Home / Examples / Thermal Analysis [Watt] / Example 2: Temperature Distribution of Two Rods (Transient Analysis)

Example 2: Temperature Distribution of Two Rods (Transient Analysis)

General

Two square rods with different thermal conductivities are placed closely and subjected to the common temperature boundary condition.
The temperature distribution and the heat flux vectors are solved under the transient condition.
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	N/A

The total number of calculation steps is 130. The time step is 1 second.

Therefore, the temperature distributions for 130 sec are solved.
The output interval is changed from 1 in the first 10 steps to 5 in the steps to follow.

Tabs

Setting Item

Settings

Transient Analysis

Table

Number	Calculation Steps	Output Interval	Timestep [s]
1	10	1	1.0
2	120	5	1.0

Initial Temperature

0 [deg]

Model

The same as the example 1. The body attributes, the material properties and the boundary conditions are the same as well.

Two box-shape solid bodies are created. One is of gold and the other is of stainless steel (SUS301). Their thermal conductivities are different.

The temperature boundary conditions are set on the top and bottom faces.

Body Attributes and Materials

Body Number/Type	Body Attribute Name	Material Name
0/Solid	VOL1	002_Au *
1/Solid	VOL2	500_SUS301 *

* Available from the material DB

Boundary Conditions

Boundary Condition Name/Topology	Tab	Boundary Condition Type	Settings
Top/Face	Heat	Temperature	100 [deg]
Bottom/Face	Heat	Temperature	0 [deg]

Results

The temperature distributions in 5 sec, 60 sec and 130 sec are shown below.

In 5 sec

There is a huge difference between the temperature distributions of gold and SUS. This is due to the difference of the thermal conductivity.

In 60 sec

Even in 60 sec, the temperature distribution of SUS has not reached that of gold in 5 sec yet.

In 130 sec

The temperature distribution of SUS is getting close to that of gold.