CFD Online Discussion Forums - chtMultiregionFoam issues with heat sources

Hi everyone!

I'm in desperate need of help!

I set up a case in which a cylindrical heating element 2 cm in diameter and 4 cm long is heated with a power of 404 W and irradiates the surroundings.

The heater is surrounded by vacuum (modeled as air with very low kappa and cp, frozen flow), and everything is enclosed in a reradiating furnace wall, except that two stripes of this wall are actually held at 600K and so absorb all the exceding heat.

I used fvDOM as radiation model.

The analytical calculation shows that the heater, which is made of silicon carbide, should heat up at a rate of 52 K/s, while calculation with cht shows a heating of only 8K/s, which is much lower.

The setup can be seen in the image I attached (PS there is a mesh in between the heater and the external wall)

I'll post here the configuration files related to the heating element:

Code:

/*--------------------------------*- C++ -*----------------------------------*\

  =========                 |

  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox

   \\    /   O peration     | Website:  https://openfoam.org

    \\  /    A nd           | Version:  7

     \\/     M anipulation  |

\*---------------------------------------------------------------------------*/

FoamFile

{

    version     2.0;

    format      ascii;

    class       dictionary;

    location    "constant/heater";

    object      fvOptions;

}

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

heatSource 

{ 

    type            scalarSemiImplicitSource; 

    active          true;  

    scalarSemiImplicitSourceCoeffs 

    { 

                selectionMode       all;

        volumeMode              absolute; //specific;//absolute; 

        injectionRateSuSp 

        { 

                        rho (3200 0); //TODO: is this required?

            h (404 0); //TODO: 404 W is this the right unit?

                }

        }

}

//************************************************************************* //

Here I set up a heat source for the heating element

Code:

/*--------------------------------*- C++ -*----------------------------------*\

  =========                 |

  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox

   \\    /   O peration     | Website:  https://openfoam.org

    \\  /    A nd           | Version:  7

     \\/     M anipulation  |

\*---------------------------------------------------------------------------*/

FoamFile

{

    version     2.0;

    format      ascii;

    class       dictionary;

    location    "constant/solid";

    object      thermophysicalProperties;

}

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //



thermoType

{

    type            heSolidThermo;

    mixture         pureMixture;

    transport       constIso;

    thermo          hConst;

    equationOfState rhoConst;

    specie          specie;

    energy          sensibleEnthalpy; //sensibleEnthalpy;

}



mixture

{

    // Silicon carbide



    specie

    {

        molWeight       1000;                

    }

    equationOfState

    {

        rho             3200;//3200; //g/cm2                

    }

    transport

    {

        kappa           120;//120; //W/cm*K        

    }

    thermodynamics

    {

        Hf              0;

        Cp              190;        //J/(g*K)        

    }

}



// ************************************************************************* //

And here are the thermophysical properties of the heating element.

Code:

/*--------------------------------*- C++ -*----------------------------------*\

  =========                 |

  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox

   \\    /   O peration     | Website:  https://openfoam.org

    \\  /    A nd           | Version:  7

     \\/     M anipulation  |

\*---------------------------------------------------------------------------*/

FoamFile

{

    version     2.0;

    format      ascii;

    class       volScalarField;

    location    "0/solid";

    object      T;

}

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //



dimensions      [ 0 0 0 1 0 0 0 ];



internalField   uniform 300;



boundaryField

{

    #includeEtc "caseDicts/setConstraintTypes"



    front_cyc

    {

        type            cyclic;

    }



    back_cyc

    {

        type            cyclic;

    }



    heater_to_air

    {

        type            compressible::turbulentTemperatureRadCoupledMixed;

        value           uniform 300;

        Tnbr            T;

                T                                T;

        kappaMethod     solidThermo;

        qrNbr           qr;

        qr              none;

/*                type                        zeroGradient;*/

    }

}





// ************************************************************************* //

Last but not least the boundary condition file that couples temperature in this solid to radiation in the neighbour solid.

the whole case can be found here:
https://drive.google.com/open?id=1xi...5dn-LkhGKw7QKl

Any idea of what could be causing this issue? Wrong unit in the thermophysical properties? Wrong injection of heat?

Please help! :eek: