U.S. patent application number 13/395742 was filed with the patent office on 2012-09-13 for free-draining finned surface architecture for heat exchanger.
This patent application is currently assigned to CARRIER CORPORATION. Invention is credited to Abbas A. Alahyari, Satyam Bendapudi, Jack Leon Esformes, Mikhail B. Gorbounov, Arindom Joardar, Sunil S. Mehendale, Michael F. Taras.
Application Number | 20120227945 13/395742 |
Document ID | / |
Family ID | 43758953 |
Filed Date | 2012-09-13 |
United States Patent
Application |
20120227945 |
Kind Code |
A1 |
Taras; Michael F. ; et
al. |
September 13, 2012 |
FREE-DRAINING FINNED SURFACE ARCHITECTURE FOR HEAT EXCHANGER
Abstract
A free-draining heat exchanger includes a first heat exchange
tube, a second heat exchange tube spaced from and generally
parallel to the first heat exchange tube, and a fin contacting the
first and second heat exchange tubes. The fin includes a louver and
at least one drainage enhancement feature for promoting removal of
liquid from external surfaces of the heat exchanger. A
free-draining fin structure includes an array of fins disposed
between adjacent heat exchange tubes for improving water drainage
by reducing liquid surface tension. Each fin in the array includes
an opening and a louver for directing airflow through the opening
and around the fin and at least one drainage enhancement
feature.
Inventors: |
Taras; Michael F.;
(Fayetteville, NY) ; Esformes; Jack Leon;
(Jamesville, NY) ; Mehendale; Sunil S.; (Manlius,
NY) ; Bendapudi; Satyam; (Fayetteville, NY) ;
Alahyari; Abbas A.; (Manchester, CT) ; Joardar;
Arindom; (East Syracuse, NY) ; Gorbounov; Mikhail
B.; (South Windsor, CT) |
Assignee: |
CARRIER CORPORATION
Farmington
CT
|
Family ID: |
43758953 |
Appl. No.: |
13/395742 |
Filed: |
March 31, 2010 |
PCT Filed: |
March 31, 2010 |
PCT NO: |
PCT/US2010/029416 |
371 Date: |
May 23, 2012 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61243064 |
Sep 16, 2009 |
|
|
|
Current U.S.
Class: |
165/172 ;
165/185 |
Current CPC
Class: |
F28F 2265/06 20130101;
F28F 17/005 20130101; F28D 1/05391 20130101; F28F 2265/22 20130101;
F28F 1/128 20130101 |
Class at
Publication: |
165/172 ;
165/185 |
International
Class: |
F28F 17/00 20060101
F28F017/00; F28F 7/00 20060101 F28F007/00; F28F 1/10 20060101
F28F001/10 |
Claims
1. A free-draining heat exchanger comprising: a first heat exchange
tube; a second heat exchange tube spaced from and generally
parallel to the first heat exchange tube; and a fin contacting the
first and second heat exchange tubes, the fin comprising: a louver;
at least one drainage enhancement feature for promoting removal of
liquid from external surfaces of the heat exchanger.
2. The free-draining heat exchanger of claim 1, wherein the at
least one drainage enhancement feature is selected from the group
consisting of a louver angle greater than 45.degree., a notch, an
overhanging edge, a descending lip, a curvature, an angle, a
rotated fin structure and combinations thereof.
3. The free-draining heat exchanger of claim 1, wherein the louver
has a louver angle between 45.degree. and about 75.degree..
4. The free-draining heat exchanger of claim 1, wherein the first
heat exchange tube comprises a first lateral edge, and wherein the
fin further comprises: a first overhanging edge extending beyond
the first lateral edge of the first heat exchange tube.
5. The free-draining heat exchanger of claim 4, wherein the first
overhanging edge extends beyond the first lateral edge of the first
heat exchange tube by a distance between about 3 mm and about 10
mm.
6. The free-draining heat exchanger of claim 4, wherein the fin
further comprises: a first descending lip extending from the first
overhanging edge.
7. The free-draining heat exchanger of claim 6, wherein the first
descending lip comprises a cross-section selected from the group
consisting of rectangular, trapezoidal, triangular, curved and
combinations thereof.
8. The free-draining heat exchanger of claim 6, further comprising:
a third heat exchange tube; and a second fin contacting the second
and third heat exchange tubes, the second fin comprising: a second
overhanging edge extending beyond the first lateral edge of the
first heat exchange tube; and a second descending lip extending
from the second overhanging edge, wherein a portion of the first
descending lip overlaps with a portion of the second descending
lip.
9. The free-draining heat exchanger of claim 6, further comprising:
a third heat exchange tube; and a second fin contacting the second
and third heat exchange tubes, the second fin comprising: a second
overhanging edge extending beyond the first lateral edge of the
first heat exchange tube; and a second descending lip extending
from the second overhanging edge, wherein the second descending lip
is spaced from the first descending lip by a gap.
10. The free-draining heat exchanger of claim 1, wherein the first
heat exchange tube comprises a first lateral edge and a second
lateral edge on an opposite side of the first heat exchange tube,
and wherein the fin further comprises: a first overhanging edge
extending beyond the first lateral edge of the first heat exchange
tube; and a second overhanging edge extending beyond the second
lateral edge of the first heat exchange tube.
11. The free-draining heat exchanger of claim 10, wherein the first
overhanging edge extends beyond the first lateral edge of the first
heat exchange tube farther than the second overhanging edge extends
beyond the second lateral edge of the first heat exchange tube.
12. The free-draining heat exchanger of claim 10, wherein the fin
further comprises: a first descending lip extending from the first
overhanging edge; and a second descending lip extending from the
second overhanging edge.
13. The free-draining heat exchanger of claim 1, further
comprising: a second fin contacting the first and second heat
exchange tubes; and a parallel portion connecting the fin and the
second fin and substantially parallel to and contacting one of the
first or second heat exchange tubes.
14. The free-draining heat exchanger of claim 13, wherein the fin,
the second fin and the parallel portion are formed from a
continuous piece of material.
15. The free-draining heat exchanger of claim 13, wherein the
parallel portion forms a sharp corner with the fin to reduce liquid
surface tension.
16. The free-draining heat exchanger of claim 13, wherein the fin
comprises a notch on the fin adjacent the parallel portion.
17. The free-draining heat exchanger of claim 16, wherein the notch
spans an edge of the fin.
18. The free-draining heat exchanger of claim 16, wherein the notch
spans an area of the fin between but not including edges of the
fin.
19. The free-draining heat exchanger of claim 16, wherein the notch
comprises a cross-section selected from the group consisting of
oval, rectangular, trapezoidal, triangular, elliptical, racetrack
and combinations thereof.
20. The free-draining heat exchanger of claim 16, wherein the fin
comprises between about one notch and about five notches, and
wherein each notch has a length between about 3 mm and about 32 mm
and a height between about 1 mm and about 5 mm.
21. The free-draining heat exchanger of claim 14, wherein the fin
further comprises a first overhanging edge extending beyond a first
lateral edge of the first heat exchange tube, and wherein the
second fin comprises a second overhanging edge extending beyond the
first lateral edge of the first heat exchange tube, and wherein the
parallel portion comprises a third overhanging edge extending
beyond the first lateral edge of the first heat exchange tube.
22. The free-draining heat exchanger of claim 21, wherein the third
overhanging edge comprises a notch.
23. The free-draining heat exchanger of claim 21, further
comprising: a notch located at an intersection of the first and
third overhanging edges.
24. The free-draining heat exchanger of claim 21, wherein the first
overhanging edge is separated from the fin and bent downward to
form a descending lip adjacent the second fin.
25. The free-draining heat exchanger of claim 1, wherein the fin
has a curvature.
26. The free-draining heat exchanger of claim 25, wherein the fin
comprises a notch adjacent the first or second heat exchange
tube.
27. The free-draining heat exchanger of claim 1, wherein the fin
comprises: a first fin segment; and a second fin segment connected
to the first fin segment, wherein the first fin segment and the
second fin segment form an angle between about 100.degree. and
about 170.degree..
28. The free-draining heat exchanger of claim 27, wherein the first
fin segment comprises a notch adjacent the first or second heat
exchange tube.
29. The free-draining heat exchanger of claim 1, further
comprising: a plurality of fins contacting the first and second
heat exchange tubes, wherein adjacent fins are connected to form a
corrugated pattern along a longitudinal axis of the first and
second heat exchange tubes.
30. A free-draining fin structure comprising: an array of fins
disposed between adjacent heat exchange tubes for providing
enhanced water drainage by reducing liquid surface tension, each
fin in the array of fins comprising: an opening; a louver for
directing airflow through the opening and around the fin; and at
least one drainage enhancement feature.
31. The free-draining fin structure of claim 30, wherein the at
least one drainage enhancement feature is selected from the group
consisting of a louver angle greater than 45.degree., a notch, a
sharp corner, an overhanging edge, a descending lip, a curvature,
an angle, a rotated fin structure and combinations thereof.
32. The free-draining fin structure of claim 30, further
comprising: a parallel portion connecting adjacent fins in the
array for engaging with a heat exchange tube.
33. The free-draining fin structure of claim 30, wherein the louver
has a louver angle greater than 45.degree..
Description
BACKGROUND
[0001] Aluminum microchannel heat exchangers offer several
advantages over the once conventional copper-aluminum or
copper-copper round tube plate fin heat exchangers and are used in
a variety of applications. However, aluminum microchannel heat
exchangers also present new challenges, with effective condensate
drainage being one of them. Condensation that forms on heat
exchanger surfaces during operation or water collected during an
off-cycle can be retained within the fin and tube heat exchanger
aluminum core for prolonged periods of time. This problem is
compounded when the heat exchanger is used in outdoor industrial,
coastal or marine environments, especially where exposure to high
humidity levels, frequent rains and winds carrying ocean/sea water
can occur. Water retention on the aluminum surfaces of the heat
exchangers can lead to accelerated corrosion of the surfaces and,
eventually, perforation of critical components, such as heat
exchange tubes and manifolds, as well as compromising joints
between heat exchange tubes and heat transfer fins.
[0002] Until now, drainage improvements for aluminum microchannel
heat exchangers were specifically aimed at evaporators for air
conditioning and heat pump applications where fin spacing is
relatively wide and only modest amounts of condensate need to be
continually removed. These improvements normally did not benefit
aluminum microchannel condensers, which generally have closer fin
spacing that allows for larger amounts of water to be accumulated
within the heat exchanger matrix and impedes condensate drainage.
Aluminum microchannel condensers can also become flooded due to the
accumulation of environmental water or condensation during
off-cycle periods, resulting in extended periods of exposure to
water. Thus, these condensers generally have a significantly larger
amount of retained water that needs to be removed (and require a
corresponding higher rate of condensate or environmental water
removal) than evaporators.
SUMMARY
[0003] A free-draining heat exchanger includes a first heat
exchange tube, a second heat exchange tube and a fin structure. The
second heat exchange tube is spaced from and generally parallel to
the first heat exchange tube. The fin structure includes a fin
contacting the first heat exchange tube and the second heat
exchange tube for promoting removal of liquid from external
surfaces of the heat exchanger.
[0004] A free-draining fin structure includes an array of fins
disposed between adjacent heat exchange tubes for providing
enhanced water drainage by reducing liquid surface tension. Each
fin in the array includes an opening and a louver for directing
airflow through the opening and around the fin and the louver.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 is a front view of a microchannel heat exchanger.
[0006] FIG. 2 is a perspective view of one embodiment of a fin.
[0007] FIG. 3 is a front view of heat exchange tubes and a fin
structure.
[0008] FIG. 4 is a perspective view of the heat exchange tubes and
fin structure of FIG. 3.
[0009] FIG. 5 is a cross section view of a fin structure with an
overhanging fin.
[0010] FIG. 5A is a perspective view of a fin structure with
notched overhanging fins.
[0011] FIG. 6 is a cross section view of a fin structure with an
overhanging fin and a lip.
[0012] FIG. 6A is a perspective view of a fin structure with
overhanging fins and lips.
[0013] FIG. 7 is a cross section view of a fin structure with an
overhanging fin and two lips.
[0014] FIG. 8 is a perspective view of a heat exchange tube with a
curved fin.
[0015] FIG. 9 is a perspective view of a heat exchange tube with an
angled fin.
[0016] FIG. 10A is a partial perspective view of a microchannel
heat exchanger with vertical heat exchange tubes and a rotated fin
structure.
[0017] FIG. 10B is an exploded view of the rotated fin structure of
FIG. 10A.
DETAILED DESCRIPTION
[0018] The present invention describes fin structures having
louvers and drainage enhancement features that provide for improved
liquid drainage in heat exchangers. The fin structures allow water
to drain more easily and improve the removal of water from heat
exchanger external surfaces. The fin structures work with any type
of tube-fin heat exchanger and are particularly useful for aluminum
microchannel heat exchangers, especially aluminum microchannel
condensers. While specific embodiments are described with reference
to aluminum microchannel heat exchangers, the invention can also
provide benefits to other tube-fin heat exchangers. Aluminum
microchannel heat exchangers typically have a more compact
structure than other heat exchangers. Typical fin spacing varies
between about 5.5 fins per cm (14 fins per inch) and about 9.1 fins
per cm (23 fins per inch) and typical heat exchange tube spacing
varies between about 0.5 cm (0.19 inches) and about 1.0 cm (0.39
inches). Due to this tight fin and tube spacing combined with the
aluminum construction, water removal is critically important for
aluminum microchannel heat exchangers.
[0019] FIG. 1 illustrates one example of an aluminum microchannel
heat exchanger. Heat exchanger 20 can be aluminum or an aluminum
alloy and includes first manifold 22 having inlet 24 for receiving
a working fluid, such as coolant or refrigerant, and outlet 26 for
discharging the working fluid. First manifold 22 is fluidly
connected to each of a plurality of heat exchange tubes 28 that are
each fluidly connected on an opposite end with second manifold 30.
Second manifold 30 is fluidly connected with each of a plurality of
heat exchange tubes 32 that return the working fluid to first
manifold 22 for discharge through outlet 26. Heat exchange tubes 28
and 32 each typically include flow channels or passages, so-called
microchannels or minichannels (not shown), for conveying the
working fluid. The structures of heat exchange tubes 28 and 32 are
essentially identical; only the direction of working fluid flow
differs. Reference is made in this application generally to heat
exchange tubes 28 to demonstrate the concepts of the invention. The
same concepts can be equally applied to heat exchange tubes 32.
Partition 23 is located within first manifold 22 to separate inlet
and outlet sections of first manifold 22. The two-pass working
fluid flow configuration described above is only one of many
possible design arrangements. Single and other multi-pass fluid
flow configurations can be obtained by placing partitions 23, inlet
24 and outlet 26 at specific locations within first manifold 22 and
second manifold 30. Various other working fluid flow configurations
are possible, but are not critical to understanding the present
invention. Fins 34 extend between heat exchange tubes 28 as shown
in FIG. 1. Fins 34 support heat exchange tubes 28 and establish
open flow channels between the heat exchange tubes 28 (e.g., for
airflow). Fins 34 are mechanically and/or chemically and/or
thermally joined to heat exchange tubes 28. Multiple fins 34 can be
connected together to form one continuous fin structure 36. Fins 34
can have louvers for flow re-direction and heat transfer
enhancement.
[0020] According to the present invention, fins 34 and fin
structures 36 are arranged to improve and optimize water drainage
aspects for heat exchanger 20. Fins 34 and fin structures 36 affect
the operation of heat exchanger 20 in three primary ways. First,
fins 34 and fin structures 36 aid in heat transfer between the
working fluid flowing within heat exchange tubes 28 and the air
passing over heat exchange tubes 28 and fins 34 through heat
exchanger 20 in the spaces between adjacent heat exchange tubes 28.
Second, fins 34 and fin structures 36 affect the pressure drop
across heat exchanger 20. The pressure drop reduces airflow through
and around heat exchanger 20, subsequently having a negative impact
on heat transfer. Third, fins 34 and fin structures 36 provide for
water drainage. Fins 34 and fin structures 36 are arranged to
prevent water from being retained by the aluminum surfaces of heat
exchanger 20 and to allow water to effectively drain from the
outside surfaces of heat exchanger 20. Therefore, fins 34 and fin
structures 36, by providing efficient drainage characteristics,
reduce water retention within fin structures 36 and diminish the
pressure drop effect on performance of heat exchanger 20. Fins used
in prior art heat exchangers were generally optimized only for
pressure drop and heat transfer considerations. However, fins 34
and fin structures 36 provide improved water drainage for heat
exchanger 20 without significantly compromising pressure drop and
heat transfer characteristics or the performance of heat exchanger
20.
[0021] FIG. 2 illustrates a partial perspective view of one
embodiment of fin 34. Fin 34 can be aluminum or an aluminum alloy.
Fin 34 includes fin body 38, louvers 40 and louver openings 42. As
shown in FIG. 2, fin body 38 is generally planar and rectangular in
shape. In other embodiments, fin body 38 can be curved or segmented
with different portions being angled. Examples of curved and angled
fin bodies 38 are described in further detail below. Fin body 38
extends longitudinally to form first portion 44 and second portion
46 of fin 34.
[0022] As illustrated in FIG. 2, fin 34 includes first louvers 40a
associated with first portion 44 and second louvers 40b associated
with second portion 46. Louvers 40 create louver openings 42 within
fin body 38 to provide drainage paths for directing water away from
the aluminum surfaces of fin 34, and heat exchanger 20 in general.
As shown in FIG. 2, louvers 40 are angled away from fin body 38,
creating louver openings 42. In this illustration, both sets of
louvers 40 (40a and 40b) are angled so that they open away from the
center of fin body 38. Louvers 40 can also be arranged so that they
are angled and open in a single direction, towards the leading edge
of fin 34 or away from the leading edge of fin 34, or angled so
that they open towards the center of fin body 38. During operation
of heat exchanger 20, air typically flows around fins 34 and
louvers 40 and through louver openings 42 to enhance heat transfer
between fins 34 and the airflow passing through heat exchanger 20.
Louvers 40 direct air flowing along the surface of fin body 38 to
and through louver openings 42. The flow of air through heat
exchanger 20 aids in the removal of environmental water or
condensate from the external aluminum surfaces of heat exchanger 20
by directing water through and away from heat exchanger 20. Fins 34
and fin structures 36 also contain at least one drainage
enhancement feature to provide improved water drainage with reduced
or no airflow through heat exchanger 20. The various drainage
enhancement features can include louver angles greater than about
50.degree., notches, overhanging edges, descending lips,
curvatures, angles and combinations thereof and are described in
greater detail below.
[0023] Louvers 40 can extend outwardly from fin body 38 at
relatively large louver angles (measured between the plane of
louver 40 and the plane of fin body 38). Louver angles suitable for
providing adequate drainage in wet environments can be between
about 45.degree. and about 75.degree., with louver angles of about
50.degree. to about 60.degree. being particularly suitable as a
drainage enhancement feature. Fins 34 with relatively large louver
angles are suitable for use with heat exchange tubes 28, whether
heat exchange tubes 28 are arranged horizontally, vertically or in
any position in between vertical and horizontal orientation.
Louvers 40, and thereby louver openings 42, generally have a width
of about 0.5 mm (0.0197 inches) to about 1.8 mm (0.071 inches) and
a height of about 2 mm to about 10 mm (0.0787 inches to 0.394
inches). Consecutive louvers 40 are generally spaced about 0.7 mm
(0.0276 inches) to about 2 mm (0.0787 inches) apart on fin 34. The
relatively large louver angles and widths of louver openings 42
improve drainage capabilities of fin 34. Because the louver angle
is relatively large, condensate and other water present on the
surfaces of fin 34 more readily flows away from the fin surface.
The flow of water is aided by gravity and any airflow passing
around and through louver openings 42. The relatively large louver
angle significantly reduces the potential water surface tension
interactions along fin 34, thereby discouraging water retention on
the fin surface. Due to the lower surface tension, gravity alone
provides a force substantial enough to facilitate water drainage
from louvers 40 and fin 34. Depending on the orientation of fin 34,
water can drain from a first fin 34 to a second, lower fin 34 or to
lower heat exchange tube 28 for subsequent removal by gravity
and/or airflow. Airflow further increases drainage by directing
water along fin body 38 towards downstream louvers 40 and louver
openings 42 and onto the external surfaces of heat exchange tubes
28.
[0024] Multiple fins 34 can be connected together to form fin
structure 36. FIG. 1 illustrates continuous fin structure 36
composed of a plurality of fins 34 connected together in a
corrugated fashion. Fins 34 are arranged in a repeating alternating
V pattern. Fin structure 36 can be constructed from a single piece
of material to have a plurality of fins 34 and shaped to fit
between heat exchange tubes 28. Such a continuous fin structure 36
can be constructed and positioned in place between heat exchange
tubes 28 and mechanically or chemically attached (e.g., welded,
brazed, soldered or glued) to heat exchange tubes 28 at one or more
locations. Alternatively, individual fins 34 can be connected to
heat exchange tubes 28 or connected to other fins 34 by similar
techniques (welding, brazing, soldering, etc.).
[0025] FIGS. 3 and 4 illustrate continuous fin structure 36 having
surfaces parallel and adjacent to heat exchange tubes 28 between
fins 34 and "sharp" edges near heat exchange tubes 28. In general,
fin structure 36 can have a curved, oval or sinusoidal wave type
shape or the sharp edge type shape. The embodiment illustrated in
FIGS. 3 and 4 provides for reduced surface tension along fin
structure 36 and increased water drainage potential. FIGS. 3 and 4
illustrate fin structure 36 with a series of corrugated geometries.
In this embodiment, fin structure 36 is arranged to form a series
of trapezoidal like shapes with fins 34 and parallel fin structure
portions 50. Between adjacent fins 34, fin structure 36 includes a
series of parallel fin structure portions 50 that run generally
parallel to heat exchange tubes 28. Parallel fin structure portions
50 are arranged with fins 34 within fin structure 36 to form sharp
edges at corners 52 and eliminate the crevices and small spaces
possible between heat exchange tubes 28 and fin structures having
curved, oval or sinusoidal shapes. As shown in FIGS. 3 and 4,
corners 52 formed by the sharp edges of trapezoidal fin structure
36 have an angle that can approach but does not quite reach
90.degree. (i.e. fins 34 are not perpendicular to heat exchange
tubes 28). Other geometries, such as rectangular shapes, can also
be used to form sharp edges at corners 52 near heat exchange tubes
28. When fin structure 36 forms rectangular shapes, fins 34 are
generally perpendicular to heat exchange tubes 28.
[0026] With angles that are close to 90.degree., sharp corners 52
of fin structure 36 eliminate the small spaces present between
curved edges (not shown) of, for instance, sinusoidal fin
structures and heat exchange tubes 28. Those small spaces formed by
curved fin structures allow water surface tension to draw water
into the small spaces where it can accumulate and become difficult
to remove by gravity alone or even with airflow passing through
heat exchanger 20. Sharp corners 52 minimize water entrapment
between fin structure 36 and heat exchange tubes 28. For example,
sharp corner 52a does not allow water to become trapped between fin
34 or parallel fin structure portion 50 and heat exchange tube 28.
The angle of sharp corner 52a is large enough that any water in the
vicinity of sharp corner 52a will run down fin 34 due to gravity
instead of being trapped between fin 34 and heat exchange tube 28.
Since water moves away from sharp corner 52a, it is more easily
removed by airflow directed over heat exchange tubes 28 and through
fin structure 36. Thus, sharp corner 52a provides reduced surface
tension potential that might allow water to not become entrapped.
On the other hand, a curved fin structure provides small spaces
between the top surface of the fin structure and heat exchange tube
28 where water surface tension can entrap water between the top
surface of the fin structure and heat exchange tube 28.
[0027] Similar to sharp corner 52a, sharp corner 52b provides a
large enough angle so that water does not become easily trapped
between fin structure 36 and heat exchange tube 28. Instead of
gravity aiding the removal of water from sharp corner 52b here (for
horizontally aligned heat exchange tubes 28), however, the large
angle between fin 34 and heat exchange tube 28 at sharp corner 52b
allows airflow to direct any water that accumulates in sharp corner
52b along the surface of heat exchange tube 28 until it reaches the
downstream edge (with respect to the airflow) where the water is
removed from heat exchange tube 28. The large angle between fin 34
and heat exchange tube 28 at sharp corner 52b does not restrict the
airflow along sharp corner 52b like smaller spaces would.
[0028] FIG. 4 illustrates a perspective view of heat exchange tubes
28 and fin structure 36 of FIG. 3. FIG. 4 offers a different view
of fin structure 36 with louvers 40 and louver openings 42. In the
embodiment shown, fins 34 and parallel fin structure portions 50 of
fin structure 36 have widths equal to widths of heat exchange tubes
28. In other embodiments, described below in additional detail, the
widths of fins 34 and parallel fin structure portions 50 differ
from the width of heat exchange tubes 28.
[0029] FIG. 4 also illustrates notches 54 incorporated into fin
structure 36. Notches 54 represent areas of fin structure 36 where
a portion of the structure material has been cut out or otherwise
removed from fin structure 36 or a gap, slit or apertures in fin
structure 36 has been created. Notches 54 can be located on fins 34
(as shown in FIG. 4), parallel fin structure portions 50 (as shown
in FIG. 5A) or a combination of the two. When located on fins 34
arranged on horizontal heat exchange tubes 28, notches 54 are
preferably located on bottom portions of fins 34 (to allow water to
move along the surface of heat exchange tubes 28 more freely).
Other heat exchange tube 28 orientations with respect to gravity
(as well as above mentioned horizontal orientation) also permit
positioning notches 54 to be adjacent to both sides of the heat
exchange tube 28. As shown in FIG. 4, notches 54 create openings in
fins 34 where they join heat exchange tube 28. Notches 54a and 54c
are located on lateral edges of fin structure 36. In this case,
notches 54a and 54c are located on fin 34 at first portion 44 and
second portion 46 of fin body 38, respectively. Notch 54b is
located near the center of fin 34. One notch 54 or a combination of
notches 54 can be present to improve water or condensate movement,
and hence, airflow along the surface of heat exchange tube 28. The
exact location of each notch 54, dimensions and numbers of notches
54 depend on a particular fin configuration and size. For typical
microchannel heat exchangers currently employed in the air
conditioning and refrigeration industry, the number of notches 54
could be between 1 and 5. Furthermore, the length of notches 54 can
range between about 3 mm (0.118 inches) and about 32 mm (1.26
inches) and the height of notches 54 can range between about 1 mm
(0.039 inches) and about 5 mm (0.197 inches). Although only
rectangular notch configurations are depicted in FIG. 4, other
notch shapes, such as oval, elliptical, racetrack, trapezoidal and
triangular, are also feasible and within the scope of the
invention.
[0030] Notches 54 further reduce surface tension within fin
structure 36 and improve water drainage. Water is even less likely
to accumulate in sharp corners 52 where notches 54 are located. In
areas where fin 34 has an opening, water does not easily accumulate
as it is in contact with only two surfaces (heat exchange tube 28
and parallel fin structure portion 50) rather than three surfaces
of the prior art configurations (heat exchange tube 28, fin 34, and
parallel fin structure portion 50). Furthermore, notches 54 provide
additional flow paths for airflow passing through fin structure 36
and over heat exchange tubes 28. The additional flow paths allow
the airflow to better direct water away from heat exchange tubes 28
and fin structure 36, thereby improving water drainage.
[0031] FIG. 5 illustrates a cross section of fin structures 36 with
overhanging lateral edges. Fin structure 36 includes fins 34,
louvers 40, louver openings 42, first overhanging edge 60 and
second overhanging edge 62. Fin structure 36 can be a single
continuous piece with parallel fin structure portions 50 or a
series of unconnected fins 34 as described above. Louvers 40,
louver openings 42 and parallel fin structure surfaces 50 function
as described above. Unlike fin structure 36 shown in FIG. 4,
however, fin structure 36 shown in FIG. 5 includes first and second
overhanging edges 60 and 62, respectively, which extend laterally
past the lateral edges of heat exchange tubes 28. By extending the
lateral edges of fin 34 (overhanging edges 60 and 62) past the
lateral edges of heat exchange tubes 28, water drainage from the
fin structure 36 and heat exchange tubes 28 is improved. For
example, water present within fin structure 36 can be directed away
from fin structure 36 without contacting heat exchange tubes 28 by
the airflow passing between heat exchange tubes 28 and fin
structures 36. Water can travel along fins 34 and lower parallel
fin structure portion 50b. By extending past the lateral edges of
heat exchange tubes 28, first and second overhanging edges 60 and
62 allow water to travel along the edge of fin structure 36 without
ever contacting heat exchange tube 28. Once water reaches first or
second overhanging edges 60 or 62 or the lateral edge of lower
parallel fin structure portion 50b, gravity and/or airflow cause
the water to drain downward and in a direction away from heat
exchange tubes 28. This prevents water from collecting along the
surfaces of heat exchange tubes 28 and subsequently causing
corrosion to the surfaces of heat exchange tubes 28. First and
second overhanging edges 60 and 62 can extend beyond lateral edges
of heat exchanger tube 28 by different distances, preferably with
the downstream overhanging edge, with respect to the airflow,
extending a larger distance beyond the lateral edge of heat
exchange tubes 28. If the distance by which both first and second
overhanging edges 60 and 62 extend past the lateral edges of heat
exchange tube 28 is identical, the orientation of heat exchanger
20, with respect to the airflow, is symmetrical, so that any
lateral edge of heat exchange tube 28 can be a leading edge (i.e.
the airflow can pass through heat exchanger 20 in either
direction).
[0032] Furthermore, condensate collected on the outside surfaces of
heat exchange tubes 28 may be drawn to overhanging edges 60 and 62
by surface tension, assisting in condensate retention reduction.
Fin structure 36 may have only one overhanging edge 60, preferably
downstream, with respect to the airflow flowing over heat exchange
tubes 28 and fin structure 36. For currently used microchannel heat
exchangers, the overhand dimension for the fins 34 would typically
be between about 3 mm (0.118 inches) and about 10 mm (0.394
inches). Overhanging edges 60 and 62 can be combined with notches
54 of FIG. 4. FIG. 5A illustrates a perspective view of fins 34
with notched overhanging edges 60. Louvers 40 have been omitted
from FIG. 5A to better illustrate notched overhanging edges 60. It
should be understood that fins 34 with notched overhanging edges 60
can include louvers 40. In one embodiment, notches 54 are located
in the middle of parallel fin structure portions 50 of overhanging
edges 60. In another embodiment, notch 54a is located at the
intersection of fin 34a and parallel fin structure portion 50a of
overhanging edges 60a and 60b, respectively. Thus, notches 54 can
be located on parallel fin structure portion 50, on fin body 38 of
fin 34 (e.g., the side rather than the bottom) or on a combination
of the two (i.e. part of fin body 38 and part of parallel fin
structure portion 50 is cut out to form a notch at the intersection
of fin body 38 and parallel fin structure portion 50).
[0033] FIG. 6 illustrates a cross-section of fin structure 36 with
one overhanging lateral edge and a descending lip. Fin structure 36
includes fins 34, louvers 40, louver openings 42, overhanging edge
60 and descending lip 64. Fin structure 36 can be a single
continuous piece with parallel fin structure portions 50 or a
series of unconnected fins 34 as described above. Louvers 40,
louver openings 42, parallel fin structure portions 50 and
overhanging edges 60 are as described above. As shown in FIG. 6,
overhanging edge 60 extends laterally past the right lateral edge
of heat exchange tube 28. Additionally, overhanging edge 60 is
connected to descending lip 64 that extends downward from
overhanging edge 60 and to one side of heat exchange tube 28.
Descending lip 64 can extend at the same angle as fin 34 and
overhanging edge 60. Alternatively, descending lip 64 can extend
from overhanging edge 60 in a downward or other generally downward
angle. Overhanging edge 60 and descending lip 64 work cooperatively
to improve drainage of water from fin structure 36. Water is
directed across fins 34 or parallel fin structure portions 50b of
fin structure 36 by airflow passing over heat exchange tubes 28 and
fin structure 36. Once the water reaches overhanging edge 60 or the
lateral edge of lower parallel fin structure portion 50b, the water
travels down descending lip 64, aided by gravity. When little or no
airflow is present over heat exchange tubes 28 and fin structure
36, descending lip 64 still improves water drainage. Water near the
lateral edge of parallel fin structure portions 50b that might
contact heat exchange tube 28 due to water surface tension is
directed downward by descending lip 64, away from heat exchange
tube 28. Descending lips 64 can overlap one another or have line
contact or a gap separating adjacent descending lips 64. Descending
lips 64 can be associated with every fin 34 or alternatively be
associated with only some fins 34 in a particular pattern (e.g.,
every third fin, every fifth fin, etc.).
[0034] FIG. 6A illustrates a perspective view of fin structure 36
with overhanging edges 60 and descending lips 64a and 64c. Louvers
40 have been omitted from FIG. 6A to better illustrate overhanging
edges 60 and descending lips 64a and 64c. It should be understood
that fins 34 with overhanging edges 60 and descending lips 64a and
64c can include louvers 40. Fins 34a and 34c include overhanging
edges 60a and 60c, respectively. Overhanging edges 60a and 60c
extend laterally beyond the edge of heat exchange tubes 28. Fins
34b and 34d do not have overhanging edges 60 and fin bodies 38 of
fins 34b and 34d do not extend laterally beyond the edge of heat
exchange tubes 28. Descending lips 64a and 64c are located adjacent
to overhanging edges 60a and 60c. Portions of descending lips 64a
and 64c extend from overhanging edges 60a and 60c in a direction
roughly parallel to parallel fin structure portion 50. Additional
portions of descending lips 64a and 64c extend downward. Descending
lips 64a and 64c are typically located on the downstream side of
heat exchange tubes 28, but can also be located on the upstream
side of heat exchange tubes 28. Descending lips 64a and 64c help
direct water away from fin structure 36 by encouraging water to
flow in a generally downward direction. In one embodiment,
descending lips 64a and 64c are formed by cutting fin bodies 38 of
fins 34b and 34d and part of parallel fin structure portion 50 and
bending the cut fin bodies 38 in a downward direction to form
descending lips 64a and 64c.
[0035] FIG. 7 illustrates a cross section view of fin structure 36
with two overhanging lateral edges 60a and 60b and two descending
lips 64a and 64b. Although descending lips 64, 64a and 64b are
shown to have generally rectangular cross-sections, any other
cross-sections, such as trapezoidal, triangular or curved are also
acceptable and can equally benefit from the invention.
[0036] FIG. 8 illustrates a perspective view of fin structure 36
having curved fins 34. Fin structure 36 is shown with the top heat
exchange tube 28 in phantom to better show the elements of curved
fin structure 36. Fin structure 36 includes fin 34, louvers 40 and
louver openings 42 as shown in FIG. 8. Fin structure 36 can also
include notches 54 (fin 34a includes notches 54; fin 34b does not
include notches 54). Louvers 40, louver openings 42 and notches 54
are as described above. Fin structure 36 can be arranged in
relation to heat exchange tube 28 as shown in FIG. 8 where the
plane formed between each end of fin 34 is generally perpendicular
to the longitudinal axis of heat exchange tube 28 (fin structure
36a). Alternatively, fin structure 36 can be rotated to provide
better water drainage properties. Fin structure 36 can be rotated
to better direct the airflow through heat exchanger 20 to remove
water from heat exchange tubes 28 (fin structure 36b). In a
vertical tube arrangement, fin structure 36 can be rotated to
improve gravitational water drainage. Rotation of curved fin
structure 36 can be used to balance water drainage needs along with
thermal performance and pressure drop characteristics of heat
exchanger 20. Fin structure 36 may consist of individual fins 34 as
shown in FIG. 8 or fins 34 interconnected together by parallel fin
structure portions 50, as described above.
[0037] FIG. 9 illustrates a perspective view of fin structure 36
having an angled fin. Fin structure 36 is shown with the top heat
exchange tube 28 in phantom to better show the elements of angled
fin structure 36. Fin structure 36 includes two or more fin
segments 66, louvers 40 and louver openings 42 as shown in FIG. 8.
Fin structure 36 can also include notches 54 (fin structure 36a
does not include notches 54; fin structure 36b includes notches
54). Louvers 40, louver openings 42 and notches 54 are as described
above. Similar to the embodiments illustrated in FIG. 8, angled fin
structure 36 can be rotated to improve water drainage. Fin
structure 36a includes two fin segments 66a and 66b. Fin segments
66a and 66b are connected to one another at an angle (i.e. fin
segments 66a and 66b are not parallel). The angle between fin
segments 66a and 66b can vary depending on the orientation of heat
exchange tubes 28 (i.e.
[0038] horizontal or vertical, or any position in between) and the
desired pressure drop across heat exchanger 20. Suitable angles
between fin segments 66a and 66b include angles between about
100.degree. and about 170.degree.. Each fin segment 66a and 66b has
louvers 40 and louver openings 42. Fin structure 36b includes three
fin segments 66c, 66d and 66e. Fin segment 66d includes notches 54.
Rotation of angled fin structure 36 can be used to balance water
drainage needs along with thermal performance and pressure drop
characteristics of heat exchanger 20. Fin structure 36 may consist
of individual fins 34 as shown in FIG. 9 or fins 34 interconnected
together by parallel fin structure portions 50, as described above.
Also, the curved and angled fin structures 36 depicted in FIGS. 8
and 9, although reducing condensate surface tension by themselves,
may also include one or both overhanging edges 60 and descending
lips 64, as described above.
[0039] FIG. 10A is a partial perspective view of a microchannel
heat exchanger with vertical tubes. Part of heat exchanger 20 is
shown cutaway to better illustrate heat exchange tubes 28 and fin
structures 36. FIG. 10B is an exploded view of fin structure 36 of
FIG. 10A. Fin structure 36 includes fins 34 with louvers 40 and
louver openings 42. Louvers 40 and louver openings 42 are as
described above. A distinctive feature of fin structure 36 shown in
FIGS. 10A and 10B is that fin structure 36 is rotated 90.degree.
while being assembled and integrated into heat exchanger 20. Fins
34 of fin structure 36 form a corrugated pattern along a
longitudinal axis of heat exchange tubes 28. This naturally allows
gravitational condensate drainage off of fin structure 36. All of
the other features described above can also be incorporated in such
a design, as well. Louver openings 42 and potentially additional
notches 54 can be designed and sized to achieve adequate pressure
drop characteristics for heat exchanger 20.
[0040] While the invention has been described with reference to
exemplary embodiments, it will be understood by those skilled in
the art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiments disclosed, but that the invention will
include all embodiments falling within the scope of the appended
claims.
* * * * *