U.S. patent application number 12/319301 was filed with the patent office on 2010-07-08 for integrated blower diffuser-fin heat sink.
This patent application is currently assigned to United Technologies Corporation. Invention is credited to Scott F. Kaslusky.
Application Number | 20100170657 12/319301 |
Document ID | / |
Family ID | 42310959 |
Filed Date | 2010-07-08 |
United States Patent
Application |
20100170657 |
Kind Code |
A1 |
Kaslusky; Scott F. |
July 8, 2010 |
Integrated blower diffuser-fin heat sink
Abstract
An air-cooled heat exchange device for cooling an object such as
an electronic device generating heat during use. The device
includes a toroidal electric motor with a centrifugal blower for
directing air flow in a downward and outward direction, a heat sink
positioned to receive the air flow from the blower; and a spiral
diffuser as part of the heat sink, the diffuser having vanes for
directing the air flow spirally over the heat sink. The vanes may
include microfabricated vibrating reeds and a plurality of
microfabricated dimples on at least some of the vanes.
Inventors: |
Kaslusky; Scott F.; (West
Hartford, CT) |
Correspondence
Address: |
KINNEY & LANGE, P.A.
THE KINNEY & LANGE BUILDING, 312 SOUTH THIRD STREET
MINNEAPOLIS
MN
55415-1002
US
|
Assignee: |
United Technologies
Corporation
Hartford
CT
|
Family ID: |
42310959 |
Appl. No.: |
12/319301 |
Filed: |
January 6, 2009 |
Current U.S.
Class: |
165/80.3 |
Current CPC
Class: |
F28F 13/10 20130101;
H01L 23/467 20130101; H01L 2924/0002 20130101; H01L 2924/0002
20130101; H01L 2924/00 20130101; H05K 7/20163 20130101 |
Class at
Publication: |
165/80.3 |
International
Class: |
F28F 7/00 20060101
F28F007/00 |
Goverment Interests
STATEMENT OF GOVERNMENT INTEREST
[0001] The U.S. Government has a paid-up license in this invention
and the right in limited circumstances to require the patent owner
to license others on reasonable terms as provided for by the terms
of [Contract No. or Grant No.] ______ awarded by Defense Advanced
Research Projects Agency/Microsystems Technology Office.
Claims
1. An air-cooled heat exchange device for cooling an object,
comprising: a centrifugal blower for directing air flow in a
downward and outward direction; a heat sink base positioned to
receive the air flow from the blower; and a diffuser on the heat
sink base and in the path of the air flow from the blower, the
diffuser having vanes that are in thermal communication with the
heat sink base and that direct the air flow from the blower outward
over the heat sink base.
2. The device of claim 1, where the object being cooled is an
electronic device generating heat during use, the electronic device
being positioned in contact with the heat sink.
3. The device of claim 1, wherein the centrifugal blower is driven
by a torriodal electric motor and the downward direction is through
the center of the motor.
4. The device of claim 1, wherein the diffuser further includes
secondary vanes in the air flow channels defined by the vanes to
prevent flow separation and increase heat transfer surface
area.
5. The device of claim 1, wherein the vanes comprise a diffuser set
of vanes forming air flow channels above the heat sink extending
spirally out from the center of the heat sink.
6. The device of claim 1, wherein the diffuser further includes
vibrating reeds in the vane channels defined by the vanes.
7. The device of claim 6, wherein the vibrating reeds include a
piezoelectric component and means for actuating it to cause the
reeds to vibrate.
8. The device of claim 1, which further includes a plurality of
microfabricated surface features on at least some of the vanes to
increase heat transfer area per unit volume.
9. The device of claim 8 where the plurality of microfabricated
surface features are dimples.
10. The device of claim 1, wherein the centrifugal blower extends
downward into and is surrounded by the diffuser.
11. The device of claim 10, wherein the centrifugal blower includes
an upper hub, a lower hub, and a plurality of blades connected
between the upper hub and the lower hub.
12. The device of claim 11, wherein the lower hub includes a port
for allowing passage of air downward through the lower hub into a
space between the lower hub and the heat sink base.
13. The device of claim 11 and further comprising a toroidal
electric motor mounted on the diffuser and having a stator, a
rotor, and a central air passage, the rotor being connected to the
upper hub of the centrifugal blower.
14. A method of cooling an object using an air-cooled heat
exchanging device, comprising the steps of: directing air flow in a
downward and outward direction using a blower; and directing the
air flow through a diffuser in thermal communication with a heat
sink base positioned to receive the air flow from the blower and
directing it outward over the heat sink base.
15. The method of claim 14, wherein the object being cooled is an
electronic device generating heat during use, the electronic device
being positioned in contact with the heat sink.
16. The method of claim 14, wherein the centrifugal blower is a
torroidal electric motor and the downward direction is through the
center of the motor.
17. The method of claim 14, wherein the diffuser vains comprises a
set of vanes forming air flow channels above the heat sink
extending radially out from the center of the heat sink.
18. The method of claim 17, which further includes secondary vanes
on the outer ends of the vanes to prevent separation of airflow and
increase heat transfer surface area.
19. The method of claim 17, which further includes vibrating reeds
in the flow channels.
20. The method of claim 19, wherein the vibrating reeds include a
piezoelectric component for causing the reeds to vibrate.
21. The method of claim 17, which further includes a plurality of
microfabricated surface features on at least some of the vanes to
increase heat transfer area per unit volume.
22. The method of claim 21 where the plurality of microfabricated
surface features are dimples.
Description
BACKGROUND
[0002] The present invention relates to air-cooled heat-exchange
systems used to remove heat from electronic devices that generate
heat during operation.
[0003] Over the past 40 years, many electronic technologies such as
telecommunications, and active sensing and imaging have undergone
tremendous technological innovation. During this same time, the
technologies, designs and performance of air-cooled heat exchangers
has remained fundamentally unchanged. Performance data for present
day heat exchangers and blowers is based on that old
technology.
[0004] Because of the improved performance and increased power
consumption of electronic technologies, heat rejection systems have
grown in size, weight, complexity and cost. In some instances,
conventional air-cooled heat sinks have become inadequate. This has
resulted in more exotic liquid-cooled manifolds, spray-cooled
enclosures, and vapor-compression refrigeration being proposed. All
these newly proposed cooling approaches add complexity associated
with operation of active pumps and compressors, as well as the need
to prevent fluid or vapor leakage. Reliability of those approaches
has not been demonstrated at this time.
[0005] Conventional designs rely on high heat transfer impingement
flows generated by axial fans placed above the heat sink. Airflow
at the fan outer diameter passes over a portion of the available
heat transfer area, thus requiring high airflow rates and high fan
power input.
SUMMARY
[0006] An integrated centrifugal blower-diffuser with a vaned
heat-sink provides cooling of electronics and other devices that
generate heat during use. Airflow is introduced radially onto the
heat sink such that the centrifugal blower and fin-diffuser direct
the bulk of the airflow outward across the available heat transfer
area of the device. Air is induced through space in the shaft of an
electric motor, and the air is then accelerated centrifugally
through a set of rotating impellor vanes, and then diffused
radially through a set of radial heat sink fins. The radial heat
sink fins form the spiral diffuser fins (or vanes) to provide
pressure recovery within the heat sink. This enables tight
intra-vane spacing and increased heat transfer surface area.
[0007] The device may also include passive vanes, surface features
and microfabricated active elements to provide heat transfer
enhancement at reduced air flow rates, thus providing reduced
thermal resistance of the heat sink device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a perspective view of an integrated blower and
diffuser.
[0009] FIG. 2 is a partially cut away view of the devices in FIG.
1.
[0010] FIG. 3 is a side sectional view of the device in FIG. 1.
[0011] FIG. 4 is a top section view of the device in FIG. 1.
[0012] FIG. 5 is a view showing stationary vanes and active fin
elements of the device shown in FIG. 1.
DETAILED DESCRIPTION
[0013] Air cooling system 10 for cooling component C is shown in
FIG. 1. System 10 includes motor 11, blower 13, cover 14, diffuser
15 and heat sink base 17. The heat sink base 17 may be an integral
part of system 10, or it may be part of component C being cooled.
In FIG. 1, the diffuser 15 also functions with heat sink base 17 as
part of a heat sink. The motor 11 and blower 13 are integral and
are mounted on cover 14, which also serves as the top of the
diffuser 15 and supports all of the elements between cover 14 and
heat sink base 17. System 10 cools objects it is in heat transfer
contact with, such as an electronic device shown generically as
component C. Any object generating heat can be cooled by system 10
if it can be placed in heat transfer contact therewith.
[0014] Motor 11 is shown as a toroidal electric motor with a
central airway 12 around its rotational axis. Air is drawn by
rotation of blower 13 axially down through central airway 12 into
blower 13 and then into diffuser 15. Air flows outward. Other
motors may also be used, with different configurations and sources
of power, depending on the size and shape of the object to be
cooled. Controller 31 provides a source of energy via line 29 to
drive motor 11 and other active components described below. In
operation, motor 11 causes air to be drawn into central airway 12
by blower 13, passing through a central aperture in cover 14 into
diffuser 15. The air flows through diffuser 15 and in contact with
heat sink base 17 to cool component C. Airflow through diffuser 15
can be radial, spiral or diffuser 15 can be configured for other
paths.
[0015] As seen in FIG. 2, the internal components of system 10 are
shown. Motor 11 includes a housing 11a, bearings 18, permanent
magnet rotor 19, stator 20, and stator windings 20a to support
rotation of the rotor 19 and blower 13. Stator winding 20a are
positioned to receive electrical power from controller 31 and drive
the blower 13 in a normal electric motor fashion.
[0016] Blower 13 has an upper hub 13a, lower hub 13b and blades 16.
Upper hub 13a is connected to the permanent magnet rotor 19. Blades
16 have an upper end 16a connected to lower hub 13b. A center port
13c in lower hub 13b provides a passage for air flow through lower
hub 13b and into space between lower hub 13b and heat sink base
17.
[0017] Diffuser 15 includes a plurality of fins or vanes 23 and
other elements shown and described below that take air from central
passage 12 so that air contacts the vanes 23 and the heat sink base
17 to absorb heat into the air and out of system 10. Diffuser 15
serves two purposes in this device. First, diffuser 15 deflects the
flow of air from a vertically downward direction radially outward
as will be described below, Second, the diffuser vanes 23 provide
additional heat conductive material as part of the heat sink 17, so
that more hot metal is exposed to the cooling air flow. This is a
significant improvement over conventional designs that simply
direct the air flow axially to impinge on a heat sink. The motor
11, blower 13, diffuser 15 and heat sink 17 are attached together
to form a single device that can be attached to an electronic
package such as a circuit board in the same manner that
conventional air-cooled heat-exchangers are attached.
[0018] Air flow in FIG. 3 is pulled down into system 10 central
airway 12 by blower blades 16 into a radial direction. This air
passes through the channels formed by vanes 23, transferring heat
from the heat sink 17 and from vanes 23 into the air as it flows
out of system 10, and, accordingly, cooling the object on which
heat sink 17 is positioned. Vanes 23 are made from heat conductive
materials such as metals. Aluminum and copper vanes are effective
conductors. System 10 is compact and yet provides a great increase
in the surface area of the heat sink.
[0019] FIG. 4 is another view of the relationship of the blower
blades 16, the heat sink base 17 and the vanes 23, and illustrates
the spiral configuration of the vanes 23. Air is drawn by blower
blades 16 through central passage 12 and down into the diffuser 15.
Diffuser 15 also include secondary vanes or splitter plates 23a and
23b at the ends of the channels formed by vanes 23 and mounted on
vanes 23 to narrow the channel and further disrupt air flow and
improve heat transfer. Also seen in FIG. 4 are a plurality of posts
25 that support reeds 27 for further disruption of the air flow and
thus further heat transfer and cooling. Posts 25 are supported
between cover 14 and heat sink base 17. Reeds 27 may be passive or
active, as described below.
[0020] In addition to the basic flow pattern as seen in FIGS. 3 and
4, FIG. 5 illustrates several additional ways to improve the
cooling of the device. Vanes 23 have been further modified to
decrease fin-to-air heat transfer resistance by the use of
microfabricated dimples 24, seen in FIG. 5. Dimples 24 are created
through a bipolar anodization process that has been shown to
enhance air side heat transfer by from about 10% to about 30% over
undimpled vanes. Other method of putting dimples 24, or other
surface irregularities can be used.
[0021] FIG. 5 also illustrates the placement of vanes 23 with
respect to splitter plates 23a and 23b to provide a larger quantity
of heat conductive material in contact with the flowing air. The
splitter plates 23a and 23b of vane 23 decrease the channel width.
This increases the resistance to flow and increases heat transfer.
Splitter plates 23a and 23b are made from heat conductive materials
and may be made from the same or different materials as supporting
vanes 23.
[0022] In FIG. 5, two vanes 23 are shown with post 25 for mounting
reeds 27, although reeds 27 are only visible in FIG. 5 for the vane
on the left. FIG. 4 shows the plurality of vanes 23, ends 23a and
23b, posts 25 and reeds 27. Post 25 is supported by cover 14 and
heat sink base 17, as noted above. Post 25 contains a piezoelectric
component that excites reeds 27 to vibrate, or reeds 27 may be
piezoelectric elements.
[0023] Reeds 27 are designed to function as vibrating reeds in the
space between adjacent fins to further improve heat transfer. In
one embodiment, reeds 27 are formed from a silicon material having
a piezoelectric component bonded to the silicon so that when the
piezoelectric component is actuated by an electric signal in wire
29 from controller 31 in FIG. 1, the reed 27 vibrates. The signal
driving the piezoelectric component may be the same signal driving
motor 11 or it may be a different signal. The appropriate signal in
wire 29 is directed to all the reeds 27 by a printed circuit on
cover 14 to the post 25 that also has an electronic circuit printed
thereon. Hard wiring is also an alternative method for exciting the
piezoelectric component. Vibrating reed 27 introduces a high
frequency, unsteady flow within the channels formed by fins 23 that
greatly enhances air mixing and heat transfer from the fin wall 23
to the air flowing through them. Use of vibrating fins or reeds 27
has been shown to increase heat transfer coefficients downstream by
more than 50% with only a negligible increase in the power
requirement and pressure drop.
[0024] The combination of dimples 24 on vanes 23, splitter plates
23a and 23b, and the vibrating reeds 27 function as highly
integrated active fin, and operate through the introduction of high
frequency, unsteady flow within the channels formed by them. This
greatly enhances mixing and heat transfer from their walls to the
air. This well-mixed air is swept through the thus formed channels
by the bulk airflow provided by the blower 13.
[0025] A simulated comparison between the present system described
above and in the figures and a conventional air-cooled exchanger
system shows significant improvement achieved by the present
invention.
[0026] A conventional device has a thermal resistance of
0.2.degree. C./W, which gives a temperature rise of 230.degree. C.,
which is above the allowed operating temperature of many electronic
devices. The system of this invention is estimated to have a
thermal resistance of 0.05.degree. C./W, resulting in a theoretical
temperature rise of only 50.degree. C. The system would be usable
with many more electronic devices. The Coefficient of Performance
(COP) is the electronic device power dissipation divided by the
blower and heat sink power. For the conventional system, the COP is
100. Simulated results for the system of this invention is
estimated to produces a COP of as low as 30, which results in an
estimated power consumption reduction of more than a factor of
three. These results are due to the substantial reduction in the
airflow and increasing the back-pressure on the blower. This
significantly improves operating point efficiency as well as
providing a reduction in thermal resistance.
[0027] Although the present invention has been described with
reference to preferred embodiments, workers skilled in the art will
recognize that changes may be made in form and detail without
departing from the spirit and scope of the invention.
* * * * *