U.S. patent application number 12/520929 was filed with the patent office on 2010-01-21 for multi-channel heat exchanger with improved condensate drainage.
This patent application is currently assigned to CARRIER CORPORATION. Invention is credited to Alexander Lifson, Michael F. Taras.
Application Number | 20100012305 12/520929 |
Document ID | / |
Family ID | 39562805 |
Filed Date | 2010-01-21 |
United States Patent
Application |
20100012305 |
Kind Code |
A1 |
Taras; Michael F. ; et
al. |
January 21, 2010 |
MULTI-CHANNEL HEAT EXCHANGER WITH IMPROVED CONDENSATE DRAINAGE
Abstract
A heat exchanger includes a first generally vertical header and
a second generally vertical header and a generally vertical array
of a plurality of generally flat heat exchange tubes extending in a
horizontal direction therebetween. Each heat exchange tube has a
plurality of channels extending longitudinally in parallel
relationship from its inlet end to its outlet end, each channel
defining a discrete refrigerant flow path. A plurality of fins
extends between parallel-arrayed tubes. To facilitate drainage of
the collected condensate from the external surfaces of the flat
heat exchange tubes, the tubes are aligned at a slight angle with
respect to the horizontal so that the trailing edge of each tube is
positioned lower than the leading edge of each tube. To further
assist in the condensate drainage, the trailing edge of each of the
fins may extend beyond the trailing edge of the associated heat
transfer tubes and a lower extension lip may extend downwardly from
the trailing edge of each of the fins.
Inventors: |
Taras; Michael F.;
(Fayetteville, NY) ; Lifson; Alexander; (Manlius,
NY) |
Correspondence
Address: |
MARJAMA MULDOON BLASIAK & SULLIVAN LLP
250 SOUTH CLINTON STREET, SUITE 300
SYRACUSE
NY
13202
US
|
Assignee: |
CARRIER CORPORATION
Farmington
CT
|
Family ID: |
39562805 |
Appl. No.: |
12/520929 |
Filed: |
December 26, 2006 |
PCT Filed: |
December 26, 2006 |
PCT NO: |
PCT/US06/49290 |
371 Date: |
June 23, 2009 |
Current U.S.
Class: |
165/175 ;
165/182; 62/285; 62/515 |
Current CPC
Class: |
F28F 17/005 20130101;
F28F 1/12 20130101; F28D 1/05383 20130101; F28F 1/022 20130101 |
Class at
Publication: |
165/175 ;
165/182; 62/285; 62/515 |
International
Class: |
F28F 9/26 20060101
F28F009/26; F28F 1/12 20060101 F28F001/12; F25D 21/14 20060101
F25D021/14; F25B 39/02 20060101 F25B039/02 |
Claims
1. A heat exchanger for cooling a flow of air passed therethrough
comprising: first and second spaced apart and generally vertical
longitudinally extending headers; and at least one heat exchange
tube having a flattened cross-section and defining at least one
fluid flow path extending along a longitudinal axis thereof, said
at least one heat flattened exchange tube extending longitudinally
in a horizontal direction between said first and second headers and
having an inlet to said fluid flow path opening in fluid
communication to said first header and an outlet to said fluid flow
path opening in fluid communication to the second header, said at
least one flattened heat exchange tube having a transverse axis
extending from a leading edge of said at least one flattened heat
exchange tube to a trailing edge of said at least one flattened
heat exchange tube, said leading edge disposed upstream with
respect to air flow of said trailing edge, the transverse axis of
said at least one flatted heat exchange tube disposed at an acute
angle with the horizontal with said leading edge disposed
vertically higher than said trailing edge.
2. A heat exchanger as recited in claim 1 wherein said at least one
flattened heat exchange tube comprises a plurality of flattened
heat exchange tubes disposed in parallel, spaced relationship in a
generally vertical array.
3. A heat exchanger as recited in claim 2 further comprising a
plurality of fins extending between adjacent tubes of said parallel
tube array.
4. A heat exchanger as recited in claim 3 wherein said plurality of
fins extends from a position aft of the leading edges of adjacent
tubes of said parallel tube array to a position forward of the
trailing edges of adjacent tubes of said tube array.
5. A heat exchanger as recited in claim 3 wherein said plurality of
fins extends from a position aft of the leading edges of adjacent
tubes of said parallel tube array to a position aft of the trailing
edges of adjacent tubes of said tube array.
6. A heat exchanger as recited in claim 5 wherein the portion of
each of said plurality of fins extending aft of the trailing edges
of adjacent tubes of said tube array includes a lip portion
extending behind the trailing edge of tube of said parallel array
of tubes lying subadjacent said fin.
7. A heat exchanger as recited in claim 3 wherein said plurality of
fins comprises a plurality of generally vertical plate-like fins
extending between adjacent tubes of said parallel tube array.
8. A heat exchanger as recited in claim 3 wherein said plurality of
fins comprises serpentine-like corrugated fins extending between
adjacent tubes of said parallel tube array.
9. A heat exchanger as recited in claim 8 wherein said a
serpentine-like corrugated fins extending between adjacent tubes of
said parallel tube array are forming one of generally triangular,
rectangular or trapezoidal airflow passages.
10. A heat exchanger as recited in claim 3 wherein said plurality
of fins are at least one of louvered, wavy, offset strip or flat
plate configurations.
11. A heat exchanger as recited in claim 1 wherein the transverse
axis of said at least one flattened heat exchange tube is disposed
at an acute angle with the horizontal in the range of from about 5
degrees to about 10 degrees.
12. A heat exchanger as recited in claim 11 wherein said at least
one flattened heat exchange tube comprises a plurality of flattened
heat exchange tubes disposed in parallel, spaced relationship in a
generally vertical array.
13. A heat exchanger as recited in claim 11 further comprising a
plurality of fins extending between adjacent tubes of said parallel
tube array.
14. A heat exchanger as recited in claim 13 wherein said plurality
of fins extends from a position aft of the leading edges of
adjacent tubes of said parallel tube array to a position forward of
the trailing edges of adjacent tubes of said tube array.
15. A heat exchanger as recited in claim 13 wherein said plurality
of fins extends from a position aft of the leading edges of
adjacent tubes of said parallel tube array to a position aft of the
trailing edges of adjacent tubes of said tube array.
16. A heat exchanger as recited in claim 15 wherein the portion of
each of said plurality of fins extending aft of the trailing edges
of adjacent tubes of said tube array includes a lip portion
extending behind the trailing edge of tube of said parallel array
of tubes lying subadjacent said fin.
17. A heat exchanger as recited in claim 13 wherein said plurality
of fins comprises a plurality of generally vertical plate-like fins
extending between adjacent tubes of said parallel tube array
18. A heat exchanger as recited in claim 13 wherein said plurality
of fins comprises serpentine-like corrugated fins extending between
adjacent tubes of said parallel tube array.
19. A heat exchanger as recited in claim 18 wherein said a
serpentine-like corrugated fins extending between adjacent tubes of
said parallel tube array are forming one of generally triangular,
rectangular or trapezoidal airflow passages.
20. A heat exchanger as recited in claim 13 wherein said plurality
of fins are at least one of louvered, wavy, offset strip or flat
plate configurations.
21. A heat exchanger as recited in claim 1 wherein said at least
one flattened heat exchange tube defines at least one refrigerant
flow path extending along a longitudinal axis thereof.
22. A heat exchanger as recited in claim 1 wherein said at least
one flattened heat exchange tubes defines a plurality of parallel
refrigerant flow paths extending parallel to a longitudinal axis
thereof, each refrigerant flow path of said plurality of parallel
refrigerant flow paths having an inlet to said refrigerant flow
path opening in fluid communication to said first header and an
outlet to said refrigerant flow path opening in fluid communication
to the second header.
23. A heat exchanger as recited in claim 22 wherein said plurality
of parallel fluid flow paths form at least one of rectangular,
triangular, trapezoidal, circular or oval channels for refrigerant
flowing herethrough.
24. A heat exchanger as recited in claim 1 wherein said at least
one flattened heat transfer tube has internal heat transfer
enhancement elements.
25. A heat exchanger as recited in claim 1 wherein said at least
one flattened heat transfer tube has one of rectangular or oval
cross-section.
26. A heat exchanger as recited in claim 1 wherein said heat
exchanger is a refrigerant system evaporator.
27. A heat exchanger as recited in claim 1 wherein said heat
exchanger has a single-pass configuration.
28. A heat exchanger as recited in claim 1 wherein said heat
exchanger has a multi-pass configuration.
Description
FIELD OF THE INVENTION
[0001] This invention relates generally to refrigerant vapor
compression system heat exchangers having a plurality of parallel,
flat tubes extending between a first header and a second header
with fins positioned between these tubes, and more particularly, to
providing for improved drainage of condensate collecting on the
external surfaces of the flat tubes and fins.
BACKGROUND OF THE INVENTION
[0002] Refrigerant vapor compression systems are well known in the
art. Air conditioners and heat pumps employing refrigerant vapor
compression cycles are commonly used for cooling or cooling/heating
air supplied to a climate controlled comfort zone within a
residence, office building, hospital, school, restaurant or other
facility. Refrigerant vapor compression systems are also commonly
used for cooling air, or other secondary media such as water or
glycol solution, to provide a refrigerated environment for food
items and beverage products with display cases, bottle coolers or
other similar equipment in supermarkets, convenience stores,
groceries, cafeterias, restaurants and other food service
establishments.
[0003] Conventionally, these refrigerant vapor compression systems
include a compressor, a condenser, an expansion device, and an
evaporator serially connected in refrigerant flow communication.
The aforementioned basic refrigerant vapor compression system
components are interconnected by refrigerant lines in a closed
refrigerant circuit and arranged in accord with the vapor
compression cycle employed. The expansion device, commonly an
expansion valve or a fixed-bore metering device, such as an orifice
or a capillary tube, is disposed in the refrigerant line at a
location in the refrigerant circuit upstream, with respect to
refrigerant flow, of the evaporator and downstream of the
condenser. The expansion device operates to expand the liquid
refrigerant passing through the refrigerant line, connecting the
condenser to the evaporator, to a lower pressure and temperature.
The refrigerant vapor compression system may be charged with any of
a variety of refrigerants, including, for example. R-12, R-22,
R-134a, R-404A, R-410A, R-407C, R717, R744 or other compressible
fluid.
[0004] In some refrigerant vapor compression systems, the
evaporator is a parallel tube heat exchanger having a plurality of
tubes extending longitudinally in parallel, spaced relationship
between a first generally vertically extending header or manifold
and a second generally vertically extending header or manifold, one
of which serves as an inlet header/manifold. The inlet header
receives the refrigerant flow from the refrigerant circuit and
distributes the refrigerant flow amongst the plurality of parallel
flow paths through the heat exchanger. The other header serves to
collect the refrigerant flow as it leaves the respective flow paths
and to direct the collected flow back to the refrigerant line for
return to the compressor in a single pass heat exchanger or to a
downstream bank of parallel heat exchange tubes in a multi-pass
heat exchanger. In the latter case, this header is an intermediate
manifold or a manifold chamber and serves as an inlet header to the
next downstream bank of parallel heat transfer tubes.
[0005] Historically, such parallel tube heat exchangers used in
refrigerant vapor compression systems have used round tubes,
typically having a diameter of 1/2 inch, 3/8 inch or 7 millimeters.
More recently, flat, typically rectangular or oval in
cross-section, multi-channel tubes are being used in heat
exchangers for refrigerant vapor compression systems. Each
multi-channel tube generally has a plurality of flow channels
extending longitudinally in parallel relationship the entire length
of the tube, each channel providing a relatively small flow area
refrigerant flow path. Thus, a heat exchanger with multi-channel
tubes extending in parallel relationship between the inlet and
outlet headers of the heat exchanger will have a relatively large
number of small flow area refrigerant flow paths extending between
the two headers. Sometimes, such multi-channel heat exchanger
constructions are called microchannel or minichannel heat
exchangers as well.
[0006] Commonly, fins are positioned between heat transfer tubes
for heat transfer enhancement, structural rigidity and heat
exchanger design compactness. The heat transfer tubes and fins are
permanently attached to each other (as well as to the manifolds)
during furnace braze operation. The fins may have flat, wavy,
corrugated or louvered design and typically form triangular,
rectangular, offset or trapezoidal airflow passages.
[0007] When a heat exchanger is used as an evaporator in a
refrigerant vapor compression system, moisture in the air flowing
through the evaporator and over the external surface of the
refrigerant conveying tubes and associated fins of the heat
exchanger condenses out the air and collects on the external
surface of the those tubes and fins. In general, condensate
naturally drains well from refrigerant vapor compression system
evaporators having round heat transfer tubes and plate fins due to
the cylindrical outer surface of a round tube and vertically
extended plate fins. For evaporator heat exchangers having the flat
tubes and serpentine fins arranged in a vertical orientation
extending between a pair of horizontally disposed headers, such as,
for example, the heat pump evaporator/condenser heat exchanger
disclosed in U.S. Pat. No. 5,826,649, the condensate depositing on
the heat transfer tubes and associated heat transfer fins
inherently drains down the vertically extending tubes under the
influence of gravity. The draining condensate is typically
collected in a drain pan disposed beneath the heat exchanger.
[0008] U.S. Pat. No. 5,279,360 discloses an evaporator heat
exchanger having an array of parallel heat exchange tubes of
flattened cross-section disposed in spaced relationship with
V-shaped fins disposed between the facing flat surfaces of adjacent
heat exchange tubes. Each heat exchange tube is bent into a V-shape
and disposed in a vertical plane with its inlet end connected in
fluid communication with a first horizontally extending header and
its outlet end connected in fluid communication with a second
horizontally extending header. The apexes of the arrayed
V-shape-bent heat exchange tubes are aligned at a lower elevation
than the headers, and a condensate trough is disposed therebeneath.
Condensate collecting on the flattened heat exchange tubes and the
fins therebetween drains downwardly along the respective fin-free
edge surfaces of the flattened heat exchange tubes to the
condensate trough.
[0009] However, with respect to prior art heat exchangers having
tubes of flattened cross-section disposed horizontally and
extending longitudinally in a horizontal direction between a pair
of spaced, generally vertical headers, condensate collecting on the
upper side of the tubes does not drain therefrom because of the
horizontal disposition of the flat external surface of the tube. If
the condensate collecting on the external surfaces of the heat
exchanger tubes becomes excessive, overall performance of the
refrigerant vapor compression system will be adversely impacted.
For example, excessive condensate retention of the external
surfaces of the heat exchange tubes can result in increased air
side pressure drop through the evaporator which causes increased
fan power consumption and reduced heat transfer through the heat
transfer tubes. Also, condensate collecting on the external
surfaces of the heat transfer tubes of the evaporator may be
undesirability re-entrained in the air passing through the
evaporator and transversely over the flattened tubes. Further,
under certain conditions, excessive condensate retention promotes
faster frost accumulation and undesirably requires more frequent
defrost cycles.
SUMMARY OF THE INVENTION
[0010] A heat exchanger having generally flattened heat exchange
tubes extending longitudinally between a pair of spaced headers is
provided wherein condensate collecting on the flat surfaces of the
tubes from an airflow passing over the tubes inherently drains from
the external flat surfaces of the flattened heat transfer
tubes.
[0011] The heat exchanger includes first and second spaced apart
and generally vertical longitudinally extending headers, and at
least one heat exchange tube having a generally flattened
cross-section and defining at least one fluid flow path extending
along a longitudinal axis thereof. The flattened heat exchange tube
extends longitudinally in a horizontal direction between the first
and second headers and has an inlet to the fluid flow path opening
in fluid communication to the first header and an outlet to the
fluid flow path opening in fluid communication to the second
header. The flattened heat exchange tube has a transverse axis
extending from its leading edge to its trailing edge, the leading
edge being disposed upstream with respect to airflow of the
trailing edge. The transverse axis of the flatted heat exchange
tube is disposed at an acute angle with the horizontal with the
leading edge preferably disposed vertically higher than the
trailing edge. In one embodiment, the transverse axis of the
flattened heat exchange tube is disposed at an acute angle with the
horizontal in the range of from about 5 degrees to about 10
degrees.
[0012] In an embodiment, the heat exchanger includes a plurality of
flattened heat exchange tubes disposed in parallel, spaced
relationship in a generally vertical array. Additionally, the heat
exchanger may include a plurality of heat transfer fins extending
between adjacent tubes of the parallel tube array. In an
embodiment, the plurality of fins extends from a position aft of
the leading edges of adjacent tubes of the parallel tube array to a
position forward of the trailing edges of adjacent tubes of the
tube array. In an embodiment, the plurality of fins extends from a
position aft of the leading edges of adjacent tubes of the parallel
tube array to a position aft of the trailing edges of adjacent
tubes of the tube array and that portion of each of the fins
extending aft of the trailing edges of adjacent tubes of the tube
array may include a lip portion extending behind the trailing edge
of tube of the parallel array of tubes lying subadjacent the fin.
In an embodiment, the plurality of fins may comprise a plurality of
generally vertical plate-like fins extending between adjacent tubes
of said parallel tube array. Alternatively, corrugated serpentine
fins may be disposed between the tubes. The fins may have a flat,
wavy, offset strip or louvered design and form triangular,
rectangular, or trapezoidal airflow passages.
[0013] In an embodiment of the heat exchanger, each flattened heat
exchange tube defines a plurality of parallel fluid flow paths
extending parallel to a longitudinal axis thereof, with each fluid
flow path of the plurality of parallel fluid flow paths having an
inlet to the fluid flow path opening in fluid communication to the
first header and an outlet to the fluid flow path opening in fluid
communication to the second header. The plurality of the channels
defining the flow paths within each heat transfer tube may be of
circular, oval, rectangular, triangular or trapezoidal
cross-section. In an embodiment, each of the fluid flow paths may
comprise a refrigerant flow path.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] In the following detailed description of the invention,
reference will be made to and is to be read in connection with the
accompanying drawing, where:
[0015] FIG. 1 is a schematic diagram of a refrigerant vapor
compression system incorporating a heat exchanger as an
evaporator;
[0016] FIG. 2 is a perspective view of an exemplary embodiment of
an evaporator heat exchanger in accordance with the invention;
[0017] FIG. 3 is a partially sectioned, elevation view taken along
line 3-3 of FIG. 2;
[0018] FIG. 4 is a partially sectioned, elevation view of another
exemplary embodiment of an evaporator heat exchanger in accordance
with the invention; and
[0019] FIG. 5 is a partially sectioned, elevation view of an
alternate exemplary embodiment of an evaporator heat exchanger in
accordance with the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0020] The heat exchanger of the invention will be described herein
in use as an evaporator in connection with a simplified air
conditioning cycle refrigerant vapor compression system 100 as
depicted schematically in FIG. 1. Although the exemplary
refrigerant vapor compression cycles illustrated in FIG. 1 is a
simplified air conditioning cycle, it is to be understood that the
heat exchanger of the invention may be employed in refrigerant
vapor compression systems of various designs, including, without
limitation, heat pump cycles, economized cycles, cycles with tandem
components such as compressors and heat exchangers, chiller cycles,
cycles with reheat and many other cycles including various options
and features.
[0021] The refrigerant vapor compression system 100 includes a
compressor 105, a condenser 110, an expansion device 120, and the
heat exchanger 10, functioning as an evaporator, connected in a
closed loop refrigerant circuit by refrigerant lines 102, 104 and
106. The compressor 105 circulates hot, high pressure refrigerant
vapor through discharge refrigerant line 102 into the inlet header
of the condenser 110, and thence through the heat exchanger tubes
of the condenser 110 wherein the hot refrigerant vapor is
desuperheated, condensed to a liquid and typically subcooled as it
passes in heat exchange relationship with a cooling fluid, such as
ambient air, which is passed over the heat exchange tubes by the
condenser fan 115.
[0022] The high pressure, liquid refrigerant leaves the condenser
110 and thence passes through liquid refrigerant line 104 to the
evaporator heat exchanger 10, traversing the expansion device 120
wherein the refrigerant is expanded to a lower pressure and
temperature to form a refrigerant liquid/vapor mixture. The now
lower pressure and lower temperature, expanded refrigerant thence
passes through the heat exchanger tubes 40 of the evaporator heat
exchanger 10 wherein the refrigerant is evaporated and typically
superheated as it passes in heat exchange relationship with air to
be cooled (and, in many cases, dehumidified), which is passed over
the heat exchange tubes 40 and associated heat transfer fins 50 by
the evaporator fan 15. The refrigerant, predominantly in a vapor
thermodynamic state, collects in the outlet header 30 of the
evaporator heat exchanger 10 and passes therefrom through suction
refrigerant line 106 to return to the compressor 105 through the
suction port thereto. As the air flow traversing the evaporator
heat exchanger 10 passes over the heat exchange tubes 40 and heat
transfer fins 50 in heat exchange relationship with the refrigerant
flowing through the heat exchange tubes 40, the air is cooled and
the moisture in the air flowing through the evaporator heat
exchanger 10 and over the external surface of the refrigerant
conveying tubes 40 and heat transfer fins 50 of the evaporator heat
exchanger 10 condenses out the air and collects of the external
surface of the tubes and fins. A drain pan 45 is provided beneath
the evaporator heat exchanger 10 for collecting condensate that
drains from the external surface of the tubes 40 and fins 50.
[0023] The parallel flow heat exchanger 10 will be described herein
in general with reference to the illustrative embodiments of the
heat exchanger 10 depicted in FIGS. 2-4. The heat exchanger 10
includes a plurality of heat exchange tubes 40 arranged in a
generally vertical array, each of which extends in a horizontal
direction along its longitudinal axis between a generally
vertically extending first header 20 and a generally vertically
extending second header 30, thereby providing a plurality of
refrigerant flow paths between the two headers. Although the
refrigerant headers 20 and 30 are shown of a cylindrical
configuration, the may be of a rectangular, half of cylinder or any
other shape as well as have a single chamber or multi-chamber
design, depending on the refrigerant path arrangement. Each heat
exchange tube 40 has a first end mounted to the first header 20, a
second end mounted to the second header 30, and a plurality of
parallel flow channels 42 extending longitudinally, i.e. along the
generally horizontally disposed longitudinal axis of the tube, the
entire length of the tube, whereby the each of the individual flow
channels 42 provides a flow path in refrigerant flow communication
between the first header and the second header. The internal
refrigerant pass arrangement may be a single-pass configuration or
a multi-pass configuration, depending on particular application
requirements.
[0024] Additionally, each multi-channel heat exchange tube 40 has a
generally flattened cross-section, for example, a rectangular
cross-section or oval cross-section, and defines an interior that
may be subdivided to form a side-by-side array of independent flow
channels 42. Each flattened multi-channel tube 40 may have a width
as measured along a transverse axis extending from the leading edge
44 to the trailing edge 46 of, for example, fifty millimeters or
less, typically from ten to thirty millimeters, and a height of
about two millimeters or less, as compared to conventional prior
art round tubes having a diameter of 1/2 inch, 3/8 inch or 7 mm.
The tubes 40 are shown in the accompanying drawings, for ease and
clarity of illustration, as having ten channels 42 defining flow
paths having a circular cross-section. However, it is to be
understood that in applications, each multi-channel tube 40 may
typically have from about ten to about twenty flow channels 42.
Generally, each flow channel 42 will have a hydraulic diameter,
defined as four times the cross-sectional flow area divided by the
"wetted" perimeter, in the range generally from about 200 microns
to about 3 millimeters. Although depicted as having a circular
cross-section in the drawings, the channels 42 may have a
rectangular, triangular, oval or trapezoidal cross-section, or any
other desired non-circular cross-section. Also, heat transfer tubes
40 may have other internal heat transfer enhancement elements, such
as mixers and boundary layer destructors.
[0025] As in conventional practice, to improve heat transfer
between the air flowing through the heat exchanger 10 over the
external surface of the heat transfer tubes 40 and the refrigerant
flowing through the parallel flow channels 42 of the heat transfer
tubes 40, the heat exchanger 10 includes a plurality of external
heat transfer fins 50 extending between each set of the
parallel-arrayed tubes 40. The fins are brazed or otherwise
securely attached to the external surfaces of the adjoining tubes
40 to establish heat transfer contact, by heat conduction, between
the fins 50 and the external surface of the flat heat transfer
tubes 40. Thus, the external surfaces of the heat transfer tubes 40
and the surfaces of the fins 50 together form the external heat
transfer surface that participates in heat transfer interaction
with the air flowing through the heat exchanger 10. The external
heat transfer fins 50 also provide for structural rigidity of the
heat exchanger 10 and quite often assist in air flow redirection to
improve heat transfer characteristics. In the exemplary embodiment
of the heat exchanger 10 depicted in FIG. 2, the fins 50 constitute
a plurality of plates disposed in parallel, spaced relationship and
extending generally vertically between the heat transfer tubes 40.
However, it is to be understood that other fin configurations, such
as, for example, generally corrugated serpentine wavy, offset or
louvered fins forming triangular, rectangular, or trapezoidal
airflow passages may be used instead of generally vertical fins in
the evaporator heat exchanger of the invention.
[0026] To facilitate drainage of the collected condensate from the
external surfaces of the flat heat exchange tubes 40, the tubes 40
are aligned with their transverse axes at an slight angle with
respect to the horizontal so that the trailing edge 46 of each tube
40 is positioned lower than the leading edge 44 of each tube 40.
The leading edge 44 is the edge of the heat exchange tube 40
disposed at the air flow inlet side of the heat exchanger 10 and
the trailing edge 46 is the edge of the heat exchange tube 40
disposed at the air flow outlet side of the heat exchanger 10.
Under the influence of gravity and assisted by the airflow sheer
force, with the trailing edge 46 of each tube 40 in the generally
vertical array of horizontally extending tubes 40 of the heat
exchanger 10 being positioned lower than the leading edge 44,
condensate collecting of the external generally flat surfaces of
the tubes 40 will flow transversely along the width of each tube 40
in the direction of the air flow across the generally flat surfaces
of the tubes to pass off the respective trailing edges 46 of tubes
40 and drain into the drain pan 45. Condensate depositing on the
surface of each of the fins 50 will drain downwardly unto the upper
external surface of the tube 40 subjacent the lower end of the fin
and likewise flow to the trailing edge of the tube and drain
therefrom into the drain pan 45. Thus, with respect to the
evaporator heat exchanger 10, both gravity and the airflow passing
over the external surface of the heat exchange tubes 40 serve to
facilitate drainage of condensate deposited on the external
surfaces of the tubes 40. In an embodiment, the transverse axis of
the flattened heat exchange tubes 40 is disposed at an acute angle
with the horizontal in the range of from about 5 degrees to about
10 degrees, facilitating condensate drainage, while not
compromising the airflow pattern.
[0027] In the exemplary embodiments of the evaporator heat
exchanger 10 depicted in FIGS. 4 and 5, the trailing edges 56 of
the fins 50 extend beyond the trailing edges 46 of the respective
heat exchange tubes 40. In these embodiments, the condensate may
simply drain off the trailing edge 46 of each heat exchange tube 40
to drip into the drain pan 45, or the condensate may flow along the
lower surface of the portion of the trailing edge 56 extending
beyond the trailing edges 46 of the heat exchange tubes 40 to drip
into the drain pan 45. In the exemplary embodiment depicted in FIG.
5, the trailing edge 56 of each of the fins 50 includes a lower
extension 58 that extends downwardly aft of the trailing edge 46 of
the heat exchange tube 40 subadjacent that fin to the fin 50
positioned next below. In this embodiment, the lower extension 58
further facilitates drainage of condensate by providing a
downwardly extending surface along which the condensate will flow
to the fin next below and eventually drain from the extension 58 of
the lower most fin 50 into the condensate drain pan 45.
Additionally, a lip 59 may be provided extending outwardly from the
lower extension 58 and beneath the trailing edge 46 of the
subadjacent tube 40 to provide a surface for directing condensate
draining off the trailing edge 46 of that tube 40.
[0028] While the present invention has been particularly shown and
described with reference to the preferred mode as illustrated in
the drawing, it will be understood by one skilled in the art that
various changes in detail may be effected therein without departing
from the spirit and scope of the invention as defined by the
claims.
* * * * *