Device for cooling a heat source cooled by an air flow and assembly comprising such a cooling device

Abstract

The invention relates to a cooling device (1) that can be positioned in the cooling air flow (21) of a heat source (20) and in contact with that source (20), which cooling device (1) comprises a network (2) of fibres, and further comprises a free-standing frame (3) having a base (5) by which the frame (3) bearingly rests in an upright configuration corresponding to the configuration of use of the device (1). The network (2) of fibres is coupled to the frame (3) to form an openwork barrier through which the flow (21) of cooling air passes, and comprises a first series of feeder fibres (6) capable of being supplied with water by a water supply system (22), and a second series of capillary fibres (7). Capillary fibres (7) at least partially surround the feeder fibres (6) to form an area (8) of contact. These capillary fibres (7) extend from the area (8) of contact between the capillary fibre (7) and the feeder fibre (6) towards the upper part (4) of the frame (3), with part of the areas (8) of contact between the capillary fibre (7) and the feeder fibre (6) extending beneath the base (5) of the frame (3) in the configuration of use of the cooling device (1).

Description

Description Title of the invention: DEVICE FOR COOLING A HEAT SOURCE COOLED BY AN AIR FLOW AND ASSEMBLY COMPRISING SUCH A DEVICE COOLING

[0001] The present invention relates to a device for cooling 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 fibres suitable for 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 heat source with a water-soaked cloth is known to improve cooling. This lowers the surface temperature of the heat source. However, this solution is very water-intensive and its cooling effects are limited.

[0004] One aim 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 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 includes 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 frame to form a perforated barrier suitable for passage by 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 capillary fibers, at least a part of the capillary fibers at least partially surrounding the feeder fibers to form at least one contact zone,These capillary fibers develop from the capillary fiber / feeder fiber contact zone towards the upper part of the frame so that they can extend over at least part of their length in a substantially vertical manner in the cooling device's operating configuration; at least part of the capillary fiber / feeder fiber contact zones extend below at least part of the base of the frame in the cooling device's operating 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 along at least part of their length between the base and the upper part of the frame in its operating configuration, and present at least one low point in contact with the feed fibers for capillary diffusion of the water contained in the feed fibers into the capillary fibers. It should be noted that the expression "substantially vertically"It is understood that the capillary fibers form an angle of less than 45° with the vertical along at least part of their length in the operating configuration of the cooling device. The design of the cooling device maximizes cooling by increasing the contact surface 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 by conduction at the contact point with the wet fibers. The air is cooled by evaporation of free water from the fibers. The fibers thus serve to diffuse liquid water through the interior of the fiber, while their outer surface, in contact with the air, The air allows the water to evaporate. As the water evaporates, the air cools. The arrangement of the capillary fibers, which grow upwards from the contact zone between the capillary fiber, the feeder fiber, and the heat source 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. Furthermore, the design of the cooling device, with its self-supporting structure that makes it easily removable, allows for simple 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, and 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 / feeder fiber contact zones being formed by a knot of the hair fiber around the feeder 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 cooling device for said heat source, 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, 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 attached drawings in which:

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

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

[0021] [Fig. 3] represents a schematic view illustrating the formation of a knot of a capillary fiber 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 allows for a reduction in the energy consumption of the refrigeration system and an increase in cooling capacity under extreme climatic conditions, particularly during periods of high air temperatures resulting, for example, from a heat wave. The heat source can alternatively be a power electronic component or, more generally, any device that needs to be cooled by an airflow. The airflow 21 intended to cool such a heat source 20 can be produced naturally by convection or forced by a fan or 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 it is to be cooled by the cooling device 1.The cooling device 1 is therefore intended to be positioned in the airflow 21 of the cooling of the heat source 20 and in contact with the heat source 20. Heat. The heat source 20 is configured in a known, predetermined manner. This heat source 20 extends at least partially under the cooling device 1 in the configuration for use of the cooling device 1.

[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 take many forms. Generally, the armature 3 is a thermally conductive, three-dimensional structure consisting of a set of metal wires 10, preferably joined by welding. The metal can be stainless steel, aluminum, or another material. This armature 3 therefore comprises longitudinal wires that extend along the airflow and 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 arranged 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 where 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 source. heat. Again, the frame 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 here 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 armature 3, while the upper horizontal edges of the frames form the upper part of the armature 3.

[0029] The cooling device 1 comprises a network 2 of fibers suitable for being supplied by a water supply system 22. The network 2 of fibers is coupled to the frame 3 to form a perforated barrier suitable for the passage of the cooling airflow 21 from the heat source 20. This network 2 of fibers comprises a first series of feeder fibers 6 suitable for being 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 requires a reservoir whose level is maintained constant, for example, by 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 end, preferably through the bottom of the reservoir, as illustrated in Figures 1 and 2. The water supply system 22 can be a pump. Generally, the water supply system 22 is configured to deliver water at a pressure ranging 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 defined as a plurality of individual strands joined together by threading.

[0031] The connection point of the feed fibers to the water supply system 22 is located 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 composed of 55% wool and 45% artificial fibers such as polyamide fibers. Preferably, at least one, and preferably each, of the feed fibers exhibits 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 miniature camera that allows for taking photographs of small areas. The associated image processing software allows for the computer processing of the photographs to enable the measurement of the contact angle.

[0034] In practice, to determine the contact angle of the feed fibers of 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 footage allows the contact angle to be determined by observing the shape of the drop laterally. 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 measured 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, for at least part of their length, in a substantially vertical manner when the cooling device 1 is in use.

[0037] At least a portion of the contact zones 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 zones 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 reinforcement to be held there by a knot or other means. At least one of Each preference, zone 8 of contact 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 frame 3, as is the case for example in Figure 1 at the two lower horizontal edges of the vertical frames constituting the frame.

[0039] To allow for precise positioning of the contact zones 8, and in particular to ensure that some of the contact zones 8 are at the same level, thus guaranteeing that these contact zones 8 form 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 Figure 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 11 is then removed at the end of the fiber network fabrication process. 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 consisting of 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 balance. weighing. The fibers are exposed to increasing levels of air humidity 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 feeder fibers 6, they exhibit a capillary rise height from the contact zones 8 of capillary fibers 7 / feeder 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 wet 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 typically 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 within 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 positioned in this position, the cooling device 1 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 has a 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 operating configuration, the cooling device 1 is positioned within the airflow 21 that cools the heat source. Water from the water supply system 22 feeds the feed fibers, which carry this water to the feed fiber / capillary fiber contact zones where the water rises by capillary action along the capillaries. The airflow passing through this capillary network is cooled by the evaporation of the water it absorbs upon contact with the capillaries. This air cooling provides increased cooling of the heat source. In particular, when this heat source is an air-cooled condenser of a refrigeration unit, the cooling device 1 improves the efficiency of the refrigeration unit.

Claims

Demands

1. 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 network (2) of fibers is coupled to the reinforcement (3) to form an openwork barrier suitable for passage by the flow (21) of cooling air from the heat source (20) and in that the network (2) of fibers comprises a first series of so-called feeder fibers (6) suitable for being supplied with water by the water supply system (22) and a second series of so-called capillary fibers (7), at least a part of the capillary fibers (7) at least partially surrounding the feeder fibers (6) to form at least one contact zone (8), these capillary fibers (7) developing from the contact zone (8) capillary fiber (7) / feeder fiber, (6) towards the upper part (4) of the armature (3) so as to be able to extend over at least part of their length substantially vertically in the configuration of use of the cooling device (1), at least part of the areas (8) of contact capillary fiber (7) / feed fiber (6) extending below at least part of the base (5) of the armature (3) in the configuration of use of the cooling device (1) to form the part of the cooling device (1) capable of coming into contact with the heat source (20).

2. Cooling device (1) according to claim 1, characterized in that at least one of the capillary fiber contact zones (8) (7) / feeder fiber (6) is formed by a knot (9) of the hair fiber (7) around at least the feeder 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 hair 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) of capillary fiber (7) / feeder fiber (6) being formed by a knot (9) of the capillary fiber (7) around the feeder 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 cooling device (1) for 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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