Boundary Heat Source

This node models a heat source (or heat sink) that is embedded in the boundary. When selected as a , 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 menu, choose the pair to apply this condition to. A pair must be created first. See Identity and Contact Pairs in the COMSOL Multiphysics Reference Manual for more details.

Material Type

Select an option in the list to specify if the inputs of the section are defined in the material or spatial frame:

•

The default option for the node is , 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.

•

The option defines Qb in the spatial frame. No frame conversion is needed.

•

The option uses the option selected in the list of the 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 take into account 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

Select an option from the list:

•

For (default) enter a value for the boundary heat source Qb when the default option, , 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


	When User defined is selected for General source, if the expression contains a variable that is discontinuous across that boundary (a thin resistive layer, for example), its value is the average of the value on the “up” and “down” sides of the boundary. You can use the up and down operators to get the value on either side of the boundary (see up and down).

•

For 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 button (

) and select .

Select a to define a side where the heat source is defined: (default), , or . This setting has no effect unless the temperature differs from one side of the boundary to the other. Typically when contributes with a feature.

Continuity

If this node is selected from the menu, select the check box to prescribe that the temperature field is continuous across the pair where the source and destination boundaries match. The continuity on a pair should be set from a single feature. It may also be set by a or another pair feature.

When the option is selected, the heat source Qb is applied on the source or on the destination or on both depending on the selected option in . When the check box is selected in this feature (the status in other features has no effect) and is set to , Qb ⁄ 2 is applied on the source and on the destination.

When the option is selected, the heat rate is distributed on the source or on the destination or on both depending on the selected option in . In this case, the integral of the applied heat source is equal to the heat rate.


	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.

•

Handling Frames in Heat Transfer

•

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

Ribbon

Physics tab with interface as , or any version of the Heat Transfer interface selected:

Physics tab with or selected in the model tree: