U.S. patent application number 10/190046 was filed with the patent office on 2004-01-08 for unit cell u-plate-fin crossflow heat exchanger.
This patent application is currently assigned to Ingersoll-Rand Energy Systems, Inc.. Invention is credited to Haplau-Colan, Alexander, Hodous, Frederick Wells, Nash, James Stephen.
Application Number | 20040003916 10/190046 |
Document ID | / |
Family ID | 29999782 |
Filed Date | 2004-01-08 |
United States Patent
Application |
20040003916 |
Kind Code |
A1 |
Nash, James Stephen ; et
al. |
January 8, 2004 |
Unit cell U-plate-fin crossflow heat exchanger
Abstract
The invention recites a heat exchanger for the exchange of heat
between an internal fluid and an external fluid comprising at least
two heat exchange cells. Each heat exchange cell includes a first
plate having an outer surface, raised peripheral edges, an inlet
aperture, an outlet aperture, and a heat exchange area extending
between the inlet aperture and the outlet aperture. Each cell
further includes a second plate including raised peripheral edges,
an inlet aperture, an outlet aperture, and a heat exchange area
extending between the inlet aperture and the outlet aperture. The
inlet aperture of the first plate is aligned with the inlet
aperture of the second plate to define a cell inlet and the outlet
aperture of the first plate is aligned with the outlet aperture of
the second plate to define a cell outlet. The heat exchange area of
the first plate is aligned with the heat exchange area of the
second plate to define an internal U-shaped flow path and the
raised peripheral edges of the first plate connect to the raised
peripheral edges of the second plate to substantially enclosing the
U-shaped flow path between the first and second plate. An internal
finned member is disposed within the internal U-shaped flow path
and is attached to one of the first and second plates and an
external finned member is connected to the outer surface of the
first plate.
Inventors: |
Nash, James Stephen; (North
Hampton, NH) ; Haplau-Colan, Alexander; (Hampton,
NH) ; Hodous, Frederick Wells; (Sanford, ME) |
Correspondence
Address: |
MICHAEL BEST & FRIEDRICH LLP
3773 CORPORATE PARKWAY
SUITE 360
CENTER VALLEY
PA
18034-8217
US
|
Assignee: |
Ingersoll-Rand Energy Systems,
Inc.
Portmouth
NH
|
Family ID: |
29999782 |
Appl. No.: |
10/190046 |
Filed: |
July 3, 2002 |
Current U.S.
Class: |
165/153 ;
165/176 |
Current CPC
Class: |
F28D 21/0003 20130101;
F28F 2250/102 20130101; F28F 3/025 20130101; F28D 9/0056 20130101;
F28D 9/0043 20130101 |
Class at
Publication: |
165/153 ;
165/176 |
International
Class: |
F28D 001/02; F28D
007/06 |
Claims
What is claimed is:
1. A heat exchanger comprising at least two heat exchange cells for
the exchange of heat between an internal fluid and an external
fluid, each heat exchange cell comprising: a first plate having an
outer surface, raised peripheral edges, an inlet aperture, an
outlet aperture, and a heat exchange area extending between the
inlet aperture and the outlet aperture; a second plate including
raised peripheral edges, an inlet aperture, an outlet aperture, and
a heat exchange area extending between the inlet aperture and the
outlet aperture, the inlet aperture of the first plate aligned with
the inlet aperture of the second plate to define a cell inlet, the
outlet aperture of the first plate aligned with the outlet aperture
of the second plate to define a cell outlet, the heat exchange area
of the first plate aligned with the heat exchange area of the
second plate to define an internal U-shaped flow path, and the
raised peripheral edges of the first plate connected to the raised
peripheral edges of the second plate to substantially enclose the
U-shaped flow path between the first and second plates; an internal
finned member disposed within the internal U-shaped flow path, and
attached to one of the first and second plates, the internal finned
member defining flow channels; and an external finned member
connected to the outer surface of the first plate.
2. The heat exchanger of claim 1, wherein the heat exchange cells
are stacked on top of one another and the external finned member is
disposed between adjacent heat exchange cells, the external finned
member defining flow channels oriented substantially perpendicular
to the flow channels of the internal finned member.
3. The heat exchanger of claim 1, wherein each cell inlet defines
an inlet axis and each cell outlet defines an outlet axis, the
inlet and outlet axes defining a plane substantially perpendicular
to the internal flow channels.
4. The heat exchanger of claim 1, wherein each of the heat exchange
cells includes a turning region receiving a flow of the internal
fluid from the internal finned member and redirecting the flow in
substantially the opposite direction to the cell outlet.
5. The heat exchanger of claim 1, wherein the first and second
plates further define a slot within each plate, the slots having
raised peripheral edges connected to one another to at least
partially enclose the U-shaped flow path.
6. The heat exchanger of claim 1, wherein the heat exchange area of
the first plate and the heat exchange area of the second plate
align with one another to define two U-shaped flow paths providing
two distinct flow paths that substantially mirror one another.
7. The heat exchanger of claim 6, wherein the cell inlet and the
cell outlet are disposed between the two U-shaped flow paths.
8. A heat exchanger for the exchange of heat between an internal
fluid and an external fluid, the heat exchanger comprising: a
plurality of heat exchange cells stacked in a stackwise direction,
each cell including first and second plates, each plate having
peripheral edges raised in a first direction, an inlet aperture
having internal edges raised in a second direction substantially
opposite the first direction, an outlet aperture having internal
edges raised in the second direction, and a heat exchange area
extending between the inlet aperture and the outlet aperture, the
second plate being inverted with respect to the first plate such
that the inlet aperture of the first plate aligns with the inlet
aperture of the second plate to define a cell inlet, the outlet
aperture of the first plate aligns with the outlet aperture of the
second plate to define a cell outlet, the heat exchange area of the
first plate aligns with the heat exchange area of the second plate
to define an internal U-shaped flow path, and the peripheral edges
of the first plate connect to the peripheral edges of the second
plate to substantially enclose the U-shaped flow path; wherein the
inlet internal edges of adjacent heat exchange cells align with and
are connected to one another to define an inlet manifold and the
outlet internal edges of adjacent heat exchange cells align with
and are connected to one another to define an outlet manifold.
9. The heat exchanger of claim 8, wherein the U-shaped flow path
further includes a turning region, a first flow leg extending in a
first flow direction from the cell inlet to the turning region, and
a second flow leg extending in a second flow direction from the
turning region to the cell outlet, the second flow direction
substantially opposite the first flow direction.
10. The heat exchanger of claim 9, further comprising a first
internal finned member disposed within the first flow leg, a second
internal finned member disposed within the second flow leg, and a
turning finned member disposed within the turning region.
11. The heat exchanger of claim 8, wherein the heat exchange cells
include a top surface and a bottom surface and wherein a first
external finned member is connected to one of the top surface and
bottom surface.
12. The heat exchanger of claim 11, wherein each cell inlet defines
an inlet axis extending from the first plate to the second plate
and each cell outlet defines an outlet axis extending from the
first plate to the second plate, the inlet and outlet axes defining
a plane substantially parallel to the external flow channels.
13. The heat exchanger of claim 8, wherein the first and second
plates further define a slot within each plate, the slots having
raised peripheral edges connected to one another to at least
partially enclose the U-shaped flow path.
14. The heat exchanger of claim 8, wherein the internal U-shaped
flow path within each heat exchange cell is a first internal
U-shaped flow path, and wherein the first plate and the second
plate further define a second internal U-shaped flow path that is a
substantial mirror image of the first U-shaped flow path.
15. A recuperated combustion turbine engine comprising: a
compressor operable to produce a flow of compressed gas; a
combustor receiving the flow of compressed gas and combusting it
with a flow of fuel to produce a flow of products of combustion; a
turbine receiving the flow of products of combustion and
discharging an exhaust gas, the turbine operable under the
influence of the flow of products of combustion therethrough; and a
plate-fin heat exchanger having a plurality of heat exchange cells
stacked in a stackwise direction, each heat exchange cell including
first and second plates having raised peripheral edges connected to
one another to define an inner U-shaped flow path, a cell inlet,
and a cell outlet, each heat exchange cell including a finned
member connected to one of the first and second plates and disposed
within the inner U-shaped flow path to define internal flow
channels; wherein the flow of exhaust gas passes through the heat
exchanger along a first flow path between adjacent heat exchange
cells and the flow of compressed gas passes through the heat
exchanger along the U-shaped flow path within the heat exchange
cells.
16. The engine of claim 15, wherein each U-shaped flow path further
includes a turning region, a first flow leg extending in a first
flow direction from the cell inlet to the turning region, and a
second flow leg extending in a second flow direction substantially
opposite the first flow direction from the turning region to the
cell outlet.
17. The engine of claim 16, wherein the finned member is a first
finned member disposed within the first flow leg, each heat
exchange cell further including a second internal finned member
disposed within the second flow leg, and a turning finned member
disposed within the turning region.
18. The engine of claim 15, wherein the heat exchange cells include
a top surface and a bottom surface and wherein a first external
finned member is connected to one of the top surface and bottom
surface to define external flow channels substantially
perpendicular to the internal flow channels.
19. The engine of claim 15, wherein the cell inlets of adjacent
heat exchange cells are aligned and attached to one another to
define an inlet manifold and cell outlets of adjacent heat exchange
cells are aligned and attached to one another to define an outlet
manifold.
20. The engine of claim 15, wherein each cell inlet defines an
inlet axis and each cell outlet defines an outlet axis, the inlet
and outlet axes defining a plane substantially perpendicular to the
internal flow channels.
21. The engine of claim 15, wherein the first and second plates
further define a slot within each plate, the slots having raised
peripheral edges connected to one another to at least partially
enclose the U-shaped flow path.
22. The engine of claim 15, wherein the U-shaped flow path within
each heat exchange cell is a first U-shaped flow path, and wherein
the first plate and the second plate define a second U-shaped flow
path that is a substantial mirror image of the first U-shaped flow
path.
Description
BACKGROUND AND SUMMARY OF THE INVENTION
[0001] The present invention relates to combustion turbine engines,
and particularly to recuperated microturbine engines. More
particularly, the present invention relates to recuperated
microturbine engines employing plate-fin recuperators.
[0002] Recuperators are heat exchangers used to transfer heat from
a hot fluid to a cold fluid. In the case of microturbine engines,
the hot fluid is generally turbine exhaust gas while the cold fluid
is generally compressed air exiting a compressor. The recuperator
preheats the compressed air prior to combustion to improve the
overall efficiency of the engine.
[0003] To maximize the efficiency of the engine, it is desirable to
use the most effective recuperator possible. To that end,
counterflow plate-fin type recuperators are often employed.
However, counterflow plate-fin recuperators require inlet manifolds
and outlet manifolds spaced apart from one another, increasing the
complexity of the heat exchanger. In addition, the spaced apart
manifolds reduce the amount of area that can be used for efficient
heat exchange.
[0004] Crossflow heat exchangers are known to be less effective
than counterflow heat exchangers. To improve crossflow heat
exchanger effectiveness, one of the flows can make two or more
passes across the other flow. One way to produce a multi-pass
crossflow heat exchanger is to provide a U-shaped path for one of
the flows. Tube-type heat exchangers that employ U-shaped tubes are
known.
[0005] Thus, according to the present invention a heat exchanger
for the exchange of heat between an internal fluid and an external
fluid comprises at least two heat exchange cells. Each heat
exchange cell includes a first plate having an outer surface,
raised peripheral edges, an inlet aperture, an outlet aperture, and
a heat exchange area extending between the inlet aperture and the
outlet aperture. Each cell further includes a second plate
including raised peripheral edges, an inlet aperture, an outlet
aperture, and a heat exchange area extending between the inlet
aperture and the outlet aperture. The inlet aperture of the first
plate is aligned with the inlet aperture of the second plate to
define a cell inlet and the outlet aperture of the first plate is
aligned with the outlet aperture of the second plate to define a
cell outlet. The heat exchange area of the first plate is aligned
with the heat exchange area of the second plate to define an
internal U-shaped flow path and the raised peripheral edges of the
first plate connect to the raised peripheral edges of the second
plate to substantially enclosing the U-shaped flow path between the
first and second plate. An internal finned member is disposed
within the internal U-shaped flow path and is attached to one of
the first and second plates and an external finned member is
connected to the outer surface of the first plate.
[0006] In preferred embodiments, the heat exchange cells include
multiple finned members disposed within the U-shaped flow path to
enhance the heat transfer efficiency.
[0007] In another preferred embodiment, the cell inlets align with
one another and define an inlet manifold and the cell outlets align
with one another to define an outlet manifold. The heat exchanger
inlet manifold and outlet manifolds align with one another relative
to the external fluid flow to maximize useable heat exchange space
for a fixed volume. In addition, two separate and distinct U-shaped
flow paths are provided to improve the heat exchanger
effectiveness.
[0008] In still other preferred embodiments, the heat exchange
cells include a slot disposed between the parallel flow regions of
the U-shaped flow path. The slot separates the hottest portions of
the heat exchanger area from the coolest portions.
[0009] Additional features and advantages will become apparent to
those skilled in the art upon consideration of the following
detailed description of preferred embodiments exemplifying the best
mode of carrying out the invention as presently perceived.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The detailed description particularly refers to the
accompanying figures in which:
[0011] FIG. 1 is an exploded view of a heat exchange cell of a
recuperator in accordance with the present invention;
[0012] FIG. 2 is a cross sectional view taken along line 2-2 in
FIG. 1, and illustrating several heat exchange cells;
[0013] FIG. 3 is an exploded view of another embodiment of the heat
exchange cell;
[0014] FIG. 4 is a partially broken away top view of the
recuperator of FIG. 1;
[0015] FIG. 5 is a partial front view of the recuperator of FIG. 4,
taken along line 5-5 in FIG. 4;
[0016] FIG. 6 is a partial perspective view of a cell inlet of the
heat exchange cell of FIG. 1;
[0017] FIG. 7 is a cross sectional view taken along line 7-7 in
FIG. 6;
[0018] FIG. 8 is a cross sectional view taken along line 8-8 of
FIG. 1 and illustrating several heat exchange cells;
[0019] FIG. 9 is a schematic representation of a recuperated
microturbine engine in accordance with the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
[0020] A recuperated microturbine engine 10 in accordance with the
present invention is illustrated schematically in FIG. 9. The
engine 10 includes a compressor 15, a turbine 20, a generator 25, a
combustor 30, and a recuperator 35. The turbine 20 includes a
rotary element (not shown) that rotates in response to a flow of
products of combustion. The turbine rotary element is coupled to a
compressor rotary element (not shown) and to a generator rotary
element (also not shown) or other driven device. The turbine
rotation rotates the compressor rotary element to produce a supply
of compressed gas 40, typically air, and further rotates the
generator rotary element to produce a current of electricity. There
are many different arrangements of microturbine engines 10
including engines that employ two turbines, or engines that drive
devices other than generators 25. The present invention functions
with any arrangement that uses a turbine 20 and a flow of
compressed gas 40. Therefore, the invention should not be limited
to the arrangement of FIG. 9.
[0021] In a recuperated microturbine engine 10, the supply of
compressed air 40 flows to a recuperator 35 or heat exchanger where
it is preheated. The air enters the recuperator 35 through an inlet
manifold 45, flows along an internal flow path 50, and exits the
recuperator at an outlet manifold 55. The preheated air 60 flows to
the combustor 30 where it is combined with a fuel flow 65 and
combusted to generate a flow of products of combustion. The
products of combustion flow through the turbine 20 imparting
rotational energy to the turbine rotary element, which in turn
rotates the compressor rotary element to produce the flow of
compressed air 40 and rotates the generator rotary element to
generate electricity. The products of combustion leave the turbine
20 as a flow of exhaust gas 70. The exhaust gas 70, which is still
quite hot, is directed through the recuperator 35 in an external
flow path direction 75, allowing heat transfer to the relatively
cool compressed air stream 40 flowing along the internal flow path
50. The exhaust gas 70 exits the recuperator 35 and is vented to
the atmosphere or further processed as desired. The use of a
recuperator 35 in the standard Brayton cycle allows for increased
thermal efficiency, with the effectiveness of the recuperator 35
directly effecting the thermal efficiency of the cycle.
[0022] Referring to FIGS. 1 and 2, one construction of a heat
exchange cell 80 includes a lower plate 85, an upper plate 90, a
plurality of inner fin members 95, two turning region fin members
100, and a plurality of outer fin members 105. The lower plate 85
defines an inlet aperture 110, an outlet aperture 115, heat
exchange areas 120, two turning regions 125, and a slot 130. The
peripheral edges 135 surrounding the outside of the plates 85, 90
and defining the slots 130 are raised toward the interior of the
heat exchange cell 80, as is best shown in FIG. 2. Interior edges
140 surround the inlet aperture 110 and the outlet aperture 115 and
are raised away from the interior of the heat exchange cell 80. The
peripheral edges 135 and interior edges 140 will be discussed in
greater detail below.
[0023] To assemble the heat exchange cell 80 of FIG. 1, inner fin
members 95 first attach to the lower or upper plate 85, 90 in the
heat exchange area 120. The inner fin members 95, which are
generally corrugated pieces of metal, define internal flow channels
that guide the flow from the inlet aperture 110 to one of the
turning regions 125. Turning region fin members 100 attach to the
lower or upper plates 85, 90 at either end to turn the fluid and
redirect it toward the outlet aperture 115. Additional inner fin
members 95 attach to the lower or upper plate 85, 90 and receive
the flow from the turning regions 125. The inner fin members 95
guide the flow to the outlet aperture 115. Thus, the arrangement
illustrated in FIG. 1 provides two separate and distinct U-shaped
flow paths 145 within the heat exchange cell 80. Each U-shaped flow
path 145 includes an outbound flow leg 150, a flow reversing leg
155, and an inbound flow leg 160. The second U-shaped flow path 145
is positioned so that the flow follows a path that is a substantial
mirror image of the path followed by the flow within the first
U-shaped flow path 145.
[0024] The upper plate 90, which is substantially identical to the
lower plate 85, is inverted and positioned relative to the lower
plate 85 so that the inlet apertures 110, outlet apertures 115, and
slots 130 align with one another. The peripheral edges 135 of the
upper plate 90 contact the peripheral edges 135 of the lower plate
85, thereby sandwiching the inner fin members 95 between the plates
85, 90. The peripheral edges 135 are connected to one another
utilizing a suitable attachment method (e.g., welding, soldering,
brazing, bolting, etc.) to seal all but the inlet apertures 110 and
the outlet apertures 115. The aligned inlet apertures 110 define a
cell inlet 165 where fluid flow enters the two U-shaped flow paths
145 and the aligned outlet apertures 115 define a cell outlet 170
where fluid flows out of the two U-shaped flow paths 145. The cell
inlet defines an axis 11-11 that extends through the centers of the
inlet apertures 110 from the lower plate 85 to the upper plate 90.
The cell outlet defines an axis 12-12 that extends through the
centers of the outlet apertures 115 from the lower plate 85 to the
upper plate 90. The cell inlet and outlet axes are substantially
parallel to each other and together define a plane that is
substantially perpendicular to the flow channels defined by the
inner fin member 95.
[0025] The aligned slots 130 separate the outbound flow legs 150
and the inbound flow legs 160 of the U-shaped flow paths 145. The
exhaust gas 70 flowing through the recuperator 35 along exhaust gas
flow direction 75 is at its hottest temperature when adjacent the
inbound flow leg 160 and at its coolest temperature when adjacent
to the outbound flow leg 150. In response to these temperature
differences and the thermal gradients created thereby, the heat
exchange area 120 supporting the inbound flow leg 160 of the
U-shaped flow paths 145 will have a tendency to thermally expand to
a greater extent than the heat exchange area 120 supporting the
outbound flow leg 150 of the U-shaped flow path 145. This
differential thermal expansion can result in large thermal stress
levels and structural failure if left unchecked. The slot 130
separates the outbound flow legs 150 from the inbound flow legs 160
and allows the legs 150, 160 to substantially independently expand,
thereby reducing the thermal stress within the heat exchange cells
80.
[0026] Outer fin members 105 attach to the outer surface 162 of the
heat exchange cell 80 to define external flow channels that guide
the flow of exhaust gas 70 around the outside of the heat exchange
cell 80 and define the flow path 75. The outer fin members 105 are
generally corrugated metal pieces like the inner fin members 95,
however the outer fin member corrugations are turned approximately
ninety degrees with respect to the corrugations of the inner fin
members 95. Thus, the outbound flow leg 150 and inbound flow leg
160 of the U-shaped flow paths 145 and the external flow path
direction 75 are arranged in a generally crossflow orientation.
While the construction of FIG. 1 shows outer fin members 105 on
both the top and bottom outer surfaces 162 of the heat exchange
cell 80, other constructions may use outer fin members 105 on only
one of the top and bottom surface 162.
[0027] Slot 130 is open to the exhaust gas flow and permits, the
exhaust gas to travel vertically and into flow paths between
different adjacent heat exchange cells 80. This vertical flow is
minimal due to the substantially even distribution of exhaust gas
70 and the substantially equal exhaust gas pressures between
adjacent heat exchange cells 80. To prevent leakage out of the top
and bottom of the slot 130, a housing or duct 163 (shown partially
in FIG. 5) surrounds the stack of heat exchange cells 80. The duct
163 guides the flow of exhaust gas 70 into the recuperator 35 and
simultaneously prevents leakage through the top and bottom of the
stacked heat exchange cells 80. The duct 163 also prevents exhaust
gas from escaping from the recuperator 35 before it flows across
the entire U-shaped flow path 145 of the recuperator 35.
[0028] FIG. 2 better illustrates the peripheral edges 135 and the
inner fin members 95 of several heat exchange cells 80. FIG. 2 is a
cross sectional view of FIG. 1 taken along line 2-2 with three heat
exchange cells 80 stacked on top of one another along a stackwise
direction 13-13. It should be understood that FIG. 2 shows only
three heat exchange cells 80 for clarity, and that many heat
exchange cells 80 would be stacked on top of one another to
complete a recuperator 35. The inner fin members 95 illustrated in
FIG. 2 have a substantially sinusoidal cross-section. FIG. 7
illustrates an inner fin member 95 having a square wave
cross-section, rather than the sinusoidal section shown in FIG. 2.
Fin members 95, 100, 105 with many other cross sections will also
function with the invention (e.g., triangle-wave pattern, D-shape,
W-shape, etc.). In fact, the present invention will function with
any shape fin members 95, 100, 105 because the shape is likely to
only influence the overall effectiveness of the recuperator.
[0029] The peripheral edges 135 of the upper plate 90 contact those
of the lower plate 85 to facilitate connection of the plates 85, 90
and to substantially enclose the U-shaped flow path 145. The
peripheral edges 135 include an attachment portion 175 and an
angled portion 180. The angled portion 180 extends from the heat
exchange area 120 to the attachment portion 175, which is generally
parallel to the heat exchange area 120 of the plate 85, 90. The
attachment portions 175 of the upper plate 90 and lower plate 85
contact one another and provide a convenient attachment location
around the periphery of the heat exchange cell 80 and around the
inside border of the slot 130. Once sealed, the cell inlet 165 and
the cell outlet 170 become the only entry and exit points to the
U-shaped flow path 145. The actual shape of the peripheral edges
135 is not critical to the function of the invention. Therefore,
other shapes (e.g., Z-shaped, L-shaped, S-shaped, etc.) are
contemplated and will function with the invention so long as they
provide a convenient means of spacing the upper plate 90 heat
exchange area 120 from the lower plate 85 heat exchange area 120
while attaching the plates 85, 90 to one another. For example, FIG.
5 illustrates a construction of a recuperator 35 in which S-shaped
peripheral edges 135 are employed.
[0030] Turning to FIG. 3, an alternative construction of a U-shaped
heat exchange cell 80A in accordance with the present invention is
shown, wherein similar components are labeled with similar
reference numerals and the extension "A". The heat exchange cell
80A includes an upper plate 90A, a lower plate 85A, two inner fin
members 95A, a turning fin member 100A and four outer fin members
105A. The upper plate 90A and lower plate 85A are substantially
similar to the upper plate 90 and lower plate 85 of FIG. 2 with the
exception of the inlet and outlet aperture 110A, 115A locations.
Instead of positioning the apertures 110A, 115A away from the ends
of the plates 85A, 90A to provide two distinct U-shaped paths 145A,
the present construction positions the inlet and outlet apertures
110A, 115A near one of the ends. The present construction thus
provides a single U-shaped flow path 145A. Each plate 85A, 90A
includes a heat exchange area 120A, a turning region 125A,
peripheral edges 135A and apertures 110A, 115A having interior
edges 140A. The peripheral edges 135A of the upper plate 90A attach
to the peripheral edges 135A of the lower plate 85A as described
with respect to previous constructions to define a U-shaped flow
path 145A extending from the inlet aperture 110A to the outlet
aperture 115A. The inner fin members 95A and the turning fin member
100A are sandwiched between the plates 85A, 90A and guide the flow
along the U-shaped path 145A while improving the effectiveness of
the heat exchange cell 80A. The outer fin members 105A attach to
the outer surface 162A of the heat exchange cell 80A to guide the
flow of exhaust gas 70 across the U-shaped flow path 145A and
improve the effectiveness of the heat exchange cell 80A.
[0031] FIG. 4 is a top view of a recuperator 35 in accordance with
the present invention, better illustrating the fin member 95, 105
orientations. The inner fin members 95 positioned within the
individual heat exchange cells 80 extend generally from left to
right to define the internal flow paths 50. The outer fin members
105 positioned on the outer surfaces 162 of the individual heat
exchange cells 80 extend generally from front to back and define
the direction of flow of exhaust gas 75. Thus, the heat exchanger
of FIG. 4 includes four distinct crossflow heat exchange areas 120.
The slot 130 separates the heat exchange areas 120 supporting the
outbound flow leg 150 from the areas supporting the inbound flow
leg 160 and the inlet manifold 45 and outlet manifold 55 separate
the heat exchange areas 120 of the two U-shaped flow paths 145 from
one another.
[0032] The turning regions 125 also perform some heat transfer and
add to the overall effectiveness of the recuperator 35. In fact, as
the compressed air makes the turn in the turning regions 125, it is
closer to the more effective counterflow heat exchanger model.
[0033] FIG. 4 also illustrates the alignment of the inlet and
outlet manifolds 45, 55 relative to the direction of flow of
exhaust gas 75. By aligning the inlet and outlet manifolds 45, 55
the effective heat exchange area for a fixed length recuperator 35
is maximized, thereby improving the overall effectiveness of the
recuperator 35. The inlet and outlet manifold 45, 55 can be located
at one end of the recuperator 35A as illustrated in FIG. 3 to
maximize the useable length of a single flow U-shaped recuperator
35A. However, the multiple path recuperator 35 is preferred, as it
allows for reduced flow velocities within the U-shaped flow paths
145, thereby improving the heat exchanger performance and reducing
the pressure drop of the gas flowing through the internal flow path
50 (defined by the outbound flow leg 150, flow reversing leg 155,
and the inbound flow leg 160).
[0034] Turning to FIGS. 6 and 7, a perspective and end view of a
cell inlet 165 in accordance with the present invention better
illustrate the peripheral edges 135 and the aperture interior edges
140. The heat exchange area 120 of the plates 85, 90 supports the
outer fin members 105 as shown in FIG. 6. The peripheral edges 135
extend from the heat exchange area 120 toward the interior of the
heat exchange cell 80. The interior edges 140, on the other hand,
extend from the heat exchange area 120 of the plate 85, 90 away
from the interior of the heat exchange cell 80. This arrangement
allows each heat exchange cell 80 to sandwich an inner fin member
95 between the heat exchange areas 120 of the upper plate 90 and
lower plate 85 as shown in FIG. 7. In addition, the raised interior
edges 140 provide for sufficient space between adjacent heat
exchange cells 80 to accommodate one or more outer fin members 105
as shown in FIG. 6.
[0035] FIG. 8 illustrates the interior edges 140 of adjacent cell
inlets 165 attached to one another in a manner similar to that
described above with regard to the peripheral edges 135. The
interior edges 140 contact one another, thereby providing
sufficient space between the adjacent heat exchange cells 80 for
the outer fin members 105. Like the peripheral edges 135, any
suitable attachment method can be used, however welding is
preferred. In other constructions (not shown), support members
located away from the inlet and outlet manifolds 45, 55 provide
additional support to the adjacent heat exchange cells 80. The
support members attach to adjacent heat exchange cells 80 to
maintain the desired gap between adjacent heat exchange cells 80,
while still allowing free expansion and contraction in response to
temperature changes.
[0036] It should be noted that the figures contained herein are
meant to further clarify the reader's understanding of the
invention. To that end, many features are exaggerated or shown out
of scale for the sake of clarity. For example, the plates 85, 90
are shown as having a substantial thickness when compared to the
fin members 95, 105. In practice, the plates 85, 90 as well as the
fin members 95, 105 would be as thin as practicable to facilitate
more rapid heating and improved heat transfer. Therefore, the
drawings should not be interpreted as limiting the scope of the
invention in any way.
[0037] Although the invention has been described in detail with
reference to certain preferred embodiments, variations and
modifications exist within the scope and spirit of the invention as
described and defined in the following claims.
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