Thin Layer
This node defines the thickness and thermal conductivity of a material located on internal or external boundaries. This material can be formed of one or more layers, and different conductive behaviors can be modeled through the setting of the Layer type:
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Select Thermally thick approximation to model a layer that is a bad thermal conductor compared to the adjacent geometry. In this case, the tangential heat flux is neglected and only the heat flux across the layer’s thickness is considered. The layer can be constituted of multiple sub-layers with specific thickness and conductivity. The up and down sides can be distinguished when a heat source is applied to the layer. This option may also be used to enforce consistent initial conditions.
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Select Thermally thin approximation to model a layer that is a good thermal conductor compared to the adjacent geometry. In this case, the temperature difference and heat flux across the layer’s thickness are neglected. Only the tangential heat flux is considered. The up and down sides are not distinguished when a heat source is applied to the layer.
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Select General to model a layer in which both the normal and tangential heat fluxes should be considered. The layer can be constituted of multiple sub-layers with specific thickness and conductivity, and heat sources can be applied on a sub-layer selection, and on up and down sides of the layer.
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.
Thin Layer
The available options for Layer type are Thermally thin approximation, Thermally thick approximation, and General.
Thermally thin approximation
For Thermally thin approximation enter a value or expression for the Layer thickness ds.
Thermally thick approximation
From the Specify list select Layer properties (the default) or Thermal resistance.
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For Layer properties enter a value or expression for the Layer thickness ds.
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For Thermal resistance enter a value or expression for the Thermal resistance Rs.
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By default the Multiple layers check box is not selected. For Layer properties click to select the check box to define multiple sandwiched thin layers with different thermal conductivities.
General
For General no additional setting is required in this section.
Heat Conduction
This section is not available when Layer type is set to Thermally thick approximation and Specify is set to Thermal Resistance in the Thin Layer settings.
Thermally thin approximation (Layer Type)
For Thermally thin approximation the default Layer thermal conductivity ks is taken From material. For User defined select Isotropic, Diagonal, Symmetric, or Anisotropic to enter another value or expression. If the thickness is zero, the thin layer does not take effect.
Thermally thick approximation (Layer Type)
The default Layer thermal conductivity ks is taken From material. For User defined select Isotropic, Diagonal, Symmetric, or Anisotropic to enter another value or expression.
General (Layer Type)
Select the Number of layers to define (1 to 5) and set the properties for each layer selected.
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Select an option from the Layer (1, 2, 3, 4, or 5) list to assign a material to each layer. The default Boundary material takes the material from the boundary.
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For each layer, enter the Layer thickness ds.
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The default Thermal conductivity ks is taken From material, which is then taken from the material selected in Layer (1, 2, ...). For User defined enter another value or expression.
Thermodynamics
Set the following properties for each Layer:
By default the Layer density ρs and Layer heat capacity Cp, s values are taken From material. See Material Density in Features Defined on the Material Frame if a temperature-dependent density should be set. For User defined enter other values or expressions.
When Layer type is Thermally thick approximation, these properties are only used in time-dependent studies, but must be set in all cases.
Thin Layer Opacity
This section is only available when the Surface-to-surface radiation check box is selected under the Physical Model section on the parent physics interface.
Select Opaque (the default) or Transparent to set the layer’s opacity type.
This is needed when the thin layer (with Layer type as Thermally thick approximation or General) contributes with any boundary condition from the Radiation menu. It picks the side where irradiation starts from.
Layer Discretization
This section is only available when the Layer type is set to General.
Define the Number of elements used for discretizing the layer thickness.
These subnodes are available for Thin Layer node:
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Layer Heat Source — to add a layer internal heat source, Qs, within the layer.
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 Line Heat Flux (Thin Layer, Thin Film, Fracture) — to add a heat flux through a specified set of boundaries.
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Temperature (Thin Layer, Thin Film, Fracture, and Heat Transfer in Thin Shells)  — to set a prescribed temperature condition on a specified set of boundaries.
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 Surface-to-Ambient Radiation (Thin Layer, Thin Film, Fracture) — to add a surface-to-ambient radiation for the layer end.
When multiple layers are defined they are numbered from the upside (Layer 1) to the downside.
Theory for Heat Transfer in Thin Structures
Boundary Wall Temperature
Plotting Results in Thin Layers Extra Dimensions
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Heat Transfer in a Surface-Mount Package for a Silicon Chip: Application Library path Heat_Transfer_Module/Power_Electronics_and_Electronic_Cooling/
surface_mount_package
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Silica Glass Block Coated with a Copper Layer: Application Library path Heat_Transfer_Module/Tutorials,_Thin_Structure/copper_layer
Location in User Interface
Context menus
Heat Transfer>Thin Layer
Heat Transfer in Solids>Thin Layer
Heat Transfer in Fluids>Thin Layer
Heat Transfer in Porous Media>Thin Layer
Bioheat Transfer>Thin Layer
Heat Transfer with Surface-to-Surface Radiation>Thin Layer
Heat Transfer with Radiation in Participating Media>Thin Layer
Heat Transfer>Pairs>Thin Layer
Heat Transfer in Solids>Pairs>Thin Layer
Heat Transfer in Fluids>Pairs>Thin Layer
Heat Transfer in Porous Media>Pairs>Thin Layer
Bioheat Transfer>Pairs>Thin Layer
Heat Transfer with Surface-to-Surface Radiation>Pairs>Thin Layer
Heat Transfer with Radiation in Participating Media>Pairs>Thin Layer
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, Bioheat Transfer, Heat Transfer with Surface-to-Surface Radiation or Heat Transfer with Radiation in Participating Media selected:
Boundaries>interface>Thin Layer
Pairs>interface>Thin Layer