U.S. patent application number 13/002692 was filed with the patent office on 2011-06-02 for microchannel heat exchanger module design to reduce water entrapment.
Invention is credited to Jack Leon Esfromes, Michael F. Taras.
Application Number | 20110127015 13/002692 |
Document ID | / |
Family ID | 41797395 |
Filed Date | 2011-06-02 |
United States Patent
Application |
20110127015 |
Kind Code |
A1 |
Taras; Michael F. ; et
al. |
June 2, 2011 |
MICROCHANNEL HEAT EXCHANGER MODULE DESIGN TO REDUCE WATER
ENTRAPMENT
Abstract
A microchannel heat exchanger has a core having at least one
heat exchange tube bank having a plurality of flow channels with a
small hydraulic diameter less than 5 mm. A means is provided to
reduce the amount of water retained on the external surfaces of the
at least one heat exchange tube bank. These means may utilize the
incorporation of a particular routing of refrigerant within the
heat exchanger, the operation and control of a fan associated with
the heat exchanger, or the provision of structure to at least
partially block liquid from reaching the heat exchanger tube
bank.
Inventors: |
Taras; Michael F.;
(Fayetteville, NY) ; Esfromes; Jack Leon;
(Jamesville, NY) |
Family ID: |
41797395 |
Appl. No.: |
13/002692 |
Filed: |
April 24, 2009 |
PCT Filed: |
April 24, 2009 |
PCT NO: |
PCT/US09/41624 |
371 Date: |
January 5, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61095019 |
Sep 8, 2008 |
|
|
|
Current U.S.
Class: |
165/104.34 ;
165/172; 165/175 |
Current CPC
Class: |
F28F 17/005 20130101;
F28F 2260/02 20130101; F25B 39/00 20130101; F28F 9/026 20130101;
F28D 2021/007 20130101; F25B 47/003 20130101; F28D 2021/0073
20130101; F28D 1/024 20130101; F28D 1/05375 20130101 |
Class at
Publication: |
165/104.34 ;
165/172; 165/175 |
International
Class: |
F28F 13/12 20060101
F28F013/12; F28F 1/10 20060101 F28F001/10; F28F 9/02 20060101
F28F009/02 |
Claims
1. A microchannel heat exchanger comprising: a heat exchanger core
including at least one heat exchange tube bank with heat exchange
tubes in the at least one heat exchange tube bank having a
plurality of internal parallel flow channels; and a means to reduce
condensate retention within the heat exchanger core.
2. The heat exchanger as set forth in claim 1, wherein said means
to reduce condensate retention within the heat exchanger core
include routing of the refrigerant flowing inside said heat
exchange tubes.
3. The heat exchanger as set forth in claim 2, wherein there are a
plurality of said heat exchange tube banks, and refrigerant flows
in opposed parallel directions through said plurality of heat
exchange tube banks from an inlet manifold, into an intermediate
manifold, and from said intermediate manifold to an outlet
manifold, said inlet manifold fluidly connected to a first heat
exchange tube bank, with both said inlet manifold and said first
heat exchange tube bank being located in a bottom section of the
heat exchanger to provide a higher temperature refrigerant to the
bottom section of the heat exchanger.
4. The heat exchanger as set forth in claim 3, wherein there are
more than two of said heat exchange tube banks, with said first
heat exchange tube bank being a vertically lowermost of said heat
exchange tube banks, and one of intermediate heat exchange tube
banks being a vertically uppermost of said heat exchange tube
banks.
5. The heat exchanger as set forth in claim 3, wherein there are
more than two of said heat exchange tube banks, with said heat
exchange tube banks being arranged in a vertically intertwined
configuration.
6. The heat exchanger as set forth in claim 5, wherein at least one
branch pipe routes refrigerant from one of said heat exchange tube
banks to another of said heat exchange tube banks.
7. The heat exchanger as set forth in claim 3, wherein a flow
control device for selectively tapping at least a portion of higher
temperature refrigerant from an upstream location to a downstream
location to provide additional heating at the downstream location
is included.
8. The heat exchanger as set forth in claim 7, wherein said
downstream location is in an intermediate manifold.
9. The heat exchanger as set forth in claim 8, wherein said
intermediate manifold communicates with a vertically lowermost one
of said plurality of heat exchange tube banks.
10. The heat exchanger as set forth in claim 1, wherein there is at
least one fan associated with the heat exchanger, said at least one
fan being operable to move air over said at least one heat exchange
tube bank to absorb heat from refrigerant flowing inside said heat
exchange tubes, said at least one fan being selectively operable in
a reverse direction to move air over said at least one heat
exchange tube bank to remove moisture accumulated on external heat
exchanger surfaces.
11. The heat exchanger as set forth in claim 1, wherein there is at
least one fan associated with the heat exchanger, said at least one
fan being operable to move air over said at least one heat exchange
tube bank to absorb heat from refrigerant flowing inside said heat
exchange tubes, said at least one fan is a variable speed fan and
said variable speed fan is selectively and periodically operated at
a reduced speed to increase temperature of refrigerant flowing
through at least one heat exchange tube bank to remove moisture
accumulated on external heat exchanger surfaces.
12. The heat exchanger as set forth in claim 1, wherein there is at
least one fan associated with the heat exchanger, said at least one
fan being operable to pull air over said at least one heat exchange
tube bank to absorb heat from refrigerant flowing inside said heat
exchange tubes, said at least one fan to be periodically turned on
during prolonged shutdown periods to move air over said at least
one heat exchange tube bank to remove moisture accumulated on
external heat exchanger surfaces.
13. The heat exchanger as set forth in claim 1, wherein there are
at least two fans associated with the heat exchanger, said at least
two fans being operable to move air over said at least one heat
exchange tube bank to absorb heat from refrigerant flowing inside
said heat exchange tubes, and at least one fan of said at least two
fans to be selectively and periodically turned off to increase
temperature of refrigerant flowing through at least one heat
exchange tube bank to remove moisture accumulated on external heat
exchanger surfaces.
14. The heat exchanger as set forth in claim 1, wherein there is a
frame structure associated with the heat exchanger, said frame
structure including a generally solid upper deck and a fan mounted
to said frame structure and moving air over said at least one heat
exchange tube bank through a fan orifice, and a cover for blocking
moisture from entering said fan orifice.
15. The heat exchanger as set forth in claim 14, wherein said cover
includes a wire mesh material.
Description
RELATED APPLICATION
[0001] This application claims priority to U.S. Provisional
Application No. 61/095,019, which was filed Sep. 8, 2008.
BACKGROUND OF THE INVENTION
[0002] In recent years, much interest and design effort has been
focused on efficient and durable operation of the heat exchangers
in refrigerant systems. Sustained high effectiveness of refrigerant
system heat exchangers directly translates into the augmented
system performance and reduced life-time cost. One relatively
recent advancement in heat exchanger technology is the development
and application of parallel flow, or so-called microchannel or
minichannel, heat exchangers (these two terms will be used
interchangeably throughout the text), as the indoor and outdoor
heat exchangers.
[0003] These parallel flow heat exchangers are provided with a
plurality of parallel heat exchange tubes, typically of a non-round
shape, among which refrigerant is distributed and flown in a
parallel manner. The heat exchange tubes typically incorporate
multiple channels and are orientated generally substantially
perpendicular to a refrigerant flow direction in the inlet,
intermediate and outlet manifolds that are in flow communication
with the heat exchange tubes. Heat transfer enhancing fins are
typically disposed in between and rigidly attached to the heat
exchange tubes. The primary reasons for the employment of the
parallel flow heat exchangers, which usually have all-aluminum
furnace-brazed construction, are related to their superior
performance, high degree of compactness, structural rigidity,
reduced refrigerant charge and enhanced resistance to
corrosion.
[0004] Microchannel heat exchangers provide beneficial results, at
least in part, because their internal flow channels are of quite
small hydraulic diameter. However, there are other challenges
associated with microchannel heat exchangers. One challenge is that
bare outdoor microchannel heat exchangers (as other heat exchanger
types) are susceptible to atmospheric corrosion in industrial and
coastal corrosive environments, due to the nature of their
construction, material system and manufacturing processes.
[0005] In particular, the increased amount of water potentially
retained on external heat exchanger surfaces and increased wet
time, particularly in coastal corrosive environments, can present
corrosion challenges.
[0006] Protective anti-corrosion coatings are known but are
expensive. On the other hand, while less expensive coatings may be
known, they are less effective. Therefore, it is desired to
considerably reduce the amount of water retained on external
surfaces of the outdoor heat exchanger (typically condenser or gas
cooler), and thus significantly slow down corrosion reaction.
SUMMARY OF THE INVENTION
[0007] In a disclosed embodiment of this invention, a microchannel
heat exchanger is provided with at least one heat exchange tube
bank having a plurality of flow channels with a hydraulic diameter
less than 5 mm, and preferably less than 2 mm, and having a means
incorporated into the heat exchanger and associated sub-system or
structural design to reduce the amount of water retained on the
heat exchanger external surfaces.
[0008] The means may utilize the incorporation of a particular
routing of refrigerant within the heat exchanger, the operation and
control of a fan associated with the heat exchanger, or the
provision of structure to at least partially block liquid from
reaching the heat exchanger tube bank.
[0009] These and other features of the present invention can be
best understood from the following specification and drawings, the
following of which is a brief description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1A shows a prior art arrangement of a microchannel heat
exchanger.
[0011] FIG. 1B schematically shows one example of known heat
exchanger.
[0012] FIG. 1C is a cross-sectional view through a tube bank.
[0013] FIG. 2 shows a first embodiment of the invention.
[0014] FIG. 3 shows a second embodiment of the invention.
[0015] FIG. 4 shows a third embodiment of the invention.
[0016] FIG. 5 shows yet another embodiment of the invention.
[0017] FIG. 6A shows another embodiment of the invention.
[0018] FIG. 6B shows a side view of a portion of the FIG. 6A
embodiment.
[0019] FIG. 6C is a top view of a portion of the FIG. 6A
embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0020] A typical microchannel heat exchanger outdoor module 20 is
illustrated in FIG. 1A. An upper deck 22 includes a fan system 24
for moving (typically pulling) air over a pair of microchannel heat
exchangers 26 and 28. As can be appreciated, water accumulated
inside outdoor module 20 will tend to collect near a lower portion
128 of this heat exchanger arrangement. Furthermore, moisture
present in the atmospheric air, particularly in humid environments,
will also accumulate on external heat exchanger surfaces. Due to
the close-coupled construction of the microchannel heat exchanger,
this moisture is retained within the heat exchanger core for
prolonged periods of time. It should be noted that the outdoor
module 20 shown in FIG. 1A is exemplary, and there many design
variations of the outdoor module arrangements, including (but not
limited to) vertical and V-shaped as well as straight and formed
heat exchangers. All these designs and constructions are within the
scope and can benefit from the invention.
[0021] As shown in FIG. 1B, the microchannel heat exchanger 26
includes an inlet 21 fluidly connected and delivering refrigerant
to a top chamber 23 of an inlet/outlet manifold 28. After leaving
the top chamber 23 of the manifold 28, refrigerant passes into a
first heat exchange tube bank 25 and to a top chamber 27 of an
opposed intermediate manifold 29. From the top chamber 27 of the
manifold 29, the refrigerant returns through a second heat exchange
tube bank 11 to an intermediate chamber 13 of the manifold 28. From
the intermediate chamber 13 of the manifold 28, refrigerant passes
through a third heat exchange tube bank 15 back to a bottom chamber
17 of the intermediate manifold 29. From the bottom chamber 17 of
the manifold 29, the refrigerant passes through yet another forth
heat exchange tube bank 19 to an outlet chamber 16 of the manifold
28. As shown, divider plates 43 divide manifolds 28 and 29 into the
chambers 23, 13, 16 and 27, 17 respectively. In addition, fins 18
are positioned between the heat exchange tube banks 25, 11, 15, and
19. It should be noted that a four-pass heat exchanger
configuration is exemplary, and different numbers of passes can be
incorporated within the same heat exchanger construction. All these
arrangements are within the scope of the invention.
[0022] As can be appreciated, in the condenser or gas cooler case,
the hottest refrigerant (refrigerant typically leaving the
compressor) is at the inlet 21 and within first heat exchange tube
bank 25 of the heat exchanger 26, namely within the top section of
the microchannel heat exchanger 26. As mentioned above, the
greatest accumulation of water will be at the lower section of the
microchannel heat exchanger 26. This top-to-bottom refrigerant flow
arrangement is typical for microchannel condensers, since
condensing refrigerant flow naturally coincides with the direction
of gravity.
[0023] As shown in FIG. 1C, the heat exchange tubes of the tube
banks include a plurality of small refrigerant channels 100
provided by separator walls 101. These channels have hydraulic
diameter less than 5 mm, and preferably less than 2 mm. The
channels can be any number of shapes and the term "diameter" does
not imply a circular cross-section.
[0024] In FIG. 2, an embodiment 32 includes an inlet chamber 30 of
an inlet/outlet manifold 180 at a vertically lower position leading
to a heat exchange tube bank 40 passing refrigerant to a chamber 36
of an intermediate manifold 182. From the chamber 36, refrigerant
passes through a heat exchange tube bank 42 to a chamber 31 of the
inlet/outlet manifold 180, and back through yet another heat
exchange tube bank 44 to another chamber 37 of the intermediate
manifold 182. From the chamber 37, the refrigerant passes through a
heat exchange tube bank 46 to an outlet chamber 33 of the
inlet/outlet manifold 180. In the FIG. 2 embodiment, as opposed to
the FIG. 1B prior art, the inlet chamber 30 is at a bottom section
of the microchannel heat exchanger 32, providing a much hotter
refrigerant to this section than would exist in the outlet chamber
33 at the heat exchanger exit.
[0025] By routing the hottest refrigerant into the inlet 30
positioned at the lower section of the microchannel heat exchanger,
the hotter refrigerant will provide more heat to evaporate moisture
retained on the external heat exchanger surfaces of the bottom area
128 of FIG. 1A, where the most amount of moisture is typically
accumulated. Thus, the effect of corrosion at the most susceptible
lower heat exchanger tube banks will be greatly reduced.
[0026] FIG. 3 shows an embodiment 60 wherein the inlet refrigerant
line 61 is also at the vertically lowermost portion leading into an
inlet chamber 62 of an inlet/outlet manifold 190. From the inlet
chamber 62, the refrigerant passes through a heat exchange tube
bank 64 to a chamber 66 in an intermediate manifold 192, a heat
exchange tube bank 68, the intermediate chamber 67 of the
inlet/outlet manifold 190, and through a branch refrigerant line 70
to another intermediate chamber 72 of the same inlet/outlet
manifold 190 not adjacent to the chamber 67, leading in turn to a
heat exchange tube bank 73. From the heat exchange tube bank 73,
the refrigerant passes through yet another intermediate chamber 74
of the intermediate manifold 192, the heat exchange tube bank 76,
and to the outlet refrigerant line 78. Essentially, this embodiment
provides hotter refrigerant at the bottom and top heat exchanger
tube bank sections 64 and 73, which might be more exposed to the
effects of corrosion than the intermediate heat exchange tube banks
68 and 76. This may be beneficial, for instance, in situations when
the top and bottom heat exchanger sections have reduced airflow and
hence much lower water removal potential, in comparison to the
center section. The FIG. 3 embodiment is purely exemplary, and
other branch line configurations to provide intertwined refrigerant
passes (in comparison to conventional staggered refrigerant passes)
are also feasible and within the scope of the invention.
[0027] FIG. 4 shows an embodiment 80 wherein the refrigerant inlet
line 82 is located within the top section of the microchannel heat
exchanger. Refrigerant flow control devices such as valves 84 and
86 selectively route refrigerant through a tap line 88 to an
injection point 90. If the valve 86 is open and the valve 84 is
closed, refrigerant will pass normally into an inlet chamber 92 of
inlet/outlet manifold 200, a heat exchange tube bank 94, an
intermediate chamber 96 of an intermediate manifold 202, back
through a heat exchange tube bank 98 to an intermediate chamber 112
of the inlet/outlet manifold 200. From the intermediate chamber 112
refrigerant passes through a heat exchange tube bank 103 to a
chamber 105 of the intermediate manifold 202, and a heat exchange
tube bank 102. From the heat exchange tube bank 102, the
refrigerant passes through an outlet chamber 110 of the
inlet/outlet manifold 200 and to an outlet refrigerant line 108.
This embodiment will operate as in the prior art of FIG. 1B.
However, either periodically, or when some indication has been
received that there is moisture accumulating on the external
surfaces of the lower heat exchange tube bank 102, the valve 86 may
be closed or restricted and the valve 84 opened (partially or
fully). Thus, at least a portion of hot refrigerant vapor from the
inlet refrigerant line 82 will pass into the injection point 90.
This hot refrigerant will provide additional heat to assist in
evaporation of accumulated condensate on the external surfaces of
the low heat exchange tube bank 102. The valves 84 and 86 can be
ON/OFF solenoid valves or regulating valves and can be operated in
a pulsation mode or in a modulation mode respectively. As was
stated above, the FIG. 4 embodiment is exemplary, and other
refrigerant bypass line configurations to provide a higher
temperature refrigerant to the heat exchanger sections with
increased amount of accumulated condensate on a periodic basis are
also feasible and within the scope of the invention.
[0028] FIG. 5 shows yet another embodiment encapsulating a
different way of reducing the condensate amount accumulated on
external heat exchanger surfaces of an outdoor heat exchanger
module 120. In the outdoor heat exchanger module 120, there are
microchannel heat exchangers 122 and 124 and an air-moving device
such as fan 126. The fan 126 typically operates in a forward
direction to pull air over the microchannel heat exchangers 122 and
124 and then through a fan orifice 128. However, the fan 126 may be
run in reverse to blow air over the heat exchangers 122 and 124,
thus also blowing the accumulated condensate off of the external
surfaces of the heat exchangers 122 and 124 (since airflow and
gravity directions are coincidental now). The fan 126 may be run in
reverse either periodically, or, again, when some indication has
been received (such as, for instance, increased airside pressure
drop) regarding condensate accumulation on external surfaces of the
heat exchangers 122 and 124. Typically, axial fans provided within
outdoor heat exchanger modules have sufficient airflow, while
running in reverse, but other fan types can be utilized as well. If
the fan 126 is a multi-speed or variable speed fan, then fan speed
may be increased to reduce the condensate removal time. Further, if
a multi-fan system is associated with the outdoor heat exchanger
module 120, the number of operating fans may be increased to
shorten the blow-off time as well. It should be pointed out that
fan reversed operation can be coincidental with refrigerant system
compressor operation, so that hot refrigerant circulating
throughout the refrigerant system assists in condensate removal
through evaporation, or fan reversals can be executed and
controlled independently.
[0029] Furthermore, to remove condensate from external surfaces of
the heat exchangers 122 and 124, during prolonged periods of
shutdown in particular, fan system 126 can be turned on
periodically, based on a timer or a sensor reading. Additionally,
during normal operation, particularly at low ambient temperatures,
a number of operational fans can be reduced (e.g. for a multi-fan
system), or a speed of a variable speed fan can be reduced, to
achieve lower airflow and higher temperature of the refrigerant
circulating through the heat exchangers 122 and 124, thus resulting
in faster condensate evaporation and heat exchanger dryout.
[0030] FIG. 6A shows an embodiment 129 intended to reduce the
likelihood of rain water reaching the heat exchanger cores. Here,
an upper deck 131 of the outdoor heat exchanger module 129 is
generally solid. A fan orifice 133 receives a cap 134. Heat
exchangers 130 thus are exposed to sufficiently reduced amount of
water, since the cap 134 tends to divert the rain water radially
outwardly and away from the heat exchangers 130. As shown in FIG.
6B, the cap 134 may be generally conical but other shapes or
configurations (e.g. pyramidal) are also acceptable. FIG. 6C is a
top view of the cap 134. Furthermore, the cap 134 may be formed of
a wire mesh, perforated plate or the like, with sufficient porosity
not to impede airflow provided by a fan 136 and small cell size
preventing water to drain through the cap 134. On the other hand,
the cap 134 may be made of solid material, and the airflow provided
by the fan 136 will escape through the gap between the cap 134 and
the upper deck 131.
[0031] The refrigerant systems that utilize this invention can be
used in many different applications, including, but not limited to,
air conditioning systems, heat pump systems, marine container
units, refrigeration truck-trailer units, and supermarket
refrigeration systems. Also, although the invention is described in
reference to microchannel heat exchangers and outdoor applications,
such as condensers and gas coolers, it can be applicable to other
heat exchanger types, such as round tube and plate fin heat
exchangers, and indoor applications, such as reheat heat exchangers
and evaporators. Furthermore, although the invention is described
in reference to slanted heat exchanger configuration with
horizontal tube orientation, it can be applied to vertical
arrangements with either vertical or horizontal tube
orientation.
[0032] Although an embodiment of this invention has been disclosed,
a worker of ordinary skill in this art would recognize that certain
modifications would come within the scope of this invention. For
that reason, the following claims should be studied to determine
the true scope and content of this invention.
* * * * *