U.S. patent application number 09/841463 was filed with the patent office on 2001-10-04 for offset counterflow matrix fin for a counterflow plate-fin heat exchanger with crossflow headers.
Invention is credited to Haplau-Colan, Alexander, Nash, James S..
Application Number | 20010025705 09/841463 |
Document ID | / |
Family ID | 27486052 |
Filed Date | 2001-10-04 |
United States Patent
Application |
20010025705 |
Kind Code |
A1 |
Nash, James S. ; et
al. |
October 4, 2001 |
Offset counterflow matrix fin for a counterflow plate-fin heat
exchanger with crossflow headers
Abstract
A heat exchanger includes a plurality of heat exchange cells
positioned in a stacked configuration with respect to each other.
Each cell includes first and second parting sheets, an internal
finned member, and at least one external finned member. The first
and second parting sheets include opposing first and second
surfaces, an inlet manifold portion, an outlet manifold portion, an
internal finned member portion and peripheral edges. The second
parting sheet is substantially superimposed by, is spaced apart
from and is coupled to the first parting sheet. The second surface
of the second parting sheet confronts the second surface of the
first parting sheet. The peripheral edges of the first and second
parting sheets are attached to each other. The internal finned
member is disposed between the second surfaces of the first and
second parting sheets and has a leading edge positioned adjacent to
the inlet manifold portion of the first and second parting sheets,
and a trailing edge is positioned adjacent to the outlet manifold
portion of the first and second parting sheets. The external finned
member is attached to one of the first and second parting sheet.
The external finned member has a leading edge and a trailing edge
and is positioned offset from the internal finned member such that
the leading edge of the external finned member outwardly extends
beyond the leading edge of the internal finned member and the
external finned member covers a portion of the inlet manifold
member.
Inventors: |
Nash, James S.; (West
Newbury, MA) ; Haplau-Colan, Alexander; (Hampton,
NH) |
Correspondence
Address: |
David B. Smith
Michael Best & Friedrich LLP
942 Memorial Parkway
Phillipsburg
NJ
08865-2726
US
|
Family ID: |
27486052 |
Appl. No.: |
09/841463 |
Filed: |
April 24, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09841463 |
Apr 24, 2001 |
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09409641 |
Oct 1, 1999 |
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09409641 |
Oct 1, 1999 |
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09239647 |
Jan 29, 1999 |
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5983992 |
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09239647 |
Jan 29, 1999 |
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08792261 |
Jan 31, 1997 |
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60010998 |
Feb 1, 1996 |
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Current U.S.
Class: |
165/167 ;
165/153; 165/166; 165/174; 165/81 |
Current CPC
Class: |
F28F 9/0268 20130101;
F28D 9/0043 20130101; F28F 2265/26 20130101; F28D 21/0003 20130101;
F28F 3/025 20130101; F28F 3/02 20130101 |
Class at
Publication: |
165/167 ;
165/166; 165/174; 165/153; 165/81 |
International
Class: |
F28F 003/00; F28F
003/08; F28F 009/02; F28F 007/00; F28D 001/02 |
Claims
What is claimed is:
1. A heat exchanger for transferring heat between an external fluid
and an internal fluid, the heat exchanger comprising: a plurality
of heat exchange cells positioned in a stacked configuration with
respect to each other, each cell being connected to at least one
adjacent cell, each cell including: a first parting sheet including
opposing first and second surfaces, a first inlet header portion, a
first outlet header portion, a first internal finned member portion
and peripheral edges; a second parting sheet substantially
superimposed by, spaced apart from and coupled to the first parting
sheet, the second parting sheet including opposing third and fourth
surfaces a second inlet header portion, a second outlet header
portion, a second internal finned member portion and peripheral
edges, the fourth surface of the second parting sheet confronting
the second surface of the first parting sheet, at least a portion
of the peripheral edges of the first and second parting sheets
attached to each other; an internal finned member disposed between
the second and fourth surfaces of the first and second parting
sheets, respectively, the internal finned member positioned at the
first and second internal finned member portions of the first and
second parting sheets, respectively, and having a leading edge
positioned adjacent to the first and second inlet header portions
of the first and second parting sheets, respectively, and a
trailing edge positioned adjacent to the first and second outlet
header portions of the first and second parting sheets,
respectively; at least one external finned member being attached to
at least one of the first surface of the first parting sheet and
the third surface of the second parting sheet, the external finned
member having a leading edge and a trailing edge, the external
finned member positioned such that the leading edge of the external
finned member outwardly extends beyond the trailing edge of the
internal finned member.
2. The heat exchanger of claim 1, further comprising inlet and
outlet finned members disposed between and attached to the inlet
and outlet header portions, respectively, of the first and second
parting sheets.
3. The heat exchanger of claim 1, wherein the internal finned
member is configured to direct the flow of a fluid generally along
a first path in a first direction and the inlet header portions of
the first and second parting sheets are configured to direct the
flow of the fluid generally along a second path in a second
direction substantially perpendicular to the first direction.
4. The heat exchanger of claim 3, wherein the outlet header
portions of the first and second parting sheets are configured to
direct the flow of the fluid generally along a third path
substantially perpendicular to the first path.
5. The heat exchanger of claim 1, wherein the at least one external
finned member is two external finned members, a first external
finned member attached to the first surface of the first parting
sheet and a second external finned member attached to the third
surface of the second parting sheet.
6. The heat exchanger of claim 3, wherein each external finned
member is configured to direct the flow of a second fluid in a
direction generally opposite the first direction.
7. The heat exchanger of claim 1 wherein the external finned
members of adjacent heat exchange cells are connected together.
8. The heat exchanger of claim 1 wherein the peripheral edges of
the first and second parting sheets of each heat exchange cell
further extend and connect to adjacent heat exchange cells.
9. A heat exchange cell of a heat exchanger for transferring heat
between an external fluid and an internal fluid, the heat exchange
cell comprising: a first parting sheet including opposing first and
second surfaces, a first inlet header portion, a first outlet
header portion and a first internal finned member portion; a second
parting sheet substantially superimposed by, spaced apart from and
coupled to the first parting sheet, the second parting sheet
including opposing third and fourth surfaces, a second inlet header
portion, a second outlet header portion and a second internal
finned portion, the fourth surface of the second parting sheet
confronting the second surface of the first parting sheet; an
internal finned member disposed between the first and second
parting sheets, at the first and second internal finned member
portions, the internal finned member having a leading edge and a
trailing edge; at least one external finned member being attached
to at least one of the first surface of the first parting sheet and
the third surface of the second parting sheet, the external finned
member having a leading edge and a trailing edge; an outlet header
connected to the first and second outlet header portions of the
first and second parting sheets, respectively, the trailing edge of
the internal finned member extending along the juncture of the
first and second outlet header portions to the first and second
internal finned member portions of the first and second parting
sheets, respectively; and an inlet header connected to the first
and second inlet header portions of the first and second parting
sheets, respectively, the leading edge of the internal finned
member extending along the juncture of the first and second inlet
header portions to the first and second internal finned member
portions of the first and second parting sheets, respectively, the
external finned member positioned offset from the internal finned
member such that the leading edge of the external finned member
outwardly extends beyond the trailing edge of the internal finned
member.
10. The heat exchange cell of claim 9, wherein the inlet and outlet
headers are cross-flow headers.
11. The heat exchange cell of claim 9, wherein the inlet and outlet
headers each further include a finned member.
12. The heat exchange cell of claim 9, wherein the internal finned
member is configured to direct the flow of a fluid generally along
a first plane in a first direction and the inlet header is
configured to direct the flow of the fluid generally along the
first plane in a second direction substantially perpendicular to
the first direction.
13. The heat exchange cell of claim 9, wherein the internal finned
member is configured to direct the flow of a fluid generally along
a first axis and the outlet header is configured to direct the flow
of the fluid generally along a third axis substantially
perpendicular to the first axis.
14. The heat exchange cell of claim 9, wherein the leading edge of
the at least one external finned member is positioned over the
outlet header.
15. The heat exchange cell of claim 9, wherein the at least one
external finned member is two external finned members, a first
external finned member attached to the first surface of the first
parting sheet and a second external finned member attached to the
third surface of the second parting sheet.
16. The heat exchange cell of claim 9, wherein the first and second
parting sheets further include peripheral edges and at least a
portion of the peripheral edges of the first and second parting
sheets are attached to each other.
17. The heat exchange cell of claim 16, wherein the first and
second parting sheets define a high pressure chamber and the
internal finned member is disposed within the chamber.
18. The heat exchange cell of claim 12, wherein each external
finned member is configured to direct the flow of a second fluid in
a direction generally opposite the first direction.
19. The heat exchanger of claim 11 the finned member of the inlet
and outlet headers each include convolutions.
20. The heat exchanger of claim 9 wherein the internal finned
member is connected to the second surfaces of the first and second
parting sheets.
Description
FIELD OF THE INVENTION
[0001] The present application is a continuation-in-part of U.S.
patent application Ser. No. 09/409,641 filed Oct. 1, 1999, which is
a continuation of U.S. patent application Ser. No. 09/239,647 filed
Jan. 29, 1999 (U.S. patent No. 5,983,992), which is a continuation
of U.S. patent application Ser. No. 08/792,261 filed Jan. 31, 1997
which, in turn, claims benefit under 35 U.S.C. Section 119(e) of
U.S. Provisional Application 60/010,998 filed Feb. 1, 1996. The
disclosures set forth in U.S. patent application Ser. Nos.
09/409,641, 09/239,647, and 08/792,261 and U.S. Provisional
Application 60/010,998 are hereby incorporated by reference
herein.
BACKGROUND OF THE INVENTION
[0002] This invention relates generally to plate-fin heat
exchangers and more particularly to a counter-flow plate-fin heat
exchanger with cross-flow headers used as a recuperator. Plate fin
heat exchangers are typically monolithic structures created by
brazing their many constituent pieces in a single furnace cycle.
This general design presents several problems including the
following:
[0003] 1. A plate fin heat exchanger typically includes hundreds,
if not thousands, of brazed joints. Thus, the overall quality of
the finished product depends on the reliability of each and every
brazed joint so that even one defective brazed joint can result in
the entire heat exchanger being scrapped. As a result, assembly
methods for plate fin heat exchangers are generally labor intensive
as assemblers must avoid the creation of even a single poor braze
among thousands in a typical heat exchanger.
[0004] 2. The dimensions of the constituent parts used to assemble
the heat exchanger must be maintained within close tolerances in
order that differences in thickness do not compound into gross
differences in load during the brazing cycle.
[0005] 3. Edge bars or closure bars used to carry load through the
edges of the heat exchanger make assembly both labor and material
intensive and create stiffness and mass discontinuities
antithetical to minimizing strain during transient thermal
operation.
[0006] With regard to the above design, counterflow plate-fin heat
exchangers with cross-flow headers typically include a stack of
headers sandwiched together to form an alternating gas/air/gas/air
header pattern. Each pair of adjacent gas and air headers is
separated by a relatively thin parting sheet. Additionally,
conventional plate-fin heat exchangers incorporate edge bars or
closure bars to seal about the perimeters of the parting sheets and
prevent overboard leakage from the high pressure side of the heat
exchanger. Inlet and outlet manifold ducts are welded transverse to
the edge bars after the headers are assembled and brazed. The edge
bars create a stiff and massive structural attachment between the
parting sheets. Thermal loading produces faster thermal response in
the lighter parting plates than the more massive edge bars. This
difference in response time rate combined with the relative
weakness of the parting plates can produce damage in the parting
plates. Due to differences in the position and structural
composition of the parting sheets and edge bars, the temperature
changes do not affect the bars and sheets at the same rate. Since
the parting sheets are structurally weaker than the edge bars, the
parting sheets are strained.
[0007] A second problem associated with the use of edge bars in
counterflow plate-fin heat exchangers is related to the sheet metal
manifold ducts that are welded to the edge bars. The manifolds are
welded to the stack of edge bars along the sides and comers of the
core adjacent the header openings. Like the parting sheets, the
manifold ducts respond quickly to changes in temperature. Since the
edge bars do not respond to changes in temperature as quickly as
the manifold ducts, the sheet metal experiences a shear load at or
near the weld. As a result, the weld and the base metal in the heat
affected zone is likely to become damaged.
[0008] U.S. Pat. No. 2,858,112 to Gerstung discloses a cross-flow
heat exchanger for transferring heat from a liquid (FIG. 1) in
which multiple pairs 10 of corrugated plates 12 and 14 are spaced
apart by air centering means 16 and heat exchanger or edge bar
elements 18 and 20. The edge bar elements 18 and 20 are sandwiched
between the aligned header openings 30 and 32 of the respective
plates 12 and 14. The utilization of the edge bar elements 18 and
20 adds undesirable rigidity and thermal mass discontinuity to the
structure. As a result, the various layers of the structure are
unable to move independently of one another during operation. Thus,
the heat exchanger disclosed in the Gerstung patent is not
appropriate for use with a gas turbine because the exchanger cannot
withstand the tremendous temperature extremes produced by a gas
turbine.
[0009] Great Britain Patent 1,304,692 to Lowery (FIGS. 1 and 5)
discloses a cross-flow heat exchanger for transferring heat from a
liquid including a plurality of metal plates 24 shaped and bonded
together. The plates 24 have fin members 16 and 17 bonded to their
respective outer surfaces. Each plate 24 has two centrally
apertured raised end portions 25 and 26 and also has two parallel
inverted channels 27 and 28. The respective units are assembled
together by placing the next unit in the sequence with its raised
end portions 25 and 26 in contact with equivalent raised end
portions of the previous unit in the sequence, and by applying
pressure to the juxtaposed pair of raised end portions 25 and 26.
The relatively large intermeshing surface areas of adjacent raised
end portions 25 and 26 results in the formation of rigid flow ducts
so that the various layers of the final structure are incapable of
moving and flexing relative to one another.
[0010] Based on the foregoing limitations known to exist in present
plate-fin heat exchangers, it would be beneficial to provide a heat
exchanger having a compliant bellows structure capable of
elastically absorbing deflections produced by temperature gradients
attendant with the heat exchange process and thermal gradients
associated with installation or operation, so that the individual
layers of the heat exchanger can move and flex freely relative to
one another, and can accommodate thermal deflections throughout of
plane deformation. It would be advantageous to provide a heat
exchange cell configured with graduated stiffness at a transition
section of the cell connecting the matrix to the cross-flow header
to reduce damaging strain accumulation and to increase the fatigue
life of the heat exchanger.
SUMMARY OF THE INVENTION
[0011] In accordance with certain preferred embodiments of the
present invention, a heat exchanger for transferring heat between
an external fluid and an internal fluid includes two or more heat
exchange cells. Each heat exchange cell preferably includes a top
plate having an inlet aperture at one end thereof and an outlet
aperture at the other end thereof, the top plate including a first
surface, a second surface and peripheral edges. The heat exchange
cell may also include a bottom plate juxtaposed with the top plate
having an inlet aperture at one end thereof and an outlet aperture
at the other end thereof. The bottom plate also preferably includes
a first surface, a second surface and peripheral edges, the
peripheral edges of the bottom and top plates being attached to one
another, whereby the second surfaces of the top and bottom plates
confront one another and the inlet and outlet apertures of the top
and bottom plates are in substantial alignment with one another.
The aligned inlet apertures and outlet apertures of the respective
attached top and bottom plates preferably provide an inlet manifold
on one side of the cell and an outlet manifold at the other side of
the cell. The inlet and outlet apertures of the top and bottom
plates may include substantially S-shaped raised flange portions
extending away from the first surfaces of the plates, the
substantially S-shaped raised flange portions terminating at
interior edges bounding the apertures. The attached top and bottom
plates preferably define a high pressure chamber between the second
surfaces thereof so that the internal fluid may pass through the
heat exchange cell at a higher pressure than the external fluid.
The heat exchanger also preferably includes an internal finned
member disposed within the high pressure chamber and attached to
the second surfaces of said top and bottom plates. The individual
heat exchange cells are preferably assembled one atop the other
with the adjacent interior edges of adjacent heat exchange cells
attached together for forming a compliant bellows structure capable
of elastically absorbing deflections produced during thermal
loading so that the heat exchange cells may move and flex relative
to one another.
[0012] In certain preferred embodiments, each heat exchange cell
includes an internal finned member and two external finned members,
a first one of the two external finned members being attached to
the first surface of the top plate and a second one of the two
external finned members being attached to the first surface of the
bottom plate. Each heat exchange cell is designed for passing the
external fluid through the two external finned members in a first
flow direction and for passing the internal fluid through the
internal finned member in a second flow direction substantially
counter to the first flow direction. The internal fluid may be high
pressure air passing through the internal finned member and the
external fluid may be a low-pressure product resulting from
combustion. In other embodiments, the internal fluid may be
compressor discharge gases and the external fluid may be turbine
discharge gases. During operation of the heat exchange cell, the
two external finned members capture heat from the external fluid
passing therethrough and transfer the heat to the internal finned
member. The internal finned member then transfers the heat to the
internal fluid passing therethrough.
[0013] Each top plate may include a substantially flat central
region between the inlet and outlet apertures thereof and the
bottom plate preferably includes a substantially flat central
region between the inlet and outlet apertures thereof, the
substantially flat central regions of the two plates being in
substantial alignment with one another. In certain embodiments, the
first one of the two external finned members overlies the
substantially flat central region of the top plate, the second one
of the two external finned members overlies the substantially flat
central region of the bottom plate, and the internal finned member
is disposed between the substantially flat central regions of the
top and bottom plates. The internal finned member may be in
substantial alignment with the two external finned members. The
internal finned member is preferably brazed to the second surfaces
of the top and bottom plates. In certain preferred embodiments, the
first and second external finned members of each heat exchange cell
may include substantially aligned leading edges for receiving the
external fluid passing between the cell layers and trailing edges
for discharging the external fluid after the external fluid has
passed therethrough. The substantially aligned leading edges of the
first and second external finned members are desirably
substantially remote from at least one leading peripheral edge of
the heat exchange cell for enabling the peripheral edge to deflect
toward and away from a heat exchange cell adjacent thereto. In
other preferred embodiments, the substantially aligned leading
edges of the first and second external finned members are
substantially offset from the aligned outlet apertures for enabling
each cell layer to deflect toward and away from a heat exchange
cell adjacent thereto. Offsetting the leading edges away from the
bellows structure enables the bellows to flex and bend without
being constrained by the external finned members. Placing the
leading edges of the external finned members away from the at least
one leading peripheral edge also reduces thermal forces acting upon
the top and bottom plates of each cell.
[0014] The trailing edges of the first and second external finned
members may also be in substantial alignment with one another, as
well as being substantially remote from at least one rear
peripheral edge of the heat exchange cell for enabling the cell to
move toward and away from a heat exchange cell adjacent thereto.
The substantially aligned trailing edges of the first and second
external finned members may also be substantially offset from the
aligned inlet apertures of the heat exchange cell for enabling each
cell to deflect toward and away from a heat exchange cell adjacent
thereto. Each heat exchange cell may also include at least one gas
turning finned member attached adjacent a peripheral edge of one of
the plates for directing the external fluid into a preferred path
for impinging upon the two external finned members.
[0015] As mentioned above, the internal finned member is desirably
disposed in the high pressure chamber of the cell and may have an
inlet edge for receiving the first gas from the inlet manifold and
an outlet edge for discharging the first gas to the outlet
manifold. Each heat exchange cell may also include an inlet
manifold finned member disposed in the high pressure chamber
between the inlet manifold and the inlet edge of the internal
finned member and an outlet manifold finned member disposed in the
high pressure chamber between the outlet manifold and the outlet
edge of the internal finned member. The inlet and outlet manifold
finned members direct the internal fluid in a first direction and
the internal finned member directs the internal fluid in a
direction substantially perpendicular to the first direction. As
mentioned above, heat is generally transferred between the external
and internal fluids when the internal fluid passes through the
internal finned member. The internal finned member of each cell is
adhered to the top and bottom plates for providing resistance
against differential pressure load so that no external pre-loading
of the heat exchange cell is required.
[0016] The top and bottom plates and the substantially S-shaped
raised flange portions thereof preferably have a substantially
uniform thickness, thereby minimizing the effects of thermal
expansion and contraction on the plates. At the outer perimeter of
the cell, the substantially S-shaped raised flange portions join
together to partially form and define a high pressure chamber,
while the inner edges of the substantially S-shaped raised flange
portions, i.e., the edges surrounding the inlet and outlet
apertures of the attached plates, diverge from one another in each
cell so that adjacent inner edges of adjacent cells may be attached
together. The adjacent interior edges of the adjacent cells are
preferably welded together to form a compliant bellows structure.
In highly preferred embodiments, the heat exchange cells are
attached to one another solely through the interior edges of the
raised flanges. In these embodiments, the sections of the
substantially S-shaped raised flanges away from or remote from the
interior edges are not attached together. This enables the
substantially S-shaped flange portions to independently move and
flex in response to compressive, tension and lateral forces.
[0017] The present invention also provides a heat exchanger for
transferring heat between an external fluid and an internal fluid.
The heat exchanger includes a plurality of heat exchange cells
positioned in a stacked configuration with respect to each other.
Each cell is connected to at least one adjacent cell. Each cell
includes first and second parting sheets, an internal finned
member, and at least one external finned member. The first parting
sheet includes opposing first and second surfaces, a first inlet
header portion, a first outlet header portion, a first internal
finned member portion and peripheral edges. The second parting
sheet is substantially superimposed by, is spaced apart from and is
coupled to the first parting sheet. The second parting sheet
includes opposing first and second surfaces, a second inlet header
portion, a second outlet header portion, a second internal finned
member portion and peripheral edges. The second surface of the
second parting sheet confronts the second surface of the first
parting sheet. At least a portion of the peripheral edges of the
first and second parting sheets are attached to each other. The
internal finned member is disposed between the second surfaces of
the first and second parting sheets. The internal finned member is
positioned at the first and second internal finned member portions
of the first and second parting sheets, respectively, and has a
leading edge positioned adjacent to the first and second inlet
header portion of the first and second parting sheets,
respectively, and a trailing edge positioned adjacent to the first
and second outlet header portion of the first and second parting
sheets, respectively. The at least one external finned member is
attached to at least one of the first surface of the first parting
sheet and the first surface of the second parting sheet. The
external finned member has a leading edge and a trailing edge. The
external finned member is positioned offset from the internal
finned member such that the leading edge of the external finned
member outwardly extends beyond the trailing edge of the internal
finned member.
[0018] The present invention also provides a heat exchange cell of
a heat exchanger for transferring heat between an external fluid
and an internal fluid. The heat exchange cell includes first and
second parting sheets, an internal finned member, at least one
external finned member, and inlet and outlet headers. The first
parting sheet includes opposing first and second surfaces, a first
inlet header portion, a first outlet header portion and a first
internal finned member portion. The second parting sheet is
substantially superimposed by, is spaced apart from and is coupled
to the first parting sheet. The second parting sheet includes
opposing first and second surfaces, a second inlet header portion,
a second outlet header portion, and a second internal finned member
portion. The second surface of the second parting sheet confronts
the second surface of the first parting sheet. The internal finned
member is disposed between the second surfaces of the first and
second parting sheets. The internal finned member has a leading
edge and a trailing edge. The at least one external finned member
is attached to at least one of the first surface of the first
parting sheet and the first surface of the second parting sheet.
The external finned member has a leading edge and a trailing edge.
The trailing edge of the internal finned member extends along the
juncture of the first and second outlet header portions to the
first and second internal finned portions of the first and second
parting sheets, respectively. The leading edge of the internal
finned member extends along the juncture of the first and second
inlet header portions to the first and second internal finned
portions of the first and second parting sheets, respectively. The
external finned member is positioned offset from the internal
finned member such that the leading edge of the external finned
member outwardly extends beyond the leading edge of the internal
finned member.
[0019] The foregoing and other aspects will become apparent from
the following detailed description of the invention when considered
in conjunction with the accompanying FIGS.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 shows an exploded view of an individual heat exchange
cell for a counterflow heat exchanger in accordance with preferred
embodiments of the present invention.
[0021] FIG. 2 shows a first plan view of the individual heat
exchange cell shown in FIG. 1.
[0022] FIG. 3 shows an exploded view of the individual heat
exchange cell of FIG. 1 after partial assembly thereof.
[0023] FIG. 4 shows an enlarged fragmentary view of an inlet header
of the individual heat exchange cell shown in FIG. 2.
[0024] FIG. 5 shows a side view of a counterflow heat exchanger
including a plurality of the individual heat exchange cells shown
in FIGS. 1-3.
[0025] FIG. 6 shows a perspective view of a counterflow heat
exchanger including a plurality of the heat exchange cells shown in
FIGS. 1-3, in accordance with one preferred embodiment of the
present invention.
[0026] FIG. 7 shows a partial cross-sectional view of the inlet
aperture taken along line 7-7 of FIG. 2, showing the raised
flanges.
[0027] FIG. 8 shows a partial cross-sectional view of an edge of
the individual heat exchanger element shown in FIG. 2, taken along
line 8-8, showing the details of a braze-reservoir.
[0028] FIG. 9 shows the flow of first and external fluids through
the heat exchanger of FIG. 6 in accordance with certain preferred
embodiments of the present invention.
[0029] FIG. 10 shows a perspective view of the heat exchange of
FIG. 6 after thermal loading whereby the structure flexes in
response to thermal forces.
[0030] FIG. 11 shows a cross-sectional view of the heat exchanger
shown in FIG. 9 taken along line XI-XI, before thermal loading.
[0031] FIG. 12 shows the heat exchanger of FIG. 11 after thermal
loading whereby the structure flexes in response to thermal
forces.
[0032] FIG. 13 shows a fragmentary top view of the heat exchanger
shown in FIG. 9.
[0033] FIG. 14A shows a front view of the heat exchanger shown in
FIG. 13 along line XIV-XIV when the heat exchanger is in an
undeflected "cold" state.
[0034] FIG. 14B shows a front view of the heat exchanger shown in
FIG. 13 along line XIV-XIV when the heat exchanger is in a
deflected "hot" state.
[0035] FIG. 15 shows an exploded view of an individual heat
exchange cell for a counterflow heat exchanger in accordance with
an embodiment of the present invention.
[0036] FIG. 16 is a sectional view an inlet manifold member, an
internal finned member and two external finned members of the heat
exchange cell of FIG. 15.
[0037] FIG. 17 is a sectional view an outlet header, the internal
finned member and the two external finned members of the heat
exchange cell of FIG. 15.
[0038] FIG. 18 is a graph illustrating the stiffness of the heat
exchange cell along the portion of the heat exchange cell
illustrated in FIG. 16
[0039] FIG. 19 shows an exploded view of an individual heat
exchange cell for a counterflow heat exchanger in accordance with
another preferred embodiment of the present invention.
[0040] FIG. 20 is a sectional view an outlet header, the internal
finned member and the two external finned members of the heat
exchange cell of FIG. 19.
[0041] FIG. 21 is a graph illustrating the stiffness of the heat
exchange cell along the portion of the heat exchange cell
illustrated in FIG. 20.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0042] FIG. 1 shows an exploded view of an individual heat exchange
cell 10 in accordance with certain preferred embodiments of the
present invention. Each heat exchange cell 10 includes a
self-contained pressure-tight structure which may be stacked atop
other substantially identical heat exchange cells to produce a
counterflow heat exchanger, such as the exchanger shown in FIG. 9
and described below. Each heat exchange cell 10 has all of the
features required for providing a complete counterflow heat
exchanger including inlet and exit manifolds and heat transfer fins
assembled into a single unit cell, as shown in FIG. 2.
[0043] The utilization of individual heat exchange cells overcomes
the following problems present in the prior art:
[0044] 1) Allows for the inspection, correction and/or rejection of
a small, manageable heat exchange cell rather than on a completed
heat exchanger comprising a matrix of permanently assembled layers,
thereby resulting in greater quality control and reduced scrap.
[0045] 2) Allows for quality-control testing of individual heat
exchange cells before the various layers are assembled together,
thereby avoiding the risk and technical difficulty of brazing
massive heat exchanger matrices.
[0046] 3) Allows for slip and movement between layers to
accommodate for thermal expansion and contraction, without the risk
of leakage.
[0047] 4) Allows for the rapid removal and replacement of defective
heat exchange is cells, as opposed to scrapping an entire heat
exchanger when a defective layer is discovered.
[0048] Referring to FIGS. 1 and 2, in certain preferred
embodiments, each individual heat exchange cell 10 preferably
includes a top plate 12 having a first surface 14, a second-surface
16 (FIG. 5) and one or more peripheral edges 18 defining outer
edge(s) of the top plate 12. The top plate 12 preferably includes
an inlet aperture 20A at one end thereof, an outlet aperture 22A at
the other end thereof and a substantially flat central region 24A
between the inlet and outlet apertures 20A and 22A. Each heat
exchange cell 10 also preferably includes a bottom plate 26 that
substantially mirrors the dimensions, size and shape of the top
plate 12. The bottom plate 26 preferably has a first surface 28
(FIG. 6), a second surface 30 and one or more peripheral edges 32
defining outer edge(s) of the bottom plate 12. The bottom plate 26
also preferably includes an inlet aperture 20B at one end thereof,
an outlet aperture 22B at the other end thereof and a substantially
flat central region 24B (FIG. 5) between the inlet and outlet
apertures 20B and 22B.
[0049] The heat exchange cell 10 preferably includes at least one
finned member attached thereto for transferring heat between two or
more fluids passing closely by one another. In one particular
embodiment, the heat exchange cell 10 preferably includes two
external finned members, a first one of the external finned members
34A attached to the first surface 14 of the top plate 12,
preferably within the substantially flat central region 24A
thereof; and a second one of the two external finned members 34B
attached to the first surface 28 of the bottom plate 26, preferably
within the substantially flat central region 24B thereof.
[0050] The heat exchange cell 10 is preferably assembled by
juxtaposing the second surfaces 16,30 of the top and bottom plates
12, 26 with one another so that the inlet apertures 20A, 20B and
the outlet apertures 22A, 22B of the top and bottom plates 12 and
26 are in substantial alignment. The inlet apertures 20A, 20B
include respective substantially S-shaped raised flange portions
36A and 36B terminating at interior edges bounding the inlet
apertures 20A, 20B. Similarly, the outlet apertures 22A, 22B
include respective substantially S-shaped raised flange portions
38A, 38B terminating at interior edges bounding the outlet
apertures 22A, 22B. In other words, the substantially S-shaped
raised flange portions of the attached top and bottom plates 12 and
26 diverge from one another at the interior edges thereof and are
joined at the outer peripheral edges of the plates. Thus, each
substantially S-shaped raised flange portion generally extends away
from the first surface of the plate associated therewith so that
the interior edge thereof lies above the first surface of the
plate. In preferred embodiments, the top and bottom plates 12, 26
including the respective substantially S-shaped raised flange
portions thereof are of substantially uniform thickness so that
temperature changes occurring at the flanges are substantially the
same as temperature changes occurring along the remainder of the
top and bottom plates 12, 26, whereby thermal strain produced
during operation of the heat exchanger is minimized.
[0051] The peripheral edges 18, 32 of the respective top and bottom
plates 12 and 26 are then attached to one another, whereby the
aligned inlet apertures 20A, 20B of the attached top and bottom
plates 12 and 26 provide an inlet manifold of the heat exchange
cell 10 and the aligned outlet apertures 22A, 228 of the attached
top and bottom plates provide an outlet manifold of the heat
exchange cell 10. The attached top and bottom plates 12, 26 define
a high pressure chamber 52 (FIG. 5) between the second surfaces
thereof so that a fluid may pass therethrough at a relatively
higher pressure than do fluids passing over the first surfaces of
the plates.
[0052] The heat exchange cell 10 also preferably includes an
internal finned member 40 disposed between and attached to the
second surfaces of the top and bottom plates 12, 26. The internal
finned member 40 is preferably brazed to the second surfaces 16, 30
of the top and bottom plates 12, 26. When the cell is assembled,
the internal finned member 33 is typically in substantial vertical
alignment with the two external finned members 34A, 34B, the two
external finned members also being in substantial vertical
alignment with one another.
[0053] Referring to FIG. 3, each heat exchange cell 10 is
preferably adapted for passing an internal fluid, such as a
combustible gas, through the internal finned member 40 in a first
flow direction designated 56 and for passing an external fluid,
such as an exhaust gas, through the two external finned members 34
in a second flow direction designated 54 that is substantially
counter to the first flow direction 54.
[0054] Referring to FIGS. 1-3, the internal finned member 33
attached to the second surfaces of the top and bottom plates 12 and
26 desirably includes an inlet end 42 for receiving the internal
fluid from the inlet manifold 20 and an outlet end 44 for
discharging the internal fluid to the outlet manifold 22. The heat
exchange cell 10 may also include an inlet manifold finned member
46 disposed in the high pressure chamber between the inlet manifold
20 and the inlet edge 42 of the internal finned member 33 and an
outlet manifold finned member 48 disposed in the high pressure
chamber between the outlet edge 44 of the internal finned member 33
and the outlet manifold 22. As shown in FIG. 3, the inlet and
outlet manifold finned members 46, 48 direct the internal fluid in
first lateral or cross-flow directions 58A, 58B and the internal
finned member 33 directs the external fluid in the direction
designated 56 that is substantially perpendicular to the first
lateral directions 58A, 58B.
[0055] FIG. 4 shows a fragmentary, close-up view of the inlet
manifold 20, inlet manifold finned member 46 and internal finned
member 33 of a preferred heat exchange cell 10. In this embodiment,
the inlet manifold finned member 46 includes a series of channels
50 which serve as conduits for passing the internal fluid from the
inlet manifold 20 to the first edge 42 of the internal finned
member 33. In preferred embodiments, each channel 50 is in fluid
communication with a plurality of channels 52A, 52B, 52C of the
internal finned members 33. Referring to FIG. 8, in certain
embodiments the inlet manifold fins 46 (or the outlet manifold
fins) may terminate at the portion of the top and bottom plates 12
and 26 where the plates diverge to form substantially S-shaped
raised flanges 36A, 36B. This termination configuration is shown in
solid font in FIG. 7. Alternatively, the inlet manifold fins may
extend beyond the portion of divergence of the plates 12, 26 in the
manner shown in FIG. 7 by dashed font designated 46.
[0056] Referring to FIGS. 5 and 6, in preferred embodiments, a heat
exchanger 60 is provided by assembling two or more heat exchange
cells 10 one atop the other with the adjacent interior edges of
adjacent heat exchange cells attached together for forming a
compliant bellows structure 62 capable of elastically absorbing
deflections produced during thermal loading so that the individual
heat exchange cells may move relative to one another. For example,
FIG. 5 shows a heat exchanger including stacked heat exchange cells
10A, 10B, 10C and 10D. Heat exchange cell 10A includes top plate
12A having substantially S-shaped raised flange portion 36A with
interior edge 64A and bottom plate 26A having substantially
S-shaped raised flange portion 36B with interior edge 64B. Heat
exchange 10B is substantially similar to heat exchange cell 10A and
also includes interior edges 64A and 64B. The heat exchange cells
10A and 10B are attached together solely through the adjacent
interior edges (e.g., such as by welding the interior edge 64A of
heat exchange cell 10B with the interior edge 64A of heat exchange
cell 10B). The portions of the substantially S-shaped raised
flanges 36 remote from the interior edges 64 are not attached to an
adjacent heat exchange cell. This allows the substantially S-shaped
raised flanges to flex in response to compression and tension
forces. The process is continued until the heat exchange cells
10A-10D are attached together through the adjacent interior
edges.
[0057] The external finned members 34 of adjacent heat exchange
cells 10 are not attached or bonded together so that the individual
heat exchange cells are free to move relative to one another during
heating up and cooling down of the heat exchanger. As mentioned
above, the welded interior edges of the substantially S-shaped
raised flanges form a compliant bellows structure capable of
elastically absorbing deflections produced during thermal loading
so that the individual heat exchange cells may move relative to one
another. The compliant nature of the bellows structure minimize
stresses and strains placed upon the heat exchanger structure.
[0058] In addition, prior art heat exchangers typically include gas
header fins adjacent the external finned members 34 attached to the
top and bottom plates. The gas header fins are typically provided
for 1) directing flow into the heat exchanger matrix; 2) providing
compressive strength to react pressure; and 3) providing a
continuous load path between the layers during assembly and
manufacturing. The present invention does not require such gas
header fins due, inter alia, to the fact that each individual cell
is pressure balanced (i.e., includes its own internal high pressure
chamber so that each individual heat exchange cell may function, if
necessary, as a complete heat exchanger). Thus, the absence of gas
header fins from the individual heat exchange cells of the present
invention provides numerous benefits including providing
flexibility to the cell that enables the cell to deflect
out-of-plane and thus respond to thermal gradients.
[0059] Referring to FIG. 9, during operation of one preferred
embodiment of the heat exchanger 60, the external fluid, such as a
heated exhaust gas, travels in the direction designated 54 and
through the external finned members 34 of the stacked heat exchange
cells 10. At the same time, the internal fluid, such as a
relatively cool compressor discharge air travels through the
compliant inlet manifold structure 62 in a downward direction
designated 66. Referring to FIG. 3, the internal fluid then passes
in succession though the inlet manifold finned member 58A, the
internal finned member 33 and the outlet manifold finned member
58B. At least some of the heat present in the external fluid is
transferred to the internal fluid as the heat is transferred from
the external finned members to the internal finned member.
Referring to FIG. 9, the internal fluid then passes from the outlet
manifold finned members of the respective cells 10 to the outlet
manifold structure 68 in the direction designated 70. The
temperature of the internal fluid discharged from the heat
exchanger 60 is typically higher than the temperature of the
internal fluid entering the heat exchanger. Referring to FIG. 10,
the compliant nature of the inlet and outlet manifolds and the
individual plates enables the cells of the heat exchanger to move
relative to one another during operation so as to minimize the
adverse affects that may result from thermal expansion and
contraction. During operation, there is no need to apply external
forces to the outside of each heat exchange cell 10 in order to
hold the cell together because, inter alia, the internal finned
member 33 is fully adhered to the top and bottom plates 12, 26
(which provides resistance against differential pressure load).
[0060] Referring to FIGS. 1, 2 and 13, in certain preferred
embodiments the first and second external finned members 34A and
51B of each heat exchange cell may include substantially aligned
leading edges 72A and 89B that are desirably adapted for receiving
the external fluid passing between the cell layers. The first and
second external finned members may also include trailing edges 74A
and 91B adapted for discharging the external fluid therefrom after
the external fluid has passed completely through the external
finned members. The substantially aligned leading edges 72A and 89B
of the first and second external finned members 34A and 51B are
desirably substantially remote from a leading peripheral edge 76 of
the heat exchange cell 10. In other words, Referring to FIG. 11,
there exists a space or gap 78 between the aligned leading edges
72A and 89B of the external finned members and the leading
peripheral edge 76 of the heat exchange cell 10. The space 78
enables the individual cells to move toward and away from one
another. Referring to FIG. 2, the substantially aligned leading
edges 72A and 89B of the first and second external finned members
34A and 51B may also be substantially offset from the aligned
outlet apertures 22 forming the flexible outlet manifold structure
68 for also enabling each cell to deflect toward and away from a
heat exchange cell adjacent thereto.
[0061] Referring to FIGS. 1, 2 and 13, in other preferred
embodiments, the trailing edges 74A and 91B of the first and second
external finned members 34A and 51B may also be in substantial
alignment with one another and substantially remote from a rear
peripheral edge 80 of the heat exchange cell 10. There preferably
exists a space or gap 82 between the trailing edge 74A of the
external finned member 34 and the rear peripheral edge 80 of the
cell for enabling each individual cell to deflect toward and away
from a heat exchange cell adjacent thereto. The substantially
aligned trailing edges 74A and 91B of the first and second external
finned members 34A and 51B are substantially offset from the
aligned inlet apertures 20 forming the flexible inlet manifold
structure 62 of the heat exchanger 60 for enabling each cell to
deflect toward and away from a heat exchange cell adjacent
thereto.
[0062] FIG. 11 shows a fragmentary cross-sectional view of the heat
exchanger shown in FIG. 9 before the bellows structures have flexed
and/or bowed in response to thermal forces. The various cell layers
are substantially parallel to one another because, inter alia, the
heat exchanger is not under thermal stress. The leading edges 72A
and 89B of the external finned members 34A and 51B are remote from
the leading peripheral edge 76 of the cell, thereby providing a gap
78 that extends between the adjacent cell layers. FIG. 12 shows a
fragmentary cross-sectional view of the heat exchanger of FIG. 9
after thermal loading whereby the heat exchanger flexes, bends
and/or deflects in response to thermal forces. The leading
peripheral edges 76 of the respective cell layers are able to move
toward one another because the gaps 78 provide room into which the
respective cell layers are able to move toward one another because
the gaps 78 provide room into which the respective cell layers may
move, thereby providing the heat exchanger with enhanced
flexibility.
[0063] FIG. 13 shows a top fragmentary view of the heat exchanger
60 shown in FIGS. 9 and 14. FIGS. 14A and 14B show a front view of
the heat exchanger 60 taken along line XIV-XIV of FIG. 13. FIG. 14A
shows the heat exchanger in an undeflected "cold" state, i.e.,
before the cell layers 10 have flexed and/or bowed in response to
thermal forces. As shown in FIG. 14A, the leading edges 76 of the
various cell layers 10 are substantially flat and parallel to one
another. FIG. 14B shows the heat exchanger in a deflected "hot"
state, i.e., after the leading edges 76 of the respective cell
layers 10 have flexed and/or bowed in response to thermal forces.
As shown in FIG. 14B, at least some of the leading edges 76 have
flexed and/or deflected away from cell layers 10 adjacent thereto.
As mentioned above, the leading peripheral edges 76 of the
respective cell layers 10 are able to deflect toward and away from
adjacent cell layers because the leading edges 76 are remote from
the leading edges 72 of the external finned members 74 for forming
form gaps 78 in which the respective cell layers 10 may move and/or
deflect, thereby providing the heat exchanger 60 with enhanced
flexibility.
[0064] In one preferred method of assembling individual heat
exchange cells 10, the top and bottom plates 12, 26 (also known as
parting plates) are formed from .010-.050 inch stainless or super
alloy steel sheet in roll form. The sheet is unrolled and then the
plates are formed by stamping and laser trimming. The external
finned members 34 and gas is turning fins 52 are formed from
.003-.010 inch rolled stainless or super alloy steel. The metal is
unrolled, the fins are folded and braze coating is sprayed onto one
side of the external finned member 34 and the gas turning fin 52.
The braze coated external finned member 34 and gas turning fin 52
are then laser trimmed and cleaned. Instead of applying a braze
coat to the external finned member 34 and gas turning fin 52, the
first surfaces 14, 28 of the respective top and bottom plates 12,
26 may be coated with the braze coating. The internal finned member
33 and the inlet and outlet manifold finned members 46, 48 are
formed from .003-.010 inch rolled stainless or super alloy steel.
The metal is unrolled, the fins are folded and braze coating is
sprayed onto both sides of the internal finned member 33 and the
inlet and outlet manifold finned members 46, 48. The braze coated
internal finned member 33 and inlet and outlet manifold finned
members 46, 48 are then laser trimmed and cleaned. Instead of
applying a braze coat to the internal finned member 33 and the
inlet and outlet manifold finned members 46, 48, both inside
surfaces of the top and bottom plates 12, 26 may be braze
coated.
[0065] The top and bottom plates 12, 26; the two external finned
members 34A, 34B; the internal finned member 33; and the inlet and
outlet manifold finned members 46, 48 are assembled to form an
individual heat exchange cell 10. The individual pieces are tack
welded to temporarily hold the pieces together. In addition, the
peripheral edge of the assembled individual heat exchange cell 10
may be laser welded.
[0066] One or more assembled individual heat exchange cells 10 are
then preferably placed into a braze cell where the individual cells
10 are heated to braze the coated surfaces to one another. Various
brazing jig components can be used to load the individual heat
exchange cells 10 to minimize any distortion of the cells 10 during
the brazing process. FIGS. 7 and 8 illustrate a preferred
embodiment of the top and bottom plates 12, 26, including a
reservoir 54 provided in top plate 12. This reservoir 54 holds
additional braze coating which will spread in the adjacent surfaces
of the interior of an individual heat exchange cell 10 during the
brazing process.
[0067] After brazing, each heat exchange cell 10 is pressurized to
check for any leaks caused by inadequate brazing. A plurality of
individual heat exchange cells 10 are then assembled into a partial
stack and the interior edges of the substantially S-shaped raised
flanges 36, 38 are welded together. These partial stacks are then
pressure tested again. A plurality of partial stacks are then
welded together to provide a heat exchanger. Transition pieces (not
shown) may be attached to outer individual heat exchange cells 10
to provide a place to connect the heat exchanger to the inlet and
outlet manifolds of the equipment the heat exchanger is a part
of.
[0068] FIG. 15 shows an exploded view of an individual heat
exchange cell 100 in accordance with a preferred embodiment of the
present invention. Each individual heat exchange cell 100
preferably includes a first parting sheet 102 having one or more
peripheral edges 117 defining outer edge(s) of the first parting
sheet 102. The first parting sheet 102 preferably includes an inlet
aperture 160A at one end thereof, an outlet aperture 162A at the
other end thereof and a substantially flat central region 164A
between the inlet and outlet apertures 160A and 162A. Each heat
exchange cell 100 also preferably includes a second parting sheet
104 that substantially mirrors the dimensions, size and shape of
the first parting sheet 102. The second parting sheet 104
preferably has one or more peripheral edges 166 defining outer
edge(s) of the second parting sheet 104. The second parting sheet
104 also preferably includes an inlet aperture 160B at one end
thereof, an outlet aperture 162B at the other end thereof and a
substantially flat central region 164B between the inlet and outlet
apertures 160B and 62B.
[0069] The heat exchange cell 100 preferably includes two external
finned members, a first external finned member 108 attached to the
first parting sheet 102 preferably within the substantially flat
central region 164 thereof; and a second external finned member 110
attached to the second parting sheet 104, preferably within the
substantially flat central region 164B thereof. The peripheral
edges 117, 166 of the respective first and second parting sheets
102, 104 are attached to one another, whereby the aligned inlet
apertures 160A, 160B of the attached first and second parting
sheets 102, 104 provide an inlet manifold 160 of the heat exchange
cell 100 and the aligned outlet apertures 162A, 162B of the
attached first and second parting sheets 102, 104 provide an outlet
manifold 162 of the heat exchange cell 100.
[0070] The heat exchange cell 100 also preferably includes an
internal finned member 106 disposed between and attached to the
first and second parting sheets 102, 104. When the cell is
assembled, the internal finned member 106 is typically in
substantial vertical alignment with the two external finned members
108, 110, the two external finned members 108, 110 also being in
substantial vertical alignment with one another.
[0071] The internal finned member 106 preferably includes a leading
edge 126 for receiving the internal fluid from the inlet manifold
160 and a trailing edge 128 for discharging the internal fluid to
an outlet manifold 162. The heat exchange cell 10 may also include
an inlet header 127 disposed in the high pressure chamber between
the inlet manifold 160 and the leading edge 126 of the internal
finned member 106 and an outlet header 129 disposed in the high
pressure chamber between the trailing edge 128 of the internal
finned member 106 and the outlet manifold 162. The inlet and outlet
headers 127, 129 direct the internal fluid in first lateral or
cross-flow directions and the internal finned member 106 directs
the external fluid in the direction that is substantially
perpendicular to the first lateral directions.
[0072] Heat exchange cell 100 is configured for transferring heat
between an external fluid and an internal fluid. In an exemplary
embodiment, heat exchange cell 100 is a counter-flow heat exchange
cell configured for enabling an internal fluid to pass through an
interior finned heat exchange section of heat exchange cell 100 in
a first direction and enable an external fluid to pass through
exterior finned heat exchange section of heat exchange cell 100 in
a direction generally opposite that of the internal fluid. In an
exemplary embodiment, heat exchange cell 100 is a cross-flow cell
wherein the internal fluid is directed along an inlet region of
heat exchange cell 100 in a second direction and then is redirected
in the first direction substantially perpendicular, or oblique, to
the second direction and along the flow path defined by the
interior finned section of heat exchange cell 100. Upon exiting the
interior finned sections of heat exchange cell 100 the flow of the
internal fluid is redirected again in a third direction which is
substantially perpendicular, or oblique, to the first
direction.
[0073] FIGS. 16 and 18 illustrate sectional views of an individual
cross-flow heat exchange cell 100 in accordance with an exemplary
embodiment of the present invention. FIG. 16 illustrates the inlet
region of heat exchange cell 100 for directing the flow of an
internal fluid. FIG. 18 illustrates the outlet region of heat
exchange cell 100 for directing the flow of the internal fluid.
Heat exchange cell 100 includes the first and second parting sheets
102, 104, the internal finned member 106, and the first and second
external finned members 108, 110. First and second parting sheets
102, 104 are generally flat plates each having opposing first and
second surfaces 116, 118, 120, 122 and peripheral edges. Second
surface 120 of second parting sheet 104 confronts or faces second
surface 118 of first parting sheet 102. A portion of the peripheral
edges of first and second members 102, 104 are connected to each
other to form a chamber 124. First and second parting sheets 102;
104 are connected to and retain internal finned member 106 between
second surfaces 118, 120 and within chamber 124. First and second
parting sheets 102, 104, between second surfaces 118, 120, also
connect to the inlet header 127 and to the outlet header 129. First
surface 116 of first parting sheet 102 connects to first external
finned member 108 and first surface 122 of second parting sheet 104
connects to second external finned member 110. First and second
parting sheets 102, 104 include inlet and outlet apertures 160, 162
(see FIG. 15) and are configured to define a flow path for an
internal fluid.
[0074] Internal finned member 106 is a segment of fin stock.
Internal finned member 106 includes a leading edge 126 and a
trailing edge 128. Internal finned member 106 is connected to and
between second surfaces 118, 120 of first and second parting sheets
102, 104. In an exemplary embodiment, internal finned member 106 is
brazed to second surfaces 118, 120 of first and second parting
sheets 102, 104. The connection of internal finned member 106 to
first and second parting sheets 102, 104 at internal finned portion
138, 140 of first and second parting sheets. Internal finned member
106 is configured to create passages of a requisite hydraulic
diameter for directing the flow of an internal fluid, to increase
heat transfer area of heat exchange cell 100, and to provide
structural support to heat exchange cell 100.
[0075] First and second external finned members 108, 110 are
segments of fin stock. First and second external finned members
108, 110 include first and second trailing edges 130, 132 and first
and second leading edges 134, 136. First external finned member 108
is attached to first surface 116 of first parting sheet 102 and
second external finned member 110 is attached to first surface 122
of second parting sheet 104. First and second external finned
members 108, 110 generally have the same plan dimensions as
internal finned member 106. Internal and external finned members
106, 108, 110 are separated by first and second parting sheets 102,
104 and are stacked with respect to one another with leading edge
126 and trailing edges 130, 132 in general alignment with one
another, and trailing edges 128 and leading edges 134, 136 in
general alignment with one another. First and second external
finned members 108, 110 are configured to create passages of a
requisite hydraulic diameter for directing the flow of an external
fluid, to increase heat transfer area of heat exchange cell 100,
and to provide structural support to heat exchange cell 100. In an
exemplary embodiment, internal finned member 106 is configured to
direct the flow of an internal fluid generally along a first plane
in a first direction and each external finned member 108, 110 is
configured to direct the flow of an external fluid in a direction
opposite the first direction. In alternative exemplary embodiments,
heat exchange cell 100 can include a single external finned member
connected to one of first surface 114 of first parting sheet 102
and first surface 120 of second parting sheet 104.
[0076] Referring to FIG. 16, the inlet header 127 is a finned
cross-flow header. The inlet header 127 is positioned between and
connected to first and second parting sheets 102, 104. Inlet header
127 is comprised of more coarsely configured fins than internal and
external finned members 106, 108, 110. The inlet header 127 is
positioned adjacent to the internal finned member 106 at leading
edge 126. The inlet header 127 is configured to deliver an internal
fluid from inlet aperture 160 (see FIG. 15) to internal finned
member 106. The inlet header 127 directs the flow of an internal
fluid generally along the first plane in a second direction that is
substantially perpendicular, or oblique, to the direction of
internal fluid flow through internal finned member 106, referred to
as the first direction.
[0077] Referring to FIG. 18, the outlet header 129 is a finned
cross-flow header. The outlet header 129 is positioned between and
connected to first and second parting sheets 102, 104. Outlet
manifold finned member 129 is comprised of more coarsely configured
fins than internal and external finned members 106, 108, 110.
Outlet header 129 is positioned adjacent to the internal finned
member 106 at trailing edge 128. The outlet header 129 is
configured to collect an internal fluid from internal finned member
106 and deliver the flow to outlet aperture 162 (see FIG. 15). The
outlet header 129 directs the flow of an internal fluid generally
along the first plane in a third direction that is substantially
perpendicular, or oblique, to the first direction.
[0078] FIGS. 16 and 18 further illustrate the transition of inlet
and outlet headers 127, 128 to the internal finned portions 106,
otherwise referred to as a transition region 144. FIG. 17
illustrates the relative stiffness of heat exchange cell 100 along
the section of heat exchange cell 100 illustrated in FIG. 16. As
illustrated in FIG. 17, the exemplary embodiment of heat exchange
cell 100 of FIG. 16 includes a sharp drop in stiffness at the
connection of internal and external finned portions 106, 108, 110
of heat exchange cell 100 to transition region 144, and an sharp
increase in stiffness from transition region 144 to the outlet
header 129.
[0079] FIG. 19 shows an exploded view of an individual heat
exchange cell 200 in accordance with a preferred embodiment of the
present invention. Each individual heat exchange cell 200
preferably includes a first parting sheet 202 having one or more
peripheral edges 217 defining outer edge(s) of the first parting
sheet 202. The first parting sheet 202 preferably includes an inlet
aperture 260A at one end thereof, an outlet aperture 262A at the
other end thereof and a substantially flat central region 264A
between the inlet and outlet apertures 260A and 262A. Each heat
exchange cell 200 also preferably includes a second parting sheet
204 that substantially mirrors the dimensions, size and shape of
the first parting sheet 202. The second parting sheet 204
preferably has one or more peripheral edges 266 defining outer
edge(s) of the second parting sheet 204. The second parting sheet
204 also preferably includes an inlet aperture 260B at one end
thereof, an outlet aperture 262B at the other end thereof and a
substantially flat central region 264B between the inlet and outlet
apertures 260B and 262B.
[0080] The heat exchange cell 200 preferably includes two external
finned members, a first external finned member 208 attached to the
first parting sheet 202, preferably within the substantially flat
central region 264 thereof; and a second external finned member 210
attached to the second parting sheet 204, preferably within the
substantially flat central region 264B thereof. The peripheral
edges 217, 266 of the respective first and second parting sheets
202, 204 are attached to one another, whereby the aligned inlet
apertures 260A, 260B of the attached first and second parting
sheets 202, 204 provide an inlet manifold 260 of the heat exchange
cell 200 and the aligned outlet apertures 262A, 262B of the
attached first and second parting sheets 202, 104 provide an outlet
manifold 262 of the heat exchange cell 200.
[0081] The heat exchange cell 200 also preferably includes an
internal finned member 206 disposed between and attached to the
first and second parting sheets 202, 204. The two external finned
members 208, 210 also being in substantial vertical alignment with
one another.
[0082] The internal finned member 206 attached preferably includes
a leading edge 226 for receiving the internal fluid from the inlet
manifold 260 and a trailing edge 228 for discharging the internal
fluid to an outlet manifold 262. The heat exchange cell 10 may also
include an inlet header 227 disposed in the high pressure chamber
between the inlet manifold 260 and the leading edge 226 of the
internal finned member 206 and an outlet header 229 disposed in the
high pressure chamber between the trailing edge 228 of the internal
finned member 206 and the outlet manifold 262.
[0083] Heat exchange cell 200 is configured for transferring heat
between an external fluid and an internal fluid. In an exemplary
embodiment, heat exchange cell 200 is a counter-flow heat exchange
cell configured for enabling an internal fluid to pass through an
interior finned heat exchange section of heat exchange cell 200 in
a first direction and enable an external fluid to pass through
exterior finned heat exchange section of heat exchange cell 200 in
a direction generally opposite that of the internal fluid. In an
exemplary embodiment, heat exchange cell 200 is a cross-flow cell
wherein the internal fluid is directed along an inlet region of
heat exchange cell 200 in a second direction and then is redirected
in the first direction substantially perpendicular, or oblique, to
the second direction and along the flow path defined by the
interior finned section of heat exchange cell 200. Upon exiting the
interior finned sections of heat exchange cell 200 the flow of the
internal fluid is redirected again in a third direction which is
substantially perpendicular, or oblique, to the first
direction.
[0084] FIG. 20 illustrates a sectional view of the cross-flow heat
exchange cell 200 in accordance with an alternative exemplary
embodiment of the present invention. FIG. 20 illustrates the outlet
region of heat exchange cell 200 for directing the flow of the
internal fluid. Heat exchange cell 200 includes first and second
parting sheets 202, 204, the internal finned member 206, and first
and second external finned members 208, 210. First and second
parting sheets 202, 204 are generally flat plates each having
opposing first and second surfaces 216, 218, 220, 222 and
peripheral edges. Second surface 220 of second parting sheet 204
confronts or faces second surface 218 of first parting sheet 202. A
portion of the peripheral edges of first and second members 202,
204 are connected to each other to form a chamber 224. First and
second parting sheets 202, 204 are connected to and retain internal
finned member 206 between second surfaces 218, 220 and within
chamber 224. First and second parting sheets 202, 204, between
second surfaces 218, 220, also connect to the inlet and outlet
header 227, 229.
[0085] First surface 216 of first parting sheet 202 connects to
first external finned member 208 and first surface 222 of second
parting sheet 204 connects to second external finned member 210.
First and second parting sheets include inlet and outlet apertures
260, 262 (see FIG. 19) and are configured to define a flow path for
an internal fluid. First and second parting sheets 202, 204
therefore each include an internal finned member portion connected
to internal finned member 206. First surface 216 of first parting
sheet 202 further connects to first external finned member 208 and
first surface 222 of second parting sheet 204 connects to second
external finned member 210. In an alternative exemplary embodiment,
the first and second parting sheets each include an internal finned
member portion which connects to an inlet header sheet portion and
an outlet header sheet portion, respectively. The trailing edges of
the internal finned member extend along the juncture of the first
and second outlet header sheet portions to the internal finned
member portion of the first and second parting sheets.
[0086] Internal finned member 206 is a segment of fin stock.
Internal finned member 206 includes a leading edge 226 (see FIG.
19) and a trailing edge 228. Internal finned member 206 is
connected to and is disposed between second surfaces 218, 220 of
first and second parting sheets 202, 204. In an exemplary
embodiment, internal finned member 206 is brazed to second surfaces
218, 220 of first and second parting sheets 202, 204. The
connection of internal finned member 206 to first and second
parting sheets 202, 204 at an internal finned portion 238, 240 of
first and second parting sheets 202, 204. Internal finned member
206 is configured to create passages of a requisite hydraulic
diameter for directing the flow of an internal fluid, to increase
heat transfer area of heat exchange cell 200, and to provide
structural support to heat exchange cell 200. In an exemplary
embodiment, internal finned member 206 includes convolutions.
[0087] First and second external finned members 208, 210 are
segments of fin stock. First and second external finned members
208, 220 include first and second leading edges 230, 232 and first
and second trailing edges 234, 236. First external finned member
208 is attached to first surface 216 of first parting sheet 202 and
second external finned member 210 is attached to first surface 222
of second parting sheet 204. First and second external finned
members 208, 210 are configured to create passages of a requisite
hydraulic diameter for directing the flow of an external fluid, to
increase heat transfer area of heat exchange cell 200, and to
provide structural support to heat exchange cell 200. In an
exemplary embodiment, internal finned member 206 is configured to
direct the flow of an internal fluid generally along a first plane
in a first direction and each external finned member 208, 210 is
configured to direct the flow of an external fluid in a direction
opposite the first direction. In alternative exemplary embodiments,
heat exchange cell 200 can include a single external finned member
connected to one of first surface 216 of first parting sheet 202
and first surface 222 of second parting sheet 204. In an exemplary
embodiment, first and second external finned members 208, 210
further include convolutions.
[0088] The interface between a counter-flow matrix (internal and
external finned members separated by parting sheets of a heat
exchange cell of a heat exchanger) and cross-flow headers of a
plate-fin heat exchanger can be susceptible to damage due to
discontinuities of stiffness and thermal response. During transient
thermal operation of the heat exchanger, strain accumulates in the
parting sheets separating two heat transfer streams, adjacent to
the open ends of the counter-flow fin segments. A global thermal
deflection is created in the heat exchange matrix, while the
cross-flow headers, experiencing little heat transfer, are strained
through connection with the parting sheets which extend from the
matrix and connect the cross-flow headers to the heat exchange
matrix. Along the interface between the matrix and the cross-flow
headers there is also a local thermal gradient created by the
difference in heat transfer rate between the matrix and the
cross-flow headers. The resulting difference in transient
temperature, and the attendant thermal strain, can be exacerbated
by the difference in stiffness between the matrix, the cross-flow
headers and the interface thereof. Strain accumulates in the softer
cross-flow region where it may cause damage.
[0089] As best illustrated in FIG. 20, internal finned member 206
is positioned offset from first and second external finned members
208, 210, such that leading edges 234, 236 of first and second
external finned members 208, 210 outwardly extend with respect to
internal finned member 206 and partially cover a portion of the
outlet header 229. Leading edges 234, 236 remain in general
alignment with one another and in an offset alignment with trailing
edge 228 of internal finned member 206.
[0090] The outlet header 229 is a cross-flow, finned header. In an
exemplary embodiment, the outlet header 229 is positioned between
and is connected to first and second parting sheets 202, 204. The
outlet header 229 is comprised of more coarsely configured fins
than internal and external finned members 206, 208, 210. The outlet
header 229 is positioned adjacent to internal finned member 206 at
trailing edge 228. The outlet header 229 is configured to collect
an internal fluid from internal finned member 206 and deliver the
flow to outlet aperture 262. The outlet header 229 directs the flow
of an internal fluid generally along the first plane in a third
direction that is substantially perpendicular to the first
direction.
[0091] FIG. 20 further illustrates the transition of the outlet
header 229 to the internal finned member 206, otherwise referred to
as transition region 244. FIG. 21 illustrates the relative
stiffness heat exchange cell 200 along the section of heat exchange
cell 200 illustrated in FIG. 20. FIG. 21 illustrates that the
exemplary embodiment of heat exchange cell 200, including the
offset configuration of internal finned member 206 with respect to
external finned members 208, 210, significantly increases the
stiffness of transition region 244. The exemplary embodiment of
FIG. 20, reduces damaging strain accumulation by creating
transition zone 244 including the offset positioning of first and
second external finned members 208, 210 with internal finned member
206 separated by first and second parting sheets 202, 204.
Transition zone 244 includes at least two significant
characteristics over a non-offset configuration. First transition
zone 244 reduces the rate of heat transfer into first and second
parting sheets 202, 204, and second, the structural stiffness of
transition zone 244 is significantly increased. These
characteristics enable heat exchange cell 200 to exhibit lower
thermal strain in operation and therefore, increase the fatigue
life of heat exchange cell 200.
[0092] The above disclosure describes only certain preferred
embodiments of a heat exchanger and is not intended to limit the
scope of the present invention to the exact construction and
operation shown and described herein. The foregoing is considered
to merely illustrate certain principles of the invention. Thus, it
should be evident to those skilled in the art that numerous
modifications and changes may be made to the embodiments shown
herein while remaining within the scope of the present invention as
described and claimed.
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