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Radiation heat transfer with P1 and chtMultiRegionFoam 

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February 14, 2019, 13:14 
Radiation heat transfer with P1 and chtMultiRegionFoam

#1 
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Eliot
Join Date: Aug 2018
Posts: 3
Rep Power: 4 
Hello everybody !
I am having trouble calculating radiation heat transfer with the P1 model, here is my case. Numerical configuration I am currently trying to model a problem of conjugate heat transfer between a hot air jet and an opaque solid plate on openFoam4.1. This problem involves thermal conduction in the solid, convective heat transfer and radiation thus chtMultiRegionFoam seems to be a good choice. The case is very similar to the following threads: chtMultiRegionSimpleFoam: Thermal Conduction + SurfaceToSurface Radiation and Lack of knowledge simulating radiation in solids The following threads gives information concerning the calculation of G and Qr: Difference between IDefault and G (radiation) Fluid/solid thermal coupling The coupling between the fluid and the solid regions is made using a compressible::turbulentTemperatureRadCoupledMixed boundary condition as follows. Code:
//location "0/solid"; //object T; solid_to_fluid { type compressible::turbulentTemperatureRadCoupledMixed; Tnbr T; kappaMethod fluidThermo; QrNbr none; Qr Qr; value $internalField; } Code:
//location "0/fluid"; //object T; fluid_to_solid { type compressible::turbulentTemperatureRadCoupledMixed; Tnbr T; kappaMethod fluidThermo; QrNbr Qr; Qr none; value $internalField; } For the radiative heat transfer, the fluid is considered a nonparticipating media and the solid is an opaque solid with a surface emissivity equal to 1. Code:
//location "0/fluid"; //object G; fluid_to_solid { type MarshakRadiation; emissivityMode solidRadiation; value uniform 0; } Code:
//location "0/fluid"; //object Qr; fluid_to_solid { type MarshakRadiation; T T; value uniform 0; } Code:
//location "0/solid"; //object G; solid_to_fluid { type MarshakRadiation; emissivityMode solidRadiation; value uniform 0; } Code:
//location "0/fluid"; //object Qr; solid_to_fluid { type mappedField; sampleRegion fluid; sampleMode nearestPatchFace; samplePatch solid_to_fluid; offset (0 0 0); field Qr; setAverage no; average 0; value uniform 0; } Code:
//location "constant/fluid"; //object radiationProperties; radiation on; radiationModel P1; solverFreq 3; absorptionEmissionModel constantAbsorptionEmission; constantAbsorptionEmissionCoeffs { absorptivity absorptivity [ m^1 ] 0; emissivity emissivity [ m^1 ] 0; E E [ kg m^1 s^3 ] 0; } scatterModel none; sootModel none; Code:
//location "constant/solid"; //object radiationProperties;; Radiation on; radiationModel opaqueSolid; solverFreq 3; absorptionEmissionModel constantAbsorptionEmission; constantAbsorptionEmissionCoeffs { absorptivity absorptivity [ 0 1 0 0 0 0 0 ] 0; //opaqueSolid emissivity emissivity [ 0 1 0 0 0 0 0 ] 1; E E [ 1 1 3 0 0 0 0 ] 0; } scatterModel none; sootModel none; With this particular setting, I expect the radiative flux Qr at the solid/fluid interface to be Qr= QinQem where Qem = emissivity*Sigma*T⁴ Qin=0 as absorptivity=0 However the result is different: for T=850 K > Qr=58055.75 Qr should be emissivity*Sigma*T⁴= 29600 So there is a factor 2 between the theoretical radiativ heat flux and the Qr field. Is there a problem in the definition of the boundary condition and radiationProperties or have I misunderstood the definition of Qr? Question 2 As the P1 model seems to be less accurate than fvDOM for exemple, is it possible this large difference between theoretical and numerical radiation flux is due to the model ? Question 3 I have doubt about the setting of my "0/fluid/Qr" boundary condition with "mappedField". Is it necessary for the calculation of the radiative heat transfer and if yes, is it writen in a proper way ? I would really appreciate if someone could help me with this problem. Many thanks in advance. Regards, Eliot 

February 17, 2019, 16:31 

#2 
Senior Member
Domenico Lahaye
Join Date: Dec 2013
Posts: 110
Rep Power: 8 
My humble suggestion would be to check the continuity of the heat flux first.
Cheers, Domenico. 

December 17, 2019, 18:27 

#3 
New Member
Dániel Bakonyi
Join Date: Dec 2019
Location: Budapest, Hungary
Posts: 2
Rep Power: 0 
Hello EliotSch,
I know it has been quite a while, but have you found asolution for your problem? I am currently facing what seems to be the exact same issue. Regards, Daniel Edit: I am sorry, I accidentally posted to the wrong thread. Please disregard this post. Last edited by Daniel Bakonyi; December 17, 2019 at 20:26. 

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