U.S. patent number 3,831,674 [Application Number 05/307,264] was granted by the patent office on 1974-08-27 for plate type heat exchangers.
This patent grant is currently assigned to Avco Corporation. Invention is credited to Wolfgang J. Stein, Salvatore Straniti.
United States Patent |
3,831,674 |
Stein , et al. |
August 27, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
PLATE TYPE HEAT EXCHANGERS
Abstract
A heat exchanger is described which is adapted for use with a
regenerative type gas turbine engine. The heat exchanger comprises
a stack of annular disc plates which are joined in bellows fashion.
Inlet and exit plenums extend longitudinally of the stack. The
plates define alternate flow paths respectively for radial flow of
the hot gas discharge outwardly from the center of the stack and
for cross flow of pressurized air from the inlet to exit plenums.
Alternate plates are provided with flow path defining corrugations
formed both radially, in a general sense, and cross wise, generally
concentric of the discs. The remaining plates have generally
radially extending, flow paths defining corrugations. The radial
corrugations of all plates are curved to be generally concentric of
the curved sides of the inlet and exit plenums which are
respectively triangular and elliptical in cross section.
Inventors: |
Stein; Wolfgang J. (Milford,
CT), Straniti; Salvatore (Orange, CT) |
Assignee: |
Avco Corporation (Stratford,
CT)
|
Family
ID: |
23188953 |
Appl.
No.: |
05/307,264 |
Filed: |
November 16, 1972 |
Current U.S.
Class: |
165/166;
165/DIG.357 |
Current CPC
Class: |
F28D
9/0012 (20130101); F02C 7/08 (20130101); Y10S
165/357 (20130101) |
Current International
Class: |
F28D
9/00 (20060101); F02C 7/08 (20060101); F28b
003/12 (); F28b 013/06 () |
Field of
Search: |
;165/164-167 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Myhre; Charles J.
Assistant Examiner: Streule, Jr.; Theophil W.
Attorney, Agent or Firm: Hogan; Charles M. Garfinkle; Irwin
P.
Claims
Having thus described the invention, what is claimed is novel and
desired to be secured by Letters Patent of the United States
is:
1. A heat exchanger comprising
inlet and outlet connections respectively provided for first and
second fluids,
a relatively thin, first plate having first and second series of
corrugations, one series being disposed, generally, at right angles
to the other,
a pair of second plates disposed, respectively, on opposite sides
of said first plate, said second plates, in combination with said
first plate, defining, on opposite sides thereof, portions of flow
paths between the respective inlet and outlet connections for the
first and second fluids,
said second plates each having a series of corrugations generally
aligned with the first series of corrugations of the first plate
and generally at right angles to the second series of corrugations,
or cross corrugations, of the first plate,
whereby opposite sides of the first plate define portions of the
heat exchange flow paths for both the first and second fluids,
which flow paths provide a maximum of turbulence by area variations
both longitudinally and transversely of the flow directions, with a
minimum impedence to fluid flow.
2. A heat exchanger as in claim 1 wherein
the cross corrugations of the first plate engage the corrugations
of the second plates on opposite sides thereof, and
the corrugations of said first series are of a lesser height than
that of the cross corrugations, the spacing of the corrugations of
said first series matches the spacing of the corrugations of the
second plates, the corrugations of said first series are "out of
phase" with the corrugations of the second plates.
3. A heat exchanger as in claim 2 particularly adapted for use in
combination with a gas turbine engine to increase the energy level
of pressurized air (first fluid) by transferring heat thereto from
the hot gas (second fluid) discharge of the engine as the
pressurized air passes from the engine's compressor to its
combustor, said heat exchanger further including
successive first and second plates, the latter also being
relatively thin, alternately disposed and defining alternate heat
exchange flow paths for the pressurized air and the hot gas,
said first and second plates being in the form of annular discs
forming a central entrance connection for the hot gas and an outer
outlet connection therefor, said discs also including longitudinal
plennums, formed by openings therethrough, providing the inlet and
outlet connections for the pressurized air to and from the heat
transfer flow paths defined by the first and second plates, and
further wherein
the corrugations of the second plates extend generally radially of
the discs and open to the inner and outer portions thereof to
connect the heat exchange flow paths for the hot gas to the inlet
and outlet connections therefor.
4. A heat exchanger as in claim 2 wherein
adjacent first and second plates have inner and outer peripheral
flanges respectively joined to form the heat exchange flow path for
the pressurized air therebetween as the pressurized air flows from
the inlet to the outlet plennums, and
pairs of plates so joined are in turn joined to adjacent pairs by
seaming peripherally of the plennum openings therein, whereby the
discs are connected in bellows fashion with the several heat
exchange flow paths for the pressurized air and the hot gas,
respectively, separated from each other.
5. A heat exchanger as in claim 4 wherein
each plate has radial, flow path defining corrugations of the same
height as the cross corrugations, said flow path defining
corrugations being being disposed on opposite sides of the inlet
plennum openings and extending from from the inner peripheral
flanges and terminating in radially spaced relation from the outer
peripheral flanges, said flow path defining corrgations also being
disposed on opposite sides of the outlet plennum openings and
extending from the outer peripheral flanges and terminating in
radially spaced relation from the inner peripheral flanges,
said flow path defining corrugations engaging corrugations of the
second plate with which it is paired, to define the lateral bounds
of the pressurized air flow paths between adjacent plennums, said
cross corrugations being spaced from the inner and outer flanges,
whereby the pressurized air is directed from outer, inlet chambers,
radially inwardly through primary zones of heat transfer and then
through inner, exit chambers, and further wherein
the first series of corrugations of the first plates extend
radially to the inner and outer flanges thereof and cross
corrugations of the same intermediate height are formed inwardly
and outwardly of the full height corrugations to provide a waffle
effect in the portions of the first plates which define the inlet
and exit chambers.
6. A heat exchanger as in claim 5 wherein
there are a plurality of inlet and outlet plennums, alternately
spaced around said discs,
the disc openings defining the outlet plennums are generally
elliptical, and the disc openings defining the inlet plennums are
generally triangular and pointed toward the axis of the discs, said
triangular inlet openings having concave sides generally concentric
of the adjacent convex sides of the outlet plennum openings,
and
the generally radially extending corrugations of the first and
second plates are curved in generally concentric relation with the
sides of the plennum openings between which they extend, and
the cross corrugations of the first plates are generally concentric
of the axis of the discs.
7. A heat exchanger comprising
inlet and outlet connections respectively provided for first and
second fluids,
a plurality of annular discs, defining alternate heat exchange flow
paths for the first and second fluids as the flow between the
respective inlet and outlet connections therefor,
the inlet and outlet connections for the first fluid including
inlet and outlet plennums extending longitudinally of said discs
and defined by openings therein, one of said plennums being
generally elliptical in cross section with the major axis thereof
generally radial of said discs, the other of said plennums being
generally triangular and pointed toward the axis of the discs, the
sides of the triangular openings being generally concave and
concentric of the adjacent convexly curved sides of the elliptical
openings,
the heat exchange flow paths for the first fluid pass between said
discs from the inlet plennums to the outlet plennums and the heat
exchange flow paths for the second fluid pass between alternate
plates from the interior to the exterior of the discs, and
alternate plates comprise series of corrugations, between each
adjacent plennum, which corrugations extend generally radially of
the discs and are curved generally concentric of the sides of the
plennums between which they extend.
Description
The present invention relates broadly to heat exchangers and more
particularly to improvements in plate type heat exchangers.
Many different types of heat exchangers are known for transferring
heat to or from a fluid, usually transferring heat between two
fluid mediums.
In almost all heat exchangers, the rate of heat transfer is of
prime concern. This factor is of particular importance where heat
exchangers are used in regenerative type gas turbine engines.
Briefly, in such engines, waste energy of the hot gas stream
exhaust is transferred, through a heat exchanger, to a pressurized
air stream as it passes from the engine's compressor to its
combustor. Thus the energy level of the hot gas stream generated in
the combustor is proportionately increased to give an overall,
theoretical, increase in engine cycle efficiency.
Heat exchangers for regenerative type engines not only require a
high rate of heat transfer, but also require a minimum impedence or
pressure loss to the flow of the pressurized air and the hot gas
streams therethrough. Otherwise, excessive pressure drops in either
or both of the fluid flow paths could cause losses which more than
offset the theoretical gains to be derived from the regenerative
cycle. Another factor of concern in such heat exchangers, is the
wide range of temperatures encountered in cyclic operation and the
resultant stresses that are induced in the component parts of the
heat exchanger. Yet, another area of concern in heat exchangers for
regenerative type engines, particularly engines utilized for the
propulsion of aircraft, is the need for a lightweight construction
as well as a configuration having a minimum space envelope.
Plate type heat exchangers, while having other applications, have
been found particularly effective in fulfilling the needs described
above for regenerative type gas turbine engines. A particularly
effective heat exchanger of this type is disclosed in U.S. Pat. No.
3,424,240. In that heat exchanger, a stack of corrugated plates, in
the form of annular discs, define a central entrance for the hot
gas discharge of the turbine engine. From this central entrance,
the hot gasses pass radially outwardly between alternate pairs of
plates to a discharge duct. Pressurized air from the engine
compressor flows into inlet plenums extending longitudinally of the
stack of plates, through cross flow paths between the plates, to
exit plenums, also extending longitudinally of the stack of plates
and then back to the combustor of the engine.
One object of the invention is to increase the overall
effectiveness of stacked plate type heat exchangers of the general
configuration referenced above, and in so doing, to particularly
combine a high rate of heat transfer with a low impedence to fluid
flow in a compact, rugged, lightweight construction.
Another and broader object of the invention is to improve the
effectiveness of plate type heat exchangers and particularly to
increase the rate of heat transfer capabilities thereof as well as
reducing the pressure drops of fluid flows therethrough and further
to decrease the induced stresses imposed thereon during
operation.
The above ends, in accordance with the broader aspects of the
invention, are attained in a heat exchanger which includes a
relatively thin plate defining on its opposite sides, opposed
portions of flow paths for first and second fluids. This plate is
characterized by having first and second series of corrugations
with one series being cross corrugations generally at right angles
to the other.
The heat exchanger, preferably, further includes a pair of plates
disposed on opposite sides of the first plate and respectively
defining the opposite bounds of the two fluid flow paths. The
second plates also have a series of corrugations which are of the
same spacing as and aligned with one of the series of corrugations
of the first plate. Further, the corrugations of the second plates
are "out of phase" with corrugations of the first plate to define
flow paths having longitudinal and cross sections which vary in
area. Further, it is advantageous that one of the series of
corrugations of the first plate have a lesser height than the other
series of cross corrugations thereof and that the corrugations of
the second plates are generally aligned with the lower series of
corrugations of the first plate.
In a more specific aspect of the invention, a plurality of first
and second plates are formed as annular discs and are arranged in
stacked relationship to define alternate flow paths for the first
and second liquids. Further, longitudinal inlet and exit plenums
may be provided through the plates for the introduction and
discharge of the first liquid. As specifically adapted for use with
a regenerative type gas turbine engine, the inlet plenum would
receive pressurized compressor air and the exit plenum would
discharge air to the combustor of the engine after the air passes
through cross flow, heat exchange flow paths between alternate
pairs of plates. The second fluid would be the hot gas discharge of
the engine which passes through flow paths radial of the stacked
discs.
The second plates, in disc form, have series of corrugations
between adjacent plenums which extend, generally, in a radial
direction. The first series of corrugations of the first plates
also extend radially between adjacent plenums, while the higher,
cross corrugations are formed generally concentric of the discs and
engage the second plate corrugations on opposite sides.
Further, the first and second plates may have flanges peripherally
of their inner and outer diameters. The flanges of the first plates
project in one axial direction and the flanges of the second plates
project in the opposite direction in matching relationship with
flanges of the adjacent plates. These matching flanges are
respectively joined to complete the cross flow paths for the
pressurized air. Further, the longitudinal plenums may be defined
by openings in the first and second plates. The surfaces of the
adjacent first and second plates, opposite of the joined plenums
thereof, may be joined peripherally of such openings so that the
stack of plates becomes a bellows.
Another preferred feature is found in providing radial corrugations
adjacent the plenum openings which direct air flow laterally to an
entrance chamber for radial flow through a primary heat transfer
zone and then to a discharge chamber leading to the exit plenum.
Cross corrugations of a lesser height as well as the reduced height
radial corrugations are formed in the first plates in the areas of
these chambers to facilitate cross flow with a maximum heat
transfer.
Another feature of the invention is found in forming each inlet
plenum with a generally triangular cross section and each exit
plenum with a generally elliptical cross section having its major
axis extending in a radial direction. The generally radial
corrugations of the first and second plates are then formed
generally concentrically of the adjacent sides of the plenums. This
feature of the invention may also be utilized in combination with
first plates having other forms of corrugations.
The above and other related objects and features of the invention
will be apparent from a reading of the following description of a
preferred embodiment thereof, in which reference is made to thhe
accompanying drawings, and the novelty thereof pointed out in the
appended claims.
In the drawings:
FIG. 1 is a longitudinal cross section of a heat exchanger in which
the present invention is embodied;
FIG. 2 is an enlarged view of a fragmentary portion of FIG. 1;
FIG. 3 is a perspective view, partially exploded, of a stack of
plates comprising the present heat exchanger;
FIG. 4 is a fragmentary perspective view, on a greatly enlarged
scale, looking generally in the direction of arrow A in FIG. 3 and
illustrating a pair of plates which define an air flow path through
the heat exchangers;
FIG. 5 is a fragmentary perspective view, on a greatly enlarged
scale, looking generally in the direction of arrow B in FIG. 3 and
illustrating a pair of plates defining a portion of the hot gas
flow path of the heat exchanger;
FIG. 6 is a section taken on line 6--6 in FIG. 4, on an enlarged
scale;
FIG. 7 is a section taken on line 7--7 in FIG. 4, on an enlarged
scale;
FIG. 8 is a section taken on line 8--8 in FIG. 4, on an enlarged
scale;
FIG. 9 is a section taken on line 9--9 in FIG. 4, on an enlarged
scale;
FIG. 10 is a section taken on line 10--10 in FIG. 4, on an enlarged
scale; and
FIG. 11 is a section taken on line 11--11 in FIG. 4, on an enlarged
scale.
The heat exchanger, illustrated in FIG. 1 and indicated by
reference character 10, is adapted for attachment to a gas turbine
engine at a point downstream of the final turbine stage of that
engine. The engine, itself, may be of conventional construction in
accordance with well known designs for regenerative type engines.
The hot gas discharge of the engine enters the center of the heat
exchanger 10 and then is directed radially outwardly, through a
stack of plates 11, to an exhaust system which includes a
surrounding duct 12. The heat exchanger 10 comprises an adaptor
frame 14, which may be attached to a frame member of the engine.
The adaptor frame 14 has a plurality of passageways 16 and 18 which
respectively connect with engine passageways (not shown) leading
from the engine's compressor and leading to the engine's combustor.
The compressor passageways 16 are aligned with a plurality of inlet
plenums 20, see also FIG. 3, formed longitudinally through the
stack of plates 11. The combustor passageways 18 are aligned with a
plurality of exit plenums 22 also extending longitudinally through
the stack of plates 11. Cross flow paths between adjacent plenums
20 and 22 provide the primary heat exchange between the radially
flowing hot gas discharge and the pressurized compressor air. These
cross flow and radial flow paths will presently be described in
detail. The heat exchanger 10 further comprises an end frame 24 and
an end plate 26, which define the downstream limit of the hot gas
discharge flow path so that all of the hot gasses may be turned
radially outwardly through the stack of plates 11 and discharged
through the exhaust system.
The stack of plates 11, FIG. 3, comprises a series of alternately
arranged plates 11a and 11b, which are identical in outline and
differ primarily in the flow path defining corrugations formed
therein. The plates 11a and 11b are in the form of annular discs
having inner and outer flanges 28 and 29. The flanges of the plates
11a project in one axial direction and the flanges of the plates
11b project in the opposite axial direction (FIGS. 2 and 4).
Successive pairs of plates 11a and 11b are thus disposed with their
flanges 28 and 29 in face-to-face relation. These matching flanges
are seam welded or otherwise joined around their full
circumferences. The pairs of plates, thus joined, define the bounds
of the cross flow paths between plenums 20 and 22.
The plenums 20 and 22 comprise aligned openings 20a, 20b and 22a,
22b, formed in the plates 11a and 11b respectively. The surfaces of
plates 11a and 11b facing outwardly of the flange welds are joined,
as by welding, peripherally of the openings 22a, 22b, and 20a, 20b,
FIGS. 2 and 5. The stack of plates 11 is thus joined in fashion.
fashion
The pairs of plates 11a and 11b define alternate flow paths for the
pressurized air and the hot gas discharge as well as the plenums 20
and 22. The stack of plates 11 may further be formed as a series of
substacks as taught in U.S. Pat. No. 3,385,353. With such an
arrangement, and as indicated in FIGS. 1 and 2, a selected number
of plates 11a and 11b are joined as just described and their
opposite ends are secured to somewhat thicker intermediate plates
30 which have openings corresponding to the openings 20a, 20b, and
22a, 22b, and which further have positioning lugs, that are located
by rods 32 extending the full length of the stack 11.
Referencing next FIG. 4, it will be noted that the openings 22a and
22b are generally elliptical and that the openings 20a and 20b are
generally triangular and that the adjacent sides of each opening 20
and 22 are similarly curved, or generally concentric. This
relationship, maximizes the heat transfer area of the discs and
minimizes the overall volume, or space envelope, of the heat
exchanger, when coupled with correspondly curved corrugations in
the plates 11a and 11b as shown in FIGS. 4 and 5.
More specifically, each of the plates 11a has a series of
corrugations 34 between adjacent openings 20a and 22a. The
corrugations (see also FIGS. 6-11) are generally sinusoidial or
what will herein be referenced as "regular wave-form." The wave
form corrugations 34 extend, generally radially, from the inner
flange 28 to the outer flange 29 and are further curved, to
correspond to the curvature of the sides of the openings 20 a and
22b between which they extend. Each plate 11b is corrugated in a
more involved fashion. First, there are flow path defining
corrugations 36 and 38 which extend marginally of the openings 22b
and 20b respectively. The corrugations 36 and 38 are curved
similarly to the wave-form corrugations 34 and are "out of phase"
therewith so as to sealingly engage matching corrugations 34
respectively adjacent the openings 22a and 20a. The corrugations
36, on opposite sides of the exit plenum opening 22, extend
inwardly from the outer flange 29b and terminate at a point space
outwardly of the inner flange 28b. In a similar fashion, the
corrugations 38, on opposite sides of each inlet plenum 20a, extend
outwardly from the inner flange 28b and terminate in spaced
relationship from the outer flange 29b. Between the corrugations 36
and 38, is a series of corrugations 40 of an intermediate height,
which have a similar curvature to the curvature of the corrugations
34, are of the same spacing and also "out of phase" therewith. It
will also be seen that the series of corrugations 40 extend from
the inner flange 28b to the outer flange 29b. Further, there is a
series of cross corrugations 42 extending between the co-extensive
portions of the corrugations 36 and 38. The corrugations 42,
generally at right angles to the corrugations 40, are generally
concentric of the axis of the discs 11 and have a spacing generally
matching that of the corrugations 40. The heighth of the cross
corrugations 42 matches that of the corrugations 36 and 38, so that
there is a grid of engagement points between the corrugations 34
and 42 within the boundary defined by the co-extensive portions of
the corrugations 36 and 38, herein referenced as a zone of primary
heat transfer. In the areas above and below, are inlet and exit
chambers, which have a "waffle" type surface formed by the
intermediate corrugations 40 and cross corrugations 44 which are of
the same intermediate height.
The described configuration of the plates 11a and 11b defines cross
flow paths from one inlet plenum 20 to the adjacent exit plenums 22
on either side thereof. The outer grid work of the intermediate
height corrugations 40 and 44 form a lateral entranch chamber
defined at the left hand end thereof by the linear engagement
between the corrugation 36 and its matching corrugation 34. From
this lateral entrance chamber, the cross flow path extends radially
inwardly between the co-extensive portions of the corrugations 36
and 38, forming a zone of primary heat transfer, and then through a
discharge chamber similar to the entry chamber described above
except that the opening thereof directs the air towards the plenum
22.
It will be noted that the cross flow path described, provides
throughout its length, a varying cross sectional area and
longitudinal sectional area which minimizes the boundary layers and
thus increases the rate of heat transfer. Further, it will be noted
that in the grid of corrugations in the primary heat transfer zone,
between the co-extensive areas of corrugations 36 and 38, the
variations in the flow path area become more pronounced for greater
heat transfer effectiveness. This is opposed to the entry and exit
chambers which, while providing flow area variation, also
facilitate lateral flow of the air to facilitate its entry and
discharge from the primary area.
Using FIG. 4 as a point of reference, the corrugations to the right
of the opening 20b between the next adjacent opening 22 would
define the same series of an entry chamber, primary exchange zone
and discharge chamber as described above. In both instances, the
air, from the inlet plenum 20, enters the outer corner of the grid
work and flows radially inwardly. This is to say that air passing
through the plenum 20 has a split cross flow path to both of the
adjacent plenums 22 and similarly both of the plenums 22 receives
cross flow from the plenums 20 on either side thereof, as is also
indicated in FIG. 3.
Referencing next FIG. 5. Plates 11a and 11b are illustrated as they
define a portion of the radial flow path for the hot gas discharge
through the stack of plates. As will be seen, the corrugations 34
also form a grid of contact points with the cross corrugations 42,
in the plate 11b, to form a flow path for the hot gas discharge
(see also FIGS. 6-11) which varies greatly in area from the inner
circumference from the plates 11a and 11b to the outer
circumference thereof.
It will also be noted that in each instance, the secondary flow of
the pressurized air from the passageways 20 to the passageways 22
is counter to the flow of the hot gas stream in the primary area of
heat exchange.
All of these factors contribute to a high rate of heat exchange for
greater efficiency. Further, the described configuration of both
the cross flow paths of the pressurized air and the flow paths of
the hot gas discharge have proven to be highly effective in
minimizing pressure drops so as to minimize the decrement to
overall cycle efficiency which is attributable to such losses.
Yet another factor to be noted is that the described corrugations
of the plates 11a and 11b contribute to the overall efficiency of
the heat exchanger in that the spring effect, or resilience, of
these corrugated plates minimizes induced stresses in the plates
which are inherent in any operation in a high temperature
environment as described. This is to say that in a cyclic operation
of the engine heat exchanger, the plates 11a and 11b will contract
and expand exerting compressive forces on the plates themselves
which vary in magnitude during operational cycles. The resultant
low stresses achieved enable, for a given plate material, use of
thinner section material which further contributes to the
efficiency of heat transfer. The ability to utilize thinner section
material for the plates 11a and 11b also minimizes the overall
weight heat exchanger, to the end that its incorporation in a gas
turbine engine used for the propulsion of aircraft becomes more
efficient in that the overall aircraft system.
While a preferred embodiment has been described, particularly
directed towards an application in a gas turbine engine, variations
of this embodiment will occur to those skilled in the art for such
an application and other variations thereof will be apparent for
utilization in other applications of heat exchangers. The broader
aspects of the invention, as well as the full spirit and scope
thereof, are therefor to be derived solely from the following
claims.
* * * * *