U.S. patent application number 10/157290 was filed with the patent office on 2002-10-03 for heat sink with textured regions.
Invention is credited to Azar, Kaveh.
Application Number | 20020139515 10/157290 |
Document ID | / |
Family ID | 23353058 |
Filed Date | 2002-10-03 |
United States Patent
Application |
20020139515 |
Kind Code |
A1 |
Azar, Kaveh |
October 3, 2002 |
Heat sink with textured regions
Abstract
A heat exchanger and a method of manufacturing the heat
exchanger is disclosed for dissipating heat from a heat generating
component. The heat exchanger comprises a thermally conductive base
in thermal communication with the component, a plurality of
thermally conductive plate fins affixed to the base wherein the
plate fins define a fin field and channels, and fluid control for
controlling the fluid flow within the fin field. The individual
fins of the heat exchanger comprise textured regions positioned
about a side surface of the fins and extending into an adjacent
channel. The positioning of the textured regions function to
minimize formation of high pressure within the fin field by
disturbing the fluid flow passing along the fins. Alternatively or
in conjunction with the above-outlined embodiments, the heat
exchanger may comprise a fluid control feature for substantially
preventing premature egress of fluid from a top region of the fin
field caused by the high pressure region within the fin field.
Inventors: |
Azar, Kaveh; (Westwood,
MA) |
Correspondence
Address: |
Lieberman & Brandsdorfer, LLC
12221 McDonald Chapel Drive
Gaithersburg
MD
20878-2252
US
|
Family ID: |
23353058 |
Appl. No.: |
10/157290 |
Filed: |
May 29, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10157290 |
May 29, 2002 |
|
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|
09345003 |
Jul 2, 1999 |
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Current U.S.
Class: |
165/80.3 ;
257/E23.099; 257/E23.103 |
Current CPC
Class: |
F28F 3/02 20130101; H01L
2924/0002 20130101; H01L 23/3672 20130101; H01L 23/467 20130101;
H01L 2924/0002 20130101; F28F 2215/08 20130101; H01L 2924/00
20130101 |
Class at
Publication: |
165/80.3 |
International
Class: |
F28F 007/00 |
Claims
What is claimed is:
1. A heat exchanger comprising: a thermally conductive base in
thermal communication with said component; a plurality of thermally
conductive plate fins affixed to said base to define a fin field;
said fins have a top region, a bottom region, an inlet region, and
an outlet region; said fins comprise a plurality of spaced apart
flow guides transverse to said inlet and outlet regions, said flow
guides traverse a portion of said top region and lie in a common
plane; and an interior plate fin includes a plurality of textured
portions extending outwardly from a surface of said fin:
2. The heat exchanger of claim 1, further comprising a side plate
fin having an aperture substantially contiguous with said base to
provide fluid communication across said channel.
3. The heat exchanger of claim 2, wherein said side fin comprises
textured portions extending outwardly from a surface of said
fin.
4. The heat exchanger of claim 1, further comprising an interior
fin having an aperture located substantially contiguous with said
base.
5. The heat exchanger of claim 1, wherein said textured portions
are elliptical in shape.
6. The heat exchanger of claim 1, wherein said plate fins comprise
an extension protruding from the top region of each discrete plate
fin, wherein alignment of the extension with an adjacent extension
forms said flow guide.
7. The heat exchanger of claim 1, wherein said flow guide is
selected from the group consisting of a horizontal bar, a flat bar,
a profiled bar, and a profiled bar having at least one point.
8. The heat exchanger of claim 1, wherein said flow guide covers a
sufficient portion of said top region to restrict ingress of fluid
and creating a near impingement condition.
9. The heat exchanger of claim 1, wherein said textured portions
increase pressure drop of fluid in said fin field.
10. A method of dissipating heat from a heat generating component,
comprising: affixing a heat sink apparatus adjacent to the heat
generating component, wherein said heat sink comprising a plurality
of thermally conductive plate fins affixed to a thermally
conductive base, and said plate fins defining a top region, a
bottom region, an inlet region, and an outlet region, said fins
further comprising providing a plurality of spaced apart flow
guides transverse to said inlet and outlet regions and lying in a
common plane, and providing a plurality of textured portions
extending outwardly from a surface of said interior fin.
11. The method of claim 10, further comprising forming eddy
currents in fluid passing through the heat sink.
12. The method of claim 10, further comprising providing an
aperture substantially contiguous with said base for enhancing
communication of fluid between an interior portion of said heat
sink apparatus and an area exterior to said heat sink
apparatus.
13. The method of claim 10, wherein said flow guide is selected
from the group consisting of a horizontal bar, a flat bar, a
profiled bar and a profiled bar having at least one point.
14. The method of claim 10, further comprising said flow guide
providing structural integrity to said heat exchanger.
15. The method of claim 10, further comprising said flow guide
imparting a downward force on fluid within the fin field.
16. The method of claim 10, further comprising said textured
portions disturbing fluid passing along said fin.
17. The method of claim 10, further comprising said textured
portions disrupting formation of a boundary layer.
18. The method of claim 10, wherein said textured portions increase
pressure of said fluid.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates generally to the cooling of
heat-producing electronic components, and more particularly, to a
heat exchanger having fluid control elements for deterring the
formation of high pressure within the heat exchanger and/or
reducing the premature egress of fluid from the heat exchanger
caused by the high pressure.
[0002] Effective dissipation of heat produced by electronic
components is an important concern in optimizing circuitry
performance. In addition to optimizing performance, effective heat
dissipation also helps to prolong the useful life of those
components. Heat dissipation is particularly important in the case
of high-power electronic components, such as microprocessors and
lasers, which generate a relatively high amount of heat in a
relatively small area.
[0003] Finding suitable heat exchangers to adequately dissipate the
heat generated by these components is a difficult task. These
components are typically used in systems housed within a cabinet
having a fan mounted in the back. The fan pulls cooling fluid,
usually air, across the electrical components mounted within. A
suitable heat exchanger should function adequately given this
environment. Exotic methods of cooling high-power electronic
components, such as forced liquid cooling, are undesirable due to
the high cost of implementation and maintenance in these systems.
Given their relative simplicity, traditional plate fin heat
exchangers are generally preferred from cost and implementation
perspectives. These exchangers offer high surface area for heat
exchange relative to their size. Nevertheless, often these devices
are inadequate to dissipate heat generated from high power
electronics, although improvements are being made.
[0004] Advances have been made involving the use of narrow channel
and micro-channel plate fin heat exchangers to cool electronic
components. For example, a patent issued to the applicant, Azar et
al., U.S. Pat. No. 5,304,846, discloses a narrow-channeled heat
exchanger with certain geometric relations aimed at improving the
heat dissipation of the heat exchanger. Specifically, the patent
teaches optimal ratios relating the height of the plate fins to the
width of the channels. The ratios can be selected to optimize the
heat dissipation capabilities of the heat exchanger for a given
pressure drop across the heat exchanger.
[0005] Although narrow channel heat exchangers significantly
improve heat dissipation, they, like all other plate fin designs,
suffer from boundary layer formation. The boundary layer consists
of hydrodynamic and thermal layers which result from friction or
drag between cooling fluid and a plate fin. The layer tends to
blanket the plate fin thereby insulating it from the cooler fluid
flow. This reduces heat transfer. Additionally, the layer narrows
the remaining channel available to fluid flow which further impedes
fluid flow thereby compounding the problem. The boundary layer
therefore thickens as the fluid progresses down the channel
contributing to high pressure within the fin field.
[0006] Efforts to reduce boundary layer formation in heat
exchangers include irregularities such as protrusions, indentations
and louvers along the plate fin surface. These irregularities are
intended to disturb the boundary layer to prevent it from building
up. From the standpoint of boundary layer disruption, the greatest
improvement would be a device having as many irregularities as
possible. Unfortunately, however, such an approach leads to
practical problems. First, it is difficult, if not impossible, to
extrude a plate fin having the desired surface irregularities.
Extrusion techniques are limited to producing lengthwise ridges
(horizontal and vertical) which have limited ability to disrupt the
boundary layer. Other manufacturing techniques such as casting and
machining also preclude intricate plate fin textures. Perhaps more
important though, increasing irregularities, as described above,
also decreases the velocity of the passing fluid within the
channels formed by the textured plate fins which tends to increase
pressure within the fin field.
[0007] The applicant has found that high pressure in the fin field
leads to inefficient heat transfer and premature egress of fluid
from the fin field. Therefore, a need exists for a flat fin heat
exchanger that deters high pressure formation, prevents the
premature egress of fluid from the fin field caused by the high
pressure, and/or minimizes boundary layer formation without
increasing pressure. The present invention fulfills this need.
SUMMARY OF THE PRESENT INVENTION
[0008] It is therefore the general object of the present invention
to provide an improved heat exchanger for dissipating heat from a
heat generating component, as well as a method of manufacturing the
novel heat exchanger. The heat exchanger comprises a thermally
conductive base in thermal communication with the component, a
plurality of thermally conductive plate fins affixed to the base
wherein the plate fins define a fin field and channels, and fluid
control for controlling the flow of fluid within the fin field to
minimize the formation of high pressure. Alternatively or in
conjunction, the fluid control substantially prevents premature
egress of fluid from the top of the fin field caused by the high
pressure within the fin field.
[0009] It is a further object of the invention to utilize the low
pressure created by flow by-pass to vent relatively high pressure
fluid within the fin field. To this end, the fluid control
comprises fluid communication between a portion of the channels and
at least one side of the fin field. The fluid communication enables
a portion of fluid within the fin field to be drawn out by the low
pressure caused by the flow by-pass. In this way, the formation of
high pressure within the fin field is substantially avoided.
Suitable fluid communication in this embodiment includes slots,
notches, orifices, or perforations through a fin, gaps or spaces
along a plate fin, and combinations thereof.
[0010] It is even a further object of the invention to provide a
novel heat exchanger comprising fluid control having flow guides
within the fin field. The flow guides are configured to impart a
downward force to a portion of fluid within the fin field to hamper
its premature exit out the top. Suitable flow guides include vanes
protruding from the plate fins, bars traversing the top of the fin
field, and combinations thereof.
[0011] In accordance with the invention, these and other objectives
are achieved by providing a novel heat exchanger of the present
invention. The heat exchanger comprises a plurality of thermally
conductive plate fins affixed to and in thermal communication with
a base. The individual fins are separated by channels. The fins,
together with the channels and base form a fin field having an
inlet region, a middle region and an outlet region. Each of the
individual plate fins comprise textured regions positioned about a
side surface of the fins and extending into an adjacent channel.
Accordingly, the positioning of the textured regions function to
minimize formation of high pressure within the fin field by
disturbing the fluid flow passing along the individual fins.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The features of the present invention, which are believed to
be novel, are set forth with particularity in the appended claims.
The invention may best be understood by reference to the following
description taken in conjunction with the accompanying drawings,
wherein like reference numerals identify like elements, and
wherein:
[0013] FIG. 1 shows a side view of a prior art heat exchanger;
[0014] FIG. 2 shows a top view of the prior art heat exchanger in
FIG. 1;
[0015] FIG. 3 shows a perspective view of the fluid dynamics
associated with a prior art heat exchanger;
[0016] FIG. 4 shows a perspective view in comparison to FIG. 3 of
the present invention's heat exchanger and its associated fluid
dynamics;
[0017] FIGS. 5-33 show various embodiments of the present
invention; and
[0018] FIG. 34 shows a process of configuring and assembling
discrete plate fins.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT AND BEST MODE OF
THE INVENTION
[0019] In this disclosure, the term "fin" (also called a "plate" or
"flat fin") refers to a substantially planar heat exchanging member
that extends at an angle, typically about 90 degrees, from a base.
Such a base may support a number of plate fins, in which case,
"channels" are defined between adjacent fins. The area within and
immediately about the cluster of plate fins is referred to as the
"fin field." It should be understood that the term "fluid" as used
herein refers to both liquids and gases. The flow of fluid across
the fin field can be created using known features such as fans and
natural convection.
[0020] Referring now to the drawings, FIGS. 1 and 2 show a prior
art configuration of a heat generating component 11 mounted to a
printed circuit board (PCB) 10 and adjacent to another PCB 24. A
prior art heat exchanger having individual plate fins 20 affixed to
a base 19 is mounted to the component 11. The plate fins 20 define
a fin field 12, and channels 23 through which cooling fluid 13
flows. The fin field 12 has a top 18, and intake and exhaust
regions 16, 17 respectively.
[0021] The combination of the heat generating component and the
heat exchanger forms a 3-dimensional protrusion into the flow of
fluid 14. As such, the prior art heat exchanger experiences certain
fluid dynamics which reduce its effectiveness, including boundary
layer formation, high pressure formation, and premature fluid
egress from the fin field.
[0022] Cooling fluid 13 entering the fin field through the channels
23 forms a boundary layer 22 along the sides of the plate fins as
shown in FIG. 2. The boundary layer is a region of heated, high
pressure fluid that forms as a result of the friction between the
plate fin 20 and fluid. The layer tends to blanket the plate fin
thereby insulating it from the cooler fluid flow. This reduces heat
transfer. Additionally, the layer narrows the remaining channel
available to fluid flow which further impedes fluid flow, thus,
compounding the problem. As shown in FIG. 2, the boundary layer 22
grows as the fluid 13 progresses down the channel, eventually
contributing to a region of near stagnant, high pressure fluid
within the fin field.
[0023] Fluid not only penetrates the fin field 12 and forms
boundary layers, but also flows over and around it. Fluid flowing
over and around the fin field 12 is referred to as "flow by-pass"
in this disclosure. Flow by-pass typically reduces the efficiency
of the fin field 12. Specifically, fluid 21 flows around the heat
exchanger 12 (see FIG. 2), turns and enters it from the exhaust
region 15. This also contributes to the near stagnant, high
pressure region 17 within the fin field 12. This problem is
exacerbated because the by-pass fluid contributing to the high
pressure region 17 comprises relatively hot fluid. That is, this
fluid travels around the fin field 12 in intimate contact with the
PCB. The PCB carries much of the heat generated by the components
mounted thereto, and consequently, the passing fluid is heated.
[0024] The high pressure caused by flow by-pass and boundary layer
formation impedes the fluid flow 13 through the fin field 12 and
contributes to its premature egress through the field's top 18.
Consequently, relatively cool fluid entering through the intake
region 16 of the fin field 12 is forced from the field. Thus, the
high pressure not only blankets the region in a hot layer that
retards efficient heat transfer, but also forces the relatively
cool fluid to leave the fin field prematurely.
[0025] The present invention recognizes the phenomena leading to
the formation of high pressure within the fin field and its
effects, and provides solutions aimed at preventing high pressure
from forming, and/or reducing its effects. In its basic embodiment,
the present invention provides for an improved heat exchanger for
dissipating heat from a heat generating component. The heat
exchanger comprises a thermally conductive base in thermal
communication with the component. Affixed to the base is a
plurality of thermally conductive plate fins. The plate fins define
a fin field having channels, a top, sides, an intake region, and an
exhaust region. The invention provides for fluid control for
controlling fluid flow within and around the fin field to perform
the following functions:
[0026] (1) deter the formation of high pressure fluid;
[0027] (2) reduce the premature egress of fluid from the top of the
fin field caused by high pressure fluid; and/or
[0028] (3) minimize boundary layer formation without forming high
pressure fluid.
[0029] 1. Deter High Pressure Formation
[0030] The present invention deters the formation of high pressure
by (a) venting the high pressure and/or (b) minimizing the friction
between the plate fin and the cooling fluid.
a. Venting
[0031] In a preferred embodiment, the flow control comprises
ventilation features to alleviate high pressure fluid within the
fin field and enhance the performance of the heat exchanger. The
ventilation features actually exploits the flow by-pass to achieve
this function. Fluid by-passing the fin field must travel a greater
distance in the same time as the fluid passing directly through the
fin field. Consequently, its velocity must increase. According to
Bernoulli's principle, a decrease in pressure accompanies an
increase in speed. A region of low pressure therefore covers the
top and lines the sides of the fin field. Although this low
pressure contributes to the premature egress of fluid from the fin
field, it can also be harnessed to improve heat exchanger
performance. The present invention uses the low pressure to draw
the high pressure fluid from the fin field.
[0032] The ventilation features can include fluid communication
between a portion of the channels and at least one side of the fin
field. The fluid communication enables a portion of fluid within
the fin field to be drawn out by the low pressure flow by-pass. The
fluid communication may include plurality of passageways within the
fin field. These passageways can be slots or notches within a plate
fin, gaps along a plate fin, perforations or orifices in a plate
fin, and the like, and combinations thereof. Alternatively, the
passageways may comprise traversing tubes or channels above or
below the fin field.
[0033] Yet another ventilation feature involves the radial
configuration of plate fins such that a portion of the channels
between the plate fins has access to the side of the fin field.
This enables a portion of fluid within the fin field to be drawn
out by the low pressure through the channels. Still other
ventilation features may be obvious to someone skilled in the art
once the stagnation problem and venting solution are
understood.
b. Minimizing Friction
[0034] In another embodiment, the fluid control can reduce high
pressure by minimizing the friction between the plate fins and the
fluid. A tapered plate fin, for example, provides for reduced
friction. The taper of the plate fin is designed such that the
plate fin's cross-sectional area relative to the direction of the
fluid flow decreases from the intake region to the exhaust region.
Less cross-sectional area corresponds to less friction or drag, and
thus, less reduction in fluid velocity. Alternatively, the plate
fins may be coated to reduce friction. As mentioned above, drag is
a major contributor to the boundary layer condition which
contributes greatly to high pressure within the fin field.
Therefore, by reducing drag, the present invention reduces the
formation of high pressure.
[0035] 2. Prevent Premature Egress
[0036] In another embodiment, the fluid control prevents the
premature egress of fluid from the top of the fin field caused by
the high pressure region within the fin field and by the low
pressure by-pass above it. One way to perform this function is
through the use of a flow guide within the fin field. Aside from
improving heat transfer by increasing the plate fin's surface area,
the flow guide is configured to impart a downward force to a
portion of the fluid within the fin field thereby hampering its
premature exit from the top of the fin field. The flow guide can be
a mechanism such as a vane protruding from a plate fin, a bar
traversing the tops of a portion of the plate fins, and
combinations thereof. The vanes can have various configurations
such as arcuate or straight, integral to the plate fin or discrete
and separately attached. In one preferred embodiment, the vane
comprises a disrupted section of the plate fin that is bent to
protrude from the plate fin. The bar too can assume a variety of
configurations. Suitable configurations include a flat bar, a
profiled bar, and a profiled bar having a point(s). In this
context, the term "profiled" refers to a significant profile or
cross-sectional area relative to the flow of the fluid. Other
suitable mechanisms will be obvious to someone skilled in the art
once the problem of premature egress is understood, and the ability
to curb it through fluid redirection is realized.
[0037] The use of a bar not only exerts a downward force on a
portion of fluid within the fin field, but also imparts other
improvements to the heat exchanger. The profiled bars retard fluid
flow above the fin field thereby forming a high pressure region.
Such a high pressure region substantially prevents a portion of
fluid from prematurely exiting the fin field, and may even present
a pressure gradient significant enough to cause ingress of fluid
through the fin field's top. Moreover, by using bars to cover a
significant portion of the fin field top and restrict the region of
fluid egress, fluid enters the fin field at a high velocity and at
an angle nearly normal to the base. This creates a near impingement
condition which is highly desirable in heat exchangers.
[0038] 3. Minimize Boundary Layer Formation
[0039] The flow control can also be used to reduce boundary layer
formation by fin surface enhancements such as texturing or other
surface anomalies. The texturing causes eddy currents in the fluid
flow that disrupt the boundary layer. Unfortunately, surface
irregularities also decrease fluid velocity which increases
pressure. It is therefore preferred that the fluid control for
deterring the formation of high pressure within the fin field be
used in combination with such texturing or surface anomalies.
[0040] Comparative Illustration
[0041] The improvements of the present invention can be more
readily understood in comparison to the prior art under dynamic
fluid conditions. FIG. 3 shows a perspective view of a typical heat
exchanger 31 and its attendant problems of fluid by-pass 32
including stagnation 33 and premature egress 34 from the top 36 of
the fin field 37. On the other hand, FIG. 4 shows one possible
combination of fluid control. Slots 41 in a plate fin 42 provide
ventilation to the low pressure region 43 caused by the flow
by-pass 47. Additionally, tapered plate fins 44 reduce the friction
with the fluid 45 entering the fin field 46 thereby reducing the
velocity drop and minimizing pressure increase. The combination of
the ventilation features and tapered plate fins serves to minimize
the formation of a high pressure region within the field. By
reducing high pressure formation, the premature egress of fluid 47
from the fin field 46 is also minimized if not reversed. That is,
the fluid control even tends to draw cool fluid 48 through the top
of the fin field 46. The addition of these fluid control features
results in a high performance heat exchanger that dissipates heat
more efficiently than the prior art.
[0042] Specific Embodiments
[0043] Referring to FIGS. 5-33, specific embodiments of the present
invention will now be considered in light of the principles above.
These embodiments depict various configurations of the fluid
control for (1) deterring the formation of high pressure, (2)
reducing premature egress of fluid from the field, and/or (3)
minimizing boundary layer formation. It should be understood that
the particular flow control illustrated by these figures should not
be construed to limit the scope of the invention, and may be
interchanged and varied to form infinite combinations.
[0044] FIG. 5 shows a heat exchanger having a series of plate fins
51 with holes or perforations 52. The plate fins 51 are mounted to
a base 54, and are further secured with bars 53 that traverse the
plate fins across their top. It should be understood that such bars
are optional in this embodiment as well as in the other embodiments
disclosed herein. The plate fins 51 define channels 56 there
between, and a plate fin field 57 and about. FIG. 5b depicts a
discrete plate fin 51 that can be configured according to a
particular application before being mounted to the base 54. The
discrete plate fin 51 has connection elements 55 for securing to
the base 54 and to other plate fins. In one embodiment, when a
series of discrete plate fins are mounted to the base, as shown in
FIG. 5a, the connection elements 55 on the top align and form the
individual bars 53. FIG. 5c shows a complementing plate fin 51
having connection elements 55 protruding from an opposite side
which may be used as a side plate fin to complete the heat
exchanger.
[0045] The bars 53 not only add structural integrity to the
assembly, but also act as flow control, specifically, flow guides
for imparting a downward force on the fluid attempting to exit.
Additionally, the perforations 52 in the plate fins 51 provide
fluid communication between the channels 56. This fluid
communication ventilates the stagnant region within the fin field
57.
[0046] Specifically, low pressure along the sides of the fin field
caused by the flow bypass as described above draws fluid from the
fin field 57 through the perforations 52. Additionally, these
perforations allow for omni-directional fluid flow. That is, the
alignment of the fin field is no 20 longer crucial since fluid can
flow either through the channels or across the channels. In the
latter case, the channels provide the ventilation to the region of
low pressure caused by the fluid by-pass.
[0047] FIG. 6a shows a heat exchanger having a series of plate fins
61 each having a slot 62 near the base 64. Several bars 63 traverse
the plate fins. A configurable plate fin 61 is shown in FIG. 6b as
a discrete component. The slots 62, like the perforations 52 in
FIG. 5a, allow for fluid communication between the channels and the
low pressure region caused by the fluid bypass. This way, high
pressure within the fin field vents to the sides. Likewise, the
slots allow for omni-directional flow thereby allowing the fin
field to be mounted in any direction relative to fluid flow.
[0048] FIG. 7a shows an alternative embodiment of the fin field
described in FIG. 6a. In this fin field, the same plate fin
structure is found in plate fin 71 with slot 72. However, the
interior plate fins 75 are comprised of thin flat fins or,
alternatively, pin fins 78. The various fins are connected by bar
73. FIG. 7b shows a discrete component of the heat exchanger
wherein fin 71 has a slot 72 and connection element 77 on top. When
the fin field is assembled, connection elements 77 align to form
the bar 73. FIG. 7c shows a side view of the fin 71. The
configuration of this fin field allows for a generous space 76
between the fin segments. Such a space facilitates easy fluid
communication to provide the benefits as mentioned above.
[0049] FIG. 8a shows a series of plate fins 81 having the same
configuration as the interior fins of FIG. 7a. A configurable plate
fin 81 is shown in FIG. 8b as a discrete component. Both the
interior and exterior plate fins have substantially similar
structure. FIG. 8d is a side elevational view of a discrete plate
fin, illustrating the connection element 86 extending from the top
surface of each plate fin 81. FIG. 8b is a front elevational view
of a discrete plate fin, illustrating the vertical bar elements 87
evenly spaced along the length of the plate fin 81 and the spacing
82 between each of the bars. FIG. 8c shows a side view of a
discrete plate fin, illustrating the vertical bar elements 81 and
the connection elements 86. The spacing between each vertical bar
element, together with the alignment of the plate fins 81 as
illustrated in FIG. 8a provides for improved fluid communication
across the side plate fins. As the plate fins 81 are assembled, the
connection elements 86 form the transverse bars 83 as illustrated
in FIG. 8a. Accordingly, the fin field of FIG. 8a is better suited
for omni directional flow applications.
[0050] FIGS. 9a through 9d show a variety of different features for
providing fluid communication between the plate fins. FIG. 9a shows
a rectangular orifice 91, a triangular orifice 92, an oval orifice
93, a square orifice 96, a round orifice 94, and a circular orifice
95. FIG. 9b shows a plate fin having a slot 97 located at its
bottom, while FIG. 9c shows a series of slots 98 located at the
bottom. A variety of different fin slits 99 are shown in FIG.
9d.
[0051] FIG. 9e illustrates a fin perforated with flow guides. The
flow guides illustrated are straight, angled and curved in both
upward and downward directions. Accordingly, each individual fin
can have surface cutouts for accommodating the fluid flow through
the fins.
[0052] FIGS. 10a and 10b show a perspective and top view
respectively of a heat exchanger having plate fins 101 radially
disposed on a base such that a portion of channels 102 is exposed
to the side of the heat exchanger. This configuration allows the
low pressure caused by flow bypass to draw fluid through the
channels 102. The configuration is further improved by having bars
104 located on the tops of plate fins. The bars not only guide flow
but also add structural integrity to the heat exchanger.
[0053] FIG. 11a shows a heat exchanger having plate fins 111 with
flow guides 112 mounted thereon. A discrete plate fin component of
the heat exchanger is shown in FIG. 11b. The flow guides 112 in
this particular embodiment are curved downward relative to the
direction of fluid flow. Thus, if the fluid flow direction is from
the bottom left-hand side of the drawing to the top right-hand
side, the configuration of the flow guides forces the fluid in a
downward direction.
[0054] FIG. 12a shows a variation of the exchanger in FIG. 11. In
this exchanger, slots 124 are added to plate fins 121 of the
interior plate fins while a slot 123 is added to plate fin 121 of
the exterior plate fins. FIGS. 12b and 12c show the discrete plate
fin components of the interior and exterior configuration,
respectively.
[0055] More particularly, FIG. 12 illustrates an interior fin 122
with flow guides 125 similar to that disclosed in FIG. 11b. The
flow guides 125 illustrated in FIGS. 12a and 12b are vanes curved
in a downward direction relative to the direction of fluid flow.
Each of the exterior plate fins 121 comprises a slot 123 similar to
the exterior fin 71, as illustrated in FIGS. 7a and 7c. In
addition, as the interior and exterior fins are assembled to form
the heat exchanger as illustrated in FIG. 12a, the heat exchanger
comprises several bars 126 which transverse the plate fins. The
transverse bars 126, similar to those disclosed in several
embodiments disclosed herein, add structural integrity to the heat
exchanger 120, as well as act as a flow control for imparting a
downward force on the fluid attempting to exit the heat exchanger
through the top region.
[0056] FIG. 13 shows a variety of different flow guides. A
preferred louvered flow guide is shown in FIG. 13a. This flow guide
is created by cutting a slot in a plate fin 131 to partially
circumscribe a peninsula portion. The peninsula portion remains
connected to the plate fin 131 by a tab portion 133. The peninsula
portion is then bent along the tab such that it protrudes at an
angle from the plate fin 131. This method not only forms an
integral flow guide 132, but also leaves an orifice to facilitate
fluid communication.
[0057] Accordingly, the method results in a flow guide that is
integral to the plate fin and that is disposed along the periphery
of an aperture. The apertures in each of the plate fins 131 are
formed from the displacement of the flow guides from the surface of
the plate fin 131. Each of the apertures has a volume substantially
similar to the flow guide. Accordingly, this configuration not only
forms an integral flow guide 132, but also leaves an aperture 139
to facilitate fluid communication.
[0058] FIGS. 13b and 13c illustrates flow guides made in a similar
fashion wherein sections were bent from plate fin 134 to leave
triangular orifices 136 above and below the flow guides
respectively. FIG. 13d shows flow guides that are also bent from a
plate fin, but in this case, form a curved flow guide 137 leaving
an orifice 138 in the plate fin.
[0059] FIGS. 14a through 14c show a typical narrow channel heat
exchanger 142 having a flow guide 141 mounted to the top thereon.
As shown in FIG. 14b, it is preferred that this particular flow
guide extend at an angle relative to the front plane of the fin
field.
[0060] FIGS. 15a through 15c again show a narrow channel heat
exchanger 151 having, in this case, a modified flow guide 152. It
has a similar configuration to that shown in FIG. 14, however, on
the exit end of the heat exchanger 151, there is an additional flow
guide 152. In this case, the flow guide 152 extends at an obtuse
angle 153 relative to the rear plane portion of the heat exchanger
151.
[0061] FIG. 16a shows a heat exchanger with a series of plate fins
161 each having a plurality of textured portions 162. The plate
fins are joined together by support elements 163. FIG. 16b shows a
discrete plate fin component of this configuration. As shown in
FIG. 16b, an example of an interior fin comprises several textured
regions extending outward from the surface of the fin and into an
adjacent channel. The textured regions illustrated herein are
elliptical in shape. However, the drawing figures are merely
illustrative, and the size, shape, dimensions and disbursement of
the textured regions about each fin may be modified accordingly. By
texturing the plate fin, fluid passing along the fin is disturbed
which thereby disrupts the boundary layer. As mentioned above, the
boundary layer blankets and otherwise insulates the plate fin from
the cooling fluid. Accordingly, the placement of the textured
regions about the individual plate fins causes a pressure drop in
the fin field thereby enhancing the aerodynamic characteristics of
the fluid flow about the heat dissipating device.
[0062] FIG. 17a shows a heat exchanger similar to that illustrated
in FIG. 16, however, the plate fins in this embodiment have a novel
communication feature, in this case louvers 176 and slots 172. The
various plate fins are joined together by support elements 175.
FIG. 17b shows a discrete exterior plate fin 171 having a slot 172,
and FIG. 17c shows a discrete interior plate fin having louvered
sections 176 and textured regions 174. The exterior plate fins 171
differ from the interior plate fins 173 in that they have no
textured surface, nor do they have louvered sections 176 protruding
therefrom. This is done for both aesthetics and structural reasons.
The textured portions may be considered unsightly and louvers on
the side plate fins may pose a risk of snagging. The benefit of
this configuration is having a plate fin surface that not only
disrupts the boundary layer, but also facilitates fluid
communication as described above.
[0063] FIG. 18a is similar to that of FIG. 17a, however, the
exterior plate fin 181 is similar to the interior plate fin. That
is, both the interior plate fins and the exterior plate fins have
textured regions 183 and louvered sections 182. In addition, the
heat exchanger has several bars 185 which transverse the plate
fins. Accordingly, the alignment of the textured regions 183 and
louvered regions 182 provides for fluid flow without impediments
between the interior and exterior fins.
[0064] FIGS. 19a and 19b illustrate a heat exchanger incorporating
a plate fin 191 similar to that illustrated in FIG. 13a. The plate
fin 191 comprises perforations having rectangular shaped openings
192 with 90 degree louvered sections 193. FIG. 19a is a perspective
view of a heat exchanger 190 comprised of individual plate fins
191, where both the interior and exterior fins comprise the
structure as illustrated in FIG. 19b. The fins 191 of the heat
exchanger are joined together by support elements 195. Accordingly,
the alignment of the plate fins 191 with the openings 192 causes
the fluid passing along the fin to be disturbed, thereby disrupting
the boundary layer and providing access to the cooling fluid.
[0065] FIG. 20a shows a heat exchanger having plate fins of varying
cross-sectional area relative to the fluid flow, and FIG. 20b shows
a discrete plate fin having the taper and connection elements 204.
In regard to the taper, plate fin 201 decreases in cross-sectional
area from the intake region 202 to the exhaust region 203. Each
plate fin 201 comprises connection elements 206 extending from the
top surface of each plate fin 201. As the plate fins 201 are
assembled, the connection elements 206 form transverse bars 207 as
illustrated in FIG. 20a. Accordingly, the taper reduces the
friction on the fluid moving through the fin field thereby
decreasing stagnation problems.
[0066] FIG. 21a shows a variation of the plate fin shape wherein a
curved notch is removed from the plate fin 211. FIG. 21b depicts a
discrete plate fin 211 having a curved profile 212. The curved
profile correlates to frictions exponential relationship to
velocity. The function behind this particular design is to reduce
the drag on fluid entering from the intake region 213, while
increasing the friction on fluid entering from the exhaust region
214. Each fin comprises connection elements 216 extending from the
top surface of each plate fin 211. As the plate fins 211 are
assembled, the connection elements 216 align to form transverse
bars 217, as illustrated in FIG. 21a. The transverse bars 217 add
structural integrity to the assembled heat exchanger, as well as
act as a flow control feature. More specifically, the transverse
bars 217 act as flow guides for imparting a downward force on the
fluid attempting to exit through the top region of the heat
exchanger. Accordingly, this configuration reduces the flow of
fluid in through the exhaust region.
[0067] FIG. 22a shows a heat exchanger having plate fins of varying
length. The fins range from a long length 222 to a short length of
223 to form a clear region 224. This region has very little
frictional effect on the fluid therefore reducing the formation of
stagnant regions within the fin field. It should be clear to those
skilled in the art that a variety of configurations are possible to
create a clear region 224. It should also be obvious that the plate
fins used in this configuration can incorporate any combination of
the flow control elements discussed herein. Suitable configurations
include a flat plate fin 225 as shown in FIG. 22b, a slotted plate
fin 226 as shown in FIG. 22c, and a perforated plate fin 227 as
shown in FIG. 22d.
[0068] FIGS. 23a through 23c show a narrow channel heat exchanger
231 having a plate fin 233 with a section removed from it. As FIG.
23c shows, the removal results in a vacant area 232 which reduces
the drag or friction on fluid moving through the channels. This
results in reduced fluid stagnation and the problems associated
therewith.
[0069] FIGS. 24a through 24c are similar to that of FIG. 23,
however, rather than having an entire section removed from the
plate fin, a smaller section 243 is removed from the fin 242,
leaving a top portion 244 in tact. This configuration also provides
for reduced drag, but also provides greater surface area for heat
exchange. Furthermore, this area is located towards the top of the
het exchanger where stagnant fluid is generally not a problem.
[0070] FIGS. 25a through 25c show a narrow channel heat exchanger
251 similar to FIG. 24, however, this design also has a top plate
252 having a certain profile. The top plate 252 disturbs the fluid
bypassing the fin field 251 therefore slowing it down and creating
a higher pressure above the fin field. This higher pressure tends
to restrict egress of fluid from the fin field 251, and may even
facilitate fluid ingress.
[0071] FIG. 26a shows a heat exchanger having a plate fin made of
segments 261. Segments are spaced so that a gap 263 is formed
between them. In this particular embodiment, a top bar 262 is used
to join the two sections together as well as connect the various
plate fin components together. FIG. 26b shows a discrete plate fin
component having sections 261 and gaps 263, and FIG. 26c shows a
complementing plate fin arrangement having connection elements 264
extending from a top surface of the plate fin. As mentioned above,
when assembled in series, connection elements 264 form transverse
bars 262 that adds both integrity and improved heat conduction to
the heat exchanger. The benefit of this design is that it allows
for easy communication between the channels. Moreover, the
plurality of top bars restricts the egress of fluid from the
channels.
[0072] FIG. 27a shows a perspective view of a heat exchanger having
plate fins comprised of different components. FIG. 27b illustrates
one such discrete plate fin having connection elements 275
extending from the top surface of the fin. In this embodiment, the
plate fin has a high surface area component 271 along with low
surface area components 272. Securing the various low surface area
components together are transverse bars 273, and connecting the
various high surface area components together is another transverse
bar 274. As shown in FIG. 27a, transverse bars 273 and 274 extend
lengthwise across the heat exchanger, however bar 273 is
significantly wider than bar 274. Accordingly, the benefit of this
design is that it allows for easy fluid communication in the front
region of the heat exchanger where fluid stagnation has its
greatest impact, while providing high friction towards the rear of
the heat exchanger where the ingress of fluid from the bypass
contributes to stagnation.
[0073] FIG. 28a shows a similar configuration as that illustrated
in FIG. 27a, except rather than having the high surface area
components 282 in the rear of the exchanger, they are placed in the
middle section of the heat exchanger. Again, low surface area
components are used in and around these larger sections. The low
surface area components 281 are spaced so that a gap 283 is formed
between them. In this particular embodiment, transverse bars 286
and 287 are formed from connection elements 286a and 287a extending
from a top surface region of each plate fin 280. FIG. 28b
illustrates a discrete plate fin component 280 having sections 281
and 282 and gaps 283. When the individual plate fins 280 are
assembled in series connection, elements 286a and 287a form
transverse bars 286 and 287 that adds both structural integrity and
improved heat conduction to the heat exchanger. This design is
particularly well-suited for a fan which would be placed in and
around section 285. In this way, fluid is drawn in through low
frictional areas on either side of the heat exchanger and the
forced convection of the fan pulls it through the high surface area
fin components 282.
[0074] FIGS. 29a and 29b show an alternative type of fin field
wherein the fin is arched. In FIG. 29a the fins 291 are aligned,
while in FIG. 29b the fins 292 are staggered. The advantage of the
in-line configuration is the ease of fluid flow and low frictional
losses. The advantage of the staggered design is a more efficient
heat conduction since the fins 292 are exposed to "fresh" fluid
flow, not previously exposed to a fin.
[0075] FIGS. 29c and 29d show alternate embodiments of the curved
fin design. FIG. 29c shows a fin 293 having a base 294 integral to
it, while the fin in FIG. 29d is open at the bottom having tabs for
connection to a base element of a heat exchanger.
[0076] FIG. 30a shows yet another embodiment of an improved heat
exchanger 305 employing the flow control features of the present
invention. Here, the fin field consists of concentric arcuate
sections of fin. That is, there is an interior section 303, a
middle section 302, and an exterior section 301. These sections are
formed to define arcuate channels 304 between them. The enclosed
nature of this design prevents the egress of fluid prematurely.
FIGS. 30b, 30c and 30d illustrate the progression of assembly of
the semi-circular shaped fins. One of the benefits associated with
this fin configuration is the increased surface area being
provided. Additionally, the fins may be modified as suggested above
with both slots and orifices or textures. In this way, the low
pressure regions created by flow bypass draw the stagnant air out.
With such orifices or slots, the fin field actually becomes
omni-directional. Thus, instead of having fluid drawn out of the
fin field through the orifices, the main flow could be through the
orifices or slots and the stagnant fluid could be drawn out through
the channels 304.
[0077] FIG. 31 illustrates a narrow channel heat exchanger
comprising four different heat exchangers arranged in a square
thereby defining a heat tower 314 in the center. Each fin field
comprises fin plates 313 having a vertical orientation. The tops of
these plate fins are joined by flow guides 316. In this particular
embodiment, a fan mounting platform 317 is provided at the top of
the fin fields to receive a fan. The fan draws fluid 311 through
said fin plates 313. The flow guides 316 restrict the intake of
such fluid giving it a near perpendicular ingress orientation which
results in a near impingement situation.
[0078] FIG. 32 shows another heat exchanger 320 configuration
adapted to receive a fan. The heat exchanger 320 is a low profile
narrow channel heat exchanger using a blower to move the fluid. In
this embodiment, plate fins 321 are arranged on a base, and flow
guides 324 in the form of transverse bars extend the width of the
heat exchanger 320 across the top of the plate fins. The heat sink
320 comprises mounting plates 325 extending at a 90 degree angle
from the body of the heat exchanger 320 at a front end. The
mounting plates 325 are intended to secure the heat exchanger 320
adjacent to a fan or blower (not shown). This configuration allows
the restricted intake of fluid through the top end of said fin
field. As fluid is drawn into the fin field, either through the top
region, as illustrated at 322, or the back region 323, the fluid is
drawn out through the fan at the front end, as illustrated at
326.
[0079] The restricted access provided by the flow guides in this
configuration thereby creates a near impingement condition.
Accordingly, this heat exchanger 320 is intended for electronic
applications with height constraints.
[0080] FIG. 33 shows a heat exchanger 330 very similar to FIG. 32,
except it has a buffer 333 for accommodating larger size fans in
comparison to the heat exchanger 320 illustrated in FIG. 32. The
buffer 333 lies between the fan (not shown) and the fin field, and
provides for an equalization of the pressure. The buffer 333 allows
for the accommodation of more than one fan depending upon the size
of the unit. In addition, if the fan is placed too close to an
obstruction, the performance of the heat exchanger 330 will be
significantly depleted. The purpose of the fan is to make the fluid
flow entering the fin field uniform. If the flow is not uniform,
this will result in a temperature gradient across the heat
exchanger 330. Similar to the heat exchanger illustrated in FIG.
32, the heat exchanger 330 comprises flow guides 332 in the form of
transverse bars extending across the width of the heat exchanger
330. The flow guides 332 provide support for the fins as well as
provide the ability for the heat exchanger 330 to receive evenly
distributed fluid flow. As such, the flow guides 332 guide fresh
fluid being drawn into the fin field, as shown at 336, to different
parts of the heat exchanger 330. One of the benefits associated
with the heat exchanger 330 is the ability to accommodate a large
fan or multiple fans, at 334, depending upon the size and
dimensions of the unit. Accordingly, the fan provides a source of
power for moving fluid at a higher velocity within the fin field
and through the heat exchanger by directing fluid flow to exit the
front end at 335.
[0081] Manufacturing Process
[0082] Creating plate fin configurations of the type described
above can be difficult if not impossible using traditional
techniques of extrusion, machining, and casting. For this reason,
the present invention provides for discrete plate fins that can be
individually configured for a particular application before being
mounted to a base. FIG. 34 shows an assembly process for the heat
exchanger disclosed. First, a properly sized plate fin 341 is cut
or otherwise obtained from stock material of aluminum, copper, or
any other high temperature conducting material. Next, the plate fin
is modified with surface enhancements. As discussed above, these
surface enhancements include orifices 342, slots 343, texturing,
and flow guides. Support plates 344 may be also attached to the top
and bottom of the plate fin for securing the plate fin to both the
base and the other plate fins. Next, the plate fins are assembled
on a base 345. They may be attached using traditional securing
elements of gluing, soldering, braising, pressing and heating, or
other bonding techniques as well as mechanical connecting
techniques such as tongue and groove, tab and slot, hole and dowel
and other known apparatus, to form the final assembly 346.
Alternatively, the discrete fins may be connected to form an
assembly before mounting to the base.
[0083] Certain heat exchanger configurations of the present
invention may also be manufactured as integral assemblies. To this
end, a block of thermally conductive material is machined to define
plate fins and channels. This block is then drilled or otherwise
machined across the plate fins to produce orifices therethrough. In
this way, a heat exchanger is manufactured that has integral plate
fins which may be preferable from a manufacturing and structural
integrity perspective.
[0084] The above description is of a novel apparatus and method for
a heat exchanger having fluid control elements for providing
enhanced cooling of heat producing electronic components. Although
the present invention has been described in connection with
preferred embodiments thereof, it will be appreciated by those
skilled in the art that additions, deletions, modifications, and
substitutions not specifically described may be made without
departing from the spirit and scope of the invention as defined in
the appended claims and the scope should not be limited to the
dimensions indicated herein above.
* * * * *