Liquid cooling device

Abstract

To provide a space-saving liquid cooling device having excellent heat dissipation performance.SOLUTION: A liquid cooling device according to the present invention includes a liquid inlet through which a liquid refrigerant flows and a liquid outlet through which the refrigerant flows out, at least a portion of the liquid cooling device is made of a porous body, and the liquid cooling device performs cooling by bringing the liquid refrigerant into contact with the porous body, and the average circle equivalent diameter of the cross section of pores present inside the porous body is 150 μm or more.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a liquid cooling device at least a part of which is made of a porous body. [Background technology]

[0002] Liquid cooling devices that use a liquid refrigerant to remove heat from a heat source are very commonly used in applications such as cooling electronic devices, industrial cooling towers, and thermal management of chemical reactions. Methods of improving cooling efficiency by devising the shape of heat dissipation bodies such as cooling fins are also known. There is also a method of using a porous body as a component of a liquid cooling device and dissipating heat by contacting the refrigerant with the porous body. The method of using a porous body is expected to provide effective cooling because the large surface area of ​​the porous body and the numerous small spaces present inside the porous body promote heat transfer between the refrigerant and the heat source.

[0003] Patent Document 1 discloses a liquid cooling device in which at least a part of the wall constituting the cooling flow path is a porous body. Among the examples described in Patent Document 1, a technology is disclosed that uses multiple porous bodies with different porosities, and a simulation result shows that the cooling efficiency differs depending on the porosity. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2021-134778 A Summary of the Invention [Problem to be solved by the invention]

[0005] Fin-shaped heat sinks have a high cooling capacity, but the drawback is that they require a large space. There is also a need to improve the cooling capacity beyond that of heat dissipation from a bulk metal surface. The cooling capacity of a liquid cooling device using a porous body is not determined solely by the porosity of the porous body. For example, the efficiency of heat exchange changes depending on factors such as the size of the pores present inside the porous body. An object of the present invention is to provide a space-saving liquid cooling device that has excellent heat dissipation performance. [Means for solving the problem]

[0006] The inventors of the present application have conducted extensive research into the configuration of a liquid cooling device that uses a porous body. They have found that not all porous bodies provide a high cooling effect. In particular, they have found that when liquid exchange inside the porous body is poor, the cooling performance may actually decrease. Therefore, in order to achieve the above-mentioned object, there is provided a liquid cooling device which has a liquid inlet through which a liquid refrigerant flows and a liquid outlet through which the refrigerant flows out, at least a portion of which is made of a porous body, and which performs cooling by bringing the liquid refrigerant into contact with the porous body, and in which the average circle equivalent diameter of the cross section of the pores present inside the porous body is 150 μm or more. In such a liquid cooling device, the porous body has a high heat dissipation performance with a small occupying volume, and can be used as a heat sink for electronic components, for example.

[0007] In one embodiment of the present invention, there is provided a liquid cooling device, wherein the proportion of the area occupied by pores in a cross section of a porous body is 20% or more.

[0008] In another embodiment of the present invention, a liquid cooling device is provided in which, when the height direction in a cross-section of a porous body is defined as the direction perpendicular to the main surface of the porous body, the area of ​​pores connecting from the upper side to the lower side of the field of view in the height direction within a field of view of 500 μm in height and 2000 μm in width is 40% or more of the total area of ​​pores present in the field of view.

[0009] In yet another embodiment of the present invention, there is provided a liquid cooling device, wherein the porosity of the porous body is 30% or more and 70% or less.

[0010] In yet another embodiment of the present invention, a liquid cooling device is provided, wherein the porous body is formed from a powder of a metal.

[0011] In yet another embodiment of the present invention, there is provided a liquid cooling device, wherein 90% or more of the metal powder has a particle size of 300 μm or more.

[0012] In yet another embodiment of the present invention, a liquid cooling device is provided, wherein the porous body is formed by a sintering process.

[0013] In yet another embodiment of the present invention, a liquid cooling device is provided, wherein the porous body is sintered directly to a metal plate. Effect of the Invention

[0014] According to the present invention, it is possible to provide a space-saving liquid cooling device with excellent heat dissipation performance. [Brief description of the drawings]

[0015] [Figure 1] 1A is a cross-sectional view of a first example of a liquid-cooling device according to the present embodiment, FIG. 1B is a cross-sectional view of a second example of a liquid-cooling device according to the present embodiment, and FIG. 1C is a cross-sectional view of a third example of a liquid-cooling device according to the present embodiment. [Diagram 2] 2 is a schematic cross-sectional view of a porous body that constitutes the liquid cooling device according to the embodiment. FIG. [Diagram 3] FIG. 2 is an explanatory diagram of through porosity. [Figure 4] The test results for each sample are shown. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. However, detailed description may be omitted. For example, detailed description of already well-known matters or duplicate description of substantially the same configuration may be omitted. Note that the accompanying drawings and the following description are provided to enable a person skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0017] Hereinafter, the present embodiment will be described with reference to FIGS. [1. Configuration] 1(a), 1(b), and 1(c) are cross-sectional views of an example of a liquid cooling device 1 according to this embodiment.

[0018] (Configuration of Example 1) The liquid cooling device 1 according to the first embodiment includes a liquid cooling device outer wall 30 that holds a liquid to be cooled. The liquid cooling device outer wall 30 includes a liquid inlet 10, which is an inlet through which the liquid, which is a refrigerant, flows, and a liquid outlet 20, which is an outlet for the liquid that has completed the heat exchange. The porous body 40 that performs the heat exchange is supported by a support part 50, and the support part 50 and the liquid cooling device outer wall 30 form, for example, a box-shaped closed space so that the liquid does not leak. In this case, the main surface 45 of the porous body 40 may be metal-bonded to the support part 50. Here, the main surface 45 of the porous body 40 means the surface having the largest area in contact with the support part 50. A joint part 60 having high thermal conductivity is provided between the heat source 70, which is the object to be cooled, and the support part 50. A thermocouple 80 for measuring the temperature of the heat source 70 is provided around the heat source 70.

[0019] The liquid used in the liquid cooling device 1 is, for example, water, oil, LLC (Long Life Coolant), or other cooling liquid, and any liquid commonly used in liquid cooling devices may be used, with a liquid that is less likely to corrode metal being preferred. The cooling liquid is cooled by a chiller (not shown) that performs cooling processing using, for example, a heat pump cycle, and circulates within the cooling system including the liquid cooling device 1.

[0020] The joint 60 may be any heat conductive material, such as a highly thermally conductive grease or sheet.

[0021] (Configuration of Example 2) FIG. 1(b) is a diagram showing the configuration of another embodiment of the liquid cooling device 1. In this embodiment, the liquid cooling device outer wall 30 and the support part 50 supporting the porous body 40 are integral with each other to form a box-shaped closed space. In this case, the main surface 45 of the porous body 40 may be metal-joined to the liquid cooling device outer wall 30. As in the above-mentioned embodiment 1, the liquid cooling device 1 in this embodiment has a liquid inlet 10 and a liquid outlet 20. A joint part 60 having high thermal conductivity is provided between the heat source 70, which is the object to be cooled, and the support part 50. A thermocouple 80 for measuring the temperature of the heat source 70 is provided around the heat source 70. However, the thermocouple is not an essential component.

[0022] (Configuration of Example 3) 1(c) is a diagram showing the configuration of another embodiment of the liquid cooling device 1. In this embodiment, the liquid cooling device outer wall 30 and the heat source 70 form a box-shaped closed space. In this case, the main surface 45 of the porous body 40 may be metal-joined to the heat source 70. As in the above-mentioned embodiment 1, the liquid cooling device 1 in this embodiment includes a liquid inlet 10 and a liquid outlet 20. A thermocouple 80 for measuring the temperature of the heat source 70 is provided around the heat source 70. Although not shown, the heat source 70 itself may form a box-shaped closed space, and the liquid inlet 10 and the liquid outlet 20 may be formed. In this case, the heat source 70 and the main surface 45 of the porous body 40 may be joined by metal bonding.

[0023] FIG. 2 is a schematic cross-sectional view of the porous body 40 in the liquid cooling device 1 described above. Specifically, for example, in the above-mentioned Example 1, when the joint surface between the porous body 40 and the support part 50 is set in the XY direction, this is a schematic cross-sectional view perpendicular to the joint surface. The porous body 40 is composed of a porous part 90 and a void part 100 which is a gap between the porous part 90 and the void part 100. The void part 100 realizes a three-dimensionally connected mesh-like space. The liquid for cooling enters the void part 100 and exchanges heat. Pure water or LLC may be used as the liquid for cooling. At this time, it is desirable that the average value of the circle equivalent diameter of the cross section of the void part 100 is 150 μm or more and 500 μm or less. If the voids are too small, heat exchange becomes difficult. Also, if the voids are too large, the minimum required mechanical strength for processing and installation cannot be satisfied. The optimal size of the pores 100 may vary depending on the type of refrigerant and the material of the porous body, but the inventors have obtained experimental results that show that when the refrigerant is pure water and the porous body 40 is formed of pure aluminum or an aluminum alloy, it is desirable for the average circle-equivalent diameter of the cross section of the pores 100 to be 150 μm or more.

[0024] Here, the average value of the circle-equivalent diameters of the pores 40 refers to the average value of the diameters of perfect circles equivalent to the area of ​​the cross sections of the pores 40. For example, the average value is calculated for the cross sections of all the pores 40 within the field of view of the microscope. Moreover, the proportion of the area occupied by the pores 40 in the cross section of the porous body 40 is 20% or more. It is desirable that the proportion of the area occupied by the pores 40 in the cross section of the porous body 40 is 30% or more and 70% or less. The condition that the proportion of the area occupied by the pores 40 is 70% or less satisfies mechanical strength suitable for processing, installation, etc. of the porous body 40, and leads to preventing a decrease in the thermal conductivity of the entire porous body 40 due to large internal pores. The porosity of the porous body 40 is 30% or more and 70% or less. It is more preferable that the porosity of the porous body 40 is 40% or more and 60% or less.

[0025] The porous body 40 is produced by sintering metal powder. Of course, the porous body 40 may be produced by other methods. For example, it may be produced by wet plating or by a 3D printer. However, it is preferable to produce the porous body by a sintering method of metal powder, which increases the surface area of ​​the pores 100. When produced by a sintering method, a porous body can be produced in which complex flow paths are formed inside and the pores 100 are created while ensuring strength. At this time, one type of metal powder for the base material is selected from pure aluminum powder, aluminum alloy powder, or a mixed powder of pure aluminum and aluminum alloy. Of course, the metal of the metal powder may be copper or a copper alloy, or other metal. It is preferable that 90% or more of the metal powder has a particle diameter of 300 μm or more. Here, in this specification, the amount means, for example, weight percent or volume percent, but it is preferable to control it by weight percent. The metal powder is divided into balls, which is an operation to separate the metal powder according to its size, to produce a powder with an appropriate particle size distribution. When other powders are added separately, they are mixed when the appropriate particle size distribution is achieved. Sintering is desirably carried out stepwise at temperatures of about 550° C. to 670° C. in a reducing atmosphere.

[0026] The adhesion between the porous body 40 and the liquid cooling device 1 is preferably achieved by directly sintering the porous body 40 to the supporting part 50 in the above-mentioned Example 1, but may also be achieved by a method such as welding or pressure welding, or by connection with an adhesive or adhesive tape. When the porous body 40 is formed on the supporting part 50 by direct sintering, there is no need for an adhesion process for adhering the porous body 40 to the supporting part 50, which is favorable for mass production.

[0027] 3(a) and 3(b) are explanatory diagrams of the through porosity in the porous body 40. FIG. 3(a) is a schematic diagram of an observation field when the cross section of the porous body 40 is observed with a microscope, for example, in the Y direction (width direction) of 2000 μm and the Z direction (height direction) of 500 μm. The through porosity is defined as the ratio of the area of ​​the pores in which all the pores 110 are connected from the upper side to the lower side in the observation field when the cross section is viewed, to the area of ​​the entire pores. In the case of FIG. 3(a), all the pores 110 are connected from the upper side to the lower side between the upper side 95 and the lower side 97 of the field of view, and the through porosity is 100%. In the case of FIG. 3(b), all the pores 120 are not connected from the upper side to the lower side between the upper side 95 and the lower side 97 of the field of view, and the through porosity is 0%. In the case of the porous body 40 used in the liquid cooling device 1 according to this embodiment, for example in the above-mentioned Example 1, when the joint surface between the porous body 40 and the support part 50 is in the XY direction, in a cross section perpendicular to the joint surface, when the observation field is 2000 μm in the Y direction and 500 μm in the Z direction, the through porosity is preferably 40% or more, and more preferably 50% or more. Due to these characteristics, the cooling liquid can easily pass through the internal space of the porous body 40, facilitating heat exchange.

[0028] [2. Experimental Results] Table 1 shows the experimental results when the liquid cooling device 1 has the configuration according to the above-mentioned Example 1. The porous body 40 used in the experiment is an approximately rectangular parallelepiped, with a main surface 45 parallel to the opposing support part 50, a square shape with a side of 50 mm, and a thickness direction perpendicular to the first plane of 1 mm. Here, the cooling performance is compared with the case where a bulk Al plate is provided on the support part 50 instead of the porous body 40. In the table, double circles and single circles indicate that the cooling performance is superior to the Al plate, and triangular marks indicate that the cooling performance is the same as that of the Al plate. Also, x marks indicate that the cooling performance is inferior to that of the Al plate. Here, the cooling performance of the porous body 40 means the heat dissipation performance in which heat is dissipated from a heat source through the porous body. [Table 1]

[0029] FIG. 4 shows the results of a comparative experiment on cooling performance between Example No. 1, Example No. 2, Example No. 5, Example No. 4, and Example No. 9 shown in Table 1 and an Al plate. Specifically, the final temperature in the liquid cooling device 1 is compared when pure water is cooled and circulated by a cooling chiller and left for one hour. Specifically, when heat is absorbed from the heat source 70 and heat exchange is properly performed in the porous body 40, the final temperature measured by the thermocouple 80 becomes lower. The vertical axis is the final temperature. This experiment was performed under the condition of refrigerant circulation such that the final temperature in the Al plate is 50°C. Example No. 1 had the best cooling performance, and it was found that the final temperature tends to be lower when the through porosity is high, that is, the cooling capacity tends to be superior. Conversely, it was found that when the through porosity is low (for example, Example No. 4 and Example No. 9), the cooling performance tends to be lower than that of the Al plate. This is thought to be because the pores inside the porous body 40 are not connected perpendicularly to the main surface 45, causing the insulating effect to become dominant, resulting in reduced cooling performance in the porous body 40.

[0030] [3. Effects, etc.] (Configuration 1) The liquid cooling device of this embodiment is provided with a liquid inlet through which liquid refrigerant flows and a liquid outlet through which the refrigerant flows out, and is at least partially constructed of a porous body, and performs cooling by bringing the liquid refrigerant into contact with the porous body, and the liquid cooling device provides a liquid cooling device in which the average circle equivalent diameter of the cross section of the pores present inside the porous body is 150 μm or more. It would seem that the smaller the pores inside a porous body, the easier it is for the refrigerant to be trapped in the pores due to capillary action, and the more efficient the heat exchange would be. However, if the pores are too small, the refrigerant will remain in the pores, and the efficiency of heat exchange will actually decrease. When the average circle-equivalent diameter of the cross section of the pores present inside the porous body constituting at least a part of the liquid cooling device according to this embodiment is 150 μm or more, the exchange of refrigerant between the inside and outside of the pores becomes active, resulting in improved heat exchange efficiency.

[0031] (Configuration 2) The liquid-cooling device according to the present embodiment is characterized in that the ratio of the area of ​​the pores to the cross section of the porous body is 20% or more. If the size of the pores present inside the porous body is too small, the refrigerant will remain inside the pores, reducing the efficiency of heat exchange. When the cross-sectional area of ​​the porous body constituting at least a part of the liquid cooling device in this embodiment is occupied by the pores at a ratio of 20% or more, the exchange of refrigerant between the inside and outside of the pores becomes active, resulting in improved heat exchange efficiency.

[0032] (Configuration 3) The liquid cooling device according to this embodiment provides a liquid cooling device as described in configuration 1 or 2, in which, when the height direction in a cross section of the porous body in the liquid cooling device is defined as the direction perpendicular to the main surface of the porous body, the area of ​​the holes connecting from the upper side to the lower side of the field of view in the height direction within a field of view of 500 μm in height and 2000 μm in width is 40% or more of the total area of ​​the holes present in the field of view. In the porous body constituting at least a part of the liquid cooling device in this embodiment, if a large proportion of the pores penetrate in the vertical direction, the refrigerant that has completed heat exchange can easily escape, resulting in improved heat exchange efficiency.

[0033] (Configuration 4) The liquid-cooling device according to the present embodiment has a porosity of the porous body of 30% or more and 70% or less. In general, for porous bodies, there is a correlation between a high porosity and a large internal surface area. Therefore, for heat dissipation, it is desirable for the porosity of the porous body to be high. However, when the porosity is high, the thermal conductivity of the entire porous body decreases, and the strength of the porous body itself also decreases. When the porosity of the porous body constituting at least a part of the liquid cooling device according to this embodiment is within the above-mentioned range, it has an excellent effect of being able to achieve both a high heat exchange rate and the strength of the porous body itself.

[0034] (Configuration 5) The liquid-cooling device according to the present embodiment provides a liquid-cooling device as recited in any one of configurations 1 to 4, wherein the porous body in the liquid-cooling device is made of metal powder. Metal particles of desired particle size are available at a relatively low cost, so forming a porous body from metal particles is inexpensive and highly controllable, which has the effect of making it easy to form a porous body that has both a high heat exchange rate and a high strength of the porous body itself.

[0035] (Configuration 6) The liquid cooling device according to the present embodiment provides a liquid cooling device as recited in Configuration 5, wherein the porous body has a particle diameter of 90% or more of the metal powder of 300 μm or more. This has the effect of facilitating the formation of a porous body that has both a high heat exchange rate and a high strength of the porous body itself. (Configuration 7) The liquid-cooling device according to the present embodiment is characterized in that the porous body is formed by a sintering method. The sintering method allows control of the microstructure of the porous body (e.g., porosity) by controlling the particle shape, size, distribution, and sintering temperature and time. In addition, the sintering method melts the metal particles together and bonds them firmly, resulting in a porous body with high strength and durability. This has the effect of making it easy to form a porous body that has both a high heat exchange rate and high strength of the pores themselves.

[0036] (Configuration 8) 8. The liquid cooling device according to claim 7, wherein the porous body is directly sintered onto a metal plate. Since there is no need for a bonding process for bonding the porous body to a base metal plate, this method has the advantage of being easy to mass-produce and makes it easy to form a porous body that combines a high heat exchange rate with the strength of the porous body itself.

[0037] It should be noted that the above-described embodiments are intended to illustrate the technology of the present disclosure, and various modifications, substitutions, additions, omissions, and the like can be made within the scope of the claims or their equivalents. [Industrial Applicability]

[0038] The present disclosure can be applied to a liquid cooling device that removes heat from a heat source by using a refrigerant, specifically, the present disclosure can be applied to liquid cooling used for dissipating heat from electronic components. [Explanation of symbols]

[0039] 1 Liquid cooling device 10 Liquid inlet 20 Liquid outlet 30 Liquid cooling device outer wall 40 Porous bodies 45 Main Surface 50 Support part 60 Joint 70 Heat source 80 Thermocouple 90 Porous part 95 Upper Vision 97 Bottom of the Field of View 100 Hole 110 Through hole 120 Non-penetrating hole

Claims

1. A liquid cooling device comprising a liquid inlet through which a liquid refrigerant flows and a liquid outlet through which the refrigerant flows out, at least a portion of which is made of a porous body, and which performs cooling by bringing the liquid refrigerant into contact with the porous body, wherein the average circle equivalent diameter of the cross section of pores present inside the porous body is 150 μm or more.

2. 2. The liquid cooling device according to claim 1, wherein a ratio of an area of ​​the pores to a cross section of the porous body is 20% or more.

3. A liquid cooling device as described in claim 1 or claim 2, wherein, in a cross-section of the porous body, when the height direction is defined as the direction perpendicular to the main surface of the porous body, the area of ​​the holes connecting from the upper side to the lower side of the field of view in the height direction in a field of view of 500 μm in height and 2000 μm in width is 40% or more of the total area of ​​the holes present in the field of view.

4. 4. The liquid cooling device according to claim 3, wherein the porosity of the porous body is 30% or more and 70% or less.

5. The liquid cooling device according to claim 4 , wherein the porous body is made of a metal powder.

6. 6. The liquid cooling device according to claim 5, wherein 90% or more of the metal powder has a particle size of 300 [mu]m or more.

7. The liquid cooling device according to claim 6 , wherein the porous body is formed by a sintering method.

8. The liquid cooling device according to claim 7 , wherein the porous body is directly sintered onto a metal plate.

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