Evaporative cooler using hollow fibers with protective layer

Abstract

A unit for use in evaporative cooling includes a first frame with a cover and an open second frame opposite the first frame. A post is located between and coupled to the first frame and the second frame. A porous hollow fiber membrane extends around the post between the first frame and the second frame and is coupled to the first frame and the second frame to form an internal volume. The first frame and the second frame are configured for water to flow between the first frame and the second frame via the membrane. The membrane is configured to deliver water between the first frame and the second frame and to allow airflow from the interior volume through the membrane for evaporative cooling. The unit has one or more protective layers to minimize or prevent leakage of water from the hollow fiber membrane.

Description

Background Technology

[0001] Evaporation is a low-cost and energy-efficient cooling method used to regulate temperatures in data centers, food processing plants, or office buildings. Currently, cellulose pads are used for large-scale evaporative cooling in applications such as data centers. Hot, dry air is cooled by evaporating water flowing through the cellulose pad, resulting in cool, humid air at the output. This type of cooling requires large quantities of water, and the medium must be kept either dry or humid to prevent degradation due to scaling or crystallization. The humidity level of the air discharged into the data center can be controlled using louvers or dampers that guide the incoming air through only a portion of the medium or completely around the medium in a bypass duct. Therefore, there is a need for improved evaporative cooling systems. Summary of the Invention

[0002] A unit for use in evaporative cooling includes a covered first frame and an open second frame opposite to the first frame. A plurality of mechanical supports are located between and connected to the first and second frames. A porous hollow fiber membrane extends around the supports between the first and second frames and is connected to the first and second frames to form an internal volume. The first and second frames are configured for liquid to flow between them via the membrane. The membrane is configured to transport liquid between the first and second frames and to allow gas flow through the membrane for evaporative cooling.

[0003] The unit has one or more protective layers to minimize or prevent water leakage from the hollow fiber membrane in the unit. Attached Figure Description

[0004] Figure 1A This is a front sectional view of a rounded square evaporative cooling unit.

[0005] Figure 1B This is a side sectional view of a rounded square evaporative cooling unit.

[0006] Figure 2 This is a diagram of the water recirculation system used in the evaporative cooling unit.

[0007] Figure 3A This is a front view of an evaporative cooling unit with branched water flow.

[0008] Figure 3B This is a side view of an evaporative cooling unit with branched water flow.

[0009] Figure 3C This is a rear view of an evaporative cooling unit with branched water flow.

[0010] Figure 4AIt is a cross-sectional view of the outer covering of the fiber's protective layer.

[0011] Figure 4B It is a cross-sectional view of the outer and inner protective layers of the fiber.

[0012] Figure 4C It is a cross-sectional view of the outer protective layer or wrapping.

[0013] Figure 4D This is a cross-sectional view of the outer protective layer of the fiber.

[0014] Figure 4E This is a cross-sectional view of the outer and inner protective layers of the fiber. Detailed Implementation

[0015] Implementation schemes include evaporative coolers using membranes with hollow fibers having porous walls, which provide enhanced evaporative cooling and reduced pressure drop. This construction includes an array of braided fibers wound into annular cylinders, rounded squares, or other shapes and sealed at both ends to allow liquid water to flow through the fibers. One end of the annular cylinder is open to allow air to pass through, and the other end is capped, forcing air to flow through the fiber array to cool the incoming air. This construction offers ease of manufacture compared to folded designs. This construction also improves panel performance by systematically increasing the length of the panel. Additionally, adding folds in the fiber array surrounding the cylinder also improves performance due to the increased surface area. This construction with hollow fibers without porous walls can also be used as a heat exchanger. When the air is very humid, porous-walled fibers can also be used as a heat exchanger.

[0016] An example of an evaporative cooling unit is disclosed in PCT application publication No. WO 2023 / 037287, which is incorporated herein by reference in its entirety.

[0017] Evaporative cooling unit

[0018] Figure 1A and Figure 1B These are front and side sectional views of the panel structure of the evaporative cooling unit 10. As an example, the structure includes an array of woven fibers in a rounded square shape. Figure 2 The image shows a perspective view of unit 10. (Example) Figure 1A and Figure 1BAs shown, this panel configuration is also applicable to any other cross-sectional shape. Unit 10 includes a front open frame 12, mechanical supports such as pillars 14, a porous hollow fiber membrane 16, and a covered rear frame 20. Frame 12 is open because it has openings to allow air to pass through or flow into unit 10. Frame 20 is covered within this frame, at least partially and preferably completely blocking the passage or flow of air within unit 10. As an alternative, unit 10 may include another membrane that wraps around and is spaced apart from another set of mechanical supports inside membrane 16. Unit 10 may be a portable or non-portable unit.

[0019] A liquid, such as water, flows (22) between the front frame 12 and the rear frame 20. An airflow or airflow (24) from the front frame 12 is forced by the rear frame 20 through the fibers of the membrane 16 to cool the air. Alternatively, air may flow in another direction from the outside of the unit 10 to the internal volume. The unit 10 preferably does not have a core, such that the internal volume is open between the frames to allow airflow through the internal volume more efficiently. Air may be induced into a radial flow through the fibers of the membrane 16. The frame 12 may be mounted horizontally in an air duct and has mechanical structures for attachment to the air duct, wherein a fan draws air from the outside through the membrane 16.

[0020] Column 14 extends directly or via other mechanical structures between and connects to frames 12 and 20. Column 14 may have optional perforations, such as perforations 15. For illustrative purposes, only a single perforation 15 is shown; a column may have multiple perforations while still maintaining mechanical stability. The perforations allow airflow through the column. Columns 14 may be connected to each other to provide additional support. For example, column 14 may include an optional crossbeam 18 located between frames 12 and 20 (such as at the midpoint between the frames or elsewhere). The crossbeam 18, or other mechanical connections between columns 14, may deflect airflow through the internal volume of unit 10. One of the supported columns may optionally be used as a conduit to facilitate unit maintenance and installation.

[0021] Column 14 may have a circular cross-sectional shape as shown, or other shapes such as the following alternatives and options. The column may be a rounded rectangular strip, such as 0.75 inch × 0.25 inch, where each corner is rounded with a radius of 0.125 inches and set at a 45° angle to the circumference of a square. The column may be a folded column, where a 1.5 inch × 0.125 inch sheet of material is folded so that the cross-section becomes 0.75 inch × 0.25 inch. The column may be a corner column, which is a 0.5 inch × 0.5 inch × 0.125 inch angle iron “L” shaped piece. For example, one or more columns may be hollow tubes to facilitate all water connections at one end (frame).

[0022] Column 14 is preferably made of ABS plastic. Alternatively, the column may be formed of stainless steel, aluminum, or fiberglass. Frames 12 and 20 are preferably made of ABS plastic. Alternatively, the frames may be formed of PVC, styrene, polycarbonate, or metal. The material of unit 10 may optionally have a flame retardant (FR) rating.

[0023] A membrane 16 (e.g., a woven fiber mat) extends (e.g., wraps) around four posts 14 to form an internal volume, and can be positioned between the posts 14 and the frame (e.g. Figure 1A (As illustrated) or mechanically held in place between the inner frame assembly and the outer frame assembly. The membrane 16 preferably forms a continuous ring around the pillar 14, as shown. Figure 1A As shown, this creates an internal volume; alternatively, membrane 16 may form a discontinuous ring around a column. Hollow fibers in membrane 16 are encapsulated at both ends of a frame. For example, the fibers of membrane 16 may be held in epoxy resin within the frame, with the open ends of the hollow fibers receiving water or other liquids. As another example, the ends of the fibers in membrane 16 may be held by an adhesive, which can then be cut to open the fiber ends, and end plates can be fixed to the open ends of the fibers. Alternatively, unit 10 may have a frame configuration in which the frame supports the open ends of the hollow fibers, which are then attached to an air handling unit in the system having water channels for circulating water through the hollow fiber membrane.

[0024] The membrane 16 may comprise multiple layers, such as 27 to 33 layers surrounding the pillar 14. Alternatively, the length of the membrane 16 may be increased (L). f The membrane is designed to reduce the number of layers. It is hydrophobic (at least internally). Air flows from the front of the panel through the fibers and evaporates at the fibers to cool the air. The airflow through the fibers is reduced due to the increased surface area. Exemplary parameters for hollow fiber membranes include: pore size of 0.01 to 0.2 micrometers, preferably 0.03 to 0.04 micrometers; porosity of 25% to 80%; wall thickness (single layer) of 15 to 75 micrometers, preferably 25 to 50 micrometers; and weaving density of 15 to 65 fibers per inch, or 20 to 60 fibers per inch, or 35 to 53 fibers per inch. Examples of hollow fiber membranes are disclosed in U.S. Patent No. 9,541,302. Examples of hollow fiber membranes also include the following products: LIQUI-CEL MM series membrane contactors (product ID: B5005009013) from 3M Company and LIQUI-CEL SP series membrane contactor boxes (product ID: B5005009016) from 3M Company.

[0025] Figure 2This is a diagram of a water recirculation system for an evaporative cooling unit 10. A water tank 30 supplies water to a pump 34 via an inlet line 32, which circulates the water through a water filter 36 to an inlet 38 in a frame 12. An outlet 40 on the frame 20 supplies water to a water return line 42 returning to the water tank 30. Alternatively, water may flow in the opposite direction if the frame 20 receives water. Optionally, a frame may include both an inlet and an outlet. The water may have a specific type of quality. The water recirculation system may optionally include an anode / cathode feature to control mineral buildup within the water loop.

[0026] bifurcated water flow

[0027] Figure 3A , Figure 3B and Figure 3C These are front, side, and rear views of an evaporative cooling unit 90 with branched water flow. Unit 90 includes a front frame 92 having a channel 94; and a flow separation element 96 that divides the channel 94 into two channels and prevents water from flowing between the two channels. The rear frame 102 of unit 90 includes a continuous channel 104. Channels 94 and 104 can be formed by machining the frame to create grooves, and the flow separation element 96 can be formed by leaving the corners unmachined so that those portions of the frame block water flow. A porous hollow fiber membrane 106 with hollow fibers is located between the front frame 92 and the rear frame 102. In use, the front frame 92 includes an inlet 98 for water to flow (108) through the hollow fibers in the membrane 106 into the rear frame 102. Water is forced under pressure through the channel 104 in the rear frame 102 to flow out (110) to the outlet 100 in the front frame 92.

[0028] In this embodiment, the inlet and outlet are therefore located on the same side of unit 90 within frame 92. This feature causes the water channel to branch, directing water downwards to two adjacent surfaces of the unit and returning through the other two adjacent surfaces. In unit 90, water flows to the right on the top two surfaces and returns to the left on the bottom two surfaces. Alternatively, unit 90 may include inlets and outlets on both frame 92 and frame 102 to branch the water flow at both ends. This feature offers advantages to the end user, including ease of assembly and lower air pressure drop during operation. Moreover, in this embodiment, it is not necessary to use a pipe as a column within a column to transport water between the ends (frames) of the unit.

[0029] In addition to the bifurcation flow characteristics, unit 90 may have the same characteristics as... Figure 1A and Figure 1BThe unit 102 shown has a similar configuration, features, and materials. Specifically, frame 92 can be an open frame, and frame 102 can be a covered frame. Alternatively, frame 102 may include an inlet, an outlet, and a flow separation element, wherein frame 92 has a continuous channel. Frame 92 can be attached to frame 102 by a mechanical support (such as a column), with membrane 106 wound around the column. Membrane 106 can be held in the frame by an adhesive, and the open ends of the fibers in membrane 106 are in fluid communication with the channels in the frame. Membrane 106 may have the properties described above for unit 10. In use, inlet 98 can be connected to inlet line 32 (see...). Figure 2 ), and outlet 100 can be connected to return line 42.

[0030] The bifurcated water flow characteristic can also be incorporated into evaporative cooling units with other shapes.

[0031] Modeling has shown that this bifurcated water flow design does not adversely affect cooling efficiency or air pressure drop during operation. The only notable change in the modeling is that, at the same flow rate of gallons per minute, the water pressure through the fibers should be as high as [missing value]. Figure 1A and Figure 1B The design shown is more than four times larger. This change is due to water passing through half of the fiber openings twice.

[0032] Protective layer for hollow fibers in coolers

[0033] As described above, Figures 3A to 3C The diagram shows the water flow through the evaporative cooling unit. A desirable requirement is that no liquid water can form droplets or leak from the fibers during operation. Ideally, only water vapor should be released from the fibers and enter the air, but leaks and small water droplets, sometimes referred to as "seepage," can sometimes occur.

[0034] These leaks have been shown to be caused by several factors. One cause is physical damage to the fibers, which could be due to improper handling or accidental impact with tools or other sharp objects. Another cause has been identified as fiber surface contamination. Certain contaminants on the fiber surface can cause seepage, where water can penetrate through the pores of the fiber and accumulate on the outer surface due to impaired hydrophobicity of the polymer. These contaminants can include siloxanes, oils, and other chemicals.

[0035] Several solutions have been designed to eliminate both physical damage to fibers and surface contamination. See below for details. Figures 4A to 4E The solutions described involve a protective layer of hollow fiber or another material to physically block the water-filled fibers from damage or contamination. These protective layers do not participate in the module's evaporative cooling effect and should generally be configured to minimize cost and air pressure drop.

[0036] exist Figures 4A to 4E In the illustrated embodiment, the sectional view is a plan view passing through the unit between frame 12 and frame 20, as shown. Figure 2 The line AA shown represents this.

[0037] Figure 4A This is a cross-sectional view of the outer covering 120 of the protective layer of fibers surrounding the functional layer 122. Figure 4B This is a cross-sectional view of the outer wrapping 124 and inner wrapping 126 of the protective layer surrounding the fibers of functional layer 128. Functional layers 122 and 128 are hollow fibers with water flow and provide evaporative cooling as described above. Protective layers 120, 124, and 126 are fibers without water flow. These fibers without water flow can be achieved, for example, with hollow fibers not connected to water flow or solid fibers without internal fluid paths, or by not opening or sealing specific fiber ends. This feature also creates a sacrificial layer of fibers on the module to protect the module from damage. When the fiber pad is wound onto the frame, the desired fiber edges or ends to be sealed can be selectively cut, curled, melted, crushed, sealed, or folded using a variety of devices. This allows for precise control over how many fibers become the sacrificial layer without water flow.

[0038] Figure 4C This is a cross-sectional view of the outer protective layer or covering 130 surrounding the functional layer 132. The functional layer 132 is a hollow fiber with water flow and provides evaporative cooling as described above. The protective material 132 can be implemented using, for example, a mesh, net, nonwoven fabric, or another material that allows airflow. Alternatively, the protective material can also be used in… Figure 4C The protective layer is located inside the module shown. Preferably, the material used for the protective layer is a flame retardant. The protective layer material may also include an antimicrobial coating to limit biological growth.

[0039] Figure 4D It is a cross-sectional view of the outer protective layer of fiber 134 surrounding functional layer 136. Figure 4E This is a cross-sectional view of the outer protective layer of fiber 138 and the inner protective layer of fiber 140 surrounding functional layer 142. Functional layers 136 and 142 are hollow fibers with water flow and provide evaporative cooling as described above. Protective layers 134, 138, and 140 are non-porous hollow fibers, which can be achieved, for example, with porous hollow fibers that are treated to block or seal the pores, preventing water from escaping through the pores and preventing leakage or seepage. This treatment may involve, for example, an additional coating on the outer layer of the fiber to seal the pores and prevent water from escaping. This treatment can be performed during the winding process or as a secondary coating step after the module is wound around the frame. Testing can be conducted to ensure that air pressure drop and cooling efficiency are not negatively affected by this additional coating.

[0040] Figures 4A to 4E The number of protective and functional layers shown is for illustrative purposes. In these or other embodiments, more or fewer protective or functional layers may be used, depending on, for example, the optimized or desired design.

[0041] although Figures 4A to 4E The embodiments shown each include an outer protective layer, but these embodiments may alternatively each include an inner protective layer with an optional outer protective layer. The inner protective layer and the optional outer protective layer may be related to... Figures 4A to 4E Any of the protective layers described. For example, these inner protective layers may be useful if the interior of the module is touched or handled during the module's installation process.

[0042] also, Figures 4A to 4E The embodiments shown can be combined in various ways to achieve other types of protective layers. For example, Figure 4A or Figure 4D The protective layer of the fiber can be used together with a protective outer layer in Figure 4C The interior of the module shown. As another example, Figure 4C The protective coating can be used together with the outer protective layer of the fiber in Figure 4A or Figure 4D The interior of the module shown. Additionally, as another type of protective layer, it can also be combined... Figure 4A and Figure 4D The protective layers of various types of fibers are shown.

Claims

1. A unit for use in evaporative cooling, the unit comprising: The first frame with a lid; An open second frame, which is opposite to the first frame; Multiple mechanical support members are located between the first frame and the second frame and are connected to the first frame and the second frame; A porous hollow fiber membrane extends around the mechanical support between the first frame and the second frame to form an internal volume and is connected to the first frame and the second frame; as well as A protective layer, comprising an outer covering of the fibers surrounding the hollow fiber membrane. The first frame and the second frame are configured for liquid to flow between the first frame and the second frame via the membrane, and the membrane is configured to transport the liquid between the first frame and the second frame and to allow airflow through the membrane for evaporative cooling.

2. The unit according to claim 1, wherein the protective layer further comprises an inner wrapping of the protective layer surrounding the fibers of the hollow fiber membrane.

3. The unit according to claim 1 or 2, wherein the outer or inner wrapping of the protective layer of the fiber comprises hollow or solid fibers without liquid flow.

4. A unit for use in evaporative cooling, the unit comprising: The first frame with a lid; An open second frame, which is opposite to the first frame; Multiple mechanical support members are located between the first frame and the second frame and are connected to the first frame and the second frame; A porous hollow fiber membrane extends around the mechanical support between the first frame and the second frame to form an internal volume and is connected to the first frame and the second frame; as well as A protective layer, comprising an outer protective layer or outer covering surrounding the hollow fiber membrane, The first frame and the second frame are configured for liquid to flow between the first frame and the second frame via the membrane, and the membrane is configured to transport the liquid between the first frame and the second frame and to allow airflow through the membrane for evaporative cooling.

5. The unit according to claim 4, wherein the protective layer further comprises an inner protective layer or inner wrapping surrounding the hollow fiber membrane.

6. The unit according to claim 4 or 5, wherein the outer protective layer or the outer wrapping or the inner protective layer or the inner wrapping comprises a mesh, a net, or a nonwoven fabric.

7. A unit for use in evaporative cooling, the unit comprising: The first frame with a lid; An open second frame, which is opposite to the first frame; Multiple mechanical support members are located between the first frame and the second frame and are connected to the first frame and the second frame; A porous hollow fiber membrane extends around the mechanical support between the first frame and the second frame to form an internal volume and is connected to the first frame and the second frame; as well as A protective layer, comprising an outer protective layer of fibers surrounding the hollow fiber membrane, The first frame and the second frame are configured for liquid to flow between the first frame and the second frame via the membrane, and the membrane is configured to transport the liquid between the first frame and the second frame and to allow airflow through the membrane for evaporative cooling.

8. The unit according to claim 7, wherein the protective layer further comprises an inner protective layer surrounding the fibers of the hollow fiber membrane.

9. The unit according to claim 7 or 8, wherein the outer protective layer or the inner protective layer of the fiber comprises porous hollow fibers, the porous hollow fibers being processed to block or seal the pores in the fiber.

10. The unit according to any one of claims 1 to 9, wherein the plurality of mechanical supports comprise columns, and one of the columns comprises a pipe for conveying the liquid.

11. The unit according to any one of claims 1 to 9, wherein the membrane forms a continuous ring around the post.

12. The unit according to any one of claims 1 to 9, wherein the ends of the fibers in the membrane are held by an adhesive, and at least some of the ends are open.

13. The unit according to any one of claims 1 to 9, wherein the second frame includes an inlet and the first frame includes an outlet.

14. The unit according to any one of claims 1 to 9, wherein the first frame or the second frame includes an inlet, an outlet, a first channel for the inlet, a second channel for the outlet, and a flow separation element located between the first channel and the second channel.

15. The unit of claim 14, wherein the first frame or the second frame comprises a continuous channel.

16. The unit according to any one of claims 1 to 9, wherein the membrane has a pore size of 0.01 micrometers to 0.2 micrometers.

17. The unit according to any one of claims 1 to 9, wherein the membrane has a porosity of 25% to 80%.

18. The unit according to any one of claims 1 to 9, wherein the membrane has a wall thickness of 15 micrometers to 75 micrometers.

19. The unit according to any one of claims 1 to 9, wherein the membrane has a weave density of 35 to 53 fibers per inch.

20. The unit according to any one of claims 1 to 9, wherein the membrane has a weave density of 15 to 65 fibers per inch.

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