U.S. patent application number 12/124092 was filed with the patent office on 2009-11-26 for mixed carbon foam/metallic heat exchanger.
This patent application is currently assigned to The Boeing Company.. Invention is credited to David E. Blanding, Jarrett Reed Datcher, Samuel Kim, Michael F. Stoia.
Application Number | 20090288814 12/124092 |
Document ID | / |
Family ID | 40954750 |
Filed Date | 2009-11-26 |
United States Patent
Application |
20090288814 |
Kind Code |
A1 |
Stoia; Michael F. ; et
al. |
November 26, 2009 |
Mixed Carbon Foam/Metallic Heat Exchanger
Abstract
A heat exchanger includes a thermally-conductive fluid barrier
having first and second surfaces, at least one first type of foam
element placed in thermally-conductive contact with the first
surface of the thermally-conductive fluid barrier and having a
first coefficient of thermal expansion and at least one second type
of foam element placed in thermally-conductive contact with the
second surface of the thermally-conductive fluid barrier and having
a second coefficient of thermal expansion. The first coefficient of
thermal expansion of the first type of foam element and the second
coefficient of thermal expansion of the second type of foam element
are substantially different.
Inventors: |
Stoia; Michael F.; (Rancho
Santa Margarita, CA) ; Blanding; David E.;
(Hawthorne, CA) ; Kim; Samuel; (Snohomish, WA)
; Datcher; Jarrett Reed; (Saint Louis, MO) |
Correspondence
Address: |
TUNG & ASSOCIATES / RANDY W. TUNG, ESQ.
838 W. LONG LAKE ROAD, SUITE 120
BLOOMFIELD HILLS
MI
48302
US
|
Assignee: |
The Boeing Company.
|
Family ID: |
40954750 |
Appl. No.: |
12/124092 |
Filed: |
May 20, 2008 |
Current U.S.
Class: |
165/185 |
Current CPC
Class: |
F28F 21/08 20130101;
F28F 21/02 20130101; F28D 9/0062 20130101; F28F 2265/26 20130101;
F28F 13/003 20130101 |
Class at
Publication: |
165/185 |
International
Class: |
F28F 7/00 20060101
F28F007/00 |
Claims
1. A heat exchanger, comprising: a thermally-conductive fluid
barrier having first and second surfaces; at least one first type
of foam element placed in thermally-conductive contact with said
first surface of said thermally-conductive fluid barrier and having
a first coefficient of thermal expansion; at least one second type
of foam element placed in thermally-conductive contact with said
second surface of said thermally-conductive fluid barrier and
having a second coefficient of thermal expansion; and wherein said
first coefficient of thermal expansion of said first type of foam
element and said second coefficient of thermal expansion of said
second type of foam element are substantially different.
2. The heat exchanger of claim 1 wherein said first type of foam
element comprises a reticulated metal foam layer.
3. The heat exchanger of claim 2 wherein said reticulated metal
foam layer comprises reticulated aluminum foam.
4. The heat exchanger of claim 1 wherein said second type of foam
element comprises a thermally conductive carbon foam layer.
5. The heat exchanger of claim 4 wherein said thermally conductive
carbon foam layer is segmented in multiple sections.
6. The heat exchanger of claim 1 further comprising a plurality of
stress relief blind slots provided in said first type of foam
element.
7. The heat exchanger of claim 6 wherein said stress relief blind
slots are placed in staggered relationship with respect to each
other.
8. The heat exchanger of claim 6 further comprising a plurality of
stress relief blind slots provided in said second type of foam
element.
9. A heat exchanger, comprising: a heat exchanger frame having a
first end plate, a second end plate placed in opposed relationship
with respect to said first end plate and at least one side bar
member placed at each end of said first end plate and said second
end plate; a thermally-conductive fluid barrier having first and
second surfaces provided in said heat exchanger frame; at least one
first type of foam element placed in thermally-conductive contact
with said first surface of said thermally-conductive fluid barrier
and having a first coefficient of thermal expansion; at least one
second type of foam element placed in thermally-conductive contact
with said second surface of said thermally-conductive fluid barrier
and having a second coefficient of thermal expansion; and wherein
said first coefficient of thermal expansion of said first type of
foam element and said second coefficient of thermal expansion of
said second type of foam element are substantially different.
10. The heat exchanger of claim 9 wherein said first type of foam
element comprises a reticulated metal foam layer.
11. The heat exchanger of claim 10 wherein said reticulated metal
foam layer comprises reticulated aluminum foam.
12. The heat exchanger of claim 9 wherein said second type of foam
element comprises a thermally conductive carbon foam layer.
13. The heat exchanger of claim 12 wherein said thermally
conductive carbon foam layer is segmented in multiple sections.
14. The heat exchanger of claim 9 further comprising a plurality of
stress relief blind slots provided in said first type of foam
element.
15. The heat exchanger of claim 14 wherein said stress relief blind
slots are placed in staggered relationship with respect to each
other.
16. The heat exchanger of claim 14 further comprising a plurality
of stress relief blind slots provided in said second type of foam
element.
17. A mixed carbon foam/metallic foam heat exchanger method,
comprising: providing a reticulated metal foam layer; providing a
thermally conductive carbon foam layer in thermally-conductive
contact with said reticulated metal foam layer; distributing a
first fluid through said reticulated metal foam layer; and
distributing a second fluid through said thermally conductive
carbon foam layer.
18. The method of claim 17 wherein said reticulated metal foam
layer comprises a reticulated aluminum foam layer.
19. The method of claim 17 further comprising a plurality of stress
relief blind slots in said reticulated metal foam layer.
20. The method of claim 17 further comprising a plurality of stress
relief blind spots in said thermally conductive carbon foam layer.
Description
TECHNICAL FIELD
[0001] The disclosure relates to ram air heat exchangers for
aircraft. More particularly, the disclosure relates to a mixed
carbon foam/metallic heat exchanger having thermally conductive
carbon foam layers which alternate with metal foam layers to allow
for the fabrication of heat exchanger cores using materials having
vastly different coefficients of thermal expansion (CTE).
BACKGROUND
[0002] In the manufacture of ram air heat exchangers using
thermally conductive carbon foam as a thermal management material,
metallic and carbon elements may be used in fabrication of the heat
exchanger core. The metallic and carbon elements used in
fabrication of the heat exchanger core may have different
coefficients of thermal expansion (CTE). Therefore, during
fabrication, high-temperature vacuum brazing processes may generate
thermal stresses within the heat exchanger core during the heat-up
and cool-down phases of the brazing process.
[0003] Therefore, fabrication processes that address thermal
stresses caused by mismatched coefficients of thermal expansion
(CTE) in a mixed carbon foam/metallic heat exchanger may be
desirable.
SUMMARY
[0004] The disclosure is generally directed to a heat exchanger. An
illustrative embodiment of the heat exchanger includes a
thermally-conductive fluid barrier having first and second
surfaces, at least one first type of foam element placed in
thermally-conductive contact with the first surface of the
thermally-conductive fluid barrier and having a first coefficient
of thermal expansion and at least one second type of foam element
placed in thermally-conductive contact with the second surface of
the thermally-conductive fluid barrier and having a second
coefficient of thermal expansion. The first coefficient of thermal
expansion of the first type of foam element and the second
coefficient of thermal expansion of the second type of foam element
are substantially different.
[0005] The disclosure is further generally directed to a mixed
carbon foam/metallic foam heat exchanger method. An illustrative
embodiment of the method includes providing a reticulated metal
foam layer, providing a thermally conductive carbon foam layer in
thermally-conductive contact with the reticulated metal foam layer,
distributing a first fluid through the reticulated metal foam layer
and distributing a second fluid through the carbon foam layer.
BRIEF DESCRIPTION OF THE ILLUSTRATIONS
[0006] FIG. 1 is a perspective view of an illustrative embodiment
of the heat exchanger.
[0007] FIG. 2 is an enlarged sectional view, taken along section
line 2 in FIG. 1, of a reticulated metal foam layer of the heat
exchanger.
[0008] FIG. 2A is an enlarged sectional view, taken along section
line 2A in FIG. 1, of a thermally conductive carbon foam layer of
the heat exchanger.
[0009] FIG. 2B is a sectional view illustrating a reticulated metal
foam layer and a thermally conductive carbon foam layer attached to
opposite sides of a thermally-conductive fluid barrier.
[0010] FIG. 3 is an enlarged sectional view illustrating staggered
fluid flow channels in the reticulated metal foam layers of the
heat exchanger.
[0011] FIG. 4 is an end view of the heat exchanger shown in FIG.
1.
[0012] FIG. 5 is a flow diagram which illustrates an illustrative
embodiment of a mixed carbon foam/metallic foam heat exchanger
method.
[0013] FIG. 6 is a flow diagram of an aircraft production and
service methodology.
[0014] FIG. 7 is a block diagram of an aircraft.
DETAILED DESCRIPTION
[0015] Referring initially to FIGS. 1-4, an illustrative embodiment
of the mixed carbon foam/metallic foam heat exchanger, hereinafter
heat exchanger, is generally indicated by reference numeral 1 in
FIG. 1. The heat exchanger 1 may include a heat exchanger frame 2
which may be aluminum, for example and without limitation, and may
include an upper end plate 3; a lower end plate 4 placed in an
opposed relationship with respect to the upper end plate 3; and
spaced apart end plates 5 at respective ends of the upper end plate
3 and the lower end plate 4. At each end of the heat exchanger
frame 2, carbon foam layers 14 may be exposed through plate slots 6
which separate adjacent side bar members 5 from each other.
[0016] At least one ductile thermal management material layer 10
may be provided in the heat exchanger frame 2. As shown in FIG. 2,
the ductile thermal management material layer 10 may be reticulated
metal foam such as reticulated aluminum foam, for example and
without limitation. At least one thermally conductive carbon foam
layer 14 may be provided in the heat exchanger frame 2 in
thermally-conductive contact with at least one ductile thermal
management material layer 10. The ductile thermal management
material layer 10 and the thermally conductive carbon foam layer 14
may have different coefficients of thermal expansion (CTEs). As
shown in FIG. 2B, in some embodiments each ductile thermal
management material layer 10 may be separated from each carbon foam
layer 14 by a thermally-conductive fluid barrier 18. Accordingly,
the ductile thermal management material layer 10 may be attached to
a first surface 18a and the carbon foam layer 14 may be attached to
a second surface 18b of the thermally-conductive fluid barrier 18
according to the knowledge of those skilled in the art. The
thermally-conductive fluid barrier 18 may be a metal braze foil
layer, for example and without limitation.
[0017] As shown in FIGS. 1 and 3, multiple stress relief blind
slots 11 may extend into each ductile thermal management material
layer 10. The stress relief blind slots 11 may be placed in
generally parallel, staggered relationship with respect to each
other and may be oriented in generally perpendicular relationship
with respect to a longitudinal axis of the ductile thermal
management layer 10. Each stress relief slot 11 may or may not
extend across the entire thickness of the ductile thermal
management material layer 10. As shown in FIGS. 1 and 4, stress
relief blind slots 15 may also be provided in the thermally
conductive carbon foam layer 14 and each may or may not extend
across the entire thickness of the carbon foam layer 14. The stress
relief blind slots 11 and stress relief blind slots 15 may provide
stress relief for the heat exchanger 1 during manufacturing and in
operation. Furthermore, the stress relief blind slots 11 and stress
relief blind slots 15 may provide control of fluid flow losses
through the ductile thermal management material layer 10 and the
thermally conductive carbon foam layer 14, respectively, in
operation of the heat exchanger 1.
[0018] As shown in FIGS. 1 and 4, the ductile thermal management
material layers 10 and the thermally conductive carbon foam layers
14 may be arranged in the heat exchanger frame 2 in alternating
relationship with respect to each other, with each carbon foam
layer 14 sandwiched between a pair of ductile thermal management
material layers 10. The heat exchanger frame 2 may include multiple
side bar members 7 each of which may extend into a plate slot 6
between the end plates 5 at respective ends of the heat exchanger
frame 2. Each side bar member 7 may be generally placed between
ductile thermal management material layers 10 and generally
adjacent to a thermally conductive carbon foam layer 14.
[0019] In some applications of the heat exchanger 1, CTE induced
thermal stresses may be a function of length scale. Therefore, as
shown in FIGS. 1 and 4, the thermally conductive carbon foam layers
14 may be segmented in multiple sections and tolerance-fitted
together in the heat exchanger frame 2. Segmentation of the carbon
foam layers 14 may reduce the total length scale between each
element of the carbon foam layers 14 and the metallic portions of
the heat exchanger 1 such as the various elements of the heat
exchanger frame 2, for example and without limitation, to reduce
CTE induced thermal stresses between the carbon foam layers 14 and
those metallic portions of the heat exchanger 1 during operation of
the heat exchanger 1.
[0020] During fabrication of the heat exchanger 1, a vacuum brazing
process may be used as is known to those skilled in the art.
Accordingly, the ductile thermal management material layers 10 and
the thermally conductive carbon foam layers 14, separated by
thermally-conductive fluid barriers 18, may be stacked and brazed
together during fabrication. It will be appreciated by those
skilled in the art that during the vacuum brazing process, the high
thermal stresses resulting from thermal expansion and contraction
induced in the heat exchanger frame 2 of the heat exchanger 1 may
be absorbed by the ductile thermal management material layers 10.
The thermal management material layers 10 may not transfer the
thermal stresses from the heat exchanger frame 2 to the thermally
conductive carbon foam layers 14. This may prevent the application
of excessive thermally induced stress on the carbon foam layers
14.
[0021] In application of the heat exchanger 1, a first slot (not
shown) may be placed in fluid communication with the ductile
thermal management material layers 10 and a second slot (not shown)
may be placed in fluid communication with the thermally conductive
carbon foam layers 14. A first fluid (not shown) may be distributed
from the first slot through the thermal management material layers
10, and a second fluid (not shown) may be distributed from the
second slot through the carbon foam layers 14. Accordingly, heat
may be transferred by convection and conduction from the hotter to
the cooler of the first fluid and the second fluid through the
thermally-conductive fluid barrier 18 (FIG. 2B). The high thermal
stresses resulting from thermal expansion induced in the heat
exchanger 1 by the hotter of the first fluid and the second fluid
may be absorbed by the ductile thermal management material 10. This
may prevent the application of excessive thermally induced stress
on the carbon foam layers 14. The upper end plate 3, lower end
plate 4 and side bar members 5 of the heat exchanger frame 2 may
prevent loss of fluid from the heat exchanger 1.
[0022] Referring next to FIG. 5, a flow diagram 500 which
illustrates an illustrative embodiment of a mixed carbon
foam/metallic foam heat exchanger method is shown. In block 502, a
reticulated metal foam layer is provided. In block 503, a
thermally-conductive fluid barrier is provided in thermally
conductive contact with the reticulated metal foam layer. In block
504, a thermally conductive carbon foam layer is provided in
thermally-conductive contact with the thermally-conductive fluid
barrier. In block 506, a first fluid is distributed through the
reticulated metal foam layer. In block 508, a second fluid is
distributed through the carbon foam layer. Heat is transferred from
the hotter to the cooler of the first fluid and the second fluid.
The reticulated metal foam layer may absorb stresses which are
induced by thermal expansion during transfer of the heat between
the fluids, minimizing or eliminating thermal stresses exerted on
the carbon foam layer.
[0023] Referring next to FIGS. 6 and 7, embodiments of the
disclosure may be used in the context of an aircraft manufacturing
and service method 78 as shown in FIG. 6 and an aircraft 94 as
shown in FIG. 7. During pre-production, exemplary method 78 may
include specification and design 80 of the aircraft 94 and material
procurement 82. During production, component and subassembly
manufacturing 84 and system integration 86 of the aircraft 94 takes
place. Thereafter, the aircraft 94 may go through certification and
delivery 88 in order to be placed in service 90. While in service
by a customer, the aircraft 94 may be scheduled for routine
maintenance and service 92 (which may also include modification,
reconfiguration, refurbishment, and so on).
[0024] Each of the processes of method 78 may be performed or
carried out by a system integrator, a third party, and/or an
operator (e.g., a customer). For the purposes of this description,
a system integrator may include without limitation any number of
aircraft manufacturers and major-system subcontractors; a third
party may include without limitation any number of vendors,
subcontractors, and suppliers; and an operator may be an airline,
leasing company, military entity, service organization, and so
on.
[0025] As shown in FIG. 7, the aircraft 94 produced by exemplary
method 78 may include an airframe 98 with a plurality of systems 96
and an interior 100. Examples of high-level systems 96 include one
or more of a propulsion system 102, an electrical system 104, a
hydraulic system 106, and an environmental system 108. Any number
of other systems may be included. Although an aerospace example is
shown, the principles of the invention may be applied to other
industries, such as the automotive industry.
[0026] The apparatus embodied herein may be employed during any one
or more of the stages of the production and service method 78. For
example, components or subassemblies corresponding to production
process 84 may be fabricated or manufactured in a manner similar to
components or subassemblies produced while the aircraft 94 is in
service. Also, one or more apparatus embodiments may be utilized
during the production stages 84 and 86, for example, by
substantially expediting assembly of or reducing the cost of an
aircraft 94. Similarly, one or more apparatus embodiments may be
utilized while the aircraft 94 is in service, for example and
without limitation, to maintenance and service 92.
[0027] Although the embodiments of this disclosure have been
described with respect to certain exemplary embodiments, it is to
be understood that the specific embodiments are for purposes of
illustration and not limitation, as other variations will occur to
those of skill in the art.
* * * * *