# problem with constant wall heat flux

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 February 4, 2010, 07:46 problem with constant wall heat flux #1 Member   Join Date: Dec 2009 Posts: 46 Rep Power: 16 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 .. luiscardona, murrdpirate, elham-u and 2 others like this.

 February 4, 2010, 09:46 #2 Senior Member   Stefan Herbert Join Date: Dec 2009 Location: Darmstadt, Germany Posts: 129 Rep Power: 17 Hi, this is the right way. Go on like this. Regards Stefan

 June 23, 2014, 14:23 #3 New Member   Ian Dizon Join Date: May 2014 Posts: 6 Rep Power: 12 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

 June 24, 2014, 03:07 #4 New Member   Bárbara Arizmendi Join Date: Oct 2013 Location: Spain Posts: 14 Rep Power: 12 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. Last edited by Barbara; June 24, 2014 at 03:08. Reason: lexical mistake

 July 16, 2014, 08:30 multiregion solid conduction #5 Member   Anastasios Join Date: Mar 2009 Posts: 34 Rep Power: 17 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.

 August 15, 2016, 16:20 heat flux setting #6 New Member   alaa Join Date: Aug 2016 Posts: 1 Rep Power: 0 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

 January 13, 2019, 08:18 #7 Senior Member   Jianrui Zeng Join Date: May 2018 Location: China Posts: 157 Rep Power: 8 If I use fixedGradient BC for constant heat flux, should thermo conductivity be constant? if it is changing with T, how should I get constant heat flux? Thank you.