U.S. patent application number 13/062643 was filed with the patent office on 2011-09-01 for recuperative heat exchanger, fuel cell system including recuperative heat exchanger, and method of operating same.
This patent application is currently assigned to MODINE MANUFACTURING COMPANY. Invention is credited to Michael N. McGregor, Michael J. Reinke, Jeroen Valensa.
Application Number | 20110209859 13/062643 |
Document ID | / |
Family ID | 42005729 |
Filed Date | 2011-09-01 |
United States Patent
Application |
20110209859 |
Kind Code |
A1 |
Reinke; Michael J. ; et
al. |
September 1, 2011 |
Recuperative Heat Exchanger, Fuel Cell System Including
Recuperative Heat Exchanger, and Method of Operating Same
Abstract
A heat exchanger, such as a cathode recuperator for a high
temperature fuel cell system, has a corrugated separator, a barrier
and a plurality of flow channels. The corrugated separator has a
surface positioned along a heat exchange fluid flow path, opposite
ends of the separator having flattened corrugations. The barrier is
positioned adjacent the surface. The plurality of flow channels are
in the heat exchange fluid flow path and are at least partially
defined by the surface and the barrier. The flattened corrugations
are positioned adjacent crests in the corrugated separator and
secured to the barrier.
Inventors: |
Reinke; Michael J.;
(Franklin, WI) ; Valensa; Jeroen; (Muskego,
WI) ; McGregor; Michael N.; (Racine, WI) |
Assignee: |
MODINE MANUFACTURING
COMPANY
Racine
WI
|
Family ID: |
42005729 |
Appl. No.: |
13/062643 |
Filed: |
September 10, 2009 |
PCT Filed: |
September 10, 2009 |
PCT NO: |
PCT/US2009/056432 |
371 Date: |
May 12, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61095818 |
Sep 10, 2008 |
|
|
|
Current U.S.
Class: |
165/172 ;
29/890.03 |
Current CPC
Class: |
H01M 2008/1293 20130101;
F28D 7/106 20130101; F28D 9/0025 20130101; Y02E 60/50 20130101;
Y10T 29/4935 20150115; F28D 2021/0043 20130101; H01M 8/04014
20130101; H01M 8/04074 20130101 |
Class at
Publication: |
165/172 ;
29/890.03 |
International
Class: |
F28F 99/00 20060101
F28F099/00; B21D 53/02 20060101 B21D053/02 |
Claims
1. A heat exchanger comprising: a corrugated metal separator having
a surface positioned along a heat exchange fluid flow path,
opposite ends of the separator having flattened corrugations; a
barrier positioned adjacent the surface; and a plurality of flow
channels in the heat exchange fluid flow path at least partially
defined by the surface and the barrier; wherein the flattened
corrugations are secured to the barrier.
2. The heat exchanger of claim 1, wherein the heat exchange fluid
flow path is a first heat exchange fluid flow path, wherein the
surface is a first surface, wherein the barrier is a first barrier
and wherein the plurality of flow channels are a first plurality of
flow channels, wherein the corrugated separator further includes a
second surface positioned along a second heat exchange fluid flow
path, the heat exchanger further comprising: a second barrier
positioned adjacent the second surface; and a second plurality of
flow channels in the second heat exchange fluid flow path bounded
by the second surface and the second barrier; wherein the first
barrier and the second barrier are substantially concentric
cylinders, and wherein the first barrier is located radially inward
from the second barrier.
3. The heat exchanger of claim 2, wherein the corrugated separator
includes a first flattened region adjacent a first end of the
separator, a second flattened region adjacent a second end of the
separator, a corrugated region between the first flattened region
and the second flattened region, a first transition region
connecting the first flattened region and a first end of the
corrugated region, and a second transition region connecting the
second flattened region and a second end of the corrugated region,
and wherein the first barrier includes an inlet to the first heat
exchange fluid flow path, the inlet being positioned proximate the
first end of the corrugated region.
4. The heat exchanger of claim 3, wherein the inlet includes a
plurality of trapezoid-shaped openings.
5. The heat exchanger of claim 3, wherein the first barrier
includes an outlet from the first heat exchange fluid flow path,
the outlet being positioned proximate the second end of the
corrugated region.
6. The heat exchanger of claim 5, wherein the outlet includes a
plurality of trapezoid-shaped openings.
7. The heat exchanger of claim 1, wherein the corrugated separator
includes crests, wherein the crests are secured to the barrier by
one of soldering, brazing, welding, adhesive bonding, and cohesive
bonding.
8. The heat exchanger of claim 1, wherein the corrugated separator
is formed into a substantially cylindrical shape.
9. The heat exchanger of claim 8, wherein the corrugated separator
includes corrugations extending in a direction substantially
parallel to a central axis of the substantially cylindrical
shape.
10. The heat exchanger of claim 1, wherein the corrugated separator
includes a longitudinal direction in which the corrugations extend,
wherein the corrugated separator includes a first flattened region
adjacent a first longitudinal end of the separator, a second
flattened region adjacent a second longitudinal end of the
separator, a corrugated region between the first flattened region
and the second flattened region, a first transition region
connecting the first flattened region and a first end of the
corrugated region, and a second transition region connecting the
second flattened region and a second end of the corrugated region,
and wherein the first transition region and the first flattened
region include corrugations bent in a direction transverse to the
longitudinal direction, the corrugations overlapping adjacent
corrugations in the first flattened region.
11. The heat exchanger of claim 1, wherein the flattened
corrugations secured to the barrier substantially seal off the heat
exchange fluid flow path.
12. The heat exchanger of claim 1, wherein the corrugations include
a plurality of peaks and troughs, and wherein the flattened
corrugations are located adjacent one of the peaks and the
troughs.
13. A method of making a heat exchanger, the method comprising the
acts of: providing a corrugated metal separator sheet having metal
corrugations extending in a longitudinal direction; flattening the
metal corrugations into flattened portions positioned at first and
second longitudinal ends of the corrugated separator sheet;
positioning the corrugated separator sheet adjacent a
non-corrugated barrier to create a heat exchange flow path between
the corrugated separator sheet and the non-corrugated barrier; and
securing the flattened portions to a surface of the non-corrugated
barrier.
14. The method of claim 13, further comprising: forming the
corrugated separator sheet into a corrugated cylinder by joining a
first corrugation located at a first edge oriented parallel to the
corrugations and a second corrugation located at a second edge
oriented parallel to the corrugations.
15. The method of claim 13, wherein the act of flattening further
comprises: positioning the corrugated separator sheet adjacent a
sleeve such that crests of the corrugated separator sheet engage
the sleeve; positioning the corrugated separator sheet and sleeve
between two wheels spaced apart a distance smaller than a height of
the corrugations; rotating the two wheels in opposite directions to
feed the corrugated separator sheet and sleeve between the two
wheels, thereby forming one of the flattened portions flush with
the crests.
16. The method of claim 13, wherein the sleeve is substantially
cylindrical.
17. The method of claim 13, wherein the non-corrugated barrier is a
first non-corrugated barrier, the method further comprising:
positioning the corrugated separator sheet between the first
non-corrugated barrier and a second non-corrugated barrier to
define a first heat exchange fluid flow path on a first side of the
corrugated separator sheet and a second heat exchange fluid flow
path on a second side of the corrugated separator sheet.
18. The method of claim 17, wherein positioning the corrugated
separator sheet between the first non-corrugated barrier and a
second non-corrugated barrier includes positioning the corrugated
separator sheet in a substantially cylindrical space.
19. The method of claim 17, further comprising: providing an inlet
to the first heat exchange fluid flow path, the inlet being
positioned proximate a first end of the corrugations; and providing
an outlet to the first heat exchange fluid flow path, the outlet
being positioned proximate a second end of the corrugations;
wherein the acts of providing an inlet and providing an outlet
include creating apertures in one of the non-corrugated
barriers.
20. The method of claim 19, wherein the act of creating apertures
includes creating apertures in the non-corrugated barrier to which
the flattened portions are secured.
21. The method of claim 13, further comprising securing crests of
the corrugated separator sheet to the non-corrugated barrier.
22. A corrugated separator sheet for a heat exchanger, the
corrugated separator sheet comprising: a plurality of metal
corrugations extending parallel to one another in a longitudinal
direction, the corrugations having a plurality of peaks and a
plurality of troughs opposite the plurality of peaks; and a
flattened region proximate a longitudinal end of the separator
sheet; wherein the flattened region is adjacent the plurality of
peaks.
23. The corrugated separator sheet of claim 22, wherein the
flattened region is substantially flush with the plurality of
peaks.
24. The corrugated separator sheet of claim 22, wherein the
corrugated separator sheet is cylindrical.
25. The corrugated separator sheet of claim 22, wherein the
flattened region is a first flattened region, and wherein the
longitudinal end is a first longitudinal end, further comprising a
second flattened region proximate a second longitudinal end of the
separator sheet, wherein the second flattened region is adjacent
one of the plurality of peaks and the plurality of troughs.
26. The corrugated separator sheet of claim 25, wherein the first
flattened region is secured to a first cylindrical barrier and the
plurality of troughs are positioned adjacent a second cylindrical
barrier, wherein a first flow path is defined between the
corrugated separator sheet and the first cylindrical barrier and a
second flow path is defined between the corrugated separator sheet
and the second cylindrical barrier.
27. The corrugated separator sheet of claim 26, wherein the second
flattened region is adjacent the plurality of peaks, wherein the
second flattened region is secured to the first cylindrical
barrier.
28. The corrugated separator sheet of claim 26, further comprising
a corrugated region between the first flattened region and the
second flattened region, a first transition region connecting the
first flattened region and a first end of the corrugated region,
and a second transition region connecting the second flattened
region and a second end of the corrugated region, wherein the first
cylindrical barrier includes an inlet to the first flow path, the
inlet being positioned proximate the first end of the corrugated
region.
29. The corrugated separator sheet of claim 22, wherein the
flattened region is a first flattened region and the longitudinal
end is a first longitudinal end, the corrugated separator sheet
further comprising: a second flattened region adjacent a second
longitudinal end of the separator sheet; a corrugated region
between the first flattened region and the second flattened region;
a first transition region connecting the first flattened region and
a first end of the corrugated region; and a second transition
region connecting the second flattened region and a second end of
the corrugated region; wherein the first transition region and the
first flattened region include corrugations bent in a direction
transverse to the longitudinal direction, the corrugations
overlapping adjacent corrugations in the first flattened region.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority to U.S. Provisional
Patent Application Ser. No. 61/095,818, filed Sep. 10, 2008, the
entire contents of which is hereby incorporated by reference.
FIELD OF THE INVENTION
[0002] This invention relates to heat exchangers in general and in
more particular applications, to recuperative heat exchangers which
find many uses in industry, including in fuel cell systems.
BACKGROUND
[0003] A recuperative heat exchanger, or recuperator, is used to
optimize the overall system efficiency of a high temperature
application, such as a gas turbine or a high temperature fuel cell
system, by heating a low temperature incoming air stream to a
temperature closer to the desired process operating temperature via
the transfer of thermal energy from a high temperature process
waste stream of exhaust gas or air. Such a heat exchanger allows
for the efficient transfer of heat from the hot stream to the cold
stream while maintaining isolation of the two streams from each
other. In order to simplify the packaging of the recuperator into
the system, and in order to reduce the material costs of the
device, it is usually desirable to minimize the physical size and
weight of the recuperative heat exchanger. It is also typically a
principal object of such a heat exchanger to provide for high heat
exchanger effectiveness in order to maximize the degree to which
the heat is recuperated.
[0004] Heat exchanger effectiveness is defined as the ratio between
the actual rate at which heat is transferred between the two fluids
in a heat exchanger and the maximum possible heat transfer rate.
The maximum possible heat transfer rate is achieved when the exit
temperature of the fluid with the lower heat capacity is made to be
equal to the entering temperature of the other fluid, and can
theoretically be achieved in a heat exchanger of infinite length
with the fluids passing through it in a counter-flow orientation.
For most practical heat exchangers the effectiveness will be less
than one.
[0005] A cathode recuperator for high temperature fuel cell systems
such as, for example, solid oxide fuel cell (SOFC) systems, has
some unique performance requirements as compared to recuperators in
better-known applications such as, for example, gas turbines.
SOFC's are solid-state devices that use an oxide-conducting ceramic
electrolyte to produce electrical current by transferring oxygen
ions from an oxidizing gas stream at the cathode of the fuel cell
to a reducing gas stream at the anode of the fuel cell. This type
of fuel cell is seen as especially promising in the area of
distributed stationary power generation. SOFC's require an
operating temperature range which is the highest of any fuel cell
technology, giving it several advantages over other types of fuel
cells for these types of applications. The rate at which a fuel
cell's electrochemical reactions proceed increases with increasing
temperature, resulting in lower activation voltage losses for the
SOFC. The SOFC's high operating temperature precludes the need for
precious metal catalysts, resulting in substantial material cost
reductions. The elevated exit temperature of the flow streams allow
for high overall system efficiencies in combined heat and power
applications, which are well suited to distributed stationary power
generation.
[0006] The traditional method of constructing solid oxide fuel
cells has been as a large bundle of individual tubular fuel cells.
Systems of several hundred kilowatts of power have been
successfully constructed using this methodology. However, there are
several known disadvantages to the tubular design which severely
limit the practicality of its use in the area of 25 kW-100 kW
distributed stationary power generation. For example, producing the
tubes can require expensive fabrication methods, resulting in
achievable costs per kW that are not competitive with currently
available alternatives. As another example, the electrical
interconnects between tubes can suffer from large ohmic losses,
resulting in low volumetric power densities. These disadvantages to
the tubular designs have led to the development of planar SOFC
designs. The planar designs have been demonstrated to be capable of
high volumetric power densities, and their capability of being mass
produced using inexpensive fabrication techniques is promising.
[0007] As is known in the art, a single planar solid oxide fuel
cell (SOFC) consists of a solid electrolyte that has high oxygen
ion conductivity, such as yttria stabilized zirconia (YSZ); a
cathode material such as strontium-doped lanthanum manganite on one
side of the electrolyte, which is in contact with an oxidizing flow
stream such as air; an anode material such as a cermet of nickel
and YSZ on the opposing side of the electrolyte, which is in
contact with a fuel flow stream containing hydrogen, carbon
monoxide, a gaseous hydrocarbon, or a combination thereof such as a
reformed hydrocarbon fuel; and an electrically conductive
interconnect material on the other sides of the anode and cathode.
A number of these cells are assembled into a fuel cell stack, with
the electrically conductive interconnect material providing both
the electrical connection between adjacent cells and the flow paths
for the reactant flow streams to contact the anode and cathode.
Such cells can be produced by well-established production
methodologies such as screen-printing and ceramic tape casting.
[0008] It is critical in operation to prevent the anode flow from
mixing with the cathode flow, since the cathode flow will act as an
oxidizer to combust the fuel in the anode flow, leading to
potentially damaging combustion occurring within the fuel cell
system. High temperature gas-tight seals are therefore required
between the individual fuel cells and the interconnect material in
order to prevent such mixing from occurring. In order to meet the
requirements of operating at high temperatures, remaining stable in
both oxidizing and reducing environments, and other considerations
necessary for usage with SOFCs, these seals are typically
constructed of cements, glasses, or glass-ceramics.
[0009] As is known to those in the art, these types of sealing
materials are not capable of withstanding large differential
pressures. As a consequence, planar SOFC systems are typically not
capable of operation at elevated pressures, as are gas turbines.
This has resulted in the need for very low pressure drop, high
thermal efficiency recuperative heat exchangers to recover the
waste heat from the cathode exhaust in order to preheat the cathode
air feed. The power required to pressurize the cathode air is quite
often the largest single parasitic power draw of a SOFC system, so
minimizing the pressure drop in such a recuperator can provide
substantial gains in the overall electrical efficiency of the
system, thus potentially providing a critical commercial
advantage.
SUMMARY
[0010] In some embodiments, the invention provides a primary
surface annular heat exchanger suitable for use as a recuperator in
solid oxide fuel cell systems.
[0011] In some embodiments, the invention provides a heat exchanger
having a corrugated separator, a barrier and a plurality of flow
channels. The corrugated separator has a surface positioned along a
heat exchange fluid flow path, opposite ends of the separator
having flattened corrugations. The barrier is positioned adjacent
the surface. The plurality of flow channels are in the heat
exchange fluid flow path and are at least partially defined by the
surface and the barrier. The flattened corrugations are secured to
the barrier.
[0012] The invention also provides a method of making a heat
exchanger. The method includes the acts of providing a corrugated
separator sheet having corrugations extending in a longitudinal
direction, flattening the corrugations into flattened portions
positioned at first and second longitudinal ends of the corrugated
separator sheet, positioning the corrugated separator sheet
adjacent a non-corrugated barrier to create a heat exchange flow
path between the corrugated separator sheet and the non-corrugated
barrier, and securing the flattened portions to a surface of the
non-corrugated barrier.
[0013] The invention provides a corrugated separator sheet for a
heat exchanger. The corrugated separator sheet can include a
plurality of corrugations and a flattened region. The plurality of
corrugations extend parallel to one another in a longitudinal
direction, and have a plurality of peaks and a plurality of troughs
opposite the plurality of peaks. The flattened region is proximate
a longitudinal end of the separator sheet and is adjacent the
plurality of peaks.
[0014] The invention can also provide a primary surface annular
heat exchanger that is capable of achieving a high degree of heat
exchanger effectiveness with minimal pressure drop and minimal size
and weight impact on a system making use of such a heat
exchanger.
[0015] In some embodiments, the invention provides a method of
constructing a primary surface annular heat exchanger to exchange
heat between two flowstreams, the method providing reliable sealing
of the flowstreams from one another with a minimum number of parts
and low overall cost.
[0016] In one aspect of the invention, a primary surface annular
heat exchanger comprises a corrugated separator sheet with a first
surface exposed to a first heat exchanging fluid and a second
surface exposed to a second heat exchanging fluid. The first fluid
flows through a plurality of flow channels bounded by the first
surface of the corrugated separator sheet and a radially inwardly
located cylinder. The second fluid flows through a plurality of
flow channels bounded by the second surface of the corrugated
separator sheet and a radially outwardly located cylinder. Each of
the ends of the corrugated separator sheet has the corrugations
flattened and bonded to the radially inwardly located cylinder.
[0017] In another aspect of the invention, a method is provided for
constructing a primary surface annular heat exchanger. The method
of making the heat exchanger includes the steps of corrugating a
separator sheet and forming it into a corrugated cylinder by
joining a first corrugation located at a first edge oriented
parallel to the corrugations and a second corrugation located at a
second edge oriented parallel to the corrugations. The method of
making the heat exchanger may further include the steps of
flattening the corrugations at either end of the corrugated
cylinder, and bonding the flattened portions of the corrugations to
the surface of a non-corrugated cylinder.
[0018] Other aspects of the invention will become apparent by
consideration of the detailed description and accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a plan section view of a portion of a fuel cell
system employing a heat exchanger according to an embodiment of the
present invention;
[0020] FIG. 2 is a detail view of the portion II-II of the heat
exchanger of FIG. 1;
[0021] FIG. 3 is a perspective view of a single convolution of a
primary surface of a heat exchanger according to an embodiment of
the present invention;
[0022] FIG. 4 is an elevation view of a corrugated separator for
use in a heat exchanger according to an embodiment of the present
invention;
[0023] FIG. 5 is a partial perspective view of portions of a heat
exchanger according to an embodiment of the present invention;
[0024] FIG. 6 is a somewhat diagrammatic section view through a
flow channel of a heat exchanger according to the present invention
in order to illustrate the flowpaths;
[0025] FIG. 7 is a somewhat diagrammatic section view similar to a
portion of FIG. 6 but showing aspects of an alternate embodiment of
a heat exchanger according to the present invention;
[0026] FIG. 8 is a section view in the direction VIII-VIII of FIG.
6;
[0027] FIG. 9 is a perspective view of a corrugated separator for
use in a heat exchanger at a stage of manufacture according to an
embodiment of the present invention;
[0028] FIG. 10 is a detail view of the portion X-X of FIG. 9;
[0029] FIG. 11 is a somewhat diagrammatic view of a stage of
manufacture of a heat exchanger according to an embodiment of the
present invention; and
[0030] FIG. 12 is a diagrammatic view illustrating the geometric
relationship between certain of the components shown in FIG.
11.
DETAILED DESCRIPTION
[0031] Before any embodiments of the invention are explained in
detail, it is to be understood that the invention is not limited in
its application to the details of construction and the arrangement
of components set forth in the following description or illustrated
in the following drawings. The invention is capable of other
embodiments and of being practiced or of being carried out in
various ways. Also, it is to be understood that the phraseology and
terminology used herein is for the purpose of description and
should not be regarded as limiting. The use of "including,"
"comprising," or "having" and variations thereof herein is meant to
encompass the items listed thereafter and equivalents thereof as
well as additional items. Unless specified or limited otherwise,
the terms "mounted," "connected," "supported," and "coupled" and
variations thereof are used broadly and encompass both direct and
indirect mountings, connections, supports, and couplings. Further,
"connected" and "coupled" are not restricted to physical or
mechanical connections or couplings.
[0032] FIG. 1 illustrates an embodiment of a heat exchanger
according to the present invention employed in a solid oxide fuel
cell system. As has been previously disclosed in pending U.S.
patent application 2008/0038622 to Valensa et. al., whose contents
are hereby incorporated by reference in their entirety, a
recuperative heat exchanger to preheat cathode air for solid oxide
fuel cells using a cathode exhaust can be incorporated in an
annular volume surrounding the solid oxide fuel cell stacks and
associated high-temperature balance-of-plant in a solid oxide fuel
system. As shown in FIG. 1, an embodiment of a primary surface
recuperative heat exchanger 1 according to the present invention is
so incorporated into a solid oxide fuel cell system 100. The heat
exchanger 1 is arranged in an annular volume surrounding the solid
oxide fuel cell stacks and associated high-temperature
balance-of-plant, collectively 101. The advantages of such an
arrangement has been well-discussed in the aforementioned
application 2008/0038622.
[0033] As can be better seen in FIG. 2, the heat exchanger 1 as
depicted in the embodiment of FIG. 1 comprises a first plurality of
flowpaths A and a second plurality of flowpaths B. The plurality of
flowpaths A are bounded by a first surface 5 of a corrugated
separator sheet 2 and a first cylinder 4, or first barrier. The
plurality of flowpaths B are bounded by a second surface 6 of the
corrugated separator sheet 2 and a second cylinder 3, or second
barrier, said cylinder 3 being concentric to the cylinder 4 and
furthermore being larger in diameter than cylinder 4. The
corrugated separator sheet 2 is located in the annular gap between
the cylinders 3 and 4. In other embodiments, the first and second
cylinders may be substantially planar barriers or barriers having
other geometrical configurations such that flowpaths A and B are
configured to exchange heat.
[0034] A single convolution 7, or corrugation, of the corrugated
separator sheet 2 is shown in greater detail in FIG. 3. In the
embodiment shown, the convolution comprises a first crest 8, or
peak, formed so that the first separator sheet surface 5 assumes a
concave shape at the crest 8 and the second separator sheet surface
6 assumes a convex shape at the crest 8, and a second crest 9, or
trough, formed so that the first separator sheet surface 5 assumes
a convex shape at the crest 9 and the second separator sheet
surface 6 assumes a concave shape at the crest 9. A plurality of
generally straight sections 22 of the corrugated separator sheet 2
join the crests 8 and 9 of adjacent convolutions 7.
[0035] In some embodiments, the crests 8 are joined to the cylinder
3 by a method such as brazing, welding, gluing, or other methods of
joining known to those skilled in the art. In some embodiments, the
crests 9 are joined to the cylinder 4 by a method such as brazing,
welding, gluing, or other methods of joining known to those skilled
in the art. In some embodiments, it may be preferable to have a
bond between the crests 8 and the cylinder 3 in only certain
limited areas. In some embodiments, it may be preferable to have a
bond between the crests 9 and the cylinder 4 in only certain
limited areas.
[0036] Methods of corrugating a sheet to take such a form are
well-known to those skilled in the art of heat exchangers. It
should be understood that the shape of the corrugations shown in
the figures is meant to be illustrative of the overall concept, and
is not meant to be limiting with regard to the specific shape of
the corrugations. In other embodiments, the corrugated separator
sheet may have other geometrical configurations, such as triangular
corrugations (i.e., straight sections joining at crests of sharp
points), rectangular corrugations (i.e., straight sections joining
at flat crests) or curved corrugations (i.e., a sinusoidal
pattern), amongst others. Other types of corrugations commonly used
in heat exchangers, such as for example a corrugated separator
sheet having flat-crested convolutions, would be equally valid
substitutes for the geometry shown.
[0037] As is best seen in the elevation view of FIG. 4, the
corrugated separator sheet 2 can be divided into several distinct
regions along the flow length of the channels A and B: a zone D1 at
a first longitudinal end of the corrugated separator 2, wherein the
convolutions 7 are flattened in order to seal off a first end of
the plurality of flow channels A; a zone D2 at a second
longitudinal end of the corrugated separator 2 opposite the first
longitudinal end, wherein the convolutions 7 are similarly
flattened in order to seal off a second end of the plurality of
flow channels A, the second end of the flow channels A being
located opposite the first end of the flow channels A; a center
zone C wherein the convolutions are in an unflattened shape as
described above in reference to FIG. 3; a transition zone E1
located between and connecting the zones D1 and C; and a transition
zone E2 located between and connecting the zones D2 and C.
[0038] The flow paths through an embodiment of the heat exchanger 1
can be seen in FIG. 6. A first fluid flow 18 enters the flow
channels A by passing first through an annular flow channel 11
formed by the inner surface of cylinder 4 and a wall 16 located
radially inward therefrom, and second through an inlet 10 in the
cylinder 4. In the embodiment of FIG. 6 the inlet 10 is located in
the zone C of the corrugated separator sheet 2, adjacent the zone
E1. In one embodiment of the invention, depicted in FIG. 5, the
inlet 10 comprises a plurality of trapezoid-shaped openings in the
cylinder 4, each opening having a 180.degree. rotated orientation
as compared to its neighboring openings so that adjacent openings
are separated by a thin web oriented in a direction non-parallel to
the direction of the flow channels, thereby ensuring that all of
the flow channels A are fluidly connected to the annular flow
channel 11.
[0039] Referring again to the embodiment of the heat exchanger 1
shown in FIG. 6, the fluid flow 18 exits the flow channels A by
passing through an outlet 20 in the cylinder 4 and into an annular
flow channel 12 formed by the inner surface of cylinder 4 and a
wall 17 located radially inward therefrom, the outlet 20 being
located in the zone C of the corrugated separator sheet 2, adjacent
the zone E2. In one embodiment, the outlet 20 is constructed to be
similar to the inlet 10 of the embodiment shown in FIG. 5. A second
fluid flow 19 passes through the flow channels B in a direction
counter to the flow direction of the first fluid flow 18 passing
through the flow channels A. As shown in FIG. 6, the second fluid
flow 19 passes through an annular flow channel 13 located between
the cylinders 3 and 4, enters the flow channels B in the transition
zone E2, and exits from the flow channels B back into the annular
flow channel 13 in the transition zone E1.
[0040] An alternative embodiment, illustrated in FIG. 7, includes a
radially expanded section 21 of the cylinder 3. In this embodiment,
the fluid flow 19 exits the flow channels B in the zone C of the
corrugated separator sheet 2 rather than in the zone E1, and flows
into an annular flow channel 14 formed by the expanded section 21
and the cylinder 4. It should be understood that the alternative
embodiment shown in FIG. 7 can be applied in a similar manner to
the inlet end of the flow channels B.
[0041] In one embodiment, the shape of the convolutions in the
zones D1 and D2 is as shown in the section view of FIG. 8. The
convolutions in these zones have been folded over into a flattened
portion 32 (i.e., corresponding to D1) and flattened into the
cylinder 4, thereby sealing off the ends of the flow channels A.
Regions E1 and D1, and E2 and D2, include convolutions bent in a
direction transverse to the longitudinal direction in which the
convolutions extend, the convolutions overlapping adjacent
convolutions in the first and second flattened regions D1 and
D2.
[0042] The flattened portion 32 is positioned adjacent a crest of
the corrugated separator sheet 2. As can be seen, with reference to
FIG. 5, positioning the flattened portion 32 adjacent one set of
crests allows the flattened portion 32 to be secured to the
cylinder 4 such that the set of crests do not interfere. In
preferred embodiments, the flattened portion 32 is substantially
flush with the set of crests such that the flattened portion 32 and
set of crests engage the cylinder 4 together. With reference to
FIGS. 4-5, a second flattened portion (i.e., corresponding to D2)
is also positioned adjacent and flush with the set of crests and
secured to the first cylinder 4 in the same way as the first
flattened portion 32. In other embodiments, the second flattened
portion may be positioned adjacent and/or flush with the opposite
set of crests and secured to second cylinder 3, or another
barrier.
[0043] A process for forming a primary surface annular heat
exchanger according to the embodiments shown in FIGS. 4, 5 and 8
will now be described with reference to FIGS. 9-12. As best seen in
FIGS. 9 and 10, a corrugated separator sheet 2 is formed into a
closed loop by engaging a convolution 9a located at a first
longitudinal edge of the corrugated separator sheet into a
convolution 9b located at a second longitudinal edge of the
corrugated separator. In some preferable embodiments, the
engagement between the convolutions 9a and 9b is secured by
creating a metallurgical bond, such as by autogenous welding.
[0044] In some embodiments of the invention, the corrugated
separarator sheet is next slid over a cylinder 24, the cylinder 24
having an outer diameter that is approximately equal to the outer
diameter of the inner cylinder 4 of the primary surface annular
heat exchanger. In a prefereable embodiment the width of the
corrugated separator sheet is selected such that after engagement
of the convolutions 9a and 9b, the corrugated separator sheet will
not fit over the cylinder 24 in a free state. Since the nature of
the convolutions allow for relatively easy expansion of the
corrugated separator sheet, a most preferable embodiment would size
the width of the corrugated separator sheet so that a slight
stretching of the convolutions of the corrugated separator sheet
occurs as it is placed over the cylinder 24, thereby ensuring
uniform contact between the plurality of crests 9 and the cylinder
24.
[0045] In some embodiments of the invention, the corrugations in
the zones D1 and D2 of the corrugated separator sheet 2 are
flattened in a process illustrated in FIGS. 11 and 12. In such a
process, a first wheel 22 of a diameter substantially smaller than
the diameter of the cylinder 24 is positioned to be tangent to and
in contact with the inner surface of the cylinder 24, so that the
axis 26 of the wheel 22 and the axis 25 of the cylinder 24 are
parallel to one another and define a plane 28, the plane 28 being
the plane common to both axes 25 and 26. A second wheel 23 is
positioned such that the axis 27 of the second wheel 23 is parallel
to the axes 25 and 26 of the first wheel 22 and the cylinder 24,
and is located in the plane 28. The second wheel 23 is furthermore
positioned so that the tangent distance H1 between the wheels 22
and 23 is less than the sum of the convolution height H2 of the
corrugated separator 2 and the thickness T1 of the cylinder 24. The
wheels 22 and 23 are made to rotate about their respective axes 26
and 27, the wheel 22 rotating in a first direction indicated by the
arrow 29 and the wheel 23 rotating in a second direction indicated
by the arrow 30, said directions being opposite of one another,
thereby causing the cylinder 24 to rotate about its own axis 25 in
a direction indicated by the arrow 31. The rotation of the cylinder
24 causes successive convolutions of the corrugated separator to be
compressed as they pass under the wheel 23, thereby forming the
flattened zone D1 or D2 of the corrugated separator, the amount of
compression being determined by the tangential spacing H1. The
width of the wheel 23 and the axial location of the corrugated
separator relative to the wheel 23 can be selected in order to
control the width of the flattened zone D1 or D2 of the corrugated
separator.
[0046] In some embodiments, it may be preferable for the cylinder
24 to make multiple complete revolutions about its axis 25 and to
successively decrease the spacing H1 while the cylinder 24 is
revolving in order to flatten the convolutions in a more controlled
manner.
[0047] In some embodiments of the invention multiple pairs of the
wheels 22 and 23 are used to flatten the convolutions at both ends
of the corrugated separator 2 in the same operation.
[0048] In some embodiments of the invention the corrugated
separator is removed from the cylinder 24 and is assembled over the
cylinder 4. In some other embodiments the cylinder 24 may actually
be the cylinder 4.
[0049] In some embodiments of the invention the flattened zones D1
and D2 are bonded to the cylinder 4 by welding, brazing, gluing, or
other bonding processes known to those skilled in the art.
[0050] It should be understood that the embodiments described above
and illustrated in the figures are presented by way of example only
and are not intended as a limitation upon the concepts and
principles of the present invention. As such, it will be
appreciated by one having ordinary skill in the art that various
changes are possible.
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