FLAIR Tutorial 6: A fan mounted at the boundary of a cabinet

This case shows how to activate the "Fan Operating Point" option for a single fan mounted at the boundary of a cabinet as shown below.

Setting up the model

Start FLAIR with the default room

• Click FLAIR icon (a desktop shortcut created by the FLAIR installation program); or
• Start the VR-Editor by clicking on 'Start', 'Programs', 'FLAIR', then 'FLAIR-VR'.
• Click on the 'File' button and then select 'Start new case', followed by 'FLAIR' and 'OK'.

The FLAIR VR-Environment screen should appear, which shows the default domain with the dimensions 10mx10mx3m.

Set the cabinet size

• On the control panel

Change the X size to 0.5m

Change the Y size to 0.5m

Change the Z size to 0.7m

• Click on "Reset" button, on the movement panel, then click "Fit to window" and then the 'OK' button.

Adding objects to the cabinet

a. add the top vent

• Click on the 'Object' menu and select 'New' (New Object) on the 'Object management' dialog box to bring up the 'Object specification' dialog box

• Change name to 'VENT'.
• Click on the 'Size' button and set 'Size' of the object as:

X: 0.3 m

Y: 0.2 m

Z:0.0 m

• Click on the 'Place' button and set 'Position' of the object as:

X: 0.1 m

Y: 0.15 m

Z: 0.7 m

• Click on 'General' button and Define 'TYPE': 'OPENING'.
• Click on 'Attributes', set External Temperature to 'User-Set' and then set the external temperature to 20 degree C
• Click on 'OK' to return to the object specification dialog box. Click 'OK' again.

b. add the fan object:

• Click on the 'Object' menu and select 'New' (New Object) on the 'Object management' dialog box to bring up the 'Object specification' dialog box

• Change name to 'FAN'.
• Click on the 'Size' button and set 'Size' of the object as:

X:0.2 m

Y:0.0 m

Z:0.3 m

• Click on the 'Place' button and set 'Position' of the object as:

X: 0.15 m

Y: 0.0 m

Z: 0.2 m

• Click on 'General' button and Define 'TYPE': 'FAN'.
• Click on 'Attributes' button to bring up the attributes dialog
• Change the Fan 'Velocities' Method to Fan 'Flow Rate' and then the Rate to 0.025 m3/s.
• Change the Temperature to 20 degree C.
• Change 'Include in matching' to YES.
• Click 'Fan Type' and select FAN1 from the list. We will check FAN1 data later.
• Click on 'OK' to return to the object specification dialog box.
• Click on 'Shape' button
• Click on 'Geometry' selection
• Select 'fan' from d_object/public/equipmt and then click on 'save' button to return to the object specification dialog box. Click 'OK' again.

c. add the first chip

• Click on the 'Object' menu and select 'New' (New Object) on the 'Object management' dialog box to bring up the 'Object specification' dialog box

• Change name to 'CHIP1'.
• Click on the 'Size' button and set 'Size' of the object as:

X:0.05 m

Y:0.07 m

Z:0.02 m

• Click on the 'Place' button and set 'Position' of the object as:

X: 0.15 m

Y: 0.15 m

Z: 0.35 m

• Click on 'General' button
• Click on 'Attributes' button to bring up the attributes dialog
• Change 'Types' to 'Solids'
• Change the Material to 100 ALUMINIUM at 27 deg C.
• Change the Energy source to 'Fixed Heat Flux' and 'Total Heat Flux'
• Change the Value to 0.5 W
• Click on 'OK' to return to the 'Object specification' dialog box
• Click on 'OK' to close the Object specification' dialog box

d. add the second chip by duplicating CHIP1

• Highlight the CHIP1 object on the 'Object management' dialog box
• Click on the 'Duplicate object or group' button and then refresh the 'Object management' dialog box
• Double click on the newly duplicated object to bring up the 'Object specification' dialog box
• Change the name to CHIP2
• Click on the 'Place' button and set 'Position' of the object as:

X: 0.3 m

Y: 0.15 m

Z: 0.35 m

• Click on 'General' button
• Click on 'Attributes' and change the total heat flux value to 0.7
• Click on 'OK' to return to the attributes dialog
• Click on 'OK' to close the Object specification dialog

e. add the PCB

• Click on the 'Object' menu and select 'New' (New Object) on the 'Object management' dialog box to bring up the 'Object specification' dialog box

• Change name to 'PCB'.
• Click on the 'Size' button and set 'Size' of the object as:

X:0.3 m

Y:0.3 m

Z:0.01 m

• Click on the 'Place' button and set 'Position' of the object as:

X: 0.1 m

Y: 0.1 m

Z: 0.34 m

• Click on 'General' and select PCB from the list of geometry type
• Click 'OK' to return to Object Management Box

Now we have 5 objects listed in the 'Object management' dialog box as shown below

To activate the physical models

a. The Main Menu panel

• Click on the 'Main Menu' button. The top page of the main menu will appear on the screen.
• Click on the 'Title' dialogue box. Type in 'A cabinet with a fan'.

To activate 'K-E' turbulence model

• Click on 'Models' to obtain the Model menu page.

FLAIR always solves pressure and velocities. The temperature is also solved as the default setting.

The 'Models' page of the Main Menu.

• Click on the 'Turbulence models' button to bring up a list of available turbulence models. Select the 'KEMODL' from it.
• Click on 'OK'.

to activate 'Fan operating point' option

• Change 'Fan operating point' option from 'OFF' to 'ON' with default settings

• Click on 'Settings' for 'Fan operating point', then click 'Edit' on the next dialog. The fandata file will be opened in the default file editor. Scroll down to FAN1, and check that the settings are as shown below:

FAN1
5
0.  8.
25.  6. 
50.  4. 
75.  2.
100  0. 

• Save the file and exit.

To set the grid numbers and to solver parameters

• Click on 'Geometry'
• Set the number of cells:

in X-direction to 20 cells

in Y-direction to 20 cells

in Z-direction to 30 cells

• Click on 'OK' to apply the changes, and click on 'Top Menu' and 'OK' to close the Grid mesh Settings.

You can click on the 'Mesh toggle' button on the main control panel to view the grid distribution on the screen as shown below.

• Click on main 'Menu', on 'Numerics', then set the 'Total number of iterations' to 200
• Click on "Top menu"
• Click on 'Output', then set 'Mornitor-cell location' to

IXMON = 9; IYMON = 9; IZMON = 18

• Click on 'Top Menu' and then 'OK' to close the top panel.

Running the Solver

To run the PHOENICS solver, Earth, click on 'Run', then 'Solver', then click 'OK' to confirm running Earth. Select 'YES to all' on Geometry Replacement Window. These actions should result in the PHOENICS Earth monitoring screen.

As the Earth solver starts and the flow calculations commence, two graphs should appear on the screen. The left-hand graph shows the variation of solved variables at the monitoring point that was set during the model definition. The right-hand graph shows the variation of errors as the solution progresses.

To the end of the calculation, the monitoring display would be as shown below.

Viewing the results

• Click on the 'Run' button, then on 'Post processor', then 'GUI Post processor (VR Viewer)' in the FLAIR-VR environment.
• When the 'File names' dialog appears, click 'OK' to accept the current result files. You may use the 'Object management' dialog box to hide some of objects.
• Click on the 'V' (Select velocity) button, followed by the 'Vector toggle' button, . You will see the velocity vector displaying on X plane. Moving the X-position to 0.25m, you will see the following picture on the screen.

• Click on 'Velocity toggle' button to clear the velocity vectors
• Click on 'Slice direction Z' button and move the probe position to Z =0.36
• Click on 'Select temperature' toggle, and click on 'Contour toggle' button, . The following picture will appear.

• Use 'File' menu and select 'Open file for Editing' and 'Result (output file)' to open the result file.
• Near the end of the result file, you will find information about the operating point of your fan-system as follows.

Final result: Operating point data
System mass flow rate: 6.2970E+01 kg/h
Fan Name: FAN Fan Type: FAN1
FAN mass flow rate:    1.1642E+02 kg/h
FAN volume flow rate:  9.7896E+01 m^3/h
FAN velocity:          2.4494E-01 m/s
FAN pressure drop:     1.6825E-01 Pa 

Saving the case

Once a case has been completed, it can be saved to disk as a new Q1 file by 'File - Save working files'. The Q1 and associated output files can be saved more permanently by 'File - Save as a case'.