WO2010096825A2

WO2010096825A2 - A wicking condensate evaporator for an air conditioning system

Info

Publication number: WO2010096825A2
Application number: PCT/US2010/025094
Authority: WO
Inventors: Richard C. Bourne; Mark P. Modera; Theresa Pistochini; Siva Gunda
Original assignee: The Regents Of The University Of California
Priority date: 2009-02-23
Filing date: 2010-02-23
Publication date: 2010-08-26
Also published as: WO2010096825A3; US20100212346A1

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.

Description

A WICKING CONDENSATE EVAPORATOR FOR AN AIR CONDITIONING SYSTEM

Inventors: Richard C. Bourne, Mark P. Modera, Theresa Pistochini, and Siva Gunda

BACKGROUND

Field of the Invention

[0001] 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.

Related Art

[0002] 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.

[0003] 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.

[0004] 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 [0005] 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. [0006] In some embodiments, the AC system also includes a tray system that is configured to collect the condensate.

[0007] 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.

[0008] In some embodiments, the wicking-evaporative device includes a first material that wicks the condensate upward from the tray system.

[0009] 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.

[0010] 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.

[0011] In some embodiments, the upper portion of the first material is positioned on the air inlet side of the condenser coil.

[0012] 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.

[0013] In some embodiments, the first material is constructed into a set of spaced wi eking sheets which are arranged laterally along the width of the condenser coil.

[0014] 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.

[0015] In some embodiments, the first material is a wicking material.

[0016] In some embodiments, the first material is a polyvinyl alcohol (PVA)-based material.

[0017] In some embodiments, the wicking material is made of wicking fibers. [0018] In some embodiments, the wicking fibers are oriented upward from the tray system.

[0019] In some embodiments, pore sizes of the wicking fibers decrease with distance away from the tray system.

[0020] 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.

[0021] In some embodiments, the first material is configured to reduce airflow resistance through the wicking-evaporative device.

[0022] In some embodiments, the wicking-evaporative device includes a second material that distributes the condensate laterally along the width of the condenser coil. [0023] 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.

[0024] 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. [0025] 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.

[0026] 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.

[0027] In some embodiments, the second material includes evaporative media.

[0028] In some embodiments, the evaporative media include corrugated paper.

[0029] In some embodiments, the second material is configured to distribute the condensate laterally at a rate substantially equal to a maximum expected condensation rate.

[0030] In some embodiments, the second material is configured to reduce airflow resistance through the wicking-evaporative device.

[0031] In some embodiments, the first material is distributed in a uniform pattern within the second material. [0032] 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.

[0033] In some embodiments, the first material is interspersed with the second material. [0034] In some embodiments, a combination of the first material and the second material is configured to minimize airflow resistance.

[0035] In some embodiments, the first material and the second material are the same type of material.

[0036] 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.

[0037] In some embodiments, the second material is located entirely above the highest water level in the first tray and the second tray. [0038] 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.

[0039] 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. [0040] In some embodiments, evaporating the condensate in the vicinity of the condenser coil facilitates cooling the condenser coil.

[0041] 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. [0042] 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

[0043] FIG. 1 presents a schematic illustrating an air conditioning (AC) system which pipes the condensate to drain.

[0044] 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.

[0045] FIG. 3 illustrates a 3-dimensional (3D) model of the wicking-evaporative device in accordance with an embodiment of the present invention. [0046] 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.

[0047] 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. [0048] FIG. 5 A 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. [0049] 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.

[0050] 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.

[0051] 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

[0052] 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.

[0053] 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.

[0054] 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. [0055] FIG. 1 presents a schematic illustrating an air conditioning (AC) system 100 which pipes the condensate to drain. [0056] 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. [0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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. [0063] 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.

[0064] 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.

[0065] 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. [0066] 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.

[0067] 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.

[0068] Note that, when AC system 200 is in normal operation, the above-described process of condensate collection into tray 216, the process of condensate wi eking, 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.

[0069] 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. [0070] 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. [0071] 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.

[0072] 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. [0073] 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.

[0074] 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.

[0075] 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 wi eking rate of the wicking material and/or to maximize surface area of wicking-evaporative device 220 which faces incoming air 211.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] FIG. 5 A 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.

[0083] 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.

[0084] The second material of evaporative media 506 can include both a wicking material and a no n- 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™ evaporative media. In another embodiment, evaporative media 506 is made of corrugated paper.

[0085] In the design of FIG. 5 A, 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.

[0086] 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.

[0087] 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. [0088] 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.

[0089] 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.

[0090] 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. [0091] 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.

[0092] 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.

Claims

What Is Claimed Is:

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 wi eking 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.

32. The AC system of claim 18, wherein the tray system includes a first tray and a second tray which are interconnected but spaced apart from each other, and wherein 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.

33. The AC system of claim 32, wherein the second material is located entirely above the highest water level in the first tray and the second tray.

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.

39. The method of claim 38, wherein prior to wicking the condensate, the method further comprises draining the condensate into a tray system.

40. The method of claim 39, wherein wicking the condensate involves wicking the condensate from the tray system.

41. The method of claim 39, wherein the method further comprises installing the tray system at the base of the condenser coil, and wherein the tray system distributes the condensate laterally along the width of the condenser coil.

42. The method of claim 39, wherein the tray system has a capacity which is substantially equal to a maximum expected volume of surplus water accumulated when the condensation at the evaporator coil exceeds the evaporation of the evaporative media.

43. The method of claim 38, wherein the method further comprises predicting a condensation rate at the evaporator coil based on both indoor and outdoor conditions.

44. The method of claim 38, wherein wicking the condensate involves disposing a wicking material in the tray system such that a lower portion of the wicking material is immersed in the condensate.

45. The method of claim 44, wherein the method further comprises positioning the wicking material so that an upper portion of the wicking material is disposed upward above the surface of the condensate, and the condensate is wicked from the lower portion of the wicking material to the upper portion of the wicking material.

46. The method of claim 45, wherein the upper portion of the wicking material is positioned on the air inlet side of the condenser coil and in contact with the evaporative media.

47. The method of claim 45, wherein the upper portion of the wicking material is part of the evaporative media.

48. The method of claim 45, wherein the method further comprises constructing the wicking material into a set of spaced wicking sheets which are arranged laterally along the width of the condenser coil.

49. The method of claim 45, wherein the wicking material is configured so that its dimension perpendicular to the condenser coil is greater than the height of the wicking material.

50. The method of claim 45, wherein the wicking material is a polyvinyl alcohol (PVA)-based material.

51. The method of claim 45, wherein the wicking material is made of wicking fibers.

52. The method of claim 51 , wherein the wicking fibers are oriented upward from the tray system.

53. The method of claim 52, wherein pore sizes of the wicking fibers decrease with distance away from the tray system.

54. The method of claim 45, wherein the method further comprises configuring the wicking material to wick the condensate at a rate substantially equal to a maximum expected condensation rate at the evaporator coil.

55. The method of claim 45, wherein the method further comprises configuring the wicking material to reduce airflow resistance through the wicking material.

56. The method of claim 38, wherein the method further comprises configuring the evaporative media to distribute the condensate laterally along the width of the condenser coil.

57. The method of claim 56, wherein the method further comprises configuring the evaporative media to distribute the condensate laterally at a rate substantially equal to a maximum expected condensation rate.

58. The method of claim 38, wherein the method further comprises disposing the evaporative media so that a lower portion of the evaporative media is immersed in the condensate.

59. The method of claim 38, wherein the method further comprises disposing the evaporative media so that the evaporative media are located entirely above the surface of the condensate in the tray system.

60. The method of claim 38, wherein the evaporative media include corrugated paper.

61. The method of claim 38, wherein the method further comprises configuring the evaporative media to reduce airflow resistance through the evaporative media.

62. The method of claim 46, wherein the method further comprises configuring the wicking material in a uniform pattern within the evaporative media.

63. The AC system of claim 46, wherein the wicking material is interspersed with the evaporative media.

64. The method of claim 46, wherein the method further comprises combining the wicking material and the evaporative media to minimize airflow resistance.

65. The method of claim 46, wherein the wicking material and the evaporative media are made of the same type of material.

66. The method of claim 46, wherein the method further comprises configuring the tray system into a first tray and a second tray which are interconnected but spaced apart from each other, and wherein the evaporative media are positioned between the first tray and the second tray, and the wicking material is positioned to wick the condensate from both trays to the evaporative media.

67. The method of claim 66, wherein the method further comprises disposing the evaporative media entirely above the highest water level in the first tray and the second tray.

68. The method of claim 39, 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 of the evaporative media.

69. The method of claim 46, wherein the method further comprises configuring the wicking material to wick the condensate at an angle which is within a range from the vertical direction and the horizontal direction.

70. The method of claim 38, wherein evaporating the condensate in the vicinity of the condenser coil facilitates cooling the condenser coil.