U.S. patent application number 11/232511 was filed with the patent office on 2006-03-23 for heat exchanger with compound plates.
This patent application is currently assigned to Centrax Limited. Invention is credited to Richard Henry Howard Barr.
Application Number | 20060060335 11/232511 |
Document ID | / |
Family ID | 33397154 |
Filed Date | 2006-03-23 |
United States Patent
Application |
20060060335 |
Kind Code |
A1 |
Howard Barr; Richard Henry |
March 23, 2006 |
Heat exchanger with compound plates
Abstract
A heat exchanger for donating heat from one fluid stream to
another fluid stream, comprising a plurality of compound heat
exchanger plates, each plate having a corrugated heat exchange
portion and a header portion which is not corrugated, the heat
exchange portion being a separate component from the header
portion, and being joined permanently to the header portion,
respective plates being joined together to form heat exchanger
cells. A heat exchanger plate may be formed in a method having the
following steps: (a) forming a heat exchange portion, which is of
corrugated cross section; (b) forming a header portion, which is
not corrugated; and (c) joining the header portion permanently to
the heat exchange portion to form a compound plate.
Inventors: |
Howard Barr; Richard Henry;
(Devon, GB) |
Correspondence
Address: |
MACMILLAN SOBANSKI & TODD, LLC;ONE MARITIME PLAZA FOURTH FLOOR
720 WATER STREET
TOLEDO
OH
43604-1619
US
|
Assignee: |
Centrax Limited
|
Family ID: |
33397154 |
Appl. No.: |
11/232511 |
Filed: |
September 22, 2005 |
Current U.S.
Class: |
165/153 |
Current CPC
Class: |
F28D 1/0333 20130101;
F28F 9/0221 20130101 |
Class at
Publication: |
165/153 |
International
Class: |
F28D 1/02 20060101
F28D001/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 23, 2004 |
GB |
0421205.6 |
Claims
1. A heat exchanger, for donating heat from one fluid stream to
another fluid stream, comprising a plurality of compound heat
exchanger plates, each plate having a corrugated heat exchange
portion and a header portion which is not corrugated, the heat
exchange portion being a separate component from the header
portion, and being joined to the header portion.
2. A heat exchanger as claimed in claim 1, in which respective
pairs of compound plates are sealed to one another at their edges
to define respective heat exchanger cells, respective cells being
joined together by holes, formed in the header portion of the
compound plates and sealed around their edges, such holes providing
fluid inlets and/or outlets to each cell.
3. A heat exchanger as claimed in claim 1, in which the header
portion is substantially planar.
4. A heat exchanger as claimed in claim 1, in which the material
thickness of the header portion is greater than the material
thickness of the corrugated heat exchange portion.
5. A heat exchanger as claimed in claim 1, in which the portions of
the compound plates are joined together by welding.
6. A heat exchanger as claimed in claim 1, in which the portions of
the compound plates are joined together by seam welding.
7. A heat exchanger as claimed in clam 1, in which the corrugations
at an end of the heat exchange portion are crushed to the center
line of the heat exchange portion, forming a planar surface to
which the header portion is joined.
8. A heat exchanger as claimed in claim 1, in which one side of the
header portion has a plurality of projections.
9. A heat exchanger as claimed in claim 8, in which the projections
are ribs.
10. A heat exchanger as claimed in claim 8, in which the
projections are so arranged as to constitute flow guides.
11. A heat exchanger as claimed in claim 1, in which each compound
plate has two header portions, disposed at opposite ends of a heat
exchange portion.
12. A heat exchanger as claimed in claim 11, in which the
corrugations of the heat exchange portion are pressed around their
remaining edges, and respective pairs of compound plates are welded
or otherwise fixed around their perimeters to form the said matrix
of heat exchanger cells.
13. A heat exchanger as claimed in claim 1, in which the fluid
inlet hole into a respective cell is provided at one end of the
matrix and the fluid outlet hole from the said cell is provided at
the opposite end of the matrix.
14. A heat exchanger as claimed in claim 1, in which the holes in
the cells at one end of the matrix are staggered relative to the
holes in the cells at the other end of the matrix.
15. A heat exchanger as claimed in claim 1, in which the holes are
elongated in a direction parallel to the corrugations.
16. A heat exchanger as claimed in claim 1, in which the inlet
holes are welded or otherwise fixed around their perimeters and/or
the outlet holes are welded or otherwise fixed around their
perimeters to join together adjacent cells.
17. A heat exchanger as claimed in claim 1, in which heat is
extracted from a first gas stream at a first temperature and
donated to a second gas stream at a second temperature lower than
the first temperature by heat conduction through the said heat
exchanger plates.
18. A heat exchanger as claimed in claim 17, in which the two gas
streams flow in a substantially counter direction along the
corrugations of the matrix.
19. A heat exchanger as claimed in claim 18, in which the second
gas stream enters through the fluid inlets and leaves through the
fluid outlets respectively and the first gas stream passes in
between adjacent cells in a counter flow direction.
20. A heat exchanger as claimed in claim 17, in which the first gas
stream comprises the exhaust gases of a gas turbine and the second
gas stream comprises the compressed air of the said gas turbine
prior to its entering the combustion chamber of said turbine.
21. A heat exchanger as claimed in claim 1, in which the cells are
substantially flat.
22. A heat exchanger as claimed in claim 1, in which the cells are
curved.
23. A heat exchanger as claimed in claim 1, in which the matrix is
made from a single spirally wound cell.
24. A heat exchanger as claimed in claim 1, in which the
corrugations of the heat exchange portions of the compound plates
follow an oscillating path, so that the corrugations define a wave
pattern when viewed in a direction normal to the surface of the
plate.
25. A heat exchanger as claimed in claim 24, in which the wave
pattern of plates in adjacent cells criss-crosses thus allowing
greater turbulence in the gas streams and consequently greater heat
transfer.
26. A method of forming a heat exchanger plate comprising the steps
of: (a) forming a heat exchange portion, which is of corrugated
cross section; (b) forming a header portion, which is not
corrugated; (c) joining the header portion to the heat exchange
portion to form a compound plate.
27. A method as claimed in claim 26, wherein the step (c) comprises
crushing the corrugations at an end of the heat exchange portion to
the center line of the heat exchange portion, forming a planar
surface to which the header portion is joined.
28. A method as claimed in claim 26, wherein the step (b) further
comprises forming a second header portion.
29. A method as claimed in claim 28, wherein the step (c) comprises
joining a header portion to opposite ends of the heat exchange
portion.
30. A method as claimed in claim 26, wherein the portions of the
plates are joined together by welding.
31. A method as claimed in claim 26, wherein the portions of the
plates are joined together by seam welding.
32. A method as claimed in claim 26, further comprising the step of
forming a plurality of holes in the header portion or portions.
33. A method as claimed in claim 26, further comprising the step of
forming a plurality of projections on the header portion or
portions.
34. A method as claimed in claim 33, wherein the projections are
formed in the shape of ribs.
35. A method as claimed in claim 34, wherein the ribs are formed as
flow guides, such that fluid flowing past the plate occupies
substantially the full extent of the heat exchange portion.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to a heat exchanger with compound
heat exchanger plates.
[0002] Heat exchangers are used in gas turbine engines as a means
of increasing efficiency by extracting heat from the exhaust gas
and donating this heat to the compressed air leaving the compressor
prior to its entering the combustion chamber. Conventional heat
exchangers are of two main types, firstly the rotating disc type,
commonly known as the regenerator, and secondly the static plate
type, commonly known as the recuperator, to which this invention is
directed.
[0003] Such heat exchangers have to withstand the considerable
temperature experienced by the exhaust gases, which might be up to
700.degree. C., and the high pressure of the compressed air, which
might be up to eight times atmospheric pressure.
[0004] The present invention seeks to provide a heat exchanger
which is compact, cheap to manufacture and technically
reliable.
SUMMARY OF THE INVENTION
[0005] According to a first aspect of the present invention, there
is provided a heat exchanger, for donating heat from one fluid
stream to another fluid stream, comprising a plurality of compound
heat exchanger plates, each plate having a corrugated heat exchange
portion and a header portion which is not corrugated, the heat
exchange portion being a separate component from the header
portion, and being joined directly and/or permanently to the header
portion.
[0006] The term "joined permanently" as it is used in this
specification means joined by welding, brazing, adhesive, riveting
or by any other physical interconnection, other than releasable
fasteners.
[0007] In accordance with a preferred embodiment of the present
invention, respective pairs of compound plates are sealed to one
another at their edges to define respective heat exchanger cells,
respective cells being joined together by holes, formed in the
header portion of the compound plates and sealed around their
edges, such holes providing fluid inlets and/or outlets to each
cell.
[0008] Preferably, the header portion of each compound plate is
substantially planar. Preferably, the material thickness of the
header portion is greater than the material thickness of the
corrugated heat exchange portion.
[0009] The corrugations at an end of the heat exchange portion are
preferably crushed to the center line of the heat exchange portion,
forming a planar surface to which the header portion may be joined.
Preferably, the portions of the compound plates are joined together
by welding, which may be seam welding.
[0010] Preferably, each compound plate has two header portions,
disposed at opposite ends of a heat exchange portion. Preferably,
only one side of each header portion has a plurality of
projections. In a preferred embodiment, the projections comprise
ribs, which are so arranged as to constitute flow guides, such that
fluid flowing in the cells occupies substantially the full extent
of the cells.
[0011] If the projections are formed on one side only of each
header portion, the surface of the header portion without
projections presents no obstruction to the free flow of the fluid
stream (preferably high pressure gas) which passes over that header
portion, so that the fluid stream can spread out from the inlet
holes over the full extent of the heat exchanger portion.
[0012] Preferably, the corrugations of the heat exchange portion
are pressed around the remaining edges of the heat exchange
portion, and respective pairs of compound plates are welded or
otherwise fixed around their perimeters to form the said matrix of
heat exchanger cells.
[0013] The fluid inlet hole into a respective cell of the heat
exchanger may be provided at one end of the matrix and the fluid
outlet hole from the said cell is preferably provided at the
opposite end of the matrix. The holes in the cells at one end of
the matrix may be staggered relative to the holes in the cells at
the other end of the matrix in order to equalize flow distribution.
Preferably, the holes are elongated in a direction parallel to the
corrugations.
[0014] Preferably, the inlet holes are welded or otherwise fixed
around their perimeters and the outlet holes are preferably also
welded or otherwise fixed around their perimeters to join together
adjacent cells. The holes in the cells at the extremity of the
matrix may be welded or otherwise fixed to a support structure
within which the two streams of gas are separated and directed.
[0015] In accordance with the preferred embodiment of the
invention, heat is extracted from a first gas stream at a first
temperature and donated to a second gas stream at a second
temperature lower than the first temperature by heat conduction
through the said heat exchanger plates. The two gas streams
preferably flow in a substantially counter direction along the
corrugations of the matrix. Preferably, the second gas stream
enters through the fluid inlets, spreads out across the
unobstructed header portion to occupy substantially the full extent
of the heat exchange portion and leaves through the fluid outlets
respectively, and the first gas stream spreads out, directed by the
flow guides, and passes in between adjacent cells in a counter flow
direction.
[0016] Preferably, the first gas stream comprises the exhaust gases
of a gas turbine and the second gas stream comprises the compressed
air of the said gas turbine prior to its entering the combustion
chamber of said turbine.
[0017] The cells of the heat exchanger matrix may be substantially
flat. Alternatively, the cells of the heat exchanger matrix may be
curved, and may be arranged together to form an annulus.
[0018] Preferably, the corrugations of the heat exchange portions
of the compound plates follow an oscillating path, so that the
corrugations define a wave pattern when viewed in a direction
normal to the surface of the plate. The compound plates may be
arranged such that the wave pattern of plates in adjacent cells
criss-crosses, thus allowing greater turbulence in the gas stream
and consequently greater heat transfer. Additionally,
criss-crossing the wave pattern of adjacent plates avoids the
possibility of plates interlocking and provides improved support
against pressure forces.
[0019] A particular advantage of the compound plates of the present
invention is that the header portions, being of a greater
thickness, can exhibit a greater stiffness than the corrugated heat
exchange portions. The stiffer header portions require a reduced
number of projections to support them against pressure differences
between the two gas streams when compared with conventional heat
exchanger plates. The reduced number of projections leads to a
reduced pressure drop across each heat exchanger cell and hence
greater efficiency for the heat exchanger.
[0020] According to another aspect of the present invention, there
is provided a method of forming a heat exchanger plate comprising
the steps of: (a) forming a heat exchange portion, which is of
corrugated cross section; (b) forming a header portion, which is
not corrugated; and (c) joining the header portion directly and/or
permanently to the heat exchange portion to form a compound plate.
Preferably, the step (c) comprises crushing the corrugations at an
end of the heat exchange portion to the center line of the heat
exchange portion, forming a planar surface to which the header
portion may be joined.
[0021] Preferably, the method further comprises forming a second
header portion and joining a header portion to opposite ends of the
heat exchange portion.
[0022] Preferably, the portions of the plates are joined together
by welding, which may be seam welding.
[0023] Preferably, the method further comprises the step of forming
holes through the header portion or portions. The method may also
comprise the step of forming projections on the header portion or
portions. The projections may be formed in the shape of ribs and
may be so formed as to act as flow guides, such that the fluid
flowing in the cells occupies substantially the full extent of the
cells.
[0024] Various objects and advantages of this invention will become
apparent to those skilled in the art from the following detailed
description of the preferred embodiment, when read in light of the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 is a perspective view of a heat exchanger plate.
[0026] FIG. 2 is an exploded view of the plate of FIG. 1.
[0027] FIG. 3 is a plan view of a heat exchanger cell.
[0028] FIG. 4a is an end view of the cell of FIG. 3.
[0029] FIG. 4b is a sectional view along the line XX of FIG. 3.
[0030] FIG. 5a is an end view of two of the cells of FIG. 3.
[0031] FIG. 5b is a sectional view of the cells of FIG. 5a.
[0032] FIG. 6 is a perspective view of a heat exchanger matrix
showing an alternative embodiment of inlet and outlet ports.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0033] Referring to FIG. 1, a compound heat exchanger plate 2
comprises a central heat exchange portion 4 and two header portions
6. The heat exchange portion 4 is corrugated, the corrugations
following an oscillating path so that they define a wave pattern
when viewed in a direction normal to the surface of the plate. The
corrugations at opposite ends 8 of the heat exchange portion 4 are
crushed to the centerline of the heat exchange portion so as to
present a planar surface. The header portions 6 are substantially
planar and are formed from a material of greater thickness than
that of the heat exchange portion 4. The header portions 6 thus
exhibit a greater stiffness than the heat exchange portion 4. The
header portions 6 are sealed to the crushed edges 8 of the heat
exchange portion 4 by welds 10, which are preferably seam
welds.
[0034] A plurality of holes 12 extend through the header portions 6
to permit the passage of fluid. The holes 12 are elongated in a
direction parallel to the corrugations. Holes 12 in opposite header
portions 6a and 6b are staggered relative to each other such that
no one hole is directly opposite a corresponding hole. A plurality
of projections 14 are formed on one side of the header portions 6
in the shape of ribs. At least one rib 14 is disposed on either
side of each hole 12, extending in a direction substantially
parallel to the corrugations of the heat exchange portion 4. Those
ribs 14a which are disposed adjacent one of the holes 12 have a
slight curvature, following the shape of the adjacent hole. In use,
ribs 14 act as both support for the plate 2 and as flow guides,
directing fluid passing over the plate into the corrugated heat
exchange portion 4.
[0035] With reference to FIG. 2, the compound plate 2 may be
assembled by first stamping out a metal sheet to form a corrugated
heat exchange portion 4, having oscillating corrugations which form
a wave pattern when viewed from a direction normal to the side of
the heat exchange portion. Opposite edges 8 of the heat exchange
portion 4 are then crushed to the center line of the corrugations
so as to provide a planar surface for attachment to header
portions. Two substantially planar header portions 6 are then
stamped out or otherwise formed from a material of greater
thickness than that used to form the heat exchange portion 4. In
the illustrated embodiment, projections are formed on one side of
the header plates 6 in the form of ribs 14 and depressions 15,
which may later be cut away to form holes 12. The ribs 14 are
formed so as to act as flow guides, such that in use, they will
direct fluid passing over the compound plate to occupy
substantially the full extent of the heat exchange portion. The
header portions 6 are then welded, preferably by seam welding, to
the crushed end portions 8 of the heat exchange portion 4.
[0036] With reference to FIGS. 3, 4a and 4b, a heat exchanger cell
16 comprises a pair of compound plates 2. The plates 2 are welded
together or otherwise sealed around their peripheries 20 to form
the cell 16. The free edges 18 of the heat exchange portions 4 of
the two plates 2 are crushed to the level of the header portions 6,
thus presenting planar surfaces for attachment to the adjacent
plate.
[0037] Referring to FIG. 6, a heat exchanger matrix 30 comprises a
plurality of heat exchanger cells 16 which are stacked one on top
the other. The respective heat exchanger cells are welded or
otherwise fixed together around the perimeter 24 of each hole 12 as
shown in FIGS. 5a and 5b. Each set of welded together holes 12
comprises an inlet port 22 or an outlet port 24 which is in fluid
communication with the interior of each of the cells 16.
[0038] In the illustrated embodiment, the heat exchanger matrix 30
comprises a recuperator for use in a gas turbine engine. Cold high
pressure air C from the compressor of the gas turbine engine is
directed into the inlet ports 22 by means of a manifold (not
shown). From the inlet ports, the cold high pressure air C is
directed between the corrugated heat exchange portions 4 of the
compound plates 2 of each heat exchanger cell 16 and makes its way
along the heat exchanger matrix 30 into the outlet ports 24, which
are themselves connected to an outlet manifold (not shown).
[0039] As the projections 14 are formed on only the outside surface
of the plates of a respective heat exchanger cell, the inside
surfaces of the plates are clear of obstructions in the vicinity of
the holes 12, so that the cold high pressure air entering the cell
through the holes 12 can spread out unimpeded to occupy
substantially the full extent of the heat exchanger matrix.
[0040] Hot low pressure exhaust gas E from the gas turbine engine
is directed into an end of the heat exchanger matrix 30 and is
forced between the cells 16 of the heat exchanger matrix 30. The
gas E is directed by the ribs 14 to occupy substantially the entire
area of the heat exchange portion 4 of each cell 16. As the exhaust
gas E is forced between the heat exchanger cells 16 and the colder
high pressure air C is forced through the interior of the heat
exchanger cells 16, heat is donated from the exhaust gas E to the
colder high pressure air C. Preferably, the two gas streams flow in
a substantially counter direction. The corrugations of the heat
exchange portions 4 cause the air C to follow a tortuous path.
Consequently, heat transfer occurs over a greater surface area and
over a greater time than if the heat exchange portions were planar,
and the overall heat transfer is thus improved.
[0041] Preferably, the compound plates 2 of each heat exchanger
cell 16 are arranged so that the corrugations of the heat exchange
portions 4 of the plates 2 criss-cross, such that the corrugations
of one compound plate are out of phase with the corrugations of an
adjacent compound plate. Preferably the corrugations are
180.degree. out of phase. This enables gas entering the cells to
traverse sideways across the corrugations thereby to occupy
substantially the whole volume of the cells 16. Additionally, this
arrangement prevents intermeshing of adjacent compound plates,
ensuring the entire matrix remains rigid and stable.
[0042] Although the heat exchanger of the present invention has
been described with reference to substantially flat, planar cells,
in an alternative embodiment, the heat exchanger is formed from
curved compound plates and may be formed from a single, spirally
would cell.
[0043] In accordance with the provisions of the patent statutes,
the principle and mode of operation of this invention have been
explained and illustrated in its preferred embodiment. However, it
must be understood that this invention may be practiced otherwise
than as specifically explained and illustrated without departing
from its spirit or scope.
* * * * *