General
Home / Examples / Thermal Analysis [Watt] / Example 14: Natural Convection with Correction Coefficient Automatically Calculated
The model consists of two heat sources and a substrate. The heat sources are placed on the substrate.
The heat is released to the ambient by natural convection.
The coefficient of natural convection is calculated automatically based on the model shape.
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.
Item |
Settings |
Analysis Space |
3D |
Model Unit |
mm |
Item |
Settings |
Solver |
Thermal Analysis [Watt] |
Analysis Type |
Steady-state Analysis |
Options |
N/A |
To use the boundary condition of [Natural convection (automatic calculation)], the model must be directed so that the negative Z direction points to the ground.
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/Solid |
GND |
008_Cu * |
|
2/Solid |
MAINCHIP |
001_Alumina * |
|
3/Solid |
SUBCHIP |
001_Alumina * |
|
4/Solid |
HOLE |
008_Cu * |
0.5 |
5/Solid |
HOLE |
008_Cu * |
0.5 |
6/Solid |
HOLE |
008_Cu * |
0.5 |
7/Solid |
HOLE |
008_Cu * |
0.5 |
8/Solid |
HOLE |
008_Cu * |
0.5 |
9/Solid |
HOLE |
008_Cu * |
0.5 |
10/Solid |
HOLE |
008_Cu * |
0.5 |
11/Solid |
HOLE |
008_Cu * |
0.5 |
* Available from the material DB
The heat sources of MAINCHIP and SUBCHIP are set up as follows.
Body Attribute Name |
Tab |
Settings |
MAINCHIP |
Heat Source |
0.2 [W] |
SUBCHIP |
Heat Source |
0.1 [W] |
Select "Natural convection (automatic calculation)" on the outer boundary condition.
Boundary Condition Name/Topology |
Tab |
Boundary Condition Type |
Settings |
Outer Boundary Condition |
Thermal |
Heat Transfer: Convection |
Natural Convection (Automatic Coefficient Calculation) Room Temperature: 25 [deg] |
* The correction coefficient for the natural convection is calculated automatically. For the details, please refer to the Thermal tab.
The temperature distribution is shown below.
The temperature of MAINCHIP is the highest.
The vectors of the heat flux are shown below.
The heat is well transfered through the via holes (HOLE).