Home / Examples / Thermal Analysis [Watt] / Example 20: Further Analysis with Saved Temperature Data (Transient Analysis)

Example 20: Analysis with Saved Temperature Data (Transient Analysis)

General

The results of [Example 4: Heating due to the Iron Loss (Temperature-Dependent Materials)] of the magnetic-thermal coupled analysis is used as the initial temperature to perform the heat dissipation analysis.
The result of the magnetic-thermal coupled analysis is used as an initial temperature.
The models of the magnetic-thermal coupled analysis and transient thermal analysis are prepared in one project.
The temperature distribution and the heat flux vectors are solved.
Unless specified in the list below, the default conditions will be applied.

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

Analysis Space

Item	Settings
Analysis Space	3D
Model Unit	mm

Analysis Conditions

Item	Settings
Solver	Thermal Analysis [Watt]
Analysis Type	Transient Analysis
Options	None

The setting on the transient analysis tab are as follows. As the calculation steps is 20 and the timestep is 30 sec, the temperature distributions for 10 minutes
are solved where the resulting temperature of the magnetic-thermal coupled analysis is set to the initial temperature.

Tabs

Setting Item

Settings

Transient Analysis

Table

Number	Calculation Steps	Output Interval	Timestep [s]
1	20	1	30

Results import

Import Type

Initial Temperature

Specify Results

Specify analysis model

"gauwat_ex4"

Specify Mode

Automatic

Model

Basically the same as Example 4: Heating due to the Iron Loss (Temperature-Dependent Materials),

Body Attributes and Materials

Body Number/Type	Body Attribute Name	Material Name	Mesh Size
0/Solid	Coil	008_Cu *	1
1/Solid	Core	Core	2

* Available from the material DB

The material properties of the core are set up as follows.

Material Name	Tab	Settings
Core	Thermal Conductivity	Thermal Conductivity: 10 [W/m/deg]
	Density	Density: 7000 [kg/m3]
	Specific Heat	Specific Heat: 800 [J/Kg/deg]

Boundary conditions

Select "Natural convection (automatic calculation)" on the outer boundary condition.

Boundary Condition Name/Topology

Tab

Boundary Condition Type

Settings

Outer Boundary Condition *

Heat

Heat Transfer: Convection

Natural Convection (Automatic Coefficient Calculation)

Ambient Temperature: 25 [deg]

* To set the outer boundary condition, on the [Model] tab,

click [Outer Boundary Condition Setting].

* The correction coefficient for the natural convection is calculated automatically. For the details, please refer to the Thermal tab.

Procedure

To take in the temperature, in the magnetic-thermal coupled analysis, firstly run the analysis model, "gauwat_ex4",
and then run the analysis model, "wat_ex20".

The initial temperature is set according to the results of the magnetic-thermal coupled analysis.

Results

The result at the time 0s is the temperature distribution taken in.

The temperature distributions in 30s, 300s and 600s are shown below.
The range of color scale is fixed from 20 [deg] to 90 [deg].

The temperature of Core goes down over time.

Temperature Distribution in 30 sec

Temperature Distribution in 300 sec

Temperature Distribution in 600 sec