U.S. patent number 3,894,581 [Application Number 05/351,439] was granted by the patent office on 1975-07-15 for method of manifold construction for formed tube-sheet heat exchanger and structure formed thereby.
This patent grant is currently assigned to The Garrett Corporation. Invention is credited to Fred W. Jacobsen, Stanley T. Jakubowski, Herman Sam Weiner.
United States Patent |
3,894,581 |
Jacobsen , et al. |
July 15, 1975 |
Method of manifold construction for formed tube-sheet heat
exchanger and structure formed thereby
Abstract
A heat exchanger plate of single unitary structure and
relatively thin material has a deep draw formed through one surface
adjacent to each of the opposite ends to provide fluid openings and
a lesser depth inner draw formed in the other surface to provide a
fluid passage communicating with the fluid openings. The plate is
adapted to oppose adjacent plates in a stacked configuration to
provide heat transfer between separate fluids flowing through
counterflow passages on opposite sides of the plate. The recessed
area on one surface of the plate forms a fluid passage with its
adjacent plate in the stacked array for flow of a first fluid
through the stack from side to side of an enclosing housing. A
collar formed around each plate opening by the deep draw is adapted
to nest with a corresponding collar of an adjacent plate to provide
manifold sections communicating with a second fluid passage. The
stacked configuration of corresponding plates establishes
pluralities of first and second passages alternately arrayed for
adjacent counterflow of separate fluids for maximal heat transfer
between them. The nested plates may be brazed together, eliminating
the necessity for slow and costly welding procedures to develop the
strength required to withstand operating pressures. Finned elements
positioned between the plates improve the efficiency of the heat
exchange process. The structure is compact, light weight, strong
and efficient in operation. The fabrication process is simplified
and economical.
Inventors: |
Jacobsen; Fred W. (Los Angeles,
CA), Jakubowski; Stanley T. (Carson, CA), Weiner; Herman
Sam (Southgate, CA) |
Assignee: |
The Garrett Corporation (Los
Angeles, CA)
|
Family
ID: |
23380929 |
Appl.
No.: |
05/351,439 |
Filed: |
April 16, 1973 |
Current U.S.
Class: |
165/166 |
Current CPC
Class: |
F28F
9/0275 (20130101); F28D 9/00 (20130101); F28F
3/025 (20130101); Y10T 29/49364 (20150115); Y10T
29/49366 (20150115) |
Current International
Class: |
F28F
27/00 (20060101); F28F 27/02 (20060101); F28D
9/00 (20060101); F28F 3/00 (20060101); F28F
3/02 (20060101); F28f 003/00 () |
Field of
Search: |
;165/130,131,152,153,157,166,167,170,172,173,154 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Myhre; Charles J.
Assistant Examiner: Streule, Jr.; Theophil W.
Attorney, Agent or Firm: Bissell; Henry M.
Claims
What is claimed is:
1. Heat exchanger apparatus of the counter-flow type having inlet
and outlet manifolds integrally combined with a heat exchanger core
comprising:
a plurality of formed plates in stacked array arranged by pairs in
back-to-back relationship to define a series of layered passages
for a first fluid, each of said plates having a central section
between opposed end sections, each of said end sections having at
least one manifold opening therein surrounded by a cup-like
protrusion in the form of a collar portion extending generally
orthogonally of the plate about the periphery of said opening, the
collar portions of each plate constituting segments of respective
inlet and outlet manifolds extending through the stacked array,
each manifold within said stacked array consisting of said
segments;
the formed plates in said stacked array comprising a repetitive
sequence of first, second and third distinct configuration types,
one type being provided in pairs;
the plates of said first type comprising a collar portion of
intermediate depth and having a flange extending outwardly along
the outer periphery of one edge thereof;
the plates of said second type having a collar portion of depth
greater than that of the first type and having a flange extending
outwardly along the outer periphery of one edge thereof;
the plates of the third type having a collar portion of lesser
depth than that of the first type and having a flange extending
outwardly along the outer periphery of one edge thereof;
the collar portions of the plates of said second and third types
having like outer diameters which are less than the inside diameter
of the collar portion of said first type plate in order to permit
the nesting of said second and third type plate collar portions
within the collar portions of the first type plates;
the plates of said first type being arrayed back-to-back by pairs
in sealing relationship abutting at the collar flanges thereof to
define a first passage layer for the first fluid in communication
with said manifolds;
the plates of said second and third types being arrayed
back-to-back by pairs with the collar portions thereof nesting
within corresponding collar portions of said first type plates such
that the second type plate collar overlaps the flange juncture of
the adjacent first type plate collars, said second and third type
plates together defining a second passage layer for the first fluid
in communication with said manifolds and also defining with the
respective adjacent first type plates successive passage layers for
the second fluid, the collar portions of plates defining said
second fluid passage layers being configured to seal said second
fluid from communication with said manifolds, the second fluid
passages being open along the outer periphery of said end sections
except at the location of said manifolds; and
a housing for enclosing said stacked array and directing the second
fluid to and from the end portions thereof.
2. Apparatus in accordance with claim 1 wherein the plates of said
first type further include a re-entrant portion extending outwardly
about at least part of said collar portion along the edge opposing
the flanged edge thereof, said re-entrant portion arranged when the
plates are nested in said back-to-back relationship to abut against
and reinforce the flange junctures of the second and third type
plates.
3. Apparatus in accordance with claim 1 wherein each of said plates
is provided with an offset portion to define access between the
manifolds and the passages for the first fluid when said plates are
nested in said back-to-back relationship.
4. Apparatus in accordance with claim 3 wherein the collar portions
of the first and second type plates are partially cut off along a
region adjacent the offset portion of the collar but along the
opposite edge thereof in order to prevent blocking the access
opening defined by offset portions of the adjacent plates in the
stacked array.
5. Apparatus in accordance with claim 1 wherein one repetitive
sequence comprises a pair of first type plates joined together in
flange-abutting back-to-back relationship and one each of the
second and third type plates stacked therewith such that the
collars of the latter two plates are nested within the collars of
the first type plates in abutting relationship of the unflanged
edges;
the collar of the second type plate overlapping the juncture of the
first type plates with the abutting juncture of the unflanged edges
of the second and third type plates being in turn overlapped by the
collar of one of the first type plates of said pair;
the interior corners of the collar flanges of the second and third
type plates abutting against the unflanged edges of the collars of
the first plates, respectively.
6. Apparatus in accordance with claim 5 wherein the unflanged edges
of the collars of the first type plates are each formed with a
re-entrant portion for reinforcing the collar flange of the
associated plate of said second and third types.
7. Apparatus in accordance with claim 5 wherein the core is formed
of stacked repetitive sequences of said four plates with adjacent
repetitive sequences being arrayed in back-to-back relationship and
joined together at adjacent flanges thereof.
8. Apparatus in accordance with claim 1 wherein each of said plates
is formed of material of substantially the same thickness and
having similar thermal expansion properties.
9. Apparatus in accordance with claim 1 wherein said plates are
joined together at all junctures of adjacent surfaces by
brazing.
10. Apparatus in accordance with claim 1 wherein said means for
sealing the manifold opening against communication with the second
fluid passages comprises overlapping sections of the collar
portions of adjacent plates which overlap throughout the
circumference of said collar portions.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to recuperative heat exchangers of the
formed plate type and, in particular, to plate structures adapted
to transfer heat from one fluid to another through the surfaces of
the plate and to the methods of forming such.
2. Description of the Prior Art
Recuperative heat exchangers are known in which a plurality of
plates of relatively thin material are formed and stacked so as to
provide heat transfer through the plates to and from a series of
alternate flow passages formed between alternate pairs of
plates.
In the interchange of heat between the fluid passages and the heat
exchanger, fluids are separated by a plate of high thermal
conductivity. In order to obtain the maximum efficiency, the design
of the heat exchanger must take into consideration several critical
factors. Among these factors which affect the efficiency of design
are: (1) the amount of heat transfer area in intimate contact with
the fluid, (2) a boundary layer resistance of the plate to the
exchange of heat between the fluids, (3) the difference in thermal
conductivity of the various parts of the heat exchanger, and (4)
the overall structure of the heat exchanger core. The design of
prior art heat exchangers has resulted in compromises in design
according to the above factors whereby fluid capacity suffers with
a decrease in size or vice versa, because of the inability of
designing a heat exchanger to optimize all of these factors. For
example, strength and reliability of the overall structure dictate
some parts of larger size than others resulting in large
differences in thermal conductivity of the parts. Conversely, if
the parts are of the same size the overall structure may be too
weak to stand the pressure and temperature gradients therein or may
be too heavy and cumbersome for practical use in any but the most
limited applications.
Various attempts have been made to solve the abovenoted problems in
heat exchangers by designing plate type heat exchangers comprising
a series of stacked thin metallic plates which are assembled in
face-to-face arrangement to define fluid passages therebetween for
separate flow of primary and secondary fluids in the heat exchange
relation. A thin plate type of heat exchanger has been generally
very difficult to manufacture, due to the many welding and bonding
operations required, and difficult to achieve a strong structure
because of the thinness of the plate material.
A preferred type of heat exchanger would have a uniform thickness
of plate and other components utilized throughout the heat
exchanger in order to maintain a uniform thermal conductivity
between the parts. In this manner localized adverse expansion and
contraction effects encountered during the heating and cooling
cycle would be minimized. In the interest of maintaining a low cost
of manufacture it would be highly advantageous to make a heat
exchanger of plates which are similar in structure and form so as
to present surfaces adapted to mate with each other to contribute
adequate seals. In prior art heat exchangers typically a module of
two plates is provided, wherein the plates are recessed to
accommodate the flow of two fluids so as to provide a reliable and
effective basis for sealing around the module perimeter as well as
adequate structural strength. However, to accomplish this the
sealing is generally provided by bars which are welded or brazed to
the stacked plates. The great difference in thermal conductivity of
the bars, as compared to the thin material of the plates, has a
deleterious effect on the heat exchanger, causing undesirable
stresses during expansion and contraction of the stacked parts.
Thus, the plate type heat exchanger of the prior art, which is
formed of a series of plates stacked together in spaced
side-by-side relation, has been limited in efficiency due to the
above-mentioned disadvantages therein.
Accordingly, it is essential that the heat exchanger be designed
with the above-mentioned factors taken into consideration in order
to achieve a low cost, high efficiency heat exchanger. In a typical
prior art recuperative heat exchanger, the type of construction is
usually characterized by a large number of components which result
in high labor efforts with resulting high cost of fabrication of
the heat exchangers. Structural problems are associated with the
thermal inertia incompatibility of the different size core elements
and these severely limit the design objective. Existing heat
exchangers for large industrial gas turbines realize a fairly low
compactness resulting in a unit of extremely large volume and
weight. On the other hand, providing a heat exchanger of high
compactness results in an extremely high cost of manufacture. Prior
attempts at providing a more compact heat exchanger of low cost and
high efficiency have met with failure due to the inability to solve
the problems set forth above.
The design of a plate type heat exchanger must take into
consideration the transient metal temperature differentials between
the various parts. These differentials occur during thermal
transients and are caused by the temperature time lag of the
relatively heavier sections in the core, such as the bars which may
be used to enclose the relatively thin stacked plates. These
heavier reinforced bars for sealing the gauge manifolds are
thermally incompatible with the plates. Additionally, the heavy
gauge manifolds which are required for the input and output fluid
passages often result in a transient thermal stress at the ends of
the core matrix which exceeds the material yield strength. Of
course, if the manifold sections were designed of thin materials,
the structural strength of the heat exchanger core would be
unacceptable.
Thus, it may be seen that a heat exchanger is desired that will
achieve the thermal inertia compatibility between the various
elements of the core without sacrificing the structural strength
and efficiency of the heat exchanger. Such a structure should
desirably admit of fabrication without inordinate labor costs to be
commercially feasible.
SUMMARY OF THE INVENTION
In brief, particular apparatus in accordance with the present
invention utilize a series of formed plates of single unitary
structure and relatively thin material, each including integral
inlet and outlet manifold sections in combination with a sandwich
configuration developing counterflow fluid passages. Each
individual plate is formed to provide a deep draw in opposed end
sections of the plate, forming collars or cup-like protrusions to
permit nesting together with other, similarly formed plates to
develop the inlet and outlet air manifold passages. The collars are
particularly shaped so as to admit of being nested together and
brazed into an integral unit with appropriate reinforcement of the
assembled structure at the various juncture lines. Furthermore, the
collar manifold sections are fashioned so as to define air openings
communicating between the manifold and the interior air passages of
the heat exchanger core matrix.
In accordance with an aspect of the invention, three different
plate designs are sufficient, when repeated throughout the stacked
core structure, to develop the desired structural integrity with
the manifold section reinforcement as described, while providing
the desired openings between the manifolds and the counter-flow
passages. These three plates, designated respectively A-plates,
B-plates and C-plates, all have extended flanges about the outer
periphery thereof for joining along the flange surface with a
corresponding surface of an adjacent plate. One of the designs, the
A-plate, is utilized in pairs, relative to the B-plates and
C-plates. A pair of A-plates are joined together in abutting
relationship with each other at their flange portions. The B- and
C-plates are joined to each other in similar abutting relationship
overlapping the adjacent A-plate collar juncture line. The B- and
C-plates have slightly smaller diameters of their collar portions
then do the A-plates in order that they may nest within the collar
manifold sections of the A-plates and also to allow adequate gap
for a continuous circumferential braze joint. The flange sections
of the B- and C-plates are provided with additional reinforcement
for rigidity by an extended re-entrant section of the collar of the
A-plates which overlap the B- and C-plate collar manifold
juncture.
In the counter-flow section of the heat exchanger core, fin element
layers are provided for additional strength and rigidity, as well
as to break up the smooth flow of air and improve the heat transfer
characteristics at the fluid-structure interfaces. Between adjacent
pairs of plates defining the air passages are the gas flow passages
which extend directly through the core matrix and communicate with
the outside thereof at the end portions extending between adjacent
air manifolds. The entire core structure may be made up of thin
metal elements, the plates being fabricated preferably from 0.010
inch thickness, type 347 stainless steel. Thus, the thermal
stability of the entire structure is exceedingly favorable, since
there are no particular structural components having great thermal
lag relative to any other components, as is the case in presently
known heat exchanger assemblies utilizing reinforcing bars at the
core boundaries for sealing and/or reinforcement. Other materials
may be employed in heat exchangers of the invention. For example,
it has been found that embodiments of the invention may be
fabricated of ceramic materials shaped to the desired configuration
and then fired to a permanent hardness. The desired properties of
materials suitable for use in the practice of the invention are: a
low thermal coefficient of expansion with good thermal shock
resistance; good tensile strength; and good workability of the
material.
BRIEF DESCRIPTION OF THE DRAWING
A better understanding of the present invention may be had from a
consideration of the following detailed description taken in
conjunction with the accompanying drawing, in which:
FIG. 1 is a perspective view of one particular arrangement in
accordance with the present invention;
FIG. 2 is a side elevation of another arrangement in accordance
with the invention, similar to that of FIG. 1, except that somewhat
different housing and headering configurations are shown;
FIG. 3 is a perspective view of a portion of the arrangement of
FIG. 1, taken in section at the arrows 3 thereof;
FIG. 4 is a plan view of the heat exchanger core of FIGS. 1 and
2;
FIG. 5 is another sectional view of a portion of the arrangement of
FIG. 4 taken at the arrows 5 thereof;
FIG. 6 is a side sectional view showing one of the elements
employed in the core of FIG. 4;
FIG. 7 is a side sectional view of another element employed in the
arrangement of FIG. 4;
FIG. 8 is a side sectional view of a third element employed in the
arrangement of FIG. 4; and
FIG. 9 is a side sectional view showing the elements of FIGS. 6-8
nested together to form a portion of the core of FIG. 4.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The embodiment of the invention as shown in FIG. 1 comprises a heat
exchanger assembly 10 having a core 12 enclosed within a housing
14. The core is provided with integrally fashioned manifolds 16, 17
on opposite sides of the central heat exchanger, connected
respectively to headers 18, 19. The heat exchanger core 12 is
supported within the housing 14 by means of mounts 20. The housing
14 is provided with inlet and outlet passages 22 and 23 for passing
a hot gas through the heat exchanger core 12 in intimate heat
exchange relationship with air flowing between the respective
manifolds 16, 17. In operation, air enters the header 19 through an
inlet pipe 24 which incorporates a load compensating bellows
portion 26 to adjust for dimensional variation, passes upward into
the manifolds 17 and then into the air flow passages in the heat
exchanger core 12. The air then flows upward through the manifolds
16 into the header 18 and out through an outlet pipe 28 which is
also provided with a load compensating bellows portion 29. At the
same time hot gas is flowing into the housing 14 through the inlet
duct 22, thence through gas flow passages sandwiched between the
air flow passages of the heat exchanger core 12, and finally out of
the housing 14 through the outlet duct 23. It will thus be
understood that the air and gas flow is in a direct counterflow
relationship within the sandwich structure of the heat exchanger
core 12.
A similar assembly 10A is shown in a sectional elevation view of
FIG. 2, in which the same heat exchanger core 12 is employed, but
in which a slightly different housing 14A having inlet and outlet
ducts 22A, 23A are provided. Also, the headering arrangements 18A
and 19A are slightly different from those shown in FIG. 1.
FIG. 3, which is a perspective view, partially broken away and
partially in section, shows structural details of the portion of
the core 12 at the section line arrows 3--3 of FIG. 1. The portion
depicted in FIG. 3 is shown comprising a part of the core section
12 and a part of one of the air manifolds 16. The core section 12
includes a plurality of formed plates 30 sandwiched together with
and separated from each other by respective layers of gas fins 32
and air fins 34. The formed plates 30 are provided with collars 36
to develop the manifold 16 extending into the sandwiched structure
and define strategically located openings 38 for passing air
between the manifold 16 and the air fins 34. Correspondingly,
openings are provided at 40 for the passage of hot gasses from the
outside of the core 12 to the gas passages containing the gas fins
32. Thus as may be seen from FIG. 3, the respective gas and air fin
configurations within the sandwich structure of the core 12 serve
to provide a certain rigidity and integrity to the structure while
at the same time serving to provide the desired heat transfer
between the adjacent gas and air streams while developing the
desired turbulence in the respective fluid flows so as to enhance
the heat transfer characteristics of the fluid-metal interface.
FIG. 4 may be considered a plan view of the core 12 of FIG. 1. It
may also be considered as representing in general outline form one
of the formed plates 30 making up the core 12. As may be seen, the
plate 30 is provided with an offset flange 42 extending about its
periphery. This offset flange is for the purpose of joining to a
similar flange on the plate of the next layer in the stack so as to
define a fluid passage having openings communicating therewith only
as indicated hereinabove; i.e. where the fluid passage is an air
stream, openings communicating with the manifolds 16 and 17,
whereas for a gas stream the openings communicate with the outside
of the core 12 at segments between adjacent manifolds 16 or 17.
Such a segment may be seen at 44 on the left-hand side of FIG. 5,
which is a section of a portion of the core 12 taken along the line
5--5 of FIG. 4 looking in the direction of the arrows. Gas openings
40 and the juncture of adjacent flanges 42 are shown in segment 44
of FIG. 5. Air openings 38 are shown in FIG. 5 on the opposite side
of the manifold 16 and communicating therewith.
The respective formed plates 30 which, with the gas fin elements 32
and the air fin elements 34, are nested together to make up the
core structure 12 are fabricated in three different configurations.
Each plate 30 is formed with a cup-like protrusion providing a
collar 36 or a manifold section of each of the individual manifolds
16 and 17. The details of structural configuration of the
respective formed plates 30 and the manner in which they are nested
together in the core 12 may best be seen by reference to FIGS. 6-9.
FIG. 6 shows a portion of plate 30a and a cup-like protrusion or
collar 36a. FIG. 7 similarly depicts a formed plate 30b having a
cup-like protrusion or collar 36b. FIG. 8 shows a corresponding
formed plate 30c with its collar 36c. The plates 30a, 30b and 30c
may be referred to respectively as "A-plates", "B-plates", and
"C-plates". Each of the collars 36 of FIGS. 6-8 is provided with a
corresponding flange portion 42a, 42b or 42 c about its outer
(left-hand) periphery. The A-plate collar 36a also has an
additional reentrant portion 46 along the edge of the collar 36a
opposite the flange 42a. It will be noted that the diameters of the
collars 36b and 36c are the same but are slightly less than the
diameter of the collar 36a, the outside diameters of collars 36b
and 36c being fixed to match the inside diameter of collar 36a.
Each of the plates of FIGS. 6-8 is provided with an offset segment
48a, 48b, 48c as the case may be. Also, plates 30a and 30b of FIGS.
6 and 7 have a diagonal cutout 50a or 50b removed from their
respective collars 36a and 36b along the edge which is opposite to
the offset segments 48a, 48b.
The manner in which the plates 30 of the core 12 are nested
together can best be seen in FIG. 9 which is an enlarged section
generally corresponding to FIG. 5. A single sequence of plates 30
comprises two A-plates, one B-plate and one C-plate. The two
A-plates are joined in butting relationship back to back so that
their respective flanges 42a are together. The sequence may be
considered beginning at the top of FIG. 9 with a B-plate juxtaposed
in upside down relationship to the way in which the plate 30b is
shown in FIG. 7, nested within the two abutting A-plates, and
followed by a C-plate, also nested within the lower of the two
A-plates in abutting relationship with the B-plate above it. The
sequence then repeats itself, proceeding in the downward direction
in FIG. 9, with another B-plate nested within a pair of abutting
A-plates, etc.
For each sequence of four formed plates and nested collars as just
described, two air layers with corresponding air openings 38 and
two associated gas layers are formed. The upper air opening 38 in
FIG. 9 is defined by the juncture of the two offset segments 48a of
the abutting A-plates. The lower of the two air openings 38 in FIG.
9 is formed by the juncture of the offset segments 48b and 48c of
the abutting B- and C-plates respectively. The diagonal cutouts 50a
and 50b serve to provide the desired clearance for communication
between the manifold and the respective air openings 38.
FIG. 9 illustrates the manner in which the configuration and
dimensions of the respective A-, B- and C-plates, when nested
together as shown, serve to provide reinforcement and strengthening
for the manifold portion of the core 12. It will be appreciated
that the core 12 is pressurized to substantial pressure levels
(e.g. in the vicinity of 100 pounds per square inch) in normal
operation. Throughout the extent of the manifold, there is a double
layer of collar elements 36 by virtue of the insertion of portions
36b and 36c within the abutting portions 36a. Furthermore, the
collar 36b overlaps the abutting portion of the two A-plates at the
flanges 42a. Moreover, where the B and C plates abut at collar
portions 36b and 36c without the possibility of an overlapping
joint, additional reinforcement is provided for the juncture of the
flanges 42b and 42c by the re-entrant portions 46 of the adjacent
A-plates. Strengthening of the respective junctures in this fashion
serves to resist the so-called "bellows" effect in which a simple
flanged plate structure tends to expand in bellows fashion when
subjected to pressurized fluids flowing therethrough. Simple
flanged structures tend to develop leaks and ruptures about the
juncture lines because of failure of the soldering or brazed joint
in tension or through successive flexing cycles. The present
structure advantageously serves to provide the necessary
reinforcement to prevent or minimize the incidents of failure in
this manner. Moreover, the configuration of the core structure
readily admits of repair by soldering or brazing when a leak or
rupture is encountered, since such a failure will occur at a
juncture line and all juncture lines, either inside or outside the
manifold, are readily accessible to the implements needed to repair
the rupture.
Various configurations of elements may be employed to develop the
gas and air layers in the sandwich structure of the heat exchanger
core. These may include the finned elements as disclosed, which
themselves may be of various types. For example, a plain
rectangular or rectangular offset fin may be employed. The fins may
be triangular or wavy, smooth, perforated or louvered. As an
alternative to the plate-fin structure, a pin-fin configuration may
be employed. Alternatively, tubular surface geometries may be
utilized which encompass configurations of plain tube, dimpled tube
and disc finned tube structures. Also, strip finned tube and
concentric finned tube configurations may be employed. Some of
these structures may be more adaptable to cross-flow than the
counter-flow arrangements of the present invention. However, where
the structures are utilizable in counter-flow configurations, they
may be employed within the scope of the invention.
In the fabrication of arrangements in accordance with the
invention, the respective plate and fin elements are first
prepared, including the structures for the inlet and outlet
openings. The plates are formed by successive strike operations.
The first strike forms the inner draw depth for the central core,
fin containment region and the deep manifold collar section with
its cup-like protrusion. A second strike forms the outer plate
periphery, including the sealing peripheral flange. Next a trim
strike removes the peripheral excess sheet stock as well as the
cutout portions of the manifold collar sections. The fin elements
are formed according to the type of fin being employed. The various
parts are then cleaned as by immersion or spraying with suitable
solvents. An ultrasonic cleaning tank may be used if desired. A
selected brazing alloy is then deposited on all surfaces which are
to be brazed and the various elements are stacked together into an
assembly corresponding to the core matrix which is to be
fabricated. The assembled parts are then brazed in a controlled
atmosphere furnace until all adjacent surfaces are properly brazed.
After the completion of the braze operation, the headers 18 and 19
(FIG. 1) and the remainder of the integral air inlet and air outlet
ducting are attached to the core matrix and the assembly is then
ready for mounting in its housing.
An important feature of the apparatus in accordance with the
invention is the method of fabrication such that the structure is
provided with integral sheet or plate closures and integral
manifolds. This is accomplished by the provision of flange
junctures along all closure lines or the combination of flange
junctures with overlapping collar segments in the manifold
sections. Apparatus fabricated in accordance with the present
invention dispenses with the need for special boundary sealing or
support elements, such as the header bars which may be employed
about the periphery of heat exchangers of the prior art. This is
particularly important in applications of apparatus of the present
invention where the weight of the structure is a critical factor,
as in utilization of the apparatus in motor vehicle, turbine type
power plants, because of the problems encountered with thermal
stresses where thick-thin material structure is employed. In
apparatus in accordance with the present invention, the respective
components are all more or less of the same general thickness so
that such problems are avoided.
Although there have been described hereinabove specific methods and
apparatus of formed plate, counter-flow fluid heat exchanger
structures in accordance with the invention for the purpose of
illustrating the manner in which the invention may be used to
advantage, it will be appreciated that the invention is not limited
thereto. Accordingly, any and all modifications, variations or
equivalent arrangements which may occur to those skilled in the art
should be considered to be within the scope of the invention as
defined in the attached claims.
* * * * *