Example19 Time-Dependent Heat Source (Transient Analysis)

General

Two heat sources are placed on a substrate. The heat is released to the ambient by natural convection.
The transient analysis is performed. A heat source generates heat for a certain period.
The model is the same as Exercise 14: Natural Convection with Correction Coefficient Automatically Calculated.
The temperature distribution and the heat flux vectors are solved.
Unless specified in the list below, the default conditions will be applied.

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 Transient Analysis tab is set up as follows. The total number of steps is 20. The time step is 60 second.

Therefore, the temperature distributions for 1200 seconds are solved.

Tabs

Setting Item

Settings

Transient analysis

Table

Number	Calculation steps	Output steps	Time step [s]
1	20	1	60

Initial Temperature

25[deg]

Model

The same as Exercise 14. The material properties and the boundary conditions are the same as well.

Model

To use the boundary condition of “Natural convection (automatic calculation)”, the model must be oriented so that the negative Z direction points the ground.

Body Attributes and Materials

The finer mesh size is set for via holes (HOLE), where the heat flux is expected to change drastically.

Body Number/Type	Body Attribute Name	Material Name	Mesh Size
0/Solid	SUB	006_Glass_epoxy *1
1/Solid	GND	008_Cu *2
2/Solid	MAINCHIP	001_Alumina *2
3/Solid	SUBCHIP	001_Alumina *2
4/Solid	HOLE	008_Cu *2	0.5
5/Solid	HOLE	008_Cu *2	0.5
6/Solid	HOLE	008_Cu *2	0.5
7/Solid	HOLE	008_Cu *2	0.5
8/Solid	HOLE	008_Cu *2	0.5
9/Solid	HOLE	008_Cu *2	0.5
10/Solid	HOLE	008_Cu *2	0.5
11/Solid	HOLE	008_Cu *2	0.5

*1 Available from the Material DB.

*2 Available from the Material DB. The specific heat is manually entered.

The heat sources of MAINCHIP and SUBCHIP are set up as follows.
MAINCHIP is time-dependent. It generates 0.2[W] heat for 600[s]. After that, no heat is generated.

Body Attribute Name

Tab

Settings

MAINCHIP

Heat Source

0.2[W]
Select Time dependency.

Weight function