Home / Examples / Coupled Analysis / Simple Fluid-Thermal Analysis [Pascal/Watt] / Example 1: Air Cooling of Chips on Substrate

Example 1: Air Cooling of Chips on Substrate (Forced Convection)

General

• Two heat sources are placed on a substrate,
  and the heat dissipation by forced convection is analyzed in the steady state.
   

• See [Simple Fluid-Thermal Analysis by Femtet] for more details.
   

• The air flow is assumed to be laminar, non-viscous and incompressible.
   

• The flow velocity distribution, the temperature distribution and the heat flux vectors are solved.
   

• 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.

Analysis Space

Item	Settings
Analysis Space	3D
Model Unit	mm

 

Analysis Conditions

Item	Settings
Solver	Simple Fluid Analysis [Pascal] Thermal Analysis [Watt]
Analysis Type	Steady-state Analysis
Options	N/A

 

Tab	Setting Item	Settings
Mesh Tab	Mesh Size	8

Model

The fluid (Air) is created by a solid body and defined as [Fluid] in the material property.

Body Attributes and Materials

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 *
5/Solid	HOLE	008_Cu *
6/Solid	HOLE	008_Cu *
7/Solid	HOLE	008_Cu *
8/Solid	HOLE	008_Cu *
9/Solid	HOLE	008_Cu *
10/Solid	HOLE	008_Cu *
11/Solid	HOLE	008_Cu *
12/Solid	Air	000_Air(*)

* Available from the material DB

 

The heat quantities of MAINCHIP and SUBCHIP are set up as follows.

Body Attribute Name	Tab	Settings
MAINCHIP	Heat Quantity	0.2 [W]
SUBCHIP	Heat Quantity	0.1 [W]
Air	Solid/Fluid

 

Fluid is set to Air. The main flow temperature is set to 25deg C.

Material Property Name	Tab	Settings
Air	Solid/Fluid	State: Fluid Main Flow Temperature: 25 [deg]

 

Boundary Conditions

The flow velocity is given at the inflow face and the velocity potential is given at the outflow face.

The outflow face is set to the opening by setting the velocity potential of the outflow face to 0 [m^2/s].
 

• The details are explained at [Fluid] tab of the boundary condition.
   

Boundary Condition Name/Topology	Tab	Boundary Condition Type	Settings
in/Face	Fluid	Flow Velocity	1 [m/s]
out/Face	Fluid	Velocity Potential	0 [m^2/s]

Results

The distribution of the flow velocities is shown below.

 

 

The temperature distribution is shown below.

 

• The temperature distribution of the fluid is not available.

SUBCHIP is hotter than MAINCHIP as its heat quantity is higher and it is positioned down the flow.

 

The vectors of the heat flux are shown below.