Cooling device for a heat source cooled by an airflow and assembly comprising such a cooling device

Abstract

A cooling device (1) positionable in the cooling airflow (21) of a heat source (20) and in contact with said heat source (20), and comprising a fiber array (2), the cooling device (1) includes a self-supporting frame (3) with a base (5) on which the frame (3) rests in an upright configuration corresponding to the operating configuration of the device (1). The fiber array (2) is coupled to the frame (3) to form a perforated barrier suitable for the passage of the cooling airflow (21) and includes a first series of feed fibers (6) suitable for being supplied with water by a water supply system (22) and a second series of capillary fibers (7). Capillary fibers (7) at least partially surround the feed fibers (6) to form a contact zone (8).These capillary fibers (7) develop from the contact zone (8) between the capillary fiber (7) and the feeder fiber (6) towards the upper part (4) of the frame (3). Part of the contact zones (8) between the capillary fiber (7) and the feeder fiber (6) extend below the base (5) of the frame (3) in the configuration of use of the cooling device (1). Figure for the abstract: Fig. 1.

Description

Title of the invention: Cooling device for a heat source cooled by an airflow and assembly comprising such a cooling device

[0001] The present invention relates to a cooling device for a heat source cooled by an airflow and an assembly comprising such a cooling device.

[0002] It relates in particular to a cooling device for a heat source cooled by an airflow, the cooling device being positionable in the airflow cooling the heat source and in contact with the heat source, said cooling device comprising a network of fibers capable of being supplied by a water supply system.

[0003] Air cooling of a heat source, such as the hot part of a heat exchanger or an electronic component, is known. However, high summer temperatures and heat waves create an environment unfavorable to air cooling. Covering the hot source with a water-impregnated fabric is known to improve such cooling. This lowers the surface temperature of the heat source. However, this solution is very water-intensive and its cooling effects are limited.

[0004] An object of the invention is to provide a cooling device of the aforementioned type whose design improves heat transfer between the heat source and the cooling airflow.

[0005] To this end, the invention relates to a cooling device for a heat source cooled by an airflow, the cooling device being positionable in the airflow for cooling the heat source and in contact with the heat source intended to extend at least partially below the cooling device, said cooling device comprising a network of fibers capable of being supplied with water by a water supply system, characterized in that the cooling device comprises a self-supporting frame comprising an upper part and an opposing lower part called a base by which the frame rests in an upright configuration corresponding to the operating configuration of the cooling device,in that the fiber network is coupled to the reinforcement to form a perforated barrier suitable for the passage of the cooling airflow from the heat source and in that the fiber network comprises a first series of so-called feeder fibers suitable for being supplied with water by the water supply system and a second series of so-called , capillaries, at least a portion of the capillary fibers surrounding at least partially the feeder fibers to form at least one contact zone, these capillary fibers developing from the capillary fiber / feeder fiber contact zone towards the upper part of the frame so as to be able to extend over at least part of their length substantially vertically in the cooling device usage configuration, at least a portion of the capillary fiber / feeder fiber contact zones extending below at least part of the base of the frame in the cooling device usage configuration to form the part of the cooling device capable of coming into contact with the heat source.Thus, at least a portion of the capillary fibers extend substantially vertically over at least part of their length arranged between the base and the upper part of the frame in the frame's usage configuration and present at a low point at least one area in contact with the feeder fibers for capillary diffusion of the water contained in the feeder fibers into the capillary fibers. It should be noted that the expression "substantially vertical" means that the capillary fibers form an angle of less than 45° with the vertical along at least part of their length when the cooling device is in use. The design of the cooling device maximizes cooling by increasing the contact area between the air and the water through capillary action. The cooling principle is twofold. The heat source is cooled by evaporation of water in the area of ​​contact with the wet fibers, and the air is cooled by evaporation of free water from the fibers. The fibers thus diffuse liquid water through their interior, while their outer surface, in contact with the air, allows this water to evaporate. The air is cooled by the evaporation of the water.The arrangement of the capillary fibers, which grow upwards from the capillary fiber / feeder fiber / heat source contact zone towards the top of the frame, and are designed to extend at least part of their length in a substantially vertical manner when the cooling device is in use, increases the air / water contact surface and improves heat transfer. The design of the cooling device, with its self-supporting structure that makes it easily removable, also allows for easy maintenance.

[0006] According to one embodiment of the invention, at least one of the hair fiber / feed fiber contact zones is formed by a knot of the hair fiber around at least one of the feed fibers. This results in a simple design without compromising the efficiency of water impregnation of the hair fibers from the feed fibers.

[0007] According to one embodiment of the invention, the hair fibers are plant fibers containing between 65 and 85%, expressed as a percentage by weight, of cellulose relative to the total weight of the hair fibers. A high cellulose content ensures the wetting properties and determines the permeability of said fibers to water.

[0008] According to one embodiment of the invention, the hair fibers are chosen from the group formed by cotton, flax, hemp, jute, sisal fibers.

[0009] According to one embodiment of the invention, the hair fibers exhibit, at an ambient temperature of 25°C and under conditions of relative humidity of the ambient air greater than 80%, a water retention rate, corresponding to the quantity of water that said fibers can absorb per unit weight, greater than 10%.

[0010] According to one embodiment of the invention, at least a portion of the capillary fibers are configured to, in the cooling device operating configuration and in the water-supplied state of the feeder fibers, exhibit a capillary rise height from the capillary fiber / feeder fiber contact areas of at least 6 cm.

[0011] According to one embodiment of the invention, the feed fibers are fibers selected from the group formed by flax, hemp, jute, sisal, wool fibers, these fibers being alone or mixed with artificial fibers representing at most 40% expressed by weight of said mixture.

[0012] According to one embodiment of the invention, at least one of the feed fibers has a wettability expressed as an angular value corresponding to the contact angle formed between the surface of said feed fiber and the wall of a water droplet deposited on said surface, this contact angle being less than 60°.

[0013] According to one embodiment of the invention, the feed fibers have a diameter between 1.5 and 3.7 mm and the hair fibers have a diameter between 1.5 and 4 mm.

[0014] According to one embodiment of the invention, the feed fibers have a porosity of between 50 and 90%, preferably close to 60%.

[0015] According to one embodiment of the invention, the reinforcement is a thermally conductive three-dimensional structure in the form of a set of assembled, preferably welded, metal wires. Preferably, the feed fibers are braided, over at least part of their length, onto the reinforcement.

[0016] According to one embodiment of the invention, at least one of the hair fiber / feed fiber contact areas being formed by a knot of the hair fiber around the feed fiber, said knot extends around a part of the reinforcement.

[0017] The invention further relates to an assembly comprising at least one heat source cooled by an airflow and a device for cooling said source of heat, the cooling device being positionable in the cooling airflow of the heat source and in contact with the heat source, said cooling device comprising a network of fibers capable of being supplied by a water supply system, characterized in that the cooling device is of the aforementioned type. Brief description of the drawings

[0018] The invention will be better understood upon reading the following description of exemplary embodiments, with reference to the accompanying drawings in which:

[0019] [Fig-1] represents a schematic perspective view of a device cooling according to the invention in the configuration of use and the assembly comprising such a device;

[0020] [Fig.2] represents a schematic perspective view of a device cooling according to the invention in the configuration of use and the assembly comprising such a device;

[0021] [Fig.3] represents a schematic view illustrating the formation of a fiber knot capillary around a nourishing fiber.

[0022] As mentioned above, the invention relates to a device 1 for cooling a heat source 20 cooled by an airflow 21. Although the heat source 20 can be varied, provided that it has a surface temperature below 100°C and is able to withstand the presence of water at the point of contact with the cooling device 1, the invention applies more particularly to the case where the heat source 20 is part of a heat exchanger of a refrigeration installation, such as the condenser of a refrigeration circuit.

[0023] In such an application, the cooling device 1 makes it possible to reduce the energy consumption of the refrigeration system and increase its cooling capacity under extreme climatic conditions, particularly during high air temperatures resulting, for example, from a heat wave. The heat source may, alternatively, be a power electronic component and, more generally, any device that needs to be cooled by an airflow. The airflow 21 intended to cool such a heat source 20 may be produced naturally by convection or forced by a fan or any other forced air circulation system. This airflow 21 is directed towards the cooling device 1 and, in the case of forced air circulation, towards the heat source 20 that is to be cooled by the cooling device 1.The cooling device 1 is therefore intended to be positioned in the airflow 21 cooling the heat source 20 and in contact with the heat source 20. The heat source 20 is configured in a known, predetermined manner. This source. 20 of heat extends at least partially under the cooling device 1 in the cooling device 1 usage configuration.

[0024] This cooling device 1 includes a self-supporting frame 3 comprising an upper part 4 and an opposite lower part, called a base 5, by which the frame 3 rests in support in an upright configuration corresponding to the configuration of use of the cooling device 1.

[0025] In this upright configuration, the cooling device 1 is in contact with their heat source 20 when it is positioned at least partially above this heat source 20 and is disposed in the airflow 21, as illustrated in Figures 1 and 2. The armature 3 can have a wide variety of shapes. Generally, the armature 3 is a thermally conductive three-dimensional structure in the form of a set of metallic wires 10, preferably joined by welding. The metal can be stainless steel, aluminum, or another material. This armature 3 therefore comprises so-called longitudinal wires that extend along the airflow and so-called transverse wires that extend transversely to the airflow. These transverse wires can extend vertically or horizontally to give the armature its three-dimensional shape.

[0026] Figure 1 illustrates an embodiment in which the heat source 20 is a flat, horizontal source and the cooling device 1 is placed on said heat source 20. The frame 3 is formed here of two parallel vertical wire frames connected by metal wires forming crossbars located at least between the upper horizontal edges of the frames. The airflow moves along said frames from one of the vertical edges towards the opposite vertical edge of the frames. The lower horizontal edges of the frames form the base 5 of the frame 3, while the upper horizontal edges of the frames form the upper part 4 of the frame 3.

[0027] Figure 2 illustrates an embodiment in which the heat source 20 is cylindrical and the cooling device 1 spans the heat source so that the armature can bear against a surface other than the heat source. Again, the armature 3 is formed of two parallel vertical wire frames connected by metal wires forming crossbars arranged between the upper horizontal edges of the frames. Each frame has a horizontal upper edge, two vertical edges, and a concave lower edge with a cavity facing outwards from the frame to form a bridge spanning said heat source 20.

[0028] The airflow 21 moves again along the frames from one of the vertical edges towards the opposite vertical edge of the frames. The lower horizontal edge of the frames forms the base 5 of the frame 3, while the upper horizontal edges of the frames form the upper part of the frame 3.

[0029] The cooling device 1 comprises a network 2 of fibers adapted to be supplied by a water supply system 22. The network 2 of fibers is coupled to the frame 3 to form a perforated barrier adapted to allow passage of the cooling airflow 21 from the heat source 20. This network 2 of fibers comprises a first series of feeder fibers 6 adapted to be supplied with water by the water supply system 22 and a second series of capillary fibers 7.

[0030] The water supply system 22 can be implemented simply as illustrated in the figures. It simply requires a reservoir whose level is maintained constant, for example, by means of a float. This float allows for the opening and closing of a valve connecting the reservoir to a water supply network. Each feed fiber 6 enters the reservoir at one of its ends, preferably through the bottom of the reservoir, as illustrated in Figures 1 and 2. The water supply system 22 can be formed by a pump. Generally, the water supply system 22 is configured to deliver water at a pressure that can vary from 1 to 5 mbar. Alternatively, the water supply system 2 can be a misting system directed towards the feed fibers 6. It should be noted that a capillary fiber or feed fiber is understood to mean a plurality of individual strands joined together by threading.

[0031] The connection point of the feed fibers to the water supply system 22 is arranged at a higher level than that occupied by the cooling device 1 to allow water to be supplied to the feed fibers by gravity from the device of the water supply system 22.

[0032] Each feed fiber 6 therefore has a section developing vertically in the configuration of use of the cooling device 1 before developing along the base of the frame 3, ideally following the direction of the airflow, then going up to the upper part of the frame 3 where said fibers are preferably attached by knotting to said frame 3. The feed fibers 6 are fibers chosen from the group formed by flax, hemp, jute, sisal, wool fibers, these fibers being alone or in a mixture with artificial fibers representing at most 40% expressed by weight of said mixture.

[0033] In the example shown, the feed fibers 6 are fibers composed of 55% wool and 45% artificial fibers such as polyamide fibers. Preferably, at least one, preferably each, of the feed fibers has wettability expressed as an angular value corresponding to the contact angle formed between the surface of the feed fiber 6 and the wall of a water droplet deposited on said surface, this contact angle being less than 60 degrees. To determine the contact angle, a goniometer is used in conjunction with commercially available image processing software. The goniometer incorporates a mini camera which allows Take pictures of small areas. The associated image processing software allows the pictures to be processed digitally to enable the measurement of the contact angle.

[0034] In practice, to determine the contact angle of the feed fibers of the cooling device 1, the following procedure can be used: the fiber is stretched horizontally between two bars, and a 5 ml drop of water is carefully placed on the fiber. The scene is filmed, and the images allow the contact angle to be determined by lateral visualization of the drop's shape. The drop penetrates the fiber when the contact angles are very small.

[0035] The feeder fibers 6 have a diameter between 1.5 and 3.7 millimeters. These feeder fibers 6 have a porosity between 50 and 90%, preferably close to 60%. The porosity is determined by measuring the volume change of the feeder fibers by humidification or tomography. In practice, the procedure is as follows: the fiber is stretched vertically and placed on a rotating base. The fiber is rotated 360° and X-rayed during this rotation. The X-ray images are analyzed to reconstruct the three-dimensional structure of the fiber. Reconstructed images of the volume are extracted at different heights. These images are binarized to identify the solid parts within the fiber. The porosity is deduced from the ratio of the solid volume to the total volume, averaged over several heights.Preferably, at the level of their vertical path, the feeder fibers are braided over at least part of their length on the frame 3.

[0036] The second series of fibers is formed by so-called capillary fibers 7. At least a portion of the capillary fibers 7 surrounds at least partially the feeder fibers 6 to form at least one contact zone 8. These capillary fibers 7 grow upwards from the contact zone 8 between the capillary fiber 7 and the feeder fiber 6 towards the upper part of the frame 3 so that they can extend over at least part of their length in a substantially vertical manner in the operating configuration of the cooling device 1.

[0037] At least a portion of the contact areas 8 between the capillary fiber 7 and the feed fiber 6 extends below at least a portion of the base 5 of the frame 3 in the configuration for use of the cooling device 1, to form the area or a portion of the cooling device 1 capable of coming into contact with the heat source 20. Thus, a portion of the contact areas 8 between the capillary fiber 7 and the feed fiber 6 forms the interface between the cooling device 1 and the heat source 20.

[0038] Figure 1 illustrates an embodiment with three feeder fibers and capillary fibers connected at intervals to the horizontal portion of each feeder fiber before ascending towards the upper part of the frame to... be held by a knot or other. At least one, preferably each, contact zone 8 hair fiber 7 / feed fiber 6 is formed by a knot 9 of the hair fiber 7 around at least the feed fiber 6. At some of these contact zones 8, the knot 9 also extends around a part of the framework 3, as is the case for example in [Fig.1] at the two lower horizontal edges of the vertical frames constituting the framework.

[0039] To allow precise positioning of the contact zones 8, and in particular to ensure that some of the contact zones 8 are at the same level, in order to guarantee that these contact zones 8 constitute the interface between the heat source 20 and the cooling device 1, the knot 9 of the capillary fiber around the feed fiber 6, or of the feed fiber 6 and the reinforcement 3, can be made as illustrated in [Fig. 3] using an attached cylindrical bar 11. This cylindrical bar 11 is temporarily fixed to the reinforcement 3 below the base 5 of the reinforcement 3. This bar 11 serves as a support for tightening the knot and ensures secure positioning of the knot. The feed fiber passes over this bar 11, and the capillary fiber 7 is wrapped around the feed fiber 6 and the bar 11 with a simple knot. The bar is then removed at the end of the fiber network fabrication. The knot can then be tightened.A similar process can be used when the knot encircles the feeder fiber 6 and a reinforcing wire 3. In this case, the knot is made at a location where the feeder fiber 6 extends along a reinforcing wire 3. The hair fibers 7 are plant fibers containing between 65% and 85%, expressed as a percentage by weight of cellulose relative to the total weight of the hair fibers 7. These hair fibers 7 can be selected from the group formed by flax, hemp, jute, and sisal fibers. In the example shown, these fibers are composed of sisal.

[0040] The hair fibers 7 exhibit, at an ambient temperature of 25°C and under conditions of relative humidity above 80%, a water retention rate corresponding to the amount of water that said fibers can absorb per unit weight greater than 10%. The water retention rate can be measured as follows: 10 mg of fibers are placed in a temperature- and humidity-controlled chamber on the platform of a weighing balance. The fibers are exposed to increasing humidity levels and are weighed at each level once their mass has stabilized.

[0041] The capillary fibers 7 are configured so that, in the operating configuration of the cooling device 1 and in the water-supplied state of the feed fibers 6, they exhibit a capillary rise height from the contact zones 8 of capillary fibers 7 / feed fibers 8 of at least 6 cm.

[0042] To measure the capillary rise height, the following procedure is used: the fibers are stretched vertically on a stand, and the base of the stand is placed in a water tank. Water rises along the fibers, and its presence is detected by measuring the temperature using infrared thermography. The fiber temperature is lowered in the wetted areas. The images taken by the infrared thermographic camera are processed to measure the height of the cooled fiber relative to the height of the liquid in the tank. The rise height is the height measured after 24 hours of stabilization. Capillary fibers generally have a diameter between 1.5 and 4 mm.

[0043] The invention also relates to an assembly comprising at least one heat source 20 cooled by an airflow 21 and a cooling device 1 for said heat source 20, the cooling device 1 being positionable in the airflow 21 cooling the heat source 20 and in contact with the heat source 20. Said cooling device 1 comprises a network 2 of fibers adapted to be supplied with water by a water supply system 22, and this cooling device 1 may be of the type described above.

[0044] The design of the cooling device 1 allows for its removable positioning in contact with the heat source 20. Maintenance of such a cooling device 1 is therefore particularly easy. Ideally, the assembly includes a dedicated receiving position for the cooling device 1. When the cooling device 1 is positioned in this position, it is in contact with the heat source 20 and in the path of the airflow 21.

[0045] The operation of the cooling device 1 as described above, integrated into an assembly, is as follows. It is assumed that the cooling device 1 is positioned in contact with the heat source 20 by positioning at least part of the cooling device 1 above the heat source until the cooling device 1 rests on the surface of the heat source or on the surface surrounding said heat source. The heat source is of predetermined shape and dimensions known to ensure contact between at least a portion of the feed fiber / capillary fiber contact areas of the cooling device 1 and said heat source. In this position, the armature is held upright and rests on its base. The feed fibers are connected to the water supply system 22 or are subjected to the action of the water supply system 22.In this usage configuration, the cooling device 1 is placed in the airflow 21 which is used to cool the heat source. Water from the water supply system 22 feeds the feed fibers which carry this water to the feed fiber / contact zones. A capillary fiber is a network of capillaries where water rises by capillary action. The airflow passing through this network is cooled by the evaporation of the water it absorbs upon contact with the capillaries. This air cooling allows for increased cooling of the heat source. In particular, when this heat source is an air-cooled condenser of a refrigeration machine, the cooling device 1 improves the efficiency of the refrigeration machine.

Claims

1.

2. Demands A device (1) for cooling a heat source (20) cooled by an airflow (21), the cooling device (1) being positionable in the airflow (21) cooling the heat source (20) and in contact with the heat source (20) intended to extend at least partially below the cooling device (1), said cooling device (1) comprising a network (2) of fibers capable of being supplied with water by a water supply system (22), characterized in that the cooling device (1) comprises a self-supporting frame (3) comprising an upper part (4) and an opposing lower part called a base (5) by which the frame (3) rests in an upright configuration corresponding to the operating configuration of the cooling device (1),in that the fibre network (2) is coupled to the frame (3) to form a perforated barrier suitable for the passage of the cooling air flow (21) from the heat source (20) and in that the fibre network (2) comprises a first series of feeder fibre (6) suitable for being supplied with water by the water supply system (22) and a second series of capillary fibre (7), at least part of the capillary fibre (7) at least partially surrounding the feeder fibre (6) to form at least one contact zone (8), these capillary fibre (7) developing from the contact zone (8) capillary fibre (7) / feeder fibre (6) towards the upper part (4) of the frame (3) so as to be able to extend over at least part of their length in a substantially vertical manner in the operating configuration of the cooling device (1),at least a portion of the contact zones (8) of the capillary fiber (7) / feeder fiber (6) extending below at least a portion of the base (5) of the armature (3) in the configuration of use of the cooling device (1) to form the portion of the cooling device (1) capable of coming into contact with the heat source (20). Cooling device (1) according to claim 1, characterized in that at least one of the contact zones (8) hair fiber (7) / feed fiber (6) is formed by a knot (9) of the hair fiber (7) around at least the feed fiber (6).

3. Cooling device (1) according to any one of claims 1 or 2, characterized in that the hair fibers (7) are plant fibers containing between 65 and 85% expressed as a percentage by weight of cellulose relative to the total weight of the hair fibers (7).

4. Cooling device (1) according to any one of claims 1 to 3, characterized in that the capillary fibers (7) are selected from the group formed by flax, hemp, jute, sisal fibers

5. Cooling device (1) according to any one of claims 1 to 4, characterized in that the capillary fibers (7) exhibit, at an ambient temperature of 25°C and under conditions of relative humidity of the ambient air greater than 80%, a water retention rate, corresponding to the quantity of water that said fibers can absorb per unit weight, greater than 10%.

6. Cooling device (1) according to any one of claims 1 to 5, characterized in that at least a portion of the capillary fibers (7) are configured to, in the operating configuration of the cooling device (1) and in the water-supplied state of the feed fibers (6), exhibit a capillary rise height from the areas (8) of contact between capillary fiber (7) and feed fiber (6) of at least 6 cm.

7. Cooling device (1) according to any one of claims 1 to 6, characterized in that the feed fibers (6) are fibers selected from the group formed by flax, hemp, jute, sisal, wool fibers, these fibers being alone or mixed with artificial fibers representing at most 40% expressed by weight of said mixture.

8. Cooling device (1) according to any one of claims 1 to 7, characterized in that at least one of the feed fibers (6) has a wettability expressed as an angular value corresponding to the contact angle formed between the surface of said feed fiber (6) and the wall of a water droplet deposited on said surface, this contact angle being less than 60°.

9. Cooling device (1) according to any one of claims 1 to 8, characterized in that the feed fibers (6) have a diameter between 1.5 and 3.7 mm and the capillary fibers (7) have a diameter between 1.5 and 4 mm.

10. Cooling device (1) according to any one of claims 1 to 9, characterized in that the feed fibers (6) have a porosity between 50 and 90%, preferably close to 60%.

11. Cooling device (1) according to any one of claims 1 to 10, characterized in that the armature (3) is a thermally conductive three-dimensional structure in the form of a set of assembled, preferably welded, metallic wires (10).

12. Cooling device (1) according to any one of claims 1 to 11, characterized in that at least one of the contact zones (8) hair fiber (7) / feed fiber (6) being formed by a knot (9) of the hair fiber (7) around the feed fiber (6), said knot (9) extends around a part of the frame (3).

13. Assembly comprising at least one heat source (20) cooled by an airflow (21) and a device (1) for cooling said heat source (20), the cooling device (1) being positionable in the airflow (21) for cooling the heat source (20) and in contact with the heat source (20), said cooling device (1) comprising a network (2) of fibers connectable to a water supply system (22), characterized in that the cooling device (1) conforms to any one of claims 1 to 12.

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