U.S. patent application number 13/644037 was filed with the patent office on 2014-04-03 for heat exchanger.
The applicant listed for this patent is Delio SAMZ. Invention is credited to Delio SAMZ.
Application Number | 20140090804 13/644037 |
Document ID | / |
Family ID | 50384116 |
Filed Date | 2014-04-03 |
United States Patent
Application |
20140090804 |
Kind Code |
A1 |
SAMZ; Delio |
April 3, 2014 |
Heat Exchanger
Abstract
A device for exchanging heat between the two fluid streams is
disclosed. The device includes parallel heat exchange tubes
arranged in an annular pattern, the first and second ends of the
tubes being coupled to first and second halves of a core housing
configured to channel the first gas stream through the heat
exchange tubes between a first intake formed on the first half of
the core housing and a first exhaust formed on the second half of
the core housing. The device further includes a shell enclosing the
core housing and separated from the core housing by a space, the
shell configured to channel the second gas from a second intake,
then between the heat exchange tubes, and then through a second
exhaust. The heat exchanger device includes an expansion joint
coupling the core housing and the shell housing such that the core
housing floats within the shell.
Inventors: |
SAMZ; Delio; (Aurora,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SAMZ; Delio |
Aurora |
|
CA |
|
|
Family ID: |
50384116 |
Appl. No.: |
13/644037 |
Filed: |
October 3, 2012 |
Current U.S.
Class: |
165/81 |
Current CPC
Class: |
F28F 27/02 20130101;
F28D 7/1669 20130101; F28F 2250/06 20130101; F28F 9/0239 20130101;
F28F 9/0132 20130101; F28F 9/0229 20130101; F28F 1/022 20130101;
F28F 9/22 20130101 |
Class at
Publication: |
165/81 |
International
Class: |
F28F 1/02 20060101
F28F001/02 |
Claims
1. A heat exchanger for exchanging heat between a first stream of
fluid and a second stream of fluid, the two fluid streams being at
different temperatures, the heat exchanger comprising: a plurality
of parallel heat exchange tubes coupled to a core housing, the core
housing configured to channel the first stream through the heat
exchange tubes; a shell enclosing the core housing and isolated
from the core housing by a space, the shell configured to channel
the second stream between the heat exchange tubes; an expansion
joint coupling the core housing to the shell housing, the expansion
joint configured such that the expansion joint allows the core
housing to float within the shell.
2. The heat exchanger of claim 1 wherein the heat exchange tubes
have opposite first and second ends, the first and second ends
being coupled with a first and second halves of the core housing,
the first and second halves of the core housing configured to
channel the first stream through the heat exchange tubes between a
first intake formed on the first half of the core housing and a
first exhaust formed on the second half of the core housing; the
shell configured to channel the second stream from a second intake,
then between the heat exchange tubes, and then through a second
exhaust.
3. A heat exchanger of claim 1 wherein the expansion joint
comprises a flanged and flued expansion joint having a middle
flange positioned between near side and far side flange portions,
one of said near side and far side flange portions being mounted to
the shell housing with the middle flange being mounted to the core
housing.
4. A heat exchanger of claim 3 wherein the far side and near side
flange portions each have a thickness selected to permit the near
side and far side flange portions to resiliently flex sufficiently
to compensate for expansion and contraction of the shell housing
relative to an adjacent component, the middle flange having a
thickness selected to permit it to flex sufficiently to compensate
for the relative motion between the core housing and the shell
housing.
5. A heat exchanger of claim 4 wherein the thickness of the middle
flange is less than the thicknesses of the near side and far side
flange portions.
6. A heat exchanger of claim 3 wherein the far side and near side
flange portions have a thickness selected to permit the heat
exchanger to operate at a desired pressure rating, the thickness of
the third flange being selected by referencing a difference in
pressure between the first and second fluid streams.
7. A heat exchanger as defined in claim 2 further comprising an
internal shunt for diverting a portion of the first stream such
that said portion of the first stream does not pass through the
heat exchange tubes and instead flows directly towards the first
exhaust, the internal shunt comprising a central passage extending
through a center of the core housing, the central passage having a
first port communicating with the first intake and a second port
communicating with the second exhaust and a valve for controlling
the flow through the internal shunt.
8. A heat exchanger as defined in claim 7 wherein the internal
shunt further comprises a conical diffuser formed on the second
port adjacent the first exhaust, the conical diffuser separating
the diverted first stream to a portion of the first stream which
was not diverted, the conical baffle having a plurality of
apertures through which the diverted first stream can mix with the
portion of the first stream which was not diverted.
9. The heat exchanger as defined in claim 8 further comprising a
second expansion joint mounting the central passage at one of the
first and second ports to the core housing such that an end of the
central passage floats within the core housing.
10. The heat exchanger as defined in claim 1 further comprising at
least one baffle surrounding the heat exchange tubes and extending
between the heat exchange tubes and the shell, the baffle
comprising a flat annular sheet having openings through which the
heat exchange tubes extend perpendicularly there through, the
baffle having peripheral edges with a plurality of notches formed
there along, the flange being supported by a plurality of tie bars
extending perpendicular to the flange, each of the tie bars having
a plurality of notches formed thereon, the notches of the tie bars
mating with the notches on the baffle.
11. The heat exchanger as defined in claim 2 wherein the first end
of the heat exchange tubes are mounted to a header formed on the
first half of the core housing, at least one heat shield baffle
being mounted parallel to the header and held at a distance from
the header by a plurality of support members, the heat shield
baffle comprising a flat sheet of metal having a plurality of
apertures formed thereon dimensioned and configured to permit the
heat exchange tubes to pass through the flat sheet of metal and
mate thereto.
12. The heat exchanger as defined in claim 11 further comprising an
extension tube formed on an end of each heat exchange tube and
extending between the header and the heat baffle, the extension
tube being made of an insulative material.
13. The heat exchanger as defined in claim 1 wherein the core
housing and shell housing are configured such that the second
stream is directed to impinge on the heat exchange tubes in a
parallel fashion where the second stream first contacts the heat
exchange tubes.
14. The heat exchanger as defined in claim 2 wherein the shell
housing immediately adjacent one of the exhausts and intakes is
recessed sufficiently to reach the core housing and form a void
surrounding said exhaust or intake such that said exhaust or intake
does not contact the shell housing.
15. The heat exchanger as defined in claim 7 wherein the valve
comprises a movable baffle contained within the central passage
coupled to an elongated valve stem passing through the core housing
and the shell housing, the shell housing immediately adjacent the
valve stem being recessed sufficiently to reach the core housing
and form a void surrounding the valve stem such that the valve stem
does not contact the shell housing.
16. A heat exchanger for exchanging heat between a first stream of
fluid and a second stream of fluid, the two fluid streams being at
different temperatures, the heat exchanger comprising: a plurality
of parallel heat exchange tubes coupled to a core housing, the core
housing configured to channel the first stream through the heat
exchange tubes; a shell enclosing the core housing and isolated
from the core housing by a space, the shell configured to channel
the second stream between the heat exchange tubes; an expansion
joint coupling the core housing to the shell housing, the expansion
joint configured such that the expansion joint compensates for the
thermal expansion and contraction of the shell housing relative to
an adjacent component, the expansion joint being further configured
to compensate for the expansion and contraction of the core housing
relative to the shell housing.
17. A heat exchanger of claim 16 wherein the expansion joint
comprises a flanged and flued expansion joint having a third flange
positioned between near side and far side flange portions, one of
said near side and far side flange portions being mounted to the
shell housing with the flexible flange being mounted to the core
housing.
18. A heat exchanger for exchanging heat between first and second
fluid streams, the heat exchanger comprising: a core housing
mounted within a shell housing by a thermal expansion joint, the
core and shell housings being configured to keep the first and
second fluid streams separate but in thermal contact; the shell
housing being isolated from the core housing by a space dimensioned
to permit the core housing to move relative to the shell housing as
a result of thermal expansion; the thermal expansion joint
configured to compensate for the relative motion of the shell and
core housings, and the expansion joint being further configured to
compensate for the thermal expansion of the shell housing relative
to an adjacent component.
19. A heat exchanger of claim 2 wherein a portion of the core
housing is positioned inwardly towards a longitudinal axis of the
heat exchanger to accommodate two parallel conduits carrying the
first and second fluid streams.
Description
FIELD OF THE INVENTION
[0001] The invention relates generally to a heat exchanger for
exchanging heat between a cooler fluid and a hotter fluid, and in
particular for exchanging heat between two separate streams of
gas.
BACKGROUND OF THE INVENTION
[0002] Heat exchangers are often used in industrial applications to
transfer heat from one gas or liquid to another. One type of heat
exchanger uses a plurality of tubes to carry one of the fluids. The
tubes are usually arranged in a circular fashion around a central
opening, as seen in U.S. Pat. No. 5,355,945 to Sanz et al. The
parallel tubes are generally mounted to headers at their ends and
can be held in a substantially vertical orientation. The other gas
is then passed over and between the tubes in a current or counter
current arrangement to effect the transfer of heat from the hotter
gas (or fluid) to the cooler gas (or fluid). One stream of gas (or
fluid) enters the heat exchanger through an intake port which then
passes the gas through the heat exchange tubes and then out of an
exhaust. The other stream of gas (or fluid) enters the heat
exchanger through another intake port, then passes over and between
the heat exchange tubes and then out another exhaust port. Heat is
exchanged between the two fluids through the walls of the heat
exchange tubes as the two currents pass each other in opposite
directions.
[0003] While this sort of heat exchanger is heat transfer wise
effective, it suffers from a series of drawbacks, such as
complexity of design, difficulty in assembling, bulkiness and the
need to periodically repair leaks in the heat exchange mechanism,
particularly where the heat exchange tubes are secured to their
headers. One factor necessitating the large bulk associated with
heat exchangers is the cyclical heating and cooling of portions of
the heat exchanger. During the operation of the heat exchanger,
heat from the fluids passing through the heat exchanger tends to
cause the heat exchange tubes and the housings enclosing the heat
exchange tubes to expand. When the heat exchanger cools down when
the flow of hot fluid is stopped, the tubes and housings contract.
This constant expanding and contracting generally requires the
housings to be built large enough to absorb the expansions and
contractions without causing faults in the system. As a result,
heat exchangers tend to be large and bulky.
[0004] In order to control the temperature exciting the heat
exchanger, external piping is generally provided so that a portion
of one of the gas (fluid) streams can be shunted directly towards
the exhaust port without going through or between the heat exchange
tubes. The piping required for the shunting adds to the overall
size and bulk of the heat exchanger.
[0005] One factor contributing to the complexity and cost of
building shell and tube heat exchangers is the necessity of
mounting a series of baffles around the heat exchange tubes. These
baffles generally take the form of annular metal members which
surround the bundle of heat exchange tubes and extend between the
tubes and the outer housing. Mounting these baffles often involves
many steps, which in turn increases the overall cost of the heat
exchanger.
[0006] One factor contributing to the maintenance requirements of
the heat exchanger is the failure of the joints holding the ends of
the heat exchange tube to their respective headers. As a result of
the joints being repeatedly heated and cooled by exposure to the
hotter and cooler gases and in conjunction with the thermal
stresses in the heat exchanger, the welded or rolled in joints are
prone to failure from cracking This in turn requires periodic
inspection and occasional repair. Another factor contributing to
the maintenance requirements and limiting the service life of these
heat exchangers is the failure of tubes at a result of fluid
impingement causing erosion and tube vibration failures at the
proximity of the shell ports of the vessels.
[0007] All of the above limitations add to the expense and
inconvenience of utilizing these types of heat exchanges. An
improved heat exchanger design which overcomes these limitations is
therefore required.
SUMMARY OF THE INVENTION
[0008] In accordance with one aspect of the present invention,
there is provided a heat exchanger for exchanging heat between a
first stream of gas and a second stream of gas, the two gas streams
being at different temperatures. The heat exchanger includes a
plurality of parallel heat exchange tubes arranged in an annular
pattern, the heat exchange tubes having opposite first and second
ends, the first and second ends being coupled with a first and
second halves of a core housing, the first and second halves of the
core housing is configured to channel the first gas stream through
the heat exchange tubes between a first intake formed on the first
half of the core housing and a first exhaust formed on the second
half of the core housing. The heat exchanger further includes a
shell enclosing but isolated from the core housing by a space. The
shell is configured to channel the second gas from a second intake,
then between the heat exchange tubes, and then through a second
exhaust. The heat exchanger further includes a three part flanged
flued expansion joint.
[0009] With the foregoing in view, and other advantages as will
become apparent to those skilled in the art to which this invention
relates as this specification proceeds, the invention is herein
described by reference to the accompanying drawings forming a part
hereof, which includes a description of the preferred typical
embodiment of the principles of the present invention.
DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a schematic sectional view of a heat exchanger
made in accordance with the present invention showing the heating
exchange tubes mounted between the upper and lower pair of headers
and within the housing shell of the heat exchanger.
[0011] FIG. 2 is a sectional view of a heat exchanger made in
accordance with the present invention and showing the inner shunt
mechanism.
[0012] FIG. 3 is a cross sectional view taken along line C-C of
FIG. 2 showing the orientation of the heat exchange tubes in
relation to the outer housing shell and the inner core housing and
showing also the shell guide plates mounted around the upper tube
plate.
[0013] FIG. 4 is a view of the tie bar portion of the present
invention.
[0014] FIG. 5 is a top view of a portion of a baffle used in the
construction of the heat exchanger shown in FIG. 2.
[0015] FIG. 6 is a cross sectional view of a anti acid condensation
shield portion of a heat exchanger made in accordance with one
aspect of the present invention.
[0016] FIG. 7 is a side view of a portion of the heat exchanger
showing part of the valve mechanism for the shunt.
[0017] In the drawings like characters of reference indicate
corresponding parts in the different figures.
DETAILED DESCRIPTION OF THE INVENTION
[0018] Referring to FIG. 1 a heat exchanger made in accordance with
the present invention, shown generally as item 10, includes an
outer shell housing 12, an inner core housing 14 contained within
shell housing 12 and a plurality of heat exchange tubes 16 arranged
in an annular fashion around a central space 18 and axis 1. Core
housing 14 is divided into first portion (or half) 20 and second
portion (or half) 22. Headers (also called tubesheet) 24 and 26 are
formed on the first and second core housing portions 20 and 22,
respectively. The tubesheets are configured to form a header
causing a first stream of fluid, shown by arrows A, to pass from an
intake 27 formed on one portion of the core housing to exhaust 29
formed on the other portion of the core housing by passing through
heat exchange tubes 16. Shell housing 12 is isolated from core
housing 14 and is further configured to cause a second stream of
fluid, indicated by arrows B, to flow from an intake 28 on shell 12
to an exhaust 30. Baffle 25 is an annular flange which ensures that
the second stream of fluid passes between and the full length of
heat exchange tubes 16 on its way from intake 28 to exhaust 30. The
direction of flow of the first and second streams can be reversed
if required. Of course, the two fluids enter heat exchanger 10 at
different temperatures, with the hotter fluid passing a majority of
its heat to the second fluid while passing through the heat
exchanger.
[0019] Heat exchanger 10 is provided with a flange & flued
bellows expansion joint assembly shown generally as item 32. Flange
34 joins to shell 12, flange 38 joins to an adjacent component (not
shown) connected to shell exhaust 29. Flange 36, located between
flanges 34 and 38, joins to core housing 14. Item 32 is the joint
assembly internal liner. The thickness of flanges 34 and 38 are
configured for the expansion/contraction to be compensated for
derives from the local Pressure code requirement while the
thickness of flange 36 derives from the pressure differential
between streams A and B. It will be appreciated that because the
pressure differential is smaller than the design pressure (i.e.
desired pressure rating) of the exchanger that it is possible there
from to obtain a greater flexibility for flange 36 by making this
flange thinner than flanges 34 and 38.
[0020] The above described expansion joint permits the heat
exchanger's outer diameter be made smaller and less bulky because
there is no need for a greater diameter shell to absorb thermal
expansions/contractions. Instead, the flexibility of flange 36 of
the joint absorbs the expansion/contraction of the core housing.
Essentially, the second half portion core 22 via flange 36 floats
within the isolated shell.
[0021] Referring now to FIG. 2, heat exchanger 10 includes an
internal passage 50 for by-pas purpose of fluid stream A. Flange 38
of expansion joint 32 is exhaust port 29. Passage 50 consists of an
elongated tube 52 which is dimensioned to fit coaxially through
central opening 54 formed within the heat exchanger. Central
opening 54 is surrounded by heat exchange tubes 16 and is
positioned along axis 51 of the heat exchanger. Space 53 separates
heat exchange tubes 16 from shell housing 12 and permits fluid
stream B to flow between heat exchange tubes 16 as the fluid stream
passes from external space 53 to central passage 54. Baffle 25
ensures that the fluid is then directed to flow between the heat
exchange tubes to space 64. Baffles 21 have a tube support function
only. The top and bottom ends of central opening 54 is blocked by
walls 43 and 45, respectively, to ensure that stream B does not mix
with stream A. Elongated tube 52 is provided with an expansion
joint 56 to ensure that changes in the length of tube 52 caused by
the cooling or heating of the tube can be compensated for.
[0022] Tube 52 has a conical diffuser 58 formed on the end of tube
52 adjacent exhaust port 29. Conical diffuser 58 is cone shaped and
has a plurality of apertures 60 formed thereon to permit the fluid
passing through tube 52 to mix with the rest of fluid stream A
flowing within the interior of first core housing 20 before the
fluids exit exhaust port 29. Valve 80 is positioned at the entry of
tube 52, adjacent intake port 27 to control the amount of stream A
which by-passes through tube 52 as opposed to through heat exchange
tubes 16 in order to maintain the specified temperature. In the
event the temperature of the fluid exiting outlet port 29 is below
its normal temperature valve 80 closes fully and the entirety of
stream A passes between heat exchange tubes 16. Inversely, if the
temperature of the fluid exiting outlet port 29 is above its normal
temperature valve 80 opens partially and only part of stream A
passes between heat exchange tubes 16. It will be appreciated that
the portion of the stream passing through tube 52 will be at a
different temperature than the portion of the stream passing
through tubes 16, so conical diffuser 58 helps to mix the two
portions of stream A in the interior of core housing portion 20
before the stream exits exhaust 29. This ensures that no "hot
spots" are formed at exhaust 29.
[0023] Fluid stream B enters the heat exchanger, through intake
port 28, decreases its velocity within space 62 and is distributed
all around conical shape 14 at the circumference of annular space
63 separating shell 12 from core housing portion 20. Then, upon
flowing through space 63 stream B enters and fills space 53
parallel and not transversely to tubes 16 before impinging
transversely on and between the tubes. As a result of first flowing
parallel to the tubes there is even less likelihood to cause the
tubes to vibrate. In contrast, if stream B at the greater velocity
of port 28 impinged on the tubes transversely, as it is generally
done, the stream would induce vibrations in the tubes, causing
additional strain at the tube joints and tube wall thinning damage
at baffle 25 and as a result shorten the service life of the
exchanger.
[0024] Fluid stream B passes from space 53 towards exhaust 30 by
flowing through internal passage 54, around baffle 25 to space 64
to reach passage 65. Since port 30 is in this case positioned below
tube plate 26, stream B is forced by annular passage 65 to again
flow towards space 66 parallel to tubes 16. It will be appreciated
that should a particular application of heat exchanger 10 require
the direction of steams A and B to be reversed, then, passage 65
would also act to reduce vibration in the tubes by compelling the
fluid stream to impinge on the tubes in a parallel orientation
adjacent tube plate 26.
[0025] A portion of the core housing is positioned inwardly towards
a longitudinal axis of the heat exchanger by means of wall 99. This
extends the space separating housing 12 and core housing 14 at a
position "below" tube plate 26 so as to accommodate two parallel
conduits for carrying the first and second fluid stream, in this
case exhaust port 30 and intake port 27.
[0026] Referring now to FIG. 3, a cross-sectional view shows the
relationship between heat exchange tubes 16, central passage 54,
baffle 25, space 53 and ports 27, 28 29 and 30. Space 53 is
obstructed by baffle 25 in order to cause stream B to flow between
the top and bottom halves of heat exchange tubes 16 as discussed
above.
[0027] Referring now to FIGS. 4 and 5, flanges 25 and 21 are
supported within the housing by a plurality of tie bars 67 which
run up the length of the heat exchanger. Flanges 25 and 21 have a
peripheral edge 69 with a plurality of notches 70 formed therein.
Tie bars 67 are elongated members, usually made of steel, which
have notches 68 formed along the length of the tie bar. To attach
the tie bars 67 to the flange edge 69 the tie bar is positioned
such that one of the notches 68 mates with a corresponding notch
70, the tie bar is then tack welded to the baffle. It will be
appreciated that the heat exchanger may have several flanges 25 and
21 positioned one above the other, in which case a corresponding
plurality of notches 68 are formed along the length of the tie bar.
The above tie bars are located between tubes and have the advantage
of not taking the place of heat transfer tubes--as is generally
done.
[0028] Referring now to FIG. 6, condensation can occur when a hot
SO3 gas is cooled by a cold SO2 gas. The bulk gas temperature may
be above the acid dew point but the temperature of the tube wall
can be below the acid dew point because the incoming cold stream
temperature is below the acid dew point. As a preventive measure
FIG. 6 shows one insulating space formed by a heat shield 71,
however two or more insulative spaces could also be used.
[0029] Heat shield 71 consists of a flat sheet of metal which is
provided with a plurality of apertures dimensioned to accept heat
exchange tubes 16. Tube extensions 72 preferably, (temperature
permitting) consists of a non-metallic or insulative material (such
as Teflon) which is mounted around heat exchange tube 16. In this
example, heat shield 71 is mounted to tube plate 26 by bolts 73 to
have an insulating space 74 between cold stream A and hot tube
plate 26. The intent is to prevent as much as possible, the cooling
down by stream A of the tube wall temperature of the inlets of
tubes 16 within tube plate 26 and thereby prevent acid
condensation.
[0030] Referring back to FIG. 2, a recess 31 is formed within shell
12 to obtain an internal passage for port 27. Inwardly extended
port 27 fills partially recess 31 and is attached thermal expansion
free to internal wall 99 separating stream A from steam B. Thus,
recess 31 has eliminated the need for a traditional expansion joint
within the inwardly extension of port 27.
[0031] Referring now to FIG. 7, valve 80 attached to by-pass tube
52; this valve being located within A stream does not require a
seal at the valve as is generally done, instead, the valve stem 81
passes through a void 82 provided within space 65. Void 82 is
partially filled by tube 100 around valve stem 81. Further, the
valve stem and seal block the space within tube 100.
[0032] A specific embodiment of the present invention has been
disclosed; however, several variations of the disclosed embodiment
could be envisioned as within the scope of this invention. It is to
be understood that the present invention is not limited to the
embodiments described above, but encompasses any and all
embodiments within the scope of the following claims
* * * * *