U.S. patent application number 10/955148 was filed with the patent office on 2005-04-07 for heat exchanger tube assembly.
Invention is credited to Hall, Peter David.
Application Number | 20050072562 10/955148 |
Document ID | / |
Family ID | 34382678 |
Filed Date | 2005-04-07 |
United States Patent
Application |
20050072562 |
Kind Code |
A1 |
Hall, Peter David |
April 7, 2005 |
Heat exchanger tube assembly
Abstract
A heat exchanger tube assembly 10 comprising a tube 12 having a
plurality of fins 14 mounted thereto at spaced intervals along its
length, each fin 14 having at least one aperture 16 through which
the tube 12 is received, each fin 14 having an integral spacer 20
to define the spaced interval from an adjacent fin, the spacer 20
extending from the rim of the aperture 16 generally transversely to
the fin 14 to provide an inner surface profiled to contact and
cooperate with the external surface of the tube 12 to enhance heat
transfer from the tube 12 to the fin 14, the spacer 20 being bonded
to the tube 12 by a thermally-conductive medium.
Inventors: |
Hall, Peter David; (Western
Australia, AU) |
Correspondence
Address: |
STURM & FIX LLP
206 SIXTH AVENUE
SUITE 1213
DES MOINES
IA
50309-4076
US
|
Family ID: |
34382678 |
Appl. No.: |
10/955148 |
Filed: |
September 30, 2004 |
Current U.S.
Class: |
165/182 |
Current CPC
Class: |
F28F 2240/00 20130101;
F28F 21/082 20130101; F28F 1/32 20130101 |
Class at
Publication: |
165/182 |
International
Class: |
F28F 001/30 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 2, 2003 |
AU |
2003905374 |
Claims
I claim:
1. A heat exchanger tube assembly comprising a tube having a
plurality of fins mounted thereto at spaced intervals along its
length, each fin having at least one aperture through which the
tube is received, each fin having an integral spacer to define the
spaced interval from an adjacent fin, the spacer extending from the
rim of the aperture generally transversely to the fin to provide an
inner surface profiled to contact and cooperate with the external
surface of the tube to enhance heat transfer from the tube to the
fin, the spacer being bonded to the tube by a thermally-conductive
medium.
2. A heat exchanger tube assembly as claimed at claim 1 wherein the
fins are formed of generally the same material as the tube.
3. A heat exchanger tube assembly as claimed at claim 2 wherein
said material is a steel.
4. A heat exchanger tube assembly as claimed at claim 1 wherein the
thermally conductive medium occupies a region between the external
surface of the tube and the inner surface of the spacer to thereby
enhance said heat transfer from the tube to the fin.
5. A heat exchanger tube assembly as claimed at claim 1 wherein
each spacer is configured as an annular flange.
6. A heat exchanger tube assembly as claimed at claim 5 wherein
said annular flange is discontinuous around the circumference of
said tube.
7. A heat exchanger tube assembly as claimed at claim 5 wherein
said annular flange comprises a plurality of tabs disposed around
the circumference of said tube.
8. A heat exchanger tube assembly as claimed at claim 1 wherein
said heat exchanger tube assembly is covered with a
corrosion-resistant material.
9. A heat exchanger tube assembly as claimed at claim 8 wherein
said corrosion-resistant material is said thermally-conductive
medium.
10. A heat exchanger tube assembly as claimed at claim 1 wherein
said thermally-conductive medium is zinc or zinc alloy.
11. A heat exchanger comprising a plurality of heat exchanger tube
assemblies as claimed at claim 1, said tubes being held in parallel
spaced relation, adjacent tubes being interconnected by at least
some of said fins, each tube being received through an aperture
provided in said fins, each fin having at least two apertures to
thereby interconnect adjacent tubes.
12. A heat exchanger comprising a plurality of heat exchanger tube
assemblies as claimed at claim 1, said tubes being held in parallel
spaced relation, each tube being interconnected with at least one
adjacent tube by a group of fins, each fin having two apertures to
receive said adjacent tubes to thereby interconnect adjacent
tubes.
13. A method of manufacturing a heat exchanger tube assembly, said
method comprising the steps of mounting a plurality of fins to a
tube and bonding the fins to the tube with a thermally-conductive
medium, each fin having at least one aperture through which the
tube is received, each fin having an integral spacer to define the
spaced interval from an adjacent fin, the spacer extending from the
rim of the aperture generally transversely to the fin to provide an
inner surface profiled to contact and cooperate with the external
surface of the tube to enhance heat transfer from the tube to the
fin.
14. A method of manufacturing a heat exchanger tube assembly as
claimed at claim 13 further comprising the step of covering the
fins and tube with a corrosion-resistant material.
15. A method of manufacturing a heat exchanger tube assembly as
claimed at claim 14 wherein the methods of bonding the fins to the
tube and covering of the fins and tube comprises a hot-dip, zinc or
zinc-alloy galvanising procedure.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a heat exchanger tube
suitable to be incorporated into a heat exchanger, as well as a
method of manufacturing such a heat exchanger tube.
BACKGROUND ART
[0002] Heat exchangers are utilised in a broad range of
applications where it is necessary to transfer heat to or from a
particular item of equipment, such as an air compressor, air
conditioning unit, booster or engine.
[0003] A typical heat exchanger commonly used in air or gas heating
and cooling applications such as those identified above is that of
the "cross-flow" type. Such exchangers generally comprise an
arrangement of tubes through which a first fluid is passed and
across which a second fluid (often a gas) is passed.
[0004] A particular type of cross-flow exchanger comprises an
arrangement of tubes, each of which is provided with a plurality of
fins along, and extending generally transverse to, its length.
Where the heat exchanger is being utilised to cool the equipment
concerned, hot fluid from that equipment is passed through the
tubes whilst a cooler fluid (often a gas) is passed over the fins
and tubes to extract heat therefrom and thus to cool the hot fluid.
The fins assist in cooling the hot fluid by providing a large heat
transfer area. It is desirable that the fins be thin to maximise
the surface area available for transfer of heat within the
particular space available..
[0005] In this particular type of cross-flow exchanger, it is often
necessary that the fluid be passed through the tubes under
relatively high pressures. As a result, it is in many instances
also desirable that the tubes be robust.
[0006] Cross-flow heat exchangers generally use fins made of
aluminium or copper due to the excellent heat conduction
characteristics of those metals. However, their use introduces
other problems.
[0007] Generally the tubes used are not made of the same metal as
they are required to be more robust. Galvanic corrosion tends to
occur as a result of the dissimilarity in the metals. Such galvanic
corrosion gives rise to oxides which are poor conductors of heat
and which thus compromises the heat transfer between the tubes and
fins.
[0008] A further disadvantage, is the relative softness of those
metals and thus the vulnerability of the fins to damage,
particularly from impact such as during cleaning with a high
pressure hose. Moreover, those metals oxidise and/or perish over
time in harsh operating conditions.
DISCLOSURE OF THE INVENTION
[0009] Accordingly, the invention resides in a heat exchanger tube
assembly comprising a tube having a plurality of fins mounted
thereto at spaced intervals along its length, each fin having at
least one aperture through which the tube is received, each fin
having an integral spacer to define the spaced interval from an
adjacent fin, the spacer extending from the rim of the aperture
generally transversely to the fin to provide an inner surface
profiled to contact and cooperate with the external surface of the
tube to enhance heat transfer from the tube to the fin, the spacer
being bonded to the tube by a thermally-conductive medium.
[0010] According to a preferred feature of the invention, the fins
are formed of generally the same material as the tube.
[0011] According to a preferred embodiment, said material is a
steel.
[0012] According to a preferred feature of the invention, the
thermally conductive medium occupies a region between the external
surface of the tube and the inner surface of the spacer to thereby
enhance said heat transfer from the tube to the fin.
[0013] According to a preferred feature of the invention, each
spacer is configured as an annular flange.
[0014] According to a preferred embodiment, said annular flange is
discontinuous around the circumference of said tube.
[0015] According to a preferred embodiment, said annular flange
comprises a plurality of tabs disposed around the circumference of
said tube.
[0016] According to a preferred feature of the invention, said fins
are resistant to permanent deformation under conditions typically
encountered by a heat exchanger.
[0017] According to a further preferred feature of the invention,
each spacer is closely adjacent the external surface of said
tube.
[0018] According to a preferred feature of the invention, said heat
exchanger tube assembly is covered with a corrosion-resistant
material.
[0019] According to a preferred feature of the invention, said
corrosion-resistant material is said thermally-conductive
medium.
[0020] A heat exchanger tube assembly as claimed in any one of the
preceding claims wherein said thermally-conductive medium is zinc
or zinc alloy.
[0021] According to a further aspect the invention resides in a
heat exchanger comprising a plurality of heat exchanger tube
assemblies as previously descibed, said tubes being held in
parallel spaced relation, adjacent tubes being interconnected by at
least some of said fins, each tube being received through an
aperture provided in said fins, each fin having at least two
apertures to thereby interconnect adjacent tubes.
[0022] According to a further aspect the invention resides in a
heat exchanger comprising a plurality of heat exchanger tube
assemblies as previously descibed, said tubes being held in
parallel spaced relation, each tube being interconnected with at
least one adjacent tube by a group of fins, each fin having two
apertures to receive said adjacent tubes to thereby interconnect
adjacent tubes.
[0023] According to a further aspect the invention resides in
method of manufacturing a heat exchanger tube assembly, said method
comprising the steps of mounting a plurality of fins to a tube and
bonding the fins to the tube with a thermally-conductive medium,
each fin having at least one aperture through which the tube is
received, each fin having an integral spacer to define the spaced
interval from an adjacent fin, the spacer extending from the rim of
the aperture generally transversely to the fin to provide an inner
surface profiled to contact and cooperate with the external surface
of the tube to enhance heat transfer from the tube to the fin.
[0024] According to a preferred feature of the invention, the
method further comprises the step of covering the fins and tube
with a corrosion-resistant material.
[0025] According to a preferred embodiment, the methods of bonding
the fins to the tube and covering of the fins and tube comprises a
hot-dip, zinc or zinc-alloy galvanising procedure.
[0026] The invention will be more fully understood in the light of
the following description of specific embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The description is made with reference to the accompanying
drawings of which:
[0028] FIG. 1 is a perspective view of a heat exchanger tube
according to the first embodiment with part of its coating shown
cut-away (for clarity);
[0029] FIG. 2 is a front elevation view of the heat exchanger of
FIG. 1;
[0030] FIG. 3 is a perspective view of a fin of the type
incorporated in the heat exchanger tube of FIG. 1;
[0031] FIG. 4 is a perspective view of a heat exchanger tube
according to the second embodiment;
[0032] FIG. 5 is a perspective view of a fin of the type
incorporated in the heat exchanger tube of FIG. 4;
[0033] FIG. 6 is a perspective view of a heat exchanger tube
assembly according to the third embodiment of the invention and
comprising fins of the type depicted in FIG. 5;
[0034] FIG. 7 is a front elevation view of a repeating unit of the
type incorporated in the heat exchanger tube assembly shown in FIG.
6; and
[0035] FIG. 8 is a perspective view of a heat exchanger tube
assembly according to a fourth embodiment of the invention and
comprising fins of the type depicted in FIG. 5.
DETAILED DESCRIPTION OF THE SPECIFIC EMBODIMENTS
[0036] FIGS. 1, 3 and 5 illustrate the first, second and third
embodiments respectively. Each of those embodiments comprises at
least one tube and a plurality of fins mounted thereto. Each fin
has at least one aperture through which the tube is received.
[0037] The heat exchanger tube assembly 10 according to the first
embodiment is shown at FIGS. 1 and 2 and comprises a tube 12 and a
plurality of fins 14 mounted to the tube 12. The tube is typically
made from steel due to the robust properties provided by that
material which enable it to withstand harsh environments. In
particular, it has the ability to resist fatigue when subject to
vibration, provided the system is designed appropriately. As well,
it is able to withstand substantial knocks, impacts and the
like.
[0038] Each fin 14 has an aperture 16 through which the tube 12 is
received and is also provided with a spacer 20 on an axial face
thereof. In other embodiments, such spacers may be provided on both
axial faces of each fin. The spacers 20, which are located between
adjacent fins 14, maintain a regular spacing between those fins 14
along the tube 12. The fins 14 are formed of generally the same
material which, in the case of this embodiment, is steel.
[0039] A detailed view of a fin 14 of the type used in the first
embodiment is shown at FIG. 3.
[0040] The spacer 20 is integrally formed with the fins 14 and
extends from the rim of the aperture 16 generally transversely to
the fin 14. It is thereby positioned so as to be closely adjacent
to the external surface of the tube 12. The spacer 20 is configured
as an annular flange so as to conform with the external surface of
the tube 12. The annular flange is discontinuous around its
circumference to provide a plurality of tabs around the rim of the
aperture 16. In this embodiment, the tabs are disposed at regular
angular intervals around the rim of the aperture 16.
[0041] The fin 14 is produced from steel sheeting, the aperture 16
being stamped therein to be of a diameter which is such that the
aperture 16 which will snugly receive the tube 12 therethrough. The
stamping device is suitably formed to produce tabs 20, initially in
the plane of the fin 14. The tabs 20 are then bent out of that
plane to extend from the rim of the aperture. In the forming
process, the tabs are suitably profiled to provide an inner surface
to contact and cooperate with the external surface of the tube to
enhance heat transfer from the tube to the fin.
[0042] In the case of the embodiments described herein, each of the
fins 14 is discrete though, in alternative embodiments, the fins
may be provided as a one-piece assembly such as in the form a
helix.
[0043] The fins 14 are bonded to the tube 12 by zinc 11 which is a
thermally-conductive and corrosion resistant medium. The zinc 11
occupies the regions between the external surface of the tube 12
and the inner radial faces both of the fins 14 and the tabs 20,
giving rise to a substantially continuous bond between the fins 14
and the tube 12. The manner in which this is achieved is discussed
further below. The substantially continuous bond provides for
efficient heat transfer from the tube to the fins and also creates
a relatively robust mounting of the fins 14 to the tube 12. The
entire exterior of the heat exchanger tube 10 is also coated in
zinc to render it corrosion-resistant.
[0044] The method of manufacturing the heat exchanger tube 10 will
now be described with reference to the drawings. Firstly, the fins
14, which may have been formed in the manner described above, are
received over the tube 12 such that the spacer 20 of each fin 14
abuts an adjacent fin 14 (best shown at FIG. 2). If it is felt
necessary, the fins 14 may then be tack welded to the tube 12 to
assist in locating the fins 14 in their desired position on the
tube 12 prior to coating with the zinc 11. Alternatively, they may
be of a sufficiently snug fit that no such welding is needed.
[0045] The fins 14 and tube 12 forming the heat exchanger tube 10
are then hot-dipped in molten zinc to galvanise the heat exchanger
tube 10. Hot-dipping of the heat exchanger tube 10 in zinc is
advantageous in that it not only renders the heat exchanger tube 10
corrosion-resistant but simultaneously bonds the fins 14 to the
tube 12. Moreover, the zinc, as applied by hot-dipping is pervasive
and occupies the regions between the external surface of the tube
12 and the inner radial faces both of the fins 14 and the tabs 20,
giving rise to the substantially continuous bond between the fins
14 and the tube 12 and thus providing for efficient heat transfer,
as described above.
[0046] It will thus be appreciated that the spacer 20 provides two
functions: namely it acts to provide a definite, predefined spacing
between adjoining fins to simply assembly of the fins as one fin
may be pressed along the tube 12 until it contacts the spacer of
the previous fin, and more importantly, the inner surface of the
spacer 20 provides a broad area of contact with tube 12 to enable
better transfer of heat from the tube 12 to the fin 14. In this
regard a spacer comprising a continuous annular flange might well
provide the best solution from this point of view. However, by
segmenting the spacer 20 into tabs the fins 14 are more easily
mounted to the tube 12 and it is even less likely that zinc will
fail to penetrate between the tube 12 and the inner surface of the
spacer 20 during the hot-dip process.
[0047] The heat exchanger tube 10 is relatively robust, owing to
the fins 14 being formed of steel, which is resistant to permanent
deformation, and also due to the continuity and area, and thus the
strength, of the zinc bond between the external surface of the tube
12 and the inner radial faces both of the fins 14 and the tabs
20.
[0048] It has been found that the use of steel fins with the
inherently lower heat conductivity as compared with metals such as
copper and aluminium results in little deterioration in overall
performance of the heat exchanger. It is believed that this is
partly due to the high thermal conductivity of the zinc and because
the reduction in conductivity is compensated for by the improvement
in the bond, and thus in the heat conductivity of the junction,
between the fins 14 and the tube 12.
[0049] Furthermore, galvanic corrosion between the fins 14 and the
tube 12 is eliminated because the fins 14 and the tube 12 are made
of substantially the same material, while the zinc coating provides
the well known galvanic protection to the assembly. In particular,
corrosion at the junction between the fins and the tubes is
eliminated. At the same time, the zinc coating provides stiffness
to the fins and the tubes. In particular, in use, the steel fins
are able to withstand the force of high pressure sprays used for
cleaning without permanent deflection thereby better maintaining
their cooling effectiveness during the life of the heat
exchanger.
[0050] The heat exchanger tube assembly 10, in addition to offering
the abovementioned advantages, is relatively economic to
manufacture.
[0051] The second embodiment of the invention is illustrated at
FIG. 4. The second embodiment is a variation of the first
embodiment though the heat exchanger tube 10 comprises a pair of
parallel tubes 12 respectively received through a pair of apertures
16.
[0052] A fin 14 of the type used in the second embodiment is shown
at FIG. 5. The fin 14 is manufactured in an identical fashion to
that which is incorporated in the first embodiment though it is
formed with a pair of apertures 16 each of which is provided with a
spacer 20 identical to that described in connection with the first
embodiment.
[0053] The advantage offered by the second embodiment, over the
first, is that a given number of fins 14 in this embodiment is
sufficient for two tubes 12 rather than just one tube. This results
in a saving in manufacturing costs because the labour required in
cutting and/or stamping a single fin is not significantly greater
than that required to produce a fin in accordance with the first
embodiment.
[0054] A further advantage is a stiffening effect which is created
along the axis between the pair of adjacent tubes 12 as a result of
their being tied together by the fins 14. This can reduce
vibration, both of the heat exchanger tube 10 and in the heat
exchanger generally, and thus increase the life of the heat
exchanger.
[0055] The third embodiment of the invention, which is illustrated
at FIG. 6, is a heat exchanger tube assembly 100 based on a
variation of the heat exchanger tube 10 according to the second
embodiment. The heat exchanger tube assembly 100 comprises a
plurality of tubes 12 interconnected by fins 14 of the type
illustrated in FIG. 5.
[0056] The heat exchanger tube assembly 100 is comprised of a
series of repeating units, one such unit 40 being illustrated at
FIG. 7. The unit 40 is similar to the heat exchanger tube 10
depicted at FIG. 4 though alternate fins 14', along the length of
one of the tubes 12', do not extend to the other tube 12" in that
unit 40, the unoccupied apertures 16' of those alternate fins 14'
instead being intended to receive another tube 12" of an identical
unit 40 shown in broken lines.
[0057] The assembly 100 is formed from the desired number of units
40 prior to hot-dipping. As can be seen at FIG. 6, the tubes 12 in
that assembly 100 need not be coplanar, thus enabling the
configuration of the assembly 100 to be adjusted so as to conform
with space restrictions and/or the layout of adjacent equipment.
Indeed, the ability to interlink tubes with the fins in this manner
enables novel heat exchanger configurations to be devised. FIG. 8
illustrates a fourth embodiment which shows an arrangement 110
providing a group of 8 tubes 12 which are disposed in a octagonal
configuration and interlinked with fins 14. As there are no end
tubes, such a configuration has a high degree of inherent rigidity
requiring little additional support. As well, such a configuration
allows the cooling fluid to be either supplied or withdrawn from a
direction parallel to the tubes 12, rather than transverse to them,
which may be beneficial in certain applications.
[0058] Once that configuration has been suitably adjusted, the fins
14 may be tack welded to the respective tubes 12, prior to
hot-dipping, so as to assist in locating the fins 14 in their
desired position on the tubes 12 and to maintain the configuration
of the assembly 100.
[0059] An advantage offered by this embodiment, and shared by the
second embodiment, is the stiffening effect which is created along
the axis between the pairs of adjacent tubes 12' and 12" as a
result of their being tied together by the fins 14'. Such a
stiffening effect is also realised along the axis between the pairs
of adjacent tubes 12' and 12" as a result of their being tied
together by the fins 14' and also the fins 14". The fins 14' and
14" thus offer lateral restraint to tubes 12' and 12" throughout
the assembly 100, thus possibly reducing vibration, both of the
assembly 100 and in the heat exchanger generally and increasing the
life of the heat exchanger. Moreover, it can be seen that the tube
which is second-from-right in FIG. 5 is, advantageously, laterally
restrained in two different axes, those axes extending between that
tube and the tubes to its left and right (which are not coplanar)
respectively.
[0060] As an alternative to the unit 40 shown in FIG. 7, units
comprising fins of other profiles and having any number of
apertures (i.e. possibly more than two apertures) are possible. It
is clear that such units may be tied to other units, whether like
or unlike, using suitably-profiled fins having appropriately-spaced
apertures, those fins, depending on the arrangement of the
apertures, being able to provide stiffening and lateral restraint
along several different lateral axes. It should also be appreciated
that the arrangement of the fins 14' with respect to the fins 14"
need not be staggered as depicted in FIG. 6, provided those fins
still provide adequate lateral restraint, stiffening and heat
transfer characteristics throughout the heat exchanger
assembly.
[0061] It should be appreciated that the scope of the present
invention need not be limited to the particular scope of the
embodiments described above.
[0062] Throughout the specification, unless the context requires
otherwise, the word "comprise" or variations such as "comprises" or
"comprising", will be understood to imply the inclusion of a stated
integer or group of integers but not the exclusion of any other
integer or group of integers.
* * * * *