U.S. patent application number 10/652768 was filed with the patent office on 2005-03-03 for concentric tube heat exchanger and end seal therefor.
Invention is credited to Brown, Alan, Seager, James R., So, Allan K., Watson, Darryl S..
Application Number | 20050045315 10/652768 |
Document ID | / |
Family ID | 34436133 |
Filed Date | 2005-03-03 |
United States Patent
Application |
20050045315 |
Kind Code |
A1 |
Seager, James R. ; et
al. |
March 3, 2005 |
Concentric tube heat exchanger and end seal therefor
Abstract
A concentric tube heat exchanger comprises an outer tube and a
concentric inner tube, with an annular passageway between the
tubes. The ends of the annular passageway are sealed by sealing
members having axially extending inner and outer walls which are
connected to one another and which are sealed to the respective
outer and inner tubes. The sealing member walls are preferably
connected by an integrally formed connecting wall. The walls of the
sealing member are preferably resilient and diverge so as to form a
friction fit with the tubes during assembly of the heat exchanger.
The heat exchanger further comprises a turbulizer which comprises a
plurality of rows of corrugations defining axially extending flow
passages. Preferably, the corrugations have a top land width
greater than a bottom land width so that the side walls of the
corrugation are radially arranged in the annular passageway.
Adjacent corrugations in each row are preferably offset relative to
one another by an amount of from about 30 percent to about 40
percent.
Inventors: |
Seager, James R.; (Guelph,
CA) ; So, Allan K.; (Mississauga, CA) ; Brown,
Alan; (Cambridge, CA) ; Watson, Darryl S.;
(Brantford, CA) |
Correspondence
Address: |
Dykema Gossett PLLC
Suite 300
39577 Woodward Avenue
Bloomfield Hills
MI
48304
US
|
Family ID: |
34436133 |
Appl. No.: |
10/652768 |
Filed: |
August 29, 2003 |
Current U.S.
Class: |
165/154 |
Current CPC
Class: |
F28D 7/106 20130101;
F28F 2230/00 20130101; F28F 9/0234 20130101; F28F 9/0202
20130101 |
Class at
Publication: |
165/154 |
International
Class: |
F28D 007/10 |
Claims
What is claimed is:
1. A concentric tube heat exchanger having a first end and a second
end, the heat exchanger comprising: (a) an outer tube; (b) an inner
tube received inside the outer tube and concentric therewith,
wherein an annular passageway is formed between the inner and outer
tubes; (c) first and second annular sealing members received inside
the annular passageway between the inner and outer tubes, the first
sealing member being positioned proximate the first end of the heat
exchanger and the second sealing member being positioned proximate
the second end of the heat exchanger, each of the sealing members
comprising an outer wall and an inner wall which are connected to
one another, each of the walls having first and second
axially-spaced ends, the outer wall being sealed to the outer tube
and the inner wall being sealed to the inner tube, thereby sealing
the ends of the tubes.
2. The concentric tube heat exchanger of claim 1, wherein each of
the sealing member walls has an axially-extending portion between
its first and second end.
3. The concentric tube heat exchanger of claim 1, wherein the inner
and outer walls of the sealing members are connected through a
connecting portion which seals a radial space between the sealing
member walls.
4. The concentric tube heat exchanger of claim 3; wherein the
sealing members are generally U-shaped, with the first ends of the
sealing member walls being connected to the connecting portion and
the second ends of the sealing member walls being distal to the
connecting portion.
5. The concentric tube heat exchanger of claim 1, wherein the
sealing members are spaced inward from the ends of the heat
exchanger, such that the second ends of the sealing member walls
are proximate to, and spaced inwardly from, the ends of the heat
exchanger.
6. The concentric tube heat exchanger of claim 5, wherein the
sealing members are brazed to the tubes such that fillets of filler
metal are formed between the tubes and the ends of the sealing
member walls, and wherein the sealing members are spaced inwardly
from the ends of the heat exchanger by a distance sufficient that
the fillets between the second ends of the sealing member walls and
the tubes are located inwardly of the ends of the heat
exchanger.
7. The concentric tube heat exchanger of claim 3, wherein the
connecting portion is rounded.
8. The concentric tube heat exchanger of claim 3, wherein the
connecting portion is flat.
9. The concentric tube heat exchanger of claim 1, wherein the tubes
and the sealing members are comprised of aluminum.
10. The concentric tube heat exchanger of claim 9, wherein the
tubes are provided with a cladding comprised of a brazing alloy, at
least on surfaces which are joined to the sealing members.
11. The concentric tube heat exchanger of claim 10, wherein the
sealing members are provided with a cladding comprised of a brazing
alloy, at least one surfaces which are joined to the tubes.
12. The concentric tube heat exchanger of claim 1, further
comprising a turbulizer received in the annular passageway, the
turbulizer comprising a plurality of corrugations defining a
plurality of axially extending flow passages extending parallel to
the tubes, each of the corrugations comprising a top land, a bottom
land and a pair of side surfaces connecting the top and bottom
lands, the top land being in heat exchange contact with the outer
tube and the bottom land being in heat exchange contact with the
inner tube; wherein the convolutions are arranged in axially
extending rows with the convolutions in each row being connected to
one another and with an offset being provided between adjacent
convolutions in each row, the offset having a width which is from
about 30 percent to about 40 percent of a width of the top land or
the bottom land.
13. The concentric tube heat exchanger of claim 12, wherein the
width of the offset is from about 31 percent to about 36 percent of
the top land width or the bottom land width.
14. The concentric tube heat exchanger of claim 13, wherein the
width of the offset is about 31 percent of the top land width.
15. The concentric tube heat exchanger of claim 13, wherein the
width of the offset is about 36 percent of the bottom land
width.
16. The concentric tube heat exchanger of claim 13, wherein the top
land width is greater than the bottom land width and wherein the
side surfaces extend radially between the inner and outer
tubes.
17. The concentric tube heat exchanger of claim 13, wherein the
tubes and the turbulizer are comprised of aluminum with the top
land being brazed to the outer tube and the bottom land being
brazed to the inner tube.
18. A sealing member for sealing opposite ends of an annular
passageway extending along an axis between inner and outer tubes of
a concentric tube heat exchanger, the sealing member comprising: an
outer wall having first and second axially-spaced ends and having a
generally axially-extending portion between its ends for sealing to
the outer tube; and an inner wall having first and second
axially-spaced ends, the inner wall being connected to the outer
wall and being spaced radially inwardly of the outer wall, the
inner wall having a generally axially-extending portion between its
ends for sealing to the inner tube; wherein the generally
axially-extending portions of the walls diverge from one another
along said axis.
19. The sealing member of claim 18, wherein the inner and outer
walls are connected through a connecting portion, the second ends
of the sealing member walls are axially spaced from the connecting
portion, the generally axially-extending portions of the sealing
member walls extend between the connecting portion and the second
end, and wherein the generally axially-extending portions diverge
from said connecting portion to the second ends of the sealing
member walls.
20. The sealing member of claim 18, wherein the generally
axially-extending portions of the walls are resilient, and wherein
the generally axially-extending portions diverge from one another
at an angle such that, during assembly, the sealing members are
slidably received in the annular passageway with the outer wall
frictionally engaging the outer tube and the inner wall
frictionally engaging the inner tube, and such that the generally
axially-extending portions of the sealing member walls are in
substantial engagement with the inner and outer tubes.
21. The sealing member of claim 18, wherein the generally
axially-extending portion of at least one of the sealing member
walls diverges from the axis by an angle of from about 1 to about 2
degrees.
Description
FIELD OF THE INVENTION
[0001] This invention relates to concentric tube heat exchangers,
and more particularly to seals for closing an annular passageway
between the inner and outer tubes of such heat exchangers.
BACKGROUND OF THE INVENTION
[0002] Concentric tube heat exchangers are commonly employed as
transmission and transaxle oil coolers and are mounted in the
coolant tank or manifold of a vehicle radiator. These heat
exchangers include a cylindrical outer tube, a cylindrical inner
tube and a turbulizer placed in an annular passageway between the
inner and outer tubes. Oil is admitted to the annular passageway
via an inlet port located at one end of the tube for passage
through the turbulizer. The oil is cooled and exits via an outlet
port located near the other end of the outer tube.
[0003] Numerous arrangements are known in the prior art for sealing
the ends of the annular passageway. These include deformation of
the inner and/or outer tubes, for example as shown in U.S. Pat. No.
3,001,767 (Straubing), U.S. Pat. No. 5,732,769 (Staffa) and U.S.
Pat. No. 5,950,716 (Appelquist et al.); or by use of annular seals
as described in U.S. Pat. Nos. 3,323,586 and 3,339,260 (Burne et
al.)
[0004] The suitability of prior art end sealing methods can be
affected by the type of material from which the heat exchanger is
made. For example, in aluminum concentric tube heat exchangers, it
has proven difficult to seal the annular passageway by deformation
of the tubes. This has led some manufacturers to seal the annular
passageway with machined aluminum end blocks, which significantly
increase the weight and cost of the heat exchanger.
[0005] Accordingly, there is a need for improved methods for
sealing the annular passageway in a concentric tube heat exchanger
which will provide economical and reliable sealing in a variety of
materials.
SUMMARY OF THE INVENTION
[0006] In one aspect, the present invention provides a concentric
tube heat exchanger having a first end and a second end. The heat
exchanger comprises an outer tube and an inner tube. The inner tube
is received inside the outer tube and concentric therewith, wherein
an annular passageway is formed between the inner and outer tubes.
The heat exchanger further comprises first and second annular
sealing members received inside the annular passageway between the
inner and outer tubes. The first sealing member is positioned
proximate the first end of the heat exchanger and the second
sealing member is positioned proximate the second end of the heat
exchanger. Each of the sealing members comprises an outer wall and
an inner wall which are connected to one another, each of the walls
having first and second axially-spaced ends, the outer wall being
sealed to the outer tube and the inner wall being sealed to the
inner tube,. thereby sealing the ends of the tubes.
[0007] The concentric tube heat exchanger according to the
invention further comprises a turbulizer received in the annular
passageway between the tubes. The turbulizer comprises a plurality
of corrugations defining a plurality of axially extending flow
passages extending parallel to the tubes. Each of the corrugations
comprises a top land, a bottom land and a pair of side surfaces
connecting the top and bottom lands, the top land being in heat
exchange contact with the outer tube and the bottom land being in
heat exchange contact with the inner tube. The convolutions are
arranged in axially extending rows with the convolutions in each
row being connected to one another and with an offset being
provided between adjacent convolutions in each row. The offset has
a width which is from about 30 percent to about 40 percent of a
width of the top land or the bottom land.
[0008] In another aspect, the present invention provides a sealing
member for sealing opposite ends of an annular passageway extending
along an axis between inner and outer tubes of a concentric tube
heat exchanger. The sealing member comprises an outer wall and an
inner wall. The outer wall has first and second axially-spaced ends
and a generally axially-extending portion between its ends for
sealing to the outer tube. The inner wall has first and second
axially-spaced ends, is connected to the outer wall and is spaced
radially inwardly of the outer wall. The inner wall has a generally
axially-extending portion between its ends for sealing to the inner
tube. The generally axially-extending portions of the walls diverge
from one another along said axis.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The invention will now be described, by way of example only,
with reference to the accompanying drawings, in which:
[0010] FIG. 1 is a perspective view of a preferred heat exchanger
according to the invention, prior to insertion of the sealing
members;
[0011] FIG. 2 is a cross section through one of the sealing members
along line II-II in FIG. 1;
[0012] FIGS. 3A to 3D are cross sections through alternate
preferred sealing members according to the invention;
[0013] FIG. 4 is a cross section in an axial plane through one end
of the heat exchanger of FIG. 1, after insertion of the sealing
members;
[0014] FIG. 5 is a close-up of area A in FIG. 4;
[0015] FIG. 6 is a cross-section along line VI-VI of FIG. 1;
[0016] FIG. 7 is a front view of a portion of a turbulizer sheet
according to the invention; and
[0017] FIG. 8 is a top plan view of a portion of the turbulizer
sheet of FIG. 7.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0018] FIG. 1 illustrates a preferred concentric tube heat
exchanger 10 according to the invention. Heat exchanger 10
comprises an outer cylindrical tube 12 and an inner cylindrical
tube 14, the inner tube 14 being received in the outer tube 12 and
concentric therewith, with an annular passageway 16 being formed
between the outer and inner tubes 12, 14 and extending through
substantially the entire length of the heat exchanger 10.
[0019] Heat exchanger 10 further comprises an inlet port 18 located
adjacent its first end 20 and an outlet port 22 (FIG. 6) located
adjacent its second end 24. Both the inlet and outlet ports 18, 22
comprise perforations formed in the outer tube 12 through which a
fluid to be cooled, such as oil, is allowed to enter and exit the
annular passageway 16. The heat exchanger 10 further comprises an
inlet fitting 26 and an outlet fitting 28 which are mounted to the
outer surface of the outer tube 12 in communication with the inlet
and outlet ports 18, 22 respectively. To assist in mounting and
sealing the fittings 26, 28 to outer tube 12, the areas surrounding
inlet and outlet ports 18, 22 are preferably flattened, as shown in
FIG. 6. Sealed connections are formed between fittings 26, 28 and
the outer surface of tube 12, for example by brazing.
[0020] Not shown in FIG. 1, but described in detail below, is a
turbulizer 30 which is received in the annular passageway 16 and
extends through the annular passageway 16 between the inlet and
outlet ports 18, 22.
[0021] Lastly, the heat exchanger 10 comprises a pair of annular
sealing members 32 for sealing the ends of the annular passageway
16. In FIG. 1, the heat exchanger 10 is shown in a partially
disassembled state with the sealing members 32 separated from the
tubes 12, 14. FIG. 4 illustrates the first end of heat exchanger 10
in its assembled state with a sealing member 32 received in the
annular passageway 16 and brazed to both the outer and inner tubes
12, 14.
[0022] As shown in FIG. 4, sealing member 32 is received inside the
annular passageway 16 between the outer and inner tubes 12, 14. The
sealing member 32 is located proximate the first end 20 of heat
exchanger 10 and, more particularly, is located between the inlet
port 18 and the first end 20 of the heat exchanger 10. The sealing
member 32 is sealingly connected to both the inner surface of the
outer tube 12 and the outer surface of the inner tube 14,
preferably by brazing, with braze fillets 34 and 36 being formed
between the sealing member 32 and the outer tube 12, and braze
fillets 38 and 40 being formed between the sealing member 32 and
the inner tube 14. The braze fillets 34, 36, 38 and 40 are shown
only in the close-up of FIG. 5. It will be appreciated that the
second end 24 of heat exchanger 10 is preferably sealed in an
identical manner with the other sealing member 32 illustrated in
FIG. 1.
[0023] The preferred sealing members 32 shown in the drawings each
comprise an outer wall 42 and an inner wall 48, with the inner wall
48 being spaced radially inwardly of the outer wall 42, and
preferably concentric therewith. The outer wall 42 has a first end
46 and a second end 44, the ends 44, 46 being axially spaced from
one another, with at least a portion of the outer wall extending
generally along the axis. Similarly, the inner wall has a first end
52 and a second end 50, the ends 50, 52 being axially spaced from
one another, with at least a portion of the outer wall extending
generally along the axis. In the sealing members 32 shown in the
drawings, the entire outer and inner walls 42 and 46 extend along
the axis, with the inner wall 48 abutting the outer surface of
inner tube 14 and sealed thereto, and with the outer wall 42
abutting the inner surface of outer tube 12 and sealed thereto.
However, it will be appreciated that this is not necessary that the
entire outer and inner walls 42, 48 extend generally axially.
Rather, it will be appreciated that only portions of walls 42, 46
are required to extend axially, sufficient to form seals with the
outer and inner tubes 12, 14, respectively.
[0024] The sealing members 32 illustrated in the drawings are of
generally U-shaped cross section, with the first end 46 of the
outer wall 42 being connected to the first end 52 of the inner wall
48 by a radially extending connecting portion 54 which seals the
radial space between the walls 42, 48. The second ends 44, 50 of
the walls 42, 48 are distal to the connecting portion. Preferably,
the connecting portion 54 is integrally formed with the walls 42,
48.
[0025] As shown in FIG. 2, the outer and inner walls 42, 48 of the
sealing member are not necessarily parallel to one another. Rather
it is preferred that the walls 42, 48, or the generally axially
extending portions thereof, diverge from one another along the
axis. Preferably, the walls 42, 48 diverge from one another from
the connecting portion 54 toward the second ends 44, 50 such that a
radial distance measured between the walls 42, 48 at the connecting
portion 54 is less than a radial distance measured between the
second ends 44, 50 of walls 42, 48. Furthermore, the material from
which the walls 42, 48 are formed is preferably sufficiently
resilient such that, when the sealing members 32 are inserted into
the annular passageway with the connecting portions 54 spaced
inwardly of the ends 20, 24 by a greater distance than the second
ends 44, 50 of walls 42, 48 (as shown in FIG. 4), the second ends
44, 50 become compressed so that the sealing member walls 42, 48
frictionally engage the respective tubes 12, 14, thereby retaining
the sealing members 32 during the assembly process. The angle at
which the walls 42, 48 diverge is sufficient for easy insertion of
the sealing members 32 into the annular passageway 16 with a
friction fit, while ensuring substantially complete contact between
the walls 42, 48 and the tubes 12, 14 after the inner tube is
expanded during the manufacturing process, thus ensuring leak-proof
braze joints. The inventors have found that these objects can be
achieved by forming sealing members with at least one, and
preferably both, side walls 42, 48 diverging from the axis by an
angle .theta. of from about 1 to about 2 degrees, more preferably
about 1.5 degrees.
[0026] As shown in FIG. 4, the sealing member 32 is preferably
spaced inwardly from the end 20 of the heat exchanger 10, for at
least two reasons. Firstly, it will be noted from FIG. 4 that the
turbulizer 30 does not extend past the inlet port 18 and, in fact,
is prevented from doing so by a collar 56 of inlet fitting 26, the
collar 56 projecting into the annular passageway 16 through the
inlet port 18 and acting as a stop for the turbulizer 30. Thus, the
turbulizer 30 does not provide support for the portion of annular
passageway 16 extending from the inlet port 18 to the first end 20
of the heat exchanger 10. To minimize the unsupported area of
annular passageway 16 and thereby avoid narrowing of the annular
passageway 16 in the area surrounding inlet port 18, the sealing
member 32 is located inwardly of the end 20 of heat exchanger 10,
between the inlet port 18 and the end 20. Secondly, locating the
sealing member inward of the end 20 ensures that there is
sufficient area for formation of braze fillets 34 between the top
44 of outer wall 42 and the inner surface of outer tube 12, and
between the top 50 of inner tube 14 and the outer surface of inner
tube 14. The formation of continuous braze fillets about the entire
circumference of each sealing member ensures robust, leak proof
joints at the ends 20, 24 of the heat exchanger.
[0027] As shown in FIG. 2, the connecting portion 54 of the sealing
member is preferably flat and extends radially between the outer
and inner walls 42, 48 of the sealing member 32. FIG. 3A
illustrates an alternate preferred form of sealing member 58 having
outer and inner walls 60, 62 diverging from the axis by an angle
.theta. and connected at their bottoms by a rounded connecting
portion 64. It will also be appreciated that numerous alternate
constructions of sealing members are possible without departing
from the present invention. For example, as shown in FIG. 3B, a
sealing member 132 may be of generally H-shaped cross section, with
the connecting member 154 extending radially between the sealing
member walls 142, 148 intermediate the first ends 146, 152 and the
second ends 144, 150. Alternatively, FIG. 3C shows a sealing member
232 which is of generally V-shaped cross section, and in which a
V-shaped connecting member 254 extends between sealing member walls
242, 248, which extend generally axially. FIG. 3D shows a sealing
member 332 which is of modified U-shaped construction, having a
somewhat indented connecting portion 354 extending between the
outer and inner walls 342, 348.
[0028] In a particularly preferred embodiment of the present
invention, all the components of heat exchanger 10 are formed from
aluminum or alloys thereof, and are preferably formed from
brazeable aluminum alloys. In particular, the tubes 12, 14 are
preferably of welded and drawn construction and comprise an
aluminum alloy core layer clad on at least one side with an
aluminum brazing alloy. More preferably, the inner surface of the
outer tube 12 and the outer surface of the inner tube 14, i.e. the
"oil-side" surfaces, are clad with a brazing alloy, while the
opposite surfaces of these tubes, i.e. the "water-side" surfaces,
are clad with an alloy containing an amount of zinc for sacrificial
corrosion protection. Where the oil-side surfaces of tubes 12, 14
are clad with a brazing alloy, it will be appreciated that neither
the turbulizer 30 nor the sealing members 32 require a cladding of
brazing alloy. It will be appreciated that alternate arrangements
are possible, for example, the turbulizer 30 and sealing members 32
may be clad with brazing alloy, and the tubes 12, 14 may be unclad.
Alternatively, all these components may be clad with a brazing
alloy. In yet another alternative, the heat exchanger 10 may be
comprised of non-clad aluminum members, and the filler metal for
brazing may be provided by means of a brazing paste or preform, and
brazing can be accomplished by either flux or fluxless brazing by
suitable selection of the braze system and materials. Similarly, a
brazing paste or preform can be used to join the fittings 26, 28 to
the corrosion resistant clad water-side surface of the outer tube
12.
[0029] It will be appreciated that the sealing members 32 may be
installed with the second ends 44, 50 of walls 42, 48 facing the
inlet or outlet port 18, 22. However, for manufacturing purposes,
it is preferred that the sealing members 32 are received in the
annular passageway with the second ends 44, 50 of walls 42, 48
facing the ends 20, 24 of heat exchanger 10, as shown in the
drawings.
[0030] The heat exchanger 10 is preferably by assembled by
inserting the inner tube 14 and the turbulizer 30 into the outer
tube 12, inserting the sealing members 32 into the opposite ends 20
and 22, expanding the inner tube so that both the outer and inner
tubes 12, 14 are in intimate heat exchange contact with the
turbulizer 30, applying the fittings to the outer tube, and then
brazing the assembly in a brazing oven.
[0031] A preferred form of turbulizer 30 is now described below
with reference to FIGS. 7 and 8. Turbulizer 30 is of generally the
same construction as the turbulizer described in U.S. Pat. No. Re.
35,890 (So), which is incorporated herein by reference in its
entirety. In particular, prior to insertion into the annular
passageway 16, the turbulizer 30 is in the form of a sheet having a
plurality of convolutions 74 which define a plurality of flow
passages. The flow passages extend axially (parallel to arrow A in
FIG. 8) once the turbulizer 30 is rolled up and inserted into the
annular passageway 16. Each of the convolutions 74 has a height H
(FIG. 7), a length L (FIG. 8), a rectangular top land 76 having
width W.sub.T (FIGS. 7 and 8), a rectangular bottom land 78 having
a width W.sub.B, and a pair of side surfaces 80 extending between
the top and bottom lands 76, 78. In a particularly preferred
embodiment of the present invention, the convolutions 74 have a
height of about 3 mm and a length of at least about 1.6 mm. It will
be appreciated that all width dimensions described herein are
measured perpendicular to the axial direction.
[0032] The top lands 76 of the convolutions 74 are arranged in
axially extending rows, as seen in FIG. 8, which shows a single row
82 of convolutions 74. The top lands 76 of the convolutions 74 in
each row 82 are connected to one another along their front and rear
edges at areas 84 (FIG. 8) and are offset relative to one another,
with the width of the offset being W.sub.O (FIG. 8). It will be
appreciated that a bottom plan view of the turbulizer 30 has an
appearance which is substantially the same as that shown in FIG.
8.
[0033] The features of turbulizer 30 described above are also
present in the turbulizer described in the above-mentioned So
patent. The turbulizer 30 according to the invention differs from
the So turbulizer in several important respects, which are now
discussed below.
[0034] Firstly, the turbulizer 30 according to the invention has a
preferred offset W.sub.O which is significantly less than that of
the So turbulizer, thereby maximizing the width of the area 84
along which the convolutions 84 are connected with one another. In
the So turbulizer, the width of offset is about 50 percent of the
width of the top and bottom lands, whereas the offset in the
turbulizer 30 according to the invention is about 30 to 40 percent
(i.e. W.sub.O/W.sub.T or W.sub.B=0.30-0.40), preferably about 31 to
about 36 percent. The inventors have found that decreasing the
offset of the convolutions 74 helps to ensure formability of the
turbulizer 30 from metals such as aluminum, while providing high
heat transfer and low pressure drop.
[0035] Secondly, the turbulizer 30 according to the invention is
formed with the top land width W.sub.T which is greater than the
bottom land with W.sub.B, and with the side surfaces 80 of each
convolution 74 sloping away from one another from the top land 76
to the bottom land 78. Thus, when the turbulizer sheet 30 is rolled
up and inserted into the annular passageway 16 with the bottom
lands 78 in heat exchange contact with the inner tube 14 and the
top lands 76 in heat exchange contact with the outer tube 12, the
side surfaces 80 are extend substantially radially between the
outer tube 12 and inner tube 14, producing axial flow passages of
substantially constant cross-sectional area. This helps to maximize
heat transfer and minimize pressure drop.
[0036] In a particularly preferred embodiment of the invention, the
side surfaces are sloped at about 5.degree. from vertical, the top
land width W.sub.T is about 1.1 mm, the bottom land width W.sub.B
is about 1.0 mm, the centers of rows 82 are spaced about 2.1 mm
apart, and the offset with W.sub.O is about 0.35 mm. In a
turbulizer having these dimensions, the offset expressed as a
percentage of the top land width is about 31 percent and the offset
expressed as a percentage of the bottom land width is about 36
percent.
[0037] The above-mentioned features of the turbulizer according to
the invention, for example the top and bottom lands of different
width, the radially extending side surfaces, and the decreased
offset, ensure optimum fit-up of the turbulizer during assembly,
thereby maximizing metal-to-metal contact between the turbulizer
and the tubes, which ensures brazeability and optimum heat
transfer.
[0038] Although the invention has been described in connection with
certain preferred embodiments, it is not intended to be limited
thereto. Rather, the invention includes all embodiments which may
fall within the scope of the following claims.
* * * * *