U.S. patent application number 11/699779 was filed with the patent office on 2007-06-07 for finned helicoidal heat exchanger.
Invention is credited to Ahmad Fakheri.
Application Number | 20070125528 11/699779 |
Document ID | / |
Family ID | 38117569 |
Filed Date | 2007-06-07 |
United States Patent
Application |
20070125528 |
Kind Code |
A1 |
Fakheri; Ahmad |
June 7, 2007 |
Finned helicoidal heat exchanger
Abstract
Heat exchanger having a plurality of heat transfer tubes
arranged substantially in the shape of a helicoidal tube with the
individual coils running parallel to one another, and a plurality
of fins secured to the external surfaces of the heat transfer tubes
and arranged perpendicular to the tube to extend outwardly
therefrom. The first working fluid flows inside the heat transfer
tubes, and air flows through a passage defined between the adjacent
fins and at right angles to the axis of each heat transfer tube.
The blower is placed co-axial with the helicoid's axis to further
enhance the heat exchange.
Inventors: |
Fakheri; Ahmad; (Peoria,
IL) |
Correspondence
Address: |
HUSCH & EPPENBERGER, LLC
190 CARONDELET PLAZA
SUITE 600
ST. LOUIS
MO
63105-3441
US
|
Family ID: |
38117569 |
Appl. No.: |
11/699779 |
Filed: |
January 30, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10748636 |
Dec 30, 2003 |
|
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11699779 |
Jan 30, 2007 |
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Current U.S.
Class: |
165/163 ;
165/152; 165/177 |
Current CPC
Class: |
F28D 1/0472 20130101;
F28F 1/325 20130101; F28D 1/0473 20130101; F28D 1/024 20130101;
F28F 1/022 20130101; F28F 1/32 20130101; F28F 1/126 20130101 |
Class at
Publication: |
165/163 ;
165/152; 165/177 |
International
Class: |
F28D 1/02 20060101
F28D001/02 |
Claims
1. A heat exchanger, comprising: a conduit, said conduit having a
plurality of microchannels; said conduit being a helix configured
to maintain a substantially equivalent distance from a central axis
as it turns through a plurality of loops; a web, said web having a
plurality of bends and said web having a plurality of notches, said
web being disposed between said loops with the plane of said web
being non-parallel to said central axis; and each of said notches
being dimensioned to receive said conduit to form a
thermal-conducting contact.
2. The heat exchanger of claim 1 wherein said conduit is round in
cross section.
3. The heat exchanger of claim 1 wherein said conduit is
rectilinear in cross section.
4. The heat exchanger of claim 1 wherein said notches are at said
bends.
5. The heat exchanger of claim 1 wherein said notches are
intermediate to an inner edge and an outer edge of said web.
6. The heat exchanger of claim 1 wherein a fluid within said
microchannels is hotter than a fluid outside said conduit.
7. The heat exchanger of claim 1 further comprising a blower.
8. The heat exchanger of claim 1 wherein said blower is
cylindrical.
9. The heat exchanger of claim 1 wherein said cylindrical blower is
disposed outside said conduit.
10. A heat exchanger comprising: a conduit having a rectilinear
cross section with a top, a bottom, an inside face and an outside
face; a plurality of microchannels inside said conduit; said
conduit being configured to substantially spiral around a
longitudinal axis, thereby forming a plurality of loops; a
plurality of fins, said fins being non-parallel with said
longitudinal axis, each of said fins having a first
thermal-conducting contact with said bottom of said conduit at one
of said loops and a second thermal-conducting contact with said top
of said conduit at an adjacent loop.
11. The heat exchanger of claim 10 wherein said fins span from said
inside to said outside of said conduit.
12. The heat exchanger of claim 10 wherein each of said fins
contacts a next fin at one of said first or second
thermal-conducting contacts.
13. The heat exchanger of claim 10 wherein each of said fins is a
portion of a continuous web.
14. The heat exchanger of claim 10 wherein said fins comprise an
accordion fold of a continuous web.
15. The heat exchanger of claim 10 wherein a plane of each of said
fins is substantially perpendicular to said longitudinal axis.
16. The heat exchanger of claim 10 further comprising a blower.
17. The heat exchanger of claim 10 wherein said blower is a fan
substantially aligned with said longitudinal axis.
18. The heat exchanger of claim 10 wherein said blower is
cylindrical.
19. The heat exchanger of claim 18 wherein said cylindrical blower
surrounds said conduit.
20. The heat exchanger of claim 10 further comprising a second
conduit.
21. The heat exchanger of claim 10 wherein said second conduit has
a plurality of loops alternating with said conduit and said
plurality of fins traverse a first thermal-conducting contact with
a top or bottom of said conduit and a second thermal-conducting
contact with a bottom or a top of said second conduit.
22. The heat exchanger of claim 20 wherein said second conduit is
substantially parallel to and spaced radially from said conduit.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of United States Patent
Application No. 10/748,636 filed on Dec. 30, 2003.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
[0002] Not Applicable.
APPENDIX
[0003] Not Applicable.
BACKGROUND OF THE INVENTION
[0004] 1. Field of The Invention
[0005] The present invention relates generally to the field of heat
exchangers and, more particularly, to a heat exchanger having
helical coils whose performance is improved by the addition of
fins.
[0006] 2. Related Art
[0007] Heat exchangers are used to transfer heat between fluids.
Many different designs accomplish this, invariably by relying on
the basic thermodynamic principle that heat is transferred from a
warmer body to a cooler one. One of the more commonly used types of
heat exchangers is a fin and tube heat exchanger, such as the
evaporator or condenser of a common air conditioner. Separate fin
strips are arranged in an array with holes in each to receive
perpendicular tubing. One of the working fluids flows through the
tubes and a second fluid (such as air) flows on the outside over
the fins and tubes. Although fin and tube heat exchangers provide
good thermal contact between the cross-fins and the tubing, a
shortcoming is that the tubing must be inserted in sections and the
sections interconnected at the ends by return bends which are
soldered or otherwise connected to the tube sections. The return
bends force the first fluid to turn 180 degrees in each pass
thereby causing an excessive pressure drop in the first fluid.
[0008] To force the second fluid, which in many cases is air,
through the fin spaces and externally across the tubing sections, a
fan structure is typically employed. Due to the placement of the
fan structure relative to the coil, and because the fans are
circular and the heat exchangers rectangular and the respective
different areas thereof, it is common for the air velocities to
vary substantially over the face of the heat exchanger. This
non-uniform air velocity through different portions of the coil
often creates a variety of operational problems and inefficiencies
in which the coil is incorporated, leading to a lowering the
overall heat exchange capability of the coil.
[0009] An example of known heat exchangers is provided by U.S. Pat.
No. 1,785,159 wherein thin ribbons or strips of metal are secured
to the outside surface of a pipe to provide it with integral ribs
or fins. The pipe is formed into a helical coil. In such heat
exchangers, the coil loop radial spacing is limited by the
dimensions of the fin which will prevent close spacing of the
loops. They also limit the types of fin material that can be used.
High pressure applications also are problematic because in known
heat exchangers the fins do not strengthen the heat exchanger and,
thus, service life is adversely affected.
[0010] Further areas of applicability of the present invention will
become apparent from the detailed description provided hereinafter.
It should be understood that the detailed description and specific
examples, while indicating the preferred embodiment of the
invention, are intended for purposes of illustration only and are
not intended to limit the scope of the invention.
SUMMARY OF THE INVENTION
[0011] It is in view of the above problems that the present
invention was developed. The invention is a heat exchanger having a
plurality of heat transfer tubes arranged substantially in the
shape of a helicoidal tube with the individual coils running
parallel to one another in a spiral pattern. A plurality of fins
are secured to the external surfaces of the heat transfer tubes and
extend away therefrom. The first working fluid flows inside the
heat transfer tubes, and the second working fluid, typically air,
flows through the passages between the adjacent fins and tubes. To
further enhance the exchange of thermal energy between the fluids,
a blower may be placed inside the coil cavity or around the coil,
with blower's blades being parallel to the central coil axis.
[0012] The invention incorporates characteristics of high fin
density, close coil spacing, and non-uniform fin size. The
attachment of the fins to at least two adjacent loops not only
enhances the rate of heat transfer, but also provides for enhanced
structural strength that allows the use of this design for
applications where the first heat exchanging fluid is at elevated
pressures. These characteristics and the absence of 180 degree
bends result in a significantly more compact heat exchanger having
superior heat transfer characteristics.
[0013] Further features and advantages of the present invention, as
well as the structure and operation of various embodiments of the
present invention, are described in detail below with reference to
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The present invention will become more fully understood from
the detailed description and the accompanying drawings,
wherein:
[0015] The accompanying drawings, which are incorporated in and
form a part of the specification, illustrate the embodiments of the
present invention and together with the description, serve to
explain the principles of the invention. In the drawings:
[0016] FIGS. 1a-1c illustrate three views of a finned helicoidal
heat exchanger with plane straight fin;
[0017] FIGS. 2a-2d illustrate alternative embodiments of the fins
attached to the helicoidal tube;
[0018] FIGS. 3a-3c illustrate the finned helicoidal heat exchanger
with folded fins;
[0019] FIG. 4 illustrates alternative embodiments of tube cross
sections;
[0020] FIGS. 5a-5c illustrate a finned helicoidal heat exchanger
with a rectangular cross section tube;
[0021] FIG. 6 illustrates a tube cross-section having
microchannels;
[0022] FIG. 7 illustrates in a top view alternative embodiments of
the helicoidal heat exchanger;
[0023] FIGS. 8a-8d illustrate a finned helicoidal heat exchanger
having a blower; and
[0024] FIGS. 9a-9b illustrate two alternative arrangements of a
multi-coil finned helicoidal heat exchanger.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0025] The following description of the preferred embodiment(s) is
merely exemplary in nature and is in no way intended to limit the
invention, its application, or uses.
[0026] The embodiments disclosed below are not intended to be
exhaustive or limit the invention to the precise forms disclosed
below. Rather, the embodiments are chosen and described so that
others skilled in the art may utilize their teachings.
[0027] Referring to the accompanying drawings in which like
reference numbers indicate like elements, FIGS 1a-1c illustrate a
finned helicoidal heat exchanger 20. The helicoidal heat exchanger
20 includes a heat transfer tube 22 arranged substantially in the
shape of a continuous helicoidal tube. The helicoidal heat
exchanger 20 also includes a fin 21 secured to the external
surfaces of the heat transfer tube 22. FIGS 1a-1c illustrate an
embodiment having a plurality of evenly spaced fins 21A, 21B
secured to the external surfaces of the heat transfer tube 22 and
extending outwardly therefrom. The heat transfer tube 22 has a
pitch. The pitch of a helical or helicoidal shape is generally
defined as the distance from any point on the loop of a helix
thread or strand to the corresponding point on the next adjacent
loop of the same thread or strand, measured parallel to the axis
and on the same side of the axis.
[0028] A helix can be a single thread (as illustrated in FIGS. 1-3
or as in U.S. Pat. No. 1,785,159) or can be a double strand helix
(as illustrated in FIG. 9 or as in a DNA strand) or it can be a
multi strand helix. The strands may be placed in line where the
inside strand and outside strand have the same pitch and have the
same tube diameter but the inner strand has smaller coil diameter
compared to the outer strand. In this inline arrangement, the each
individual loop of the inner strand and the corresponding loop of
the outer strand are essentially in a horizontal plane as shown in
FIG. 9b. The strands may also be arranged inline in a vertical
plane as shown in FIG. 9a. The strands may also be arranged in a
staggered arrangements, in-between the above two limits, where the
strands (two or more) may have different pitch, different coil and
tube diameters.
[0029] In the present invention, each of the heat exchanger tubes
or each strand is a continuous conduit formed in a helicoidal shape
with a number of adjacent loops (22A, 24A, & 32A, 32B &
42A, 42B, & 22A, 22B). Each loop is connected to some or all
the other loops through the fins. In the preferred embodiment, each
loop has an interval space (22C, 32C, 42C) with the adjacent loop,
regardless whether there is a single or multiple strands in the
helix. However, for the present invention, there does not need to
be a space between adjacent loops, i.e., each tube section could
actually be in contact with the other adjacent tube sections as
well as being connected by the fins.
[0030] While in the depicted embodiment of FIGS 1a-1c illustrate a
single strand or heat transfer tube 22, some embodiments may have
more than one heat transfer tube. For example, the finned heat
exchanger 20 may include several individual helicoidal strands
running parallel to one another in a spiral pattern as shown in
FIGS. 9a and 9b. Each fin 21 includes a plurality of openings 23
corresponding to the number of loops in tube 22. The tube 22 passes
through the fins' openings 23. While in the depicted embodiment the
openings are through-holes, depending on the application and tube
cross section, they may also be slots, grooves or notches. The fins
21 are connected to the tube 22 and may be affixed to the tube 22
such as by welding, soldering, brazing, chemically attaching, or by
expanding the tubes 22 using a variety of commonly used methods. A
first working fluid flows inside the heat transfer tube 22, and a
second working fluid, typically air, flows through a passage
defined by the adjacent fins 21 and the tube 22. For example, the
air may flow radially, axially or a combination of the two through
the passage.
[0031] The fins 21 can be plain as shown in the example of FIGS
1a-1c. They can also assume the configuration of the any of the
commonly used types in heat exchangers such as perforated,
louvered, slotted, wavy, spine etc. The fins 21 can be continuous
as shown in FIGS. 1a-2c, or can be segmented as shown in FIG. 2d
where fin segments 21' are attached to the helicoidal tubes at an
arbitrary angle 28 relative to the tube 22. Some or all of the fin
segments 21' may connect with one another to form continuous fins
21 or may be left segmented.
[0032] The tube outer surface can also be plain as shown in the
examples of FIGS 1a-2d or can also be formed in the configuration
of the any of the commonly employed tube enhancements methods such
as grooved or dimpled. The inside surface of the tube can also be
plain or altered using any of the commonly used methods to enhance
the inside rate of heat transfer such as grooved, dimpled, or
inserting twisted tape turbulators.
[0033] FIGS. 3a-3c show three views of a helicoidal heat exchanger
having a tube 32 and enhanced with folded fins 31. The folded fins
31 are formed by folding a first sheet of a heat conductive
material back and forth on itself to provide accordion-like folds.
The folded fins 31 have openings, such as slots or holes, cut
through them at the folds or below to allow the fins to fit onto
the tubes and be attached to the tubes 32 using any one of the
aforementioned methods. The embodiments of FIGS. 3a-3c can further
be modified by replacing the triangular pattern of fins with
rectangular, or other fin arrangement profiles. The fins shown in
FIGS. 3 are continuous. They can also be segmented, i.e. the fins
may be cut along their fold line, similar to the fins shown in FIG.
2d, which can then be arranged between the adjacent loops in any
pattern.
[0034] Another category of modifications is the changing of the
shape of the tube cross-section. The tubes shown in FIGS 1a-3c have
circular cross sections. Other tube cross sections, typically used
in heat exchanger manufacturing like flat tubes, lenticular,
square, rectangular, triangular, or elliptical channels or any
other cross section, some of which are shown in FIG. 4, can replace
the tubes shown in the drawings. For example, the tube may be
circular 40A, lenticular 40B, elliptical 40C, square 40D,
rectangular 40E, or triangular 40F.
[0035] FIGS. 5a-5c show a helicoidally finned heat exchanger made
with a helicodal pipe 42 having rectangular cross section and
enhanced with fanfold fins 31. In the depicted embodiment, the
helicoidal pipe 42 forms a first winding and the fins 31 form a
second winding. As stated above, the fin arrangement shown is one
of the many that can be used.
[0036] Another embodiment is a finned helicoidal microchannel heat
exchanger. Microchannel heat exchangers use channel widths of 10 to
1,000 .mu.m. In microchannel heat exchangers the heat transfer
coefficients are very high and therefore relatively short flow
passages required, causing the pressure drop to be small. The small
size of the individual channels allow the placement of many flow
passages in parallel in a small device. FIG. 6, shows the cross
section of the pipe 42 of the finned helicoidal microchannel heat
exchanger as shown in FIG 5. The cross-section illustrates the
microchannels 60. Again, the microchannels do not need to be
circular, and can have any cross sections, including those shown in
FIG. 4. They also can be arranged in a parallel horizontal
arrangement as shown in FIG. 7, or in a vertical arrangement of in
a staggered manner anywhere in between.
[0037] As shown in FIGS 1c, 3c, and 5c the top view of all the
above embodiments of the invention is a circle since the helical
coils are formed in that shape. The circular coil shape represents
one of the possible configurations and the invention is not limited
to just the circular cross section as the coil cross section can be
in any other form, as some additional possibilities are shown in
FIG. 7. For example, the coil shape may be rectangular 70A,
elliptical 70B, or triangular 70C.
[0038] Another improvement made to the helicoidally finned heat
exchangers is the incorporation of a blower 51, shown in FIGS.
8a-8d. The blower 51 can either be placed in the hollow core 25 as
shown in FIG. 8c or around the outside of the coil as shown in FIG.
8d. Addition of the blower enhances the velocity of the second heat
exchanging fluid and thus the overall rate of heat transfer,
without requiring much extra space. Hence, the second working fluid
can be forced by the blower axially along the fins or radially in
the core 25 or a combination of the two.
[0039] FIGS. 9a and 9b show two configurations of a double pipe
(strand) helicoidal heat exchanger. In the embodiment of FIG. 9a,
the fins are removed to show its essential features. In a pipe, two
helicoidal coils, 22 and 24 run parallel to one another. The number
of parallel coils can be as many as required and the arrangements
are not limited to the two shown. In FIG. 9a, the tubes (strands)
22A and 24A have the same coil diameter and the same pitch,
although they don't have to have the same tube diameter and are
intertwined, and arranged in the same vertical plane. In FIG. 9b,
the tubes (strands) 24B have different coil diameters, i.e. strand
24A has a smaller coil diameter than tube 22B. In the case shown in
FIG. 9b, the strands have the same pitch and therefore the loops
are in line, or essentially on the same plane which is almost
horizontal. The other embodiments include multiple coils that have
different coil and/or tube diameters or pitch that are arranged in
staggered and/or inline arrangement. The tubes 22, 24 are
operatively connected by a header 26.
[0040] Referring to FIG. 1a, in operation, a first working fluid
(not shown) flows into the tube 22 at an inlet. The first working
fluid flows through the tube 22 and heats (or cools) the tube 22
and the fins 21. A second working fluid (not shown), air for
example, flows over and between the fins 21 to cool (heat) the fins
and the tubes and therefore the first fluid. If the first working
fluid is the warmer fluid, the heat will be transferred from the
inner wall towards the outer wall of the tube 22. The fins 21
conduct heat away from the outer surface of tube 22 and transfer
the heat to the second working fluid. For increased efficiency, the
second working fluid may be forced over and between the fins 21. In
the depicted embodiment of FIG. 8C, a blower apparatus forces the
second working fluid from a central axis of the tube outwardly and
past the fins 21. The first working fluid cools as it flows through
the tube 22. The first working fluids exits the tube 22 at an
outlet.
[0041] In view of the foregoing, it will be seen that the several
advantages of the invention are achieved and attained. The
embodiments were chosen and described in order to best explain the
principles of the invention and its practical application to
thereby enable others skilled in the art to best utilize the
invention in various embodiments and with various modifications as
are suited to the particular use contemplated.
[0042] As various modifications could be made in the constructions
and methods herein described and illustrated without departing from
the scope of the invention, it is intended that all matter
contained in the foregoing description or shown in the accompanying
drawings shall be interpreted as illustrative rather than limiting.
For example, while the cross-section of the helicoidal tube is
shown as circular, the cross-section could also be a flat tube,
lenticular, square, rectangular, triangular, or elliptical. Thus,
the breadth and scope of the present invention should not be
limited by any of the above-described exemplary embodiments, but
should be defined only in accordance with the following claims
appended hereto and their equivalents.
[0043] As various modifications could be made to the exemplary
embodiments, as described above with reference to the corresponding
illustrations, without departing from the scope of the invention,
it is intended that all matter contained in the foregoing
description and shown in the accompanying drawings shall be
interpreted as illustrative rather than limiting. Thus, the breadth
and scope of the present invention should not be limited by any of
the above-described exemplary embodiments, but should be defined
only in accordance with the following claims appended hereto and
their equivalents.
* * * * *