U.S. patent application number 12/710994 was filed with the patent office on 2010-08-26 for wicking condensate evaporator for an air conditioning system.
This patent application is currently assigned to THE REGENTS OF THE UNIVERSITY OF CALIFORNIA. Invention is credited to Richard C. Bourne, Siva Gangadhar Gunda, Mark P. Modera, Theresa E. Pistochini.
Application Number | 20100212346 12/710994 |
Document ID | / |
Family ID | 42629714 |
Filed Date | 2010-08-26 |
United States Patent
Application |
20100212346 |
Kind Code |
A1 |
Bourne; Richard C. ; et
al. |
August 26, 2010 |
WICKING CONDENSATE EVAPORATOR FOR AN AIR CONDITIONING SYSTEM
Abstract
One embodiment of the present invention provides an air
conditioning (AC) system that evaporates its own condensate. This
AC system includes a condenser coil and an evaporator coil that
produces condensate. The AC system also includes a
wicking-evaporative device that is configured to wick and evaporate
the condensate in the vicinity of the condenser coil.
Inventors: |
Bourne; Richard C.; (Davis,
CA) ; Modera; Mark P.; (Piedmont, CA) ;
Pistochini; Theresa E.; (West Sacramento, CA) ;
Gunda; Siva Gangadhar; (Davis, CA) |
Correspondence
Address: |
PARK, VAUGHAN & FLEMING LLP
2820 FIFTH STREET
DAVIS
CA
95618-7759
US
|
Assignee: |
THE REGENTS OF THE UNIVERSITY OF
CALIFORNIA
Oakland
CA
|
Family ID: |
42629714 |
Appl. No.: |
12/710994 |
Filed: |
February 23, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61154720 |
Feb 23, 2009 |
|
|
|
Current U.S.
Class: |
62/281 ;
165/104.26; 62/291 |
Current CPC
Class: |
F28D 5/00 20130101; F24F
13/222 20130101; F28F 17/005 20130101; F24F 2013/225 20130101; F24F
1/022 20130101; F24F 2013/227 20130101 |
Class at
Publication: |
62/281 ;
165/104.26; 62/291 |
International
Class: |
F25D 21/14 20060101
F25D021/14; F28D 15/04 20060101 F28D015/04 |
Claims
1. An air conditioning (AC) system, comprising: a condenser coil;
an evaporator coil which produces condensate; and a
wicking-evaporative device configured to wick and evaporate the
condensate in the vicinity of the condenser coil.
2. The AC system of claim 1, wherein the AC system further includes
a tray system configured to collect the condensate.
3. The AC system of claim 2, wherein the tray system is positioned
at the base of the condenser coil and distributes the condensate
laterally along the width of the condenser coil.
4. The AC system of claim 2, wherein the wicking-evaporative device
includes a first material which wicks the condensate upward from
the tray system.
5. The AC system of claim 4, wherein the wicking-evaporative device
is positioned in the tray system such that a lower portion of the
first material is immersed in the condensate.
6. The AC system of claim 5, wherein the wicking-evaporative device
is positioned such that an upper portion of the first material is
disposed upward above the surface of the condensate, and wherein
the condensate is wicked from the lower portion of the first
material to the upper portion of the first material.
7. The AC system of claim 6, wherein the upper portion of the first
material is positioned in front of the condenser coil.
8. The AC system of claim 6, wherein the upper portion of the first
material is positioned in the path of an airflow which is directed
toward the condenser coil, and wherein the airflow facilitates
evaporating the condensate which is wicked into the upper portion
of the first material.
9. The AC system of claim 4, wherein the first material is
constructed into a set of spaced wicking sheets which are arranged
laterally along the width of the condenser coil.
10. The AC system of claim 4, wherein the first material is
configured so that its dimension perpendicular to the condenser
coil is greater than the height of the first material.
11. The AC system of claim 4, wherein the first material is a
wicking material.
12. The AC system of claim 11, wherein the first material is a
polyvinyl alcohol (PVA)-based material.
13. The AC system of claim 11, wherein the wicking material is made
of wicking fibers.
14. The AC system of claim 13, wherein the wicking fibers are
oriented upward from the tray system.
15. The AC system of claim 14, wherein pore sizes of the wicking
fibers decrease with distance away from the tray system.
16. The AC system of claim 4, wherein the first material is
configured to wick the condensate at a rate substantially equal to
a maximum expected condensation rate at the evaporator coil.
17. The AC system of claim 4, wherein the first material is
configured to reduce airflow resistance through the
wicking-evaporative device.
18. The AC system of claim 4, wherein the wicking-evaporative
device includes a second material which distributes the condensate
laterally along the width of the condenser coil.
19. The AC system of claim 18, wherein the wicking-evaporative
device is positioned in the tray system such that a lower portion
of the second material is immersed in the condensate.
20. The AC system of claim 18, wherein the wicking-evaporative
device is positioned in the tray system such that the second
material is located entirely above the surface of the condensate in
the tray system.
21. The AC system of claim 18, wherein the wicking-evaporative
device is positioned such that an upper portion of the second
material is disposed upward and positioned in front of the
condenser coil.
22. The AC system of claim 21, wherein the upper portion of the
second material is positioned in the path of an airflow which is
directed toward the condenser coil, and wherein the airflow
facilitates evaporating the condensate which is spread into the
upper portion of the second material.
23. The AC system of claim 18, wherein the second material includes
evaporative media.
24. The AC system of claim 18, wherein the evaporative media
include corrugated paper.
25. The AC system of claim 18, wherein the second material is
configured to distribute the condensate laterally at a rate
substantially equal to a maximum expected condensation rate.
26. The AC system of claim 18, wherein the second material is
configured to reduce airflow resistance through the
wicking-evaporative device.
27. The AC system of claim 18, wherein the first material is
distributed in a uniform pattern within the second material.
28. The AC system of claim 18, wherein the wicking-evaporative
device is constructed into alternating layers, wherein a pair of
adjacent layers includes a first layer made of the first material
and a second layer made of the second material, and wherein the
first layer and the second layer are in contact with each
other.
29. The AC system of claim 18, wherein the first material is
interspersed with the second material.
30. The AC system of claim 18, wherein a combination of the first
material and the second material is configured to minimize airflow
resistance.
31. The AC system of claim 18, wherein the first material and the
second material are the same type of material.
34. The AC system of claim 2, wherein the tray system has a
capacity substantially equal to a maximum expected volume of
surplus water accumulated when a condensation rate at the
evaporator coil exceeds an evaporation rate at the
wicking-evaporative device.
35. The AC system of claim 1, wherein the wicking-evaporative
device is configured to wick the condensate at an angle which is
within a range from the vertical direction and the horizontal
direction.
36. The AC system of claim 1, wherein evaporating the condensate in
the vicinity of the condenser coil facilitates cooling the
condenser coil.
37. The AC system of claim 1, wherein evaporating the condensate in
the vicinity of the condenser coil eliminates a need for piping to
drain the condensate away from the AC system.
38. A method for removing condensate collected from an evaporator
coil within an air conditioning (AC) system, comprising: wicking
the condensate upward into evaporative media which is positioned in
the path of an airflow directed toward a condenser coil of the AC
system, wherein the evaporative media and the airflow facilitate
evaporating the condensate in the vicinity of the condenser coil,
thereby eliminating a need for piping to drain the condensate away
from the AC system.
Description
RELATED APPLICATION
[0001] This application hereby claims priority under 35 U.S.C.
.sctn.119 to U.S. Provisional Patent Application No. 61/154,720,
filed on 23 Feb. 2009, entitled "WICKING CONDENSATE EVAPORATOR AT
AC CONDENSER," by inventors Richard C. Bourne. (Attorney Docket No.
UC08-399-2PSP).
BACKGROUND
[0002] 1. Field of the Invention
[0003] The present invention generally relates to design of air
conditioning (AC) systems. More specifically, the present invention
relates to techniques for improving efficiency and reducing the
cost of AC-system installations by evaporating condensate at the AC
system's condenser coil.
[0004] 2. Related Art
[0005] Both residential and commercial air conditioning ("AC")
systems typically condense moisture on the cooling coil, known as
the system's evaporator (also referred to as the "evaporator
coil"). The resulting water, referred to as "condensate," is then
drained through pipes either to the ground, which is commonly done
in residential systems, or to a storm or sanitary drain system,
which is commonly done in commercial systems. Note that the
plumbing for draining of the condensate adds cost to each AC
system. However, if the condensate can be re-evaporated at the AC
system, the piping cost can be eliminated. Moreover, if such
evaporation takes place at the AC system's heat discharge coil,
also known as the "condenser coil," the energy consumption
associated with rejecting heat at the condenser coil, can be
reduced.
[0006] There are existing techniques for re-evaporating the AC
condensate at the condenser coil of an AC system. For example, one
technique uses a small pump placed below the condensate collection
pan to pump condensate through piping to the top of a drip-type
evaporative media. Another technique uses a device to create a
"mist" in an air stream which can be directed onto the condenser
coil without the need for evaporative media. However, both of these
existing techniques require electrical components and electrical
power to operate, and therefore introduce additional component
costs, the need for specialized electricians for field
installations, and associated maintenance and replacement
costs.
[0007] Hence, what is needed is a technique for re-evaporating the
AC condensate at the condenser coil of an AC system without the
above-described problems.
SUMMARY
[0008] One embodiment of the present invention provides an air
conditioning (AC) system that evaporates its own condensate. This
AC system includes a condenser coil and an evaporator coil that
produces condensate. The AC system also includes a
wicking-evaporative device that is configured to wick and evaporate
the condensate in the vicinity of the condenser coil.
[0009] In some embodiments, the AC system also includes a tray
system that is configured to collect the condensate.
[0010] In some embodiments, the tray system is positioned at the
base of the condenser coil and distributes the condensate laterally
along the width of the condenser coil.
[0011] In some embodiments, the wicking-evaporative device includes
a first material that wicks the condensate upward from the tray
system.
[0012] In some embodiments, the wicking-evaporative device is
positioned in the tray system such that a lower portion of the
first material is immersed in the condensate.
[0013] In some embodiments, the wicking-evaporative device is
positioned such that an upper portion of the first material is
disposed upward above the surface of the condensate, and the
condensate is wicked from the lower portion of the first material
to the upper portion of the first material.
[0014] In some embodiments, the upper portion of the first material
is positioned on the air inlet side of the condenser coil.
[0015] In some embodiments, the upper portion of the first material
is positioned in the path of an airflow that is directed toward the
condenser coil. Consequently, the airflow facilitates evaporating
the condensate that is wicked into the upper portion of the first
material.
[0016] In some embodiments, the first material is constructed into
a set of spaced wicking sheets which are arranged laterally along
the width of the condenser coil.
[0017] In some embodiments, the first material is configured so
that its dimension perpendicular to the condenser coil is greater
than the height of the first material.
[0018] In some embodiments, the first material is a wicking
material.
[0019] In some embodiments, the first material is a polyvinyl
alcohol (PVA)-based material.
[0020] In some embodiments, the wicking material is made of wicking
fibers.
[0021] In some embodiments, the wicking fibers are oriented upward
from the tray system.
[0022] In some embodiments, pore sizes of the wicking fibers
decrease with distance away from the tray system.
[0023] In some embodiments, the first material is configured to
wick the condensate at a rate substantially equal to a maximum
expected condensation rate at the evaporator coil.
[0024] In some embodiments, the first material is configured to
reduce airflow resistance through the wicking-evaporative
device.
[0025] In some embodiments, the wicking-evaporative device includes
a second material that distributes the condensate laterally along
the width of the condenser coil.
[0026] In some embodiments, the wicking-evaporative device is
positioned in the tray system such that a lower portion of the
second material is immersed in the condensate.
[0027] In some embodiments, the wicking-evaporative device is
positioned in the tray system such that the second material is
located entirely above the surface of the condensate in the tray
system.
[0028] In some embodiments, the wicking-evaporative device is
positioned such that an upper portion of the second material is
disposed upward and positioned in front of the condenser coil.
[0029] In some embodiments, the upper portion of the second
material is positioned in the path of an airflow which is directed
toward the condenser coil. Consequently, the airflow facilitates
evaporating the condensate which is spread into the upper portion
of the second material.
[0030] In some embodiments, the second material includes
evaporative media.
[0031] In some embodiments, the evaporative media include
corrugated paper.
[0032] In some embodiments, the second material is configured to
distribute the condensate laterally at a rate substantially equal
to a maximum expected condensation rate.
[0033] In some embodiments, the second material is configured to
reduce airflow resistance through the wicking-evaporative
device.
[0034] In some embodiments, the first material is distributed in a
uniform pattern within the second material.
[0035] In some embodiments, the wicking-evaporative device is
constructed into alternating layers, wherein a pair of adjacent
layers includes a first layer made of the first material and a
second layer made of the second material. The first layer and the
second layer are in contact with each other.
[0036] In some embodiments, the first material is interspersed with
the second material.
[0037] In some embodiments, a combination of the first material and
the second material is configured to minimize airflow
resistance.
[0038] In some embodiments, the first material and the second
material are the same type of material.
[0039] In some embodiments, the tray system includes a first tray
and a second tray that are interconnected but spaced apart from
each other. Further, the second material is positioned between the
first tray and the second tray, and the first material is
positioned to wick the condensate from both trays to the second
material.
[0040] In some embodiments, the second material is located entirely
above the highest water level in the first tray and the second
tray.
[0041] In some embodiments, the tray system has a capacity
substantially equal to a maximum expected volume of surplus water
accumulated when the condensation rate at the evaporator coil
exceeds the evaporation rate at the wicking-evaporative device.
[0042] In some embodiments, the wicking-evaporative device is
configured to wick the condensate at an angle that is within a
range from the vertical direction and the horizontal direction.
[0043] In some embodiments, evaporating the condensate in the
vicinity of the condenser coil facilitates cooling the condenser
coil.
[0044] In some embodiments, evaporating the condensate in the
vicinity of the condenser coil eliminates a need for piping to
drain the condensate away from the AC system.
[0045] One embodiment of the present invention provides a
wicking-evaporative device for removing condensate collected from
an evaporator coil within an AC system. During operation, the
wicking-evaporative device wicks the condensate upward into
evaporative media that is positioned in the path of an airflow
directed toward a condenser coil of the AC system. Next, the
evaporative media and the airflow facilitate evaporating the
condensate in the vicinity of the condenser coil, thereby
eliminating the need for piping to drain the condensate away from
the AC equipment.
BRIEF DESCRIPTION OF THE FIGURES
[0046] FIG. 1 presents a schematic illustrating an air conditioning
(AC) system which pipes the condensate to drain.
[0047] FIG. 2 presents a schematic illustrating a cross-section of
an AC system which re-evaporates condensate in accordance with an
embodiment of the present invention.
[0048] FIG. 3 illustrates a 3-dimensional (3D) model of the
wicking-evaporative device in accordance with an embodiment of the
present invention.
[0049] FIG. 4A illustrates a cross-section in the horizontal
direction of an exemplary design of the wicking-evaporative device
based on a single wicking material in accordance with an embodiment
of the present invention.
[0050] FIG. 4B illustrates a cross-section in the vertical
direction of the exemplary design in FIG. 4A wherein wicking
material 402 is shown in the form of wicking sheets.
[0051] FIG. 5A illustrates a cross-section in the horizontal
direction of an exemplary design of the wicking-evaporative device
which uses a first material for wicking condensate in the vertical
direction and a second material for spreading condensate in the
lateral direction in accordance with an embodiment of the present
invention.
[0052] FIG. 5B illustrates a cross-section of another design of the
wicking-evaporative device based on the first material and the
second material in accordance with an embodiment of the present
invention.
[0053] FIG. 6 illustrates a cross-section in the vertical direction
(top-view) of an exemplary design of the wicking-evaporative device
based on a single or two-material wicking material in accordance
with an embodiment of the present invention.
[0054] FIG. 7 illustrates an exemplary configuration of a tray and
a wicking-evaporative device in an AC system in accordance with an
embodiment of the present invention.
DETAILED DESCRIPTION
[0055] The following description is presented to enable any person
skilled in the art to make and use the embodiments, and is provided
in the context of a particular application and its requirements.
Various modifications to the disclosed embodiments will be readily
apparent to those skilled in the art, and the general principles
defined herein may be applied to other embodiments and applications
without departing from the spirit and scope of the present
disclosure. Thus, the present invention is not limited to the
embodiments shown, but is to be accorded the widest scope
consistent with the principles and features disclosed herein.
[0056] Some embodiments of the present invention provide
wicking-evaporation techniques for re-evaporating AC condensate at
the condenser coil of an AC system. The present techniques do not
require electrical components or electrical energy to operate, thus
eliminating the cost of a motorized component, the cost of
specialized electrician labor for installation, and the maintenance
and replacement costs associated with an electrical device.
[0057] More specifically, some embodiments of the present invention
dispose wicking-evaporative media within a portion of the condenser
airflow at the bottom of the condenser coil. Furthermore, a tray is
provided which supports or contacts the lower edge of the
wicking-evaporative media, and the bottom of the tray is positioned
lower than the drain line from the condensate collection pan at the
evaporator side. The condensate is then piped to the tray, and
wicked upward through the wicking-evaporative media to evaporate
into the condenser airflow.
[0058] FIG. 1 presents a schematic illustrating an air conditioning
(AC) system 100 which pipes the condensate to drain.
[0059] AC system 100, for example a rooftop AC unit, includes a
compressor 102, a condenser 104, an expansion valve 106, and an
evaporator 108. These components are connected by tubing to form a
loop through which a refrigerant circulates during a cooling
cycling. Typically, a refrigerant enters compressor 102 in a vapor
form and exits compressor 102 as superheated vapor. This
superheated vapor travels through condenser 104 which condenses the
vapor into a liquid; in doing so, the heat is transferred to
condenser 104. The liquid refrigerant enters expansion valve 106
which causes a portion of the liquid to vaporize. This creates a
mixture of liquid and vapor at a cooler temperature. The cold
liquid-vapor mixture then travels through the evaporator coil of
evaporator 108 and is substantially vaporized by cooling the warm
air being blown through evaporator 108. This process additionally
condenses moisture from the warm air onto the evaporator coil to
form condensate. The resulting refrigerant vapor returns to
compressor 102 to complete a cooling cycle and start the next
cooling cycle. Note that the condensate is drained through piping
110 either to the ground or away from AC system 100.
[0060] FIG. 2 presents a schematic illustrating a cross-section of
an AC system 200 which re-evaporates the condensate in accordance
with an embodiment of the present invention.
[0061] As illustrated in FIG. 2, a vertical direction 202
represents the upward direction along the height of AC system 200,
and a horizontal direction 204 represents the direction of airflow
of incoming air 211 (i.e., the air inlet to the condenser) which is
used to cool condenser coil 210 (from right to left in this case).
A third direction, referred to as "lateral direction" 206, is
perpendicular to the paper and parallel to the width of AC system
200 and the width of condenser coil 210 (not shown). Although not
shown, condenser coil 210 typically has an extended profile in
lateral direction 206. Note that the above definitions for the
three directions are also used throughout the discussion below when
a same-named direction is referred.
[0062] AC system 200 also includes an evaporator coil 208, a
condenser coil 210 and a housing 203. Evaporator coil 208 is
located at the far left of housing 203 and is open to both the air
flows inside of AC system 200 and outside of AC system 200. During
operation, warm air 205 which is driven by fan 207 flows from right
to left onto evaporator coil 208, while cool air 209 flows from
right to left out of evaporator coil 208 to cool a space outside of
AC system 200. Condenser coil 210 is located at the far right of
housing 203 and is open to both the air flows inside of AC system
200 and outside of AC system 200. As is mentioned above, condenser
coil 210 also has an extended width in lateral direction 206.
During operation, incoming air 211 from outside of AC system 200
flows from right to left through condenser coil 210 to cool the
condenser coil. This incoming air flow may be caused by a lower
pressure created within AC system 200. Typically, incoming air 211
becomes exhaust air 213 after passing through condenser coil 210
and is vented out of AC system 200. Note that some of the AC system
components, such as the compressor and the expansion valve, are not
shown in FIG. 2.
[0063] AC system 200 also includes a condensate-collection
mechanism 214 which collects condensate at evaporator coil 208.
Embodiments of the present invention also provide a tube 215 which
guides the condensate from evaporator coil 208 into tray 216. As
illustrated in FIG. 2, tray 216 is placed at the base of condenser
coil 210 and is configured to hold condensate 218. Note that tube
215 may guide the flow of the condensate through gravity. For
example, tube 215 may be angled slightly downward from the
evaporator side to the condenser side. In some embodiments, instead
of using a tube, an open channel or a pan may be used to guide the
condensate into tray 216. Note that, while different designs of a
guiding mechanism may be used in place of tube 215, no power is
required to drain the condensate into tray 216.
[0064] Note that in other embodiments tray 216 may be alternatively
implemented as any type of water container which has an opening.
Moreover, a single tray 216 may be replaced by two or more
interconnected trays to increase condensate-collection capacity. In
some embodiments, a condensate-collection tray can also be placed
at the base of evaporation coil 208 between condensate-collection
mechanism 214 and tube 215. However, in these embodiments, the
bottom of tray 216 may need to be positioned lower than the drain
line of the condensate-collection tray at the evaporator side.
[0065] In some embodiments, tray 216 is sized to collect the
maximum expected volume of condensate without spilling. This
maximum expected volume may be measured at conditions when the
condensation rate at the evaporator coil exceeds a current
evaporative capability. For example, such conditions can occur when
warm air 205 has a high humidity and temperature, which leads to a
high condensation rate and a surplus of water flowing into tray
216. In some embodiments, a simulation tool may be used to predict
a condensation rate at the evaporator coil based on both indoor and
outdoor conditions.
[0066] While FIG. 2 illustrates tray 216 as separate from housing
203, in some embodiments, tray 216 may be integrated with housing
203. Moreover, while FIG. 2 illustrates tray 216 as outside of
housing 203, in some embodiments, tray 216 may be placed partially
or entirely inside housing 203 within a space between condenser
coil 210 and the bottom of housing 203.
[0067] Note that, while FIG. 2 provides a cross-section view of
tray 216, tray 216 also has a width in lateral direction 206. In
some embodiments, the width of tray 216 is substantially equal to
the width of condenser coil 210 in lateral direction 206. Note that
in these embodiments tray 216 evenly distributes condensate 218 in
lateral direction 206 along the width of condenser coil 210.
[0068] Some embodiments of the present invention also provide a
wicking-evaporative device 220. As illustrated in FIG. 2,
wicking-evaporative device 220 is positioned such that a lower
portion of wicking-evaporative device 220 is placed within tray 216
and the remainder of wicking-evaporative device 220 is disposed
upward into the air stream of incoming air 211. Hence,
wicking-evaporative device 220 is also partially immersed in
condensate 218. Note that while wicking-evaporative device 220 is
shown to be in contact with the bottom of tray 216, other
embodiments can also have wicking-evaporative device 220 suspended
in condensate 218. This can be achieved by affixed
wicking-evaporative device 220 onto to the sidewalls of tray
216.
[0069] In one embodiment, wicking-evaporative device 220 is
configured to wick condensate 218 upward from a lower portion of
wicking-evaporative device 220 into an upper portion of
wicking-evaporative device 220, which is positioned in the path of
incoming air 211. The effect of wicking is indicated by a arrow 222
pointing at the highest level of the wicked-up condensate. As shown
in FIG. 2, the wicked-up condensate is directly in the path of
incoming air 211, which facilitates evaporation of the wicked-up
condensate into water vapor. Because wicking-evaporative device 220
allows incoming air 211 to flow through, the water vapor moves
along with incoming air 211 onto condenser coil 210 (and the fins
of the condenser), helping to cool condenser coil 210 in the
process. Additionally, after taking part in the evaporation
process, incoming air 211 is further cooled down when reaching
condenser coil 210. Consequently, the efficiency of incoming air
211 in cooling condenser coil 210 can be significantly
increased.
[0070] Note that some embodiments of the present invention take
advantage of the existing cooling airflow of a conventional AC
system to facilitate evaporation of the condensate. Therefore, the
condensate evaporation and the improved cooling efficiency are
acquired without requiring additional electrical power. Although
evaporation of the condensate as a result of direct heat radiation
from the hot condenser coil may be a lesser effect, it can also
contribute to the overall evaporation rate of condensate 218. The
evaporation rate due to this effect may be further increased by
reducing the distance between condenser coil 210 and
wicking-evaporative device 220. In some embodiments,
wicking-evaporative device 220 and condenser coil 210 are in direct
contact with each other.
[0071] Note that, when AC system 200 is in normal operation, the
above-described process of condensate collection into tray 216, the
process of condensate wicking, and the process of condensate
evaporation become automatic and can occur indefinitely without
requiring additional electrical power. In other words, the
condensation wicking-evaporating process of the present invention
becomes an integral part of the cooling cycles of AC system
200.
[0072] FIG. 3 illustrates a 3-dimensional (3D) model of
wicking-evaporative device 220 in accordance with an embodiment of
the present invention. In this simplified model,
wicking-evaporative device 220 may be represented by a plate
structure associated with a height 302 in the vertical direction, a
thickness 304 in the horizontal direction, and a width 306 in the
lateral direction. Note that each direction in FIG. 3 has the same
meaning as a corresponding direction with the same name in FIG. 2.
Also, FIG. 3 is understood and discussed in conjunction with FIG.
2.
[0073] Typically, height 302 of wicking-evaporative device 220 is
designed so that at least an upper portion of wicking-evaporative
device 220 is positioned in the path of incoming air 211. As a
result, at least a portion of incoming air 211 first blows through
wicking-evaporative device 220 before reaching condenser coil 210
behind wicking-evaporative device 220. Generally, the top of
wicking-evaporative device 220 may be designed to be anywhere
between the top and bottom of the condenser coil 210.
[0074] In the horizontal direction, wicking-evaporative device 220
is designed to allow incoming air 211 to flow through. In some
embodiments, wicking-evaporative device 220 has a structure in the
horizontal direction which facilitates minimizing the pressure drop
of incoming air 211 through the device, in other words, providing a
least airflow resistance in that direction. Consequently, thickness
304 of wicking-evaporative device 220 along the horizontal
direction is typically much smaller than its height 302 and width
306.
[0075] In the lateral direction, wicking-evaporative device 220 is
designed to have a width to facilitate wicking up a maximum volume
of the condensate. In some embodiments, width 306 may be comparable
to the width of tray 216 or condenser coil 210.
[0076] Although FIG. 3 models wicking-evaporative device 220 as a
single continuous structure, some embodiments may use two or more
laterally isolated plate structures in the lateral direction,
wherein each plate structure only occupies a portion of the full
tray length. Also note that, while the model for
wicking-evaporative device 220 is shown with a uniform box
structure, some embodiments may construct wicking-evaporative
device 220 in other geometries. For example, instead of
constructing a rectangular cross-section in the lateral direction,
this cross-section may be constructed in a trapezoidal shape with
the top edge narrower than the bottom edge.
[0077] In some embodiments, wicking-evaporative device 220 is
formed by at least a wicking material which is responsible for the
wicking action of wicking-evaporative device 220. More
specifically, the wicking material is partially immersed in the
condensate in the tray, and is configured to wick water from the
tray upward toward the top of wicking-evaporative device 220 and
into the path of incoming air 211. Generally, any material that is
capable of moving water through capillary action can be used as the
wick material in wicking-evaporative device 220. For example, a
polyvinyl alcohol (PVA)-based material can be used as the wicking
material. Such material can be made of hollow wicking fibers or
wicking tubes. Furthermore, the wick material can be made of a
single wick material or a composite wicking material containing two
or more types of wicking material.
[0078] In some embodiments, designing wicking-evaporative device
220 involves attempting to achieve the follow objectives: (1)
maximizing the evaporation rate; and (2) minimizing air flow
resistance. Note that to achieve the first objective one can
attempt to maximize the vertical wicking rate of the wicking
material and/or to maximize surface area of wicking-evaporative
device 220 which faces incoming air 211.
[0079] FIG. 4A illustrates a cross-section in the horizontal
direction of an exemplary design of wicking-evaporative device 220
based on a single wicking material 402 in accordance with an
embodiment of the present invention. In the design of FIG. 4A,
wicking material 402 is constructed as an array of long wicking
tubes arranged along the width of wicking-evaporative device 220,
wherein each wicking tube is oriented upward along the vertical
direction. In one embodiment, the array of wicking tubes is affixed
within a frame 408.
[0080] In this design, the wicking tubes are separated by spaces to
allow incoming air to flow through. This is necessary because the
wicking tubes themselves may have large airflow resistance. Note
that, while wicking material 402 can be represented as wicking
tubes in the cross-section view, it is typically made into wicking
sheets in the horizontal direction so that wicking material 402
occupies the full thickness of wicking-evaporative device 220 in
that direction. FIG. 4B illustrates a cross-section in the vertical
direction of the exemplary design in FIG. 4A wherein wicking
material 402 is shown as wicking sheets. Hence, we use the term
"wicking tubes" to specifically refer to the cross-section of the
wicking sheets in the horizontal direction.
[0081] Referring back to FIG. 4A, note that to maximize the
vertical wicking rate one can choose one or more of the following
strategies: (1) using a greater number of wicking tubes; and/or (2)
using wicking tubes with larger pore sizes. However, both of these
strategies also reduce air gaps between the wicking tubes, which
can lead to a higher airflow resistance of wicking material 402.
Therefore, there is a trade-off between maximizing the wicking rate
and minimizing airflow resistance for the design of FIG. 4A.
[0082] In some embodiments, instead of attempting to achieve a
maximum wicking rate, wicking material 402 is configured to only
wick water at a maximum expected condensation rate. In these
embodiments, the system ensures that wicking and evaporation can
generally exceed the condensation rate while avoiding using
excessive wicking material.
[0083] While FIG. 4A illustrates wicking tubes having uniform pore
sizes, some embodiments can use wicking tubes with varying pore
sizes. Typically, large pore sizes facilitate wicking a greater
volume of water but do not support a large wicking height in the
vertical direction. On the other hand, small pore sizes facilitate
increasing wicking height but tend to wick a lesser volume of
water. Hence, one can build the wicking tubes wherein the pore
sizes vary as a function of height. For example, each wicking tube
can have a gradually shrinking pore size from the bottom of the
wicking tube to the top of the wicking tube. Such a design may
allow more condensate to be wicked to a greater wicking height.
[0084] Note that FIG. 4A includes a line marking 404 which
represents the top water level in the tray. FIG. 4A also includes a
line marking 406 which represents the highest level of the
wicked-up condensate due to the effect of wicking material 402.
However, the position of line marking 406 can change as a result of
a number of factors. These factors can include, but are not limited
to: temperature, humidity, volume of condensate in the tray, and
the type and structure of the wicking material 402. While wicking
material 402 is responsible for distributing the condensate in the
vertical direction, the wicking material itself may not be capable
of evaporating the wicked-up condensate efficiently.
[0085] FIG. 5A illustrates a cross-section in the horizontal
direction of an exemplary design of wicking-evaporative device 220
which uses a first material for wicking condensate in the vertical
direction and a second material for spreading condensate in the
lateral direction in accordance with an embodiment of the present
invention. More specifically, wicking-evaporative device 220
comprises an array of long wicking sheets 502 (in the 3D structure)
which are made of a first material. Wicking sheets 502 are
partially submerged in the condensate (line marking 504 indicates
the top water level in the tray) and wick the condensate in the
vertical direction.
[0086] Wicking-evaporative device 220 also comprises, within the
spacing between a pair of wicking sheets 502, evaporative media 506
which are made of a second material. Note that evaporative media
506 have a corrugate structure and hence a very large surface area.
The corrugated structure of evaporative media 506 also facilitates
making multiple contacts with adjacent wicking sheets 502. In doing
so, evaporative media 506 draw water from wicking sheets 502 and
distribute the water laterally in the spaces between wicking sheets
502. As a result, the combined structure of wicking sheets 502 and
evaporative media 506 creates a much larger surface area for
distributing the condensate as compared to the design in FIG. 4A.
The large surface area of the resulting wicking-evaporative device
220 significantly increases the evaporation rate when such a device
is installed in an AC system. Furthermore, because the corrugated
structure of evaporative media 506 is configured to have a low
airflow resistance, this design facilitates achieving both maximum
evaporation and minimum airflow resistance at the same time. In one
embodiment, wicking sheets 502 and evaporative media 506 are
securely attached onto a frame 507.
[0087] The second material of evaporative media 506 can include
both a wicking material and a non-wicking material. If the second
material is a wicking material, it can be the same type of material
as the first material. In one embodiment, the second material is a
CELdek.TM. evaporative media. In another embodiment, evaporative
media 506 is made of corrugated paper.
[0088] In the design of FIG. 5A, evaporative media 506 have the
same height as wicking sheets 502, and therefore are also partially
submerged in the condensate. In this design, evaporative media 506
can provide limited vertical wicking action but are not the main
wicking media. FIG. 5B illustrates a cross-section of another
design of wicking-evaporative device 220 based on the first
material and the second material in accordance with an embodiment
of the present invention. In this embodiment, evaporative media 508
are shorter in height than wicking sheets 510. When placed in a
condensate tray, wicking sheets 510 are partially submerged in the
water but evaporative media 508 remain above the highest level of
the condensate in the tray (line marking 512 indicates the top
water level in the tray) and hence do not make direct contact with
the condensate in the tray. Consequently, in this embodiment
evaporative media 508 are primarily used for distributing the
concentrate in the lateral direction.
[0089] While FIG. 5A and FIG. 5B illustrate two embodiments of
interspersing the first material with the second material to form
the wicking-evaporative device 220, other embodiments of the
present invention may provide other configurations for
interspersing the first material with the second material to form
wicking-evaporative device 220. Hence, the present invention is not
limited to the specific ways of interspersing the first material
with the second material illustrated in FIG. 5A and FIG. 5B.
[0090] FIG. 6 illustrates a cross-section in the vertical direction
(i.e., the top-view) of an exemplary design of wicking-evaporative
device 220 based on a single or two-material wicking material in
accordance with an embodiment of the present invention.
[0091] In the embodiment of FIG. 6, wicking-evaporative device 220
includes a series of wicking sheets 602 which are arranged in a
zigzag pattern from the cross-section view, and attached into a
frame 604. Moreover, wicking sheets 602 have an extended profile in
both the lateral direction and the horizontal direction. For
example, in the horizontal direction (i.e., the vertical direction
on the page), the profile of wicking sheets 602 is significantly
larger than the profile of wicking material 402 in FIG. 4A. The
result of this design creates a large surface area which faces
incoming air 606. Hence, wicking sheets 602 serve both wicking and
evaporative functions. Because wicking sheets 602 provide more
wicking and evaporative area, it is possible to build wicking
sheets 602 with a lower height, such that wicking sheets 602 only
reach the lower portion of the condenser coil.
[0092] In some embodiments, wicking sheets 602 are arranged to
facilitate directing the air blowing through wicking sheets 602 to
the condenser coil. In one embodiment, wicking sheets 602 are made
of a single wicking material, such as PVA. Note that
wicking-evaporative device 220 is placed in a condensate tray 608
which has a large bottom profile to accommodate wicking-evaporative
device 220. Also note that the design of FIG. 6 is for illustration
purposes, and other embodiments may have different numbers of
wicking sheets, different angles between adjacent wicking sheets,
and different width-to-thickness ratios of wicking-evaporative
device 220.
[0093] FIG. 7 illustrates an exemplary configuration of a tray 702
and a wicking-evaporative device 704 in an AC system 700 in
accordance with an embodiment of the present invention. In the
embodiment of FIG. 7, wicking-evaporative device 704 is oriented at
an angle with the vertical direction. Because the wicking fibers in
wicking-evaporative device 704 are typically oriented along the
orientation of wicking-evaporative device 704, the wicking action
in wicking-evaporative device 704 follows the orientation of
wicking-evaporative device 704 rather than the vertical direction.
Note that this assembly is useful when the orientation of the
condenser coil 706 in AC system 700 is tilted, as shown in FIG. 7.
Generally, wicking-evaporative device 704 can be oriented in any
tilt angle between the vertical direction and the horizontal
direction so that the wicking action can also occur at that
angle.
[0094] Embodiments of the present invention can be used in any type
of residential or commercial AC system. One such application is in
the estimated >4,000,000 rooftop cooling units (RTUs) which are
commonly used to cool non-residential buildings.
[0095] The foregoing descriptions of various embodiments have been
presented only for purposes of illustration and description. They
are not intended to be exhaustive or to limit the present invention
to the forms disclosed. Accordingly, many modifications and
variations will be apparent to practitioners skilled in the art.
Additionally, the above disclosure is not intended to limit the
present invention.
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