Heat transfer member and method for manufacturing heat transfer member

Abstract

A heat transfer member is applied to a cooling device (100) for cooling an object to be cooled (70) in a state in which the object to be cooled (70) is immersed in a liquid-phase refrigerant, and promotes heat transfer from the object to be cooled (70) to the refrigerant. The object to be cooled (70) is an electronic device. The refrigerant is a fluorine-based insulating refrigerant having a boiling point of 100 DEG C or less. The refrigerant is open to the atmosphere. The heat transfer member has a degree of superheat dT of 10K and a heat flux q of 300 kW / m2 on a boiling curve in which the horizontal axis is the degree of superheat dT of the refrigerant and the vertical axis is the heat flux q. Wherein the degree of superheat dT is a value obtained by subtracting the saturation temperature Ts of the refrigerant from the temperature Tw of the heat transfer member. The heat flux q is the amount of heat per unit area transferred from the heat transfer unit to the refrigerant.

Description

[0001] Cross-reference to related applications

[0002] This application is based on Japanese Patent Application No. 2022-173289 filed on October 28, 2022, and the contents thereof are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to a heat transfer component used in a cooling device of an ebullient cooling type. Background Art

[0004] Conventionally, a boiling cooling type cooling device is disclosed in Patent Document 1, which cools a cooling object such as an electronic component that generates heat during operation while being immersed in a liquid refrigerant (in other words, refrigerant liquid). In the boiling cooling type cooling device, the refrigerant liquid is boiled using the heat generated by the cooling object, and the cooling object is cooled using the latent heat of vaporization when the refrigerant liquid vaporizes.

[0005] In addition, the cooling device of Patent Document 1 includes a heat transfer component for promoting heat transfer from the cooling object to the refrigerant and a circulation pump for pressurizing the refrigerant liquid toward the heat transfer component. The heat transfer component of Patent Document 1 has a fin portion, which is formed with a plurality of fins for increasing the contact area between the heat transfer component and the refrigerant liquid.

[0006] Furthermore, in the cooling device of Patent Document 1, by causing the refrigerant liquid pumped from the circulation pump to collide with the heat transfer component, particles of the gas phase refrigerant (in other words, bubbles) generated in the grooves formed between adjacent fins are squeezed out of the grooves. Thus, in the cooling device of Patent Document 1, boiling of the refrigerant near the heat transfer component is promoted, thereby improving the cooling performance of the cooling object.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2015-220363

[0010] However, in the cooling device of Patent Document 1, the flow rate and flow direction of the refrigerant liquid pumped from the circulation pump and the depth and width of each fin of the heat transfer member are determined so as to effectively squeeze out the bubbles in the groove.

[0011] Therefore, in the cooling device of Patent Document 1, if the operating conditions change, for example, the flow rate or flow direction of the refrigerant liquid pumped from the circulation pump changes, the bubbles in the groove may not be effectively squeezed out by the refrigerant liquid pumped from the circulation pump. That is, in the cooling device of Patent Document 1, if the operating conditions change, the heat transfer performance of the heat transfer component may be reduced, and the cooling performance of the cooling device may be reduced. Summary of the invention

[0012] In view of the above, an object of the present disclosure is to provide a heat transfer member that can exhibit high heat transfer performance regardless of the operating conditions of a cooling device to which it is applied.

[0013] Furthermore, another object of the present disclosure is to provide a method for manufacturing a heat transfer member that can exhibit high heat transfer performance regardless of the operating conditions of a cooling device to which it is applied.

[0014] To achieve the above object, a heat transfer component according to one embodiment of the present disclosure is applied to a cooling device that cools an object to be cooled while immersed in a liquid refrigerant, and is a heat transfer component that promotes heat transfer from the object to be cooled to the refrigerant.

[0015] The object to be cooled is an electronic device. The refrigerant is a fluorine-based insulating refrigerant having a boiling point of 100°C or less. The refrigerant is exposed to the atmosphere. The heat transfer component is as follows: on a boiling curve with the horizontal axis being the refrigerant superheat dT and the vertical axis being the heat flux q, when the superheat dT is 10K, the heat flux q is 300kW / m 2 .

[0016] Here, the degree of superheat dT is a value obtained by subtracting the saturation temperature Ts of the refrigerant from the temperature Tw of the heat transfer member. In addition, the heat flux q is the amount of heat per unit area transferred from the heat transfer part to the refrigerant.

[0017] Therefore, on the boiling curve, when the superheat dT is 10K, the heat flux q is 300kW / m 2 Therefore, regardless of the operating conditions of the cooling device to be applied, high heat transfer performance can be exerted. Furthermore, the cooling device to be applied can stably exert high cooling performance.

[0018] In addition, a heat transfer component of one embodiment of the present disclosure is applied to a cooling device for cooling a cooling object while it is immersed in a liquid refrigerant, and is a heat transfer component for promoting heat transfer from the cooling object to the refrigerant. Moreover, a boiling promoting surface for promoting boiling of the refrigerant is formed on the refrigerant side surface in contact with the refrigerant.

[0019] On the roughness curve of the boiling promotion surface, the portion formed between adjacent tops is defined as a hole portion. In addition, the distance between adjacent tops is defined as a hole portion width Gw. In addition, the distance between the line connecting the adjacent tops and the bottom between the adjacent tops is defined as a hole portion depth Gd. In addition, the value of the hole portion depth Gd divided by the hole portion width Gw is defined as the hole portion aspect ratio Gd / Gw. In addition, when the number of bottoms per unit length is defined as the hole portion number Ng, the number of holes in the hole portion whose hole portion aspect ratio Gd / Gw is greater than 0.01 is more than nine per 1mm.

[0020] Thus, on the refrigerant side, the number of holes having a hole aspect ratio Gd / Gw of 0.01 or more is nine or more per 1 mm, so that, as described in the embodiment to be described later, high heat transfer performance can be exerted regardless of the operating conditions of the cooling device to be applied. Furthermore, the cooling device to be applied can stably exert high cooling performance.

[0021] A method for manufacturing a heat transfer component according to one embodiment of the present disclosure is a method for manufacturing a heat transfer component that is applied to a cooling device that cools a cooling object while immersed in a liquid refrigerant and promotes heat transfer from the cooling object to the refrigerant.

[0022] Furthermore, there is a boiling promoting surface forming step in which a boiling promoting surface for promoting boiling of the refrigerant is formed by shot peening on at least a portion of the refrigerant side surface in contact with the refrigerant.

[0023] This makes it possible to form a boiling promotion surface on the heat transfer member. Therefore, it is possible to provide a method for manufacturing a heat transfer member that exhibits high heat transfer performance regardless of the operating conditions of a cooling device to which it is applied. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention is a schematic overall structural diagram of a cooling device according to an embodiment.

[0025] Figure 2 yes Figure 1 Section II-II is a schematic cross-sectional view of a cooling portion of one embodiment.

[0026] Figure 3 yes Figure 2 The III-III section is a schematic enlarged cross-sectional view of a heat transfer component according to one embodiment.

[0027] Figure 4 It is a perspective view of the appearance of a heat transfer component according to one embodiment.

[0028] Figure 5 is from Figure 4 An enlarged view observed in the V direction.

[0029] Figure 6 This is an explanatory diagram for explaining the hole portion of the boiling promotion surface according to one embodiment.

[0030] Figure 7 is a boiling curve of a heat transfer component of an embodiment.

[0031] Figure 8: is a graph showing the relationship between the hole aspect ratio and the cumulative value of the number of holes Ng according to one embodiment.

[0032] Fig. 9 This is a graph showing the relationship between the hole width and the hole aspect ratio according to one embodiment.

[0033] Fig.10 This is a perspective view of the appearance of a heat transfer component according to another embodiment. DETAILED DESCRIPTION

[0034] use Figures 1 to 9 , describing an embodiment of the present disclosure. In this embodiment, the heat transfer component 80 of the present disclosure is applied to the cooling part 30 of the cooling device 100. The cooling device 100 of this embodiment is a boiling cooling type cooling device that cools the heating element 70 as a cooling object while being immersed in the refrigerant liquid 40 as a liquid phase refrigerant.

[0035] like Figure 1 , Figure 2 As shown, the cooling device 100 includes a circulation pump 10, a heat dissipation unit 20, and a cooling unit 30. More specifically, the cooling device 100 is formed by arranging the circulation pump 10, the heat dissipation unit 20, and the cooling unit 30 in a circulation circuit 50 in which the refrigerant liquid 40 circulates. Figure 1 , Figure 2 The upper and lower arrows indicate the upper and lower directions in the vertical direction of the cooling unit 30 which is appropriately arranged.

[0036] First, the circulation pump 10 is a pressure-feeding unit that sucks and pressure-feeds the refrigerant liquid 40 flowing out of the circulation outlet 31 of the cooling unit 30. The circulation pump 10 is an electric liquid pump that operates by supplying electricity. As the circulation pump 10, a magnetic pump, a sealed pump, or the like in which at least a part of the motor as a driving unit is sealed relative to the refrigerant liquid 40 can be used.

[0037] In the present embodiment, a fluorine-based insulating refrigerant having a boiling point of 100°C or less is used as a refrigerant. The fluorine-based insulating refrigerant is a refrigerant having excellent insulation, heat transfer characteristics, and stability. More specifically, in the present embodiment, Novec (a trade name and registered trademark of 3M) having a hydrofluoroether (HFE) structure is used as a refrigerant. In addition, as a refrigerant, for example, Opteon (a trade name and registered trademark of Mitsui & Chemours), Galden (a trade name and registered trademark of Solvay), ASAHIKLIN (a trade name and registered trademark of AGC), SOLBLE (a trade name of SOLVEX), etc. can be used.

[0038] The discharge port of the circulation pump 10 is connected to the refrigerant inlet side of the heat dissipation unit 20. The heat dissipation unit 20 is a heat exchange unit for heat dissipation that allows the refrigerant liquid 40 to exchange heat with the atmosphere and dissipate the heat of the refrigerant liquid 40 to the atmosphere. The heat dissipation unit 20 suppresses the temperature rise of the refrigerant liquid 40 circulating in the circulation circuit 50 and maintains the low temperature state of the refrigerant liquid 40 by dissipating the heat of the refrigerant liquid 40 to the atmosphere.

[0039] The refrigerant outlet of the heat dissipation unit 20 is connected to the circulation inlet 32 ​​side of the cooling unit 30. The cooling unit 30 cools the heating element 70 as the cooling object. Figure 2 As shown in the cross-sectional view of FIG. 3 , the cooling unit 30 includes a cooling tank 33, a liquid reservoir 34, and a partition member 35. The cooling tank 33, the liquid reservoir 34, and the partition member 35 can be formed of a resin material or a metal material.

[0040] The cooling groove 33 is formed in a rectangular container shape with an open upper surface side. Inside the cooling groove 33, a storage space 331 for storing the lower side of the electronic substrate 60 is formed. The cooling groove 33 is formed with a circulation inlet 32 ​​for the refrigerant liquid 40 flowing out of the heat dissipation portion 20 to flow in and a circulation outlet 31 for the refrigerant liquid 40 to flow out to the suction port side of the circulation pump 10. Therefore, the refrigerant liquid 40 is stored in the storage space 331.

[0041] The electronic substrate 60 is an electrical substrate formed by a so-called hard printed substrate. A plurality of electronic devices including a heating element 70 are mounted on the electronic substrate 60. The portion of the electronic substrate 60 where the plurality of electronic devices including the heating element 70 are mounted becomes a portion immersed in the refrigerant liquid 40 when the electronic substrate 60 is accommodated in the accommodation space 331. Therefore, the heating element 70 is accommodated in the internal space of the cooling tank portion 33 while being immersed in the refrigerant liquid 40.

[0042] The heating element 70 is an electronic device called a large-scale integrated circuit, specifically a central processing unit of a computer. The heating element 70 generates heat when it is working. The performance of the heating element 70, such as the computing power, is easily reduced at high temperatures. Therefore, in the cooling device 100 of this embodiment, the heating element 70 is cooled in order to suppress the performance reduction.

[0043] The heating element 70 is formed in a rectangular flat plate shape. The heating element 70 is joined to the electronic substrate 60 by soldering. In addition, a heat transfer component 80 is mounted on the surface of the heating element 70 opposite to the surface joined to the electronic substrate 60. The heat transfer component 80 is a heat transfer part that promotes heat transfer from the heating element 70 to the refrigerant. The detailed structure of the heat transfer component 80 will be described later.

[0044] Here, the boiling point of the refrigerant liquid 40 of this embodiment is set to a value lower than the heating temperature reached when the heating element 70 generates heat. Therefore, in the cooling unit 30, the refrigerant liquid 40 is boiled by the heat generated by the heating element 70, and the boiling cooling of the heating element 70 is performed by the latent heat of vaporization when the refrigerant liquid 40 vaporizes.

[0045] Moreover, in the cooling section 30 of the present embodiment, so-called low-temperature boiling is performed, that is, while the refrigerant liquid 40 at a location away from the heating element 70 becomes a low-temperature liquid with a temperature lower than the boiling point, the refrigerant liquid 40 in contact with the heat transfer component 80 installed on the heating element 70 boils.

[0046] The bubbles of refrigerant gas generated by the boiling of the refrigerant liquid 40 in contact with the heat transfer component 80 are cooled and condensed in the low-temperature liquid. The bubbles that cannot be condensed in the low-temperature liquid are stored in the upper part of the storage space 331 to form a refrigerant gas layer 332. The refrigerant gas layer 332 contains not only the refrigerant in the gas phase, but also the dissolved gas (specifically, air) dissolved in the refrigerant liquid 40. Of course, when all the bubbles are condensed, the volume of the refrigerant gas layer 332 is zero.

[0047] Next, the liquid reservoir 34 is formed in a rectangular container shape with an open bottom surface. The liquid reservoir 34 is arranged on the upper side of the cooling groove 33. The upper opening of the cooling groove 33 and the lower opening of the liquid reservoir 34 are formed in shapes that fit each other.

[0048] The cooling groove 33 and the liquid storage tank 34 are integrated by bolting or the like in a state where their respective openings overlap. A sealing member such as a gasket (not shown) is sandwiched between the opening of the cooling groove 33 and the opening of the liquid storage tank 34. Therefore, the refrigerant in the cooling unit 30 will not leak to the outside from the gap between the opening of the cooling groove 33 and the opening of the liquid storage tank 34.

[0049] A storage space 341 for storing the refrigerant liquid 40 is formed inside the liquid storage tank 34. An opening 342 that penetrates the inside and outside of the liquid storage tank 34 is formed on the upper surface of the liquid storage tank 34. Therefore, the atmosphere can flow into the storage space 341 through the opening 342. That is, in the cooling unit 30, the refrigerant is open to the atmosphere.

[0050] The storage space 341 contains the upper portion of the electronic substrate 60. The connector 61 is disposed at the upper portion of the electronic substrate 60. The connector 61 is an electrical connection portion to which the power supply wiring 62 is connected. The power wiring 62 includes a power line that is a transmission path for power and a signal line that is a transmission path for electrical signals. The power wiring 62 connected to the connector 61 is taken out from the opening 342 to the outside of the cooling unit 30.

[0051] The partition member 35 partitions the storage space 331 of the cooling tank portion 33 and the storage space 341 of the liquid storage tank portion 34. The partition member 35 is formed in a substantially flat plate shape. The outer edge of the partition member 35 is formed in a shape suitable for the opening of the cooling tank portion 33. The partition member 35 is fixed to the opening of the cooling tank portion 33 by bolt fastening, press-fitting or bonding. The portion of the partition member 35 that expands in the horizontal direction becomes the bottom surface of the storage space 341.

[0052] In addition, a slit hole into which the electronic substrate 60 is inserted is formed in the central portion of the partition member 35. A support portion 351 is formed around the slit hole in a shape protruding toward the storage space 331. The electronic substrate 60 is clamped by the support portion 351 and supported in a manner that does not contact the inner wall surface of the cooling groove portion 33. The support portion 351 also has a function as a gas layer holding portion that holds the refrigerant gas layer 332 formed in the storage space 331.

[0053] Furthermore, a communication portion 352 is formed between the partition member 35 and the electronic substrate 60 . The communication portion 352 is a refrigerant passage that allows the housing space 331 of the cooling tank portion 33 and the storage space 341 of the liquid storage tank portion 34 to communicate with each other.

[0054] As described above, the opening 342 is formed in the liquid storage tank 34, so that the atmospheric pressure acts on the refrigerant in the storage space 341. Therefore, when the volume of the refrigerant in the cooling tank 33 changes due to boiling or condensation of the refrigerant in the storage space 331, the refrigerant liquid 40 moves between the storage space 331 and the storage space 341 via the connecting portion 352.

[0055] In this way, the refrigerant liquid 40 moves between the housing space 331 and the storage space 341 via the communication portion 352 , whereby the refrigerant liquid 40 for immersing the heating element 70 is always supplied to the cooling groove portion 33 .

[0056] Next, use Figure 3 to Figure 5 The heat transfer member 80 is described. The heat transfer member 80 is formed into a flat plate shape using a material having excellent heat transfer properties. The heat transfer member 80 of this embodiment is formed of a metal such as aluminum or copper. The outer surface of the heat transfer member 80 is roughly divided into a heat generating body side surface 81 and a refrigerant side surface 82 .

[0057] The heating element side surface 81 is a flat surface in contact with the heating element 70 on the outer peripheral surface of the heat transfer member 80. The heating element side surface 81 corresponds to the contact surface. The heating element side surface 81 is joined to a flat surface on the opposite side of the surface of the electronic substrate 60 to which the heating element 70 is joined by soldering or the like.

[0058] More specifically, the heating element 70 and the electronic substrate 60 of the present embodiment are joined by printing a paste solder on the joint surface of at least one of the heating element 70 and the electronic substrate 60, and then heating and melting the printed solder in a reflow furnace. Thus, the heating element 70 and the electronic substrate 60 can be joined over the entire joint surface.

[0059] The refrigerant side surface 82 is a surface that contacts the refrigerant liquid 40. Therefore, the refrigerant side surface 82 is a surface of the outer peripheral surface of the heat transfer component 80 other than the heating element side surface 81. That is, the refrigerant side surface 82 includes not only a surface of the outer peripheral surface of the heat transfer component 80 that is opposite to the heating element side surface 81, but also a surface that intersects with the heating element side surface 81.

[0060] The fin portion 83 is formed on the surface of the refrigerant side surface 82 that is opposite to the heating element side surface 81. The fin portion 83 is an area enlargement portion that enlarges the area of ​​the refrigerant side surface 82 and promotes heat transfer from the heating element 70 to the refrigerant. The fin portion 83 of this embodiment is formed on the refrigerant side surface 82 that is opposite to the heating element side surface 81 in the outer peripheral surface of the heat transfer component 80.

[0061] The fin portion 83 of this embodiment is formed by a plurality of grooves having a rectangular cross section provided on the refrigerant side surface 82 facing the heat generating body side surface 81. The plurality of grooves are formed to extend vertically in parallel with each other. Therefore, the fin portion 83 of this embodiment forms a so-called straight fin.

[0062] Therefore, the height dimension of each fin formed between adjacent grooves from the bottom surface of the groove is defined as fin height hf. In addition, the thickness dimension of each fin corresponding to the distance between adjacent grooves is defined as fin thickness tf. In addition, the value of fin height hf divided by fin thickness tf is defined as fin aspect ratio hf / tf. In addition, the distance between adjacent fins is defined as fin interval wf.

[0063] In the present embodiment, the fin aspect ratio hf / tf is defined as being greater than 1.3. Thus, the heat transfer component 80 of the present embodiment expands the area of ​​the refrigerant side surface 82 by 1.8 times or more compared to the heat transfer component without the fin portion 83. In addition, in the present embodiment, the fin interval wf is set to be greater than 0.2 mm. Thus, bubbles of the refrigerant gas boiling in the fin portion 83 are suppressed from being retained in the groove portion.

[0064] Furthermore, a boiling promoting surface 84 is formed on at least a portion of the refrigerant side surface 82 of the present embodiment. The boiling promoting surface 84 is a surface roughened on the refrigerant side surface 82 in order to promote boiling of the refrigerant liquid 40. More specifically, Figure 5As shown, the boiling promoting surface 84 is formed on the refrigerant side surface 82 forming the top surface of the fin portion 83, the side surface of adjacent fins facing each other, the bottom surface of the groove portion, and the side surface of the outer peripheral surface of the heat transfer component 80.

[0065] The area of ​​the boiling promoting surface 84 is larger than the area of ​​the heating element side surface 81, and is preferably formed to be 50% or more of the area of ​​the refrigerant side surface 82. Of course, the boiling promoting surface 84 can be formed on the entire area of ​​the refrigerant side surface 82. In addition, the boiling promoting surface 84 is preferably formed to be 50% or more of the fin portion 83.

[0066] Next, the detailed structure of the boiling promotion surface 84 is described. As described above, the boiling promotion surface 84 is a surface roughened on the refrigerant side surface 82. In the heat transfer component 80, a portion that becomes the boiling starting point when the refrigerant liquid 40 boils is formed by roughening the refrigerant side surface 82. Thus, boiling can be promoted.

[0067] Therefore, in the boiling promotion surface 84 of the present embodiment, the surface roughening treatment is applied so that the surface roughness Rz satisfies the following mathematical formula F1.

[0068] 1≤Rz≤150…(F1)

[0069] The surface roughness Rz in the present embodiment is an index called ten-point average roughness.

[0070] In more detail, the surface roughness Rz is obtained by extracting a reference length from the roughness curve along a specified direction, calculating the sum of the average value of the absolute value of the elevation from the highest mountain top to the fifth mountain top and the average value of the absolute value of the elevation from the lowest valley bottom to the fifth valley bottom in the extracted part, and expressing it in micrometers (μm).

[0071] The roughness curve is a curve obtained by removing wavelength components having a length greater than or equal to a predetermined length from a cross-sectional curve drawn by the flat surface on a cross section perpendicular to the flat surface. Figure 6 In FIG. 8 , the bold line of the present embodiment indicates the roughness curve Lrz in the boiling promotion surface 84 .

[0072] Furthermore, in this embodiment, if Figure 6 As shown, on the roughness curve of the boiling promotion surface 84, the recessed portion formed between adjacent tops 84a is defined as a hole portion 84c. In addition, the distance between adjacent tops 84a is defined as a hole portion width Gw. In addition, the distance between the line connecting adjacent tops 84a and the valley bottom 84b between adjacent tops 84a is defined as a hole portion depth Gd. In addition, the value of the hole portion depth Gd divided by the hole portion width Gw is defined as the hole portion aspect ratio Gd / Gw. In addition, the number of hole portions 84c per unit length (1mm in this embodiment) is defined as the hole portion number Ng.

[0073] Furthermore, in the boiling promotion surface 84 of the present embodiment, in order to effectively promote boiling, the surface roughening treatment is performed so that the number Ng of holes 84c satisfying the following mathematical formula F2 satisfies the following mathematical formula F3.

[0074] Gd / Gw≥0.01…(F2)

[0075] Ng≥9…(F3)

[0076] That is, in the boiling promotion surface 84 of the present embodiment, the surface is roughened by performing the surface roughening treatment so that the number of holes Ng of the holes 84c having the hole aspect ratio Gd / Gw of 0.01 or more is nine or more per 1 mm. In addition, the hole aspect ratio Gd / Gw may be 0.4 or less.

[0077] Furthermore, the hole width Gw may be determined so as to satisfy the following mathematical formula F4.

[0078] 315μm≥Gw≥1.7μm…(F4)

[0079] By performing the above-mentioned surface roughening treatment, such as Figure 7 As shown in FIG. 1 , on a boiling curve with the horizontal axis being the superheat dT of the refrigerant and the vertical axis being the heat flux q, the superheat dT of the heat transfer component 80 of this embodiment is 10K, and the heat flux q is 300 kW / m 2 The degree of superheat dT is a value obtained by subtracting the saturation temperature Ts of the refrigerant liquid 40 from the temperature Tw of the heat transfer component 80. The heat flux q is the amount of heat transferred from the heat transfer component 80 to the refrigerant liquid 40 per unit time.

[0080] In addition, Figure 7 , as a comparative example, a boiling curve of a heat transfer component in which the boiling promoting surface 84 is not formed, that is, a heat transfer component that has not been subjected to surface roughening treatment is also shown.

[0081] Next, the manufacturing method of the heat transfer member 80 of the present embodiment is described. First, in the raw material preparation step, the raw material of the heat transfer member 80 formed with the fin portion 83 is prepared. In the raw material preparation step, the raw material formed with the fin portion 83 by stamping or cutting a flat plate raw material such as aluminum or copper can be prepared.

[0082] In the boiling promotion surface forming process, the boiling promotion surface 84 is formed on the raw material prepared in the raw material preparation process. In the boiling promotion surface formation, the boiling promotion surface 84 is formed by shot peening. Shot peening is a processing method of roughening the surface by spraying fine aluminum oxide projection materials on the raw material and making them collide, thereby forming tiny holes on the surface of the raw material. In addition, as the material of the projection material, iron, stainless steel, zinc, ceramics, resin, etc. can be used.

[0083] In the boiling promotion surface forming process of the present embodiment, the projection material is sprayed onto the fin portion 83 from a direction perpendicular to the side surface 81 of the heating element. Thus, the surface of the refrigerant side surface 82 that forms the top of the fin portion 83 and the surface that forms the bottom of the groove portion become the boiling promotion surface 84. In addition, the projection material is sprayed onto the side surface 81 of the heating element from four horizontal directions. Thus, the side surface of the outer peripheral surface of the heat transfer component 80 becomes the boiling promotion surface 84. In addition, by spraying the projection material that is sufficiently smaller than the fin interval wf onto the fin portion 83 from various directions, the surface of all surfaces of the fin portion 83 can be roughened. Thus, all surfaces of the fin portion 83 become the boiling promotion surface 84.

[0084] Next, the operation of the cooling device 100 of this embodiment will be described. First, when the circulation pump 10 is operated, the circulation pump 10 sucks and pressure-feeds the refrigerant liquid 40 flowing out of the circulation outlet 31 of the cooling unit 30 . The refrigerant liquid 40 pressure-feeded from the circulation pump 10 flows into the heat dissipation unit 20 .

[0085] The refrigerant liquid 40 flowing in from the heat dissipation unit 20 exchanges heat with the atmosphere to be cooled. Thus, the low temperature state of the refrigerant liquid 40 is maintained in the cooling device 100. The refrigerant liquid 40 flowing out from the heat dissipation unit 20 flows into the storage space 331 of the cooling unit 30 through the circulation inlet 32 ​​of the cooling unit 30.

[0086] In the cooling unit 30, the heat generated by the heating element 70 is transferred to the refrigerant liquid 40 via the heat transfer member 80. As a result, the refrigerant liquid 40 near the heat transfer member 80 boils, and bubbles of refrigerant gas are generated. At this time, the heat generated by the heating element 70 is taken away as the latent heat of vaporization of the refrigerant liquid 40, and the heating element 70 is cooled.

[0087] The bubbles of the refrigerant gas rise inside the cooling groove 33 and are held below the partition member 35 to form a refrigerant gas layer 332. As described above, when all the bubbles are cooled and condensed by the low-temperature liquid, the refrigerant gas layer 332 is not formed.

[0088] As described above, in the cooling device 100 of this embodiment, the heat generating element 70 as the cooling object can be cooled by utilizing the vaporization latent heat of the refrigerant liquid 40. Furthermore, in the cooling device 100 of this embodiment, since the heat transfer member 80 is used, high cooling performance can be stably exerted even if the operating conditions change.

[0089] More specifically, in the cooling device 100 of this embodiment, if Figure 7 As explained above, the heat flux q is 300kW / m when the superheat dT on the boiling curve is 10K. 2 The heat transfer member 80 is provided. Thus, the heat transfer member 80 can exhibit high heat transfer performance regardless of the operating conditions of the cooling device 100. As a result, the cooling device 100 can stably exhibit high cooling performance.

[0090] In addition, the inventors have confirmed that by performing a surface roughening treatment, that is, by forming a boiling promotion surface 84, such as using Figure 7 As described above, the heat transfer member 80 can be formed to exhibit high heat transfer performance.

[0091] Specifically, the present inventors investigated the relationship between the upper limit value of the hole aspect ratio and the cumulative value of the number of holes Ng in six types of heat transfer members 80 that exhibit high heat transfer performance through surface roughening treatment. Figure 8 The integrated value of the number of holes Ng is a value obtained by integrating the number of holes Ng for holes 84 c having a hole aspect ratio Gd / Gw of 0.01 or more and not more than the upper limit of the hole aspect ratio Gd / Gw.

[0092] As a result, if Figure 8 As shown in FIG. 1 , if the heat transfer component 80 has a hole aspect ratio Gd / Gw of 0.01 or more and a hole number Ng of nine or more, it is confirmed that the heat transfer component 80 exhibits high heat transfer performance. Figure 8 As shown, if the upper limit value of the pore aspect ratio Gd / Gw is greater than 0.4, the cumulative value of the pore number Ng does not change, so the upper limit value of the pore aspect ratio Gd / Gw can be set to 0.4 or less.

[0093] In addition, the inventors investigated the distribution of hole widths Gw of six types of heat transfer components 80 that exhibit the above-mentioned high heat transfer performance by forming boiling promotion surfaces 84. Fig. 9 As shown, when the hole aspect ratio Gd / Gw is 0.01 or more, if the hole width Gw is 1.7 μm or more and 315 μm or less, the heat transfer member 80 exhibits high heat transfer performance. This can more reliably form the boiling promotion surface 84 that can improve the heat transfer performance.

[0094] In addition, the heat transfer member 80 of this embodiment has the fin portion 83 as the area enlargement portion, so that the heat transfer from the heating element 70 to the refrigerant can be promoted. Moreover, the boiling promotion surface 84 is formed as a surface parallel to the heating element side surface 81, so even if the fin portion 83 is provided, the boiling promotion surface 84 can be formed.

[0095] Furthermore, the method for manufacturing the heat transfer member 80 of the present embodiment includes a boiling promoting surface forming step of forming the boiling promoting surface 84 by shot peening.

[0096] Thus, it is possible to very easily form the boiling promoting surface 84. Furthermore, in the boiling promoting surface forming step, the projection material is sprayed from a direction perpendicular to the heating element side surface 81, so that the boiling promoting surface 84 can be easily formed not only on the surface of the top of the fin portion 83 formed on the refrigerant side surface 82, but also on the surface of the bottom of the groove portion formed.

[0097] The present disclosure is not limited to the above-described embodiments, and various modifications as described below are possible without departing from the gist of the present disclosure.

[0098] (1) In the above embodiment, the cooling device 100 is used to cool the heat generating element 70 of an electronic device, but the cooling object is not limited to the electronic device. The cooling device 100 including the heat transfer member 80 of this embodiment can be applied to a wide range of cooling objects that need to be cooled.

[0099] (2) The cooling device 100 is not limited to the structure disclosed in the above embodiment. For example, as long as the refrigerant liquid 40 in the portion of the storage space 331 away from the heating element 70 can be maintained at a low temperature, the circulation circuit 50, the circulation pump 10 and the heat dissipation unit 20 may be eliminated.

[0100] (3) The heat transfer member 80 is not limited to the structure disclosed in the above-mentioned embodiment.

[0101] For example, in the above-mentioned embodiment, an example of fixing the heat transfer component 80 to the heating element 70 by brazing is described, but the fixing method of the heat transfer component 80 is not limited to this. For example, the heat transfer component 80 may be fixed to the heating element 70 by a fastening method such as bolting, while a sheet-like or grease-like heat transfer material having electrical insulation and high thermal conductivity is sandwiched between the heat transfer component 80 and the heating element 70.

[0102] In addition, in the above-mentioned embodiment, an example is described in which the fin portion 83 is formed by a plurality of grooves extending in the vertical direction, but the present invention is not limited to this. Fig.10As shown, the fin portion 83 may be formed by a plurality of grooves extending in the vertical direction and a plurality of grooves extending in the horizontal direction. In other words, the fin portion 83 may be formed as a so-called pin fin.

[0103] In addition, in the above-mentioned embodiment, an example is described in which the fin portion 83 is formed by a plurality of groove portions having a rectangular cross section, but the present invention is not limited thereto. For example, the fin portion 83 may be formed by a plurality of groove portions having a triangular cross section or a trapezoidal cross section. Thus, the boiling promoting surface 84 is also easily formed on the side surface formed between adjacent fins.

[0104] (4) In the boiling promotion surface forming step of the above-mentioned embodiment, an example of using shot peening to form the boiling promotion surface 84 is described, but it is not limited to this. As long as the boiling promotion surface 84 similar to the above-mentioned embodiment can be formed, laser processing, mechanical processing using a grinder or a sander, etching, etc. may also be used.

[0105] (5) In the above embodiment, the cooling tank 33 and the liquid storage tank 34 are provided as separate bodies (ie, different components) in the cooling unit 30, but the present invention is not limited thereto. For example, the cooling tank 33 and the liquid storage tank 34 may be formed integrally.

[0106] Although the present disclosure is described according to the embodiment, it should be understood that the present disclosure is not limited to the embodiment, structure. The present disclosure also includes various modifications, deformations within the equivalent range. In addition, various combinations or modes, and other combinations or modes containing only one element, more than one element or less than one element also fall into the category or scope of thought of the present disclosure.

Claims

1. A heat transfer component, applied to a cooling device (100) for cooling a cooling object (70) while it is immersed in a liquid refrigerant, and promoting heat transfer from the cooling object to the refrigerant, It is characterized in that The cooling object is an electronic device, The refrigerant is a fluorine-based insulating refrigerant with a boiling point below 100°C. The refrigerant is open to the atmosphere, On the boiling curve with the horizontal axis being the superheat dT of the refrigerant and the vertical axis being the heat flux q, when the superheat is 10K, the heat flux q is 300kW / m 2 above.

2. A heat transfer component used in a cooling device (100) for cooling a cooling object (70) while it is immersed in a liquid refrigerant, and promoting heat transfer from the cooling object to the refrigerant, It is characterized in that A boiling promoting surface (84) for promoting boiling of the refrigerant is formed on a refrigerant side surface (82) in contact with the refrigerant. On the roughness curve of the boiling promotion surface, when a portion formed between adjacent tops is defined as a hole portion (84c), a distance between adjacent tops is defined as a hole portion width Gw, a distance between a line connecting adjacent tops and a bottom between adjacent tops is defined as a hole portion depth Gd, a value obtained by dividing the hole portion depth Gd by the hole portion width Gw is defined as a hole portion aspect ratio Gd / Gw, and the number of the holes per unit length is defined as a hole portion number Ng, The number Ng of holes of the hole portion having the hole aspect ratio Gd / Gw of 0.01 or more is nine or more per 1 mm.

3. The heat transfer component according to claim 2, It is characterized in that further, 315μm≥Gw≥1.7μm.

4. The heat transfer component according to claim 2 or 3, It is characterized in that have: a contact surface (81) in contact with the cooling object; and an area enlarging portion (83) for enlarging the area of ​​the refrigerant side surface, The boiling promotion surface is formed to occupy 50% or more of the area-enlarged portion.

5. A method for manufacturing a heat transfer component, the heat transfer component being applied to a cooling device (100) for cooling a cooling object (70) while being immersed in a liquid refrigerant, and promoting heat transfer from the cooling object to the refrigerant, It is characterized in that A boiling promoting surface forming step is provided, in which a boiling promoting surface (84) for promoting boiling of the refrigerant is formed by shot peening on at least a portion of a refrigerant side surface (82) in contact with the refrigerant.

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