Settings for the Heat Transfer in Thin Structures Interface

The is used primarily as a scope prefix for variables defined by the physics interface. Refer to such physics interface variables in expressions using the pattern <name>.<variable_name>. In order to distinguish between variables belonging to different physics interfaces, the name string must be unique. Only letters, numbers, and underscores (_) are permitted in the field. The first character must be a letter.

The default (for the first physics interface in the model) is htsh.

Define the ds (SI unit: m) (see Equation 4-50). The default is 0.01 m.

For 2D components, define the dz (SI unit: m) (see Equation 4-50). The default is 1 m.

Some check boxes are present in this section with certain COMSOL products.

	For a detailed overview of the functionality available in each product, visit http://www.comsol.com/products/specifications/

Click to select any of the following check boxes to activate related features:

•

Select the check box to enable the feature for the modeling of porous media. This check box is selected by default in The Heat Transfer in Fractures Interface.

The settings are the same as for the Heat Transfer interface. See Ambient Settings for details.

To display this section for any version of the Heat Transfer in Thin Structures interface, select the check box under the section.

	See The Heat Transfer with Surface-to-Surface Radiation Interface for details about the Surface-to-surface radiation method and Radiation resolution settings.

Define the .

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Keep the default value, to define a diffuse gray radiation model. In this case, the surface emissivity has the same definition for all wavelengths. The surface emissivity can still depend on other quantities, in particular on the temperature.

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For define a diffuse spectral radiation model with two spectral bands, one for short wavelengths, [0, λ1], (solar radiation) and one for large wavelengths, [λ1, +∞[, (ambient radiation). It is then possible to define the (SI unit: m), λ1, to adjust the wavelength intervals corresponding to the solar and ambient radiation. The surface properties can then be defined for each spectral band. In particular it is possible to define the solar absorptivity for short wavelengths and the surface emissivity for large wavelengths.

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For set the value ( to ), to define a diffuse spectral radiation model. It is then possible to provide a definition of the surface emissivity for each spectral band. Update (SI unit: m), λ1, λ2, ..., to define the wavelength intervals [λi − 1, λi[ for i from 1 to the . Note that the first and the last endpoints, λ0 and λN (with N equal to the value selected to define the ), are predefined and equal to 0 and +∞ respectively.

Modify the if it is different from 1 that corresponds to vacuum refractive index and that is usually a good approximation for air refractive index.

Also select the check box to enable the ability of defining radiation groups, which can, in many cases, speed up the radiation calculations.

Select the : (the default) or . See below for descriptions of each method.

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For select the . Sharp angles and small gaps between surfaces can require a higher integration order for more accuracy but also more computational cost to evaluate the irradiation.

Select(the default), ,, ,or to define the used for the surface radiosity shape function.

The check box is selected by default and should remain selected for optimal performance for heat transfer in fluids or other applications that include a convective or translational term. provides extra diffusion in regions with sharp gradients. The added diffusion is orthogonal to the streamlines, so streamline diffusion and crosswind diffusion can be used simultaneously. The check box is also selected by default.

The check box is not selected by default.

	Heat Transfer Consistent and Inconsistent Stabilization Methods

Add both a and a interface (found under the branch when adding a physics interface) then click the button (

) and select to display this section.

When the component contains a moving mesh, the check box is selected by default. 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 moving mesh, and when this option is active, the heat transfer features automatically account for deformation effects on heat transfer properties. In particular the effects of volume changes on the density are considered. Rotation effects on the thermal conductivity of an anisotropic material and, more generally, deformation effects on an arbitrary thermal conductivity, are also covered. When the check box is not selected, the feature inputs (for example, Heat Source (Heat Transfer in Thin Shells Interface) and Heat Flux (Heat Transfer in Thin Shells Interface)) are not converted and are instead defined on the frame.

To display this section, click the button (

) and select .

In the Heat Transfer in Thin Structures interfaces you can choose not only the order of the discretization, but also the type of shape functions: Lagrange or serendipity. For highly distorted elements, Lagrange shape functions provide better accuracy than serendipity shape functions of the same order. The serendipity shape functions will however give significant reductions of the model size for a given mesh containing hexahedral, prism, or quadrilateral elements.

The shape functions used for the temperature are for the modeling of heat transfer in thin shells, and for the modeling of heat transfer in thin films and heat transfer in fractures.

The Heat Transfer in Thin Structures interfaces have the dependent variable T. The dependent variable names can be changed. Editing the name of a scalar dependent variable changes both its field name and the dependent variable name. If a new field name coincides with the name of another field of the same type, the fields share degrees of freedom and dependent variable names. A new field name must not coincide with the name of a field of another type or with a component name belonging to some other field.