FEM ConstraintHeatflux

From FreeCAD Documentation

FEM ConstraintHeatflux

Menu location
Model → Thermal boundary conditions and loads → Heat flux load
Default shortcut
Introduced in version
See also
FEM tutorial


By default, defines a convective heat flux load on a surface at a temperature with a film coefficient and with the environment (sink/ambient) temperature . The convective heat flux will satisfy: . Optionally, can also define a regular surface heat flux load.

introduced in version 1.0: Can be also used to define a radiation heat flux on a surface. It satisfies: where is the surface emissivity and is the Stefan-Boltzmann constant.


  1. There are several ways to invoke the command:
    • Press the Heat flux load button.
    • Select the Model → Thermal boundary conditions and loads → Heat flux load option from the menu.
  2. Click the Add button. In the 3D view select the face(s) on which the heat flux load should be applied. Optionally, click the Remove button to remove the selected faces from the selection list.
  3. Choose the heat flux type and specify its parameters:
    • Surface Convection (default) - convective heat flux, enter the desired Film coefficient and Ambient temperature
    • introduced in version 1.0: Surface Radiation - radiation heat flux, enter the surface Emissivity and Ambient temperature
    • Surface heat flux - general heat flux, enter the Surface heat flux in Watts per surface area (W/m^2)