U.S. patent application number 11/003852 was filed with the patent office on 2006-06-08 for high pressure header and heat exchanger and method of making the same.
Invention is credited to Siegbert Altendorfer, Gregory G. Hughes, Stephen P. Memory, Johannes Moser, C. James Rogers.
Application Number | 20060118286 11/003852 |
Document ID | / |
Family ID | 36481194 |
Filed Date | 2006-06-08 |
United States Patent
Application |
20060118286 |
Kind Code |
A1 |
Memory; Stephen P. ; et
al. |
June 8, 2006 |
High pressure header and heat exchanger and method of making the
same
Abstract
A method of providing volume production of highly pressure
resistant headers (10), (12) is provided and allows the headers
(10), (12) to be formed of a header structure (10), (12) with a
relatively thin wall portion (32) and a relatively thick wall
portion (30). A strip (40) is utilized to provide the desired
thickness at the thin wall portion (32) while allowing both the
thin wall portion (32) and the strip (40) to have tube slots (34),
(42) formed therein by a one step punching operation.
Inventors: |
Memory; Stephen P.;
(Kenosha, WI) ; Hughes; Gregory G.; (Milwaukee,
WI) ; Rogers; C. James; (Racine, WI) ;
Altendorfer; Siegbert; (Wiener Neustadt, AT) ; Moser;
Johannes; (Enzesfeld, AT) |
Correspondence
Address: |
WOOD, PHILLIPS, KATZ, CLARK & MORTIMER
500 W. MADISON STREET
SUITE 3800
CHICAGO
IL
60661
US
|
Family ID: |
36481194 |
Appl. No.: |
11/003852 |
Filed: |
December 3, 2004 |
Current U.S.
Class: |
165/173 ;
165/176 |
Current CPC
Class: |
F28F 2225/08 20130101;
F28F 9/0214 20130101; F28D 1/0476 20130101; F28D 2021/0073
20130101; F28F 9/0224 20130101; F28F 9/0243 20130101 |
Class at
Publication: |
165/173 ;
165/176 |
International
Class: |
F28F 9/02 20060101
F28F009/02 |
Claims
1. A method of making a high pressure resistant header for a heat
exchanger, comprising the steps of: (a) providing an elongated
header structure including a pair of side-by-side longitudinally
extending passages, the passages surrounded by a wall of sufficient
thickness to resist deformation when a fluid is placed within said
passages at an operating pressure at which deformation is to be
resisted; (b) thinning the wall along its length by providing a
first mating exterior surface on a part thereof so that the wall,
at said first mating exterior surface, is sufficiently thin that
tube slots may be punched in said wall at said first mating surface
extending through said wall into said passages; (c) punching tube
slots at predetermined spaced intervals in said wall at said first
mating surface, with some of the slots extending into one of the
passages and other of the slots extending into the other of the
passages; (d) providing an elongated strip having a second-mating
surface complementary to said first mating surface and of a
thickness such that the combined thickness of the strip and said
wall at its first mating surface is about equal to or greater than
said sufficient thickness of said wall; (e) punching tube slots in
said strip at said predetermined spaced intervals; (f) abutting the
second mating surface of said strip to the first mating surface of
said header structure with the tube slots in each being aligned
with one another; and (g) bonding the strip to the header structure
along their respective lengths to provide a unitary header with
tube slots therein.
2. The method of claim 1 wherein both said mating surfaces are flat
surfaces.
3. The method of claim 2 wherein steps (a) and (b) are performed
simultaneously by extrusion of said header structure.
4. The method of claim 1 wherein steps (a) and (b) are performed
simultaneously by extrusion of said header structure.
5. The method of claim 1 wherein step (b) is performed by providing
a strip receiving groove in said part of said header structure
exterior surface.
6. The method of claim 5 wherein said groove has a flat bottom
surface defining said first mating surface and said second mating
surface is flat.
7. The method of claim 1 wherein step (e) is performed by punching
the tube slots in said strips to be of substantially the same size
and shape as the tube slots in the first mating surface.
8. The method of claim 1 wherein step (b) is performed by forming a
strip receiving groove in said wall.
9. The method of claim 8 wherein step (f) is preceded by the step
of providing tabs on opposite sides of the strip receiving groove
and succeeded by the step of deforming the tabs over the strip.
10. The method of claim 1 wherein step (f) is preceded by the steps
of providing tabs on opposite sides of said first mating exterior
surface and step (f) succeeded by and step (g) preceded by the step
of deforming the tabs over opposite edges of the strip.
11. The method of claim 1 wherein said passages of step (a) are
provided with a cylindrical shape.
12. The method of claim 1 wherein said passages of step (a) are
provided with a non-cylindrical shape.
13. A header for a high pressure heat exchanger, comprising: an
elongated tubular like element having a pair of side-by-side
longitudinally extending passages and a tube receiving side, said
element being a unitary structure having a relatively thick wall
partially surrounding said passages and a relatively thin wall at
said tube receiving side; a first mating exterior surface defined
by a relief at said relatively thin wall of said element; a
plurality of punched first tube receiving slots at said first
mating surface in fluid communication with said passages and
located at predetermined spaced intervals; an elongated strip
having a second mating surface complementary to and abutted against
said first mating surface such that the thickness of said strip and
said thin wall is substantially equal to or greater than the
thickness of said thick wall; a plurality of second, punched tube
receiving slots in said strip and located therein at said
predetermined intervals, said second tube receiving slots being
aligned with said first tube receiving slots; and a joint bonding
said element and said strip together.
14. The header of claim 13 wherein both said first and second
mating surfaces are flat.
15. The header of claim 13 wherein said joint is a brazed
joint.
16. The header of claim 13 wherein both said first and second
mating surfaces are flat, and said joint is a brazed joint.
17. The header of claim 16 wherein said first mating surface is
defined by the bottom of a groove formed in said exterior and said
strip is located in said groove.
18. The header of claim 13 wherein said passages are cylindrical
passages.
19. The header of claim 13 wherein said passages are
non-cylindrical passages.
20. The header of claim 13 wherein said tube slots are elongated in
the direction of elongation of said element.
21. The header of claim 13 including tabs on opposite sides of said
relief and deformed over opposite sides of said elongated
strip.
22. A high pressure heat exchanger comprising: at least one header
defined by an elongated tubular like element having a pair of
side-by-side longitudinally extending passages and a tube receiving
side, said element being a unitary structure having a relatively
thick wall partially surrounding said passages and a relatively
thin wall at said tube receiving side; a first mating exterior
surface defined by a relief at said relatively thin wall of said
element; a plurality of punched first tube receiving slots at said
first mating surface in fluid communication with said passages and
located at predetermined spaced intervals; an elongated strip
having a second mating surface complementary to and abutted against
said first mating surface such that the thickness of said strip and
said thin wall is substantially equal to or greater than the
thickness of said thick wall; a plurality of second, punched tube
receiving slots in said strip and located therein at said
predetermined intervals, said second tube receiving slots being
aligned with said first tube receiving slots; a joint bonding said
element and said strip together; a plurality of tubes, each of
flattened cross section, having their ends disposed within said
tube slots; and fins extending between and bonded to adjacent ones
of said tubes.
23. The heat exchanger of claim 22 wherein said fins are serpentine
fins.
24. The heat exchanger of claim 22 wherein both said first and
second mating surfaces are flat.
25. The heat exchanger of claim 22 wherein said first mating
surface is on the exterior of said element.
26. The heat exchanger of claim 22 wherein said joint is a brazed
joint.
27. The heat exchanger of claim 22 wherein both said first and
second mating surfaces are flat, said joint is a brazed joint.
28. The heat exchanger of claim 27 wherein said first mating
surface is defined by the bottom of a groove formed in said
exterior and said strip is located in said groove.
29. The heat exchanger of claim 22 wherein said passages are
cylindrical passages.
30. The heat exchanger of claim 22 wherein said passages are
non-cylindrical passages.
31. The heat exchanger of claim 22 including tabs on opposite sides
of said relief and deformed over opposite sides of said elongated
strip.
32. The heat exchanger of claim 22 wherein said plurality of the
tubes comprises a first group of tubes having their ends disposed
within said tube slots in fluid communication with one of said
passages, and a second group of tubes having their ends disposed
within said tube slots in fluid communication with the other of
said passages.
33. The heat exchanger of claim 22 wherein each of said ends of
each of said plurality of tubes is notched with a first part on one
side of said notch disposed within said tube slots in fluid
communication with one of said passages, and a second part on the
other side of said notch disposed within said tube slots in fluid
communication with the other of said passages.
34. The heat exchanger of claim 22 wherein each of said tubes of
said plurality of tubes include a pair of parallel legs and a bend
joining said legs at a location remote from said at least one
header, one of said legs having an end disposed within said tube
slots in fluid communication with one of said passages, and the
other of said legs having another end disposed within said tube
slots in fluid communication with the other of said passages.
Description
FIELD OF THE INVENTION
[0001] This invention relates to headers for heat exchangers, and
more particularly, to headers and heat exchangers incorporating
such headers which are designed for extremely high pressure
applications.
BACKGROUND OF THE INVENTION
[0002] Concern for global warming and the deterioration of the
ozone layer as a result of the escape of fluorine containing
refrigerants from refrigeration systems, including air conditioning
systems, has prompted a new look at refrigeration systems utilizing
more environmentally friendly refrigerants. One such system under
study is a carbon dioxide (CO.sub.2) based system wherein CO.sub.2
is employed as the refrigerant. CO.sub.2 systems operate at
significantly higher internal pressure than do conventional systems
employing fluorine based refrigerants and as a consequence, there
is a need to improve the pressure resistance of heat exchangers
used in such applications as, for example, the gas cooler and the
evaporator of such systems.
[0003] At the same time, these systems have the potential for
extensive use in vehicular air conditioning systems where weight,
because of its impact on fuel economy, is of considerable concern.
This consideration makes it impossible to achieve the desired
pressure resistance simply by expanding wall thickness of
conventional heat exchangers used in such systems without other
major changes because of the added weight of thicker walled
elements. Furthermore, this solution is not an economically viable
one because taking existing components without changing their size
other than to increase wall thickness to achieve pressure
resistance means more material will have to go into the heat
exchanger, most notably in the headers, thereby increasing the cost
of the resulting heat exchanger.
[0004] Various solutions to this problem have been proposed. For
example, many of the heat exchangers employ tubular headers which
are generally cylindrical in shape. Conventional flattened tubes
have their ends fitted in tube slots in the headers, which tube
slots are transverse to the direction of elongation of the header.
It has been proposed to reduce the diameter of the header and
reorient the tube slots so that they are elongated in the direction
of elongation of the header. The tubes are then provided with a
twist near where their ends enter the header so as to present a
desired orientation of the tubes for air flow between the tubes
through the heat exchanger.
[0005] One primary difficulty in this approach is that with smaller
diameter headers, the process of forming the tube slots in the
headers has become increasingly difficult. In order to have a
desired wall thickness in the smaller diameter headers, it has been
necessary to form the tube slots by machining procedures as, for
example, by milling. Unfortunately, these machining operations are
time consuming and expensive and are particularly more costly than
the various punching techniques that have been used to form
transverse tube slots in cylindrical headers in conventional heat
exchangers utilizing conventional refrigerants.
[0006] Thus, there is a real need for a less costly header for use
in high pressure heat exchangers, such as those used as condensers,
gas coolers and/or evaporators in high pressure refrigeration
systems. The present invention is directed to meeting that
need.
SUMMARY OF THE INVENTION
[0007] It is the principal objects of the invention to provide a) a
new and improved method for making a header for a high pressure
heat exchanger, b) a new and improved header with high pressure
resistance for use in high pressure heat exchangers, and c) a new
and improved heat exchanger having improved pressure resistance
enabling it to function in a high pressure system as, for example,
a high pressure refrigeration system such as a CO.sub.2
refrigeration system.
[0008] According to one facet of the invention, there is provided a
method of making a high pressure resistant header for a heat
exchanger which includes the steps of a) providing an elongated
header structure including a pair of side-by-side longitudinally
extending passages, the passages surrounded by a wall of sufficient
thickness to resist deformation when a fluid is placed within the
passages at an operating pressure at which deformation is to be
resisted, b) thinning the wall along its length by providing a
first mating exterior surface on a part thereof so that the wall,
at the first mating surface is sufficiently thin that tube slots
may be formed therein by punching as opposed to more expensive
machining procedures, c) punching tube slots at predetermined
spaced intervals of the wall at the first mating surface, d)
providing an elongated strip having a second mating surface
complimentary to the first mating surface and of a thickness such
that the combined thickness of the strip and the wall at its first
mating surface is about equal to or greater than the desired
thickness of the wall, e) punching tube slots in the strip at the
predetermined spaced intervals, f) abutting the second mating
surface of the strip to the first mating surface of the header
structure with the tube slots in each being aligned with one
another and g) thereafter bonding the strip to the header structure
along their respective lengths to provide a unitary header with
tube slots therein.
[0009] In a preferred embodiment, both of the mating surfaces are
flat surfaces.
[0010] A preferred embodiment also contemplates that steps a) and
b) are performed simultaneously by extrusion of the header
structure.
[0011] In one embodiment, step b) is performed by providing a strip
receiving groove in that part of the header structure exterior
surface and the groove has a flat bottom surface defining the first
mating surface.
[0012] According to another aspect of the invention, a header for a
high pressure heat exchanger is provided. The header includes an
elongated tubular like element having a pair of side-by-side
longitudinally extending passages, and a tube receiving side. The
element is a unitary structure and has a relatively thick wall
partially surrounding the passage and a relatively thin wall at the
tube receiving side. A first exterior mating surface defined by a
relief is located at the relatively thin wall of the element and a
plurality of punched first tube receiving slots are located at the
first mating surface and are in fluid communication with the
passage and are located at predetermined spaced intervals. An
elongated strip having a second mating surface complementary to and
abutted against the first mating surface is provided such that the
thickness of the strip and the thin wall is substantially equal to
or greater than the thickness of the thick wall. A second plurality
of tube receiving slots are located in the strip and are punched
therein and located at the same predetermined intervals as the tube
slots in the first mating surface. They are aligned with the first
tube receiving slots. A joint is provided that bonds the element
and the strip together.
[0013] Preferably, the joint is a brazed joint.
[0014] According to still another facet of the invention, a high
pressure heat exchanger is provided and includes a header as
described previously. A plurality of tubes, each of flattened cross
section, are provided and have their ends disposed within
corresponding ones of the tube slots.
[0015] In one form, the ends of the tubes are twisted about
90.degree. to the remainder of the corresponding tube and fins
extend between and are bonded to adjacent ones of the remainders of
the tubes.
[0016] Preferably, the fins are serpentine fins.
[0017] Other objects and advantages will become apparent from the
following specification taken in connection with the accompanying
drawings.
DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is an elevational view of a heat exchanger made
according to the invention;
[0019] FIG. 2 is a cross-section of one embodiment of a header made
according to the invention;
[0020] FIG. 3 is a plan view of a header made according to the
invention;
[0021] FIG. 4 is a plan view of a strip that is applied to the
header element shown in FIG. 3 to form a header made according to
the invention;
[0022] FIG. 5 is a cross-section of a modified embodiment of the
header;
[0023] FIG. 6 is a cross-section of still another modified
embodiment;
[0024] FIG. 7 is a cross-section of another embodiment of a header
made according to the invention;
[0025] FIG. 8 is a cross-section of still another embodiment of a
header made according to the invention; and
[0026] FIG. 9 is a view similar to FIG. 7, but showing an alternate
tube construction for use with the header;
[0027] FIG. 10 is a cross-section of still another embodiment of
the invention in a condition just prior to final assembly prior to
brazing; and
[0028] FIG. 11 is a cross-section of the embodiment of FIG. 10 at a
subsequent step in its assembly and prior to brazing.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0029] A heat exchanger made in accordance with the invention is
illustrated in FIG. 1 and will be described in the context of a
refrigeration system. However, the invention, in each of its
facets, is applicable to high pressure heat exchangers, generally;
and no limitation to refrigeration systems is intended except as
set forth in the claims. The heat exchanger is seen to include
opposed, spaced headers 10 and 12. The headers 10 and 12 are
tubular as will be seen hereinafter and receive the ends 14 of
straight flattened tubes 16. The ends 14 are in fluid communication
with the interior of the headers 10, 12 and spaced from one
another. Alternatively, the headers 10, 12 could be closely
adjacent to one another with U-shaped flattened tubes (not shown)
placed in fluid communication with the interiors of the headers 10,
12.
[0030] Fins 18, preferably serpentine fins, extend between and are
bonded to adjacent ones of the tubes 16 intermediate between the
ends 14.
[0031] The tubes 16 are flattened tubes and between the ends 14,
have their major dimension running from front to back of the heat
exchanger. That is to say, the fins 18 are bonded to the sides of
the tubes 16 along their major dimensions. The minor dimension
faces forward to minimize the obstruction to air flow imposed by
the tubes 16 themselves.
[0032] Adjacent to the ends 14, the tubes 16 include a twist 20
allowing the ends 14 to be inserted into tube slots (not shown in
FIG. 1) that are elongated and extend in the direction of
elongation of the headers 10, 12. In the usual case, the twist 20
will be 90.degree., although other angles could be employed if
desired.
[0033] One of the headers 10 may be provided with an inlet
schematically indicated by an arrow 22 while the opposite header is
provided with an outlet, schematically illustrated by an arrow 24.
Of course, in some instances, the heat exchanger may be a so-called
multi-pass heat exchanger, in which case baffles to direct the flow
back and forth between the headers 10, 12 at least once may be
provided. When the number of passes is an even number, both the
inlet 22 and the outlet 24 will be in the same header 10, 12
whereas, for a single pass heat exchanger, or a multiple pass heat
exchanger having an odd number of passes, the inlet 22 and outlet
24 will be in different ones of the headers 10, 12. Moreover, if
desired, a multiple row heat exchanger could be made using a
plurality of the structures shown in FIG. 1 in stacked relation
with the headers 10 and/or 12 connected by manifolds which in turn
can be baffled as well to provide any desired flow circuit.
[0034] Turning now to FIGS. 2-4, the headers 10, 12 will be
described. As both are identical to each other, only the header 10
will be described in detail, it being understood that the same
description applies to the header 12.
[0035] As seen in FIG. 2, the header 10 is a cylindrical tube 26
having a central, cylindrical bore 28 which serves as a passageway
for one of the heat exchange fluids used with the heat exchanger.
The header 10 has a relatively thick walled portion 30 and a
relatively thin walled portion 32. The thick walled portion 30 is
provided with a thickness sufficient to withstand, without
deformation, the typical operating pressures encountered within the
passage 28 during operation of the heat exchanger within a
refrigeration system, plus an appropriate safety factor. The thin
walled portion 32, at its thinnest point, has a thickness about
half of that of the thick walled portion 30; and this thickness is
such that a series of elongated tube slots 34 may be provided in
the thin walled portion by a simple punching operation. In the
embodiment illustrated in FIG. 2, the thin walled portion 32 is
defined by the flat bottom 36 of a relief in the form of a groove
38 formed along the length of the header 10. The bottom 36 serves
as a first mating surface and typically will be flat but may take
on other configurations if desired.
[0036] According to the invention, an elongated strip 40 is bonded
in the groove 38 as by brazing or soldering. To this end, the strip
40 typically will be braze clad. Such bonds are generically
referred to herein as metallurgical bonds. The strip 40 has a
plurality of elongated tube receiving slots 42 which are preferably
of the same size and shape as the slots 34 in the header 10. They
are also located at the same predetermined intervals as the slots
34. Thus, the elongated strip 40 may be inserted within the groove
38 and the tube slots 34 and 42 aligned with one another
preliminary to forming the aforementioned metallurgical bond. While
it is preferred that the slots 42 be of the same size and shape as
the slots 34 in the header 10, in some applications it may be
desirable for one set of the slots 34 or 42 to be of a size and
shape suitable for receiving and forming a suitable bond joint with
the ends 14 of the tubes and the other of the set of slots 34 or 42
being of a different size and/or shape that will not necessarily be
suitable for forming a bond joint with the ends 14 of the tube
16.
[0037] The strip 40 has a flat surface 44 which is a second mating
surface to mate with the bottom 36 of the groove 38. When other
than flat surfaces are used as the bottom of the groove 36, the
surface 44 will be configured to be complementary to the shape of
the bottom 36 of the groove 38.
[0038] The strip 40 has a thickness approximately equal to or
greater than half the thickness of the thick walled portion 30 of
the header 10, or vice versa, so that the tube slots 42 may be
formed therein by a simple punching operation. When assembled as
illustrated in FIG. 2, the minimum total thickness of the header 10
at its thin walled portion 32 and the strip 40 will be equal to or
exceed the thickness of the thick walled portion 30 of the
remainder of the header.
[0039] In the usual case, aluminum will be utilized as the material
for forming both the header 10 and the strip 40 because of its
light weight so as to minimize the mass of the heat exchanger in
which the header is used. However, other materials could be
utilized if desired.
[0040] Significantly, the thickness of the thin walled portion 32
and the strip 40 are both chosen so that the tube slots 34, 42 may
be punched in the respective elements 10, 40, rather than requiring
forming by machining operations such as milling. As a result, the
resulting tube slots, which are a combination of the slots 34 and
42, may be inexpensively formed thereby reducing the cost of the
resulting header.
[0041] In a preferred embodiment, the headers 10 are formed by
extrusion although it is possible to form them by other means as,
for example, roll forming out of a strip of suitable material.
[0042] Typically, the headers 10 will have their thin walled
portion 32 on the exteriors thereof for ease of application and
alignment of the strip 40 thereto. However, it is possible to
provide the relatively thin area 32 on the interior of the header,
that is, as part of the inner wall defining the passage 28.
[0043] FIG. 5 shows an alternative embodiment where the header 10
is formed with a cross-section of a semi oval having sides
terminating at points 50. In the embodiment of FIG. 5, the thin
walled portion is located between the sides 50 and again is in the
form of a relief provided by a groove 38 for receipt of a strip 40.
The relative dimensions are the same as mentioned previously and
therefore allow punching of the tube slots 34, 42 in both the
header 10 and the strip 40. The header 10 and the strip 40 are, of
course, metallurgically bonded to one another as mentioned
previously.
[0044] FIG. 6 illustrates still another embodiment of the header 10
and again one wherein its cross-section is that of a semi oval. In
this case, the groove 38 is not formed in favor of a simple, planar
surface 52 serving as a relief extending between the ends 50 of the
semi oval. In this case, a somewhat wider strip 40 may be employed
to extend from one side 50 to the other of the header semi oval
shape.
[0045] Again, the arrangement is such that a thin walled portion 32
is provided to be covered by the strip 40.
[0046] In general, the embodiments shown in FIGS. 2 and 5 are
preferred in that the groove 38 provides for ease of positioning of
the strip 40. And of those two, the embodiment illustrated in FIG.
2 is preferred because, as a comparison of the cross-sections of
each of the embodiments illustrated in FIGS. 2, 5 and 6 will show,
less material is required to form the embodiment illustrated in
FIG. 2 than either of the others, thereby assuring a minimum of
cost.
[0047] It is also preferred that the tube slots 34 and 42 be
elongated, thereby accommodating the use of flattened tubes such as
the tube 16. It is also preferred that the direction of elongation
of the tube slots 34 and 42 be in the direction of elongation of
the headers 10 and 12 as this allows a reduction in the diameter of
both the passage 28 and the header 10,12. This reduction in
diameter in turn allows the use of a thinner walled header 10, even
at its relatively thick portion 30 while still meeting pressure
resistance requirements for a system. It also minimizes the amount
of material employed, all the while allowing the use of a fairly
generous major dimension in the tubes 16.
[0048] By way of example, the embodiment illustrated in FIG. 2 may
be made of a header having an outer diameter approximately 0.500
inches and with a diameter of the passage 28 of 0.25 inches. This
provides a wall thickness of 0.125 inches for the relatively thick
portion 30. The groove 38 may have a depth of about 0.062 inches
while the strip 40 may have a thickness of 0.063 inches. The width
of the strip 40 may also be approximately 0.250 inches.
[0049] In general, it is desirable that the thin walled portion 32,
at its thinnest, be equal to approximately one-half the wall
thickness of the header 10 and that the strip 40 have the same
approximate thickness. When this is done, the ability to
satisfactorily punch the tube slots 34 and 42 is maximized because
both the thin walled portion 32 and the strip 40 will be at minimum
thickness to facilitate punching.
[0050] FIGS. 7 and 8 show still a further modification of the
invention. In the interest of brevity, the components common to the
embodiment of FIG. 2 are given like reference numerals and will not
be redescribed but it should be understood that previously
described features of these components apply equally to the
embodiments of FIGS. 7 and 8. In these embodiments, a pair of
side-by-side bores or passages 54 are provided rather then a single
cylindrical bore 28 as in FIG. 2. FIG. 7 illustrates the bores 54
as being cylindrical, whereas FIG. 8 shows the bores 54 as being
non-cylindrical. The headers 10 of FIGS. 7 and 8 are desirable for
use in multiple row heat exchanger having two rows of the tubes 16
(as shown in FIG. 7), rather than a single row of the tubes 16 as
it has been previously described.
[0051] Each of the bores 54 has a set of the tube slots 34 and a
set of tube slots 42 associated with the bore 54. It follows that
the strip 40 has two sets of the slots 42, one set aligned with one
of the bores 54 and the other set aligned with the other bore 54.
For purposes of illustration, each of the tubes 16 is shown with
its major dimension extending transverse to the longitudinal axis
of the associated bore 54. However, it should be understood that in
some applications it may be desirable for the major dimensions to
extend parallel to the longitudinal axis of the associated bore
54.
[0052] A pair of the headers 10 of either FIGS. 7 and 8 can be
provided in spaced, parallel relation, as shown for the headers in
FIG. 1, with two rows of the tubes 16 extending between them, or
each of the tubes 16 can be provided with a bend portion 55 remote
from a single one of the headers 10 of FIG. 7 or 8 such that the
two rows are formed from parallel legs 56 of the same tube with the
ends of the tube 16 being received in a single one of the headers
10, as shown in FIG. 9. As yet another alternative, a single row of
flattened tubes 16 having relatively large major dimensions can be
used with either of the headers 10 of FIGS. 7 and 8, with a notch
57 provided in the end of the tube and portions 58 and 59 located
on opposite sides of the notch 57 being received in respective ones
of the tube slots 34,42 in fluid communication with respective ones
of the bores 54.
[0053] FIGS. 10 and 11 show still a further modification of the
invention. It is illustrated in the context of the embodiment
illustrated in FIG. 2, but it will be readily appreciated that it
is applicable to the embodiment of FIG. 5 as well. In the interest
of brevity, the components common to the embodiment of FIG. 2 are
given like reference numerals and will not be redescribed. In this
embodiment, the groove 38 is flanked by tabs 60 along its length.
As seen in FIG. 10, the ends 62 of the tabs extend beyond the
radially outer side 64 of the strip 40 such that strip 40 nests
within the groove 38 inwardly of the end 62 of the tabs 60. As seen
in FIG. 11, the ends 62 of the tabs 60 may be crimped or otherwise
deformed over the ends of the radially outer surface 64. This
crimping may be along the entire length of the tabs 60 or may occur
intermittently at desired locations along their length. In any
event, the tabs 60, and specifically their ends 62 provide
self-fixturing of the header tube assembly during brazing.
[0054] It is to be particularly noted that while the foregoing
description is made with reference to the embodiment illustrated in
FIG. 2, it is equally applicable to the embodiment illustrated in
FIG. 5 and could actually even be employed with the embodiment of
FIGS. 6, 7 and 8 if the width of the strip 40 were slightly reduced
in the tabs placed on opposed sides of the surface 52. This
structure assures that the strip 40 is firmly held within the notch
36 during brazing to assure a leak-free interface between the tube
10 and the strip 40.
[0055] From the foregoing, it will be appreciated that the
invention can provide a low cost, low mass header for volume
production in systems such as CO.sub.2 refrigeration systems having
minimum burst pressures of about 6,500 psi or more. The invention
allows the use of a one step punching operation for each of the
headers and the strips and thus eliminates the currently required
milling process for forming tube slots and headers of the
thicknesses of concern.
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