Use this node to add heat flux across boundaries. A positive heat flux adds heat to the domain. This feature is not applicable to inlet boundaries, use the Inflow Heat Flux condition instead.

Click to select the General inward heat flux (the default), Convective heat flux, or Heat rate button.

It adds q0 to the total flux across the selected boundaries. Enter a value for q0 to represent a heat flux that enters the domain. For example, any electric heater is well represented by this condition, and its geometry can be omitted.

The default option is to enter a User defined value for the Heat transfer coefficient h. In addition, the following options are also available to control the type of convective heat flux to model: External natural convection, Internal natural convection, External forced convection, or Internal forced convection.

For all options except User defined, select a Fluid: Air (the default), Transformer oil, or Water.

For Air, also set the Absolute pressure, pA. For User Defined, enter a value or expression. The default is 1 atm. Else, select an Ambient absolute pressure defined in the Ambient Settings section of a Heat Transfer or Heat Transfer in Shells interface.

Depending of the selected option, different parameters are needed. You can refer to the Sketch section to get an illustration of the configuration.

For External natural convection select Vertical wall, Inclined wall, Horizontal plate, upside, Horizontal plate, downside, Long horizontal cylinder, Sphere, or Vertical Thin Cylinder from the list under Heat transfer coefficient. Then enter the applicable information:

For Internal natural convection select Narrow chimney, parallel plates or Narrow chimney, circular tube from the list under Heat transfer coefficient. Then enter the applicable information:

For External forced convection select Plate, averaged transfer coefficient, Plate, local transfer coefficient, Cylinder in cross flow, or Sphere from the list under Heat transfer coefficient. Then enter the applicable information:

For Internal forced convection the only option is Isothermal tube. Enter a Tube diameter D and a Velocity, fluid U.

If Velocity, fluid U is User defined, enter a value or expression. Else, select a Wind velocity defined in the Ambient Settings section of a Heat Transfer or Heat Transfer in Shells interface.

Finally, enter an External temperature, Text. The value depends on the geometry and the ambient flow conditions. Convective heat flux is defined by q0 = h(Text − T).

For User defined, enter a value or expression. Else, select an Ambient temperature defined in the Ambient Settings section of a Heat Transfer or Heat Transfer in Shells interface.

For Heat rate enter the heat rate P0 across the boundaries where the Heat Flux node is active. In this case q0 = P0 ⁄ A, where A is the total area of the selected boundaries.

The settings are the same as for the Heat Source node and are described under Frame Selection.

Physics Tab with interface as Heat Transfer, Heat Transfer in Solids, Heat Transfer in Fluids, Heat Transfer in Porous Media, Heat Transfer in Building Materials, Bioheat Transfer, Heat Transfer with Surface-to-Surface Radiation or Heat Transfer with Radiation in Participating Media selected:
Boundaries>interface>Heat Flux