The Microwave Heating Interface

The interface (

) is used to model electromagnetic heating for systems and devices that are on a scale ranging from 1/10 of a wavelength up to, depending on available computer memory, about 10 wavelengths. This multiphysics interface adds an Electromagnetic Waves, Frequency Domain interface and a Heat Transfer in Solids interface. The multiphysics couplings add the electromagnetic losses from the electromagnetic waves as a heat source, and the electromagnetic material properties can depend on the temperature. The modeling approach is based on the assumption that the electromagnetic cycle time is short compared to the thermal time scale.

The following table shows what study step combinations of Electromagnetic Waves, Frequency Domain interface and Heat Transfer in Solids interface are supported from the Microwave Heating interface.

Table 6-1: study step combinations of Electromagnetic Waves, Frequency Domain interface and Heat Transfer in Solids interface
Preset Studies	Electromagnetic Waves, Frequency Domain interface	Heat Transfer in Solids interface
Frequency-Stationary	Frequency Domain	Stationary
Frequency-Transient	Frequency Domain	Transient

When a predefined interface is added from the branch (

) of the or windows, and interfaces are added to the Model Builder.

In addition, a node is added, which automatically includes the multiphysics coupling features , , and .

On the Constituent Physics Interfaces

The Electromagnetic Waves, Frequency Domain interface computes time-harmonic electromagnetic field distributions. To use this physics interface, the maximum mesh element size should be limited to a fraction of the wavelength. Thus, the domain size that can be simulated scales with the amount of available computer memory and the wavelength. The physics interface solves the time-harmonic wave equation for the electric field.

The Heat Transfer in Solids interface provides features for modeling heat transfer by conduction, convection, and radiation. A Heat Transfer in Solids model is active by default on all domains. All functionality for including other domain types, such as a fluid domain, is also available. The temperature equation defined in solid domains corresponds to the differential form of Fourier's law that may contain additional contributions like heat sources.


	In previous versions of COMSOL Multiphysics, a specific physics interface called Microwave Heating was added to the Model Builder. Now, a predefined multiphysics coupling approach is used, improving the flexibility and design options for your modeling. For specific details, see Multiphysics Modeling Approaches in the COMSOL Multiphysics Reference Manual.

Settings for Physics Interfaces and Coupling Features

When physics interfaces are added using the predefined couplings, for example , specific settings are included with the physics interfaces and the coupling features.

However, if physics interfaces are added one at a time, followed by the coupling features, these modified settings are not automatically included.

For example, if single and interfaces are added, COMSOL adds an empty node. You can choose from the available coupling features, , , and , but the modified settings are not included.


	Coupling features are available from the context menu (right-click the Multiphysics node) or from the Physics toolbar, Multiphysics menu.

Table 6-2: Modified settings for a Microwave Heating interface
Physics Interface or Coupling Feature	Modified Settings (if any)
Electromagnetic Waves, Frequency Domain	No changes.
Heat Transfer in Solids	No changes.
Electromagnetic Heat Source	The Domain Selection is the same as that of the participating physics interfaces. The corresponding Electromagnetic Waves, Frequency Domain and Heat Transfer in Solids interfaces are preselected in the Electromagnetic Heat Source section (described in the COMSOL Multiphysics Reference Manual).
Boundary Electromagnetic Heat Source	The Boundary Selection is the same as the exterior and interior boundaries of the Domain Selection of the participating physics interfaces. The corresponding Electromagnetic Waves, Frequency Domain and Heat Transfer in Solids interfaces are preselected in the Boundary Electromagnetic Heat Source section (described in the COMSOL Multiphysics Reference Manual).
Temperature Coupling	The corresponding Electromagnetic Waves, Frequency Domain and Heat Transfer in Solids interfaces are preselected in the Temperature Coupling section (described in the COMSOL Multiphysics Reference Manual).


	A side effect of adding physics interfaces one at a time is that two study types—Frequency-Stationary and Frequency-Transient—are not available for selection until after at least one coupling feature is added. In this case, it is better to first add an Empty Study, then add the coupling features to the Multiphysics node, and lastly, right-click the Study node to add the study steps as needed.

Physics Interfaces and Coupling Features


	Use the online help in COMSOL Multiphysics to locate and search all the documentation. All these links also work directly in COMSOL Multiphysics when using the Help system.

Coupling Features

•

The Electromagnetic Heat Source coupling feature node is described in this section.

•

The Boundary Electromagnetic Heat Source and Temperature Coupling coupling feature nodes are described for The Joule Heating Interface in the COMSOL Multiphysics Reference Manual.

Physics Interface Features

Physics nodes are available from the ribbon toolbar (Windows users), context menu (Mac or Linux users), or right-click to access the context menu (all users).


	In general, to add a node, go to the Physics toolbar, no matter what operating system you are using. Subnodes are available by clicking the parent node and selecting it from the Attributes menu.

•

The available physics features for The Electromagnetic Waves, Frequency Domain Interface are listed in the section Domain, Boundary, Edge, Point, and Pair Nodes for the Electromagnetic Waves, Frequency Domain Interface.

•

See The Heat Transfer Interfaces in the COMSOL Multiphysics Reference Manual for information about the available physics features for heat transfer.


	If you have an add-on module, such as the Heat Transfer Module, there are additional specialized physics nodes available and described in the individual module documentation.


	Microwave Oven: Application Library path RF_Module/Microwave_Heating/microwave_oven