U.S. patent application number 12/661463 was filed with the patent office on 2011-09-22 for slotted impingement plates for heat exchangers.
This patent application is currently assigned to Saudi Arabian Oil Company. Invention is credited to Salamah S. Al-Anizi, Luai M. Al-Hadhrami, Dhawi A. AL-Otaibi, Abdullah M. Al-Qahtani.
Application Number | 20110226455 12/661463 |
Document ID | / |
Family ID | 44646287 |
Filed Date | 2011-09-22 |
United States Patent
Application |
20110226455 |
Kind Code |
A1 |
Al-Anizi; Salamah S. ; et
al. |
September 22, 2011 |
Slotted impingement plates for heat exchangers
Abstract
Impingement plates for shell and tube heat exchangers are
positioned between the inlet openings and the tubes with the
surfaces of the impingement plates being normal to the flow path of
the liquid entering the shell from the inlet openings and having a
plurality of openings through which a portion of the liquid passes
before contacting the tubes. The openings can be formed as
elongated parallel slots that are positioned parallel to the tubes
and function to enhance the fluid flow, especially in the area that
is immediately downstream from the impingement plates, thereby
reducing fluid stagnation, fouling and tube erosion and prolonging
the useful life and time in service between maintenance shut
downs.
Inventors: |
Al-Anizi; Salamah S.;
(Dhahran, SA) ; AL-Otaibi; Dhawi A.; (Jalawaih,
SA) ; Al-Qahtani; Abdullah M.; (Dammam, SA) ;
Al-Hadhrami; Luai M.; (Dhahran, SA) |
Assignee: |
Saudi Arabian Oil Company
|
Family ID: |
44646287 |
Appl. No.: |
12/661463 |
Filed: |
March 16, 2010 |
Current U.S.
Class: |
165/177 |
Current CPC
Class: |
F28F 9/0278 20130101;
F28D 7/16 20130101; F28F 9/0265 20130101 |
Class at
Publication: |
165/177 |
International
Class: |
F28F 1/00 20060101
F28F001/00 |
Claims
1. A shell and tube heat exchange apparatus for the transfer of
heat from a first liquid to a second liquid comprising: a shell
defining an interior space, a plurality of spaced-apart tubes
extending longitudinally in the shell, wherein the first liquid
flows through the plurality of tubes, an inlet opening for
admitting the second liquid into the interior space in an inlet
flow direction that is generally transverse to the tubes, and an
impingement plate positioned between the inlet opening and the
tubes, the surface of the plate being normal to the flow path of
the second liquid entering the shell from the inlet opening and
having a plurality of openings through which a portion of the
second liquid passes before contacting the tubes.
2. The apparatus of claim 1, wherein the plurality of openings in
the impingement plate are elongated slots.
3. The apparatus of claim 2, wherein the slots extend along
substantially the entire length of the plate.
4. The apparatus of claim 2, wherein the slots are parallel to each
other.
5. The apparatus of claim 2, wherein the impingement plate is
positioned so that the slots are parallel to the tubes.
6. The apparatus of claim 5, wherein a portion of the slots are
aligned with the spaces between the tubes.
7. The apparatus of claim 2, wherein the width of each slot is
about 6 mm and the space between the slots is about 25 mm.
8. The apparatus of claim 2, wherein the length of each slot is
about 136 mm.
9. The apparatus of claim 1, wherein the impingement plate is
rectilinear and generally planar.
10. The apparatus of claim 2, wherein the slot openings constitute
about 80% of the surface area of the impingement plate.
11. The apparatus of claim 2, wherein the area of the impingement
plate is about 110% of the area of the inlet opening.
12. The apparatus of claim 1, wherein the shell and tube heat
exchanger is a double split flow H-type further comprising: a
second inlet for admitting a portion of the second liquid into the
interior space in an inlet flow direction that is generally
transverse to the tubes; and a second impingement plate positioned
between the second inlet and the tubes, the surface of the plate
being normal to the flow path of liquid entering the shell from the
second inlet, the second impingement plate having a plurality of
openings through which a portion of the second liquid passes before
contacting the tubes.
13. A generally planar diffusing impingement plate configured and
dimensioned for interpositioning between a liquid inlet opening in
the exterior wall of a shell and tube heat exchanger and the tubes
of the heat exchanger, the surface of the plate being generally
planar and having a plurality of elongated spaced-apart slotted
openings for diffusing and passing a portion of liquid contacting
the surface of the plate.
14. The plate of claim 13, wherein the plurality of openings in the
impingement plate are elongated slots that extend from proximate
opposing ends of the plate.
15. A method of mitigating fouling on and corrosion of a portion of
the tubes in a shell and tube heat exchanger that are in the flow
path of a heat transfer liquid entering the heat exchanger through
an inlet opening, the method including: providing a generally
planar diffusing impingement plate having a plurality of elongated
spaced-apart openings, and positioning the plate proximate the
liquid inlet opening to thereby diffuse and pass only a portion of
the flowing liquid into direct contact with the tubes adjacent the
plate.
16. The method of claim 15, wherein the plurality of openings in
the impingement plate are elongated slots and the slots are aligned
parallel to the tubes.
Description
FIELD OF THE INVENTION
[0001] The invention relates to impingement plates for shell and
tube heat exchangers.
BACKGROUND OF THE INVENTION
[0002] Fluid heat exchangers are widely used in the industry. One
common heat exchanger is known as a shell and tube heat exchanger
and includes a cylindrical housing or shell encompassing a bundle
of tubes. In this type of heat exchanger, heat from a first fluid
flowing through the tubes is transferred to a second fluid flowing
through the housing, as a result of the second fluid flowing in
contact with the outer surfaces of said tubes. The second fluid
enters the shell through a nozzle and is directed initially to an
impingement plate which deflects and redirects the second fluid to
flow toward and about the outer surfaces of said tubes, as
generally disclosed in U.S. Pat. No. 3,938,588.
[0003] The inlet fluid initially has a high velocity and dynamic
force when it impacts on the impingement plate. In many
conventional shell and tube type heat exchangers the impingement
plate adjacent the inlet nozzle protects the tubes from direct
impact of the high velocity inlet fluid, but often creates
operational problems when fluid flowing downstream of the
impingement plate has reduced velocity due to the vortex effect of
fluid motion at the sides of the impingement plate. This results in
fouling accumulation on surfaces of the tubes, particularly in the
region designated herein as "fouling area" immediately downstream
from the conventional impingement plate. Such fouling retards heat
transfer to tubes in that area and furthermore may create a
corrosive environment on the outer surfaces of said tubes. If the
fouling and corrosion becomes severe enough, eventually the heat
exchanger must be completely shut down and retubed.
[0004] FIGS. 1-2 illustrate a prior art cylindrical double split
flow H-type heat exchanger 10, as classified by Tubular Exchanger
Manufacturers Association (TEMA), being formed of a cylindrical
shell housing or shell 20 encompassing a bundle of tubes. This type
of heat exchanger is often used for vaporizing duties where low
pressure drop is required. In the prior art shell and tube heat
exchanger shown in FIGS. 1-2 it is typical for tubes to transport a
first fluid of relatively elevated temperature, the heat from this
fluid in the tubes being transferred to a second fluid flowing from
inlets 21A, 21B to outlets 22A, 22B. For convenience herein, the
fluid within the tubes will be designated "tube-side fluid" and the
fluid flowing from inlets 21A, 21B to outlets 22A, 22B and flowing
across and in contact with the outer surfaces of the tubes will be
designated "shell-side fluid".
[0005] As shown in FIG. 2, housing 20 has two shell side fluid
inlets 21A, 21B and two shell side fluid outlets 22A, 22B. The
inner tubes are in communication with a tube side inlet 27 and a
tube side outlet 28. The illustrated heat exchanger includes
conventional impingement plates 40A, 40B situated inward and
adjacent of the inlet nozzles and between said inlet nozzles and a
bundle of tubes.
[0006] As shown in FIG. 2, fluid entering the shell 20 from inlets
21A, 21B initially strikes impingement plates 40A, 40B, and then
follows primarily the path indicated by long arrows A, flowing
between, around and engaging the outer surfaces of tubes in the
tube bundle (not shown). Two horizontal divider baffles 41A, 41B
and three vertical circular support baffles 30A, 30B, 30C are also
positioned in the heat exchanger and further impinge the flow of
the fluid.
[0007] Arrows A indicate how the fluid from inlets 21A, 21B tends
to not flow in the fouling areas 22 shown in the dashed line
generally semi-circular areas in the region of the housing that is
directly downstream from impingement plates 40A, 40B. As discussed
above, it is in this region where deposits and fouling accumulate
on the surfaces of tubes (not shown). This accumulation inhibits
heat exchange with the fluid flowing within tubes by reducing the
ability of the in-flowing fluid to freely circulate around these
tubes and thus reduces the efficiency of the heat transfer. Also,
this fouling may cause corrosion on the surfaces of these
tubes.
[0008] The above-mentioned areas of fouling and accumulation
designated with reference number 22 and shown in FIG. 2, are not
precise areas, but are the regions where the above-mentioned
fouling occurs. In addition, fouling can also occur downstream of
the divider baffles 41A, 41B.
SUMMARY OF THE INVENTION
[0009] The improved impingement plate of the present invention for
use in a shell and tube heat exchanger are positioned between the
inlet openings and the tubes, the surfaces of the plates being
normal to the flow path of the liquid entering the shell from the
inlet openings and are provided with a plurality of openings
through which a portion of the liquid passes before contacting the
tubes. In one aspect of the invention, the openings are formed as
elongated parallel slots and the impingement plate is positioned so
that the slots are parallel to the tubes. The openings enhance the
fluid flow, especially in the area that is immediately downstream
from the impingement plates. This improved fluid flow prevents
fluid stagnation by allowing a portion of the pressurized liquid to
pass through the plate, the majority being diverted around the
periphery of the plate to prevent tube erosion, and therefore
avoids unnecessary shut downs of the heat exchanger for
service.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] For convenience and clarity in describing these embodiments,
similar elements or components appearing in different figures will
have the same reference numbers.
[0011] FIG. 1 is a perspective view of a prior art double split
flow H-type heat exchanger.
[0012] FIG. 2 is a cross section view of the prior art heat
exchanger taken along line 2-2 of FIG. 1.
[0013] FIG. 3 is a perspective view of an impingement plate
according to one embodiment of the invention, showing a plurality
of slots in the surface of the impingement plate.
[0014] FIG. 4 is a perspective view of the inside of the heat
exchanger, showing the new impingement plate.
DETAILED DESCRIPTION OF THE INVENTION
[0015] A preferred embodiment of the impingement plate of the
invention is illustrated in FIGS. 3-4. For simplicity and clarity,
the heat exchanger 10 in FIG. 4 will be shown as having the same
housing or shell 20 as in FIGS. 1-2 and also having the same inlets
21A, 21B, outlets 22A, 22B and bundle of tubes 25. As mentioned
above, in the present embodiments it is understood that flowing in
these tubes 25 is a relatively hot fluid, with heat transfer from
the outer surfaces of these tubes 25 to the relatively cooler
second fluid flowing from inlets 21A, 21B through the shell housing
to outlets 22A, 22B.
[0016] FIGS. 3-4 illustrate in the heat exchanger housing 20, the
impingement plate 40 which is generally planar. Although the
impingement plate 40 is shown as being rectilinear, other shapes
can be used. The impingement plate 40 includes a plurality of
openings 45A, 45B through which a portion of the shell-side fluid
passes before contacting the tubes. The openings are preferably in
the form of elongated slots which are parallel to each other, but
other shapes and orientations can also be used. The openings extend
along substantially the entire length of the plate. In one
embodiment, the openings constitute about 70-90% of the surface
area of the impingement plate, and preferably about 80%. In the
embodiment shown, the openings form two columns separated by a
portion of the impingement plate that forms a central support
member 47 which can be provided for enhanced structural
integrity.
[0017] The width of each opening can be in the range of about 3 mm
to about 10 mm. The length of each opening can be in the range of
about 125 mm to about 150 mm, depending on the size of the
impingement plate. The space between the openings can be in the
range of about 20 mm to about 50 mm. In a preferred embodiment, the
width of each opening is about 6 mm, the length of each opening is
about 136 mm, and the space between the openings is about 25 mm.
However, the exact dimensions of the impingement plates and the
openings, and the spacing between the openings in the plates can be
varied, depending on the nature of the fluid, the velocity of the
fluid, the intended heat transfer, etc.
[0018] FIG. 4 illustrates the placement of the impingement plate 40
in the shell 20 which is between the inlet 21B and the tubes 25.
The tubes 25 are spaced-apart from each other and extend
longitudinally in the shell 20 in a first direction, wherein a
first liquid flows through the plurality of tubes. An inlet opening
21B admits a second liquid into the shell 20 in an inlet flow
direction that is generally transverse to the tubes 25. The
impingement plate 40 is positioned so that its surface is normal to
the flow path of the second liquid entering the shell from the
inlet opening 21B. A portion of the second liquid passes through
the openings in the impingement plate 40 before contacting the
tubes 25.
[0019] In a preferred embodiment, the impingement plate 40 is
positioned so that the slots 45A, 45B are parallel to the tubes 25.
Further, it is preferred that a portion of the slots 45A, 45B are
aligned with the spaces between the tubes 25. This orientation
helps to prevent fluid stagnation by allowing fluid to flow through
the openings and between the tubes 25. This orientation also helps
to prevent tube erosion by allowing impingement of the fluid by the
surface of the impingement plate formed between the openings.
[0020] In one embodiment the area of the impingement plate 40 is
about 10% to about 20% larger than the area of the inlet opening.
For example, if the inlet opening is 10 inches in diameter, then
the impingement plate can be about 11 inches by 11 inches.
[0021] The openings in the impingement plate allow the fluid to
more effectively flow in area 22 (see FIG. 2) which greatly reduces
or even prevents accumulation of deposits on the tubular surfaces
in this area, and thus allows these tubular surfaces to maintain
their most efficient heat transfer capability. Also, the
elimination of these deposits reduces or prevents corrosion on
these surfaces. Furthermore, the more efficient heat transfer from
these surfaces increases protection of these tubes from overheating
due to lack of heat transfer from them. And finally, as a
consequence of this new structure and fluid-flow arrangement, there
is an overall improved and more efficient heat transfer of the
entire heat exchanger system.
[0022] The improvement by the new impingement plate overcomes or
greatly reduces fouling accumulation on the tubes downstream of the
impingement plates caused by very low velocity or absence of flow
of the fluid in this area below the impingement plate assembly.
With the new device, not only is there established an adequate
fluid flow onto and around the surface areas of the tubes directly
downstream from the impingement plate but a flow of adequate
velocity to achieve cleaning and scrubbing and also to achieve
recovery of heat from those surfaces.
[0023] The new impingement plate can be made of material similar or
the same as that in prior art impingement plates such as stainless
steel or other material resistant to corrosion and damage from the
environment within the heat exchanger.
[0024] The divider baffles 41A, 41B in the shell can also include
openings as described herein to prevent fouling in the areas that
are immediately downstream of these divider baffles (see FIG.
2).
[0025] Although the present invention has been described in
accordance with an I-I-type heat exchanger, persons of ordinary
skill in the art will recognize that the present invention can be
implemented in any type of heat exchanger having impingement
plates.
[0026] As will be understood from the above description and the
attached drawings, the present invention provides a new and
functionally different impingement plate to reduce fouling
accumulation, to enhance heat transfer and to reduce corrosion of
tubes in a shell and tube heat exchanger.
[0027] While the invention has been described in conjunction with
several embodiments, it is to be understood that many alternatives,
modifications, and variations will be apparent to those skilled in
the art in light of the foregoing description. Accordingly, this
invention is intended to embrace all such alternatives,
modifications, and variations which fall within the spirit and
scope of the appended claims.
* * * * *