Home / Examples / Coupled Analysis / Fluid-Thermal Analysis [Bernoulli/Watt] / Example 14: Cooling by Fan

Example 14: Cooling by Fan

General

A heat source is placed inside the case. A fan on the case cools the heat source.
The fan pressure and the flow rate are determined according to the pressure loss. The operating point of the fan can be output as well.
The monitoring values are used for convergence judgment.
The temperature distribution and the heat flux vectors are solved.
The results can be viewed by the simultaneous display of temperature contours and streamlines.
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	m

Analysis Condition

Item	Setting
Solver	Fluid Analysis [Bernoulli] Thermal Analysis [Watt]
Analysis Type	Fluid Analysis: Steady-state Analysis Thermal Analysis: Steady-state Analysis
Detailed Setting	Convergence Judgment by Monitoring Value Enable

Tab

Monitoring Quantity

Settings

Monitoring

Temperature

Monitoring Domain: Select [Body Attribute]
Monitoring Value: Select [Maximum Value]
Body Attribute Name: Select [All Body Attributes]

Then click [Add].

Volumetric Flow Rate

Monitoring Domain: Select [Body Attribute]
Body Attribute Name: Select [Fan]
Then click [Add].

Model

The heat dissipation of the heat source inside the case is calculated.

A fan and a vent are set on the case.

Body Attributes and Materials

Body Number/Type	Body Attribute Name	Material Name
3/Solid	Source	Si
5/Solid	Case	001_Al *
6/Solid	Fan	000_Air *
7/Solid	Air	000_Air *

* Available from the material DB

Body Attribute Name

Tab

Setting

Fan

Fluid

Inflow and Outflow Faces are set to the both sides of the circular model.

Fluid Body Type: Specify flow

Inlet/Outlet Type: Fan

P-Q Characteristics

Number	Volumetric Flow Rate (Q) [m3/s]	Differential Pressure (P) [Pa]
1	0	30
2	0.2	0

Boundary Condition

Boundary Condition Name/Topology

Tab

Boundary Condition Type

Setting

Outer Boundary Condition

Fluid-Thermal

Inlet/Outlet

Natural Inflow/Outflow

Inflow Temperature: Use ambient temperature (25 [deg])

Results

The calculation was terminated by the monitoring values for convergence judgment before the residual converges.

Below are the transitions of the volumetric flow rate of the fan and the maximum temperatures of each body attribute that are predetermined as monitoring values.

(Displayable by clicking Check Convergence Status button in the dialog box after the analysis finishes)

Since the results are almost constant, it can be interpreted to be acceptable to terminate the calculation before the residual fully converges.

The figure below shows the streamlines and the contours of temperature distribution of the heat source at the same time. The contour field of the case is hidden.

The air flows into the case from the vent and flows out through the fan.

The operating point of the fan can be viewed in the result table.

By displaying on the graph, the operating point can be located on the P-Q characteristic.