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TITLE : HOTBOX EXAMPLE : THERMAL ANALYSIS OF PC DESKTOP ENCLOSURE

 BY : CHAM Development Team - F Liu DATE : 1999 FOR : Demonstration Case PHOENICS Version : HOTBOX VR
 NOTES : Three-dimensional, steady flow, forced convection, conjugate heat transfer, Cartesian computational grid

Description of the problem:

• The unit is of typical PC desktop enclosure (mini tower case), consisting of a CPU mounted on the motherboard, a power unit with single fan, two drive bays, two add-in cards and two vents. click here to see Overall view of the PC desktop
• Ambient air is extracted through the top vent by the fan, passing through the power supply unit, cooling over the CPU and two add-in cards, and finally pushed out of the enclosure via the bottom vent.
• Apart from cooling by fan-driven air, the heating components mounted on boundary can exchange heat transfer with the outside, which is maintained at 25°C.
Solution procedure:

• Turbulence is modelled by the LVEL method;
• Buoyancy effect is included using Boussinesq approximation;
• The heat exchange with the outside is estimated by presumed convective heat exchange coefficients;
• Different constant total heat flux is added to each heating component; and
• Material properties are imported from the built-in Property library.
Results:

All the pictures as shown below are created via the Virtual Reality Graphic Interface, a strong feature of HOTBOX-VR.

From the figures above, the majority of air flow passes the power supply unit, the CPU and add-in cards, while little movement is found around the drive bays. This design is probably justified if the heat output from the drive bays is relatively smaller, which could be found out from the temperature contours.

It is clearly seen in this case, the CPU is the hottest component, while the temperatures around and inside disk drives are relatively lower despite of little air cooling.

3. Streamlines
A set of streamlines originating at the top vent

Conclusions:

• This simplified case demonstrates how HOTBOX-VR analyses thermal performance within a PC desktop;
• LVEL model as an unique feature of HOTBOX-VR delivers both physically plausible and computationally economic simulations of turbulence flows; and