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. Note that in this case the source term is applied on the source side.
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.
Material Type
Select an option in the Material type list to specify if the inputs of the Boundary Heat Source section are defined in the material or spatial frame:
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The default option for the Boundary Heat Source node is Solid, which specifies that the heat source Qb is defined in the material frame. Because the heat transfer variables and equations are defined in the spatial frame, the inputs are internally converted to the spatial frame. See Conversion Between Material and Spatial Frames for details.
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The Nonsolid option defines Qb in the spatial frame. No frame conversion is needed.
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The From material option uses the option selected in the Material type list of the Material Properties section of the material applied on the domain on which the node is active.
This option has no effect when the component does not contain a moving frame because the material and spatial frames are identical in such cases. With a Deformed Geometry or a Moving Mesh interface, the heat transfer features automatically account for deformation effects of the material and spatial frames on heat transfer properties. In particular the effects of volume changes on the density are considered. See Handling Frames in Heat Transfer and Material and Spatial Frames for details.
Boundary Heat Source
Click the General source (the default) or Heat rate button.
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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.
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For Heat rate enter the heat rate Pb. In this case Qb = Pb ⁄ A, where A is the total area of the selected boundaries.
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. See Boundary Wall Temperature for a thorough description of the boundary temperature variables.
You can specify the source to be a harmonic perturbation in a frequency domain analysis. To mark the source as being a harmonic perturbation, right-click the node and choose Harmonic Perturbation. Note that this updates the node’s icon. See Theory for Harmonic Heat Transfer for more details.
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 in the COMSOL Multiphysics Reference Manual.
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Handling Frames in Heat Transfer
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About the Heat Transfer Interfaces
Evaporative Cooling of Water: Application Library path Heat_Transfer_Module/Phase_Change/evaporative_cooling
When Line Heat Flux is applied on a pair, the flux is only applied on the edge adjacent to the source boundary which is in contact with the destination boundary. Consider adding another pair with opposite source and destination boundaries to apply a flux on the edge adjacent to the destination boundary and in contact with the source boundary.
See Identity and Contact Pairs in the COMSOL Multiphysics Reference Manual for more details.
Location in User Interface
Context menus
 Heat Transfer>Boundary Heat Source
Heat Transfer in Solids>Boundary Heat Source
Heat Transfer in Fluids>Boundary Heat Source
Heat Transfer in Porous Media>Boundary Heat Source
Heat Transfer in Building Materials>Boundary Heat Source
Bioheat Transfer>Boundary Heat Source
 Heat Transfer in Solids>Pairs>Pair Boundary Heat Source
Heat Transfer in Fluids>Pairs>Pair Boundary Heat Source
Heat Transfer in Porous Media>Pairs>Pair Boundary Heat Source
Heat Transfer in Building Materials>Pairs>Pair Boundary Heat Source
Bioheat Transfer>Pairs>Pair Boundary Heat Source
Ribbon
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 or Bioheat Transfer selected:
Boundaries>interface>Boundary Heat Source
Pairs>interface>Pair Boundary Heat Source