Home / Examples / Coupled Analysis / Fluid-Thermal Analysis [Bernoulli/Watt] / Example 21: Blower Fan

Example 21: Blower Fan

General

• Create a blower fan model to perform fluid-thermal analysis.
  

• Air is fed from the high-temperature domain to the low-temperature domain by a centrifugal fan. The resulting temperature distribution is calculated.
  

• The results from constant flow-rate air are shown below.
  Analysis model with PQ characteristics set is also included in the project file.
  

• The analysis can be performed with other fans of different sizes by changing parameters.
  

• 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	Fluid Analysis [Bernoulli] Thermal Analysis [Watt]
Analysis Type	Fluid Analysis: Steady-state Analysis Thermal Analysis: Steady-state Analysis
Laminar Flow/Turbulent Flow	Select Turbulent Flow
Flow Type	Select External Flow.
Convergence Judgment by Monitored Value	Fluid-Thermal Analysis tab: Detailed Settings Select [Convergence Judgment by Monitored Value] Click the [Automatic Monitoring Setting button and then the monitoring settings of pressure and temperature are registered.

Model

A cylindrical solid body and a rectangular solid body are combined. A shape of intake is imprinted on the surface, and a centrifugal fan is created. (Segment Face (delete Tool) is used among modification operations)

Dimensions are input using the following variables.

By changing the values of variables, the dimensions can be changed.

 

Variable	Value	Notes
H_fan	20	Height of fan
L_fan	76	Width of fan
W_fan	70	Length of fan
L2_fan	25	Width of exhaust
Phi_intake	40	Outer diameter of intake
Phi2_intake	10	Inner diameter of intake
dL_intake	-6	Lateral center position of intake
dW_intake	-1	Longitudinal center position of intake
t	1	Height of plate
L	400	Edge length of air domain
mesh_fan	L_fan/10	Mesh size of fan

 

Hollow out the intake shape from a plate with a thickness of t and an edge length of L to create the plate body.

Create an air body with an edge length of L such as it covers the whole fan model.

The air body is divided into upper and lower bodies in order to change the temperature of the air inflowing from the lower domain beneath the plate body.

Set the boundary condition [Hot_Inlet] to the surfaces of the lower air body.

 

Setting of Body Attributes, Materials, and Mesh Sizes

Body Number/Type	Body Attribute Name	Material Name	Mesh Size
3/Solid	Fan	002_Polycarbonate(PC) *	mesh_fan(L_fan/10)
9/Solid	Plate	001_Al *	mesh_fan(L_fan/10
10/Solid	Air	000_Air *	-
11/Solid	Air	000_Air *	-

* Available from the material DB

 

The body Fan is set up on the fluid tab as follows.

Body Attribute Name	Tab	Settings
Fan	Fluid	Fluid Body Type: Specify flow Select inflow face (intake) and outflow face (exhaust) in the model. Inlet/Outlet Type: Specify flow rate 0.29 [m3/min]

Boundary Conditions

Boundary Condition Name/Topology	Tab	Boundary Condition Type	Settings
Hot_Inlet	Fluid-Thermal	Inlet/Outlet	Natural Inflow/Outflow Fluid Temperature: Direct Entry 30[ deg]

Set the inlet/outlet type of the outer boundary condition to natural inflow/outflow.

Since the temperature of the incoming fluid is the ambient temperature, the ambient temperature is applied In the [Ambient Setting] dialog box.

 

Results

Select intake and exhaust faces and display streamlines as shown below.

It is observed that air is drawn in from the surrounding lower domain and exhausted straight from the fan in the y-direction into the upper domain.

 

Contour diagrams of flow velocity and temperature distributions at the cross section (Z=0) are shown.

You can observe that a high-temperature fluid is exhausted in the lateral direction.