WO2018051157A1

WO2018051157A1 - Water distribution systems for plate heat and mass exchanger for indirect evaportive cooling

Info

Publication number: WO2018051157A1
Application number: PCT/IB2016/001417
Authority: WO
Inventors: Demis Lukasz PANDELIDIS
Original assignee: Aurae Technologies Ltd
Current assignee: Aurae Technologies Ltd
Priority date: 2016-09-19
Filing date: 2016-09-19
Publication date: 2018-03-22
Anticipated expiration: 2019-03-19

Abstract

A water distribution systems for heat and mass exchangers(l) is designed to improve the cooling efficiency of indirect evaporative coolers and may be applied in the different units which use basic cycles or advanced cycles for indirect evaporative air cooling. The improvement to the evaporating water distribution is by water pipes(6) with holes(8) inside wet channel(A-A). This solution guarantees that all of the evaporative layers will get adequate wetting, and the evaporation will be not limited by the water buildup. By an unique water distribution structure in the wet channels(A-A), uniform water film is created on the surfaces of evaporative media. This enlarges the wetting area of wet channels(A-A) with minimum water flow and allows the performance of the heat and mass transfer to be increased. The proposed water distribution system consumes very little energy for its operation, only a small pump, due to the lack of water nozzles which require high water pressure for operation. The energy efficiency of the system will therefore be extremely high.

Description

WATER DISTRIBUTION SYSTEMS FOR PLATE HEAT AND MASS EXCHANGER FOR INDIRECT EVAPORATIVE COOLING

FIELD OF THE INVENTION

[0001] The present invention relates to plate heat and mass exchangers for indirect evaporative cooling. In particular, the present invention relates to water distribution systems for evaporative coolers for controlling distribution of water uniformly across a media to avoid dry spots and distribution of excess water.

BACKGROUND

[0002] The application of air conditioning systems in the buildings is significantly increasing. Recently evaporative cooling devices, which operate on the basis of water evaporation, has gained growing interest for use in air-conditioning systems instead of the conventional units. Evaporative air coolers own such popularity to the fact that they are able to significantly reduce the energy used for air conditioning systems. Therefore, they are less dependent on the fossil fuel energy and they are environment friendly.

[0003] In addition, it is becoming increasingly important to reduce global consumption of the water. In that respect, the evaporative air cooling systems have to be improved in their design for their efficiencies in terms of water consumption.

[0004] The main driving force for the evaporative cooling process is the outdoor air and water: air reduces its temperature by humidifying itself. As a result, warm and dry air becomes cool and moist. An indirect evaporative air coolers are able to provide cooling of the product air stream without increasing its moisture content: in these devices the primary (main) air stream passes over the dry side of the plate inside a heat exchanger, while secondary (working) air flows over the opposite side of the plate, which is covered with thin water film. The sensible heat flux from the dry side is transferred to the wet side, which results in cooling of the primary air flow without adding moisture, because the latent heat of water evaporation is transferred to the working air stream. Evaporation of the water causes reduction of the plate surface temperature, which results in the heat transfer between the primary air and the plate.

[0005] To obtain maximum evaporation, the media must be adequately wetted. Most conventional evaporative coolers have a water spraying system on a top of heat and mass exchanger. The typical cooler is mainly equipped with an evaporative pad, a fan, water distribution system, a water pump and a reservoir. It operates as follows: The pump lifts water from the reservoir to the distribution system and the water flows down through the pads and then is collected in the reservoir. The water is sprayed by the water nozzles to the wet channels and runs down onto the top of the evaporative media. The second possibility is the use of porous materials for the construction of the heat exchanger, so the nozzles may be avoided.

[0006] One prior technology discloses a water distributor, that is located at the upper end of each of the secondary channels. The water distributors are arranged to spray water horizontally across the upper ends of the secondary channels from where it can drip down to wet the secondary surfaces. The supply of water to the water distributors is preferably intermittent and may be at a controlled pressure to vary the length of spray. The water distribution sprayers are too inefficient to distribute the water uniformly and entirely over the wet surface. The disadvantage of this system is that they require a lot of water flow and high pressure.

[0007] Another prior technology discloses a feeder wick system creates the wetting of the wet channels without excess water. It rely on the following principles: using capillary porous plates as a structural material for the heat transfer matrix, allowing moisture to fully cover the surface of the working channels at the minimum value of water consumption. The wet channel is made of specially-designed sheets with the high water retention and wick ability, created with porous material, which allows for an even water distribution. Each porous plate is coated with an impervious material on one side, in order to create the dry channel. Each channel also uses fins in order to improve the heat transfer and to keep the exchanger' s structure. Water is delivered to the exchanger directly from the pipeline. The main limitation of the system are the capillary forces, therefore this water distribution system works only in small indirect evaporative exchangers or in the modular units.

SUMMARY

[0008] Embodiments of the invention improve the efficiency and economic feasibility of evaporative coolers. Aspects of the invention improve over prior technologies in their applications to the water distribution system, and the use of the water pipes with holes inside the wet channel to improve distribution of water for evaporation and also to support the evaporative process. [0009] In one aspect, the new improved water distribution system described herein enables the use of evaporative cooling in efficient and economical way in both small and large indirect evaporative coolers.

[0010] Further aspects of the invention improve on certain elements of plate heat and mass exchangers used in evaporative cooling systems. Indirect evaporative cooling systems increase its efficiency and productivity by the addition of the novel method disclosed here. The elements of these improvements refer to the water distribution system, the use of water pipes with holes located inside the wet channel for uniformly wetting these channels and other elements disclosed in here. By an unique water distribution structure in the wet channels, uniform water film is created on the surfaces of evaporative media. This allows to achieve better heat and mass transfer in indirect evaporative cooler.

[0011] Although the invention has been herein shown and described in what is conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope of the invention, which is not to be limited to the illustrative details disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1 is a diagram showing a perspective and schematic view of a water distribution system used in parallel-flow or counter-flow heat and mass exchanger (water pipes with holes inside wet channel are not shown) according to one embodiment of the invention.

[0013] FIG. 2 is a diagram illustrating a side view of embodiment of FIG. 1 according to one embodiment of the invention.

[0014] FIG. 3 is a diagram showing a cross-section of a wet side of the plate of an embodiment of FIG. 1 with water pipes with holes inside wet channel are shown, as well as the connection with the water distribution collectors according to one embodiment of the invention.

[0015] FIG. 4 is a diagram illustrating a cross section of a dry side of the plate of an embodiment of FIG. 1 with channel guides are shown according to one embodiment of the invention.

[0016] FIG. 5 is a diagram showing a top view of an embodiment of FIG. 1 with the main water pipe, the water distribution collectors and the outline of the water tank shown according to one embodiment of the invention. [0017] FIG. 6 is a diagram showing a perspective and schematic drawing illustrating a water distribution system used in cross-flow heat and mass exchanger (water pipes with holes inside wet channel are not shown) according to one embodiment of the invention.

[0018] FIG. 7 is a side view diagram of an embodiment of FIG. 6 according to one embodiment of the invention.

[0019] FIG. 8 is a cross section view of a wet side of the plate of an embodiment of

FIG. 6, water pipes with holes inside wet channel are shown, as well as the connection with the water distribution collectors according to one embodiment of the invention.

[0020] FIG. 9 is a diagram showing a cross section view of a dry side of the plate of an embodiment of FIG. 6 with channel guides are shown according to one embodiment of the invention.

[0021] FIG. 10 is a diagram showing a top view of an embodiment of FIG. 6 with the main water pipe, the water distribution collectors and the outline of the water tank shown according to one embodiment of the invention.

[0022] FIG. 11 is a diagram showing a detail "A" - holes on the pipe in wet channel, a cross section of embodiment of FIG. 1 and FIG. 6 according to one embodiment of the invention.

[0023] FIG. 12 shows diagrams illustrating a cross section (C-C) of a pipe in wet channel, embodiment of FIG. 1 and FIG. 6 according to one embodiment of the invention.

[0024] FIG. 13 shows diagrams illustrating a cross section (D-D) of a water distribution holes in wet channel, of embodiment of FIG. 1 and FIG. 6, according to one embodiment of the invention.

[0025] FIG. 14 is a diagram illustrating a cross section (E-E) of an embodiment of

FIG. 1 and FIG. 6: dry and wet channels according to one embodiment of the invention.

[0026] Persons of ordinary skill in the art may appreciate that elements in the figures are illustrated for simplicity and clarity so not all connections and options have been shown to avoid obscuring the inventive aspects. For example, common but well- understood elements that are useful or necessary in a commercially feasible embodiment may often not be depicted in order to facilitate a less obstructed view of these various embodiments of the present disclosure. It will be further appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. It will also be understood that the terms and expressions used herein may be defined with respect to their corresponding respective areas of inquiry and study except where specific meanings have otherwise been set forth herein.

DETAILED DESCRIPTION

[0027] The present invention may now be described more fully with reference to the accompanying drawings, which form a part hereof, and which show, by way of illustration, specific exemplary embodiments by which the invention may be practiced. These illustrations and exemplary embodiments may be presented with the understanding that the present disclosure is an exemplification of the principles of one or more inventions and may not be intended to limit any one of the inventions to the embodiments illustrated. The invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Among other things, the present invention may be embodied as methods, systems, computer readable media, apparatuses, or devices. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. The following detailed description may , therefore, not to be taken in a limiting sense.

[0028] In one embodiment, a cooling unit includes a dry channel and a wet channel arranged to closely come into contact with each other. For example, referring now to FIG. 1 , which shows a diagram showing a perspective and schematic view of a water distribution system used in parallel-flow or counter-flow heat and mass exchanger (water pipes with holes inside wet channel are not shown) according to one embodiment of the invention. FIG. 2 is a diagram illustrating a side view of embodiment of FIG. 1 according to one embodiment of the invention. For illustration purposes and not as a limitation, the following reference numbers are used for FIGS. 1-14:

[0029] 1 - Heat and mass exchanger

[0030] 2 - Water pump

[0031] 3 - Water tank [0032] 4 - Main water pipe

[0033] 5 - Water distribution collectors

[0034] 6 - Water pipe inside wet channel

[0035] 7 - Channel guide in dry channel

[0036] 8 - Hole on the water pipe in wet channel (6)

[0037] 9 - Wet channel plate

[0038] 10 - Coating impervious material for dry channel

[0039] A-A - Wet channel

[0040] B-B - Dry channel

[0041] For example, referring to FIGS. 1 and 2, the heat and mass exchanger 1 includes a water pump 2, a water tank 3, a main water supply/pipe 4, a water distribution collectors 5.

[0042] Turning to FIG. 3, a diagram shows a cross-section of a wet side of the plate of an embodiment of FIG. 1 with water pipes with holes inside wet channel are shown, as well as the connection with the water distribution collectors according to one embodiment of the invention.

[0043] The heat and mass exchanger 1 may further include a wet channel A with wet channel plates 9. FIG. 3 further shows water pipe inside wet channel A, as indicated by 6.

[0044] Referring now to FIG. 4, a diagram illustrates a cross section of a dry side of the plate of an embodiment of FIG. 1 with channel guides are shown according to one embodiment of the invention. In one embodiment, the heat and mass exchanger 1 includes a dry channel B. In one illustration, the dry channel B may include channel guide 7 therein as directed by 7.

[0045] In a further embodiment, FIG. 5 is a diagram showing a top view of an embodiment of FIG. 1 with the main water pipe, the water distribution collectors and the outline of the water tank shown according to one embodiment of the invention.

[0046] In an alternative embodiment, FIGS. 6 and 7 show diagrams illustrating a water distribution system used in cross-flow heat and mass exchanger (water pipes with holes inside wet channel are not shown) according to one embodiment of the invention. In conjunction with FIG. 3 , FIG. 8 is a cross section view of a wet side of the plate of an embodiment of FIG. 6, water pipes with holes inside wet channel are shown, as well as the connection with the water distribution collectors according to one embodiment of the invention. [0047] The heat and mass exchanger, in one embodiment, may include a plate having a dry side and a wet side. The wet side may include a wet channel having wicking materials to help water evaporation. A wicking material with high wicking ability enables a uniform wetting on the wet surface of the plate. Additional advantage of embodiments of the invention includes that there is no exchanger size limit for its application: unlike existing water distribution methods, embodiments of the invention may be used in both small and very large exchangers. For example, this may be caused by the fact that water is delivered uniformly along the whole length of the channel. In existing methods, water is delivered only on one side of the exchanger, therefore existing evaporative coolers need to have relatively small dimensions.

[0048] In another embodiment, a water supply system may feed water to the wet channel. For example, see also FIG. 10, a water distribution system includes:

[0049] a water pump that moves water, water is lifted by a pump from a bottom reservoir and it flows over the wet surfaces while the airflow passes through the wet channels where the water is circulating,

[0050] a water tank which stores circulating water; various materials may be used for water tank construction: plastics, metals, fiberglass; by design a water tank should do no harm to the circulating water,

[0051] a main water pipe which delivers circulating water to the water distribution collectors, a water pump is connected to this pipe.

[0052] water distribution collectors which deliver circulating water to the water pipes with holes, which are located inside wet channel,

[0053] water pipes with holes located inside wet channel which create uniform water film on the surfaces of evaporative media,

[0054] water pipes may be made from various materials: plastics, metals, fiberglass.

[0055] As illustrated in FIGS. 11-13, the water pipes inside wet channel may be designed in a different shape: round, elliptic or rectangular. For example, FIG. 12 shows four configurations or cross-sections: C-Cl - Round pipe; C-C2 - Elliptic pipe; C-C3 - Rectangular pipe; and C-C4 - Rectangular pipe obtained with impervious material and wet channel plate.

[0056] For example, the holes, bores, or openings of the pipes may further include different cross-sectional shapes. For example, FIG. 13 shows four configurations or cross-sections: D-Dl - Round pipe; D-D2 - Elliptic pipe; D-D3 - Rectangular pipe; D-D4 - Rectangular pipe obtained with impervious material and wet channel plate. [0057] The water distributor may be supplied using water supply by a pump from a water tank. A water pump may be merged in the main water pipe. The water may run periodically in response to an amount of evaporated water. The pump, in one example, may pump to lift water when the water film on the wet plate starts to fade. At the lower end of the wet channels, excess water may be collected and returned to the water tank.

[0058] In an embodiment of this invention, the wet channel may be arranged to allow the air to flow with water to the downer end of the wet channel, thus allowing the water to flow downward due to gravity while uniformly wetting the surface of the wet channel. Aspects of the invention provide uniformly distributing air and water in the wet channels of indirect evaporative cooler using the inside water pipes as the guides to pass through the wet channels of exchanger. In one embodiment, the system allows to deliver minimal amount of water to the channels, only the exact amount that is needed for evaporation process. Due to this fact, it allows to minimize the water consumption by indirect evaporative coolers.

[0059] As water in the wet channels is evaporated, the dissolved minerals that were in the water will accumulate on the heat and mass transfer surfaces and the water pipes. The water distribution system according to one embodiment of the invention may operate in flushing function that allows the minerals from the heat and mass exchanging plate to be removed. In this embodiment, the air may not delivered to the wet channel, while water distribution system continues to operate - the falling water removes the minerals formed in the wet channel.

[0060] The even distribution of water inside the channels, in one embodiment, may require a hydrophilic coating for the plates inside the wet channels. This may allow to create even water film on its surface. Even water distribution may also be obtained by a hydrophobic plate material when additional fluid is added to the water to lower surface tension of water (any kind of soap or detergent).

[0061] In another embodiment, aspects of the invention may be supplied from a water supply network, in which case the pump may spared or eliminated. For such solution, the pressure reducing valve automatically reduces a high pressure from water supply network to a steady pressure before the main water pipe and it controls the required water flow for a uniform wetting on the wet surface of the plate.

[0062] In a further embodiment, water may also be supplied from a gravity water tank, so the pump is not required. The water may be stored at atmospheric pressure and distributed by gravity flow. In this embodiment, the tank is elevated above the heat and mass exchanger and it may be supplied by the rainwater harvesting or by the sea water.

[0063] In another embodiment, FIG. 9 shows a cross section view of a of a dry side of the plate of an embodiment of FIG. 6 with channel guides are shown according to one embodiment of the invention. As discussed above, the heat and mass exchanger 1 may include a dry side of the plate. Moreover, according to FIG. 14, a diagram shows one embodiment of arrangements of a dry channel and a wet channel according to aspects of the invention. For example, FIG. 14 shows a cross section (E-E) of an embodiment of FIG. 1 and FIG. 6: dry and wet channels according to one embodiment of the invention.

[0064] A water distribution systems for plate heat and mass exchanger for indirect evaporative cooling. A distribution system includes water pump, water tank, main water pipe, water distribution collectors and water pipes with holes inside wet channel.

[0065] The method of improvement to the evaporating water distribution is by water pipes with holes located inside the wet channel. This solution may guarantee that all of the evaporative layers will get adequate wetting, and the evaporation will not be limited by the water buildup.

[0066] The water pipes inside wet channel as claimed in claim 2, may be designed in different shapes: round, elliptic, rectangular or other.

[0067] The pump as claimed in claim 1, runs periodically in response to an amount of evaporated water. It begins to lift water when the water film on the wet plate starts to fade.

[0068] The proposed method as claimed in claim 1, allows that at the lower end of the wet channels, excess water is collected and returned to the water tank.

[0069] This water distribution system may be used in both small and very large indirect evaporative coolers. It is caused by the fact that water is delivered uniformly along the whole length of the wet channels.

[0070] The invention provides novel means for uniformly distributing air and water in the wet channels of indirect evaporative cooler using the inside water pipes as the guides to pass through the wet channels of exchanger.

[0071] The proposed water distribution system may operate in flushing function that allows to remove the minerals from the heat and mass exchanging plate. [0072] The even distribution of water inside the channels requires distribution system as in claim 2 and a hydrophilic coating for the plates inside the wet channels which allows to create even water film on its surface. Even water distribution may also be obtained by a distribution system as in claim 2 and a hydrophobic plate material when additional fluid is added to the water to lower surface tension of water (any kind of soap or detergent).

[0073] This invention may be applied in the different units which use basic cycles or advanced cycles for indirect evaporative air cooling, it fits to all types of heat and mass exchangers which have various airflow schemes.

[0074] The proposed water distribution system may be supplied from a gravity water tank, so the pump is not required.

[0075] The proposed water distribution system may be supplied from a water supply network, so the pump is not required.

Claims

What is claimed is:

1. A heat exchanger comprising:

a dry channel;

a wet channel having one or more plates, said one or more plates comprising wicking materials for water evaporation; and

wherein the one or more plates including water pipes with holes for creating a uniform water film.

2. The heat exchanger of claim 1, wherein the water pipes include one or more of the following cross-section shapes: circular, elliptic, and rectangular.

3. A water distribution system comprising:

a water supply for providing water to a wet channel;

a water tank for storing water;

a water connection for delivering water to the water supply;

water distribution collectors located inside the wet channel for delivering water thereto; and

water pipes with holes located inside wet channel for receiving the water from the water distribution collectors and for creating a uniform water film on surfaces of an evaporative media of the wet channel.