The externalWallHeatFluxTemperature is a boundary condition that applies a heat flux condition to temperature on an external wall in one of three modes:

  • fixed power: supply Q
  • fixed heat flux: supply q
  • fixed heat transfer coefficient: supply h and Ta


Property Description
Q Power [W]
q Heat flux [W/m^2]
h Heat transfer coefficient [W/m^2/K]
Ta Ambient temperature [K]

For heat transfer coefficient mode optional thin thermal layer resistances can be specified through thicknessLayers and kappaLayers entries.

The thermal conductivity kappa can either be retrieved from various possible sources, as detailed in the class temperatureCoupledBase.


The condition requires entries in both the boundary and field files.

Boundary file

    type            patch;

Field file

    // Mandatory entries
    type            externalWallHeatFluxTemperature;
    mode            <word>;

    // Optional entries
    relaxation      <scalar>;
    emissivity      <scalar>;
    qrRelaxation    <scalar>;
    qr              <word>;

    // Conditional entries

        // if mode==power
        Q           <Function1<scalar>>;

        // if mode==flux
        q           <PatchFunction1<scalar>>;

        // if mode==coefficient
        h           <PatchFunction1<scalar>>;
        Ta          <Function1<scalar>>;
        thicknessLayers <scalarField>;
        kappaLayers <scalarField>;

        // if qr!=none
        qrPrevious  <scalarField>;

    // Inherited entries


Property Description Type Required Default
type Type name: externalWallHeatFluxTemperature word yes -
mode Operation mode word yes -
relaxation Relaxation factor for wall temperature scalar no 1.0
emissivity Surface emissivity for radiative flux scalar no 0.0
qrRelaxation Relaxation factor for radiative field scalar no 1.0
qr Name of radiative field word no none
Q Heat power [W] Function1<scalar> conditional -
q Heat flux [W/m^2] PatchFunction1<scalar> conditional -
h Heat transfer coeff [W/m^2/K] PatchFunction1<scalar> conditional -
Ta Ambient temperature [K] PatchFunction1<scalar> conditional -
qrPrevious Cached field for qr relaxation scalarField conditional -

The inherited entries are elaborated in:

  • mixedFvPatchFields.H
  • temperatureCoupledBase.H
  • PatchFunction1.H

Further information


Source code:



  • Introduced in version 2206