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Air Cooling System with a Centrifugal Blower Disclosure Number: IPCOM000115166D
Original Publication Date: 1995-Mar-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 4 page(s) / 117K

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Benck, JW: AUTHOR [+5]


Disclosed is a cooling system, for use in a personal computer, including a centrifugal blower providing improved air delivery at reduced noise levels.

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This is the abbreviated version, containing approximately 52% of the total text.

Air Cooling System with a Centrifugal Blower

      Disclosed is a cooling system, for use in a personal computer,
including a centrifugal blower providing improved air delivery at
reduced noise levels.

      A small personal computer systems is typically cooled with air
drawn in through multiple inlet regions, by a single DC axial-flow
fan, to be exhausted through a single exhaust area.  The airflow
provided by this type of fan is significantly affected by the
increased backpressure resulting from high-density mechanical
packaging.  In high-density packaging, axial fans are also quite
noisy, with prominent discrete tones occurring mainly because of poor
inlet flow conditions resulting from the close proximity of
components obstructing the inlet area.  Furthermore, typically 30 to
40 percent of the air passes through the system without being used
for cooling, because of multiple air inlets, air leaks, and the
single exhaust port configuration.

      In an improved cooling system for a personal computer, a
centrifugal blower is used to provide support for much higher
backpressures than the conventional axial-flow fan.  In the
centrifugal blower, greater energy transfer occurs per unit of mass
flow, due to the increase in rotational energy as the fluid moves
from the hub to the tip of the impeller.  An acoustic advantage is
provided through the use of a centrifugal blower, since a properly
designed centrifugal blower typically does not exhibit pure tones,
which may be annoying to users of computer equipment.  On the other
hand, axial-flow fans are very prone to exhibiting tonal problems in
electronic packaging where sufficient clearances for airflow cannot
be provided due to space constraints.  This difference can be
understood by considering the extreme vortex stretching which occurs
as air flow is ingested into a centrifugal blower, providing a
mechanism which acts to reduce the intensity of turbulence seen by
the impeller.  There is no such reduction in an axial-flow fan.
Furthermore, centrifugal blowers tend to demonstrate lower specific
sound power than axial-flow fans.

      Fig. 1 is a schematic left side view of a computer system
having this improved cooling system.  Major components of the left
side portion are the DASD (Direct Access Storage Device) compartment
12, in which hardfiles 14 and other storage devices are mounted, a
power supply 16, and a main cooling blower 18.

      Fig. 2 is a schematic front view of the computer system of Fig.
1.  The DASD compartment 12 is separated from a CEC (Central
Electronic Complex) compartment 20, which includes a planar board 22
and feature cards 24, by means of a central baffle pl...