Surface-to-Ambient Radiation, Interface (Heat Transfer in Shells Interface)
Use this node to add surface-to-ambient radiation on the exterior interfaces of a shell and, for the case of a layered shell, at the interfaces between its layers. The net inward heat flux due to surface-to-ambient radiation is
where ε is the surface emissivity, σ is the Stefan-Boltzmann constant (a predefined physical constant), and Tamb is the ambient temperature.
Interface Selection
Set the interfaces for which surface-to-surface radiation should be considered. These can be internal interfaces between layers or the top and bottom surfaces. Select the applicable layers (the default setting is All layered materials) in the Layered Material list. If no layered materials have been included yet, there is a shorthand available for creating a Single Layer Material, a Layered Material Link, or a Layered Material Stack (the plus, next to the Layer Selection setting).
For a Single Layer Material, the surface-to-surface radiation is modeled on both sides by default. Unselect the Downside and Upside check boxes for another behavior. This setting has no effect unless the temperature differs from one side of the boundary to the other.
When a layered material stack or link is selected from the Layered Material list, unselect the check boxes corresponding to layer interfaces where the node should not be applied in the Selection table.
You can visualize the selected interfaces by clicking the Layer cross section preview and Layer 3D preview buttons.
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For a general description of layer and interface selections, see The Layer Selection and Interface Selection Sections.
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You can provide material parameters with a through-thickness variation by explicitly or implicitly using expressions containing the extra dimension coordinate as described in Using the Extra Dimension Coordinates.
The desired selection for the node may correspond to boundaries with different layered materials. The All layered materials option allows to gather these materials to make the desired selection applicable for the node on the union of the boundaries where the layered materials are defined.
See Layered Material, Layered Material Link, Layered Material Stack, Layered Material Link (Subnode), and Single Layer Material in the COMSOL Multiphysics Reference Manual.
Model Input
This section has fields and values that are inputs to expressions that define material properties. If such user-defined property groups are added, the model inputs appear here.
Temperature
This section is available when temperature-dependent material properties are used. By default the temperature of the parent interface is used and the section is not editable. To edit the Temperature field, click Make All Model Inputs Editable (). The available options are User defined (default), Common model input (the minput.T variable, set to 293.15 [K] by default) and all temperature variables from the physics interfaces included in the model. To edit the minput.T variable, click the Go to Source button (), and in the Common Model Inputs node under Global Definitions, set a value for the Temperature in the Expression for remaining selection section.
Surface-to-Ambient Radiation
Surface emissivity
The default Surface emissivity ε (a dimensionless number between 0 and 1) is taken From material. For User defined, it should be specified. An emissivity of 0 means that the surface emits no radiation at all while an emissivity of 1 means that it is a perfect blackbody.
Ambient temperature
For User defined, enter an Ambient temperature Tamb. Else, select an Ambient temperature defined in an Ambient Thermal Properties node under Definitions.
In 2D, the equation has an additional factor, dz, to account for the out-of-plane thickness.
Theory for Heat Transfer in Thin Structures
Location in User Interface
Context menus
Heat Transfer in Shells>Interfaces>Surface-to-Ambient Radiation, Interface
Heat Transfer in Films>Interfaces>Surface-to-Ambient Radiation, Interface
Heat Transfer in Fractures>Interfaces>Surface-to-Ambient Radiation, Interface
Ribbon
Physics Tab with Heat Transfer in Shells selected in the model tree:
Boundaries>Surface-to-Ambient Radiation, Interface