boundary condition.

ageorg July 16, 2014 08:30

multiregion solid conduction
 
Hi

I am also trying to do something similar and the option to fix the Gradient of T works fine but only if you have solids with the same k (thermal conductivity). If there are different domains with different k's the results are not as expected comparing with COMSOL or FLUENT applying the actual heat flux boundary value.

Has anyone dealt with something like this in ChtMultiRegionFoam if yes any advice would be really helpful!!!

Thanks in advance

T.

alaa88 August 15, 2016 16:20

heat flux setting
 
Hi


I have case that their is constant heat flux from ground and i put it 500 w/m2

but their is a problem that it is not effect the density of the air or it's velocity

during solving and after calculation

please help


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