U.S. patent application number 12/091337 was filed with the patent office on 2009-01-15 for passive thermal management system.
This patent application is currently assigned to TIR TECHNOLOGY LP. Invention is credited to Daryl James, Philippe Schick.
Application Number | 20090014154 12/091337 |
Document ID | / |
Family ID | 38022926 |
Filed Date | 2009-01-15 |
United States Patent
Application |
20090014154 |
Kind Code |
A1 |
Schick; Philippe ; et
al. |
January 15, 2009 |
Passive Thermal Management System
Abstract
A traditional passive thermal management system can only be used
effectively in a single orientation because it relies on the
buoyancy of the heated air to create natural convection. A passive
thermal management system is provided which includes means for
transferring heat away from a heat source (10) in any orientation.
The system comprises a heat pipe (14) which is thermally coupled to
the heat source (10). The heat pipe (14) is capable of transferring
heat away from the heat source (10), wherein this heat is
transferred along the length of the heat pipe (14). Thermally
coupled to the heat pipe (14) is a fin system (12), which provides
a means for extraction of the heat from the heat pipe (14) and
transfer of this heat to the environment thereby dissipating the
heat generated at the heat source (10). The fin system (12) is
configured to provide a desired level of heat transfer to the
environment independent of the orientation of the thermal
management system.
Inventors: |
Schick; Philippe;
(Vancouver, CA) ; James; Daryl; (Coquitlam,
CA) |
Correspondence
Address: |
PHILIPS INTELLECTUAL PROPERTY & STANDARDS
3 BURLINGTON WOODS DRIVE
BURLINGTON
MA
01803
US
|
Assignee: |
TIR TECHNOLOGY LP
|
Family ID: |
38022926 |
Appl. No.: |
12/091337 |
Filed: |
November 8, 2006 |
PCT Filed: |
November 8, 2006 |
PCT NO: |
PCT/CA2006/001827 |
371 Date: |
August 22, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60749860 |
Dec 13, 2005 |
|
|
|
Current U.S.
Class: |
165/80.3 ;
165/104.33 |
Current CPC
Class: |
F28F 1/34 20130101; F21V
29/773 20150115; F28F 1/24 20130101; F21V 29/77 20150115; F28F 1/32
20130101; F21V 29/713 20150115; F28F 1/14 20130101; F28D 15/0275
20130101; F28F 1/20 20130101; F28D 15/0266 20130101 |
Class at
Publication: |
165/80.3 ;
165/104.33 |
International
Class: |
F28F 7/00 20060101
F28F007/00; F28D 15/00 20060101 F28D015/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 9, 2005 |
CA |
2,526,422 |
Claims
1. A passive thermal management system for dissipating heat
generated by a heat source, the thermal management system
comprising: (a) one or more heat pipes each having a length, each
heat pipe thermally connected to the heat source, each heat pipe
for transferring heat along its length away from the heat source;
and (b) a fin system thermally coupled to the one or more heat
pipes, the fin system extracting heat from the one or more heat
pipes and dissipating the heat therefrom, the fin system configured
to provide a desired level of heat dissipation independent of
orientation of the thermal management system.
2. The passive thermal management system according to claim 1,
wherein said fin system comprises a plurality of fins, said fins
aligned about parallel with the length of the one or more heat
pipes.
3. The passive thermal management system according to claim 1,
wherein said fin system comprises a plurality of fins, said
plurality of fins positioned in a stacked configuration with a
predetermined separation therebetween.
4. The passive thermal management system according to claim 3,
wherein said fins are aligned about perpendicular with the length
of the one or more heat pipes.
5. The passive thermal management system according to claim 3,
wherein each of said fins comprise one or more primary holes
therein for insertion of a heat pipe.
6. The passive thermal management system according to claim 3,
wherein each of said fins comprise one or more secondary holes
therein for enabling fluid to pass therethrough.
7. The passive thermal management system according to claim 3,
wherein said fins are configured in a shape selected from the group
comprising planar, bi-planar, curved, conical, cylindrical and
frusto-conical.
8. The passive thermal management system according to claim 3,
wherein said fins are have a cross section which comprises two
sloped portions and one flat portion.
9. The passive thermal management system according to claim 3,
wherein said fins are formed from a material selected from the
group comprising aluminium, copper, metal, alloy, ceramic, metal
ceramic composite and thermally conductive polymer.
10. The passive thermal management system according to claim 3,
wherein said fins are formed from two or more thermally conductive
materials.
11. The passive thermal management system according to claim 1,
wherein the fin system is thermally coupled to the one or more heat
pipes using a method selected from the group comprising welding,
brazing, interference connection, epoxy, soldering and thermally
conductive adhesive.
12. The passive thermal management system according to claim 3,
wherein each of said fins are configured as a bi-planar fin
comprising a centrally located secondary hole therein.
13. The passive thermal management system according to claim 12,
wherein each of said fins comprise one or more holes therein, each
of the one or more holes for insertion of one of the one or more
heat pipes.
14. The passive thermal management system according to claim 12,
wherein each the bi-planar fin has two planes which an intersection
angle therebetween, said intersection angle ranges between about 40
degrees and about 140 degrees.
15. The passive thermal management system according to claim 13,
wherein said intersection angle ranges between about 60 degrees and
about 120 degrees.
16. The passive thermal management system according to claim 13,
wherein said intersection angle ranges between about 80 degrees and
100 degrees.
17. The passive thermal management system according to claim 1,
wherein the passive thermal management system is coupled to a
lighting device and wherein the fin system is configured as a
portion of a housing for the lighting device.
18. The passive thermal management system according to claim 17,
wherein the fin system is configured to form an entire housing for
the lighting device.
Description
FIELD OF THE INVENTION
[0001] The present invention pertains to thermal management and in
particular to a passive thermal management system.
BACKGROUND
[0002] Typical thermal management devices, especially those
designed to incorporate heat pipes, are designed for one
orientation to ensure proper airflow for efficient performance of
the device. For example, heat sinks can be used to extract heat
from a heat source and are designed based on the proximate airflow
conditions and can vary greatly in shape and construction. For
applications that allow the inclusion of a fan, the design of a
heat sink can provide tightly spaced fins to reduce size, while
enabling air to pass freely. If the fan malfunctions, for example,
air movement will likely be limited due to the spacing constraints,
thus rendering the heat sink substantially ineffective. Passive
thermal management devices rely on buoyancy driven flow, or natural
convection. Essentially, the air is heated by the heat sink,
resulting in a reduction in the density of the air, which allows
this heated lower density air to rise, thus inducing airflow. This
type of system typically requires larger spaces between fins
associated with the heat sink, and the orientation and shape of
those fins can be critical. If the fins are parallel to the
gravitational vector, as the lower density air rises, it passes
over the surface of the fins and increases the heat transfer
coefficient. If the fins are oriented perpendicular to the
gravitational vector, the lower density air will rise, however the
flow of the air will typically not pass over the surface of the
fins, and therefore will likely not improve the heat transfer
coefficient.
[0003] U.S. Pat. No. 5,921,315 describes a heat pipe heat exchanger
that is provided in the form of a serpentine heat pipe that does
not have the ends of the individual tubes manifolded to one another
via a straight pipe or via any other common connector. Instead, the
heat pipes are connected via U-bends to form a continuous coil. The
serpentine heat pipe may include integral condenser and evaporator
portions separated by a divider to form a one-slab heat exchanger,
or separate evaporator and condenser coils connected to one another
by vapour and return lines to form a two-section heat pipe. The
heat pipe heat exchanger may be formed in a continuous closed-loop
pipe.
[0004] U.S. Patent Application No. 2005/0231983 describes a method
and apparatus for using light emitting diodes for curing and
various solid state lighting applications. The method includes a
method for cooling the light emitting diodes and mounting the same
on a heat pipe in a manner which delivers ultra high power in UV,
visible and IR regions. Furthermore, the LED packaging technology
utilizes heat pipes that perform efficiently in compact spaces.
Much more closely spaced LEDs operating at higher power levels and
brightness are possible because the thermal energy is transported
in an axial direction down the heat pipe and away from the
light-emitting direction rather than a radial direction in nearly
the same plane as the "p-n" junction. A heat pipe is bonded to a
heat sink that has fins that may be machined, or moulded in place.
The fins on the heat sink may be either radial and/or at an angle
in relation to the heat pipes and/or they may be axially
disposed.
[0005] European Patent Application No. 02006194.1 describes an
antenna for performing wireless transmission of voice or data to a
base station connected to a basic network. The antenna is
accommodated in a case in which a heat sink is provided. The heat
sink is disposed at the rear surface of the case. The heat sink is
disposed so as to form a predetermined tilt angle such that
radiating fins of the heat sink are disposed to form an acute angle
of about 45.degree. with respect to, e.g., a direction of gravity
in any one of the state of the vertically polarized wave and the
state of the horizontally polarized wave. The heat sink is
thermally coupled via the case to the high-frequency circuit
portion within the accommodating portion of the case. Thus, even if
the case is rotated 90.degree. such that the antenna is set to
either the direction of the vertically polarized wave and the
direction of the horizontal polarized wave, the heat sink takes two
substantially symmetrical positions where radiating fins are tilted
about 45.degree. with respect to the direction of gravity, while
being thermally coupled to the high-frequency circuit portion.
[0006] U.S. Pat. No. 7,048,412 describes a lamp having LED sources
that are placed about a lamp axis in an axial arrangement. The lamp
includes a post with post facets where the LED sources are mounted.
The lamp includes a segmented reflector for guiding light from the
LED sources. The segmented reflector includes reflective segments
each of which is illuminated primarily by light from one of the
post facets (e.g., one of the LED sources on the post facet). The
LED sources may be made up of one or more LED dies. The LED dies
may include optic-on-chip lenses to direct the light from each post
facet to a corresponding reflective segment. The LED dies may be of
different sizes and colors chosen to generate a particular
far-field pattern. This application further describes the use of
heat pipes to increase thermal conduction away from LED sources and
mounting of heat pipes to a heat sink. The heat sink, in one
embodiment, consists of fins attached to the surface of the heat
pipe.
[0007] U.S. Patent Application No. 2002/0179284 describes a device
for enhancing cooling of electronic circuit components. A thin
profile thermosyphon heat spreader mounted to an electronics
package comprises a central evaporator in hydraulic communication
with a peripheral condenser, both at least partially filled with
liquid coolant. Performance is optimized by keeping the evaporator
substantially full at all orientations while leaving a void for
accumulation of vapour in the condenser. The device may further
include means for cooling the condenser such as cooling fins and
liquid-cooled jackets that surround the condenser.
[0008] The thermal management systems as defined in the prior art
are primarily orientation dependent in order to enable appropriate
functioning thereof. Therefore there is a need for a new passive
thermal management system which can provide heat transfer
independent of orientation and can enable the transfer of heat away
from a heat source and dissipation of this heat to the
environment.
[0009] This background information is provided to reveal
information believed by the applicant to be of possible relevance
to the present invention. No admission is necessarily intended, nor
should be construed, that any of the preceding information
constitutes prior art against the present invention.
SUMMARY OF THE INVENTION
[0010] An object of the present invention is to provide a passive
thermal management system. In accordance with an aspect of the
present invention, there is provided a passive thermal management
system for dissipating heat generated by a heat source, the thermal
management system comprising: one or more heat pipes each having a
length, each heat pipe thermally connected to the heat source, each
heat pipe for transferring heat along its length away from the heat
source; and a fin system thermally coupled to the one or more heat
pipes, the fin system extracting heat from the one or more heat
pipes and dissipating the heat therefrom, the fin system configured
to provide a desired level of heat dissipation independent of
orientation of the thermal management system.
BRIEF DESCRIPTION OF THE FIGURES
[0011] FIG. 1 illustrates a side view of a passive thermal
management system according to one embodiment of the present
invention which is coupled to a light-emitting diode heat
source.
[0012] FIG. 2 illustrates a cross sectional view of half of a fin
system used for the passive thermal management system of FIG.
1.
[0013] FIG. 3 illustrates a cross sectional view of a passive
thermal management system of FIG. 1.
[0014] FIG. 4 illustrates a side view of a passive thermal
management system according to another embodiment of the present
invention.
[0015] FIG. 5 illustrates a cross sectional view of a passive
thermal management system according to another embodiment of the
present invention.
[0016] FIG. 6 illustrates a cross sectional view of a passive
thermal management system according to another embodiment of the
present invention.
[0017] FIG. 7 illustrates a side view of a passive thermal
management system according to another embodiment of the present
invention.
[0018] FIG. 8 illustrates a perspective view of a fin for use in
the fin system of the passive thermal management system of FIG.
7.
[0019] FIG. 9 illustrates a perspective view of another fin for use
in the fin system of the passive thermal management system of FIG.
7.
[0020] FIG. 10A illustrates a cross sectional view of a passive
thermal management system according to one embodiment of the
present invention.
[0021] FIG. 10B illustrates a cross sectional view of a fin for use
in the fin system of the passive thermal management system of FIG.
10A.
[0022] FIG. 11A illustrates a cross sectional view of a passive
thermal management system according to one embodiment of the
present invention.
[0023] FIG. 11B illustrates a cross sectional view of a fin for use
in the fin system of the passive thermal management system of FIG.
11A.
[0024] FIG. 12 illustrates a perspective view of a fin for use in a
fin system according to one embodiment of the present
invention.
[0025] FIG. 13 illustrates a cross sectional view of a passive
thermal management system according to one embodiment of the
present invention.
[0026] FIG. 14 illustrates a cross sectional view of a fin for use
in a fin system of the passive thermal management system of FIG.
13.
[0027] FIG. 15 illustrates a blank for the manufacture of a fin
according to one embodiment of the present invention.
[0028] FIG. 16 illustrates a fin manufactured from the blank
illustrated in FIG. 15.
[0029] FIG. 17 illustrates a blank for the manufacture of a fin
according to one embodiment of the present invention.
[0030] FIG. 18 illustrates a fin manufactured from the blank
illustrated in FIG. 17.
[0031] FIG. 19 illustrates a passive thermal management system
according to one embodiment of the present invention.
[0032] FIG. 20 illustrates a single fin of the fin system of the
passive thermal management system illustrated in FIG. 19.
[0033] FIG. 21 illustrates a blank for the manufacture of the fin
illustrated in FIG. 20.
[0034] FIG. 22A illustrates a side view of the fin illustrated in
FIG. 20.
[0035] FIG. 22B illustrates an end view of the fin illustrated in
FIG. 20.
[0036] FIG. 23 illustrates a cross sectional view of a passive
thermal management system according to another embodiment of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
Definitions
[0037] The term "heat source" is used to define a source of heat
from which the heat is to be extracted or transferred therefrom. A
heat source can be an electronic device, light-emitting device,
laser diode, light-emitting diode, semiconductor based device or
other similar device as would be known to a worker skilled in the
art, which is capable of heat generation.
[0038] As used herein, the term "about" refers to a +/-10%
variation from the nominal value. It is to be understood that such
a variation is always included in any given value provided herein,
whether or not it is specifically referred to.
[0039] Unless defined otherwise, all technical and scientific terms
used herein have the same meaning as commonly understood by one of
ordinary skill in the art to which this invention belongs.
[0040] The present invention provides a passive thermal management
system which provides a means for transferring heat away from a
heat source. The system comprises a heat pipe which is thermally
coupled to the heat source. The heat pipe is capable of
transferring heat away from the heat source, wherein this heat is
transferred along the heat pipe. Thermally coupled to the heat pipe
is a fin system, which provides a means for extraction of the heat
from the heat pipe and transfer of this heat to the environment
thereby dissipating the heat generated at the heat source. The fin
system is configured to provide a desired level of heat transfer to
the environment independent of the orientation of the thermal
management system, for example the orientation of the thermal
management system relative to the gravitational vector.
[0041] FIG. 1 illustrates a passive thermal management system
according to one embodiment of the present invention. The thermal
management system provides for the dissipation of heat that is
generated by one or more light-emitting diodes 10 which are
thermally coupled to the passive thermal management system, and
more specifically a heat pipe 14. For example, the thermal
connection between the one or more light-emitting diodes and a heat
pipe can be provided via substantially direct contact, through a
LED package or via a thermally conductive substrate upon which the
one or more light-emitting diodes are mounted. The thermal
management system comprises heat pipe 14 which is thermally
connected to a fin system 12 which is configured as a sleeve of
fins. Each of the fins of the sleeve of fins are substantially
aligned along the length of a heat pipe. The sleeve of fins
functions as a heat sink and thereby passively transfers heat from
a heat pipe to the surrounding environment, thereby reducing the
effect that the heat generated by the one or more light-emitting
diodes has thereon.
Heat Pipe
[0042] The one or more heat pipes are configured to be in thermal
contact with the one or more heat sources, wherein the one or more
heat pipes are configured to transport the heat generated by the
heat sources away therefrom.
[0043] A heat pipe is a device that can quickly transfer heat from
one point to another. A typical heat pipe is formed from a sealed
hollow tube, which is typically manufactured from a thermally
conductive material, for example aluminium or copper, however other
materials can be used as would be readily understood. A heat pipe
contains a working fluid therein and an internal wicking structure
which provides a means for liquid phase working fluid to return to
the evaporator end of the heat pipe. A heat pipe is capable of heat
transfer against the gravitational vector through an
evaporation-condensation cycle of the working fluid with the aid of
the internal wicking structure.
[0044] The wicking structure allows the capillary driving force to
return the condensate of the working fluid to the evaporator end of
the heat pipe. Different types of wicking structures are used
depending on the application for which the heat pipe is being used
including sintered, grooved or mesh structures. Working fluids can
range from liquid helium for extremely low temperature applications
to mercury for high temperature conditions.
[0045] For a thermal management system that includes multiple heat
pipes, the heat pipes can be configured such that they are
substantially similar or the heat pipes can be configured as
substantially different. For example, the multiple heat pipes can
be manufactured from the same or different materials, use the same
or different working fluids and wicking structures. The selection
of these materials for heat pipe manufacture can be dependent on
the intended use of the thermal management system and the
conditions for desired operation. A worker skilled in the art would
readily understand how to select one or more appropriate heat pipes
for the thermal management system, based on intended use.
Fin System
[0046] The fin system is thermally coupled to the one or more heat
pipes and configured to extract heat from the one or more heat
pipes and dissipate this extracted heat to the environment. The fin
system comprises one or more fins which are configured to enable
the dissipation of heat independent of the operational orientation
of the thermal management system.
[0047] For example, the fin system is configured to provide a
desired level of heat dissipation wherein this desired level can be
achieved independent of the orientation of the thermal management
system relative to the gravitational vector. A desired level of
heat dissipation by a thermal management system positioned in a
particular orientation relative to the gravitational vector can be
achieved if a desired level of convention can be obtained in that
orientation, namely a desired level of air movement over the fin
system, thereby enabling heat transfer to the air via the fin
system and subsequently transport away from the thermal management
system.
[0048] In one embodiment of the present invention, each of the one
or more fins of the fin system are configured to enable air
movement in a direction substantially parallel to the gravitational
vector independent of the orientation of the fin system, such that
the air moves over a portion or all of the surface area of the
fins.
[0049] In one embodiment of the present invention, the thermal
management system is operatively coupled to a lighting device,
wherein the thermal management system comprises a fin system
configured as a portion or the entire housing of the lighting
device. The fin system can define the exterior surface area of a
portion or all of the housing. In one embodiment the fin system can
be configured to define the exterior surface area of a portion or
all of the housing and additionally comprises exterior fins mounted
on the exterior surface area thereof. These exterior fins may
enhance the heat dissipation provided by the fin system.
[0050] In one embodiment of the present invention, the fin system
comprises a plurality of fins, wherein a desired amount of the
surface area of each of the fins is in environmental contact, for
example in direct contact with air, and is configured to enable a
desired level of heat to be transferred to the air via the fin
system.
[0051] In one embodiment of the present invention, the one or more
fins of the fin system can be configured in one, more than one or a
combination of a plurality of shapes for example, planar,
bi-planar, curved, conical, frusto-conical, cylindrical, or other
configuration as would be readily understood by a worker skilled in
the art. The selection of the shape of the one or more fins can be
determined based on the desired level of heat transfer from the
fins to the environment in one or more of the operational
orientations.
[0052] In one embodiment of the present invention, the one or more
fins of the fin system comprise one or more primary holes
therethrough for insertion of the one or more heat pipes. In
another embodiment, the one or more fins of the fin system comprise
one or more secondary holes therethrough to enable fluid passage
therethrough, for example to enable air, cooling fluid or other
medium to pass therethrough.
[0053] In one embodiment of the present invention, the fin system
comprises a plurality of similarly configured fins that are
positioned in a stacked configuration with a predetermined
separation therebetween.
[0054] The fin system can be manufactured from one or more of a
variety of materials provided that these materials have a desired
level of thermal conductivity and can retain a desired shape. For
example, the fin system can be manufactured from aluminium, copper
or other type of thermally conductive metal or alloy. The fin
system may be manufactured from a thermally conductive polymer,
ceramic, metal ceramic composite or other type of material as would
be readily understood by a worker skilled in the art.
[0055] In one embodiment of the present invention, the fin system
can be manufactured from multiple types of materials, which can be
selected based on the desired functionality of portions of the fin
system. For example, the portion of the fin system proximate to the
one or more heat pipes may be formed from a weldable or solderable
material, and the remainder of the fin can be manufactured from a
thermally conductive polymer. Other materials and material
configurations would be readily understood by a worker skilled in
the art. For example, multi material fins may be used in situations
where weight is a consideration, while maintaining a desired
material in the vicinity of the thermal connection between a fin
and a heat pipe.
[0056] The connection between the fin system and the one or more
heat pipes can be enabled by one or more of a variety of methods.
For example, the fin system and the one or more heat pipes can be
connected by welding, brazing, interference connection, epoxy,
soldering, thermally conductive adhesive or other means of
connection as would be readily understood by a worker skilled in
the art.
[0057] In one embodiment the thermal transfer between the heat pipe
and the fin system can be enhanced with thermal grease or another
highly thermally conductive material as would be readily understood
by a worker skilled in the art.
[0058] The invention will now be described with reference to
specific examples. It will be understood that the following
examples are intended to describe embodiments of the invention and
are not intended to limit the invention in any way.
EXAMPLE 1
[0059] FIG. 1 illustrates a passive thermal management system
according to one embodiment of the present invention. The thermal
management system provides for the dissipation of heat that is
generated by one or more light-emitting diodes 10 which are
thermally coupled to the passive thermal management system, and
more specifically heat pipe 14. For example, the thermal connection
between the one or more light-emitting diodes and a heat pipe can
be provided via substantially direct contact, through a LED package
or via a thermally conductive substrate upon which the one or more
light-emitting diodes are mounted. The thermal management system
comprises heat pipes 14 which are thermally connected to a fin
system 12 which is configured as a sleeve of fins. Each of the fins
of the sleeve of fins are substantially aligned along the length of
a heat pipe. The sleeve of fins functions as a heat sink and
thereby passively transfers heat from a heat pipe to the
surrounding environment, thereby reducing the effect that the heat
generated by the one or more light-emitting diodes has thereon.
[0060] In the embodiment illustrated in FIG. 1, the fin system
comprises two half sections 16, one of which is illustrated in FIG.
2. These half sections may be manufactured using an extrusion
technique or other manufacturing technique as would be readily
understood. Two of these half sections are coupled together, for
example by one or more bolts, clamps or other coupling device, to
form the fin system 12. The fin system surrounds a heat pipe 14
such that the fin system is in thermal contact therewith, as
illustrated in FIG. 3, wherein this thermal contact therebetween
may be enhanced by thermal grease or other thermal transfer
enhancing substance as would be readily understood by a worker
skilled in the art. In this manner, heat generated by the one or
more light-emitting diodes is transported away therefrom by the
heat pipe to the fin system and is subsequently transferred to the
surrounding environment.
[0061] In one embodiment of the present invention, a plurality of
passive thermal management systems as illustrated in FIG. 1 can be
configured in a circle for example. In this configuration, however,
the fin systems may isolate the central region which they surround.
This configuration can reduce the heat dissipation provided by the
fin system 20 as the fins within the central region are not
necessarily exposed to air movement. Therefore, in one embodiment
of the present invention and as illustrated in FIG. 4, the heat
pipes 22 can be bent in a manner that the central region 21 is
exposed enabling air to move therethrough, thereby increasing the
dissipation of heat by the fin system, said heat being generated by
a heat source 24.
[0062] In another embodiment of the present invention the fin
system can be formed as an extrusion with a sun type configuration
which comprises a plurality of fins 26 as illustrated in FIG. 5. In
this configuration the fins 26 of the fin system can run along the
length of the heat pipe 28. In one embodiment of the present
invention the fin system can be manufactured with a slightly
smaller internal opening compared to the heat pipe diameter. This
relative size configuration between the fin system and the heat
pipe, can provide a substantially tight interference connection
between the heat pipe and the fin system and thereby may enhance
thermal connection therebetween. In one embodiment the fin system
is manufactured from a thermally conductive material with elastic
properties which can enable the insertion of a heat pipe into the
internal opening of the fin system. These materials can include
metals and alloys provided that during the required deformation for
heat pipe insertion, the stresses induced within the material
remain within the elastic region. In an alternate embodiment of the
present invention, the fin system as illustrated in FIG. 5 can be
manufactured from a material which has a desired thermal expansion
coefficient, wherein the fin system is appropriately heated for
insertion of the heat pipe into the internal opening. As would be
readily understood, the thermal coefficient must be selected such
that under operational conditions the fin system does not expand an
amount that can diminish the thermal transfer between the fin
system and the heat pipe below a predetermined level.
[0063] In one embodiment of the present invention wherein there are
two or more heat pipes within the thermal management system, the
fin system comprising a plurality of fins 32 and can be configured
to wrap around the heat pipes 30 as illustrated in FIG. 6. This
embodiment of the fin system can be formed by extrusion, casting or
other method as would be readily understood by a worker skilled in
the art.
EXAMPLE 2
[0064] In another embodiment of the present invention, the thermal
management system comprises a fin system including two or more flat
plate fins 34 that are thermally connected to one or more heat
pipes 36 transverse to the length of each of heat pipes as
illustrated in FIG. 7. These plate fins can be manufactured with
one or more holes 38 therein for the insertion of a heat pipe
therethrough as illustrated in FIG. 8.
[0065] In another embodiment, the plate fins can be manufactured
with a plurality of holes 41 for the insertion of heat pipes and
additionally include secondary holes 40 and 42 therein which can
enable the passage of air therethrough, as shown in FIG. 9. The
secondary holes 40 and 42 in adjacent plate fins can be aligned
along the length of the heat pipes. Alternately the secondary holes
in adjacent plate fins can be offset thereby providing a means for
changing the direction of air movement along the length of the heat
pipe, wherein the change in directional movement of the air may
enhance heat transfer from the fins to the air, for example.
EXAMPLE 3
[0066] FIG. 10A illustrates a configuration of the passive thermal
management system for dissipating heat generated by a heat source
located at end 45 according to another embodiment of the present
invention. The thermal management system comprises one or more heat
pipes 46 and a fin system comprising a plurality of curved fins 44.
A single curved fin of the fin system is illustrated in FIG. 10B.
The shape of the fins of the fin system is configured wherein the
cool air enters into the passive thermal management system at a
first velocity in a first direction 48 and is subsequently slowed,
increasing thermal transfer thereto. The heated air thereafter
exits the thermal management system at a second velocity in a
second direction 50.
[0067] FIG. 11A illustrates a configuration of the passive thermal
management system for dissipating heat generated by a heat source
located at end 56 according to another embodiment of the present
invention. The thermal management system comprises one or more heat
pipes 58 and a fin system comprising a plurality of curved fins 54.
A single curved fin of the fin system is illustrated in FIG. 11B.
The shape of the fins of the fin system is configured wherein the
cool air enters into the passive thermal management system at a
first velocity in a first direction 60 and is subsequently increase
in speed, thereby providing a means for the heated air to exit the
fin system at an accelerated second speed in a second direction 62,
which is substantially parallel to the gravitational vector. In
particular the exiting direction of the heated air is substantially
parallel to the gravitational vector and in a direction which is
similar to that which would be passively induced by this
gravitational vector and therefore heat removal may be
enhanced.
EXAMPLE 4
[0068] FIG. 12 illustrates a fin for use in the fin system
according to another embodiment of the present invention. The fin
can be configured as a cone having a secondary hole 74 therein in
addition to the holes 72 manufactured for the insertion of the heat
pipes. The secondary hole can provide a location for the heated air
to pass along the length of the heat pipe, wherein for a stack of a
plurality of this fin configuration, this secondary hole can be
aligned. These aligned secondary holes can thereby enable air
movement in a manner similar to that of a chimney. This
configuration of a fin of the fin system can provide a means for
enabling a level of air movement along the length of the heat pipe
and along the fins as well, thereby enhancing heat dissipation into
the environment.
EXAMPLE 5
[0069] FIG. 13 illustrates a cross sectional view of a thermal
management system according to another embodiment of the present
invention, wherein in this figure the heat source is positioned at
end 69 of the heat pipes. The thermal management system comprises
heat pipes 70 and a series of fins stacked in order that holes
therethrough are aligned enabling both heat pipe insertion and heat
air movement along the length of the heat pipes.
[0070] As illustrated in FIG. 13, cool air can enter the thermal
management system at a first velocity in a first direction 64,
wherein this cool air can be slowed down proximate to the heat pipe
thereby enabling heat transfer thereto, and subsequently
accelerated and directed towards an exit hole and thereby exits the
thermal management system in a direction 66, which is substantially
parallel and in substantially the opposite direction to the
gravitational vector.
[0071] FIG. 14 illustrates a perspective view of a fin for use in
the fin system as illustrated in FIG. 13. This fin comprises two
sloped portions 75 and 77 and a flat portion 73 which comprises
holes 78 for the insertion of the heat pipes. This fin
configuration can provide a means for capturing air moving along
the length of the heat pipe and redirecting this air along the
surface of the fin which may provide a means for enhancing heat
transfer from the fins to the moving air. This configuration of the
fin can further provide a means for the air to increase in velocity
towards the centre of the fin cross section subsequent to the
redirection at the flat portion 73, wherein the heat air can exit
though aperture 76. This configuration can enable the heated air to
travel along the length of the heat pipe in a manner that can
enhance the exit velocity thereof.
[0072] FIG. 15 illustrates a blank from which a fin can be formed,
wherein the fin is substantially configured as a flat disc. FIG. 16
illustrates a fin formed from the blank illustrated in FIG. 15,
after punching and bending into a three dimensional configuration.
During the punching process, aperture 76 and heat pipe insertion
holes 74 can be formed.
[0073] FIG. 17 illustrates another blank from which a fin can be
manufactured. This blank comprises a number of stress relief cuts
82 and 80 which can provide a means for limiting stress build-up
within the fin during the formation process, which may cause
ripping and/or tearing of the blank. FIG. 18 illustrates a final
fin shape which can be manufactured from the blank illustrated in
FIG. 17. During the punching process, aperture 84 and heat pipe
insertion holes 86 can be formed and upon punching the fin can be
bent into this configuration.
EXAMPLE 6
[0074] FIG. 19 illustrates a thermal management system according to
another embodiment of the present invention wherein the thermal
management system comprises a plurality of fins 90 which form the
fin system which are thermally connected to the heat pipes 88.
These fins are configured as having a shape similar to that of a
roof. A single fin according to this embodiment is illustrated in
FIG. 20, wherein this fin can be fabricated as a planar element and
bent along a single axis, thereby forming a bi-planar fin. The fin
comprises a plurality of primary holes 100 configured to receive
the heat pipes of the thermal management system and a centrally
located hole 98.
[0075] In a first orientation, the thermal management system is
oriented such that the heat pipes are substantially parallel to the
gravitational vector and the heat source is positioned at end 96 of
the thermal management system. In this orientation, as illustrated
in FIG. 19, the centrally located secondary hole 98 associated with
the fins of the fin system, essentially acts as a chimney for
heated air movement through and subsequently out of the thermal
management system in direction 94. In this orientation cool air can
be drawn from the side of the thermal management system
substantially in direction 92, wherein heating and acceleration of
the air occurs along the surface of the fins and the heated air is
subsequently expelled out the `chimney` or centrally located
secondary hole. This configuration of the fin system of the thermal
management system can provide a means for the top fins of the fin
system, namely the fins proximate to the exit hole or secondary
hole, to receive cold air and thus aid in improving the thermal
transfer efficiency of the fin system, as these upper fins are not
simply receiving air previously heated by lower fins of the fin
system.
[0076] When the thermal management system is oriented in the
opposite direction to that illustrated in FIG. 19, cool air can
enter the thermal management system through the centrally located
hole, be heated along the surface of the fins and subsequently exit
the thermal management system out the side of thereof.
[0077] In another orientation, for example when the heat pipes are
oriented perpendicular to the gravitational vector, the fins of the
fin system can substantially act as a series of vertical fins,
thereby providing a means for all the fins of the fin system to
draw in air that has not been pre-heated by other fins associated
with the fin system.
[0078] FIG. 21 illustrates a punched blank from which a fin for use
with the passive thermal management system as illustrated in FIG.
19 can be formed and FIG. 22A illustrates a front view of the fin
after bending into the desired configuration. In one embodiment of
the present invention, portions 101 of the blank can be removed
which can provide a means for reducing stresses induced within the
blank during the bending process and may further reduce buckling or
tearing of the blank during bending.
[0079] FIG. 22B illustrates an end view of the fin wherein the bend
can be formed at an angle 102, which can be determined based on the
desired air flow through the thermal management system having a fin
system comprising fins of this configuration. In one embodiment,
angle 102 can be between about 40.degree. to about 140.degree.. In
another embodiment, angle 102 can be between about 60.degree. to
about 120.degree.. In yet another embodiment, angle 102 can be
between about 80.degree. to about 100.degree.. The geometric
configuration of the holes that are punched or formed within the
blank are designed in order that upon bending of the fin, an
appropriate hole geometry is realized for a desired heat pipe to be
inserted while providing a desired level of thermal contact between
the heat pipe and the fin. For example, in one embodiment the holes
can be punched as ellipses wherein upon bending, and subsequent
viewing from above, the holes may appear as circles. As would be
readily understood by a worker skilled in the art, the shape of the
holes created for the insertion of a heat pipe, is directly
dependent on the selection of angle 102.
EXAMPLE 7
[0080] FIG. 23 illustrates a passive thermal management system
according to another embodiment of the present invention, wherein
the passive thermal management system is coupled to a lighting
device. The thermal management system provides for the dissipation
of heat that is generated by one or more light-emitting diodes 200
which are thermally coupled to the passive thermal management
system, and more specifically one or more heat pipes 202, 203. For
example, the thermal connection between the one or more
light-emitting diodes and the one or more heat pipes can be
provided via substantially direct contact, through a LED package or
via a thermally conductive substrate upon which the one or more
light-emitting diodes are mounted. The thermal management system
comprises one or more heat pipes 202, 203 which are thermally
connected to a fin system 204. The fin system 204 is configured as
the housing of the lighting device and in this configuration the
fin system 204 forms as an exterior surface area. In one embodiment
of the present invention this fin system can further comprise one
or more external fins which may enhance heat transfer from the fin
system to the environment.
[0081] In one embodiment heats pipe 202 of the thermal management
system can be straight and transfer heat to the end 206 of the fin
system 204. In another embodiment of the present invention, one or
more of heat pipe 203 may be bent in order that thermal connection
between the heat pipe and the fin system can be provided along a
portion of the length of the heat pipe, which can enhance heat
transfer to the fin system. In another embodiment of the present
invention, the thermal management system can comprise both bent and
straight heat pipes.
[0082] In one embodiment of the present invention, the fin system
which forms the housing can comprise one or more openings therein
thereby enabling environmental access to the interior volume 212
defined in part by the fin system 204, thereby aiding in the
dissipation of any heat that may have otherwise been partially
trapped within this interior volume. The one or more openings can
be configured as holes or slits or other configurations as would be
readily understood by a worker skilled in the art.
[0083] As illustrated in FIG. 23, the fin system 204 can retain or
mate with a transparent window 208 which may cover the optics 210
associated with the one or more light-emitting diodes.
[0084] It is obvious that the foregoing embodiments of the
invention are exemplary and can be varied in many ways. Such
present or future variations are not to be regarded as a departure
from the spirit and scope of the invention, and all such
modifications as would be obvious to one skilled in the art are
intended to be included within the scope of the following
claims.
* * * * *