Thin Film (Heat Transfer Interface) and Fluid (Heat Transfer in Shells Interface)

Thisnode behaves like Fluid but is applicable on boundaries.

When the node is added manually in the Heat Transfer in Films interface, and for the node, select the check box to make the node applicable only if a layered material is defined on the boundary. If a layered material ( with specified, , , or ) is available, its name is then displayed beside the boundary index (for example, slmat1), otherwise the boundary is marked as not applicable.

When is the default node of the Heat Transfer in Films interface, it is applied on all boundaries where the Heat Transfer in Films interface is applied, and neither the boundary selection nor the check box are editable.

Note that when the is in the section of the parent interface or node, the check box is not editable.

Shell Properties

Fluid (Heat Transfer in Shells Interface)

Different settings are available, depending on the settings in the Shell Properties section of the parent interface, and whether is the default node or was added manually:

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When the is in the section of the parent interface, the same layered material is used in the node, but you can limit the contribution to individually selected layers by clearing the check box. For a given or , you get access to a list of check boxes for the selection of the individual layers. In this case, both the and options are available in the section.

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When the is in the section of the parent interface, the is taken in the node. This option is not editable when is the default node, but you can change to and override the interface setting with a specific value or expression for Lth when the node was added manually. In this case, only the option is available in the section.

Thin Film (Heat Transfer Interface)

Two options are available for the :

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When the is , the Extra Dimension tool is used to solve the equations through the thickness of a layered material. It is possible to consider several layers with different thermal properties varying through the thickness. This makes the and options available for in the section. You can limit the contribution to individually selected layers by clearing the check box. For a given or , you get access to a list of check boxes for the selection of the individual layers.

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Alternatively, set to , and seta user defined value or expression for the Lth. This option should be used for thermally thin layers, for which no through-thickness temperature variation is expected in the layered material. This makes the only option available for in the section.

You can visualize the selected layered materials and layers in each layered material by clicking the and buttons.

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For a general description of layer and interface selections, see Layer and Interface Selection Tools.

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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. See Layered Material, Layered Material Link, Layered Material Stack, Layered Material Link (Subnode), and Single-Layer Materials 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 field, click (

). The available options are (default), (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 button (

), and in the node under , set a value for the in the section.

Absolute Pressure

The absolute pressure is used in some predefined quantities that include the enthalpy (the energy flux, for example).

It is also used if the ideal gas law is applied. See Thermodynamics, Fluid.

The default pA is . When additional physics interfaces are added to the model, the absolute pressure variables defined by these physics interfaces can also be selected from the list. For example, if a interface is added you can select from the list. The option corresponds to the minput.pA variable, set to 1 atm by default. To edit it, click the button (

), and in the node under , set a value for the in the section.

Layer Model

The available options for are ,and (when the is in the Shell Properties section). The former is a lumped model that accounts only for tangential temperature gradients (along the film), whereas the latter accounts also for the normal gradients of temperature (through the film’s thickness). The second model may be used for the modeling of bearings for example.


	Within a layered material selection, a single Layer type should be used. If two layer types are needed for the same layered material, the original material should be duplicated so that one layered material is defined for each layer type. A Shell Continuity (Heat Transfer Interface) and Continuity (Heat Transfer in Shells Interface) node may be added between the two layered materials.


	The settings for the Model Input, Heat Convection, Heat Conduction, Fluid, and Thermodynamics, Fluid sections are the same as for Fluid.


	The thermal conductivity of the thin film is supposed to be isotropic, even if an anisotropic property is defined for the material.

Location in User Interface

Context Menus

Ribbon

Physics Tab with interface as selected: