U.S. patent application number 12/429256 was filed with the patent office on 2009-08-13 for support for a tube bundle.
Invention is credited to Stephen Wayne Johnston, Dominicus Fredericus Mulder.
Application Number | 20090200004 12/429256 |
Document ID | / |
Family ID | 34707280 |
Filed Date | 2009-08-13 |
United States Patent
Application |
20090200004 |
Kind Code |
A1 |
Johnston; Stephen Wayne ; et
al. |
August 13, 2009 |
SUPPORT FOR A TUBE BUNDLE
Abstract
A support for a bundle of tubes, which support has more than one
transverse support plates spaced apart along the direction of the
tubes to be supported, and which support plates are provided with
openings for accommodating the tubes, wherein the support plates
are segmental baffle support elements and expanded metal support
elements.
Inventors: |
Johnston; Stephen Wayne;
(Sugarland, TX) ; Mulder; Dominicus Fredericus;
(Amsterdam, NL) |
Correspondence
Address: |
SHELL OIL COMPANY
P O BOX 2463
HOUSTON
TX
772522463
US
|
Family ID: |
34707280 |
Appl. No.: |
12/429256 |
Filed: |
April 24, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11018719 |
Dec 21, 2004 |
|
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12429256 |
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Current U.S.
Class: |
165/172 ;
165/178 |
Current CPC
Class: |
F28F 2009/226 20130101;
F28F 9/0136 20130101; F28F 9/0131 20130101; F28F 9/22 20130101;
F28D 7/16 20130101 |
Class at
Publication: |
165/172 ;
165/178 |
International
Class: |
F28F 1/10 20060101
F28F001/10; F28F 9/013 20060101 F28F009/013 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 22, 2003 |
EP |
03104881.2 |
Claims
1. A heat exchanger comprising a bundle of tubes supported by a
plurality of support elements transverse to and spaced apart along
the direction of the tubes to be supported, said plurality of
support elements comprising at least one double segmental expanded
metal support element.
2. The heat exchanger of claim 1, wherein said plurality of support
elements additionally comprises at least one single segmental
baffle support element.
3. The heat exchanger of claim 2, wherein two of the plurality of
support elements are single segmental baffle support elements and
as least one double segmental expanded metal support element is
arranged intermediate thereto.
4. The heat exchanger of claim 1, wherein said heat exchanger
comprises a vertical heat exchanger.
5. The heat exchanger of claim 4, wherein a plurality of double
segmental expanded metal support elements are arranged intermediate
to two single segmental baffle support elements
6. The heat exchanger of claim 1, wherein the double segmental
expanded metal support element is formed from a double segmental
metal sheet, which is welded to a support ring and support strips
so as to form a double segmental expanded metal support element
having two windows.
7. The heat exchanger of claim 5, wherein each of the plurality of
double segmental expanded metal support elements is formed from a
double segmental metal sheet, which is welded to a support ring and
support strips so as to form a double segmental expanded metal
support element having two windows.
8. The heat exchanger of claim 7, wherein there are no tubes in the
windows formed by the single segmental baffle support elements or
the double segmental expanded metal support elements.
9. The heat exchanger of claim 8, wherein said heat exchanger
comprises a vertical heat exchanger.
10. The heat exchanger of claim 5, wherein the spacing between the
single segmental baffle support elements is approximately 1.5
meters.
Description
[0001] This application is a division of application Ser. No.
11/018,719, filed Dec. 21, 2004, pending.
FIELD OF THE INVENTION
[0002] The present invention relates to a support for a bundle of
tubes, in particular to such a support comprising a plurality of
transverse support plates known as segmental baffles, which are
spaced apart along the direction of the tubes to be supported.
BACKGROUND OF THE INVENTION
[0003] A major area of application of the tube bundle is in
shell-and-tube heat exchangers. A shell-and-tube heat exchanger
comprises a cylindrical vessel internally provided with a bundle of
tubes that extend in longitudinal direction of the vessel. The
bundle of tubes can in particular be a bundle of parallel tubes,
and is also referred to as a tube bundle.
[0004] As is well known, the shell-and-tube heat exchanger is an
indirect heat exchanger in which heat is transferred between a
fluid passing through the tubes of the tube bundle (the tube side)
and a fluid passing through the space outside the tubes (the shell
side). Details of the shell-and-tube heat exchanger can, for
example, be found in Perry's Chemical Engineers' Handbook, 6.sup.th
edition, 1984, McGraw-Hill Inc., page 11-3 to 11-21. The tube
bundle is the most important part of the heat exchanger. The ends
of the tubes are secured to a tube sheet. The heat exchanger can
include two tube sheets, one at each end of the cylindrical vessel,
or a single tube sheet at one end of the cylindrical vessel in the
event the heat exchanger is a U-tube exchanger.
[0005] It will be understood that the intermediate portions of the
tubes have to be supported as well, for example to prevent damage
to the tubes due to vibrations caused by the fluid flow. To support
the intermediate portions of the tubes, a tube support normally
comprises axially spaced apart transverse support plates. A support
plate is sometimes also referred to as a support sheet or a support
baffle.
[0006] One type of support plate is a segmental baffle. Several
kinds of segmental baffles are discussed in Perry's. Conventional
segmental baffles are made of a circular metal plate from which a
circle segment ("window") is cut off, and through the remainder of
the plate a plurality of openings is punched or cut through which
the tubes can pass. Sometimes two circle segments are cut off at
opposite sides, for example for use in so-called double segmental
baffle arrangements, or in no-tube-in-window arrangements.
[0007] Segmental baffles not only support the tubes, but also
influence the fluid flow through the shell side. Therefore, the
design of a baffle is also determined by heat-transfer
considerations. Segmental baffle tube supports are used when a
certain amount of cross-flow of fluid in the shell over the tube
bundle is desired for reasons of optimizing heat transfer.
[0008] The design of segmental baffles can be adapted, within
certain limits, to the specific requirements of a particular
practical application. For example the so-called baffle cut can be
specifically selected, which is the percentage of the circle
diameter which has been cut off to form the segmental baffle. A
large baffle cut in a single segmental baffle provides a relatively
low pressure drop, however the relatively large part of the tubes
that run through the window remains unsupported. Normally one tries
to support a tube by at least every second segmental baffle, so
that the maximum baffle cut that is normally adopted is 45%.
[0009] When tubes run through the windows, the maximum unsupported
length of a tube ("unsupported tube length") is at least twice the
spacing between segmental baffles. Therefore it is inherent with
the segmental baffle tube supports that the number of support
plates is at least twice of that which would be required from a
mechanical support point of view alone. Segmental baffles
contribute substantially to the cost of a heat exchanger, so one
tries to maximize the spacing between baffles. When the unsupported
tube length becomes too large, this can lead to vibration
problems.
[0010] In other heat exchanger designs no tubes run through the
windows. For example, in very tall vertical heat exchangers (such
as those which are referred to as "Texas towers", used e.g. as
feed/effluent heat exchangers in large-scale industrial processes),
single segmental baffles are commonly arranged at a certain
spacing, with the windows alternatingly at opposite sides in order
to achieve a desired cross-flow pattern of the fluid over the tube
bundle along the shell. Since the spacing that is desired for
reasons of optimum fluid flow and optimum hydraulic performance (in
particular minimum pressure drop) can be much longer than the
spacing required for good mechanical support against vibrations, a
number of additional segmental support baffles, but with two
windows each, are placed in between the single segmental baffles.
These additional elements represent a considerable cost element of
the entire tube support.
[0011] Japanese Patent Application with publication No. 05-296680
describes a support baffle plate wherein a plurality of
co-operating sheet metal strips are arranged in the window to
suppress vibration. Due to the special shape required for all
individual sheet metal strips, manufacturing costs are high.
[0012] Tube supports consisting solely of expanded metal support
elements are disclosed in International Patent Application
Publication No. WO 03/067170. However, this publication does not
refer to vibration problems in conventional segmental baffle heat
exchangers.
[0013] It would be useful to provide a support for a bundle of
tubes, which allows a simpler, cheaper mechanical support against
vibrations in segmental baffle tube supports.
SUMMARY OF THE INVENTION
[0014] The present invention is directed to a support for a bundle
of tubes, which support comprises a plurality of transverse support
plates spaced apart along the direction of the tubes to be
supported, and which plates are provided with openings for
accommodating the tubes, wherein the plurality of support plates
comprises segmental baffle support elements and expanded metal
support elements.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 shows schematically a longitudinal cross-section
through a first embodiment of a heat exchanger with support
according to the present invention.
[0016] FIG. 2 shows schematically a cross section along II-II in
FIG. 1.
[0017] FIG. 3 shows schematically a cross section along III-III in
FIG. 1.
[0018] FIG. 4 shows schematically a segmental support baffle.
[0019] FIG. 5 shows schematically a combined support baffle formed
of a segmental baffle support element and an expanded metal support
element.
[0020] FIG. 6 shows schematically a longitudinal cross-section
through a second embodiment of a heat exchanger with support
according to the present invention.
[0021] FIG. 7 shows schematically a cross section along VII-VII in
FIG. 6.
[0022] FIG. 8 shows schematically a cross section along VIII-VIII
in FIG. 6.
[0023] FIG. 9 shows schematically another segmental support
baffle.
[0024] FIG. 10 shows schematically a conventional segmental baffle
for use as intermediate support plate in a Texas tower.
[0025] FIG. 11 shows schematically an intermediate expanded metal
support plate according to the invention.
[0026] FIG. 12 shows schematically a longitudinal cross-section
through a third embodiment of a heat exchanger with support
according to the present invention.
[0027] FIG. 13 shows schematically a further expanded metal support
element according to the invention.
[0028] Like reference numbers are used in the Figures to refer to
the same or similar objects.
DETAILED DESCRIPTION OF THE INVENTION
[0029] Part of the mechanical support function in a segmental
baffle tube support does not have to be provided by conventional
segmental baffle elements, but may with advantage be provided by
expanded metal elements. Expanded metal may be manufactured
considerably more cheaply than segmental baffles because less
material is used, fewer cuttings are produced, and less labor is
required. The present invention allows the tube support to be
designed such that the segmental baffles are placed where they are
needed for reasons of fluid flow, as well as where they also
provide mechanical support. Further mechanical support, in
particular to prevent vibrations, may be provided by expanded metal
elements. Expanded metal influences fluid flow far less than a
conventional segmental baffle.
[0030] The invention in this way allows far more flexibility in
designing segmental baffle heat exchangers. The basic design
parameters of the heat exchanger like tube size and arrangement
(e.g. triangular or square pitch), shell diameter, segmental baffle
size and spacing, may be chosen for optimum fluid flow, heat
transfer performance and pressure drop, not compromised by
vibration considerations. A vibration problem that might be
encountered may, according to the invention, be solved by placing
expanded metal support elements.
[0031] The expression "support element" is used in the description
and in the claims to refer to a part of a support plate, or to a
full support plate.
[0032] Expanded metal and segmental baffle support elements
together may form a combined support plate. To this end expanded
metal may be arranged to span the window(s) of the segmental baffle
support element. In this way mechanical support may be provided
over the full cross-section of the support plate, but fluid may
only flow through the window. Since the expanded metal also imposes
some small flow restriction, it may be desirable to slightly
increase the size of the window compared to a conventional
segmental support baffle.
[0033] Expanded metal support elements in the form of expanded
metal support plates may also be arranged between two segmental
baffle support elements, as an additional mechanical support.
[0034] In a further embodiment, the expanded metal support plate
may have a segmental shape itself, i.e. one or more segments may be
cut off so that one or more windows are formed. This may be
advantageous in designs where no tubes run through the windows of
segmental baffles, and where additional mechanical support between
segmental baffles is desired with a minimum disturbance of fluid
flow.
[0035] Reference is now made to FIGS. 1-5. FIG. 1 shows part of a
vertical shell-and tube heat exchanger 1 in longitudinal
cross-section, and FIGS. 2 and 3 show two cross-sections along
lines II-II and III-III, respectively. The heat exchanger 1 has a
shell 3 and a bundle of tubes 5, of which the tubes
8,9,10,11,12,13,14 are visible in FIG. 1. The support for the tube
bundle 5 comprises the four support plates 18,19,20,21 shown in
FIG. 1. The plates are spaced by a fixed distance L.sub.1 from each
other along the length direction of the tubes 8-14.
[0036] Support plates 18,19 and 21 are conventional segmental
baffles as shown enlarged in FIG. 4. These segmental baffles are
manufactured from a circular plate 25 from which a segment has been
cut off so that windows are formed when mounted in the heat
exchanger, e.g. window 28. Openings 30 have been cut into the
remaining plate 25.
[0037] Support plate 20 is a combined support plate, as shown in
FIG. 5 in more detail. The combined support plate 35 is formed of a
segmental baffle support element 38 and an expanded metal support
element 40 which spans the window 42 left open by the segmental
baffle support element 38. The expanded metal element 40 may for
example be welded to the segmental baffle element 38 and to the
strip 45 around the window 42. The strip 45 itself may also be
welded to the segmental baffle element, but may also be a remainder
from the original circular plate from which the segmental baffle
element 38 was formed by e.g. milling.
[0038] Expanded metal may be made by providing sheet metal with a
structure of slits followed by stretching the slit sheet metal. A
structure of cross-laths, formed of so-called strands and bonds,
with interstices is formed. The arrangement and length of the slits
as well as the extent of stretching determines the size, shape and
relative arrangement of the interstices, which can therefore be
designed such that the tubes can pass through them and are
optimally supported.
[0039] Normally the strands between adjacent bonds are twisted out
of the plane of the original sheet metal, which results in a
lowering of the restriction to fluid flow normal to the sheet of
expanded metal.
[0040] The support plate 20 mechanically supports the tubes over
the full cross-section of the shell 3, i.e. also in the window 42.
Therefore, the unsupported tube length of tube 8 for example,
between support plates 19 and 21 is L.sub.1. For comparison, the
unsupported tube length of e.g. tube 14 between support plates 18
and 20 is 2L.sub.1. The invention may in this way serve to decrease
the unsupported tube length in order to suppress vibrations. If
more or all support plates in the heat exchanger 1 were combined
support plates 35, it would be possible to increase the spacing
between support plates from a mechanical point of view.
[0041] Reference is now made to FIGS. 6-11, and a second embodiment
of the present invention will now be discussed.
[0042] FIG. 6 shows part of a Texas tower heat exchanger 101 in
longitudinal cross-section, and FIGS. 7 and 8 show two
cross-sections along lines VII-VII and VIII-VIII, respectively. The
heat exchanger 101 has a vertical cylindrical shell 103 and a
bundle of tubes 105 running through the central part of the shell
103. The tubes 108,109 and 110 are visible in FIG. 6. The Texas
tower may for example have a height of 24 m and a diameter of 2.5
m.
[0043] The support for the tube bundle 105 comprises the five
support plates 117,118,119,120,121 shown in FIG. 6 as support
elements. The plates are spaced from each other along the length
direction of the tubes 108-110.
[0044] Support plates 117 and 121 are conventional segmental
baffles 124 as shown enlarged in FIG. 9. These segmental baffles
are manufactured from a circular plate 125 from which a segment has
been cut off along line 126 so that windows 127, 128 are formed
when the respective plates are mounted in the heat exchanger 101.
The windows are arranged at opposite sides in the heat exchanger as
shown. Into the remaining plate 125 openings 130 have been cut
according to the size and arrangement of the tubes 105. No openings
are arranged in the part 131 opposite to the window, since the
design of the heat exchanger 101 as shown in FIG. 6 is a so-called
no-tube-in-windows design.
[0045] The spacing L.sub.2 between segmental baffles is chosen such
that an optimized fluid flow is obtained, wherein the flow passes
through the windows 127 and 128 thereby crossing the tube bundle
105. A typical value for L.sub.2 is 1.5 m. If the spacing L.sub.2
is too large for preventing vibrations of the tubes, additional
intermediate support plates are mounted in a conventional Texas
tower, like the plate 133 shown in FIG. 10. Plate 133 is a
segmental support baffle which has two sections cut off at opposite
sides, and is provided with openings 134 for the tubes. Such
additional intermediate support plates would be mounted e.g. at the
same locations as shown for plates 118, 119, 120, and such that the
windows register with the windows 127 and 128.
[0046] In the embodiment according to the invention as shown in
FIGS. 6-8, however, the intermediate support plates 118, 119 and
120 are expanded metal support plates, like the plate 135
schematically shown in FIG. 11.
[0047] The plate 135 is formed by a double segmental expanded metal
sheet 136, which is welded to a support ring 138 and support strips
140 so as to form windows 142 and 143. Support plate 135 may be
manufactured much more cheaply than a conventional intermediate
plate 134 as shown in FIG. 10.
[0048] Reference is now made to FIGS. 12-13, and with reference to
these Figs. a third embodiment of the invention will be
discussed.
[0049] The horizontal heat exchanger 201 with shell 203 through
which the tube bundle 205 runs is an example of such a design. FIG.
12 shows part of a longitudinal cross-section, and it will be
understood that the heat exchanger may be much longer, and that
more support plates than shown may be arranged. The tube bundle 205
includes tubes 208, 209, 210, 211, 212, 213, and 214. The Figure
does not show the end parts of the tubes with the tube sheet.
[0050] The tubes are supported by segmental baffles 218, 219, 220.
As further support against tube vibrations expanded metal support
plates 221,222 are arranged. The segmental baffle support elements
and the expanded metal support elements are alternatingly arranged
at a fixed spacing along the length direction of the tubes 205. The
spacing between adjacent segmental baffles, e.g. 218 and 219, is
L.sub.3.
[0051] The segmental baffle support elements 218, 219, 220 are
similar to those shown and described with reference to FIG. 4.
Halfway in between adjacent segmental baffles, an expanded metal
support plate like the plate 235 shown in FIG. 13 is arranged. The
plate 235 may be cheaply manufactured, for example, by cutting a
sheet of expanded metal to circular shape, e.g. by laser cutting,
and welding to a support ring 245.
[0052] The expanded metal support plates 221,222 serve to prevent
vibrations between segmental baffles. The maximum unsupported tube
length of e.g. tube 214 is L.sub.3, equal to the spacing between
adjacent segmental baffles. Without the expanded metal support
elements the unsupported tube length would be twice the spacing
between adjacent segmental baffles. In this way, the present
invention allows the spacing between adjacent segmental baffles to
be larger than if the tube support were made of segmental baffles
only. The segmental baffles may thus be placed such that optimum
fluid flow in the shell side and heat transfer is achieved, and the
overall cost of the tube support may be minimized.
[0053] However, in some applications it may also happen that tube
vibration considerations pose a limitation on the minimum spacing
between segmental baffles. This may be the case when it is desired
to maximize cross-flow of fluid in the shell, in order to maximize
heat transfer in a given heat exchanger volume. In this case,
segmental baffles of low baffle cut are used, and it is desirable
to minimize the spacing between the baffles. This results in a
large pressure drop, but may also generate tube vibrations despite
the relatively short spacing between segmental baffles. In such a
situation it would previously have been needed to increase the
baffle spacing and possibly increase the size of the heat
exchanger. With the present invention, however, additional expanded
metal support plates can solve the vibration problem. Although the
cost of the tube support in the heat exchanger slightly increases
by the use of the additional expanded metal support elements, the
total cost of the heat exchanger may be lower because a smaller
shell may be used.
[0054] It shall be clear that the present invention can equally be
applied to horizontal and vertical heat exchangers.
[0055] The support plates may be mounted in any suitable way in the
shell. A conventional method for mounting segmental baffles is to
use spacer rods arranged parallel to the tubes, which are welded to
the shell and to the segmental baffles. Such rods may likewise be
welded to the support ring of expanded metal support elements.
[0056] For many applications of the present invention the expanded
metal support elements suitably have interstices with a size just
large enough such that the tubes may be passed through, so that
each tube is supported from four sides substantially without play.
Typically in this case the size would be such that at maximum, a
gauge of 10% larger diameter than the tube could pass through the
interstices. This size of interstices is for example preferred for
the embodiments discussed with reference to FIGS. 1 and 12, wherein
each expanded metal support element preferably supports the tubes
sufficiently.
[0057] It will be clear however that it is also possible to use
expanded metal with interstices so large that several tubes can
pass through. In this case suitably several sheets of expanded
metal are arranged to co-operate so that the tubes are supported
from all sides, for example the intermediate expanded metals
support elements of the embodiment discussed with reference to FIG.
6. Suitable such arrangements of several expanded metal sheets are
discussed in WO 03/067170. Other suitable arrangements, types of
expanded metal and arrangement and shapes of interstices of
expanded metal are described in European Patent application No.
03077463.2, unpublished at the first filing (priority) date of the
present invention.
* * * * *