Boundary Features

Boundary Heat Source

This node models a heat source (or heat sink) that is embedded in the boundary. When selected as a Pair Boundary Heat Source, it also prescribes that the temperature field is continuous across the pair.

Pair Selection

If this node is selected from the Pairs menu, choose the pair on which to apply this condition. A pair has to be created first. See Identity and Contact Pairs in the COMSOL Multiphysics Reference Manual for more details.

Boundary Heat Source

Click the General source (the default) or Overall heat transfer rate button.

•	For General source enter a value for the boundary heat source Qb when the default option, User defined, is selected.

A positive Qb corresponds to heating and a negative Qb corresponds to cooling. For the general boundary heat source Qb, there are predefined heat sources available when simulating heat transfer together with electrical or electromagnetic interfaces. Such sources represent, for example, ohmic heating and induction heating.

•	For Overall heat transfer rate enter the heat rate Pb. In this case Qb = Pb ⁄ A, where A is the total area of the selected boundaries.

Frame Selection

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

Source Position

To display this section, click the Show button () and select Advanced Physics Options.

Select a Source position to define a side where the heat source is defined—Layer (the default), Upside, or Downside. This setting has no effect unless the temperature differs from one side of the boundary to the other. Typically when Boundary Heat Source contributes with a Thin Layer feature.

To define the boundary heat source Qb as a function of the temperature, use the local temperature variable on the selected boundary, ht.bhs1.Tvar, that corresponds to the appropriate variable (upside, downside, or average temperature of a layer, wall temperature with turbulence modeling), depending on the model configurations.

Upside and downside settings can be visualized by plotting the global normal vector (nx, ny, nz), that always points from downside to upside. Note that the normal vector (ht.nx, ht.ny, ht.nz) may be oriented differently. See Tangent and Normal Variables.

Location in User Interface

Context menus
Heat Transfer in Solids>Boundary Heat Source
Heat Transfer in Fluids>Boundary Heat Source

Ribbon

Physics Tab with interface as Heat Transfer in Solids or Heat Transfer in Fluids selected:
Boundaries>interface>Boundary Heat Source
Pairs>interface>Pair Boundary Heat Source