U.S. patent application number 14/084671 was filed with the patent office on 2014-06-19 for heat exchanger and method.
This patent application is currently assigned to Whirlpool Corporation. The applicant listed for this patent is Whirlpool Corporation. Invention is credited to NORMAN G. BEATY, NIHAT O. CUR.
Application Number | 20140166252 14/084671 |
Document ID | / |
Family ID | 50929586 |
Filed Date | 2014-06-19 |
United States Patent
Application |
20140166252 |
Kind Code |
A1 |
CUR; NIHAT O. ; et
al. |
June 19, 2014 |
HEAT EXCHANGER AND METHOD
Abstract
A shell and tube heat exchanger includes a plurality of tubes
having non-circular cross sectional shapes to improve heat
transfer. The tubes may have central portions having an oblong
cross-sectional shape with generally flat opposite side faces. The
side faces may include raised portions to increase heat transfer.
Alternatively, the tubes may have a C-shape in cross section. The
shape of the tubes promotes thin film boiling of the fluid in the
tubes to improve heat transfer.
Inventors: |
CUR; NIHAT O.; (St. Joseph,
MI) ; BEATY; NORMAN G.; (Smyrna, TN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Whirlpool Corporation |
Benton Harbor |
MI |
US |
|
|
Assignee: |
Whirlpool Corporation
Benton Harbor
MI
|
Family ID: |
50929586 |
Appl. No.: |
14/084671 |
Filed: |
November 20, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61738080 |
Dec 17, 2012 |
|
|
|
Current U.S.
Class: |
165/157 ;
165/173; 165/177 |
Current CPC
Class: |
F28F 2210/00 20130101;
F28F 2001/027 20130101; F28B 1/02 20130101; F28F 1/025 20130101;
F28D 7/1684 20130101; F28F 1/022 20130101; F28D 3/02 20130101; F28F
1/426 20130101 |
Class at
Publication: |
165/157 ;
165/173; 165/177 |
International
Class: |
F28D 3/02 20060101
F28D003/02 |
Claims
1. A heat exchanger, comprising: a shell defining a cavity and
including fluid inlets and outlets to permit flow of a first fluid
through the cavity; an inner tube assembly comprising at least one
elongated tube and fluid conduits connected to opposite ends of the
tube, the fluid conduits extending outside the shell to permit flow
of a second fluid through the inner tube assembly; and wherein: the
at least one tube includes an elongated internal passageway,
wherein at least a portion of the elongated internal passageway of
the tube has an oblong shape in cross section to promote thin film
boiling of fluid flowing through the elongated internal passageway
to thereby provide increased heat transfer from the first fluid to
the second fluid.
2. The heat exchanger of claim 1, wherein: the tube comprises a
plurality of tubes having elongated internal passageways, wherein
at least a portion of the elongated passageways have oblong shapes
in cross section.
3. The heat exchanger of claim 2, wherein: each tube has opposite
ends, each opposite end defining a substantially circular
opening.
4. The heat exchanger of claim 3, wherein: each tube includes
transition sections extending between the substantially circular
openings and the portion of each tube having an oblong shape in
cross section.
5. The heat exchanger of claim 4, wherein: each tube includes an
elongated central portion having an oblong cross sectional
shape.
6. The heat exchanger of claim 5, wherein: the elongated central
portion of each tube includes a pair of generally planar side wall
portions that are spaced apart, and a pair of curved sidewall end
portions interconnecting the generally planar side wall
portions.
7. The heat exchanger of claim 6, wherein: the generally planar
side wall portions have a substantially uniform thickness.
8. The heat exchanger of claim 7, wherein: at least a portion of
each generally planar side wall portion includes a plurality of
raised portions forming protrusions on outer surfaces of each
generally planar side wall portion.
9. The heat exchanger of claim 8, wherein: the protrusions comprise
elongated ridges extending along the tubes.
10. The heat exchanger of claim 8, wherein: the protrusions
comprise a plurality of generally circular bulges.
11. The heat exchanger of claim 1, wherein: the at least one tube
comprises sheet metal having a substantially uniform thickness.
12. A tube assembly for a shell and tube heat exchanger, the tube
assembly comprising: first and second end plates having a plurality
of generally circular openings therethrough; a plurality of tubes
extending between the first and second end plates, each tube having
opposite end portions with outer surfaces that have a generally
circular cross sectional shape, wherein the opposite end portions
are received in the openings of the first and second end plates and
being connected thereto; and wherein: the tubes have flattened
central portions forming fluid passageways having oblong cross
sectional shapes to thereby provide improved heat transfer.
13. The tube assembly of claim 12, wherein: the flattened central
portions of each tube includes a pair of spaced apart side wall
portions that are generally planar.
14. The tube assembly of claim 13, wherein: each tube includes
curved side wall portions extending between and interconnecting the
generally planar side wall portions.
15. The tube assembly of claim 13, wherein: the generally planar
side wall portions include a plurality of raised portions forming
protrusions on outer surfaces of each generally planar side wall
portion.
16. The heat exchanger of claim 15, wherein: the protrusions
comprise elongated ridges extending along the tubes.
17. The heat exchanger of claim 15, wherein: the protrusions
comprise a plurality of generally circular bulges.
18. A tube for shell and tube heat exchangers, the tube comprising:
an elongated tubular structure having spaced apart inner and outer
side walls that are generally C-shaped in cross section, wherein
the inner and outer side walls are interconnected by transverse end
wall portions to form an internal passageway that is generally
C-shaped.
19. The tube of claim 18, wherein: the inner and outer side walls
define outer surfaces that are generally cylindrical in shape.
20. The tube of claim 18, wherein: the tube comprises sheet metal
having elongated opposite edge portions that are interconnected to
form a tube.
21. The tube of claim 20, wherein: the opposite edge portions are
interconnected by folds to form a first transverse end wall
portion.
22. The tube of claim 21, wherein: the tube comprises a single
piece of sheet metal that is deformed to define a second transverse
end wall portion.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/738,080 filed on Dec. 17, 2012, entitled, "HEAT
EXCHANGER AND METHOD", the entire contents of which are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] Various types of shell and tube heat exchangers have been
developed. Known heat exchangers may include a shell having fluid
inlets and outlets to provide for circulation of fluid through the
shell. A plurality of smaller tubes are disposed within the shell.
The smaller tubes have inlets and outlets disposed outside the
shell whereby fluid can flow through the tubes. Heat is thereby
exchanged between the fluid flowing through the shell and the fluid
flowing through the tubes.
[0003] With reference to FIG. 1, a known shell and tube heat
exchanger construction may include an inner assembly comprising a
plurality of tubes 1 having opposite ends 2 and 3 that are
connected to end plates 4 and 5, respectively, at openings 7 and 8.
O rings 6 may be utilized to seal the ends 2 and 3 to openings 7
and 8, in end plates 4 and 5. A solid rod 9 may be positioned
inside each tube 1 to create an annular space 10 between the solid
rod 9 and the tubes 1. The tube assembly of FIG. 1 is positioned
inside a shell (not shown) when the heat exchanger is fully
assembled. In use, fluid flows through the small annular space 10
to thereby transfer heat between fluid flowing through tubes 1 and
the fluid flowing through the shell (not shown). U.S. Pat. Nos.
7,785,448 and 8,069,676 also disclose heat exchangers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 is a partially exploded isometric view of a portion
of a prior art heat exchanger;
[0005] FIG. 2 is a cross sectional view of a heat exchanger
according to one aspect of the present invention;
[0006] FIG. 3 is a cross sectional view of the heat exchanger of
FIG. 1 taken at an orientation that is rotated 90.degree. relative
to the orientation of FIG. 1;
[0007] FIG. 4 is a cross sectional view of the heat exchanger of
FIG. 3 taken along the line IV-IV;
[0008] FIG. 5 is a partially schematic view of a tube being formed
according to one aspect of the present invention;
[0009] FIG. 6 is a view of a tube that has been deformed according
to one aspect of the present invention;
[0010] FIG. 6A is an enlarged end view of the tube of FIG. 6;
[0011] FIG. 7 is a view of a tube that has been deformed according
to another aspect of the present invention;
[0012] FIG. 7A is an enlarged end view of the tube of FIG. 7;
[0013] FIG. 8 is a flattened tube according to another aspect of
the present invention;
[0014] FIG. 8A is an enlarged end view of the tube of FIG. 8;
[0015] FIG. 9 is an isometric view of the tube of FIGS. 6 and
7;
[0016] FIG. 10 is an isometric view of a subassembly of a heat
exchanger including flattened tubes that have been connected to a
pair of end plates;
[0017] FIG. 11 is a cross sectional view of a heat exchanger
according to another aspect of the present invention;
[0018] FIG. 12 is a cross sectional view of the heat exchanger of
FIG. 11 taken along the line XII-XII;
[0019] FIG. 13 is a cross sectional view of the heat exchanger of
FIG. 11 taken along the line XIII-XIII;
[0020] FIG. 14 is a fragmentary view of a tube for the heat
exchanger of FIG. 11, wherein the tube is C-shaped in cross
section;
[0021] FIG. 15 is an enlarged end view of an extruded version of
the tube of FIG. 14;
[0022] FIG. 16 is an enlarged end view of a version of the tube of
FIG. 14 wherein the tube is formed from sheet metal;
[0023] FIG. 17 is an enlarged view of a portion of the tube of FIG.
16 during the forming process;
[0024] FIG. 18 is an enlarged view of a portion of the tube of FIG.
16 showing the final deformed shape of the sheet metal utilized to
form the tube; and
[0025] FIG. 19 is a fragmentary isometric view of the tube of FIG.
14.
DETAILED DESCRIPTION
[0026] With reference to FIGS. 2 and 3, a heat exchanger 15
according to one aspect of the present invention includes a shell
16 and a tube assembly 18 disposed in a cavity 20 of shell 16. An
inlet 22 receives super heated steam or vapor "A" (FIG. 2) that
flows across boiler tubes 24. The steam or vapor condenses inside
shell 16 due to cooling provided by tubes 24, and the water flows
out of an exit 26 of shell 16 in the form of distilled liquid water
28.
[0027] The tube assembly 18 includes a plurality of boiler tubes 24
having opposite ends 30 and 32 that are connected to end plates 34
and 36, respectively. End plate 36 is fluidly connected to a fluid
inlet 38 that receives inlet or tap water 40. The water 40 flows
upwardly through the boiler tubes 24, and enters space 42 above
plate 34 in the form of steam or vapor. The steam/vapor 46 exits
space 42, and flows to a blower or compressor (not shown). Waste
water and particulate matter 48 flows out of an outlet 50 of shell
16. The heat exchanger 15 may include a flow straightener 52
positioned on or adjacent plate 36 to direct the flow of water from
inlet 38 through end plate 36 into tubes 24. As discussed in more
detail below, tubes 24 include end portions 54 having a circular
cross sectional shape enabling the ends to be connected to circular
openings 56 in end plates 34 and 36. The tubes 24 also include
flattened central portions 58 forming an elongated/flat passageway
60 to promote heat transfer between fluid flowing through tubes 24
and fluid flowing through cavity 20 of shell 16. As discussed in
more detail below, the tubes 24 provide increased heat transfer,
such that the length "L" of the tubes 24 and length "L1" of the
heat exchanger 15 can be significantly reduced relative to known
configurations.
[0028] During fabrication (FIG. 5), a tube 12 having a circular
cross sectional shape with generally uniform wall thickness is
flattened utilizing die or forming members 14 to thereby form
flattened central portion 58. End plugs 62 include cylindrical
portions 64 that are closely received in open ends 66 of tube 12
immediately prior to forming by forming members 14. The cylindrical
portions 64 remain inserted in the open ends 66 of tube 12 as
forming members 14 deform the tube 12 to thereby insure that the
ends 154 of tubes 12 retain a circular cross-sectional shape.
[0029] Referring to FIGS. 6, 6A, 7, and 7A the side walls 68 of
flattened central portion 58 may be substantially flat, or the side
walls 68 may include a plurality of elongated raised portions 70
that further increase the surface area of flattened central portion
58. It will be understood that the flattened central portion 58 may
be formed in more than one step utilizing a series of forming
members or dies 14 as required for a particular application. Also,
a forming member or fluidic materials such as oil or semi-fluidic
materials such as sand or iron filings (not shown) may be inserted
into flattened portion 58 of tube 12 following an initial forming
step to thereby facilitate additional forming steps to form
elongated raised portions 70. The tubes 24 include a transition
zone or portion 72 having a shape that transitions between the
flattened central portion 58 and the end portions 54. The wall
thickness of the tube following the forming process is preferably
uniform or approximately uniform.
[0030] With further reference to FIG. 8, a tube 24A according to
another aspect of the present invention includes a flattened
central portion 58A having a plurality of raised portions 74 that
increase the surface area of side walls 68A of tube 24A. Raised
portions 74 may have a dome-like shape, with a generally uniform
wall thickness in the raised portions 74 and surrounding planar
portions. Tube 24A may be formed in substantially the same manner
as tube 24, and includes circular ends 54 that can be connected to
end plates 34 and 36.
[0031] With further reference to FIGS. 9 and 10, end plates 34 and
36 include a plurality of circular openings 76. The openings 76 may
be formed by punching, extruding, or other suitable process, and
may be flared to provide increased surface area in the vicinity of
the joint formed with ends 54 of tubes 24. During assembly, ends 54
of boiler tubes 24 are inserted into the circular openings 76 of
end plates 34 and 36 and secured thereto to form a subassembly 80.
The ends 54 of tubes 24 may be flared outwardly or otherwise formed
utilizing a "bullet" (not shown) or other suitable forming
operation to thereby secure ends 54 of tubes 24 to end plates 34
and 36. The ends 54 may also be soldered or brazed at the joints
where ends 54 of tubes 24 connect with end plates 34 and 36.
[0032] It will be understood that the flattened central portions 58
may, in some cases, be formed after the tubes 12 are connected to
the end plates 34 and 36. For example, the ends 54 of a tube 12 may
be positioned in openings 76, and a single forming member or
"bullet" may be drawn or pushed through the length of tube 12 to
thereby expand the tube 12 along its entire length. This expansion
causes a tight mechanical fit between ends 54 of a tube 12 and end
plates 34 and 36. Soldering or brazing may also be utilized to
secure the joints between tubes 12 and end plates 34 and 36. The
individual tubes 12 may then be flattened utilizing forming members
or dies 14 after the tubes 12 are connected to the end plates 34
and 36.
[0033] In FIG. 10, end plates 34 and 36 have a rectangular
perimeter. However, end plates 34 and 36 may also have a circular
perimeter that corresponds to the circular cross-sectional shape of
shell 16 as shown in FIG. 4. Also, shell 16 (FIGS. 2-4) may have a
square or rectangular cross-sectional shape, and end plates 34 and
36 may have corresponding rectangular perimeters.
[0034] The boiler tubes 24 may be formed of copper, aluminum, or
other suitable material. If the tubes 12 comprise aluminum or other
material that degrades when exposed to heat, steam, boiling water,
etc., the tubes 24 may be coated with an epoxy material or other
suitable coating to insure that the tubes 24 can withstand the
adverse conditions experienced during operation of heat exchanger
15.
[0035] After subassembly 80 (FIG. 10) is formed, the shell 16
(FIGS. 2-4), inlet and outlet fittings, and other components may be
assembled with the subassembly 80 utilizing known processes.
[0036] The flattened central portions 58 of tubes 24 promote thin
film boiling of water passing through the tubes 24 to thereby
provide for efficient transfer of heat between fluid passing
through tubes 24 and fluid circulating through cavity 20 of shell
16. The passageways 60 formed by flattened central portions 58 have
an oblong cross sectional shape with an internal dimension of about
0.2 by about 1.5 inches. It will be understood that the specific
dimensions of the flattened portions 58 of tubes 24 and the
internal passageways 60 may vary depending upon the requirements of
a particular application. In contrast to known tubes with internal
rods (e.g. FIG. 1), heat is transferred to/from internal
passageways 60 on the two elongated sides of the extended perimeter
oval profile (i.e. through both side walls 68) rather than the
shorter perimeter of the circular profile.
[0037] With further reference to FIGS. 11-13, a heat exchanger 15A
according to another aspect of the present invention includes a
shell 16A that is substantially similar to the shell 16 described
in more detail above in connection with FIGS. 2-4. Heat exchanger
15A includes a plurality of tubes 24A (see also FIGS. 14-19). Each
tube 24A has a substantially C-shaped cross section. Tubes 24A
include cylindrical concave inner surface portions 82 and convex
outer cylindrical surface portions 84, and an elongated internal
passageway 86. Internal passageway 86 is generally C-shaped. In the
illustrated example, passageway 86 is preferably about 0.2 inches
between inner and outer side walls 88 and 90, and about 2.0 inches
long, such that the cross-sectional area of passageway 86 is about
0.4 square inches.
[0038] Tubes 24A may be formed from extruded aluminum or other
suitable material as shown in FIG. 15. Extruded tube 24A may
include integral transverse inner walls 89 defining three internal
passageways 86A, 86B, and 86C.
[0039] Alternatively, tubes 24A may be formed from sheet metal or
the like as shown in FIG. 16. The sheet metal may have a bend or
fold forming a curved edge 96 interconnecting formed/curved inner
and outer side wall portions 88 and 90. As shown in FIG. 17, an
edge portion 92 (FIG. 17) of side wall 88 may then be deformed to
bring it into contact with edge portion 94. The edge portion 94 of
side wall 90 may then be folded/formed to form an elongated sealed
joint 98 as shown in FIG. 18.
[0040] The folding operations of FIGS. 17 and 18 utilized to form
sealed joint 98 may comprise high speed forming that causes the end
portions 94 and 96 of side walls 88 and 90 to become fused together
due to melting/bonding of the edges 92 and 94. High speed forming
of this type is generally known, such that the details of this
process will not be described in detail herein. Alternatively, the
edge portions 92 and 94 may be deformed utilizing rollers or other
forming tools, and the joint 98 may then be sealed utilizing
solder, brazing, epoxy, or the like.
[0041] The tubes 24A form elongated passageways 86A, 86B, and 86C
(FIG. 15) or 86
[0042] (FIG. 16) that are somewhat similar to an annular shape,
except that the internal passageways 86 are generally C-shaped as a
result of the tubes 24A being formed by extrusion (FIG. 15) or from
a single piece of sheet metal (FIGS. 16-18) (in contrast to the
known tubes 1 and solid rods 9 of FIG. 1) having a cylindrical
outer surface of the same radius as outer wall 90. Also, the
surface areas of external surfaces of inner wall 88 and outer wall
90 are significantly larger than the cylindrical outer surface of a
conventional tube (e.g. FIG. 1), and provide for heat transfer on
both sides of passageways 86. The increased surface area provides
increased heat transfer between fluid inside tubes 24A and fluid in
shell 16A relative to conventional tubes (FIG. 1).
[0043] End plates 34A and 36A of heat exchanger 15 (FIGS. 11-13)
may include C-shaped openings to closely receive the ends 54A of
tubes 24A. Ends 54A of tubes 24A may be secured to end plates 34A
and 36A by forming ends 54A, or by utilizing epoxy, solder,
brazing, or the like to provide a secure, sealed bond between tubes
24A and end plates 34A and 36A.
[0044] The transfer of heat into passageway 86 (or passageways 86A,
86B, and 86C) through side walls 88 and 90 on both sides of the
internal passageways 86 promotes thin film boiling of water flowing
through tubes 24A. This increases heat transfer between material
flowing through tubes 24A and fluid flowing through shell 16A of
heat exchanger 15A. Similarly, heat is transferred through both
side walls 68 of tubes 24 (FIGS. 2-10) on both sides of passageways
60 to promote thin film boiling of water or other fluid in
passageways 60. Because the heat transfer is improved, the length L
(FIGS. 2, 10, and 11) of tubes 24 and 24A can be significantly
reduced compared to known heat exchangers utilizing round tubes or
round tubes with internal rods (e.g. FIG. 1). The length L1 of the
heat exchanger (FIGS. 2 and 11) can therefore also be reduced
significantly. In general, for a given heat transfer capability the
lengths L and L1 can be reduced by 10%-20% or more relative to a
conventional arrangement (FIG. 1).
[0045] As discussed above, the tubes 24 and 24A, and end plates 34,
36, 34A, and 36A may be formed from a suitable metal material such
as copper or aluminum. Alternatively, one or more of these
components may be formed from polymer materials having the required
strength and durability required to withstand the operating
conditions of the heat exchangers 15, 15A.
[0046] A heat exchanger according to the present invention as
described above in connection with FIGS. 1-19 may be utilized in a
wide variety of applications. For example, the inventive heat
exchanger may be utilized as an evaporator and/or a condenser in
refrigeration systems. It will be understood that the shape, size,
and number of tubes and other components may vary according to the
requirements of a particular application.
* * * * *