Home / Examples / Coupled Analysis / Electromagnetic-Thermal Analysis [Hertz/Watt] / Example 2: Microwave Oven Transient Analysis

Example 2: Microwave Oven Transient Analysis

            

General

• The heating of a piece of meat on the bone placed in a microwave oven is simulated.
  

• It is solved by coupling the electromagnetic harmonic analysis and the thermal transient analysis.
   

• The temperature-dependent relative permittivity and dielectric tangent are taken into account.
   

• Unless specified in the list below, the default conditions are applied.
   

• Obtain this session's project file. (Right-click and choose 'Save link as')
  
  

• Results will vary depending on Femtet version and the PC environment.

• This example is calculated using Femtet ver.2023.0.0.

 

Analysis Space

Item	Settings
Analysis Space	3D
Model Unit	mm

 

Analysis Conditions

Item	Settings
Solver	Electromagnetic Analysis [Hertz] Thermal Analysis [Watt]
Analysis Type	Electromagnetic Analysis: Harmonics Analysis Thermal Analysis: Transient Analysis

 

The harmonic analysis and the transient analysis are set as follows.

Tab	Setting Item	Settings
Mesh	General Mesh Size:	40
	Element Type	2nd-order Element
	Adaptive Mesh	Off (to shorten the calculation time)
	Frequency-Dependent Meshing	Reference Frequency: 2.45x109 [Hz]
Electromagnetic-Thermal Analysis	Electromagnetic Analysis Type	Harmonic Analysis
	Thermal Analysis Type	Transient Analysis
	Weight Function	Select
	Weight Function	No. Time Weight 1 0 1 2 40 1 3 40.1 0 4 60 0
Harmonic Analysis	Frequency	Minimum: 2.45×109 [Hz] Maximum: 2.45x109 [Hz]
	Input	500 [W]
Transient Analysis	Table	No. Number of Calculation Steps Output Interval Timestep [s] 1 6 1 10
	Initial Temperature	20 [deg]

 

 

Model

The model is the same as that in the example 1.

On the top of a cavity box, is placed a waveguide, into which electromagnetic waves enter. A port (PORT1) is set at the end of the waveguide.

A piece of meat on the bone is placed on a plate.

 

 

Body Attributes and Materials

Body Number/Type	Body Attribute Name	Material Name	Mesh Size
0/Solid	CAVITY	000_Air(*)
5/Solid	WAVEGUIDE	000_Air(*)
6/Sheet	Imprinting body
13/Solid	PLATE	PLATE	10
75/Solid	BONE	BONE	10
96/Solid	MEAT	WATER	10

* Available from the material DB

 

 

 

Material Name	Tab	Value
PLATE	Permittivity	Relative Permittivity: 7.0 Dielectric Tangent: 0.0
	Thermal Conductivity	1.5 [W/m/deg]
BONE	Permittivity	Relative Permittivity: 7.0 Dielectric Tangent: 0.1
	Thermal Conductivity	1.5 [W/m/deg]
WATER	Permittivity & Dielectric Tangent	No. Temperature Relative Permittivity Dielectric Tangent 1 0 88.15 10.5 2 10 84.14 8.5 3 20 80.36 7.0 4 30 76.78 5.8 5 40 73.39 4.7 6 50 70.15 3.8 7 60 67.03 3.0 8 70 64.01 2.5 9 80 61.06 2.2 10 90 58.15 2.0
	Thermal Conductivity	1.5 [W/m/deg]

Boundary Conditions

Boundary Condition Name/Topology	Tab	Boundary Condition Type	Settings
PORT1/Face	Electric	Port	Reference Impedance: Select [Use the characteristic impedance calculated from the port structure].
EW/Face	Electric	Electric Wall
Outer Boundary Condition	Electric	Electric Wall

The default setting is [Magnetic Wall] for the electric boundary, and [Adiabatic] for the thermal boundary.

 

Results

The temperature inside the meat can be observed to rise and fall according to the weight function of the input power of electromagnetic waves.

 

The contours of temperature after 40 sec represent the temperature distribution inside the meat.