U.S. patent application number 13/596020 was filed with the patent office on 2013-03-07 for heat exchanger with controlled coefficient of thermal expansion.
This patent application is currently assigned to MIKROS MANUFACTURING, INC.. The applicant listed for this patent is Javier A. Valenzuela. Invention is credited to Javier A. Valenzuela.
Application Number | 20130056176 13/596020 |
Document ID | / |
Family ID | 47752222 |
Filed Date | 2013-03-07 |
United States Patent
Application |
20130056176 |
Kind Code |
A1 |
Valenzuela; Javier A. |
March 7, 2013 |
Heat Exchanger with Controlled Coefficient of Thermal Expansion
Abstract
The heat exchanger with a controlled coefficient of thermal
expansion (CTE) includes a low CTE thermal expansion control member
operatively connected to a heat transfer member in order to
restrain the lateral thermal expansion of the heat transfer member
during use. The thermal expansion control member is placed outside
the heat transfer path, so the thermal expansion control member can
be made of a low thermal conductivity material without increasing
the thermal resistance of the heat exchanger. The CTE of the
thermal expansion control member is lower than that of the heat
transfer member, so as to constrain lateral thermal expansion of
the heat transfer member during operation. The difference between
the CTE of the device being cooled and the heat transfer member,
i.e. the CTE mismatch, is reduced over conventional heat exchangers
by restraining the heat transfer member during operation.
Inventors: |
Valenzuela; Javier A.;
(Portsmouth, RI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Valenzuela; Javier A. |
Portsmouth |
RI |
US |
|
|
Assignee: |
MIKROS MANUFACTURING, INC.
Claremont
NH
|
Family ID: |
47752222 |
Appl. No.: |
13/596020 |
Filed: |
August 27, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61528073 |
Aug 26, 2011 |
|
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|
Current U.S.
Class: |
165/81 |
Current CPC
Class: |
F28F 2260/02 20130101;
F28F 21/087 20130101; F28D 2021/0029 20130101; F28F 3/12 20130101;
F28F 21/00 20130101; F28F 2265/26 20130101; F28F 21/067 20130101;
F28F 3/10 20130101; F28F 21/085 20130101; F28F 9/026 20130101 |
Class at
Publication: |
165/81 |
International
Class: |
F28F 21/00 20060101
F28F021/00; F28F 7/00 20060101 F28F007/00 |
Claims
1. A heat exchanger for cooling a heat producing device, the heat
exchanger comprising: a heat transfer member having a first surface
operatively connected to the heat producing device, a second
surface opposite the first surface, at least the first surface of
the heat transfer member having a coefficient of thermal expansion
larger than the coefficient of thermal expansion of the heat
producing device; a thermal expansion control member operatively
connected to the second surface of the heat transfer member such
that the thermal expansion control member is outside of a heat
transfer path disposed between the heat transfer member and the
heat producing device, the thermal expansion control member having
a coefficient of thermal expansion sufficiently lower than that of
the heat transfer member so as to constrain lateral thermal
expansion of the heat transfer member during use; and wherein
during operation of the heat producing device, the thermal
expansion control member constrains the lateral thermal expansion
of the heat transfer member so that the heat transfer member
expands a similar amount as the expansion of the heat producing
device, allowing a rigid connection between the heat producing
device and the heat transfer member without inducing excessive
thermal stresses in the heat producing device or at the interface
between the heat producing device and the heat transfer member.
2. The heat exchanger according to claim 1, wherein the coefficient
of thermal expansion for the heat producing device is in the range
of about 3-6 ppm.
3. The heat exchanger according to claim 2, wherein the coefficient
of thermal expansion for the heat transfer member is above about 15
ppm.
4. The heat exchanger according to claim 1, wherein the thermal
expansion control member includes a restraining plate.
5. The heat exchanger according to claim 4, wherein the thermal
expansion control member further includes a manifold, the manifold
being constructed and arranged to distribute and collect fluid over
a heat transfer surface of the heat transfer member.
6. The heat exchanger according to claim 5, further comprising a
bow compensation member.
7. The heat exchanger according to claim 6, wherein the bow
compensation member is disposed adjacent the manifold on a side
opposite that of the restraining plate.
8. The heat exchanger according to claim 4, further including a
compliant manifold constructed and arranged to distribute and
collect fluid over a heat transfer surface of the heat transfer
member and a bow compensation member disposed between the compliant
manifold and the thermal expansion control member.
9. The heat exchanger according to claim 4, further including a
rigid manifold constructed and arranged to distribute and collect
fluid over a heat transfer surface of the heat transfer member, a
compliant gasket disposed between the rigid manifold and the
thermal expansion control member, and further including a bow
compensation member disposed between the compliant gasket and the
thermal expansion control member.
10. The heat exchanger according to claim 5, wherein the thermal
expansion control member further includes a second restraining
plate and wherein the manifold is disposed between the restraining
plate and the second restraining plate.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority to U.S.
Provisional Patent Application No. 61/528,073, filed Aug. 26, 2011
and entitled "Heat Exchanger with Controlled Coefficient of Thermal
Expansion", the entire contents of the application being
incorporated herein by reference in its entirety.
TECHNICAL FIELD
[0002] This invention relates generally to an apparatus for cooling
a heat producing device, whose coefficient of thermal expansion is
substantially lower than that of metals. More specifically, this
invention relates to a heat exchanger whose coefficient of thermal
expansion can be constrained to be similar to that of the device
being cooled.
BACKGROUND
[0003] The use of heat exchangers for cooling a range of heat
producing devices is known in the art. Heat exchangers are used to
transfer heat from the heat-producing device to a coolant, either a
liquid, or a gas. Liquid cooled heat exchangers have flow passages
disposed in a heat transfer member to distribute the coolant over
the area to be cooled. The passages can range from simple tubes to
micro-channels, depending on required heat transfer capacity of the
heat exchanger.
[0004] A typical application of liquid cooled heat exchangers is in
the cooling of power electronic components, such as IGBTs and power
FETs. FIG. 1 is a schematic of a conventional prior art approach to
liquid cooling of an electronic component, namely die 11. As shown,
die 11 is soldered ("s1") to a direct bonded copper (DBC) substrate
13. The DBC 13 includes a ceramic layer 13a with a layer of copper
13b, 13c bonded to either side. Copper layer 13b includes a pattern
etched thereon to form the electrical connection to the die while
the other copper layer 13c is soldered ("s2") to a heat spreader
15. The heat spreader 15 distributes the heat over an area
approximately 5 to 8 times larger than the die 11, and is
mechanically attached to an external heat exchanger 17. Care is
taken to minimize the gap between heat spreader 15 and heat
exchanger 17 in order to minimize the interface thermal resistance.
Thermal grease 19 is often placed between the heat spreader 15 and
the heat exchanger 17 to further reduce the thermal resistance of
the interface.
[0005] Many heat exchangers and heat spreaders are made of copper
or aluminum, and for such heat exchangers the coefficient of
thermal expansion (CTE) is generally above about 17 ppm/.degree. C.
which is substantially higher than that of the die. For example,
copper has a CTE of 17 ppm/.degree. C. and Aluminum has a CTE of 24
ppm/.degree. C.; whereas the electronic devices being cooled (for
example IGBT's, solar cells, and the like) have a CTE in the range
of about 3-6 ppm/.degree. C. (for example silicon 3.2 ppm/.degree.
C., germanium 5.8 ppm/.degree. C.). Thus, the device being cooled
and the heat exchanger have substantially different coefficients of
thermal expansion (CTE), i.e. a CTE mismatch, which results in
undesirable thermal stress.
[0006] In order to address the issue of CTE mismatch, prior art
applications utilize a copper-ceramic-copper (direct bonded copper
or DBC) substrate to attach the device being cooled to the
substrate. Typically the DBC substrate will have a CTE between 5-8
ppm/.degree. C., an intermediary value between the device being
cooled and the substrate. The DBC is also used to provide
electrical isolation. Prior art devices further utilize a layer of
solder to add compliance in order to accommodate the CTE mismatch.
Providing the DBC and solder helps to accommodate the CTE mismatch,
with the DBC reducing the overall range of the mismatch and the
solder providing compliance, but there remains a mismatch and the
DBC and solder layers add significant thermal resistance. In
addition, while the solder can plastically deform repeatedly
without cracking during use, the solder will eventually fatigue and
fail, the amount of time to failure being dependent upon the
operating conditions. For operating conditions with high
temperature excursions fewer cycles will cause failure of the
solder joint, while lower temperature excursions will allow for
more operating cycles. As will be appreciated, the solder is chosen
primarily for its mechanical properties, and indium based solder is
commonly utilized because it deforms easily.
[0007] The trend in electronics packaging toward smaller, more
powerful components results in the need for the heat exchangers to
operate at ever increasing heat fluxes. The prior art cooling
device illustrated in FIG. 1 is normally used with devices that
dissipate no more than about 100 W/cm.sup.2. For cooling higher
heat flux devices, such as high-power electronic devices
dissipating about 300 W/cm.sup.2, or solid-state laser diodes,
which dissipate heat at a rate of about 500-1000 W/cm.sup.2, heat
exchangers integrated into the device package are generally
employed. In the integrated heat exchangers, the heat spreader also
functions as the heat exchanger heat transfer member, and has flow
passages or fins to transfer heat to the coolant. By integrating
the heat exchanger into the package, the interface resistance of
the mechanical attachment between the heat spreader and the heat
exchanger is eliminated. In order to handle these large heat fluxes
without exceeding the maximum operating temperature of the
electronic component, it is desirable for the heat transfer member
to be constructed out of a high thermal conductivity material such
as copper or aluminum.
[0008] Other prior art applications that use integrated heat
exchangers reduce the CTE mismatch by utilizing material for the
heat exchanger other than copper or aluminum. For example, low CTE
refractory metals, such as molybdenum (CTE=7 ppm/.degree. C.) or
tungsten (CTE=6 ppm/.degree. C.), or metal-ceramic composites, such
as aluminum silicon carbide (AlSiC; CTE=8-15 ppm/.degree. C.) have
been utilized in place of copper. The use of these materials reduce
the CTE mismatch, but at the expense of increased thermal
resistance and cost. The thermal conductivity of these materials is
in the range of about 140-200 W/m-K which is significantly lower
than copper at about 400 W/m-K. The price of refractory metals is
several times that of copper.
[0009] In practice, most prior art cooling devices only allow for
the device being cooled to operate at about half the maximum rated
current. This is because while the device to be cooled may have the
capability to run at a certain maximum current, prior art heat
exchangers lack the ability to adequately remove heat, resulting in
overheating of the device if run near its maximum current
capability.
SUMMARY
[0010] In order to increase the power handling capacity of the heat
exchanger and improve operating performance, the thermal resistance
should be reduced while also lowering thermal stress that can lead
to failure of the joint between the device being cooled and the
heat exchanger. This is achieved in the present application by
restraining the thermal expansion of the heat transfer member to
reduce thermal stress and by removing the restraining member from
the heat transfer path to reduce thermal resistance. The difference
between the CTE of the device being cooled and the heat transfer
member, i.e. the CTE mismatch, is reduced over the prior art by
restraining the heat transfer member during operation, thus
effectively reducing the coefficient of thermal expansion of the
heat exchanger.
[0011] The heat exchanger includes a thermal expansion control
member operatively connected to a surface of the heat transfer
member to restrain the thermal expansion of the heat transfer
member during use. The thermal expansion control member is placed
outside the heat transfer path, so the thermal expansion control
member can be made of a low thermal conductivity material without
compromising thermal performance of the heat exchanger. The CTE of
the thermal expansion control member is lower than that of the heat
transfer member, so as to constrain lateral thermal expansion of
the heat transfer member during operation.
[0012] In one embodiment, the manifold is part of the thermal
expansion control member. As such, the manifold is also made of the
low CTE material and is generally rigid.
[0013] In one embodiment, a bow compensation member is provided to
balance thermal stresses on the heat exchanger and reduce heat
exchanger bow that can result from the difference in CTE between
the thermal expansion control member and the heat transfer member.
The bow compensation plate may be made of the same material as the
heat transfer member and mounted to the opposite side of the
thermal expansion control member in order to reduce any bowing that
may occur during operation by balancing the thermal stresses.
[0014] In another embodiment, the heat exchanger includes a
symmetrical construction with heat transfer members making up both
the top and bottom faces of the heat exchanger. In this embodiment,
the thermal expansion control member is disposed in between the two
heat transfer members. Heat transfer is symmetric and bowing in the
heat exchanger is controlled by the symmetry of the heat transfer
members, and a separate bow compensation member is, therefore, not
required.
[0015] In yet another embodiment, the manifold is formed as a
separate member from the thermal expansion control member. In this
embodiment the manifold may also be made of a compliant material to
accommodate the different thermal expansion between the manifold
and the portion of the heat exchanger that has the controlled CTE.
In this embodiment, because the thermal expansion control member
does not include the manifold, it is generally thinner than other
embodiments. With a thinner thermal expansion control member, the
need for a bow compensation member becomes more important as bowing
from temperature gradients in the heat exchanger is more
pronounced.
[0016] In all the embodiments, a thermal expansion control member
that is outside of the heat transfer path is provided to reduce
thermal stresses without adding thermal resistance. Because thermal
stresses are reduced, the thickness of the solder can also be
reduced, and a less ductile but higher thermal conductivity solder
can be utilized.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The foregoing and other objects, features and advantages
will be apparent from the following description of particular
embodiments of the invention, as illustrated in the accompanying
drawings in which like reference characters refer to the same parts
throughout the different views. The drawings are not necessarily to
scale, emphasis instead being placed upon illustrating the
principles of various embodiments of the invention.
[0018] FIG. 1 is a schematic of a conventional prior art liquid
cooled heat exchanger for cooling an electronic component;
[0019] FIG. 2 is a schematic, perspective view of a first
embodiment of a heat exchanger having a controlled coefficient of
thermal expansion in combination with a device to be cooled
according to the present description;
[0020] FIG. 3 is a schematic, perspective view of the first
embodiment of the heat exchanger of FIG. 2 without the device to be
cooled;
[0021] FIG. 4 is an exploded view of the heat exchanger of FIG.
3;
[0022] FIG. 5 is a schematic, perspective view of a second
embodiment of a heat exchanger having a controlled coefficient of
thermal expansion including a bow compensation member;
[0023] FIG. 6 is an exploded view of the heat exchanger of FIG.
5;
[0024] FIG. 7 is a schematic, perspective view of a third
embodiment of a heat exchanger having a controlled coefficient of
thermal expansion and a symmetrical construction;
[0025] FIG. 8 is an exploded view of the heat exchanger of FIG.
7;
[0026] FIG. 9 is a schematic, perspective view of a fourth
embodiment of a heat exchanger having a controlled coefficient of
thermal expansion and a compliant manifold;
[0027] FIG. 10 is an exploded view of the heat exchanger of FIG.
9;
[0028] FIG. 11 is a schematic, perspective view of a fifth
embodiment of a heat exchanger having a controlled coefficient of
thermal expansion including a compliant gasket and a rigid
manifold; and
[0029] FIG. 12 is an exploded view of the heat exchanger of FIG.
11.
DETAILED DESCRIPTION
[0030] Referring initially to FIGS. 2-4, a first embodiment of a
heat exchanger 10 having a controlled coefficient of thermal
expansion (CTE) is illustrated. In the present description, the
coefficient of thermal expansion is used in the conventional manner
to mean the fractional increase in the length per unit rise in
temperature of a material. The heat exchanger 10 has a thermal
expansion control member 12 including a restraining plate 14 and
manifold 16 in the present embodiment, and also includes a heat
transfer member 18 for transferring heat to a coolant, and a cover
plate 20, as illustrated. As shown in FIG. 2, a device to be
cooled, such as die 11 can be mounted to a DBC substrate 13 and to
the cover plate 20. In use, heat is transferred to, and/or from the
heat exchanger 10 over the portion of the heat transfer member 18
that includes channels 22, as described in more detail below. The
function of distributing and collecting the fluid to the channels
22 is achieved by the manifold 16 while the function of
transferring the heat is achieved by the heat transfer member 18.
Manifold 16 is not disposed in the path between the device to be
cooled 11 and the heat transfer member 18 (the heat transfer path)
and, therefore, it is not in the heat transfer path. In the present
embodiment, the manifold 16 is part of the thermal expansion
control member 12, including restraining plate 14, which is also
not in the heat transfer path. By placing the thermal expansion
control member including manifold 16 and restraining plate 14
outside of the heat transfer path, thermal stresses can be reduced
without adding thermal resistance.
[0031] The function of the manifold 16 is to distribute and collect
the fluid over a heat transfer surface of the heat transfer member
18. In the present embodiment, the manifold 16 may have an
interdigitated design to promote uniform heat transfer capacity
over the heat transfer surface, as is known in the art. The
manifold 16 includes an inlet port 26 through which fluid enters
the manifold and an outlet port 28 through which fluid exits the
manifold. Other designs for the manifold may be utilized as would
be known to those of skill in the art, provided, that the manifold
is made of a low CTE material in the present exemplary
embodiment.
[0032] Because the thermal expansion control member 12 is not in
the heat transfer path, it can be made of a low thermal
conductivity material, for example low CTE nickel alloys such as
Invar.RTM. (generically 64FeNi, extra pure grades having CTE as low
as 0.62-0.65 ppm/.degree. C.), Kovar.RTM. (a nickel-cobalt ferrous
alloy designed to be compatible with the thermal expansion
characteristics of borosilicate glass, CTE of about 5.9
ppm/.degree. C.) and Alloy 42 (FeNi42, CTE of 5.3 ppm/.degree. C.,
which matches Germanium), or any other material with a low CTE. As
described herein a material with a low CTE is below about 8
ppm/.degree. C. In the present embodiment, the thermal expansion
control member 12 includes both restraining plate 14 and manifold
16, which are made of the same low CTE material, but the two may be
made from different low CTE materials, if desired.
[0033] In contrast, the heat transfer member 18 is made of a high
thermal conductivity material, for example copper (CTE 16.7
ppm/.degree. C.) in order to transfer heat from the device to be
cooled with a low thermal resistance. In the present embodiment,
heat transfer member 18 includes one or more layers 24, each having
a plurality of non-linear, winding micro or mini-channels 22 formed
therein as described in pending U.S. patent application Ser. Nos.
12/188,859 and 13/115,956, which are incorporated by reference
herein in their entirety. Other channel configurations may be
utilized, for example linear channels, channels having different
geometries, and/or different dimensions, including those that are
not micro-channels, as would be known to those of skill in the
art.
[0034] Heat transfer member 18 is secured to the thermal expansion
control member 12 in a known manner, for example by bonding. In the
present embodiment, the thickness of the heat transfer member 18
"T.sub.h" is very thin, approximately 1 mm, and includes a
plurality of channels 22 which form voids in the heat transfer
member. In contrast, the thickness of the thermal expansion control
member 12, i.e. the combination of restraining plate 14 and
manifold 16 "T.sub.m", is in the range of approximately 5-10 mm in
the present embodiment. The restraining plate 14 is also largely
solid. The resulting stiffness of the thermal expansion control
member 12 is greater as compared to the stiffness of the heat
transfer member 18, which helps constrain lateral expansion of the
heat transfer member 18 during use. As a result the CTE of the heat
exchanger can be made closer to that of the thermal expansion
control member 12 than to that of the heat transfer member 18. The
proportions and the stiffness of the heat transfer member 18 and
the thermal expansion control member 12 can be varied to get an
acceptable CTE for a particular application. Having a lower CTE
mismatch reduces thermal stress and can prolong the life of the
device incorporating the heat exchanger. Reduced thermal stress
also allows for a thinner layer of solder, as compliance from the
solder becomes less important the lower the CTE mismatch. As such,
the solder can be chosen for its thermal conductivity properties
instead of its mechanical properties.
[0035] Referring now to FIGS. 5-6, a second embodiment of a heat
exchanger having a controlled CTE is illustrated. In this
embodiment, the same or similar elements as the previous embodiment
is labeled with the same reference numbers, preceded with the
numeral "1". Heat exchanger 110 also includes a thermal expansion
control member 112 having a restraining plate 114 and manifold 116,
and further includes a heat transfer member 118, a cover plate 120,
and a bow compensation member 130. The bow compensation member 130
helps balance the thermal stresses on the heat exchanger 110 which
can result in thermal distortion, i.e. bowing of the heat
exchanger. The bow compensation member 130 may be made of the same
material as the heat transfer member 118, and is secured to the
opposite side of the thermal expansion control member 112 in order
to reduce any bowing that may occur during operation by balancing
the thermal stresses. Alternatively, the bow compensation member
130 may be made of a different material than the heat transfer
member 118, depending upon whether more or less compensation may be
required to help alleviate bowing. In either case, the bow
compensation member 130 will have a CTE that is higher than that of
the thermal expansion control member 112.
[0036] Referring now to FIGS. 7-8, a third embodiment of a heat
exchanger having a controlled CTE is illustrated. In this
embodiment, the same or similar elements as the previous
embodiments are labeled with the same reference numbers, preceded
with the numeral "2". Heat exchanger 210 also includes a thermal
expansion control member 212, a heat transfer member 218, a cover
plate 220, and further includes a symmetrical construction
including a second heat transfer member 218b. In this embodiment,
the thermal expansion control member 212 is disposed in between the
two heat transfer members 218 and 218b and includes a second low
CTE restraining plate 214b in addition to the first low CTE
restraining plate 214 and manifold 216. By providing a heat
transfer member 218, 218b secured on either side of the thermal
expansion control member 212, which includes two low CTE
restraining plates 214, 214b, the thermal stresses are symmetric
and bowing in heat exchanger 210 is controlled. The symmetry of
this embodiment and the provision of a single manifold 216 for two
heat transfer members 218, 218b provides a compact configuration
that is symmetrical in both material and temperature
distribution.
[0037] Referring now to FIGS. 9-10, a fourth embodiment of a heat
exchanger having a controlled CTE is illustrated. In this
embodiment, the same or similar elements as the previous
embodiments are labeled with the same reference numbers, preceded
with the numeral "3". Heat exchanger 310 also includes a thermal
expansion control member 312 which in the present embodiment is a
low CTE restraining plate 314. The heat exchanger 310 further
includes a bow compensation member 330, a heat transfer member 318,
a cover plate 320, and a compliant manifold 337. As with the
previous embodiments, the manifold 337 distributes and collects the
fluid over a heat transfer surface of the heat transfer member 318.
However, the manifold 337 is not part of the thermal expansion
control member 312, and does not operate to constrain the heat
transfer member 318 in the present embodiment. As with the previous
embodiments, the manifold 337 is also is not in the heat transfer
path. Thus, manifold 337 is only responsible for flow distribution,
not mechanical constraint or heat dissipation in the present
embodiment. Because the manifold is not made of a low CTE expansion
material, and the thermal expansion control member 312 only
includes restraining plate 314, a bow compensation member 330 is
also provided in the present embodiment in order to reduce any
bowing that may occur during operation by balancing the thermal
stresses. As illustrated in FIGS. 9 and 10, the bow compensation
member 330 may be disposed between the compliant manifold 337 and
the thermal expansion control member 312, i.e. CTE restraining
plate 314 in the present embodiment.
[0038] The manifold 337 is compliant, i.e. not rigid, such that the
manifold can stretch during use to accommodate the differential
thermal expansion between the manifold and the controlled CTE
portion while continuing to distribute and collect fluid over the
heat transfer surface. In order to provide flexibility to the
manifold 337, the manifold may be made from a polymeric or
elastomeric material (for example a rubber, silicone, urethane,
etc) or another type of compliant material as would be known to
those of skill in the art. Referring now to FIGS. 11-12, a fourth
embodiment of a heat exchanger having a controlled CTE is
illustrated. In this embodiment, the same or similar elements as
the previous embodiments are labeled with the same reference
numbers, preceded with the numeral "4". Heat exchanger 410 also
includes a thermal expansion control member 412 which in the
present embodiment is a low CTE restraining plate 414. The heat
exchanger 410 further includes a bow compensation member 430, a
heat transfer member 418, a cover plate 420, and a compliant gasket
438 disposed between the bow compensation member 430 and a rigid
manifold 440. This embodiment is essentially the same as the
embodiment of FIGS. 9-10, except the compliant manifold has been
replaced with a compliant gasket 438 supported by a rigid manifold
440. The compliant gasket 438 operates to accommodate the
differential thermal expansion between the manifold and the
controlled CTE portion of the heat exchanger while the rigid
manifold 440 operates to distribute and collect fluid over the heat
transfer surface, in the present embodiment. As illustrated in
FIGS. 11 and 12, the bow compensation member 430 may be disposed
between the compliant gasket 438 and the thermal expansion control
member 412, i.e. CTE restraining plate 414 in the present
embodiment.
[0039] In all of the exemplary embodiments described herein, the
thermal expansion control member is operatively connected to a
surface of the heat transfer member to restrain the thermal
expansion of the heat transfer member during use. The thermal
expansion control member is placed outside the heat transfer path,
so the thermal expansion control member can be made of a low
thermal conductivity material without compromising the thermal
performance of the heat exchanger. The CTE of the thermal expansion
control member is lower than that of the heat transfer member, so
as to constrain lateral thermal expansion of the heat transfer
member during operation. The difference between the CTE of the
device being cooled and the heat transfer member, i.e. the CTE
mismatch, is reduced over the prior art by restraining the heat
transfer member during operation, thus effectively reducing the
coefficient of thermal expansion of the heat exchanger.
[0040] While various embodiments of the invention have been
particularly shown and described, it will be understood by those
skilled in the art that various changes in form and details may be
made therein without departing from the spirit and scope of the
invention as defined by the appended claims.
[0041] For example, the dimensions, geometric shapes, and materials
disclosed herein may be varied, as would be known to those of skill
in the art. More specifically, the stiffness of the heat transfer
member relative to that of the thermal expansion control member can
be varied depending upon the application. Likewise, the material
utilized for the thermal expansion control member and/or the heat
transfer member may also be varied, depending upon the application.
The heat transfer member and manifold may take any of a variety of
forms, as would also be known to those of skill in the art. In
addition, the heat exchanger while illustrated as parallel flow
could also be configured as a normal flow heat exchanger.
Therefore, the above description should not be construed as
limiting, but merely as exemplifications of preferred embodiments.
Those skilled in the art will envision other modifications within
the scope, spirit and intent of the invention.
* * * * *