U.S. patent application number 11/256783 was filed with the patent office on 2007-04-26 for 3-d dimpled heat exchanger.
This patent application is currently assigned to Lennox Manufacturing Inc.. Invention is credited to Mark G. Beste, David M. Wynnick.
Application Number | 20070089873 11/256783 |
Document ID | / |
Family ID | 37984275 |
Filed Date | 2007-04-26 |
United States Patent
Application |
20070089873 |
Kind Code |
A1 |
Beste; Mark G. ; et
al. |
April 26, 2007 |
3-D dimpled heat exchanger
Abstract
A heat exchanger apparatus comprising a frame, a tube coupled to
the frame, and turbulating structure disposed within the tube and
extending into an inner hollow space thereof for promoting
turbulent fluid flow within the tube. The turbulating structure
comprises elements located arcuately around an inner periphery of
the tube at approximately 120.degree. increments. A method of
manufacturing and a heating system is also provided.
Inventors: |
Beste; Mark G.; (Grapevine,
TX) ; Wynnick; David M.; (Frisco, TX) |
Correspondence
Address: |
HITT GAINES P.C.
P.O. BOX 832570
RICHARDSON
TX
75083
US
|
Assignee: |
Lennox Manufacturing Inc.
Richardson
TX
|
Family ID: |
37984275 |
Appl. No.: |
11/256783 |
Filed: |
October 24, 2005 |
Current U.S.
Class: |
165/177 |
Current CPC
Class: |
F28F 1/42 20130101; F28F
1/426 20130101; B21C 37/158 20130101 |
Class at
Publication: |
165/177 |
International
Class: |
F28F 1/00 20060101
F28F001/00 |
Claims
1. A heat exchanger apparatus, comprising: a frame; a tube coupled
to said frame; and turbulating structure disposed within said tube
and extending into an inner hollow space thereof for promoting
turbulent fluid flow within said tube, said turbulating structure
comprising elements located arcuately around an inner periphery of
said tube at approximately 120.degree. increments.
2. The apparatus of claim 1 wherein said elements comprise dimples
formed in said tube.
3. The apparatus of claim 1 wherein said tube has a longitudinal
axis and wherein said turbulating structure comprises a first
dimple trio formed in said tube and having a first trio of centers,
said first trio of centers substantially coplanar with a plane
normal to said longitudinal axis.
4. The apparatus of claim 3 wherein said turbulating structure
comprises a second dimple trio spaced apart from said first dimple
trio along said longitudinal axis, and wherein said tube has: a
first reference radius from said longitudinal axis and through a
center of one of said elements of said first dimple trio; and a
second reference radius from said longitudinal axis and through a
center of one of said elements of said second dimple trio; and
wherein said first and second reference radii are coplanar.
5. The apparatus of claim 4 wherein said first dimple trio has a
first dimple depth and said second dimple trio has a second dimple
depth not equal to said first dimple depth.
6. The apparatus of claim 3 wherein said turbulating structure
comprises a second dimple trio spaced apart from said first dimple
trio along said longitudinal axis, and wherein said tube has: a
first reference radius from said longitudinal axis and through a
center of one of said elements of said first dimple trio; a second
reference radius from said longitudinal axis and through a center
of one of said elements of said second dimple trio; and wherein
said first and second reference radii are non-coplanar.
7. The apparatus of claim 6 wherein said second reference radius
arcuately differs from said first reference radius by an angle
between about .+-.5.degree. and about .+-.30.degree..
8. The apparatus of claim 7 wherein said turbulating structure
comprises a third dimple trio spaced apart from said second dimple
trio along said longitudinal axis, and wherein said tube has a
third reference radius from said longitudinal axis and through a
one of said elements of said third dimple trio wherein said third
reference radius arcuately differs from said second reference
radius by an angle between about .+-.5.degree. and about
.+-.30.degree..
9. The apparatus of claim 1 wherein said turbulating structure
comprise said dimples including smoothly curving surfaces in said
tube.
10. The apparatus of claim 1 wherein said tube has a weld parallel
said longitudinal axis.
11. The apparatus of claim 10 wherein a one of said elements is
diametrically opposed said weld.
12. The apparatus of claim 1 wherein said tube has a path for
off-cycle or off-season condensate.
13. A method of manufacturing a heat exchanger apparatus,
comprising: providing a frame; coupling a tube to said frame; and
disposing turbulating structure within said tube and extending into
an inner hollow space thereof for promoting turbulent fluid flow
within said tube, said turbulating structure comprising elements
located arcuately around an inner periphery of said tube at
approximately 120.degree. increments.
14. The method of claim 13 wherein disposing includes forming
dimples in said tube.
15. The method of claim 13 wherein said tube has a longitudinal
axis and wherein disposing includes forming a first dimple trio in
said tube, said first dimple trio substantially coplanar with a
plane normal to said longitudinal axis.
16. The method of claim 15 wherein disposing includes forming a
second dimple trio spaced apart from said first dimple trio along
said longitudinal axis, and wherein said tube has: a first
reference radius from said longitudinal axis and through a one of
said elements of said first dimple trio; and a second reference
radius from said longitudinal axis and through a one of said
elements of said second dimple trio; and wherein said first and
second reference radii are coplanar.
17. The method of claim 16 wherein disposing includes forming said
first dimple trio having a first dimple depth and forming said
second dimple trio having a second dimple depth not equal to said
first dimple depth.
18. The method of claim 15 wherein disposing includes forming a
second dimple trio spaced apart from said first dimple trio along
said longitudinal axis, and wherein said tube has: a first
reference radius from said longitudinal axis and through a one of
said elements of said first dimple trio; and a second reference
radius from said longitudinal axis and through a one of said
elements of said second dimple trio; and wherein said first and
second reference radii are non-coplanar.
19. The method of claim 16 wherein disposing includes forming said
second dimple such that said second reference radius arcuately
differs from said first reference radius by an angle between about
.+-.5.degree. and about .+-.30.degree..
20. The method of claim 19 wherein disposing includes forming a
third dimple trio spaced apart from said second dimple trio along
said longitudinal axis, and wherein said tube has a third reference
radius from said longitudinal axis and through a one of said
elements of said third dimple trio wherein said third reference
radius arcuately differs from said second reference radius by an
angle between about .+-.5.degree. and about .+-.30.degree..
21. The method of claim 13 wherein disposing includes forming said
dimples including smoothly curving surfaces in said tube.
22. The method of claim 13 wherein coupling includes coupling a
tube having a weld parallel said longitudinal axis.
23. The method of claim 22 wherein coupling includes coupling
wherein a one of said elements is diametrically opposed said
weld.
24. A heating system, comprising: a cabinet; a frame coupled to
said cabinet; a heat exchanger having at least one tube coupled to
said frame; and turbulating structure disposed within said tube and
extending into an inner hollow space thereof for promoting
turbulent fluid flow within said tube, said turbulating structure
comprising elements located arcuately around an inner periphery of
said tube at approximately 120.degree. increments.
25. The heating system of claim 24 wherein said elements comprise
dimples formed in said tube.
26. The heating system of claim 24 wherein said tube has a
longitudinal axis and wherein said turbulating structure comprises
a first dimple trio formed in said tube, said first dimple trio
substantially coplanar with a plane normal to said longitudinal
axis.
27. The heating system of claim 26 wherein said turbulating
structure comprises a second dimple trio spaced apart from said
first dimple trio along said longitudinal axis, and wherein said
tube has: a first reference radius from said longitudinal axis and
through a one of said elements of said first dimple trio; a second
reference radius from said longitudinal axis and through a one of
said elements of said second dimple trio; and wherein said first
and second reference radii are coplanar.
28. The heating system of claim 27 wherein said first dimple trio
has a first dimple depth and said second dimple trio has a second
dimple depth not equal to said first dimple depth.
29. The heating system of claim 26 wherein said turbulating
structure comprises a second dimple trio spaced apart from said
first dimple trio along said longitudinal axis, and wherein said
tube has: a first reference radius from said longitudinal axis and
through a one of said elements of said first dimple trio; a second
reference radius from said longitudinal axis and through a one of
said elements of said second dimple trio; and wherein said first
and second reference radii are non-coplanar.
30. The heating system of claim 29 wherein said second reference
radius arcuately differs from said first reference radius by about
+30.degree..
31. The heating system of claim 30 wherein said turbulating
structure comprises a third dimple trio spaced apart from said
second dimple trio along said longitudinal axis, and wherein said
tube has a third reference radius from said longitudinal axis and
through a one of said elements of said third dimple trio wherein
said third reference radius arcuately differs from said second
reference radius by about -30.degree..
32. The heating system of claim 24 wherein said turbulating
structure comprises said dimples including curving surfaces in said
tube.
33. The heating system of claim 24 wherein said tube has a weld
parallel said longitudinal axis.
34. The heating system of claim 33 wherein a one of said elements
is diametrically opposed said weld.
Description
TECHNICAL FIELD OF THE INVENTION
[0001] The present invention is directed, in general, to heat
exchange apparatus and, more specifically, to a design for heat
exchanger tubes.
BACKGROUND OF THE INVENTION
[0002] Heat exchange tubes are used to transfer heat between two
media by using, for example, a so-called "tube-in-tube" design or a
"shell-in-tube" design. In a "tube-in-tube" design the fluid
product to be heated or cooled flows through a product tube or
series of product tubes and the heating or cooling media flows
through an outer media tube or series of media tubes usually in a
countercurrent fashion with respect to the product flow. Thus, heat
is transferred between the media flowing in the inner space between
the walls of the media and product tubes and the fluid product
flowing through the product tubes or tubes. In a "shell-in-tube"
design the product tubes are disposed within a container referred
to as a shell and within which the heating or cooling media flows
over all of the product tubes from an inlet to an outlet thereof to
transfer heat between the media and the product.
[0003] To improve heat transfer efficiency the product tubes in
either a tube-in-tube design or shell-in-tube design have included
turbulating structure of various configurations to promote flow
within the tube at a Reynolds number between 8,000 and 10,000,
approaching turbulent flow. Generally stated, turbulent flow
increases the heat transfer efficiency of the tube by distributing
the core fluid flowing therethrough across the entire diameter of
the tube and not in streams flowing generally parallel to the axis
of the tube in substantially laminar flow. Since a higher rate of
heat transfer occurs adjacent the wall of the product tube, ideally
a flow pattern is created which eliminates a temperature gradient
within the fluid at any cross section taken through the tube.
[0004] One method of inducing turbulent flow that has been used
with some success is the formation of paired dimples in an outer
surface of the heat exchange tube. In many cases, the pairs of
dimples are diametrically opposite on the surface of the tube. In
some cases, the dimples are co-linear along a line parallel to the
axis of the tube. In other cases, successive dimple pairs are
non-co-linear, being positioned axially by a set number of degrees,
e.g., 30.degree. or 40.degree., from the previous pair so as to
induce an additional rotational effect to the fluid flow.
[0005] Nonetheless, there is continual emphasis in most industries
to make ever more efficient units in ever more restricted space.
This is particularly true in the heating and air conditioning
industry where reducing the heat exchanger cabinet size for a given
tonnage is always a design objective. As a result, conventional
approaches to increasing efficiency and therefore increasing
Reynolds number are limited by the geometry of the system.
[0006] Accordingly, what is needed in the art is an improved design
for turbulating mechanisms in heat exchanger tubes to improve
efficiency within a given tube length.
SUMMARY OF THE INVENTION
[0007] To address the above-discussed deficiencies of the prior
art, the present invention provides a heat exchanger apparatus
comprising a frame, a tube coupled to the frame, and turbulating
structure disposed within the tube and extending into an inner
hollow space thereof for promoting turbulent fluid flow within the
tube. The turbulating structure comprises elements located
arcuately around an inner periphery of the tube at approximately
120.degree. increments. A method of manufacturing and a heating
system is also provided.
[0008] The foregoing has outlined preferred and alternative
features of the present invention so that those skilled in the art
may better understand the detailed description of the invention
that follows. Additional features of the invention will be
described hereinafter that form the subject of the claims of the
invention. Those skilled in the art should appreciate that they can
readily use the disclosed conception and specific embodiment as a
basis for designing or modifying other structures for carrying out
the same purposes of the present invention. Those skilled in the
art should also realize that such equivalent constructions do not
depart from the spirit and scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] For a more complete understanding of the present invention,
reference is now made to the following descriptions taken in
conjunction with the accompanying drawings, in which:
[0010] FIG. 1 illustrates a side elevation view of a portion of one
embodiment of a heat exchanger tube constructed according to the
principles of the present invention;
[0011] FIG. 2 illustrates a cross sectional view of the heat
exchanger tube of FIG. 1 at plane 2-2;
[0012] FIG. 3 illustrates a perspective view of a portion of the
heat exchanger tube of FIG. 1;
[0013] FIGS. 4A-4C illustrate sectional views of the heat exchanger
tube of FIG. 3 at planes 4A-4A, 4B-4B, and 4C-4C, respectively;
[0014] FIG. 5 illustrates a side elevation view of a portion of a
first alternative embodiment of the heat exchanger tube of FIG.
1;
[0015] FIGS. 6A--6C illustrate sectional views of the heat
exchanger tube of FIG. 5 at planes 6A-6A, 6B-6B, and 6C-6C,
respectively;
[0016] FIG. 7 illustrates a side elevation view of a portion of a
second alternative embodiment of the heat exchanger tube of FIG.
1;
[0017] FIGS. 8A-8C illustrate sectional views of the heat exchanger
tube of FIG. 7 at planes 8A-8A, 8B-8B, and 8C-8C, respectively;
[0018] FIG. 9 illustrates a side elevation view of a portion of a
third alternative embodiment of the heat exchanger tube of FIG.
1;
[0019] FIGS. 10A-10C illustrate sectional views of the heat
exchanger tube of FIG. 9 at planes 10A-10A, 10B-10B, 10C-10C,
respectively;
[0020] FIG. 11 illustrates a side elevation view of one embodiment
of a heat exchanger tube constructed according to the principles of
the present invention;
[0021] FIG. 12 illustrates a perspective view of one embodiment of
a hydraulic dimpler for the manufacture of a heat exchanger tube
constructed according to the principles of the present
invention;
[0022] FIG. 13 illustrates an enlarged view of the part holder and
a portion of the first, second and third hydraulic rams of FIG. 12;
and
[0023] FIG. 14 illustrates a heating system constructed according
to the principles of the present invention.
DETAILED DESCRIPTION
[0024] Referring initially to FIG. 1, illustrated is a side
elevation view of a portion of one embodiment of a heat exchanger
tube 100 constructed according to the principles of the present
invention. In a preferred embodiment, the heat exchanger tube 100
comprises a tube 110 having a weld seam 111 along a length l and
parallel to a centerline 112 thereof, and a turbulating structure
121 extending into an inner hollow space therein around an inner
periphery thereof. In one embodiment, the turbulating structure 121
comprises a plurality of elements 122a-122c, 123a-123c, 124a-124c,
in their respective groups 122, 123, 124 of multiple elements
disposed at spaced apart intervals i along the length 1 of the tube
110. In a preferred embodiment, the plurality of elements
122a-122c, 123a-123c, 124a-124c comprise a plurality of dimples
122a-122c, 123a-123c, 124a-124c arranged in respective trios 122,
123, 124 wherein centers 125 of each dimple of each trio group 122,
123, 124 are substantially co-planar with a respective plane 132,
133, 134 that is normal to the centerline 112 of the tube 110 and
passing through the centers 125. In a preferred embodiment, the
dimples 122a-122c, 123a-123c, 124a-124c are smoothly curved
surfaces.
[0025] Referring now to FIG. 2 with continuing reference to FIG. 1,
illustrated is a cross sectional view of the heat exchanger tube
100 of FIG. 1 at plane 2-2. The cross section at plane 2-2 is
substantially the same as at planes 132, 133, and 134. In a
preferred embodiment, the heat exchanger tube 100 has dimples
225a-225c with a depth d spaced at approximately 120.degree.
intervals 210 around the inner periphery 213 of the tube 100. The
weld seam 111 is diametrically opposed to a center 221 of one 225c
of the dimples 225a-225c so as to avoid placing a dimple on the
weld seam 111. This orientation of the weld seam 111 reduces the
likelihood of stressing the weld seam 111 during forming of the
dimples 225a-225c or thereafter. One who is of skill in the art
will recognize that because three dimples 225a-225c are being
formed, the depth d of each dimple 225a-225c is manifestly less
than dimples formed in opposed pairs, therefore, there is less
residual stress in the tube 110 as a result of the forming to be
described below. Of course, the problems associated with forming a
dimple on a weld may be solved by using seamless tubing as will be
important in embodiments yet to be described. This becomes
increasingly significant as successive dimple sets are displaced
radially around the surface of the tubing.
[0026] As an example, a reference radius 215 may be drawn from the
centerline 112 through a center 221a-221c of one 225a of the
dimples 225a-225c. The significance of this reference radius 215
will be discussed below. In a typical heat exchanger tube 100
formed from 2 inch tubing and using a 1 inch diameter hemispherical
tool end, the dimple depth d can be adjusted up to a maximum dimple
depth d of about 0.867''. The dimple depth d and tubing size can be
adjusted to achieve a desired Reynolds Number. In a preferred
embodiment, internal area of 5/8-inch tubing at the dimples may be
sized to produce a Reynolds Number from about 8,000 to about 10,000
with about a 400.degree. F. to about a 450.degree. F. flue
temperature. In a like manner, using 1/2-inch tubing produces a
Reynolds Number of about 12,000 under the same conditions. It
should be noted that tubing of any appropriate diameter and wall
thickness can be used. Also, the dimple depth can be controlled
down to the limit wherein a set of dimples touch at the centerline
within the tubing. In one embodiment, the first dimple trio 122 may
have a first dimple depth and the second dimple trio 123 may have a
second dimple depth wherein the second dimple depth is not equal to
the first dimple depth. One who is of skill in the art will
recognize that this variation of dimple depth may be applied to
vary from one set of dimples to the next all along the tubing.
Additionally, the diameter of the hemispherical tool end can be
increased or decreased in order to change the size of the dimples
and correspondingly the Reynolds number. In a preferred embodiment,
the heat exchanger tube 100 comprises a path 230 for off-cycle or
off-season condensate.
[0027] Referring now to FIG. 3, illustrated is a perspective view
of a portion of the heat exchanger tube 100 of FIG. 1. In a
preferred embodiment, the heat exchanger tube 100 has at least four
dimple trios 310, 320, 330, 340 spaced-apart by an interval i. In
one embodiment, the interval i is a constant for a given heat
exchanger tube 100. In an alternative embodiment, the interval i
between successive dimple trios is variable in order to introduce
more turbulence in the flow throughout the heat exchanger tube 100.
The first dimple trio 310 has a first reference radius 311 drawn
from the centerline 112 through a center 312 of one 310a of the
dimples 310a-310c in the manner as described with reference to FIG.
2. In a like manner, the second dimple trio 320 has a second
reference radius 321 drawn from the centerline 112 through a center
322 of one 320a of the dimples 320a-320c, and the third dimple trio
330 has a third reference radius 331 drawn from the centerline 112
through a center 332 of one 330a of the dimples 330a-330c. In a
preferred embodiment, the first, second and third radii 311, 321,
331 are substantially coplanar.
[0028] Referring now to FIGS. 4A-4C, illustrated are sectional
views of the heat exchanger tube 100 of FIG. 3 at planes 4A-4A,
4B-4B, and 4C-4C, respectively. As can be seen, the reference radii
311, 321, 331 are coaligned, and would therefore be coplanar, i.e.,
they lie in a common plane defined by the longitudinal axis 112 and
the first and third reference radii 311, 331. of course, additional
dimple trios with their associated reference radii could likewise
be formed in the heat exchanger tube 100 with their associated
reference radii in an extension of the same plane.
[0029] Referring now to FIG. 5, illustrated is a side elevation
view of a portion of a first alternative embodiment 500 of the heat
exchanger tube of FIG. 1. The heat exchanger tube 500 comprises
first, second and third sections 510, 520, 530, respectively. The
first section 510 has a first trio of dimples 511a-511c; the second
section 520 has a second trio of dimples 521a-521c; and the third
section 530 has a third trio of dimples 531a-531c. In this
embodiment, the second trio of dimples 521a-521c is clockwise
rotationally offset from the first trio of dimples 511a-511c about
a longitudinal axis 512 by an angle .alpha..sub.1 (See FIG. 6B).
The third trio of dimples 531a-531c is clockwise rotationally
offset from the second trio of dimples 521a-521c about the
longitudinal axis 512 by an angle .alpha..sub.2 (See FIG. 6C). In a
preferred embodiment, the angles .alpha..sub.1 and .alpha..sub.2
may be any number of degrees between about 5.degree. and about
30.degree..
[0030] Referring now to FIGS. 6A-6C with continuing reference to
FIG. 5, illustrated are sectional views of the heat exchanger tube
500 of FIG. 5 at planes 6A-6A, 6B-6B, and 6C-6C, respectively. In
the illustrated embodiment, the second trio of dimples 521a-521c is
clockwise rotationally offset from the first trio of dimples
511a-511c by an angle .alpha..sub.1. As an example, in the
illustrated embodiment, the angle .alpha..sub.1 is about
15.degree.. In a similar manner, the third trio of dimples
531a-531c is clockwise rotationally offset from the second trio of
dimples 521a-521c by an angle .alpha..sub.2. Again, as an example,
in the illustrated embodiment, the angle .alpha..sub.2 is also
about 15.degree..
[0031] Referring now to FIG. 7, illustrated is a side elevation
view of a portion of a second alternative embodiment 700 of the
heat exchanger tube of FIG. 1. The heat exchanger tube 700
comprises first, second and third sections 710, 720, 730,
respectively. The first section 710 has a first trio of dimples
711a-711c; the second section 720 has a second trio of dimples
721a-721c; and the third section 730 has a third trio of dimples
731a-731c. In this embodiment, the second trio of dimples 721a-721c
is counterclockwise rotationally offset from the first trio of
dimples 711a-711c about a longitudinal axis 712 by an angle
.alpha..sub.3 (See FIG. 8B). The third trio of dimples 731a-731c is
counterclockwise rotationally offset from the second trio of
dimples 721a-721c about the longitudinal axis 712 by an angle
.alpha..sub.4 (See FIG. 8C). In a preferred embodiment, the angles
.alpha..sub.3 and .alpha..sub.4 may be any number of degrees
between about 5.degree. and about 30.degree..
[0032] Referring now to FIGS. 8A-8C with continuing reference to
FIG. 7, illustrated are sectional views of the heat exchanger tube
700 of FIG. 7 at planes 8A-8A, 8B-8B, and 8C-8C, respectively. In
the illustrated embodiment, the second trio of dimples 721a-721c is
counterclockwise rotationally offset from the first trio of dimples
711a-711c by the angle .alpha..sub.3. As an example, in the
illustrated embodiment, the angle .alpha..sub.3 is about
-15.degree.. In a similar manner, the third trio of dimples
731a-731c is counterclockwise rotationally offset from the second
trio of dimples 721a-721c by the angle .alpha..sub.4. Again, as an
example, in the illustrated embodiment, the angle .alpha..sub.4 is
also about -15.degree.. In this alternative embodiment, the
rotational offset is counterclockwise by the angles .alpha..sub.3
and .alpha..sub.4. The rotational offset between successive dimple
trios may be individually varied between about 5.degree. and about
30.degree..
[0033] Referring now to FIG. 9, illustrated is a side elevation
view of a portion of a third alternative embodiment 900 of the heat
exchanger tube of FIG. 1. The heat exchanger tube 900 comprises
first, second and third sections 910, 920, 930, respectively. The
first section 910 has a first trio of dimples 911a-911c; the second
section 920 has a second trio of dimples 921a-921c; and the third
section 930 has a third trio of dimples 931a-931c. In this
embodiment, the second trio of dimples 921a-921c is clockwise
rotationally offset from the first trio of dimples 911a-911c about
a longitudinal axis 912 by an angle .alpha..sub.5 (See FIG. 10B).
The third trio of dimples 931a-931c is counterclockwise
rotationally offset from the second trio of dimples 921a-921c about
the longitudinal axis 912 by an angle .alpha..sub.6 (See FIG. 10C).
In a preferred embodiment, the angles .alpha..sub.5 and may be any
number of degrees between about 5.degree. and about 30.degree..
[0034] Referring now to FIGS. 10A-10C, illustrated are sectional
views of the heat exchanger tube of FIG. 9 at planes 10A-10A,
10B-10B, 10C-10C, respectively. In this embodiment, a second trio
of dimples 921a-921c is clockwise rotationally offset from a first
trio of dimples 911a-911c by the angle .alpha..sub.5. As an
example, in the illustrated embodiment, the angle .alpha..sub.5 is
about 15.degree.. In a similar manner, the third trio of dimples
931a-931c is counterclockwise rotationally offset from the second
trio of dimples 921a-921c by the angle .alpha..sub.6. Again, as an
example, in the illustrated embodiment, the angle .alpha..sub.6 is
about -30.degree.. In this alternative embodiment, the rotational
offset is offset clockwise by the angle .alpha..sub.5 and
counterclockwise by the angle .alpha..sub.6. In this embodiment,
the rotational offset between successive dimple trios may be
individually varied between about 5.degree. and about 30.degree..
In this advantageous embodiment, the rotational offset reverses
with each successive trio of dimples. Each successive trio of
dimples may therefore be rotationally offset in either a clockwise
or counterclockwise direction, as desired. It should be noted that
embodiments of this type with successive dimple trios rotationally
offset from the previous dimple trio by some angle is most
effective when the heat exchanger tube comprises seamless tubing,
thereby resulting in the least induced stress in the heat exchanger
tube.
[0035] Referring now to FIG. 11, illustrated is a side elevation
view of one embodiment of a heat exchanger tube 1100 constructed
according to the principles of the present invention. The heat
exchanger tube 1100 comprises first, second and third sections
1110, 1120, 1130, respectively. The first section 1110 is a
substantially straight section for positioning the heat exchanger
tube 1100 within a heat exchanger cabinet (not shown). The second
section 1120 has a substantially U-shaped bend to re-route the heat
exchanger tube 1100 to minimize horizontal cabinet size. The third
section 1130 has five trios of dimples 1131-1135 impressed therein
so as to create turbulent fluid flow through the heat exchanger
tube 1100. One who is of skill in the art is familiar with such a
heat exchanger tube and how it may be formed in general.
[0036] Specifically, the dimpled third section 1130 of the heat
exchanger tube 1100 of FIG. 11 may be formed in a forming jig and
hydraulic press. Referring now to FIG. 12, illustrated is a
perspective view of one embodiment of a hydraulic dimpler 1200 for
the manufacture of a heat exchanger tube constructed according to
the principles of the present invention. The hydraulic dimpler 1200
comprises a two-piece part holder 1210, and first, second and third
hydraulic rams 1221, 1222, 1223. One who is of skill in the art is
familiar with hydraulic dimpling of tubing in general.
[0037] Referring now to FIG. 13 with continuing reference to FIG.
11, illustrated is an enlarged view of the part holder 1210 and a
portion of the first, second and third hydraulic rams 1221, 1222,
1223 of FIG. 12. The first, second and third hydraulic rams 1221,
1222, 1223 have hemispherical end forming tools 1321, 1322, 1323
proximate the tube 1301 being formed. Dimple trios 1131-1135 may be
impressed using the hydraulicly operated press forcing the three
hemispherical end forming tools 1321, 1322, 1323 radially inward
and spaced around the circumference of the tube 1100 at
approximately 120.degree. intervals while holding the tube 1100
motionless in the part holder 1210. One who is of skill in the art
is familiar with this process. In one embodiment, a single trio may
be formed at each time. In a preferred embodiment, all dimple trios
1131-1135 may be formed simultaneously by assembling a press that
has an appropriate number of banks of hydraulic rams 1221, 1222,
1223. Rotational locating of successive dimple trios can be
achieved by appropriately positioning each successive bank of
hydraulic rams 1221, 1222, 1223.
[0038] Referring now to FIG. 14, illustrated is a heating system
1400 constructed according to the principles of the present
invention. The heating system 1400 comprises a cabinet 1410, a
frame 1420, a heat exchanger 1430 and at least one heat exchanger
tube 1440. The heat exchanger tube 1440 is coupled to the frame
1420, and the frame 1420 is coupled to the cabinet 1410. A
turbulating structure 1445 constructed according to the principles
of the present invention is disposed within the heat exchanger tube
1440.
[0039] Thus, a heat exchanger apparatus has been described
comprising a heat exchanger tube having turbulating structure in
the form of trios of elements disposed within the heat exchanger
tube. The advantages of the present invention include reducing
residual stress within the heat exchanger tube while minimizing
overall cabinet size and increased Reynolds number for flue
products. The resultant increased pressure drop increases overall
efficiency accordingly. An unobstructed path is also provided for
the drain of condensate during off-season and off cycle
operation.
[0040] Although the present invention has been described in detail,
those skilled in the art should understand that they can make
various changes, substitutions and alterations herein without
departing from the spirit and scope of the invention in its
broadest form.
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