# Problem with constant Heat Flux

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 April 14, 2015, 15:27 Problem with constant Heat Flux #1 Senior Member   Hesam Join Date: Feb 2015 Posts: 139 Rep Power: 4 Hi friends, I add temprature to icofoam with openfoam wiki tutorial : https://openfoamwiki.net/index.php/H...ure_to_icoFoam and in Temprature boundary condition I define constant heat flux condition for lower wall: lowerWall { type groovyBC; valueExpression "300"; gradientExpression "q"; fractionExpression "0"; variables "q=300;"; timelines (); value uniform 300; } but when openfoam solve the problem,Temprature after 100 second become 4000-22000K!!! I'm very cunfused.please Help me Last edited by rapierrz; April 14, 2015 at 23:48.

 April 17, 2015, 11:20 #2 Senior Member   Agustín Villa Join Date: Apr 2013 Location: Brussels Posts: 187 Rep Power: 7 Hello with GroovyBC, you are imposing a gradient of temperature, not a heat flux... to do that, you should express this gradient in function of your heat flux, and the kinematic and turbulent thermal diffusivities. Other option you have is the use of turbulentHeatFluxTemperature BC.

 April 19, 2015, 00:05 #3 Senior Member   Hesam Join Date: Feb 2015 Posts: 139 Rep Power: 4 Thank you Agustin, I think When we have a fixed heat flux condition,gradient of temprature on the wall is constant. k*gradT=q , gradT=q/k; Do you think I impliment bad boundary condition with groovyBC?

 April 20, 2015, 07:30 #4 Senior Member   Agustín Villa Join Date: Apr 2013 Location: Brussels Posts: 187 Rep Power: 7 Hello, if you are using RANS models, the expression you propose should be modified to: q=k_eff*gradT where k_eff=k+k_turb, k is the thermal conductivity, and k_turb is the turbulent thermal conductivity. This expression is taken into account in the BC I told you. In case you want to use GroovyBC, you should divide by the effective thermal conductivity.

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