Thin Layer (Heat Transfer interface) and Solid (Heat Transfer in Shells interface)
This node defines the thermal conductivity and thermodynamics properties 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:
•
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 thermal properties. Each sub-layer can be distinguished when a heat source is applied to the layer. This option may also be used to enforce consistent initial conditions.
•
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 sub-layers are not distinguished when a heat source is applied to the layer.
•
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 thermal properties, and heat sources can be applied on a sub-layer selection, and on up and down sides of the layer.
Layer Selection
Select the applicable layers (the default setting is All layered materials) defining the required material properties for the node.
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 Layered Material list).
When a layered material stack or link is selected from the Layered Material list, unselect the check boxes corresponding to layers where the node should not be applied in the Selection table.
You can visualize the selected layered materials and layers in each layered material by clicking the Layer cross section preview and Layer 3D preview buttons.
Note that this section is not editable when Solid is the default node of the Heat Transfer in Shells interface.
•
For a general description of layer and interface selections, see The Layer Selection and Interface Selection Sections.
•
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.
Volume reference temperature
This section is available when a temperature-dependent density is used. On the material frame, the density is evaluated onto a reference temperature to ensure mass conservation in the presence of temperature variations. By default the Common model input is used. This corresponds to the variable minput.Tempref, which is set by default to 293.15 [K]. To edit it, click the Go to Source button (), and in the Common Model Inputs node under Global Definitions, set a value for the Volume reference temperature in the Expression for remaining selection section.
The other options are User defined and all temperature variables from the physics interfaces included in the model.
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.
Layer Model
The available options for Layer type are Thermally thin approximation, Thermally thick approximation, and General.
If Layer type is Thermally thick approximation, from the Specify list select Layer properties (the default) or Thermal resistance.
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.
Heat Conduction
The default Thermal conductivity k is taken From shell. For User defined select Isotropic, Diagonal, Symmetric, or Anisotropic to enter another value or expression.
Alternatively, set a value for the Thermal resistance Rs if Specify is set to Thermal resistance in the Layer Model section (for Thermally thick approximation).
Thermodynamics
By default the Density ρ and Heat capacity at constant pressure Cp of the layer are taken From shell. See Material Density in Features Defined in 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.
These subnodes are available for Thin Layer node:
•
Heat Source (Thin Layer, Thin Film, Fracture) — to add a layer internal heat source, Qs, within the layer.
•
 Heat Flux (Thin Layer, Thin Film, Fracture) — to add a heat flux through a specified set of boundaries.
•
Temperature (Thin Layer, Thin Film, Fracture, and Heat Transfer in Shells)  — to set a prescribed temperature condition on a specified set of boundaries.
•
 Surface-to-Ambient Radiation (Thin Layer, Thin Film, Fracture, and Heat Transfer in Shells interface) — to add a surface-to-ambient radiation for the layer end.
When multiple layers are defined they are numbered from the downside (Layer 1) to the upside. 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.
•
Theory for Heat Transfer in Thin Structures
•
Boundary Wall Temperature
•
Plotting Results in Thin Layers Extra Dimensions
•
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
•
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 in Solids>Thin Layer
Heat Transfer in Shells>Solid
 Ribbon
Physics Tab with interface as Heat Transfer in Solids selected:
Boundaries>Thin Layer
Physics Tab with interface as Heat Transfer in Shells selected:
Boundaries>Solid