Settings for the Heat Transfer Interface
The Label is the default physics interface name.
The Name 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 Name field. The first character must be a letter.
The default Name (for the first physics interface in the model) is ht.
Physical Model
In 2D and 1D axisymmetric components, set the Thickness dz, which is the thickness of the domain in the out-of-plane direction. The default value is 1 m.
In 1D components, set the Cross sectional area Ac and the Cross sectional perimeter Pc of the domain. Default values are 1 m2 and , respectively.
When the Heat Transfer interface is coupled to an interface modeling radiation (Surface-to-Surface Radiation, Radiation in Participating Media, Radiation in Absorbing-Scattering Media), through a multiphysics coupling (Heat Transfer with Surface-to-Surface Radiation, Heat Transfer with Radiation in Participating Media, or Heat Transfer with Radiation in Absorbing-Scattering Media), these inputs are automatically defined from the multiphysics coupling. These variables are set to unit length of the component unit system. This corresponds to the assumption that the geometry is infinite in the out-of-plane direction and that the equations are defined per unit length. This assumption is required as it corresponds to the view factor computation in these dimensions.
Set the Reference temperature Tref. It is used for the evaluation of the reference density ρref when the Heat Transfer interface is coupled through Nonisothermal Flow multiphysics coupling to a Fluid Flow interface with Compressibility set to Incompressible and Specify reference temperature set to From heat transfer interface. When Specify reference temperature is set to From fluid flow interface in Nonisothermal Flow coupling node, this input is synchronized with the corresponding input in the Single Phase Flow interface. It is also used in the definition of the reference enthalpy Href which is set to 0 J/kg at pref (1 atm) and Tref. The corresponding interface variable is ht.Tref.
Two check boxes are also 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 the versions of the ht interface as described in Benefits of the Different Heat Transfer Interfaces:
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Selecting Isothermal domain provides support for isothermal domain modeling. See Isothermal Domain Interface and Isothermal Domain.
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Select the Heat Transfer in Porous Media check box to enable the Porous Medium, Fracture, and Building Material features. See The Heat Transfer in Porous Media Interface and The Heat Transfer in Building Materials Interface.
Consistent Stabilization
Under the Heat Transfer section, the Streamline diffusion 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. Crosswind diffusion 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 Crosswind diffusion check box is also selected by default.
Inconsistent Stabilization
Under the Heat Transfer section, the Isotropic diffusion check box is not selected by default.
Heat Transfer Consistent and Inconsistent Stabilization Methods
Discretization
To display all settings available in this section, click the Show More Options button () and select Advanced Physics Options in the Show More Options dialog box. You can choose the type and order of the shape functions used for the variables solved by the Heat Transfer interfaces.
Temperature
For the temperature, 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. At first order, Lagrange and serendipity shape functions are the same.
The default shape functions used for the temperature are Quadratic Lagrange for the modeling of heat transfer in solids, and Linear for the modeling of heat transfer in fluids. See the description of each version of the physics interface for more details.
Damaged Tissue Indicator
When the Thermal Damage subnode is added under Biological Tissue, you can choose the discretization level of the Damage tissue indicator shape function: Constant (the default), Linear, Quadratic, Cubic, Quartic, or Quintic.
Irreversible Transformation Indicator
When the Irreversible Transformation subfeature is added under a Solid node, you can choose the discretization level of the Irreversible transformation indicator shape function: Constant (the default), Linear, Quadratic, Cubic, Quartic, or Quintic.
Dependent Variables
The Heat Transfer interfaces have the dependent variable Temperature 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.