U.S. patent application number 10/579466 was filed with the patent office on 2007-04-12 for series fans with flow modification element.
Invention is credited to Howard Harrison.
Application Number | 20070081888 10/579466 |
Document ID | / |
Family ID | 34623142 |
Filed Date | 2007-04-12 |
United States Patent
Application |
20070081888 |
Kind Code |
A1 |
Harrison; Howard |
April 12, 2007 |
Series fans with flow modification element
Abstract
A series fan assembly has a primary fan, a flow modification
element to reduce swirl, and a secondary fan, mounted in a series
configuration. A connecting sleeve directs the combined output into
an enclosure containing components to be cooled, or a heat sink. A
sliding drawer is configured within said connecting sleeve to
detachably hold said primary fan, said flow modification element,
and said secondary cooling fan, allowing for the hot swappable
replacement of defective components. A controller is in
communication with a power source, said primary fan, said secondary
fan, and at least one sensor monitoring the status of each of said
primary fan and said secondary fan. Said controller is configured
to maintain said combined output above a minimum control level at
all times, in the event of the failure of said primary fan or said
secondary fan.
Inventors: |
Harrison; Howard; (ONTARIO,
CA) |
Correspondence
Address: |
Distributed Thermal Systems Ltd.
2914 South Sheridan Way
Suite 100
Oakville
ON
LGT7L8
CA
|
Family ID: |
34623142 |
Appl. No.: |
10/579466 |
Filed: |
November 18, 2004 |
PCT Filed: |
November 18, 2004 |
PCT NO: |
PCT/CA04/01928 |
371 Date: |
May 17, 2006 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60520676 |
Nov 18, 2003 |
|
|
|
60520678 |
Nov 18, 2003 |
|
|
|
Current U.S.
Class: |
415/47 ;
257/E23.08; 257/E23.099 |
Current CPC
Class: |
H05K 7/2019 20130101;
F04D 29/601 20130101; H01L 23/34 20130101; F04D 25/166 20130101;
F04D 29/666 20130101; F04D 19/007 20130101; F04D 29/541 20130101;
F04D 29/547 20130101; H01L 23/467 20130101; G06F 1/20 20130101;
G06F 1/206 20130101; H01L 2224/49171 20130101; H01L 2924/3011
20130101; F04D 27/008 20130101; F04D 29/582 20130101 |
Class at
Publication: |
415/047 |
International
Class: |
F04D 15/00 20060101
F04D015/00 |
Claims
1. A series fan assembly comprising: a) A primary fan; b) A
secondary fan; in series with said primary fan; c) A flow
modification element; configured to reduce swirl and mounted
between said primary fan and said secondary fan; d) A connecting
sleeve, wherein said connecting sleeve directs the output of said
primary fan through said flow modification element and into said
secondary fan.
2. A series fan assembly as claimed in claim 1, wherein said
connecting sleeve further directs the combined output of said
primary fan and said secondary fan into an enclosure containing
components to be cooled;
3. A series fan assembly as claimed in claim 1, wherein said series
fan assembly is configured to maintain the combined output of said
primary fan and said secondary fan above a minimum level at all
times, in the event of the failure of said primary fan or said
secondary fan.
4. A series fan assembly as claimed in claim 1 further comprising
more than two fans connected in series, each separated by a
distance and an appropriate said flow modification element.
5. A series fan assembly as claimed in claim 1 wherein said flow
modification element is a filter.
6. A series fan assembly as claimed in claim 1 wherein said flow
modification element is a heat exchanger.
7. A series fan assembly as claimed in claim 1 wherein said flow
modification element is an electromagnetic shield.
8. A series fan assembly as claimed in claim 1 wherein said
secondary fan is mounted a distance from said flow control element
to reduce acoustic noise.
9. A series fan assembly as claimed in claim 1 wherein said flow
modification element is comprised of a series of vanes or tubes
configured coaxially with said primary fan and said secondary
fan.
10. A series fan assembly as claimed in claim 1 wherein said flow
modification element is comprised of a series of vanes or tubes
configured to create a spiralling laminar flow of air over the
fixed blades of said primary fan or said secondary fan when
defective.
11. A series fan assembly as claimed in claim 1 wherein said flow
modification element is comprised of a series of tubes with an air
funnel at each entry point, said air funnels opening towards and
skewed towards the source of the airflow as it comes off the blades
of said primary fan.
12. A series fan assembly as claimed in claim 1 wherein the fan
blades of said primary fan and the fan blades of said secondary fan
may be configured with adjustable pitch to return to a low airflow
impedance position when locked.
13. A series fan assembly as claimed in claim 1 wherein said
primary fan and said secondary fan both normally operate at less
than full rotating speed.
14. A series fan assembly as claimed in claim 1 wherein the
rotating speed of said primary fan or said secondary fan may be
increased to compensate for the failure of another fan.
15. A series fan assembly as claimed in claim 1 wherein two or more
such series fan assemblies may be mounted in parallel to provide
greater performance and fault tolerance.
16. A series fan assembly as claimed in claim 1 further comprising
an indicator means to alert an operator regarding the location and
status of a faulty component.
17. A series fan assembly as claimed in claim 1 further comprising
a physical means to prevent the accidental reverse installation of
said primary fan, said flow modification element, or said secondary
fan.
18. A series fan assembly as claimed in claim 1 wherein said
primary fan and said secondary fan may rotate in the same or
different directions.
19. A series fan assembly as claimed in claim 1 wherein said
primary fan and said secondary fan may have the same or different
capacity ratings.
20. A series fan assembly as claimed in claim 1 wherein said
primary fan and/or said secondary fan may have an integrated stator
on the outlet side.
21. A series fan assembly as claimed in claim 1 wherein the
direction of flow of said combined output remains consistent in the
event of a failure of said primary fan or the failure of said
secondary fan.
22. A series fan assembly as claimed in claim 1 further comprising
a means to attach said connecting sleeve to said enclosure.
23. A series fan assembly as claimed in claim 1 further comprising
sensors attached to said primary fan and said secondary fan, and
capable of predicting the impending failure of said primary and
said secondary fan.
24. A series fan assembly as claimed in claim 1 wherein said
connecting sleeve may be configured to accommodate a variety of
standard size fans.
25. A series fan assembly as claimed in claim 1 wherein said
connecting sleeve may be configured with octagonal corners or other
internal features capable of flow modification.
26. A series fan assembly as claimed in claim 1 wherein said
connecting sleeve and said flow modification element may be
configured as a independent module to be later attached to a
variety of standard size fans.
27. A series fan assembly as claimed in claim 1 further comprising
shims to allow the installation of less than maximum capacity
standard sized fans, said shims being installed with said primary
fan or said secondary fan to hold it securely in place; wherein
said shims may be removed at any time to allow said primary fan or
said secondary fan to be upgraded.
28. A series fan assembly as claimed in claim 1 wherein said
primary fan and said secondary fan form an integral part of said
connecting sleeve.
29. A series fan assembly as claimed in claim 1 wherein said
connecting sleeve is adapted to direct a flow of air into a heat
sink.
30. A series fan assembly as claimed in claim 1 wherein said
connecting sleeve is adapted to mount obliquely on the cooling fin
surface of a heat sink and to direct an impingement flow of air
into said heat sink.
31. A series fan assembly as claimed in claim 1 further comprising
a controller, wherein said controller is configured to maintain
said combined output above a minimum control level at all times, in
the event of the failure of said primary fan or said secondary
fan.
32. A series fan assembly with baffles comprising: a) A primary
fan; b) A secondary fan; in series with said primary fan; S c) A
flow modification element; configured to reduce swirl and mounted
between said primary fan and said secondary fan; d) An air inlet
baffle configured to allow the free flow of air past said primary
fan in response to a failed said primary fan; e) An air outlet
baffle configured to allow the free flow of air past said secondary
fan in response to a failed said secondary fan f) At least one
sensor monitoring the status of each of said primary fan and said
secondary fan; g) A power source; h) A controller in communication
with said sensors, said power source, said primary fan, and said
secondary fan; i) A connecting sleeve, wherein said connecting
sleeve directs the output of said primary fan through said flow
modification element and into said secondary fan; said connecting
sleeve further configured to accommodate said air inlet baffle and
said air outlet baffle.
33. A series fan assembly with baffles as claimed in claim 32
wherein said connecting sleeve further directs the combined output
of said primary fan and said secondary fan into an enclosure
containing components to be cooled.
34. A series fan assembly with baffles as claimed in claim 32
wherein said controller is configured to maintain the combined
output of said primary fan and said secondary above a minimum
control level at all times, in the event of the failure of said
primary fan or said secondary fan.
35. A series fan assembly with baffles as claimed in claim 32
further comprising more than two fans connected in series, each
separated by an appropriate said flow modification element.
36. A series fan assembly with baffles as claimed in claim 32
wherein said flow modification element is a filter.
37. A series fan assembly with baffles as claimed in claim 32
wherein said flow modification element is a heat exchanger.
38. A series fan assembly with baffles as claimed in claim 32
wherein said secondary fan is mounted a distance from said flow
control element to reduce acoustic noise.
39. A series fan assembly with baffles as claimed in claim 32
wherein said flow modification element is comprised of a series of
vanes or tubes configured coaxially with said primary fan and said
secondary fan.
40. A series fan assembly with baffles as claimed in claim 32
wherein said flow modification element is comprised of a series of
vanes or tubes configured to create a spiralling laminar flow of
air over the fixed blades of said primary fan or said secondary fan
when defective.
41. A series fan assembly with baffles as claimed in claim 32
wherein said flow modification element is comprised of a series of
tubes with an air funnel at each entry point, said air funnels
opening towards and skewed towards the source of the airflow as it
comes off the blades of said primary fan.
42. A series fan assembly with baffles as claimed in claim 32
wherein the fan blades of said primary fan and the fan blades of
said secondary fan may be configured with adjustable pitch to
return to a low airflow impedance position when locked.
43. A series fan assembly with baffles as claimed in claim 32
wherein said primary fan and said secondary fan both normally
operate at less than full rotating speed.
44. A series fan assembly with baffles as claimed in claim 32
wherein the rotating speed of said primary fan or said secondary
fan may be increased to compensate for the failure of another
fan.
45. A series fan assembly with baffles as claimed in claim 32
wherein two or more such series fans with baffles may be mounted in
parallel to provide greater fault tolerance.
46. A series fan assembly with baffles as claimed in claim 32
further comprising an indicator means to alert an operator
regarding the location and status of a faulty component.
47. A series fan assembly with baffles as claimed in claim 32
further comprising a physical means to prevent the accidental
reverse installation of said primary fan, said flow modification
element, or said secondary fan.
48. A series fan assembly with baffles as claimed in claim 32
wherein said primary fan and said secondary fan may rotate in the
same or different directions.
49. A series fan assembly with baffles as claimed in claim 32
wherein said primary fan and said secondary fan may have the same
or different capacity ratings.
50. A series fan assembly with baffles as claimed in claim 32
wherein said primary fan and/or said secondary fan may have an
integrated stator on the outlet side.
51. A series fan assembly with baffles as claimed in claim 32
wherein the direction of flow of said combined output remains
consistent in the event of a failure of said primary fan or the
failure of said secondary fan.
52. A series fan assembly with baffles as claimed in claim 32
further comprising a means to attach said connecting sleeve to said
enclosure.
53. A series fan assembly with baffles as claimed in claim 32
further comprising sensors attached to said primary fan and said
secondary fan, and capable of predicting the impending failure of
said primary and said secondary fan.
54. A series fan assembly with baffles as claimed in claim 32
wherein said connecting sleeve may be configured to accommodate a
variety of standard size fans.
55. A series fan assembly with baffles as claimed in claim 32
wherein said connecting sleeve may be configured with octagonal
corners or other internal features capable of flow
modification.
56. A series fan assembly with baffles as claimed in claim 32
wherein said connecting sleeve and said flow modification element
may be configured as a independent module to be later attached to a
variety of standard size fans.
57. A series fan assembly with baffles as claimed in claim 32
further comprising shims to allow the installation of less than
maximum capacity standard sized fans, said shims being installed
with said primary fan or said secondary fan to hold it securely in
place; wherein said shims may be removed at any time to allow said
primary fan or said secondary fan to be upgraded.
58. A series fan assembly with baffles as claimed in claim 32
wherein said primary fan and said secondary fan form an integral
part of said connecting sleeve.
59. A series fan assembly with baffles as claimed in claim 32
wherein said connecting sleeve is adapted to direct a flow of air
into a heat sink.
60. A series fan assembly with baffles as claimed in claim 32
wherein said connecting sleeve is adapted to mount obliquely on the
cooling fin surface of a heat sink and to direct an impingement
flow of air into said heat sink.
61. A series fan assembly with baffles as claimed in claim 32
wherein said air inlet baffle and said air outlet baffle may be
configured to automatically respond to changes in relative air
pressure.
62. A series fan assembly with baffles as claimed in claim 32
wherein the position of said air inlet baffle and said outlet
baffle may be controlled by said controller.
63. A series fan assembly with baffles as claimed in claim 32
wherein said primary fan and said secondary fan are configured with
an offset yet parallel axis, wherein said axis is also parallel to
said combined output.
64. A series fan assembly with baffles as claimed in claim 32
wherein said primary fan and said secondary fan may be configured
at an angle to said parallel axis, and not necessarily in coaxial
fashion.
65. A series fan assembly with baffles as claimed in claim 32
wherein said controller is in communication with the operating
system associated with the system contained in said enclosure,
wherein said operating system may inform said controller of
upcoming changes in cooling requirements.
66. A series fan assembly with baffles as claimed in claim 32
further comprising a temperature sensor in thermal communication
with the component(s) being cooled, wherein said temperature sensor
is also in communication with said controller, and wherein said
controller may respond to changes the temperature of said
component(s).
67. A series fan drawer assembly comprising: a) A primary fan; b) A
secondary fan; in series with said primary fan; c) A flow
modification element; configured to reduce swirl and mounted
between said primary fan and said secondary fan; d) A connecting
sleeve, e) A sliding drawer configured to detachably hold said
primary cooling fan, said flow modification element, and said
secondary cooling fan; said drawer further configured to slide into
and out of said connecting sleeve; f) At least one sensor
monitoring the status of each of said primary cooling fan and said
secondary cooling fan; g) A power source h) A controller in
communication with said sensors, said power source, said secondary
fan, and said primary fan; wherein said connecting sleeve directs
the output of said primary fan through said flow modification
element and into said secondary fan.
68. A series fan drawer assembly as claimed in claim 67 wherein
said connecting sleeve further directs the combined output of said
primary fan and said secondary fan into an enclosure containing
components to be cooled;
69. A series fan drawer assembly as claimed in claim 67 wherein
said controller is configured to maintain the combined output of
said primary fan and said secondary fan above a minimum control
level at all times, in the event of the failure of said primary fan
or said secondary fan.
70. A series fan drawer assembly as claimed in claim 67 further
comprising more than two fans connected in series, each separated
by an appropriate said flow modification element.
71. A series fan drawer assembly as claimed in claim 67 wherein
said flow modification element is a filter.
72. A series fan drawer assembly as claimed in claim 67 wherein
said flow modification element is a heat exchanger.
73. A series fan drawer assembly as claimed in claim 67 wherein
said flow modification element is an electromagnetic shield.
74. A series fan drawer assembly as claimed in claim 67 wherein
said secondary fan is mounted a distance from said flow control
element to reduce acoustic noise.
75. A series fan drawer assembly as claimed in claim 67 wherein
said flow modification element is comprised of a series of vanes or
tubes configured coaxially with said primary fan and said secondary
fan.
76. A series fan drawer assembly as claimed in claim 67 wherein
said flow modification element is comprised of a series of vanes or
tubes configured to create a spiralling laminar flow of air over
the fixed blades of said primary fan or said secondary fan when
defective.
77. A series fan drawer assembly as claimed in claim 67 wherein
said flow modification element is comprised of a series of tubes
with an air funnel at each entry point, said air funnels opening
towards and skewed towards the source of the airflow as it comes
off the blades of said primary fan.
78. A series fan drawer assembly as claimed in claim 67 wherein the
fan blades of said primary fan and the fan blades of said secondary
fan may be configured with adjustable pitch to return to a low
airflow impedance position when locked.
79. A series fan drawer assembly as claimed in claim 67 wherein
said primary fan and said secondary fan both normally operate at
less than full rotating speed.
80. A series fan drawer assembly as claimed in claim 67 wherein the
rotating speed of said primary fan or said secondary fan may be
increased to compensate for the failure of another fan.
81. A series fan drawer assembly as claimed in claim 67 wherein two
or more such series fan drawer assemblies may be mounted in
parallel to provide greater fault tolerance.
82. A series fan drawer assembly as claimed in claim 67 further
comprising an indicator means to alert an operator regarding the
location and status of a faulty component.
83. A series fan drawer assembly as claimed in claim 67 further
comprising a physical means to prevent the accidental reverse
installation of said primary fan, said flow modification element,
or said secondary fan.
84. A high performance series fan drawer assembly as claimed in
claim 53 wherein said primary fan and said secondary fan may rotate
in the same or different directions.
85. A series fan drawer assembly as claimed in claim 67 wherein
said primary fan and said secondary fan may have the same or
different capacity ratings.
86. A series fan drawer assembly as claimed in claim 67 wherein
said primary fan and/or said secondary fan may have an integrated
stator on the outlet side.
87. A series fan drawer assembly as claimed in claim 67 wherein the
direction of flow of said combined output remains consistent in the
event of a failure of said primary fan or the failure of said
secondary fan.
88. A series fan drawer assembly as claimed in claim 67 further
comprising a means to attach said connecting sleeve to said
enclosure.
89. A series fan drawer assembly as claimed in claim 67 further
comprising sensors attached to said primary fan and said secondary
fan, and capable of predicting the impending failure of said
primary and said secondary fan.
90. A series fan drawer assembly as claimed in claim 67 wherein
said connecting sleeve may be configured to accommodate a variety
of standard size fans.
91. A series fan drawer assembly as claimed in claim 67 wherein
said connecting sleeve may be configured with octagonal corners or
other internal features capable of flow modification.
92. A series fan drawer assembly as claimed in claim 67 further
comprising shims to allow the installation of less than maximum
capacity standard sized fans, said shims being installed with said
primary fan or said secondary fan to hold it securely in place;
wherein said shims may be removed at any time to allow said primary
fan or said secondary fan to be upgraded.
93. A series fan drawer assembly as claimed in claim 67 wherein
said primary fan and said secondary fan form an integral part of
said connecting sleeve.
94. A series fan drawer assembly as claimed in claim 67 wherein
said controller is in communication with the operating system
associated with the system contained in said enclosure, wherein
said operating system may inform said controller of upcoming
changes in cooling requirements.
95. A series fan drawer assembly as claimed in claim 67 further
comprising a temperature sensor in thermal communication with the
component(s) being cooled, wherein said temperature sensor is also
in communication with said controller, and wherein said controller
may respond to changes the temperature of said component(s).
96. A series fan drawer assembly as claimed in claim 67 further
comprising a redundant indictor means to confirm the identity of
the faulty component, said redundant indicator means being visible
when said sliding drawer is pulled out from said enclosure.
97. A high performance series fan drawer assembly as claimed in
claim 53 wherein said sliding drawer may be pulled out from said
enclosure in a limited and controlled fashion while the system
within said enclosure is still in operation.
98. A series fan drawer assembly as claimed in claim 67 wherein
said primary fan, said flow modification element, or said secondary
fan may be replaced while said drawer is pulled out from said
enclosure and while the system within said enclosure is still in
operation.
99. A series fan drawer assembly as claimed in claim 67 wherein
said sliding drawer may be completely removed from said connecting
sleeve and said enclosure when required.
100. A series fan drawer assembly as claimed in claim 67 wherein
said controller is in communication with the operating system
associated with the system contained in said enclosure, wherein
said operating system may inform said controller of upcoming
changes in cooling requirements.
101. A series fan drawer assembly as claimed in claim 67 further
comprising a temperature sensor in thermal communication with the
component(s) being cooled, wherein said temperature sensor is also
in communication with said controller, and wherein said controller
may respond to changes the temperature of said component(s).
Description
PRIORITY
[0001] This application claims priority from U.S. 60/520,678 (High
performance Series Fan Configurations, filed Nov. 18, 2003) and
U.S. 60/520,676 (Dual Redundant Cooling Fan Sinks and Trays, filed
Nov. 18, 2003)
FIELD OF THE INVENTION
[0002] This invention relates to a unique series fan configuration
intended for cooling electronics. The configuration is modular,
extremely compact, fault tolerant, and uses readily available low
cost axial fans. A display panel may be configured to alert the
user regarding a failed fan, which may then be replaced (or "hot
swapped") without shutting down the system being cooled.
ACKNOWLEDGEMENT OF PRIOR ART
[0003] The need for highly reliable, fault tolerant, and hot
swappable cooling fans has increased as the mission critical use of
high performance electronics becomes more and more prevalent. In
many cases a loss of cooling for more than a brief moment could
damage the underlying electronic components.
[0004] This has driven a tremendous amount of inventive activity in
the field as evidenced by numerous recent patents including U.S.
Pat. No. 6,247,898 issued Jun. 19, 2001 to Henderson, et al
(assigned to Micron Electronics), U.S. Pat. No. 6,108,203 issued
Aug. 22, 2000 to Dittus, et al (assigned to IBM), U.S. Pat. No.
6,101,459 issued Aug. 8, 2000 to Tavallaei, et al (assigned to
Compaq Computer), U.S. Pat. No. 6,061,237 issued May 9, 2000 to
Sands, et al (assigned to Dell Computer), U.S. Pat. No. 6,040,987
issued Mar. 21, 2000 to Schmitt, et al (assigned to Dell), U.S.
Pat. No. 6,031,717 issued Feb. 29, 2000 to Baddour, et al (assigned
to Dell Computer), U.S. Pat. No. 6,021,042 issued Feb. 1, 2000 to
Anderson, et al (assigned to Intel Corporation), U.S. Pat. No.
6,005,770 issued Dec. 21, 1999 to Schmitt (assigned to Dell
Computer), U.S. Pat. No. 5,572,403 issued Nov. 5, 1996 to Mills, et
al (assigned to Dell Computer), and U.S. Pat. No. 5,562,410 issued
Oct. 8, 1996 to Sachs, et al (assigned to EMC Corporation),
[0005] Most of these patents, including U.S. Pat. No. 6,108,203
assigned to IBM, U.S. Pat. No. 6,101,459 assigned to Compaq, U.S.
Pat. No. 6,061,237 assigned to Dell, U.S. Pat. No. 6,031,717
assigned to Dell, U.S. Pat. No. 6,021,042 assigned to Intel, and
U.S. Pat. No. 6,005,770 assigned to Dell teach redundant fans
operating in parallel. Of these, U.S. Pat. No. 6,108,203, U.S. Pat.
No. 6,061, 237, U.S. Pat. No. 6,031,717, U.S. Pat. No. 6,021,042,
and U.S. Pat. No. 6,005,770 all teach various types of baffling to
prevent the reverse flow of air through the defective fan, and the
ensuing loss of cooling air pressure within the cabinet. U.S. Pat.
No. 6,101,459 teaches that this reverse flow of air may be
prevented by placing a second, back-up, fan in series with each of
the parallel fans. However it must be noted that this same patent
also teaches that the back-up fans remain idle until required.
These patents also suggest various ways to ease the process of
replacing the defective fan(s). U.S. Pat. No. 6,061, 237 teaches
that two parallel fans may be placed at an angle to save space.
[0006] Only two of these patents, U.S. Pat. No. 6,101,459 assigned
to Compaq and U.S. Pat. No. 5,572,403 assigned to Dell, suggest a
series configuration for the cooling fans. Of these, U.S. Pat. No.
6,101,459 teaches that the second fan in the series is for back-up
purposes only, and will remain idle until required as previously
noted. U.S. Pat. No. 5,572,403 does teach that the series
configured fans run simultaneously, in counter-rotating fashion,
and further teaches that a plenum bypass be used to reduce
impedance and increase airflow in the event of a fan failure.
However this approach requires specialized fans and also requires
further baffling within the cabinet to accommodate the plenum
bypass flow when required.
[0007] An additional two of these patents, U.S. Pat. No. 6,040,981
assigned to Dell and U.S. Pat. No. 5,562,410 assigned to EMC
address the issues of easy fan removal and hot swappable fans. U.S.
Pat. No. 6,040,981 teaches a removable fan with camming handle that
aligns the fan and re-connects power in a single operation. U.S.
Pat. No. 5,562,410 teaches a self aligning hot-pluggable fan
assembly, primarily to complement the fault tolerant characteristic
of RAID based disk arrays.
[0008] Finally, U.S. Pat. No. 6,247,898 teaches a method of
controlling the speed of a plurality of fans connected in parallel
fashion.
SUMMARY OF THE INVENTION
[0009] As taught by prior art, a currently accepted solution is to
install dual fans (or blowers) in a parallel configuration such
that one fan has the capacity to cool the entire cabinet, at least
on a minimal cooling basis. In this manner, the failure of one fan
can be tolerated without damaging the equipment. While this
approach works, the parallel installation has the following
associated problems; (1) mounting two fans side by side requires
twice as much cabinet wall space, and increases the potential for
Electro-Magnetic (EM) leakage through the fan opening, (2) the fail
over mechanism must contain sufficient baffling to prevent air from
escaping (or entering) through the defective fan, a complex and
bulky approach, (3) further baffling is required to ensure that the
air stream is directed consistently regardless of which fan is
operating, and (4) the system may need to be shut down before
replacing the defective fan.
[0010] There are benefits to mounting the fans in series rather
than in parallel--i.e. place one fan behind the other rather than
one fan beside the other. However the problem with this approach
has been that two fans in series do not perform well because the
airflow produced by the primary fan contains swirl, and this does
not match the ideal input conditions for the secondary fan. The
secondary fan must have a substantially reduced level of swirl at
its input to operate efficiently.
[0011] Despite this drawback, the series configuration solves many
of the problems associated with the parallel configuration; (1) a
series configuration takes less cabinet wall space than a parallel
configuration, and therefore reduces the potential EM leakage, (2)
no baffling is required to prevent air from escaping through the
defective fan--in fact air must flow through the defective fan in
order for the series configuration to work, (3) no further baffling
is required to ensure that the air is consistently directed since
the two fans are mounted on the same or similar axis, and (4) a
defective fan may be safely replaced or "hot swapped" without
shutting down the system or components being cooled.
[0012] Accordingly the present invention discloses a method of
reducing the swirl between the two fans by placing a flow
modification element, or diffuser element, between the two fans, so
that the above benefits can be realized. The present invention also
discloses several additional features that will contribute to
functionality, ease of use, ease of maintenance, and lower cost
such as; (1) an integrated filter/flow control element, (2) a user
interface panel to show the status of both fans and the integrated
filter element, (3) the ability to replace the filter element or
the defective fan from outside the cabinet while the system is
running, and (4) a very compact and modular device that can be
installed between two industry standard fans to create a high
performance series fan configuration. Further, the present
invention discloses many applications for high performance series
fans such as for the cooling of components, heat sinks, system
cabinets, and enclosures.
[0013] It is commonly known that an axial fan works best if it sees
laminar flow on the input side. This condition is met with a single
fan since there is nothing on the input side to generate swirl.
However this is not the case with a series configuration since the
output of the primary fan, as in the case of all axial fans,
contains swirl.
[0014] The present invention discloses that this problem may be
resolved by placing a diffuser element between the two fans. The
result of placing a diffuser element between the two fans is to
substantially reduce the swirl produced by the primary fan before
the airflow enters the secondary fan, thereby increasing the
efficiency of the secondary fan.
[0015] The use of an intermediate diffuser element will not affect
the primary inherent advantages of a series fan configuration--the
airflow will always be in the same direction, even during a fan
failure, and no baffling changes will be required within the
cabinet to re-direct the flow during a fan failure. In the event of
a primary (or input) fan failure, the secondary (or output) fan
will continue to "pull" air through the diffuser element and move
it in the same direction. Likewise air will continue to flow in the
same direction if the secondary fan fails, except that the primary
fan will "push" rather than "pull" air through the diffuser
element.
[0016] Although the direction of airflow will remain consistent in
a series fan configuration with a single fan failure, the volume of
airflow will be reduced if the remaining fan continues to operate
at the same speed. This is an acceptable situation only if the
volume of airflow does not fall below the minimum required to
dissipate the heat generated by the components being cooled. The
present invention teaches that a control system may be configured
to sense the fan failure and adjust the remaining fan speed
accordingly, in order to ensure that this minimum requirement is
met until the defective fan can be replaced. This type of control
may be easily implemented since (1) many fans today are available
with fault sensors to indicate an impending failure/total failure
and (2) fan speed can be easily controlled by controlling the input
parameters such as voltage, in the case of DC fans, or through
pulse width modulation.
[0017] The efficiency of the series fan configuration, while in
single fan failure mode, may be increased by allowing the diffuser
element to swing or slide out of the air flow, for example by
splitting the diffuser element down the middle and allowing each
half to swing out of the flow, or otherwise partially or completely
removing the diffuser element from the air flow until the defective
fan may be replaced. Further, the efficiency of the series fan
configuration, while in a single fan failure mode, may be increased
by partially or completely removing the failed fan from the
configuration until such time as it may be replaced. Further, the
efficiency of the series fan configuration, while in a single fan
failure mode, may be increased by providing a diffuser element
bypass channel configured to allow the free flow of air past the
diffuser element while in failure mode.
[0018] Should a fan fail, the present invention teaches that it may
be replaced without having to shut down the system or components
being cooled. High performance series fans may be configured as a
"sliding drawer" that can be pulled away from the cabinet without
interrupting the airflow. The defective fan may be replaced while
the drawer is in the "open" position, and then the drawer may be
returned to the "closed" position without affecting system
operation or necessitating a system shut down. The control system
will detect the new fan, and adjust speeds accordingly.
[0019] In some cases it may be possible to enhance the
functionality of the diffuser element by configuring it as a
combined filter/diffuser element, to reduce swirl and prevent
particles from entering the system being cooled, a combined heat
exchanger/diffuser element, to reduce swirl while adding or
removing heat from the airflow, a combined Electro-Magnetic (EM)
shield/diffuser element, to reduce swirl while maintaining the
integrity of the EM shield in the fan opening, or other possible
combinations. In larger applications the diffuser element may be
active rather than passive so that the flow control parameters may
be adjusted and optimized while the high performance series fan
configuration is operating.
[0020] Various configurations are possible including a tightly
coupled or modular arrangement, or a loosely coupled or push/pull
arrangement. In a tightly coupled arrangement a primary fan and a
secondary fan may be mounted at opposite ends of an air channel, in
a substantially coaxial configuration, such that the air channel
contains the diffuser element, and directs the airflow from the
output of the primary fan, through the diffuser element, and into
the secondary fan. In a loosely coupled or push/pull arrangement a
primary fan blows air into an enclosed space and a secondary fan
blows air out of the same enclosed space, and the components within
the enclosed space act as a type of diffuser element to remove
swirl from the airflow as it moves from the primary to the
secondary fan. In some loosely coupled configurations a diffuser
element may also be installed on the input side of the secondary
fan to further reduce the swirl and improve the efficiency of the
secondary fan, and baffling may be added to improve the efficiency
of the airflow within the enclosed space.
[0021] The performance of the secondary fan may be enhanced by
increasing the residual momentum and reducing the swirl component
of the airflow at its input, as previously described. The primary
fan contributes to this enhanced performance, since it increases
the residual momentum of the airflow entering the secondary fan,
however it also introduces a swirl component that is
counter-productive. An optimized high performance series fan
configuration retains a maximum level of residual momentum while
reducing swirl to an ideal level before the airflow enters the
secondary fan.
[0022] The total output of a series fan configuration, relative to
the theoretical output of a non-optimized series fan configuration
(generally considered to generate two times the static pressure for
any given CFM output), may be expressed, in simple terms, as
follows; Output.sub.T=(2.times.Outputs)+M-S (1) [0023] Where
Output.sub.T=Total output [0024] Output.sub.S=Output from single
fan [0025] M=Momentum Factor (at secondary fan) [0026] S=Swirl
Factor (at secondary fan)
[0027] The momentum factor will naturally decay as the distance
between the primary and secondary fans is increased, and as more
restrictions, e.g. a diffuser element, are placed in the airflow.
From this perspective the most effective series fan configurations
will have the least possible distance between the primary and
secondary fans, the closest co-axial alignment between the two
fans, and the least number of restrictions between the two
fans.
[0028] The swirl component will also naturally decay as the
distance between the primary and secondary fans is increased, and
from this perspective the most effective series fan configurations
will have the greatest possible distance between the primary and
secondary fans. The present invention teaches that this distance
may be substantially reduced by installing a diffuser element
between the primary and secondary fans to force a more rapid decay
of swirl, as previously described. In a loosely coupled series fan
configuration the components to be cooled may serve as a type of
diffuser element, as in the case of a computer system where the
primary and secondary fans are located at opposite ends of the
cabinet and the air flowing between them must pass over the
electronic components. Alternatively the diffuser element may be a
purpose built component placed strategically between the two fans,
or in front of the secondary fan. In either case the flow
straightening element(s) will have both a positive and a negative
effect since will it reduce the swirl component while at the same
time increasing drag.
[0029] Based on this information the model may be re-constructed as
follows; Output.sub.T=(2.times.Outputs)+M-S+(S.sub.R-D) (2) [0030]
Where S.sub.R=Swirl reduction factor [0031] D=Drag introduced by
swirl reducing components
[0032] Equation (2) may be re-written as follows to separate the
behaviour of the primary and secondary fans, and associate this
behaviour with the most closely aligned correction factor, as
observed;
Output.sub.T=(Output.sub.SP-D)+(Output.sub.SS+M-(S-S.sub.R)) (3)
[0033] Where Output.sub.SP=Output of a single primary fan [0034]
Output.sub.SS=Output of a single secondary fan
[0035] It is important to note that Output.sub.SP and Output.sub.SS
both represent the output of single fans operating in independent
fashion. It follows that Output.sub.SP and Output.sub.SS will be
the same for a symmetrical series fan configuration, where the
primary and secondary fans have identical specifications, and that
Output.sub.SP and Output.sub.SS will be different for an
asymmetrical series fan configuration, where the primary and
secondary fans may have different specifications.
[0036] Clearly, then, the optimization objectives are to
simultaneously maximize the momentum of airflow as it enters the
secondary fan (M), minimize the swirl component of the airflow as
it enters the secondary fan (S-S.sub.R), and minimize the drag
introduced by the swirl reducing components (D). In fact the output
of the secondary fan may be enhanced, in this manner, to the extent
that it exceeds Output.sub.SS, i.e. it exceeds the output of a
single secondary fan operating in independent fashion with input
conditions that meet design specifications. It follows that the
total output of a high performance series fan configuration with a
diffuser element may exceed the theoretical output of two single
fans as long as the following optimum condition exists;
M>((S-S.sub.R)-D) (4)
[0037] It has been found that an optimal condition may achieved by
(1) mounting the primary and secondary fans coaxially at either end
of a sealed air conducting tube or connecting sleeve, adapted with
internal features such as longitudinal grooves or octagonal corners
to induce natural swirl decay while maintaining the maximum level
of momentum as the air flows between the two fans, and (2) by
placing the diffuser element at a distance from the primary fan
such that a substantial amount of natural swirl decay will have
occurred before the airflow enters the diffuser element, as
depicted in FIG. 24 (with reference to the following components and
corresponding numbers for FIG. 24 only); TABLE-US-00001 Component
No. Component No. Primary Fan 200 Secondary Fan 202 Diffuser
Element 204 Seal 206 Airflow 208 Integrated Stator 210 Acoustic Gap
212
[0038] The diffuser element may be further optimized to remove
substantially all of the remaining swirl while introducing a
minimal level of incremental drag, thereby "straightening" the
airflow while maintaining its momentum at the highest possible
level as it leaves the diffuser element, and converting swirl
energy to kinetic energy with the highest possible efficiency. The
diffuser element may be placed immediately before or in close
proximity to the secondary fan in order to maintain this momentum
as the airflow enters the secondary fan, recognizing that a small
gap may be required between the diffuser element and secondary fan
to reduce the acoustical noise produced by the overall
configuration. The diffuser element and the air conducting tube may
be combined and further adapted in various ways to provide further
optimization and enhanced performance.
[0039] Further optimization may be achieved by controlling the
combined momentum and swirl at the input to the secondary fan such
that the momentum vector(s) drive the secondary fan to achieve
greater efficiency and performance. Such optimization may require a
more complex diffuser element design, optimized for efficient swirl
energy to kinetic energy conversion, directional control of the
momentum vector(s), reduced drag, and so on.
[0040] Further optimization may also be achieved by using a primary
fan with an integrated stator on the output side. In this case
Output.sub.SP will have less swirl (due to the straightening effect
of the stator) and a lower flow rate (due to the drag effects of
the stator) relative to a similar primary fan that does not have an
integrated stator. These attributes can be used to enhance the
performance of, and reduce the overall length of, a high
performance series fan configuration with diffuser element since
the requirement for swirl reduction in the area between the two
fans will have been reduced by the integrated stator on the primary
fan. However the reduced level of drag produced by the shorter air
conducting tube between the two fans, and the smaller diffuser
element, may be offset by the Incremental drag produced by the
integrated stator on the primary fan.
[0041] A closely coupled high performance series fan with diffuser
element, or dual redundant fan module, is ideally suited for the
cooling of cabinets and other enclosures. Further, the excellent
single stream performance under high static pressures makes it
ideal for the impingement cooling of CPUs and other electronic
components, as well as the impingement cooling of power heat sinks.
The latter configuration may be referred to as a high performance
series fan sink.
[0042] A loosely coupled or "push/pull" series configuration is
depicted in FIG. 25 (with reference to the following components and
corresponding numbers for FIG. 25 and FIG. 26 only); TABLE-US-00002
Component No. Component No. Primary Fan 300 Secondary Fan 302 Air
Flow In 304 Electronic Components 306 System Cabinet 308 Air Flow
Out 310
[0043] A loosely coupled series configuration may be designed to
incorporate some of these operating parameters, however it will
likely deliver sub-optimal performance relative to a closely
coupled configuration using similar fans. A loosely coupled series
configuration has a much larger distance and a much less efficient
duct between the primary and secondary fans, as illustrated below.
The result is a substantial loss of momentum before the airflow
reaches the secondary fan.
[0044] The practice of relying on the electronic and other
components to remove swirl may work to some degree, however it
would be extremely difficult to lay out the components for the
optimization of this function, and doing so may introduce
volumetric inefficiencies in the design. Further, it would be
extremely difficult to configure the components such that
substantially all of the swirl will have been removed just as the
airflow enters the secondary fan. Further, the optimized design, if
it could be achieved, would change with the addition or
modification of a single component within the air space between the
two fans.
[0045] In contrast, a tightly coupled or modular series fan
configuration operates with an optimized design that remains the
same regardless of component layout within the system cabinet being
cooled. While a change in components may affect the static pressure
or load conditions, it will not affect the optimized design of the
high performance series fan configuration. In other words the
performance curve (i.e. static pressure/flow curve) for the high
performance series fan configuration will remain the same
regardless of the change in load curves--it is just the
intersection of these curves (i.e. the operating point) that will
change. The fact that the output of an optimized high performance
series fan configuration may be plotted as a standard performance
curve greatly eases the thermal design task since the operating
point may be readily determined in the same way that one would
determine the operating point for a single fan.
[0046] It is possible to combine some of the benefits of a tightly
coupled series configuration with a loosely coupled series
configuration by placing a diffuser element immediately prior to
the secondary fan as depicted in FIG. 26 (with reference to the
following components and corresponding numbers for FIG. 25 and FIG.
26 only); TABLE-US-00003 Component No. Component No. Primary Fan
300 Secondary Fan 302 Air Flow In 304 Electronic Components 306
System Cabinet 308 Air Flow Out 310 Diffuser Element 312
[0047] The installation of a diffuser element at this point in the
loosely coupled configuration will serve to remove substantially
all of the swirl before the air enters the secondary fan, providing
an increase in efficiency as described above.
[0048] A further analysis of equation (3) above reveals that the
configuration may be more responsive to an increased level of power
applied to the secondary fan relative to the primary fan. This is
due to the fact that the impact of any incremental power applied to
the secondary fan is enhanced beyond what one would normally expect
from a single independent fan because of the increased momentum of
the air entering the secondary fan. When operating independently,
the momentum of the air flowing into and out of the secondary fan
is completely generated by the secondary fan. When operating in a
series configuration, however, the air flowing through the
secondary fan has a residual momentum that has already been
generated by the primary fan. This increases the efficiency of the
secondary fan beyond that of an independent fan.
[0049] A further observed effect is that the primary fan is more
sensitive (than the secondary fan) to the drag introduced by the
diffuser element as noted in equation (3). This also indicates that
the series configuration may be more responsive to increased power
applied to the secondary fan rather than the primary fan.
[0050] It is therefore possible to take advantage of these effects,
and increase the efficiency of the overall series fan
configuration, by re-balancing the distribution of power such that
more power is applied to the secondary fan than the primary fan.
The result will be an increased output relative to an equal
distribution of the same total power between the two fans. This
principle may be applied to tightly coupled or loosely coupled
series fan configurations. In practice it may be implemented by
supplying a higher voltage to the secondary fan than the primary
fan, or by utilizing a higher performance secondary fan and
applying the same voltage to both fans, or through some other
means.
[0051] It is important to note that although the preceding
discussion has been limited to high performance series fan
configurations with two fans, the principles taught herein may also
be applied to configurations of three or more fans in various
series combinations. As an example, a tightly coupled serial fan
module may replace the primary fan in a loosely coupled
configuration, resulting in a three (3) fan configuration with
enhanced performance.
[0052] Further, multiple high performance series fan modules may be
installed in parallel for greater airflow capacity and/or to
provide multiple fault tolerant airflows. It has been previously
noted that parallel single fan installations are not inherently
fault tolerant since the failed fan presents an air leak that
quickly disperses the pressure and airflow produced by the
remaining fan(s). In contrast, a parallel installation of two or
more high performance series fan modules is fault tolerant because
each one of the series fan modules is inherently fault tolerant.
The module that contains the failed fan will still continue to
produce airflow and pressure, thereby preventing the leakage of air
that is normally associated with a parallel fan installation. As an
added benefit, the failed fan may be replaced on a scheduled rather
than an urgent basis.
[0053] Parallel high performance series fan modules are ideal for
many applications including system cabinet cooling and rack mount
enclosure cooling. The former is particularly well suited for very
low profile 1 U and 2 U (approximately 44 mm and 88 mm in height,
respectively) server formats where the installation of larger
diameter fans is impossible and performance and fault tolerance are
essential. The latter configuration may be used to replace the
parallel single fans commonly installed on a fan tray to form a
high performance series fan tray.
[0054] A high performance series fan configuration operates in
fault mode when one fan fails, and the remaining fan continues to
create airflow. A controller may be configured to recognize and
respond to this situation by increasing the power supplied to the
remaining fan, thereby increasing the output during failure mode.
In some applications that demand improved fault mode performance a
unique offset series configuration provides a supplementary air
inlet or air outlet that may be opened in the event of a fan
failure to improve the efficiency of the remaining fan, while
maintaining a consistent direction and rate of flow
[0055] Finally, the principles taught herein may be applied to
larger fans and propellers to develop high performance fault
tolerant automotive fans, e.g. for cooling and turbo-charging,
innovative consumer products, such as vertical pole fans to
de-stratify the air within a room, high performance fault tolerant
industrial fans, e.g. for large air moving systems, propulsion
systems, where the safety associated with a fault tolerant
configuration cannot be underestimated, and other applications that
may become obvious when the principles are understood. Further, the
principles taught herein may also be applied to other gasses and
fluids, e.g. for the development of pumps and marine propulsion
systems, and other applications that may becomes obvious when the
principles are understood.
Embodiments
[0056] Embodiments of the invention are described by way of example
with reference to the drawings in which:
[0057] FIG. 1 illustrates an inefficient series fan
configuration,
[0058] FIG. 2 illustrates an efficient series fan configuration
with diffuser elements,
[0059] FIG. 3 provides an overview of a high performance series fan
configuration,
[0060] FIG. 4 provides a side view of a high performance series fan
configuration,
[0061] FIG. 5 provides a side view of a high performance series fan
in normal operation,
[0062] FIG. 6 provides a front view of a high performance series
fan with a control panel,
[0063] FIG. 7 illustrates how a high performance series fan drawer
may be withdrawn from a cabinet,
[0064] FIG. 8 details the replacement of one of the series
fans,
[0065] FIG. 9 shows how two high performance series fan modules may
be mounted in parallel,
[0066] FIG. 10 shows a high performance series fan module with a
supplementary air inlet and outlet,
[0067] FIG. 11 provides a connection diagram for a high performance
series fan controller,
[0068] FIG. 12 illustrates a control algorithm for a high
performance series fan controller in flow chart format,
[0069] FIG. 13 provides a perspective view of a high performance
series fan sink,
[0070] FIG. 14 provides a section view of a high performance series
fan sink,
[0071] FIG. 15 illustrates a high performance series fan sink with
the primary fan being replaced,
[0072] FIG. 16 illustrates a high performance series fan sink with
the secondary fan being replaced,
[0073] FIG. 17 provides a perspective view of a high performance
series fan tray,
[0074] FIG. 18 provides a second perspective view of a high
performance series fan tray showing further details of one of the
high performance series fan modules,
[0075] FIG. 19 illustrates a high performance series fan tray with
the primary fan being replaced,
[0076] FIG. 20 illustrates a high performance series fan tray with
the secondary fan being replaced,
[0077] FIG. 21 illustrates a high performance series fan tray
controller operating in a fan failure mode,
[0078] FIG. 22 illustrates a method for monitoring airflow through
a high performance series fan module, and:
[0079] FIG. 23 provides a perspective view of an alternatively
configured high performance series fan tray.
[0080] FIG. 1 illustrates an inefficient series fan configuration
with three independent axial cooling fans mounted such that the
output from one fan becomes the input to the next fan in the
series. In this case the output from primary fan 8 becomes the
input to secondary fan 16, and in like manner the output from
secondary fan 16 becomes the input to tertiary fan 17. Basic series
fan configurations may be comprised of two or more axial fans
configured in this manner.
[0081] An axial fan works best if it sees a substantially laminar
flow, i.e. a flow with no or a controlled level of swirl, on the
input side. This condition is met with a single fan since there is
nothing on the input side to generate swirl. However this is not
the case with a basic series configuration since the outputs of the
primary fan 8 and secondary fan 16 (as with all axial fans) contain
swirl as depicted by airflow with swirl 10 and second airflow with
swirl 11. Therefore a basic series configuration is inefficient
because the secondary, tertiary, and all subsequent fans will have
a substantial swirl component in the input airflow.
[0082] In contrast, FIG. 2 illustrates an efficient series fan
configuration with diffuser element 14 and second diffuser element
15 inserted between primary fan 8 and secondary fan 16, and
secondary fan 16 and tertiary fan 17, respectively.
[0083] The result of inserting diffuser element 14 between primary
fan 8 and secondary fan 16 is to convert the input seen by
secondary fan 16 from airflow with swirl 10 to reduced swirl
airflow 12, thereby increasing the efficiency of secondary fan 16
to a level approaching that of primary fan 8. Likewise, second
diffuser element 15 will convert the input seen by tertiary fan 17
from second airflow with swirl 11 to second reduced swirl airflow
13, thereby improving the efficiency of tertiary fan 17.
[0084] Diffuser element 14 and second diffuser element 15 may be
comprised, for example, of filter material or a number of vanes or
tubes mounted in the path of the air and configured to reduce swirl
and direct the airflow into downstream fan, as illustrated by
alternative second diffuser element 15a. Further, the vanes or
tubes may be configured to leave a certain level of residual swirl
in the airflow in order to (1) flow more easily past the stationary
fan blades of a the downstream fan and/or (2) create a set of input
conditions that would allow the downstream fan to operate more
efficiently, at above design conditions, rotating faster than
normal for a given input power level. In certain applications it
may be beneficial to combine diffuser element 14 and second
diffuser element 15 with other functions such as a heat exchanger
to add or remove heat from the airflow, or an Electro-Magnetic (EM)
shield to substantially prevent the passage of EM waves through the
fan opening. While the number of different diffuser element designs
and their related efficiencies and functionalities is vast, the
principle of reducing swirl to improve the efficiency of the
secondary or downstream fan remains the same.
[0085] While diffuser element 14 and second diffuser element 15 may
be primarily designed to reduce swirl, they will also add an
impedance to the airflow that will add to the system head and
reduce the efficiency of the system. This becomes a trade-off that
must be balanced against the positive effects of installing a
diffuser element between two fans in series. In general, however,
the overall effect of installing a diffuser element is positive
since the impact of the reduced swirl far outweighs the incremental
system head. In some applications the pressure drop across the
diffuser element may be monitored and used to measure the airflow
through the diffuser element.
[0086] FIG. 2 also illustrates the impact of a fan failure. If
primary fan 8 fails, then secondary fan 16 and tertiary fan 17 will
continue to draw air through the assembly and "push" it in the same
direction, i.e. combined airflow 22 will continue to flow in the
same direction, and no external baffling changes will be required.
A similar result will occur if secondary fan 16 or tertiary fan 17
fails. This ability to continue to provide airflow in the same
direction despite the loss of a fan is the primary inherent
advantage of a series fan configuration.
[0087] In the event of a primary fan 8 failure, the fan blades may
continue to rotate or they may remain fixed or "locked"--depending
on the nature of the failure. However, in the case of primary fan
with variable pitch blades 8a, primary fan blade 9 will remain in
an oblique position during normal operation (i.e. while rotating in
the direction defined by arrow 7) and then return to coaxial
position 9a in the event of a failure. Since coaxial position 9a
aligns the fan blade with the airflow, it will present a far lower
input impedance as seen by secondary fan 16, therefore contributing
to increased efficiency during a primary fan with variable pitch
blades 8a failure relative to an primary fan 8 (i.e. fixed fan
blade) failure. It follows that a secondary fan 16 with similar
variable pitch blades would also contribute to greater efficiency
during the failure mode as it would present a lower output
impedance as seen by primary fan 8.
[0088] Although the direction of airflow will remain consistent in
a series fan configuration with a single fan failure, the volume of
airflow will be reduced if the remaining fan(s) continue to operate
at the same speed. This is an acceptable situation only if the
volume of airflow does not fall below the minimum required to
dissipate the heat generated in the cabinet or by the components
being cooled. In practice a control system may be required to sense
the fan failure and adjust the remaining fan speed accordingly, in
order to ensure that this minimum airflow requirement is met until
the defective fan can be replaced. This type of control can be
easily implemented since (1) many fans today are available with
fault sensors to indicate an impending failure/total failure and
(2) fan speed can be easily controlled by varying the input
voltage, at least for DC fans, or by using some other type of fan
speed controller.
[0089] During normal operation, primary fan 8, secondary fan 16,
and tertiary fan 17 may all be operating at less than full rpm to
produce the required combined airflow 22. The lower rpm will reduce
the noise produced by each fan and also extend the life of each
fan. Should the controller sense an impending or actual failure in
one of these fans, then the. The user may then be alerted to
replace the defective fan on a scheduled rather than an urgent
basis. Similarly, if the airflow is impeded by a clogged air filter
or some other obstacle, then the power applied to the fans may be
increased to the point where combined airflow 22 remains the
same.
[0090] A series configuration of "n+1" fans configured with
intermediate diffuser elements, as described above, will be
tolerant to the failure of one fan where "n" is the total number of
fans whose combined flow is required to meet the cooling
requirements of the system or component(s) being cooled. FIG. 2
illustrates an example where "n"=2, and "n+1"=3 fans in total.
Actual configurations may include 2, 3 or more fans depending on
cooling requirements. The remainder of this document will deal with
high performance series fans with diffuser elements configured with
two fans for reasons of simplicity, however it should always be
noted that additional fans may be added to these representative
series configurations. Further, it should be noted that multiple
fans could be added to provide increased performance while
preserving an n+1 redundancy and providing a fault tolerant
configuration.
[0091] It is also possible that multiple series fans with diffuser
or flow modification elements may be installed in parallel to meet
demanding cooling requirements. In this case, there is no need for
the movable baffles normally associated with parallel
configurations since each independent high performance series fans
with diffuser element assembly is fault tolerant and will not allow
the back flow or "leakage" of air in the event of a fan failure.
These configurations may be used to meet very high airflow
requirements, to produce independently directed airflow streams, or
where space considerations limit the number of fans that may be
mounted in a series.
[0092] Series fans with flow modification element, or high
performance series fans, may be configured to allow a defective fan
to be replaced without having to shut down the system or components
being cooled--commonly referred to as "hot swapping" the fans. This
is made possible by the fact that high performance series fans 1
may be configured to fit in a sliding "drawer" that can be pulled
away from the cabinet without interrupting the airflow, as
illustrated in FIG. 3. In this case secondary fan 16 is being
replaced while sliding drawer 2 is in the "out position. Sliding
drawer 2 may then be returned to the "in" position without
affecting system operation or necessitating a system shut down. A
control system may be configured to detect the fan failure, alert
the user, detect the presence of a new and fully functional
secondary fan 16, adjust the power applied to both primary fan 8
and secondary fan 16 to maintain a controlled airflow throughout
the process, and then reset the lights on control panel 30 to
reflect normal operation. Note that diffuser element 14 could also
be replaced while the sliding drawer 2 is in the "out" position,
again without affecting system operation. Finger guard 6 has been
added to the configuration for safety reasons.
[0093] FIG. 4 provides further detail in a side view of high
performance series fans 1 mounted in sliding drawer 2. Primary fan
8 and secondary fan 16 are mounted co-axially in sliding drawer 2
such that the air flowing from primary fan 8 flows through diffuser
element 14 and directly into secondary fan 16. Sliding drawer 2
slides into and out of internal sleeve 3 as depicted by drawer
movement arrow 18. Sliding drawer 2 requires a minimum opening in
cabinet 4, taking less cabinet wall space than a parallel
configuration and making it easier to maintain the integrity of an
EM shield. In certain applications diffuser element 14 may be
configured as an integral part of the EM shield.
[0094] Internal sleeve 3 has at least five distinct functions; (1)
to provide a means to mount sliding drawer 2, and therefore high
performance series fans with diffuser element 1, on cabinet 4, (2)
to provide a means to allow sliding drawer 2 to slide "in" or
"out", (3) to support sliding drawer 2 whilst in the "in" or "out"
position, (4) to provide baffling such that combined airflow 22
only exits the assembly through the open end of internal sleeve 3,
and (5) to provide, in combination with sliding drawer 2, a
contained channel for the air flowing through high performance
series fans 1.
[0095] The latter function is particularly important since the
length and geometry of the contained air channel between primary
fan 8 and diffuser element 14 may be configured to provide a
pre-determined level of natural decay of swirl in the airflow
before it enters diffuser element 14. This natural decay of swirl
may be enhanced by providing multiple corners within this portion
of the contained air channel, for example by configuring the air
channel with a square or hexagonal cross section. In certain
applications, in particular those using a primary fan 8 having
stator blades, the this portion of the contained air channel may be
shortened while providing the same overall effect since some of the
swirl will have already been removed by the stator blades.
[0096] Similarly the length and geometry of the contained air
channel between primary fan 8 and diffuser element 14, and diffuser
element 14 and secondary fan 16, may be configured to reduce the
acoustical noise produced by high performance series fans 1. As an
example, a short contained air channel with smooth walls between
diffuser element 14 and secondary fan 16 may be configured to
reduce acoustical noise, even though it may not necessarily be
required to further reduce swirl in this region.
[0097] Flange 21 may be used to secure internal sleeve 3 to cabinet
4 with machine screws, or through some other suitable means. Latch
19 may be used to hold and seal tab 20 against flange 21, i.e. to
hold sliding drawer 2 in the "in" position, until released. Back
lip 5 extends outward from the normal geometry of sliding drawer 2
to prevent the accidental removal of sliding drawer 2 by coming to
rest against an extended portion of flange 21, when sliding drawer
2 is in the full "out" position. A means may be provided to
completely remove sliding drawer 2 from internal sleeve 3, when and
if required.
[0098] In some applications diffuser element 14 may be configured
as a diffuser, to reduce swirl in the airflow leaving primary fan
8, and as a filter, to substantially remove unwanted particulate
from the airflow. In these cases diffuser element 14 should be
selected to optimize both functions, in combination with the length
and geometry of the contained air channel between primary fan 8 and
diffuser element 14, as described above, while introducing a
minimal incremental system head.
[0099] Alternatively, an air filter optimized for removing
particulates may be mounted between finger guard 6 and primary fan
8, leaving the diffuser element 14 to be fully optimized for the
reduction of swirl. In these configurations diffuser element 14 may
be a screen, a laminar flow element consisting of a number of
round, square, hexagonal, or alternatively shaped tubes mounted
co-axially with the fans, a series of flow directing vanes, or some
combination thereof. Further, diffuser element 14 may be configured
with an air funnel at the entry point to each tube, and with the
funnel openings directed/skewed towards the source of the air as it
comes off the blades of primary fan 8. Regardless of configuration,
the flow related objective of diffuser element 14 is, in
combination with the length and geometry of the contained air
channel between primary fan 8 and diffuser element 14, to reduce
swirl in the airflow leaving primary fan 8, and before it enters
secondary fan 16, while introducing a minimum amount of incremental
back pressure, thereby contributing to the overall efficiency of
the high performance series fans 1.
[0100] Primary fan 8 and secondary fan 16 may rotate in the same or
different directions. This aspect of the configuration will be
somewhat dependent on the cost, performance, and acoustical
objectives associated with a given application, as a pair of
standard fans that rotate in the same direction may be less
expensive than a pair of counter-rotating fans, or a
counter-rotating fan module. Also, any efficiency gained by having
counter-rotating fans should be weighed against the service cost of
stocking two types of spares.
[0101] FIG. 5 shows high performance series fans 1 in operation. In
this case sliding drawer 2 has been moved "in" such that finger
guard 6 is flush with the outside of cabinet 4. Sliding drawer 2
slides within the internal sleeve with sliding interfaces at flange
21 and back lip 5. Alternatively, sliding drawer 2 may be
configured to slide on rails or some other suitable means.
[0102] Sliding drawer 2 is prevented from moving farther into
cabinet 4 by tab 20 (top and bottom) when it interfaces with the
outer edge of flange 21.Sliding drawer 2 is then held in place by
latch 19. In some cases an aesthetic cover may be configured to
snap onto the outside of sliding drawer 2, once in place, to
improve the appearance of the cooling module. Further, the
aesthetic cover would provide visual access to the control panel so
that the operation of high performance series fans 1 could still be
easily monitored.
[0103] As in FIG. 4, cooling air flows efficiently through primary
fan 8, diffuser element 14, and secondary fan 16 to provide
combined airflow 22. It is important to note that the direction of
combined airflow 22 remains consistent whether one or both of
primary fan 8 and secondary fan 16 is/are operational. This
precludes the requirement for any incremental baffling to ensure
that the direction of combined airflow 22 remains consistent in the
event of a fan failure.
[0104] In the event of a primary fan 8 failure, combined airflow 22
will continue to flow through primary fan 8 and into secondary fan
16--i.e. the airflow will not escape through primary fan 8.
Likewise, in the event of an secondary fan 16 failure, combined
airflow 22 will continue to flow through secondary fan 16 and into
cabinet 4--i.e. the airflow will not escape through secondary fan
16. This precludes the requirement for specialize baffling to
prevent combined airflow 22 from escaping through the defective
fan.
[0105] The last two paragraphs highlight a very important
characteristic of the series fan configuration--no baffling is
required to accommodate a failed fan scenario. This contrasts
sharply with the parallel fan configuration where substantial
baffling is required to prevent the loss of air through the
defective fan and to keep the direction of airflow consistent in
the event of a fan failure. As a result, high performance series
fans are very compact, and they may be configured as a stand-alone
cooling module that does not requires any further baffling.
[0106] Primary fan 8 may need to be rated at a higher capacity than
secondary fan 16 to compensate for the added backpressure
introduced by diffuser element 14 and secondary fan 16, if and when
secondary fan 16 is defective and/or stationary. Conversely stated,
secondary fan 16 may be rated at a lower capacity than primary fan
8 because it will not "see" the same incremental causes of
backpressure. In practice both fans may be of the same rating, but
should they be so configured that the ratings match the higher
rating required by primary fan 8. This will ensure that combined
airflow 22 will always exceed the minimum required regardless of
whether one or both fans is/are operational.
[0107] During normal operation primary fan 8 and secondary fan 16
may run at less than full rpm as long as combined airflow 22 meets
the cooling requirements for the application at hand. Further, the
total power applied to the system may be re-balanced
asymmetrically, with more power being applied to the secondary fan
in order to take advantage of the fact that secondary fan 16 runs
more efficiently than primary fan 8, therefore improving the
overall efficiency of the system. The configuration will be very
responsive to a fan failure since the remaining fan is already
running, albeit at a lower rpm, and it is much faster to ramp up
from partial to full rpm than it is to go from stopped to full
rpm.
[0108] It can be deduced from FIG. 5 that the size of the opening
in cabinet 4 will be only slightly larger than the size of primary
fan 8. In a parallel configuration the opening would be
approximately twice this size since the two fans would be mounted
side-by-side. Further the volume of space required in cabinet 4
will be much smaller than a parallel configuration since no extra
internal baffling will be required. This 2:1 reduction in the size
of the opening combined with the much smaller internal volume
requirement represents a major benefit of the series configuration
from a system designer's perspective.
[0109] In simple configurations, high performance series fans 1 may
be implemented without a controller by using two fans, each of
which is capable of providing the full combined airflow 22 required
for the application at hand. Under normal operating conditions
combined airflow 22 will actually exceed the minimum requirement,
keeping the load cooler than necessary. A fan failure can be
tolerated since the remaining fan will already be running, and is
capable of carrying the load. As described above, no further
baffling is required since the fans are in series. A simple
indicator light will flag the operator to replace the defective
fan.
[0110] In other configurations, where power consumption, precise
cooling, and/or acoustic management are important requirements, a
controller may be used to provide a controlled airflow during
normal operation and in the event of a fan failure. The controller
may be installed behind control panel 30, as shown in FIG. 6. This
drawing also illustrates the full extent of tab 20 as seen around
the perimeter of the unit, and the front face of finger guard 6.
Control panel 30 contains indicator lights 32 to alert the user
regarding the operation of primary fan 8, secondary fan 16, and
diffuser element 14 (reference FIG. 5). The controller may also be
adapted to communicate with other systems for remote monitoring and
control.
[0111] An aesthetic cover may be affixed over the entire front face
of high performance series fan 1, providing that airflow is not
impeded to the degree that it will affect cooling performance. In
most cases indicator lights 32 will need to be visible through the
aesthetic cover so that the operator can respond to a fan problem,
however this may not be an absolute requirement in situations where
the operator may be initially alerted through some other means, for
example through software and a remote monitor. In the latter case
the operator, once alerted to the problem, could remove the
aesthetic cover and visually inspect indicator lights 32 to
determine which fan is defective.
[0112] Fans are readily available with sensors for failure, or
degradation in performance that might indicate imminent failure.
This information may be used to inform the controller to increase
the speed of the other fan in order to continue to provide the
required airflow. The controller can also use the same information
to illuminate the appropriate indicator lights 32, alerting the
operator to take action. Indicator lights 32 may be activated in
several different modes, e.g. steady, flashing, red yellow or
green, to communicate certain information and the level of severity
of the problem to the user.
[0113] Under normal operation each fan may be running at less than
maximum rpm to extend life, reduce noise, and to allow for an
immediate increase in speed should the other fan fail. It is
possible that one fan may be left idle (i.e. not running) during
normal operation, however in practice it may be better to leave
both fans running to some extent in order to (1) continually ensure
that they are both operational (2) minimize any "ramp up" time in
the event of a failure and (3) reduce any unnecessary static loads
or sources of backpressure during normal operation.
[0114] FIG. 7 illustrates how high performance series fans 1 may be
withdrawn from cabinet 4 to allow for the inspection and/or
replacement of a faulty component. Note that finger guard 6 has
been removed in this diagram for illustrative purposes only, and
that this would not normally be the case when servicing the
unit.
[0115] FIG. 8 provides a top view of high performance series fans
1, and illustrates the method of replacing a defective fan without
shutting down the system, commonly referred to as "hot swapping"
the fans. In this scenario secondary fan 16 is defective, and this
information would have been conveyed to the user through indicator
lights 32.
[0116] The first step in replacing defective secondary fan 16 is to
pull out sliding drawer 2 until it is fully extended, as depicted
by drawer extension arrow 42. At this point back lip 5 will rest
against the internal edge of flange 21 to prevent further forward
movement of sliding drawer 2. Internal indicator lights 33 may be
used as a secondary check to ensure that the correct (faulty) fan
is being removed.
[0117] Once sliding drawer 2 is in the fully extended position,
secondary fan 16 may be removed by sliding it sideways, to the
right, and disconnecting internal power and control cable 44 from
internal power and control receptacle 46. FIG. 8 shows secondary
fan 16 partially removed with approximately 30% of its width
already beyond the right side of sliding drawer 2. Note that
secondary fan 16 is completely outside of and can slide clear of
cabinet 4. It can be seen that diffuser element 14 and primary fan
8 could be similarly removed without interfering with cabinet
4.
[0118] Primary fan 8 remains running as secondary fan 16 is being
removed and replaced, and may be running at a higher RPM, as
determined by controller 40, so that combined airflow 22 remains at
or above the minimum airflow required to cool the components
contained within cabinet 4. Note that the direction of combined
airflow 22 will not change, as it remains contained and directed by
internal sleeve 3, precluding the need for any change in baffling
when running with only one fan. It can be seen from FIG. 8 that
diffuser element 14 and primary fan 8 may be similarly removed
without affecting the direction of the combined airflow 22. All of
these operations can be completed without shutting down the system
contained in cabinet 4.
[0119] Referring back to the scenario at hand, a new secondary fan
16 may be set in place in sliding drawer 2, and the internal power
and control cable 44 may be re-connected to internal power and
control receptacle 46. Controller 40 may be configured to recognize
that secondary fan 16 has been replaced, and that it is
operational, and to adjust the speed of primary fan 8 and secondary
fan 16 accordingly. Sliding drawer 2 can then be pushed back into
cabinet 4 such that finger guard 6 and control panel 30 are flush
with the outside of cabinet 4. Indicator lights 32 may then be
monitored by the operator for further problems. Indicator lights 32
and controller 40 may also be interfaced with the system in cabinet
4 to alert the operator through other means such as a remote system
monitor.
[0120] Sliding drawer 2 may be configured to accommodate standard
sized fans available from a variety of manufacturers, e.g. 120 mm,
92 mm, or 40 mm fans. These fans are readily available in a variety
of thicknesses that loosely correspond to a range of CFM ratings,
i.e. the thicker fans generally have a higher CFM rating for a
given fan diameter. It follows that sliding drawer 2 may be
configured to accept the thickest fan in a particular size range,
and that slimmer or lower capacity fans may be accommodated by
installing the fan in conjunction with a "shim" ring that takes up
the extra space and holds the fan securely in place. This approach
allows a standard size sliding drawer 2 to accommodate a variety of
fan capacities, and also provides a convenient upgrade path since
the shims may be removed or replaced with thinner shims to allow
the installation of higher capacity fans. This approach can be used
to provide additional cooling, when required, without replacing the
entire cooling subsystem.
[0121] In some applications it may be necessary to provide a fixed
baffle 48 inside cabinet 4 to ensure that re-directed combined
airflow 49 is appropriate for the application. This fixed baffle 48
will need to interface with internal sleeve 3 to prevent air
leakage, however it will remain fixed in the event of a fan
failure.
[0122] FIG. 9 shows how two high performance series fan modules may
be mounted in parallel for increased airflow. Parallel baffle 50
may be configured to interface with top inner sleeve 3a and bottom
inner sleeve 3b to contain the output from both compact series fan
assemblies, and produce total combined airflow 54. Sealing cap 52
may be positioned between the two assemblies to improve the airflow
and to prevent any leakage of air in this area. Sealing cap 52 may
be configured with a cone shaped cap that protrudes downstream, or
some other feature, to increase the efficiency of the airflow.
[0123] It is important to note that even though this is a parallel
configuration of series fan assemblies, it does not require any of
the specialized baffling normally associated with this type of
installation. This is because each one of the high performance
series fans with diffuser element assemblies is independently fault
tolerant, and prevents the back flow of air in the event of a fan
failure. In other words, each series fan assembly will always
contribute to total combined airflow 54, and will not allow a
portion of combined airflow 54 to leak back out to the ambient air
around cabinet 4, even in the event of a single fan failure.
[0124] The parallel configuration of high performance series fan
modules also provides more flexibility in the event of a fan
failure. In this case a controller may be configured to speed up
three additional fans, rather than just one in a non-parallel
installation, to maintain a constant total combined airflow 54. It
follows that parallel configurations with more than two high
performance series fans with diffuser element assemblies will have
an even greater ability to respond to a single fan failure.
[0125] FIG. 10 shows a high performance series fan module
configured with a supplementary air inlet and outlet to improve
airflow in the event of a fan failure.
[0126] Under normal operation, air inlet baffle 70 and air outlet
baffle 72 will direct the output from primary fan 8 and diffuser
element 14 through secondary fan 16 to form combined airflow 22, as
previously described. Combined airflow 22 is further directed
through air funnel 74 which may have an opening size that
approximates the opening size of the fans.
[0127] In the event of a primary fan 8 failure, air inlet baffle 70
may be moved to position 70a to reduce the input impedance seen by,
and therefore increase the flow of air into, secondary fan 16.
Outlet baffle 72 may remain in place to ensure that no air leaks
from the output side to the input side of secondary fan 16.
Combined airflow 22 will be comprised solely of the output from
secondary fan 16, part of which will flow through the defective
primary fan 8 and another part of which will flow through the open
inlet baffle 70a.
[0128] Conversely, in the event of an secondary fan 16 failure, air
outlet baffle 72 may be moved to position 72a to reduce the output
impedance seen by, and therefore increase the flow of air out of,
primary fan 8. In this case inlet baffle 70 will remain in place to
ensure that no air leaks from the output side to the input side of
primary fan 8. Combined airflow 22 will be comprised solely of the
output from primary fan 8, part of which will flow through the
defective secondary fan 16 and another part of which will flow
through the open outlet baffle 72a.
[0129] Inlet baffle 70 and outlet baffle 72 may be configured to
operate automatically, based on pressure differentials, or to be
controlled by controller 40 (reference FIG. 8). In the former case
a higher relative pressure between primary fan 8 and secondary fan
16 would cause outlet baffle 72 to move to position 72a, and a
lower relative pressure between the same fans would cause inlet
baffle 70 to over to position 70a. In the latter case controller 40
may be used to control the position of the baffles in response to a
failing or defective fan. In all cases the action taken serves to
relieve the pressure differential and improve the flow of air
through the configuration. However the use of the controller
provides greater flexibility and does allow for certain load
sharing scenarios between the two fans that might cause temporary
pressure differentials between the fans that might otherwise be
interpreted as a defective fan situation.
[0130] It is important to note that air inlet baffle 70 and air
outlet baffle 72 may be configured, in conjunction with air funnel
74 and controller 40 (reference FIG. 8), such that the direction
and rate of combined airflow 22 will remain constant even in the
event of a fan failure.
[0131] This precludes the requirement for any further baffle
changes within cabinet 4 in the event of a fan failure, meaning
that the configuration may still be supplied as a standalone module
that provides fault tolerant cooling.
[0132] It is also important to note that the use of air inlet
baffle 70 and air outlet baffle 72 still allows for the replacement
of a defective fan or filter element/diffuser while the system is
running. This is because air inlet baffle 70 and air outlet baffle
72 have been configured to not interfere with the normal removal
and replacement of the fan and filter element/diffuser element
while sliding drawer 2 is in the "out" position as previously
described.
[0133] Primary fan 8 and secondary fan 16 may both be mounted with
axis parallel to combined airflow 22 as shown in FIG. 10.
Alternatively, primary fan 8 and secondary fan 16 may both be
mounted at a slight angle to the desired combined airflow 22, and
not necessarily in a coaxial fashion, in order to improve the
smooth flow of air between primary fan 8 and secondary fan 16. In
this case inner sleeve 3 and air funnel may be adaptively
re-configured to ensure that combined airflow 22 flows in the
desired direction.
[0134] FIG. 11 provides a connection diagram for high performance
series fan controller 40. Controller 40 may be configured to
receive its primary input from cooled component(s) 62, upon which
the output of high performance cooling fan module 1, i.e. combined
airflow 22, impinges. This primary input may be comprised of
information such as the temperature of cooled component(s) 62, the
rate of airflow around cooled component(s) 62, and the current
and/or anticipated workload on cooled component(s) 62. Information
regarding the anticipated workload on cooled component(s) 62 would
allow controller 40 to proactively respond to a corresponding
change in heat dissipation requirements by changing the speed of
primary fan 8 and/or secondary fan 16.
[0135] Controller 40 may also be configured to receive input from
airflow sensor 60. Airflow sensor 60 provides information regarding
the rate of combined airflow 22, and this information may be used
by controller 40 to test for appropriate responses to changes in
input to primary fan 8 and/or secondary fan 16. A non-appropriate
response to such an input may be used by controller 40 to determine
that there may be a fault with diffuser element 14 or one of the
fans. For example, controller 40 may determine that combined
airflow 22 cannot be maintained above a threshold level and may
deduce that (1) this problem may be caused by a seriously clogged
diffuser element 14, especially if it has a secondary function as a
filter, or, in the worst case, that (2) both fans may have failed
or are failing simultaneously. The user would be alerted to take
immediate action in either case, and a graceful shutdown procedure
could be initiated if either situation persists for an unacceptable
period of time.
[0136] Controller 40 may also be configured to receive input from
position sensors 64, which inform controller 40 regarding the
correct installed position of primary fan 8, diffuser element 14,
and secondary fan 16. In the case of the fans, this information may
be combined with input from combined control and monitor wires 66
to determine that the fans are installed correctly and operating
efficiently. The combined control and monitor wires may be used to
supply a control voltage to the fans, monitor current draw, and in
some cases monitor other information such as rpm, output
temperature, or output flow rate.
[0137] Position sensors 64 may further contain a physical feature
that precludes the incorrect installation of primary fan 8 and
secondary fan 16, i.e. prevents an accidental installation that
would cause air to flow in the wrong direction. Such an incorrect
installation could cause immediate damage to the components being
cooled.
[0138] The information provided by combined monitor and control
wires 66 may be used by controller 40 as leading indicators of
potential fan failure. As an example, a drop in rpm for a given
voltage input may indicate that a bearing is failing. Controller 40
may initially respond by increasing the voltage input to that fan,
and alerting the user to the problem. Controller 40 may ultimately
respond by shutting down the defective fan and changing the load
over to the alternative fan if the problem persists. Most
importantly, the information allows the controller to make
proactive responses to an impending problem before cooled
component(s) 62 becomes overheated.
[0139] Controller 40 may communicate with the user through control
panel 30, containing indicator lights 32a, 32b, and 32c, which may
be used to indicate the status of primary fan 8, diffuser element
14, and secondary fan 16 respectively. Any commonly understood
indicator algorithm may be used, for example green meaning normal
operation, yellow meaning that a component should be replaced due
to sub-optimal performance or impending failure, and red or
flashing red used to indicate that a component has failed. Note
that a failed fan does not mean that high performance cooling fan
module 1 is not operating; it simply means that the system is only
running with one fan and has no ability to respond to a further fan
failure. Therefore the failed component must be replaced
immediately to avoid potential problems.
[0140] As an example, controller 40 may be used to monitor the
amount of time that diffuser element 14 is in use, and to activate
the appropriate indicator light 32 should the "in use" time exceed
a recommended maximum. This will alert the operator to replace
diffuser element 14. The appropriate position sensor 64 in may be
used to automatically reset the "in use" timer back to zero. This
algorithm would be particularly useful in applications where
diffuser element 14 is configured as a combined filter/diffuser
element.
[0141] Controller 40 may also communicate with the user through a
second redundant set of internal indicator lights 33 (reference
FIG. 8). These lights may be more visible to the user or service
technician when the fans are being replaced, and therefore they
will serve as a safeguard to prevent the accidental removal of a
correctly operating fan. Such a mistake would leave only the
defective fan in place, potentially causing immediate damage to
cooled component(s) 62. Controller 40 may use an audible emergency
signal to instantly warn the user of such a dangerous
situation.
[0142] FIG. 12 presents a control algorithm for a high performance
series fan controller, in flow chart format.
[0143] The fundamental purpose of the controller is to keep cooled
component(s) 62 (reference FIG. 11) within a defined control
temperature range, despite changes on workload that might affect
the heat dissipated by cooled component(s) 62. Therefore the first
task in each control cycle is to check for anticipated changes in
workload as outlined in first decision triangle 80. This
information may come from the operating system associated with
cooled component(s) 62. An increase in workload would cause the
controller to increase the output CFM control point, and a decrease
in workload would cause the controller to decrease the output CFM
control point, perhaps after some delay period, as indicated by
first control box 86. The controller would proceed directly to
second decision triangle 82 should there be no anticipated changes
in workload.
[0144] At second decision triangle 82 the controller will check to
ensure that cooled component(s) 62 (reference FIG. 11) is operating
within its defined control temperature range. Should this not be
the case, then the controller will adjust the output CFM control
point to raise or lower the temperature of cooled component(s) 62
as required. However under normal operation, when no adjustment is
required, the controller will proceed directly to third decision
triangle 84.
[0145] At third decision triangle 84, the controller checks to
ensure that the output CFM, i.e. combined airflow 22 (reference
FIG. 11), is at the output CFM control point. Should there be a
discrepancy that lies outside of the acceptable control range, then
the controller will immediately investigate to determine the cause
of the problem. As an example, secondary fan 16 (reference FIG. 11)
may have suffered a drop in rpm given the same input parameters, a
possible leading indicator of impending fan failure. The controller
would then proceed to take corrective action by adjusting the
inputs to secondary fan 16 and notifying the user through indicator
lights 32 (reference FIG. 11).
[0146] Under normal circumstances the output of the high
performance cooling fan module will be at the required constant
output CFM control point and no corrective action will be required.
In this case the controller loops back to first decision triangle
80 to repeat the above control cycle once again.
[0147] While operating normally, the controller may actually change
the speed of both fans slightly on a regular timed basis. These
subtle changes in rpm will prevent any lasting beat frequencies
that might occur if the fans are left running at a constant rpm for
any length of time.
[0148] Interrupts may be used at any time to alert the controller
regarding a situation that requires immediate attention. Examples
may include a locked rotor ("0" rpm with a full normal input) or
perhaps a dislodged fan. In these cases the controller must take
immediate action to preserve a constant CFM output, thus keeping
the cooled component(s) at the required operating temperature.
[0149] FIG. 13 provides a perspective view of high performance
series fan sink 100. Primary fan 8 and secondary fan 16 are
configured in series to draw inlet airflow 108 into high
performance series fan module 106, and push it into heat sink 102
where it divides into right outlet airflow 110 and left outlet
airflow 112. Primary fan 8 and secondary fan 16 may be obliquely
mounted on heat sink 102 at a variety of angles such the diagonal
of the fans substantially covers the width of heat sink 102 and
provides airflow through substantially all of the channels within
heat sink 102. Air is retained within the confines of heat sink
102, such that it flows through and only exits at the open ends of
heat sink 102, by baffle 104.
[0150] Baffle 104 may be configured to hold high performance series
fan module 106 at a distance above heat sink 102, while preventing
the leakage of air at the interface between baffle 104 and high
performance series fan module 106, to improve the dispersion of air
throughout heat sink 102. Further, baffle 104 may be configured to
expand the opening of high performance series fan module 106 such
that covers substantially all of the width of heat sink 102,
allowing smaller series fan modules 106 to be used effectively with
larger heat sinks 102.
[0151] Inlet airflow 108 is drawn through finger guard 122, into
primary fan 8, through diffuser element 14, into secondary fan 16,
and then pushed through heat sink 102 and exhausted as right outlet
airflow 110 and left outlet airflow 112. Alternatively, the
direction of airflow may be reversed such that right outlet airflow
110 and left outlet airflow 112 become the inlet airflows, and the
air is exhausted through finger guard 122 at inlet airflow 108,
which becomes the exhaust. However the former configuration, as
illustrated in FIG. 13, provides for an impingement air flow on
heat sink 102, and this can be directed at the area of maximum heat
flux on heat sink 102 for enhanced cooling efficiency.
[0152] Control module 120 controls the operation of high
performance series fan sink 100. Primary fan indicator light 122
and secondary fan indicator light 124 indicate the operating status
of primary fan 8 and secondary fan 16 respectively. Control module
120 may be configured to sense the failure of primary fan 8 or
secondary fan 16 and increase the power to secondary fan 16 or
primary fan 8, respectively, to maintain a relatively constant
right outlet airflow 1 10 and left outlet airflow 112 during a
single fan failure. Further, control module 120 may be configured
to be responsive to a range of different backpressures to provide a
relatively constant right outlet airflow 110 and left outlet
airflow 1 12 over a range of operating conditions, or for a variety
of heat sinks 102.
[0153] FIG. 14 provides a section view of high performance series
fan sink 100. High performance series fan module 106 contains
primary fan 8, diffuser element 14, and secondary fan 16. High
performance series fan module 106 may be configured as a module
that contains all of these components and holds them at the
appropriate location, or alternatively as a standardized
sub-assembly that only contains diffuser element 14 and is adapted
to be bolted or otherwise fastened between two industry standard
fans of similar geometry, e.g. two 120 mm or 40 mm fans.
[0154] Primary fan 8 is separated from diffuser element 14 by a
first distance, and diffuser element 14 is further separated from
secondary fan 16 by a second distance. The purpose of the first
distance between primary fan 8 and diffuser element 14 is to reduce
the swirl component of the airflow exiting from primary fan 8
through natural swirl decay, with a longer channel generally
resulting in an increased level of natural swirl decay. The first
distance may be reduced by configuring the internal geometry of the
airflow channel to increase the rate of natural swirl decay, e.g.
by using a square or octagonal internal cross section and/or by
incorporating ridges, spines, or other surface features along the
interior walls of the airflow channel, thereby reducing the overall
length of high performance series fan module 106. The first
distance may be further reduced by selecting a primary fan 8 having
an integrated stator on the outlet side, thereby providing some
level of swirl decay before the airflow leaves primary fan 8.
[0155] The purpose of diffuser element 14 is to complement the
natural swirl decay accomplished within the first distance, i.e.
between primary fan 8 and diffuser element 14, by further reducing
the swirl component of the airflow before it enters secondary fan
16. This will increase the efficiency of secondary fan 16.
[0156] The purpose of the second distance between diffuser element
14 and secondary fan 16 is to reduce the acoustical noise produced
by high performance series fan module 106. The small gap between
the two components also provides sufficient space to mount a
pressure sensor, and this signal may be compared to the signal
produced by another pressure sensor located on the upstream side of
diffuser element 14 to provide an indication of flow rate through
high performance series fan module 106.
[0157] Thermal load 130 may be in thermal communication with the
bottom of heat sink 102, and may be optimally positioned such that
area of highest heat flux (i.e. the hottest portion of heat sink
102) is immediately below the impinging airflow. Heat may then be
removed through forced convection as the air flows through heat
sink 102 and exits as right outlet airflow 110 and left outlet
airflow 112, as previously described. Control 1o module 120 may be
configured to maintain a constant temperature of thermal load 130,
a constant right outlet airflow 110 and left outlet airflow 112, or
some combination of these and/or other control parameters.
[0158] FIG. 15 illustrates high performance series fan sink 100 as
primary fan 8 is being replaced. A defective primary fan 8 may be
removed while thermal load 130 (reference FIG. 14) remains active
since control module 120 may be configured to increase the power
applied to secondary fan 16 during the primary fan 8 outage, and
until primary fan 8 has been replaced, in order to maintain a
relatively constant right outlet airflow 110 and left outlet
airflow 112 (reference FIG. 14). Control module 120 may also be
configured to detect the re-insertion of a new primary fan 8, and
may then re-apply power to both fans in a controlled fashion to
optimize the performance of high performance series fan module 106,
as previously described.
[0159] FIG. 16 illustrates high performance series fan sink 100
with secondary fan 16 being replaced. A defective secondary fan 16
may be removed while thermal load 130 (reference FIG. 14) remains
active since control module 120 will increase the power applied to
primary fan 8 during the secondary fan 16 outage, and until
secondary fan 16 has been replaced, in order to maintain a
relatively constant right outlet airflow 110 and left outlet
airflow 112 (reference FIG. 14). Control module 120 may also be
configured to detect the re-insertion of a new secondary fan 18,
and may then re-apply power to both fans in a controlled fashion to
optimize the performance of high performance series fan module 106,
as previously described.
[0160] FIG. 17 provides a perspective view of high performance
series fan tray 200, which may be configured with a single row of
high performance series fan modules, as shown, or multiple rows of
high performance series fan modules. Further, a single row of high
performance series fan modules may be configured as a partial fan
tray that may be mounted from the front of a rack system, and
possibility combined with a similar fan tray mounted from the back
of the same system to provide flexible and expandable cooling
solutions. Further, high performance series fan trays 200 may be
may be mounted horizontally to produce a vertical airflow, or
vertically to produce a horizontal airflow. Finally, one or more
high performance series fan modules may be added to an existing fan
tray, using a traditional array of single axial fans in parallel,
to increase performance and add a measure of fault tolerance to an
existing installation.
[0161] Each high performance series fan module within high
performance series fan tray 200 may be configured independently.
For example, one module may be configured with a duct to provide
direct cooling for one or more components within the system, and
another module may be configured to actively exhaust air from the
same or different component(s). Other modules may be configured to
provide a more general flow of air within the system.
[0162] The high performance series fan tray 200 depicted in FIG. 17
includes three high performance series fan modules, 106a, 106b, and
106c, that draw inlet airflows 108a, 108b, and 108c, respectively,
to produce outlet airflows 110a, 110b, and 110c, respectively.
Control module 120 may be configured to monitor and control high
performance series fan modules 106a, 106b, and 106c, and outlet
airflows 110a, 110b, and 110c
[0163] FIG. 18 provides a second perspective view of high
performance series fan tray 200, showing further details of high
performance series fan module 106a (reference FIG. 17), which
contains primary fan 8, diffuser element 14, and secondary fan 16,
and operates as previously described. High performance series fan
module 106a further contains primary fan indicator light 122a and
secondary fan indicator light 124a.
[0164] It may be seen from FIG. 18 that control module 120 may
contain Cubic Feet per Minute (CFM) or temperature display 126,
increase increment button 130, decrease increment button 128, and
power switch 132. The CFM, temperature, or other set point may be
increased or decreased by pressing increase increment button 130 or
decrease increment button 128, respectively, causing control module
120 to adjust the power applied to high performance series fan
modules 106a, 106b, and 106c (reference FIG. 17) accordingly. CFM
or temperature display 126 may then be used to monitor the changing
parameter as it moves towards, and then reaches, the new set
point.
[0165] FIG. 19 illustrates high performance series fan tray 200
with primary fan 8c being replaced. Primary fan 8c may be removed
while the thermal load within the cabinet or system being cooled
remains active since control module 120 will increase the power
applied to secondary fan 16c, and high performance series fan
modules 106a and 106b (reference FIG. 17), during the primary fan
8c outage, and until primary fan 8c has been replaced, in order to
maintain a relatively constant combined outlet airflow, comprised
of output airflows 110a, 110b, and 110c (reference FIG. 17).
Control module 120 may also be configured to detect the
re-insertion of a new primary fan 8c, and then re-apply power to
high performance series fan modules 106a, 106b, and 106c in a
balanced fashion in order to optimize the performance of high
performance series fan tray 100, as previously described.
[0166] FIG. 20 illustrates high performance series fan tray 200
with secondary fan 16c being replaced. Secondary fan 16c may be
removed while the thermal load within the cabinet or system being
cooled remains active since control module 120 will increase the
power applied to primary fan 8c, and high performance series fan
modules 106a and 106b (reference FIG. 17), during the secondary fan
16c outage, and until secondary fan 16c has been replaced, in order
to maintain a relatively constant combined outlet airflow,
comprised of output airflows 110a, 110b, and 110c (reference FIG.
17). Control module 120 may also be configured to detect the
re-insertion of a new secondary fan 16c, and then to re-apply power
to high performance series fan modules 106a, 106b, and 106c in a
balanced fashion in order to optimize the performance of high
performance series fan tray 100, as previously described.
[0167] FIG. 21 illustrates control module 120 operating in fan
failure mode. Control module 120 is in communication with, and
controls the power delivered to, primary fan modules 8a, 8b, and
8c, and secondary fan modules 16a, 16b, and 16c (reference FIG. 18,
19, 20), and their respective indicator lights. Control module 120
may be configured to sense that secondary fan module 16b has
failed, and to illuminate secondary fan module indicator light 124b
accordingly. Controller module 120 may then adjust the power
applied to cooling fan modules 106a, 106b, and 106c such that
adjusted inlet airflows 138a and 138c are greater than normal inlet
airflow 108 (shown here for reference only), and adjusted inlet
airflow 138b, solely generated by primary fan module 114b, is as
close to normal inlet air 108 as possible. Inlet flows 138a, 138b,
and 138c may be adjusted in this manner such that the combined
outlet airflow will be substantially equal to the sum of combined
normal outlet airflows 110a, 110b, and 110c, and the thermal load
within the system or cabinet being cooled will experience the same
degree of forced convection cooling as with normal operation.
Control module 120 may be configured to compensate for multiple fan
module failures in a similar manner, however at some point the
remaining fans may not be able to generate the full replacement
airflow during the outage situation. Further, control module 120
may be configured to re-adjust power delivered to the cooling fan
modules to normal levels once the defective fan(s) have been
replaced, and turn off the indicator lights accordingly.
[0168] FIG. 22 illustrates a method for monitoring the airflow
through high performance series fan module 106 using first pressure
sensor 142 and second pressure sensor 144. Control module 120 may
be in communication with both sensors, and may be configured to
monitor the output from both sensors to determine the differential
pressure between first pressure sensor 142 and second pressure
sensor 144, as caused by the flow of air through diffuser element
14. Control module 120 may then use the differential pressure
information to determine the rate of flow of air through diffuser
element 14, and may further use the flow rate information as a
feedback signal for an internal flow rate control algorithm. The
power applied to primary fan 8 and secondary fan module 16 may be
adjusted by control module 120 to compensate for any detected
difference between the measured flow rate and the flow set point
for high performance series fan module 106. A power adjustment that
does not generate the predicted response, or does not generate a
response that falls within normal guidelines, may indicate to the
controller that primary fan 8 or secondary fan 16 is failing or has
failed. Control module 120 may complete further tests, in like
manner, to determine which fan has a problem, to determine the
extent of that problem, and to determine an appropriate
response.
[0169] FIG. 22 also illustrates swirl gap 140 between primary fan 8
and diffuser element 14. The swirl component of the flow produced
by primary fan 8 will decay at an initial rate, and then decay at
an ever decreasing rate as the distance from primary fan 8
increases. Swirl gap 140 allows sufficient space for some decay of
swirl prior to diffuser element 14. This increases the
effectiveness of diffuser element 14 since the swirl component at
the inlet side of diffuser element 14 will have been reduced by
some amount, and the net swirl decay caused by swirl gap 140
combined with diffuser element 14 will be greater than that caused
by a diffuser element 14 placed immediately downstream from primary
fan 8. The location and physical characteristics of diffuser 14 may
be configured such that the swirl and other flow parameters meet or
exceed the design specifications for secondary fan 16 as the flow
enters secondary fan 16.
[0170] A small gap may be introduced between diffuser element 14
and secondary fan module 118 to reduce the acoustical noise
produced high performance series fan module 106, and to allows
sufficient space for second pressure sensor 144. This gap may be
eliminated if second pressure sensor 144 is placed within diffuser
element 14 116, at some distance from first pressure sensor 142,
and if acoustic management is not an overriding design
consideration.
[0171] Although diffuser element 14 has a very positive effect on
the efficiency and performance of high performance series fan
module 106, as previously described, it does introduce a small flow
restriction and a corresponding pressure drop. Although this is
acceptable during normal operation, it does limit the maximum
achievable flow rate when only one of primary fan 8 or secondary
fan module 16 is operational. Therefore in some applications
diffuser element 14 may be configured to slide out of the way,
swing out of the way, or otherwise be partially or completely
removed from the flow in order to maximize the achievable flow rate
during an outage situation.
[0172] Accordingly, diffuser element 14 may be configured to be
removable from the flow by splitting it in the middle, and allowing
each half to swing towards primary fan module 8. The right half of
diffuser element 14 and the left half of diffuser element 14 may be
configured to swing along the right and left sides of high
performance series fan module 106, respectively, and lie along the
sides of the airflow channel in the area normally defined as swirl
gap 140 during a fan outage situation. The sides of swirl gap 140
may be configured to accommodate the right and left sides of
diffuser element, so positioned, such that they present a minimum
restriction to the flow. Control module 120 may be configured to
release the right and left sides of diffuser element 14 during a
fan outage, such that they must be manually returned to normal
position when the defective fan has been replaced, and held there
with a retaining mechanism controlled by control module 120, or to
move the right and left sides of diffuser element 14 in a
controlled fashion both during the outage and after it has been
resolved.
[0173] FIG. 23 provides a perspective view of an alternatively
configured high performance series fan tray with high performance
series fan modules 106a and 106b mounted obliquely to provide a
relatively even airflow over the maximum width possible with only
two high performance cooling fan modules. Further, the primary and
secondary cooling fans located within high performance series fan
modules 106a and 106b, so mounted, may be conveniently removed by
sliding them in the direction defined by removal arrows 156 and
154, respectively. Multiple high performance series fan modules may
be configured obliquely, in this manner, and at various angles, to
provide a relatively even airflow over a maximum possible width
with the fewest possible number of high performance series fan
modules. Further, this configuration offers fault tolerance with
the fewest possible number of high performance series fan
modules.
[0174] The present invention may be embodied in other specific
forms without departing from the spirit or essential
characteristics thereof. Certain adaptations and modifications of
the invention will be obvious to those skilled in the art.
Therefore, the above-discussed embodiments are considered to be
illustrative and not restrictive, the scope of the invention being
indicated by the appended claims rather than the foregoing
description, and all changes which come within the meaning and
range of equivalency of the claims are therefore intended to be
embraced therein.
* * * * *