U.S. patent application number 10/869327 was filed with the patent office on 2004-11-25 for system and method for joining tubes to sheets in a tubular heat transfer system.
This patent application is currently assigned to Elliott Tool Technologies Ltd.. Invention is credited to Barber, John P., Columbus, Robert M., Kouse, Bruce D., Newman, Duane C..
Application Number | 20040231157 10/869327 |
Document ID | / |
Family ID | 29548938 |
Filed Date | 2004-11-25 |
United States Patent
Application |
20040231157 |
Kind Code |
A1 |
Barber, John P. ; et
al. |
November 25, 2004 |
System and method for joining tubes to sheets in a tubular heat
transfer system
Abstract
A system and method for expanding, joining or securing a
plurality of tubes by electromagnetic expansion to a plurality of
sheets in a tubular heat transfer system. The system and method
involve the automatic sensing and positioning of a electromagnetic
coil in operative relationship with at least a portion of a tube
and an inner wall of a sheet and then energizing the
electromagnetic coil to expand the portion of the tube to engage
the inner wall of the sheet, thereby securing the tube thereto. A
tubular heat transfer system tube expander and method are also
shown.
Inventors: |
Barber, John P.; (Dayton,
OH) ; Columbus, Robert M.; (Centerville, OH) ;
Kouse, Bruce D.; (Springfield, OH) ; Newman, Duane
C.; (London, OH) |
Correspondence
Address: |
Matthew R. Jenkins
JACOX, MECKSTROTH & JENKINS
Suite 2
2310 Far Hills Building
Dayton
OH
45419-1575
US
|
Assignee: |
Elliott Tool Technologies
Ltd.
Dayton
OH
IAP Research, Inc.
Dayton
OH
|
Family ID: |
29548938 |
Appl. No.: |
10/869327 |
Filed: |
June 16, 2004 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10869327 |
Jun 16, 2004 |
|
|
|
10154700 |
May 24, 2002 |
|
|
|
Current U.S.
Class: |
29/890.044 ;
29/890.03 |
Current CPC
Class: |
Y10T 29/49803 20150115;
F28F 9/16 20130101; Y10T 29/4935 20150115; F28F 9/22 20130101; Y10T
29/4994 20150115; Y10T 29/53122 20150115; Y10T 29/49375
20150115 |
Class at
Publication: |
029/890.044 ;
029/890.03 |
International
Class: |
F28F 007/00; B21D
053/02; B21D 039/08 |
Claims
What is claimed is:
1-20. (Cancelled)
21. A method for securing a plurality of conductive tubes to a
plurality of plates to provide a tube bundle in a tubular heat
transfer system, each of said plurality of plates having a
plurality of inner walls defining a plurality of apertures,
respectively, said method comprising the steps of: situating said
plurality of conductive tubes in said plurality of apertures.
respectively, and magnetically increasing a diameter of a portion
of at least one of said plurality of conductive tubes into
engagement with at least one of said plurality of inner walls,
thereby securing said at least one of said plurality of conductive
tubes to said at least one of said plurality of inner walls;
situating a coil inside said at least one of said plurality of
conductive tubes: energizing said coil to perform said increasing
step; and sensing said surrounding member and energizing said coil
when said coil is positioned in operative relationship with said
surrounding member.
22. A method for securing a conductive tube to at least one
surrounding member of a tubular heat transfer system, said method
comprising the steps of: inserting a coil into said conductive tube
until said coil is positioned in operative relationship with said
conductive tube and said at least one surrounding member;
energizing said coil to expand a portion of the conductive tube to
engage said at least one surrounding member, thereby securing said
conductive tube to said at least one surrounding member; said
energizing step further comprising the steps of: providing a
capacitor discharge bank that provides a predetermined capacitance:
charging said capacitor discharge bank with a predetermined
voltage: discharging said capacitor discharge bank to energize said
coil to perform said energizing step; wherein said conductive tube
comprises a conductive tube dimension and said surrounding member
comprises an inner wall comprising an inner wall dimension, said
method further comprising the steps of: selecting said
predetermined capacitance and said predetermined charge voltage in
response to at least said conductive tube dimension and said inner
wall dimension; and sensing a next position of said plurality of
positions and performing said energizing step at said next
position.
23-26. (Cancelled)
27. A method for enlarging a first portion and a second portion of
a conductive tube for use in a tubular heat transfer system, said
method comprising the steps of: moving a coil to a first position
in operative relationship with said first portion of said
conductive tube; energizing said coil to enlarge magnetically said
first portion of said conductive tube at said first position;
moving said coil to the second position in operative relationship
with said second portion of said conductive tube; energizing said
coil to enlarge magnetically said second portion of said conductive
tube at said second position; and sensing said first position
before said first energizing step; sensing said second position
after said first energizing step, but before said second energizing
step.
28. A method for enlarging a first portion and a second portion of
a conductive tube for use in a tubular heat transfer system, said
method comprising the steps of: moving a coil to a first position
in operative relationship with said first portion of said
conductive tube; energizing said coil to enlarge magnetically said
first portion of said conductive tube at said first position;
moving said coil to the second position in operative relationship
with said second portion of said conductive tube; energizing said
coil to enlarge magnetically said second portion of said conductive
tube at said second position; inserting said conductive tube in a
first surrounding member located at said first position and a
second surrounding member located at said second position;
performing said first energizing step to secure said first portion
of said conductive tube to said first surrounding member;
performing said second energizing step to secure said second
portion of said conductive tube to said second surrounding member;
and sensing a position of said first surrounding member before said
first moving step; and sensing a position of said second
surrounding member before said second moving step and after said
first energizing step.
29-40. (Cancelled)
41. A method for assembling a tubular heat transfer system having a
housing, said method comprising the steps of: (a) providing a
plurality of sheets, each of said plurality of sheets comprising a
plurality of inner walls defining a plurality of apertures,
respectively (b) positioning a plurality of conductive tubes into
said plurality of apertures, respectively; (c) inserting a coil
into a first conductive tube of said plurality of conductive tubes;
(d) moving said coil to a first position in said first conductive
tube; said first position corresponding to where a first inner wall
of said plurality of inner walls and said coil become substantially
aligned; (e) energizing said coil to enlarge magnetically said
first portion of said first conductive tube adjacent the first
inner wall to secure said first portion of said first conductive
tube to said first inner wall; (f) moving a second coil to a next
position in said first conductive tube; said second position
corresponding to where said a second inner wall of a second sheet
and said coil become substantially aligned; (g) energizing said
coil to enlarge magnetically said second portion of said first
conductive tube adjacent the second inner wall to secure said
second portion of said first conductive tube to said second inner
wall; and (h) repeating said steps (f) and (g) until each of said
plurality of conductive tubes is secured to said plurality of
sheets; and sensing said first position before performing said step
(e).
42. A method for assembling a tubular heat transfer system having a
housing, said method comprising the steps of: (a) providing a
plurality of sheets, each of said plurality of sheets comprising a
plurality of inner walls defining a plurality of apertures,
respectively; (b) positioning a plurality of conductive tubes into
said plurality of apertures, respectively; (c) inserting a coil
into a first conductive tube of said plurality of conductive tubes;
(d) moving said coil to a first position in said first conductive
tube; said first position corresponding to where a first inner wall
of said plurality of inner walls and said coil become substantially
aligned; (e) energizing said coil to enlarge magnetically said
first portion of said first conductive tube adjacent the first
inner wall to secure said first portion of said first conductive
tube to said first inner wall; (f) moving a second coil to a next
position in said first conductive tube; said second position
corresponding to where said a second inner wall of a second sheet
and said coil become substantially aligned; (g) energizing said
coil to enlarge magnetically said second portion of said first
conductive tube adjacent the second inner wall to secure said
second portion of said first conductive tube to said second inner
wall; and (h) repeating said steps (f) and (g) until each of said
plurality of conductive tubes is secured to said plurality of
sheets; and sensing said second position before performing said
step (g).
43-92. (Cancelled).
93. An expander assembly comprising: an expander for magnetically
enhancing at least a portion of a tube into a surrounding member;
and a sensor connected with the expander for sensing a position of
the surrounding member as the expander is moved through the
tube.
94. The expander assembly as recited in claim 93 wherein said
expander assembly comprises: a cable having a first mount and a
second mount for detachably coupling to said direct drive expander;
a sensor associated with the mount for sensing said surrounding
member.
95. The expander assembly as recited in claim 94 wherein said cable
comprises a sensor core for coupling said sensor to a
controller.
96. The expander assembly as recited in claim 93 wherein said
sensor is a Hall effect sensor.
97. The expander assembly as recited in claim 94 wherein said cable
is extruded and comprises a sensor bundle, a first conductor and a
second conductor, said first and second conductors conductively
coupling said coil to said circuit.
98. The expander assembly as recited in claim 93 wherein said
expander assembly comprises a sensor for sensing the surrounding
member as the direct drive expander is moved through the tube.
99. The expander assembly as recited in claim 93 wherein said
surrounding member is a sheet.
100. The expander assembly as recited in claim 93 wherein said
expander is a coil.
101. The expander assembly as recited in claim 100 wherein said
coil is a solenoid.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to a process for joining a tube, such
as either a finned/enhanced tube or a prime/smooth surface tube, to
at least one baffle, support, and/or tube sheet in the manufacture
or maintenance of a tubular heat transfer system that uses an
electromagnetic force to expand the tubes such that the outer
surface of the tubes makes joining contact with apertures in the
sheets.
[0003] 2. Description of the Related Art
[0004] Tubular heat transfer systems include tubular systems of the
type conventionally employed in air conditioners, heat exchangers,
chillers, evaporators, boilers, and absorption units. The
efficiency of tubular heat transfer systems is dependent in
substantial measure on the efficiency of heat transferred between a
media circulated through tubes and another media in heat exchange
relation to the exterior of the tubes. The efficiency of heat
transferred between the fluid surrounding the tubes is also
enhanced by avoiding laminar flow of the fluid over the tubes.
[0005] The tubes used in a tubular heat transfer system are held in
place by tube sheets situated on the end of the tubular heat
transfer system. One or more tube supports sheets or baffle sheets
may be provided to support the tubes between the tube sheets.
Tubular heat transfer system tubes are supplied in various surface
configurations that enable certain media to exchange heat better
than others. The expander referenced here will expand either
prime/smooth tubes or enhanced/finned tubes. Enhanced tubes are
manufactured with a variety of inside surface raised ridges to
provide turbulence to the flow through the tube, which enables
greater heat transfer. Finned tubes are also manufactured with a
variety of fin configurations on the outside surface and are
selected based on the media that is being used to transfer heat
over the tubes. Because of these two surface configurations,
current tube expanders are unable to adequately expand these
enhanced/finned tubes. Conventionally inside surface enhancing and
outside surface finning are suspended in areas where the tube is to
be joined to the support/baffle sheets and the end tube sheets
because conventional tube expanders destroy internal ridges and
overwork the tube and produce stress cracking at the junctions
between the tube and the support/baffle sheets. In general, the
ability to expand a tube is dependent on three conditions, the
tube's thickness, diameter and the material the tube is made
from.
[0006] U.S. Pat. No. 5,050,669 discloses a tube support which
includes at least two parallel plates. The plates comprise a
plurality of pins that approximate the leading and trailing edges
of the plates in order to maintain the plates in a spaced
relationship. The pins and plates provide support for the tubes.
The use of electromagnetic force to expand a tube is described in
U.S. Pat. No. 5,853,507 to Alie et al.; U.S. Pat. No. 6,050,121 to
Daehn et al.; U.S. Pat. No. 4,947,667 to Gunkel et al.; U.S. Pat.
No. 5,497,927 to Wilson; U.S. Pat. No. 4,924,584 to Harney; U.S.
Pat. No. 4,059,882 to Wunder; U.S. Pat. No. 6,273,963 to Barber;
U.S. Pat. No. 4,929,415 to Okaziki; U.S. Pat No. 4,975,412 to
Okaziki; U.S. Pat. No. 5,405,574 to Chelluri et al.; U.S. Pat. No.
5,611,230 to Chelluri et al.; U.S. Pat. No. 5,611,139 to Chelluri
et al.; and U.S. Pat. No. 5,689,797 to Chelluri et al.
[0007] If the intersection or joint between the tubes and tube
sheets or baffle sheets is not tight, fluid can leak from the heat
exchanger shell over time. Also, if the intersection or joint
between the tube and baffle or support sheets is not tight, fluid
flow will cause vibration between the tube and baffle or support
sheet that can lead to undesirable wearing of the tube at the
interface. Over time this wearing can lead to premature failure of
the tube.
[0008] There is, therefore, a need for a tubular heat transfer
system manufacturing system and method for securing a plurality of
tubes to any surrounding members, such as support plates, end
plates or baffle plates which improves the securing of the tubes to
the sheets and which can be used to join enhanced or finned tubes
without damaging the tube.
SUMMARY OF THE INVENTION
[0009] In one aspect this invention comprises a method for securing
a conductive tube to at least one surrounding member of a tubular
heat transfer system, the method comprising the steps of inserting
a coil into the conductive tube until the coil is positioned in
operative relationship with the conductive tube and the surrounding
member and energizing the coil to expand at least a portion of the
conductive tube to engage the at least one surrounding member,
thereby securing the conductive tube to the at least one
surrounding member.
[0010] Another aspect of the invention is a method for securing a
plurality of conductive tubes to a plurality of plates to provide a
tube bundle in a tubular heat transfer system, each of the
plurality of plates having a plurality of inner walls defining a
plurality of apertures, respectively, the method comprising the
steps of situating the plurality of conductive tubes in the
plurality of apertures, respectively, and magnetically increasing a
diameter of at least a portion of at least one of the plurality of
conductive tubes into engagement with at least one of the plurality
of inner walls, thereby securing the at least one of the plurality
of conductive tubes to the at least one of the plurality of inner
walls.
[0011] Yet another aspect of this invention comprises a method for
enlarging a first portion and a second portion of a conductive tube
for use in a tubular heat transfer system, the system comprising
the steps of: moving a coil to a first position in operative
relationship with the first portion of the conductive tube,
energizing the coil to enlarge the first portion of the conductive
tube at the first position, moving the coil to the second position
in operative relationship with the second portion of the conductive
tube, and energizing the coil to enlarge the second portion of the
conductive tube at the second position.
[0012] Still another aspect of this invention comprises a method
for assembling a tubular heat transfer system having a housing, the
method comprising the steps of providing a plurality of sheets,
each of the plurality of sheets comprising a plurality of inner
walls defining a plurality of apertures, respectively, positioning
a plurality of conductive tubes into the plurality of apertures,
respectively, inserting a coil into a first conductive tube of the
plurality of conductive tubes, moving the coil to a first position
in the first conductive tube, the first position corresponding to
where a first inner wall of the plurality of inner walls, and the
coil become substantially aligned, energizing the coil to enlarge
the first portion of the first conductive tube adjacent the first
inner wall to secure the first portion of the first conductive tube
to the first inner wall, moving a second coil to a next position in
the first conductive tube, the second position corresponding to
where the second inner wall of a second sheet and the coil become
substantially aligned, energizing the coil to enlarge the second
portion of the first conductive tube adjacent the second inner wall
to secure the second portion of the first conductive tube to the
second inner wall, and repeating the steps until each of the
plurality of conductive tubes is secured to the plurality of
sheets.
[0013] Still another aspect of this invention comprises a tube
bundle in a tubular heat transfer system, comprising a plurality of
walls defining a plurality of apertures, respectively, a conductive
tube situated in each of the plurality of apertures, and the
conductive tube comprising an enlarged portion at each of a
plurality of positions at which at least one of the plurality of
walls surrounds the tube, thereby causing an interference fit
between the enlarged portion and the at least one of the plurality
of walls engaged by the enlarged portion, wherein the conductive
tube comprises a continuously enhanced tube.
[0014] Yet another aspect of this invention comprises a tubular
heat transfer system comprising, a plurality of sheets comprising a
plurality of walls defining a plurality of apertures, respectively,
a plurality of conductive tubes situated in the plurality of
apertures, respectively, each of the plurality of walls surrounding
each of the plurality of conductive tubes at a plurality of
positions, each of the plurality of conductive tubes comprising an
enlarged portion at each of the plurality of positions to cause an
interference pressure between the enlarged portion and at least one
of the plurality of walls engaged by the enlarged portion, thereby
securing the plurality of conductive tubes to the plurality of
walls to provide a tube bundle, a housing for surrounding the tube
bundle, each of the plurality of conductive tubes comprising a
continuously enhanced tube, and the plurality of sheets comprising
a first tube sheet and a second tube sheet for sealing the housing
to define an inlet area, a heat exchange area, and an outlet area,
the housing having an inlet opening associated with the inlet area
and an outlet opening associated with the outlet area, the
plurality of conductive tubes enabling communication of fluid
between the inlet area and the outlet area.
[0015] Still another aspect of this invention comprises a heat
exchange tube expander for use relative to a tubular heat transfer
system comprising a plurality of conductive tubes, the heat
exchange tube expander comprising a coil for inserting into at
least one of the plurality of conductive tubes and positioning at a
plurality of positions in the at least one of the plurality of
conductive tubes, a circuit coupled to the coil, the circuit
comprising a capacitor discharge bank having a predetermined
capacitance and being capable of receiving a predetermined charge
voltage, and a switch for discharging the capacitor discharge bank
to energize the coil to increase a diameter of at least a portion
of the at least one of the plurality of conductive tubes to force
an outer surface of the at least a portion into engagement with a
surrounding member.
[0016] Yet another aspect of this invention comprises a method for
securing a conductive tube to a surrounding member of a tubular
heat transfer system, the method comprising the steps of inserting
a coil into a conductive tube, moving the coil along the inside of
the tube, when the coil reaches a position at which the tube
intersects the surrounding member, while the coil is moving,
energizing the solenoid to expand the portion of the conductive
tube at the position of intersection and thereby securing the
conductive tube to the surrounding member.
[0017] Still another aspect of this invention comprises a tube
bundle for use in a tubular heat transfer system, comprising a
plurality of sheets comprising a plurality of walls defining a
plurality of apertures, respectively, a conductive tube situated in
each of the plurality of apertures, and the conductive tube
comprising a magnetically enlarged portion at each of a plurality
of positions at which at least one of the plurality of walls
surrounds the tube, thereby causing an interference fit between the
magnetically enlarged portion and the at least one of the plurality
of walls engaged by the magnetically enlarged portion.
[0018] Still another aspect of this invention comprises an expander
assembly comprising an expander for magnetically enhancing at least
a portion of a tube into a surrounding member as the expander is
moved through the tube, and a sensor connected with the expander
for sensing a position of the surrounding member.
[0019] The invention will be described in more detail by reference
to specific embodiments thereof, the following description, and the
accompanying drawings.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWING
[0020] FIG. 1 is a sectional view of a tubular heat transfer system
in accordance with one embodiment of the invention;
[0021] FIG. 2 is a fragmentary sectional view of one end of the
tubular heat transfer system shown in FIG. 1 before an end bell is
secured thereto;
[0022] FIG. 3 is fragmentary sectional view showing a second end of
the tubular heat transfer system shown in FIG. 1;
[0023] FIG. 4 is a fragmentary sectional view illustrating a
relationship among a tube, tube sheet and coil before a portion of
the tube is expanded;
[0024] FIG. 5 is a fragmentary sectional view similar to FIG. 4
showing the coils situated in operative relationship to the tube
and tube sheet;
[0025] FIG. 6 is a fragmentary sectional view showing the portion
of the tube expanded in accordance with one embodiment of the
invention;
[0026] FIG. 7 illustrates a heat exchange tube expander and the
various positions at which one or more portions of the tube can be
expanded to secure it to any surrounding sheets;
[0027] FIG. 8 is a fragmentary sectional showing another coil
situated in operative relationship with the tube and a baffle
sheet;
[0028] FIG. 9 is a fragmentary sectional view illustrating a
portion of the tube expanded after the coil shown in FIG. 8 was
energized;
[0029] FIG. 10 is a circuit in accordance with one embodiment of
the invention;
[0030] FIG. 11 is a sectional view taken along the line 11-11 in
FIG. 2;
[0031] FIG. 12 is an enlarged fragmentary sectional view
illustrating a relationship between a tube and an inner wall of the
tube sheet shown in FIG. 11;
[0032] FIG. 13 is a sectional view taken along the line 12-12 in
FIG. 1;
[0033] FIG. 14 is an enlarged fragmentary sectional view
illustrating a relationship between a tube and an inner wall of a
baffle sheet shown in FIG. 13;
[0034] FIG. 15 is chart illustrating various expansion results for
an enhanced tube;
[0035] FIG. 16 is a schematic view illustrating a method in
accordance with one embodiment of the invention;
[0036] FIG. 17A is a fragmentary view of a detector and coil
assembly;
[0037] FIG. 17B is a sectional view taken along the line 17B-17B in
FIG. 17A;
[0038] FIG. 18 is a view of a coaxial cable used in one
embodiment;
[0039] FIG. 19 is a view of a direct drive expander before
energization; and
[0040] FIG. 20 is a view of a direct drive expander after
energization.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
[0041] Referring now to FIG. 1, a heat exchanger is shown. For ease
of illustration, the invention will be described relative to a heat
exchanger 10, but it is to be understood that the invention may be
used with any type of tubular heat transfer system, such as a heat
exchanger, a chiller, an air conditioner or an absorption unit. The
heat exchanger 10 comprises a shell or housing 12 having a first
flange 12a, a second flange 12b, a first end 12c, a second end 12d
and an inner surface 12e. A first header or end cap 14 having a
flange 14a is secured to the flange 12a and a second header or end
cap 16 having a flange 16a is secured to flange 12b by nuts and
bolts, as shown in FIG. 1.
[0042] The heat exchanger 10 comprises a tube bundle 18 situated in
the housing 12. The tubes may be prime/smooth tubes or enhanced
and/or finned tubes. The term "enhanced" is used herein to refer to
tubes having an inside surface that is enhanced by providing a fine
network of relatively closely spaced ridges that are arranged to
enhance heat transfer between the tube and the heat exchange fluid
(typically water) that flows through the tube. The term "finned"
refers to an enhanced surface on the outside of the tube in the
form of relatively finely spaced fins. Examples of enhanced tubes
are provided in U.S. Pat. No. 4,216,826 to Furukawa Metals Co.,
Ltd. and U.S. Pat. No. 4,660,630 to Wolverine Tube, Inc., which are
incorporated herein by reference and made a part hereof. The tube
may comprise any electrically conductive material, such as copper
or other suitable electrically conductive material.
[0043] The term "continuous enhanced" as used herein refers to a
tube which is enhanced and/or finned and the enhanced and/or finned
area is not periodically interrupted by a flat or smooth area.
Conventionally, the enhanced surfaces on an enhanced tube are
interrupted by smooth areas at the points of intersection with the
support and baffle sheets because conventional expanders can
overwork and crack the enhanced tube in the expanded areas. In
accordance with certain embodiments of the invention, enhanced tube
that is not interrupted by these smooth areas can be used. This has
several advantages. First, the enhanced tube is less expensive to
manufacture because it can be manufactured as continuous enhanced
tube without altering or interrupting the manufacturing process to
provide a smooth area. Second, the heat transfer efficiency of the
tube is better because a greater surface area of tube is enhanced
and/or finned. The combined effect of these two advantages should
yield significant economies.
[0044] Particularly when using enhanced/finned tube, but
potentially also with prime/smooth tube, it may be desirable to use
a sealing media such as a conventional tube or plumbing solder or
chemical sealant to seal any spaces between the tube outer surface
and the surrounding sheets. In particular, the solder or chemical
sealant will fill the spaces between the ridges and fins of an
enhanced tube as well as the spaces between these ridges and fins
and the surrounding sheets.
[0045] The tube bundle 18 comprises a first surrounding member or
tube sheet 20 and a second surrounding member or tube sheet 22. In
the embodiment being described, the tube sheets 20 and 22 are
substantially the same and support a plurality of conductive tubes
24, as illustrated in FIG. 1. For ease of description, the
invention will be described relative to tube sheet 20, but it
should be understood that tube sheet 22 comprises substantially the
same configuration. The tube sheet 20 comprises a plurality of
inner walls, such as inner walls 20a (FIG. 12) that define a
plurality of apertures 23 for receiving the plurality of conductive
tubes 24, respectively, as illustrated in FIGS. 4 and 11.
[0046] The plurality of conductive tubes 24 are secured to the tube
sheets 20 and 22 in accordance with the system and method described
later herein. After one of the plurality of conductive tubes 24 is
situated in one of the apertures 23, the system and method
according to the invention may be applied to a portion, such as
portion 24a in FIG. 6, of the conductive tube 24 to expand a
diameter of the tube 24 from a first diameter D.sub.1 (FIG. 6) to a
second diameter D.sub.2, thereby securing the tube 24 to the inner
wall 20a of tube sheet 20. Note that after the plurality of
conductive tubes 24 are secured to the tube sheets 20 and 22, they
become aligned in a generally parallel relationship, as illustrated
in FIG. 1.
[0047] To facilitate supporting the plurality of conductive tubes
24 and providing heat exchange, the tube bundle 18 also comprises a
plurality of support sheets or baffle sheets 36a-36d. The plurality
of baffle sheets 36a-36d support the tubes 24 between the tube
sheets 20 and 22 and provide a baffle to interrupt the flow of
fluid between a first inlet opening 26 and a first outlet opening
28 in the housing 12. As illustrated in FIGS. 13 and 14, each of
the plurality of baffle sheets 36a-36d comprises a plurality of
inner walls, such as inner walls 36e in sheet 36a, defining a
plurality of apertures 38, respectively, for receiving the
plurality of conductive tubes 24 as shown. The invention will be
described relative to sheet 36a, but it should be understood that
the sheets 36b-36d function and are configured in the same or
similar manner.
[0048] As described later herein, the sheets 20, 22 and 36a-36d may
be assembled with the tubes 24 to provide the tube bundle 18, which
is then situated in housing 12. Alternatively, the sheets 20, 22
and 36a-36d may be welded, for example, to housing 12 and then the
tubes 24 inserted in the apertures 23 and 38. Note that a heat
exchange area 30 is defined by the housing 12 and sheets 20 and 22.
Note also that an inlet area 32 and an outlet area 34 are provided
when the end bells 14 and 16, respectively, are situated or mounted
to the housing 12, as illustrated in FIG. 1. It should be
understood that the tube sheets 20 and tubes 24 are sealed so that
the heat exchange area 30 is not in fluid or gas communication with
either the inlet area 32 or outlet area 34. Also, note that the
plurality of conductive tubes 24 is in fluid communication with the
inlet area 32 and outlet area 34. This permits fluid to flow into
the inlet area 32 via a second inlet 14b, through the plurality of
conductive tubes 24, into outlet area 34, and exit through a second
outlet area 16b, as illustrated in FIG. 1. Substantially
simultaneously with such fluid flow through the plurality of
conductive tubes 24, a second fluid or gas is caused to flow
through the first inlet opening 26, around the tubes 24 in the heat
exchange area 30, and exit through the first outlet opening 28. The
fluid flowing through the plurality of conductive tubes 24 is of a
first temperature and the fluid flowing into the heat exchange area
30 and around the plurality of conductive tubes 24 is of a second
temperature, which is different from the first temperature, thereby
providing the desired heat exchange. In the embodiment being
described, there is a temperature difference between the second
fluid and the temperature of the fluid flowing through the
plurality of conductive tubes 24. Also, at least one of the fluids
may be a coolant, such as air, water, ethylene glycol or any
suitable cooling fluid.
[0049] As mentioned, the plurality of conductive tubes 24 are
secured to the inner walls 20a of tube sheets 20 and 22. The
plurality of conductive tubes 24 are also secured to the inner
walls, such as wall 36e of baffle sheet 36a, of baffle sheets
36a-36d (FIGS. 9 and 14) to secure the plurality of conductive
tubes 24 to the baffle sheets 36a-36d. As illustrated in FIG. 1,
the plurality of baffle sheets 36a-36d have a staggered arrangement
to facilitate interrupting a flow path of fluid between the first
inlet opening 26 and the first outlet opening 28 to facilitate heat
exchange. It should be understood that the pattern of the plurality
of apertures 38 defined by the plurality of inner walls 36e of the
baffle sheets 36a-36d corresponds to the pattern of apertures or
openings in the tube sheets 20 and 22, such as apertures 20a in
FIG. 4.
[0050] As illustrated in FIGS. 6 and 9, each of the plurality of
conductive tubes 24 is secured to the baffle sheets 36a-36d and
tube sheets 20 and 22 by enlarging a portion, such as portion 24a
(FIG. 6) and portion 24b (FIG. 9), of each plurality of conductive
tubes 24 to provide an interference fit at the intersection or
joint between the tube 24 and the walls 20a (FIG. 6) and 36e (FIG.
9). Note, for example, that the portion 24a (FIG. 6) is enlarged
from the first diameter D.sub.1 (FIG. 6) to the second diameter
D.sub.2 using the system and method of the invention. In this
regard, it should be appreciated that each of the plurality of
tubes 24 is enlarged only in the areas where the tube 24 is
surrounded by the inner walls 20a and 36e, as illustrated in FIGS.
6 and 9, respectively. By enlarging only the portions 24a and 24b
of tube 24 adjacent to the surrounding members, such as sheets 20,
22 and 36a-36d, the amount of time necessary to secure the
plurality of conductive tubes 24 to the baffle sheets 36a-36d and
tube sheets 20 and 22 is reduced. Advantageously, it should be
appreciated that the entire process may be conducted from either
end of the tube 24. Alternatively, the process may be performed so
that approximately one-half of the tube 24, beginning at one end,
is secured to surrounding members and then the coil 46a is removed
and inserted into the other end of the tube 24 so that a second
half of tube 24 may be processed from the other end.
[0051] In the embodiment being described, the baffle sheets 36a-36d
(FIG. 1) and tube sheets 20 and 22 may each comprise different
widths or thicknesses. For example, the tube sheets 20 and 22 may
have a thickness or width W.sub.1 (FIG. 6) that may vary, and the
baffle sheets 36a-36d may each comprise a thickness or width
W.sub.2 (FIG. 9) that may vary in the embodiment being described.
It should be appreciated that an outer diameter D.sub.3 (FIG. 9) of
the tube 24 is substantially the same as the diameter D.sub.1 (FIG.
6) before the tube 24 is joined to the sheet 36a, which is the only
baffle sheet joint shown in FIG. 9 for ease of illustration. After
securing the tube 24 to the sheets 20 and 36a-36d, the tube 24 in
FIG. 9 will have an enlarged diameter D.sub.4 that is substantially
the same as diameter D.sub.2 in FIG. 6 of the diameters of the
inner walls 36e and 20a, respectively, are the same. It should be
appreciated, however, that these diameters D.sub.2 and D.sub.4 may
be different and will vary depending on the diameter of the inner
walls 20a and 36a, respectively. It has been found, however, that
keeping the diameter of the inner walls 20a (FIG. 6) and 36e the
same facilitates manufacturing, assembling and repairing the heat
exchanger 10. The system and method for enlarging portion 24a and
portion 24b of each of the plurality of conductive tubes 24 to
secure the tubes 24 to the sheets 20, 22 and any surrounding sheets
36a-36d will now be described.
[0052] The system comprises a heat exchange tube expander 44 (FIGS.
1 and 7) for expanding the portion 24a (FIG. 6) and portion 24b
(FIG. 9) as shown. The heat exchange tube expander 44 comprises a
coil 46 which is conductively coupled to circuit 48 (FIG. 10) by an
insulated cord 55 (FIG. 8) comprising a pair of conductors 50 and
52. The coil 46 may be a solenoid. Note that the circuit 48 is
housed in a suitable housing 54 (FIGS. 2 and 7) that comprises a
plurality of wheels 58, so that the heat exchange tube expander 44
is portable. As illustrated in FIG. 7, the heat exchange tube
expander 44 may comprise a take-up mechanism 60, such as a reel or
basket, for storing the insulated cord 54.
[0053] In the embodiment being described, the solenoid or coil 46
comprises a coil 46a which, as mentioned above, is coupled to the
conductors 50 and 52 (FIG. 10). To facilitate moving the coil 46a
into position, the coil 46a may be turned around a nonconductive
tubular mandrel 62 (FIG. 5). In the embodiment being described, the
nonconductive mandrel 62 is tubular and is made of glass fiber
reinforced epoxy and may be sized to the tube inside diameter,
depending on the inner diameter D.sub.5 (FIG. 6) of the tube 24. In
one embodiment, the coil 46a is housed with a sensor 132 (FIG. 17)
as described later.
[0054] Referring now to FIG. 10, notice that the circuit 48
comprises a capacitor bank 64 that is coupled in series to a switch
66, a first resistor R.sub.S, first inductor L.sub.S and load
inductor L.sub.L, as shown. In the embodiment being described, the
load inductor L.sub.L is the coil 46a (FIGS. 4, 5 and 7). The coil
46a has a coil length C.sub.L1 (FIG. 4) that generally corresponds
to the width W.sub.1 (FIG. 6) of the sheet 20 so that the portion
24a is expanded to engage the entire surface of inner wall 20a of
sheet 20. This provides an interference fit over the entire joint
between tube wall 24c (FIG. 6) and inner wall 20a. Likewise, the
heat exchange tube expander 44 may comprise a second solenoid 70
having a second coil 70a (FIGS. 8 and 9) comprising a second coil
length C.sub.L2 that corresponds to the width W.sub.2 (FIG. 9) of
the baffle sheets 36a-36d. Thus, it should be understood that the
lengths C.sub.L1 and C.sub.L2 of coils 46a and 70a are selected in
response to the widths W.sub.1 (FIG. 6) and W.sub.2 (FIG. 9),
respectively. Of course, widths W.sub.1 and W.sub.2 may vary
depending on the sheets 20, 22 and 36a-36d used in the heat
exchanger 10.
[0055] In the embodiment being described, the coils 46a and 70a
each comprise 16 AWG square magnet wire. The coil 46a, for example,
comprises at least 20 turns over a length C.sub.L1 of about one
inch, and the coil 70a comprises at least 20 turns over a length
C.sub.L2 of about one inch. Thus, the coils 46a and 70a are of
similar construction, but in the embodiment being described they
are operated at different power levels. It should be appreciated
that the coils 46a and 70a may be of different construction if
desired. The nominal inductance for the coils 46a and 70a is
approximately 0.64 microhenries when inserted into one of the tubes
24. The nominal outside diameter of the coils 46a and 70a is
slightly less than the diameter D.sub.5 (FIG. 6) of the tube 24 so
that the coils 46a and 70a can easily slide or pass through the
passageway 24e of tube 24.
[0056] The capacitor discharge bank 64 of circuit 48 is capable of
storing enough energy to perform the enlargement of the portion 24a
(FIG. 6) and portion 24b (FIG. 9). It should be appreciated that
the capacitor discharge bank 64 of circuit 48 is charged to an
appropriate voltage level that will vary depending on, for example,
the characteristics of the coil 46a, the portion 24a and portion
24b of the tube 24 to be enlarged, the characteristics of the
sheets 20, 22 and 36a-36d and the like. During operation, the
capacitor discharge bank 64 is charged by the power source 68 (FIG.
10). The switch 66 is then triggered to start current to flow
through the coil 46a or coil 70a, depending on which coil that is
being used. Through magnetic induction, the current flowing through
the coil 46a induces an eddy current in the portion 24a that is
directly opposed to the current flowing in coil 46a. This causes an
electromagnetic expansion force that pushes or forces the portion
24a radially outwardly in the direction of arrows 71 and 72 (FIG.
5). This outward radial expansion of the portion 24a of tube 24
continues until the outer wall 24d (FIG. 6) of tube 24 impacts the
inner wall 20a of sheet 20. It has been found that the radial
expansion of the portion 24a of tube 24 impacts the inner wall 20a
and causes the inner wall 24a to radially expand from its normal
diameter D.sub.2 to a slightly larger diameter. As the sheet 20
recovers from the impact from the wall 24d, the wall 20a will
return or contract to substantially its original diameter D.sub.2,
thereby providing an interference pressure fit between the outer
wall 24d of tube 24 and the inner wall 20a of sheet 20. This
interference pressure can be of significant magnitude to allow
scaling between the outer wall 24d of tube 24 and the inner wall
20a of sheet 20. This process and method is repeated at each
intersection or joint between the tubes 24 and the inner walls of
any surrounding members such as sheets 20 and 36. A method for
assembling, manufacturing and repairing the heat exchanger 10 using
the invention will now be described.
[0057] Referring to FIG. 17A, a detector and coil assembly 107 is
shown. The assembly 107 comprises the sensor 132 for sensing the
sheet 20, 22 and 36a-36d and the coil 46a. The assembly 107
comprises the coil 46a which is received in an insulated
termination housing 110. It is envisioned that the coil 46a can be
detachably removed from the housing 110 so that it can be replaced,
substituted, serviced, or the like. Advantageously, the invention
comprises a coaxial cable 114 having the conductors 50 and 52
formed of wire braids. As illustrated in FIG. 18, the coaxial cable
114 comprises an insulator 116, the conductor 50, an insulator 118,
the conductor 52, an insulator 120, and a sensor bundle 122, which
will be described later herein.
[0058] Notice that the cable 114 terminates into a cable
termination housing 124 which provides a first mount 126 and a
second mount 128. The first and second mounts 126 and 128 have
recessed areas 126a and 128a (FIG. 17B) for receiving and
conductively coupling to a complementary first coil end 46a1 and a
complementary second coil end 46a2, respectively, of coil 46a. Note
that the coil terminal ends 46a1 and 46a2 are separated by an
insulator 112 and conductively engage the first and second mounts
126 and 128, and they each may comprise a plurality of apertures,
such apertures 127a-127c of first mount 126, which become aligned
so that they can be conductively coupled together with any suitable
fastener or fastening means, such as a screw or bolt, weld or the
like. This allows for a quick connection and disconnection of the
coil ends 46a1 and 46a2 from the coaxial cable mounts 126 and 128,
respectively.
[0059] A permanent magnet 130 is attached to the cable termination
lug or mount 126 as shown. In the embodiment being described, the
permanent magnet 130 generates a magnetic flux which is interrupted
by a sheet 20, 22 or 36a-36d as the assembly 107 is moved through
the tube 24. The coaxial cable 114 comprises the sensor 132 (FIGS.
10 and 17) that is coupled to the sensor bundle 122 (FIG. 18)
contained in the center of the coaxial cable 114. The sensor 132 is
a Hall effect sensor, but could comprise any suitable sensor
capable of sensing the sheets 20, 22 and 36a-36d. The sensor 132 is
positioned on the cable 114 so that when the connection to the coil
46a is made, the sensor 132 is positioned at an appropriate working
distance from the permanent magnet 130.
[0060] The Hall effect sensor 132 cooperates with the permanent
magnet 130 to sense a position of one of the sheets 20, 22 or
36a-36d as the assembly 107 is moved through the tube 24. In this
regard, note that the sensor 132 is situated a predetermined
distance SD from the magnet 130. When sensor 132 senses a sheet 20,
22 or 36a-36d, the sensor bundle 122 carries the signal to a
controller 49 (FIG. 10) for controlling operation of the assembly
107 and power supply 68. In response, the controller 49 will
energize a display 51 or alarm (not shown) to indicate that the
coil 46a is operatively positioned to enlarge at least a portion of
the tube 24 as described herein. The display 51 may be an LCD or
other type of suitable display. The enlargement of at least a
portion of tube 24 may then proceed to the next sheet 20, 22 and
36a-36d.
[0061] It should be understood that the first mount 126 is coupled
to a negative side of the power supply 68 (FIG. 10), and the second
mount 128 is coupled to a positive side of power supply 68. The
pulse power will be fed to the coil 46a via the braided conductors
50 and 52. The cable 114 is designed to have voltage hold-off
capability of at least 10 kV. Both braided conductors 50 and 52 are
sized to have a cross-sectional area to safely carry a pulse
current to a peak value of at least 35 kA at a rate of one pulse
per five seconds or faster.
[0062] When required, a solder or sealing material (not shown) may
be applied to the tube surface before forming the joint. Upon
expansion of the tube 24, the solder or sealant melts or softens
and the tube 24 presses the solder or sealant into the joint so as
to fill any open spaces.
[0063] Advantageously, this system and method provides an assembly
107 for detecting or sensing a location of a sheet 20, 22 or
36a-36d and for enlarging at least a portion of tube 24. Note that
the assembly 107 and cable 114 can be easily and quickly moved and
positioned in and through tube 24. Also, the sensor bundle 122
(FIG. 18) and the braided conductors 50 and 52 are formed into a
bundle which is centrally located within the insulator 116. This
facilitates reducing the diameter of assembly 107. The method or
process of the invention will now be described.
[0064] The method begins (block 74 in FIG. 16) by providing a
plurality of sheets, such as sheets 20, 22 and 36a-36d that are
secured to the housing 12. At block 76, the plurality of conductive
tubes 24 are situated in the apertures 23 and 38 (FIG. 8) and
between the sheets 20 and 22, as illustrated in FIGS. 1-3. The coil
46a is then aligned with the tube passageway 24e (FIG. 4) and
inserted (block 78 in FIG. 16) into the passageway 24e of the tube
24. The coil 46a is then moved to a first position 96 (FIG. 7)
until it is aligned with the sheet 20, as illustrated in FIG. 5. At
this position, the coil 46a becomes generally aligned with the
inner wall 20a of the sheet 20 in the illustration. As illustrated
in FIG. 7, a plurality of other positions 98, 100, 102 and 104
correspond to a plurality of other positions or imaginary planes in
which the baffle sheets 36a-36d may be situated. Similarly, the
sheet 22 lies in an imaginary plane 106 and corresponds to another
position at which solenoid 46a may be moved. For ease of
description, only the fastening of portion 24a (FIG. 6) to tube
sheet 20 is described, but it should be appreciated that the same
technique is used to secure each tube 24 to any surrounding member,
such as inner walls 20a and 36a.
[0065] Returning to the illustration, after the coil 46a is moved
(block 80 in FIG. 16) to the first position 96 (FIG. 7) and
generally aligned with the wall 20a of sheet 20, a user actuates
switch 66 or if in automatic mode the device detects a sheet (FIGS.
2, 7 and 10) energizes the coil 46a. As a pulse of current flows
through the coil 46, an opposite flowing eddy current is induced in
the tube 24. This results in magnetic pressure acting on the tube
24 to expand the portion 24a of the tube 24 that is opposed to the
coil 46a to expand or be forced radially outwardly in the direction
of arrows 71 and 72 until the outer wall 24d (FIG. 6) of tube 24
engages the inner wall 20a of sheet 20, thereby securing the
portion 24a of tube 24 to the inner wall 20a of sheet 20. It may be
desirable to repeatably pulse the current through the coil 46a,
particularly if a large distance between the wall 24c and inner
wall 20a exists. In the embodiment described, the current is pulsed
for approximately 20 micro seconds.
[0066] The coil 46a is then moved (block 84 in FIG. 16) to the next
position, such as position 106 for coil 46a, where the coil 46a is
again energized (block 86 in FIG. 16) to secure the tube 24 to the
tube sheet 22. As mentioned earlier herein, if a width W.sub.1
(FIG. 4) of sheet 20 is different than the width W2 (FIG. 8) of
sheet 36, then it may be desirable to use a different coil, such as
the coil 70a at the positions 98-104 (FIG. 7). Preferably a coil
having the length C.sub.L2 corresponding to the width W.sub.2 (FIG.
9) of the baffle sheet 36a should be used. This coil 70a would be
used for each of the positions 98, 100, 102 and 104 to secure each
of the plurality of tubes 24 to the inner walls, such as inner wall
36e of baffle sheet 36a, of any surrounding baffle sheets 36a-36d.
At decision block 88, it is determined whether the process is
complete at all positions. If it is, the process proceeds as shown,
but if not, the process loops back to block 84. As mentioned
earlier, the process can be conducted from only one of the ends 12c
or 12d, or from both ends 12c and 12d.
[0067] In the example, the solenoid or coil 46a traverse the entire
length L of tube 24 creating tube sheet joint at each position
where the sheets 20 and 22 surround the tube 24. The system then
automatically traverses the solenoid or coil 46a in an opposite
direction and the tube 24 is expanded at each position where a
baffle plate 36a-36d surrounds it. Automatic positioning may be
accomplished using the sensor (FIG. 7) mentioned earlier. The
traverse speed through the tube may be on the order of about 60
feet/minute, but this speed could be higher or lower if
desired.
[0068] It is contemplated that the system and method of the
invention can be used to manufacture or assemble the tube bundle 18
comprising the sheets 20, 22 and 36a-36d secured to the plurality
of tubes 24 outside of housing 12, as alluded to earlier herein.
The assembled tube bundle 18 is then mounted in the surrounding
housing 12. Alternatively, the housing 12 may be provided with one
or more of the sheets 20, 22 or 36a-36d mounted therein. The
plurality of conductive tubes 24 are then inserted in the sheets
20, 22 and 36a-36d. In this case, the system and method is used to
secure the plurality of conductive tubes 24 to the sheets 20, 22
and 36a-36d after the plurality of conductive tubes 24 are situated
in apertures 23 and 38, as mentioned in the illustration.
[0069] If the tube bundle 18 is assembled outside of the housing
12, then the routine proceeds to block 90 in FIG. 15 where the tube
bundle 18 is situated in the housing 12 and the sheets 20 and 22
are secured to the housing 12 (block 92). The first header or end
bell 14 and a second header or end bell 16 are then secured to the
housing 12 by bolting the flanges 14a and 16a to the flanges 12a
and 12b, respectively, as shown in FIG. 1.
[0070] It should be appreciated that the heat exchange tube
expander 44 may further comprise a sensor 108 (FIG. 7) for sensing
the positions 96-106 to facilitate a quick alignment of the coils
46a and 70a in the various imaginary planes in which the sheets 20,
22 and 36a-36d lie. One example of such a sensor is the Hall effect
sensor 122 (FIG. 17) or eddy current probe, such as is shown by
U.S. Pat. No. 4,889,679 which is incorporated herein and made a
part hereof.
[0071] In one embodiment, the tube 24 is expanded into the
apertures 23 in the sheets 20 as the coil 46a is in motion in the
tube 24. Upon energizing the coil 46a, the tube 24 expands almost
instantaneously. Accordingly, it is not necessary to bring the coil
46a to a complete stop each time a joint is formed. The coil 46a
can be automatically activated each time the coil 46a aligns with
the sheet 20 by coupling the coil 46a with the sensor mentioned
herein or by closing the switch 66 in the coil circuit 48 each time
the coil 46a travels to a pre-measured point in the tube 24. In
either case, in this embodiment, as the coil 46a travels
continuously through the tube 24, the tube 24 is automatically
energized and the tube 24 is expanded "on the fly," without
stopping. Of course, those skilled in the art will appreciate that
if necessary, the coil 46a could be slowed as it aligns with each
sheet 20 or the coil 46a could momentarily stop. However, for many
tube designs and constructions, it will be possible to form joints
"on the fly" while the coil 46a is moving.
[0072] Although the embodiment described and shown herein shows a
plurality of coils 46a and 70a, it should be appreciated that more
or fewer coils may be used if desired. Also, the coils 46a and 70a
may be comprised of different gauge wire, different lengths,
different number of turns and the like.
[0073] It should further be appreciated that the system and method
of the present invention may be used to assemble and manufacture a
heat exchanger 10 and may be used to repair any intersection or
joint between the tube 24 and one of the sheets 20, 22 and 36a-36d.
During repair, one or both of the end bells 14 and 16 must be
removed to gain access to the tubes 24.
[0074] A further feature of Applicants' invention is that the heat
exchange tube expander 44 comprises a plurality of wheels 58
secured to housing 56 so that it can be moved, for example, from
the first end 12c (FIG. 2) to the second end 12d (FIG. 3). This is
particularly convenient when assembling, manufacturing or repairing
heat exchangers having a length L (FIG. 1) over 96 inches. The heat
exchange tube expander 44 may be used from either one of the ends
12c or 12d or both ends 12c or 12d as mentioned previously,
whereupon the coil 46a would be moved through the entire tube 24,
which time is saved in not moving the expander to the opposite end
of the heat exchanger. Alternatively, the heat exchange tube
expander 44 may be used at one of end 12c to, for example, expand
portions over the approximately one-half a length (i.e. --to the
middle of the tube 24) of tube 24, withdraw the coil 46a, whereupon
the coil 46a may be inserted into the tube from the opposite end
12d and then energized to expand portions of the second half of
tube 12.
EXAMPLE
[0075] One example of Applicants' invention will now be described.
Applicants used a tube 24 having a nominal outside diameter of 0.74
inches and a nominal inside diameter of 0.59 inches. The coil 46a
was made from 16 AWG square magnet wire and consisted of 22 turns
over a length of about 1.25 inches. The nominal inductance for the
coil 46a was approximately 0.5 microhenries when inserted into the
tube 24. The outside diameter of the coil 46a was about 0.565 inch.
The coil 46a was connected to the circuit 48 that had a capacitor
discharge bank 64 having a total capacitance of about 50
microfarads. The capacitors (not shown) comprising the capacitor
discharge bank 64 were charged to a voltage of about 7.5 kV
resulting in a total current of about 35 kA through the coil 46a.
The total stored energy based on these values was approximated at
1406 Joules.
[0076] The coil 46a was inserted into the tube 24 and positioned in
operative relationship with the wall 20a of sheet 20, with the tube
24 situated therebetween. It should be appreciated that the inner
wall 20a had a diameter of about 0.76 inch, and the sheet 20 had a
thickness or width W.sub.1 (FIG. 6) of approximately 1.25 inches.
The switch 66 was triggered which induced a current to flow through
coil 46a. This, in turn, caused the portion 24a to impact inner
wall 20a as it expanded. As the wall 20a recovered to substantially
its original dimension (D.sub.2 in FIG. 6), it caused an
interference pressure between the surface 24d (FIG. 5) and the
inner wall 20a. The interface pressure was significant enough to
secure the tube 24 to the sheet 20. Preferably, transport
apparatuses analogous to the devices used to transport mechanical
tube expanders used in the past may be employed for transporting
the detector assembly 107 (FIG. 17) and coil 46a.
[0077] In the example being described, the total stored energy was
1400 Joules, total capacitance was 50 microfarads and the total
load inductance L.sub.L in the tube 24 was about 0.5 microhenries.
The total system inductance L.sub.S was about 1.4 microhenries and
total system resistance R.sub.S was 10-20 milliohms with a peak
current of about 35 kA in tube 24. The coil 46a was driven with a
ringing pulse lasting approximately 200 microseconds. The rise time
of the first current peak is 10-20 microseconds. Most of the
forming or expansion of the tube 24 occurs during the first
peak.
[0078] FIG. 15 illustrates further expansion result data for an
enhanced heat transfer tube 24. The x-axis of the chart in FIG. 15
represents a peak magnetic pressure applied and the y-axis
correlates to the expansion results. Note that as the current
increased, the bulge diameter of the tubes 24 increased. For
example, significant expansion was not observed until a current of
at least 15 kA/mm after this level, the diametrical expansion
increased approximately linearly to a value of nearly 2 mm at a
current of 25 kA/mm.
[0079] Although the embodiment has been shown and described
relative to an illustrative embodiment, a particular example and
some particular data to illustrate various features of the
invention, it should be appreciated that the various values
achieved may change depending on the coil 46a or 70a used;
thickness of tube 24; the inner and outer diameters of the tube 24;
the dimensions D.sub.1-D.sub.4, W.sub.1, W.sub.2, C.sub.L1 and
C.sub.L2; the material comprising the tube 24 and the sheets 20,
22, 36a-36d and the like. In the embodiment being described, the
components of the circuit 48 may also change. What is important,
however, is that the coil used be configured to be capable, through
magnetic induction, to expand at least that portion 24a (FIG. 6)
and portion 24b (FIG. 9) of tube 24 to engage and secure the tube
24 to the sheet 20, 22 or 36a-36d that surrounds the tube 24.
[0080] In the embodiment being described, the tubes 24 are copper
and comprise a length of about 240 inches and have an outer
diameter of about 3/4 inch. The tubes 24 may comprise internal
spiral ridges and external formed fins (not shown) to further
facilitate heat exchange. The distance between the sheets 20 and 22
and varies depending on the heat exchanger manufacturers
requirements and TEMA Standards. The heat exchanger 10 comprises
four baffle sheets 36a-36d in the embodiment shown, but it could
comprise more, fewer, or even no baffle sheets 36a-36d as required
by TEMA Standards for heat exchanger construction. Moreover, a
distance between the position of the sheets 20, 22 and 36a-36d,
such as a distance between position 96 and 98 or a distance between
position 100 and 102 in FIG. 7, is approximately 19 inches in the
embodiment being described. Of course, this distance could be
varied depending on, for example, the number or sheets 36a-36d or
the interference of the fluid flow pattern desired as specified by
the heat exchanger manufacturer.
[0081] Heat exchangers are manufactured in a variety of lengths,
diameters, quantity of tubes and heat transfer medias. These
configurations are established by the heat exchanger manufacturer
and are derived from end user requirements.
[0082] Other means for magnetically expanding tube 24 can also be
used. One such means is referred to herein as a direct drive
expander in which FIGS. 19 and 20 illustrate another embodiment of
the invention. It should be understood that like parts and parts in
this embodiment are identified with the same part numbers, except
that an apostrophe ("'") has been added to part numbers in FIGS. 19
and 20. It should be understood that in this embodiment, a direct
drive expander 133' is provided for enlarging at least the portion
24a' (FIG. 6) of tube 24'. The direct drive expander 133' comprises
a core conductor 134'. The conductor 134' is coupled to a first
compliant contact 136' at a first end 134a'. A second compliant
contact 138' is situated on a second end 134b' of conductor 134'.
Notice in FIG. 19 that an insulator 140' is situated between the
second compliant contact 138' and the conductor 134' as shown. The
conductor 134' is coupled to a positive side of the power supply
68' (FIG. 10), and the conductor 138' is coupled to the negative
side of the power supply 68'.
[0083] Each of the first and second compliant contacts 136' and
138' comprise a brush 136a' and 136b' for providing a continuous
contact with the portion of the inner wall of tube 24' that lies in
a first plane FP and second plane SP, respectively, as illustrated
in FIG. 19.
[0084] During use, the direct drive expander 133' is situated in
operative relationship with the sheet 20' as illustrated in FIG.
19. For this purpose, a sensor, such as sensor 132' (FIG. 10), may
be employed with the direct drive expander 133' to align it with a
sheet 20', 22' or 36a'-36d'. After the direct drive expander 133'
is situated in operative relationship with the sheet 20', the
switch 66' (FIG. 10) may be closed to cause electric current to
flow through the conductor 134' in the direction of arrow 144' as
illustrated. The current flows from the first contact 136' through
the tube 24', through the second contact 138' and then back to the
power supply 68'. When the electrical current flows in the manner
illustrated by the arrows 144', electromagnetic pressure is created
upon the wall of tube 24'. When the magnetic pressure is applied,
the tube 24' expands in a radial direction, as illustrated in FIG.
20. As the diameter of the tube 24' increases, it ultimately
engages the inner wall 20a' to secure the tube 24' to the sheet 20'
as shown.
[0085] It should be appreciated that the first and second contacts
136' and 138' may be comprised of compliant brushes which may be
flexible to permit the direct drive enlarger 133' prime to be
driven through the tube 24' either manually or with a feeding
mechanism (not shown). The direct drive expander 133' may also be
used with the cable 114' described earlier.
[0086] Advantageously, these systems and methods provide means for
manufacturing, assembling and even repairing a tubular heat
transfer system 10. The system and method further provides means
for expanding a dimension of a tube 24 in a tube bundle 18 or used
in a tubular heat transfer system 10 to facilitate securing the
tube 24 to one or more of the sheets 20, 22 and 36a-36d situated in
the tubular heat transfer system 10 by magnetically expanding at
least a portion of the tube 24. This technique is believed to be
superior to techniques, such as mechanical expansion techniques, of
the past. The system and method improve the means by which tubes 24
are secured to one or more of the sheets 20, 22 and 36a-36d in a
tubular heat transfer system 10 and improve the joints between the
tubes 24 and any surrounding walls, such as wall 20a of sheet
20.
[0087] While the systems and methods herein described, and the
forms of apparatus for carrying these systems and methods into
effect, constitute one embodiment of this invention, it is to be
understood that the invention is not limited to these precise
methods and forms of apparatus, and that changes may be made in
either without departing from the scope of the invention, which is
defined in the appended claims.
* * * * *