Boiling Cooling Device

Abstract

To provide a boiling-cooling device with a simply structured heat propagation surface, the device presenting the same performance of heat propagation even in a narrow space for a heat reception unit.SOLUTION: The boiling-cooling device includes a liquid refrigerant, a first member 5 and a second member 6 facing each other, and a heat reception unit for storing a refrigerant in a storage room between the first member 5 and the second member 6 and receiving heat from a heat generator. The first member 5 includes a first base unit 51 and a first protruding unit 52 protruding from the first base unit 51 to the second member 6 and dividing the storage room. One or both of the inner wall surface of the first member 5 and the inner wall surface of the second member 6 is a heat propagation surface for boiling the refrigerant. The distance between the first protruding surface 52 and the second member 6 is less than or equal to twice the diameter of separated air bubbles generated by boiling refrigerant in a flat surface.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] This disclosure relates to a boiling cooling device. [Background technology]

[0002] A boiling cooling device is known that cools a heat-generating element by utilizing the heat transport due to the latent heat associated with the boiling of a refrigerant. An example of such a device is the boiling cooling device described in Patent Document 1.

[0003] The boiling cooling device described in Patent Document 1 comprises a heat receiving section that receives heat from the outside, a heat dissipation section that releases heat to the outside, and a flow section that connects the heat receiving section and the heat dissipation section. The heat receiving section is also provided with a heat transfer member having a boiling heat transfer surface that is immersed in the refrigerant. This boiling cooling device boils the refrigerant by transferring heat from a heating element to the refrigerant in the heat receiving section via the boiling heat transfer surface.

[0004] Furthermore, Patent Document 1 describes how the cooling efficiency of a heating element is improved by providing multiple holes with rough inner surfaces on the boiling heat transfer surface. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2017-15269 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, if the shape of the heat transfer surface is made more complex and fine in order to further improve heat transfer performance, there is a risk of blockage by foreign matter during long-term use. As a result, the heat transfer performance may decrease. In addition, it is difficult and costly to process heat transfer surfaces with complex and fine shapes.

[0007] In addition, when the internal space of the heat-receiving part becomes narrow due to the thinning of the boiling cooling device or the like, the internal space is likely to be filled with bubbles. Therefore, the bubbles are likely to coalesce with each other, and thus large bubbles are generated, and the heat transfer surface is covered with dry areas that do not contribute to heat transfer. Furthermore, in a narrow internal space, the pressure loss is large, so it is difficult to discharge large bubbles. As a result, the time during which the heat transfer surface is covered with dry areas becomes long, and the heat transfer characteristics deteriorate.

[0008] Therefore, a boiling cooling device having a heat transfer surface with a simple structure and not suffering from a reduction in heat transfer performance even in a narrow space inside the heat-receiving part is desired.

Means for Solving the Problems

[0009] In order to solve the above problems, a boiling cooling device according to a preferred aspect of the present disclosure has a liquid refrigerant, a first member and a second member facing each other, and the refrigerant is accommodated in an accommodation chamber between the first member and the second member, and includes a heat-receiving part that receives heat from a heating element. The first member has a first base portion and a first convex portion that protrudes from the first base portion toward the second member and divides the accommodation chamber. One or both of the inner wall surface of the first member and the inner wall surface of the second member is a heat transfer surface for boiling the refrigerant, and the distance between the first convex portion and the second member is not more than twice the departure bubble diameter of the bubbles generated by the boiling of the refrigerant in a plane.

Brief Description of the Drawings

[0010] [Figure 1] It is a perspective view showing a schematic configuration of a boiling cooling device according to a first embodiment. [Figure 2] It is a cross-sectional view of the boiling cooling device shown in FIG. 1. [Figure 3] It is a perspective view of the first member and the second member shown in FIG. 1. [Figure 4] It is a perspective view of the first member shown in FIG. 3. [Figure 5] It is a cross-sectional view of the first member and the second member shown in FIG. 3. [Figure 6] It is a diagram for explaining the growth of bubbles. [Figure 7] This is a diagram to explain the growth of bubbles. [Figure 8] This is a diagram to explain the growth of bubbles. [Figure 9] This is a diagram to explain the detachment of air bubbles. [Figure 10] This is a diagram to explain the detachment of air bubbles. [Figure 11] This is a diagram to explain the detachment of air bubbles. [Figure 12] This is a cross-sectional view showing the behavior of bubbles in the containment chamber. [Figure 13] This is a perspective view showing the behavior of bubbles in the containment chamber. [Figure 14] This figure shows the growth of bubbles on the heat transfer surface of the comparative example. [Figure 15] This figure shows the growth of bubbles on the heat transfer surface of the comparative example. [Figure 16] This figure shows the growth of bubbles on the heat transfer surface of the comparative example. [Figure 17] This figure shows the growth of bubbles on the heat transfer surface of the comparative example. [Figure 18] These are cross-sectional views of the first and second members of the second embodiment. [Figure 19] These are cross-sectional views of the first and second members of the first modified example. [Figure 20] These are cross-sectional views of the first and second members of the second modified example. [Figure 21] These are cross-sectional views of the first and second members of the third modified example. [Figure 22] These are cross-sectional views of the first and second members of the third embodiment. [Figure 23] This is a cross-sectional view showing the behavior of bubbles in the containment chamber. [Figure 24] This is a perspective view showing the first member of the fourth embodiment. [Figure 25] These are cross-sectional views of the first and second members of the fourth embodiment. [Figure 26] This is a diagram showing the first component of the fourth modified example. [Figure 27] This is a diagram showing the first component of the fifth modified example. [Figure 28] This figure shows an example of the arrangement of the first and second members. [Figure 29] This figure shows an example of the arrangement of the first and second members. [Modes for carrying out the invention]

[0011] Preferred embodiments of the present disclosure will be described below with reference to the attached drawings. Note that the dimensions and scale of parts in the drawings may differ from actual dimensions as appropriate, and some parts are shown schematically for ease of understanding. Furthermore, the scope of the present disclosure is not limited to these embodiments unless otherwise stated in the following description.

[0012] 1. First Embodiment 1-1. Overview of Boiling Cooling Equipment Figure 1 is a perspective view showing the schematic configuration of a boiling cooling device 1 according to the first embodiment. For convenience, the following description will use mutually orthogonal X, Y, and Z axes as appropriate. In the following, one direction along the X axis is the X1 direction, and the direction opposite to the X1 direction is the X2 direction. One direction along the Y axis is the Y1 direction, and the direction opposite to the Y1 direction is the Y2 direction. One direction along the Z axis is the Z1 direction, and the direction opposite to the Z1 direction is the Z2 direction. The XY plane is parallel to the horizontal plane. The Z axis is parallel to the vertical line, with the Z1 direction corresponding to vertically upward and the Z2 direction corresponding to vertically downward. The orientation of the Z axis in real space is determined according to the installation orientation of the boiling cooling device 1. Furthermore, "direction along the vertical line" includes not only directions that are perfectly parallel to the vertical line, but also directions that are slightly inclined with respect to the vertical line, to the extent that they do not depart from the invention described herein. Furthermore, in this specification, "equal" includes not only cases where they are exactly equal, but also cases within the range of manufacturing tolerances, etc.

[0013] The boiling cooling device 1 cools the two heating elements 100 shown by the dashed lines in Figure 1. Each heating element 100 is, for example, a power semiconductor element such as a diode or an IGBT (Insulated Gate Bipolar Transistor). Power semiconductor elements are used in power electronics products such as inverters or rectifiers mounted in railway vehicles, automobiles, or household electrical appliances. Note that the heating elements 100 are not limited to power semiconductor elements; other electrical or electronic components that generate heat through driving or energization may also be used, as long as cooling is required.

[0014] In the example shown in Figure 1, the two heating elements 100 are arranged side by side along the Y-axis, flanking the boiling cooling device 1. Each heating element 100 has a flattened shape along the XZ plane. Figure 1 shows the general shape of each heating element 100. The shapes of each heating element 100 shown in Figure 1 are examples, and any desired shape can be used. The number of heating elements 100 is not limited to two; there may be one or three or more. If there are three or more, for example, two or more may be arranged in the Y1 direction of the boiling cooling device.

[0015] Figure 2 is a cross-sectional view of the boiling cooling device 1 shown in Figure 1. The boiling cooling device 1 shown in Figure 2 is a loop-type thermosiphon cooler that utilizes the density difference between vaporized refrigerant RE and liquefied refrigerant RE. The boiling cooling device 1 has a heat receiving section 10, a heat dissipation section 20, a first pipe section 30, and a second pipe section 40.

[0016] 1-1a. Heat receiving part 10 The heat receiving unit 10 has a box-shaped container 11. The container 11 has a storage chamber S10 as its internal space for containing the refrigerant RE. The heat receiving unit 10 heats the refrigerant RE with heat from the heating element 100, vaporizing the refrigerant RE to produce a gaseous refrigerant.

[0017] In recent years, efforts have been made to make the boiling cooling device 1 thinner, for example, from the viewpoint of improving the arrangement efficiency of multiple heating elements 100 and the boiling cooling device 1. Due to the thinning of the boiling cooling device 1, the housing chamber S10 of the heat receiving section 10 has become narrower than before.

[0018] In the illustrated example, the container 11 has a bottom plate 111, a top plate 112, and side walls 113. The space enclosed by the bottom plate 111, the top plate 112, and the side walls 113 is the storage chamber S10. The side walls 113 also have a first member 5 and a second member 6.

[0019] The base plate 111 and the top plate 112 are both flat plates extending along the XY plane. The base plate 111 and the top plate 112 are arranged parallel to each other, with the top plate 112 positioned in the Z1 direction relative to the base plate 111. The top plate 112 is also provided with holes for connecting to the first pipe section 30 and the second pipe section 40. A side wall 113 is positioned between the base plate 111 and the top plate 112.

[0020] The side wall 113 connects the outer peripheries of the bottom plate 111 and the top plate 112 all around. The outer surface of the side wall 113 is in contact with the two heating elements 100. In the example shown in Figure 1, the side wall 113 is a rectangular tube and is composed of four flat plate-shaped members. Of these four flat plate-shaped members, the flat plate-shaped portion located in the Y1 direction is the first member 5. Of these four flat plate-shaped members, the flat plate-shaped portion located in the Y2 direction is the second member 6. Therefore, the first member 5 and the second member 6 face each other, and the housing chamber S10 is located between the first member 5 and the second member 6. The first member 5 receives heat from one of the two heating elements 100. The second member 6 receives heat from the other of the two heating elements 100. Note that other members or adhesives may be interposed between each heating element 100 and the container 11.

[0021] The inner wall surface of the first member 5 is a heat transfer surface 50. The inner wall surface of the second member 6 is a heat transfer surface 60. Each of the heat transfer surfaces 50 and 60 is in contact with the refrigerant RE. As the refrigerant RE near each of the heat transfer surfaces 50 and 60 is superheated to a temperature above its boiling point, multiple bubbles B are generated on each of the heat transfer surfaces 50 and 60.

[0022] Each of the first member 5 and the second member 6 is made of a material with excellent thermal conductivity. Specifically, the materials of the first member 5 and the second member 6 are, for example, metals such as aluminum and copper, or alloys containing such metals. The material of the part of the container 11 excluding the first member 5 and the second member 6 is not particularly limited, but is similar to the material of the first member 5 and the second member 6, for example, metals such as aluminum and copper, or alloys containing such metals.

[0023] In the example shown in Figure 1, the first member 5 and the second member 6 are parts of the container 11, but they may be separate from the container 11. Furthermore, each of the first member 5 and the second member 6 may be composed of a single component or multiple components. Also, the shape of the container 11 shown in Figure 1 is just an example, and it can be any desired shape. Similarly, the shape of the storage chamber S10 is a rectangular prism, but this is just an example, and it can be any desired shape.

[0024] 1-1b. Heat radiation part 20 The heat dissipation section 20 shown in Figure 2 is positioned in the Z1 direction relative to the heat receiving section 10. The heat dissipation section 20 has a container 21 and a plurality of heat dissipation fins 22. The container 21 has a condensation chamber S20 as its internal space, which condenses the refrigerant RE from a vaporized state into a liquid state. In the heat dissipation section 20, the gaseous refrigerant generated in the heat receiving section 10 is condensed to produce a liquid refrigerant.

[0025] In the illustrated example, the container 21 has a bottom plate 211, a top plate 212, and side walls 213. The space enclosed by the bottom plate 211, the top plate 212, and the side walls 213 is the condensation chamber S20.

[0026] The bottom plate 211 and the top plate 212 are both flat plates extending along the XY plane. The bottom plate 211 and the top plate 212 are arranged parallel to each other, with the bottom plate 211 positioned in the Z2 direction relative to the top plate 212. The bottom plate 211 is also provided with holes for connecting to the first pipe section 30 and the second pipe section 40. A side wall 213 is positioned between the bottom plate 211 and the top plate 212. The side wall 213 connects the outer circumferences of the bottom plate 211 and the top plate 212 around their entire circumference. Note that the shape of the container 21 shown in Figure 1 is an example, and it can be any desired shape as appropriate. Also, the side wall 213 is cylindrical, and the condensation chamber S20 is cylindrical, but these shapes are just examples, and they can be any desired shape as appropriate.

[0027] The container 21 is formed from a material with excellent thermal conductivity. Specific materials for the container 21 include, for example, metallic materials such as copper, aluminum, or alloys thereof.

[0028] Each heat dissipation fin 22 is thermally connected to the container 21. Each heat dissipation fin 22 is a flat plate-shaped member. Multiple heat dissipation fins 22 are spaced apart from each other in the thickness direction. Each heat dissipation fin 22 is made of a material with excellent thermal conductivity. The material of the heat dissipation fin 22 is, for example, a metallic material such as copper, aluminum, or an alloy of any of these. Each heat dissipation fin 22 is also provided with a hole for inserting the container 21. The heat dissipation fins 22 are fixed to the container 21 by, for example, expansion, press-fitting, adhesive, screw fastening, brazing, or welding. Note that other members or adhesives may be interposed between each heat dissipation fin 22 and the container 21.

[0029] Furthermore, the shape of the heat dissipation fins 22 is not limited to the example shown in Figure 1, and can be any desired shape as appropriate. Also, the heat dissipation fins 22 may be provided as needed, or omitted. However, by having multiple heat dissipation fins 22 in the heat dissipation section 20, the gaseous refrigerant can be efficiently condensed and liquefied.

[0030] 1-1c. 1st pipe section 30 The first pipe section 30 is a straight steam pipe connected to the heat receiving section 10 and the heat dissipation section 20, respectively. The first pipe section 30 has a first flow path S30 as its internal space. The first flow path S30 transports the gaseous refrigerant generated by the vaporization of the refrigerant RE in the heat receiving section 10 to the heat dissipation section 20. In the illustrated example, one end of the first pipe section 30 is not in contact with the refrigerant RE in the containment chamber S10, and the other end of the first pipe section 30 protrudes from the bottom plate 211 into the condensation chamber S20. The width of the first flow path S30 is constant, and the cross-sectional area of ​​the first flow path S30 is constant, but these do not have to be constant. Also, the cross-sectional shape of the first flow path S30 is circular, but this is just an example, and it can be any desired shape as appropriate.

[0031] The material of the first tube section 30 is, for example, a metallic material such as copper, aluminum, or an alloy of any of these. However, the material of the first tube section 30 is not limited to a metallic material; for example, it may be a ceramic material or a resin material. The first tube section 30 is fixed to the top plate 112 and the bottom plate 211 by brazing or the like.

[0032] 1-1d. Second pipe section 40 The second pipe section 40 is a straight liquid pipe connected to the heat receiving section 10 and the heat dissipation section 20, respectively. The second pipe section 40 has a second flow path S40 as its internal space. The second flow path S40 transports the liquid phase refrigerant, which is generated by the condensation of the gaseous phase refrigerant in the heat dissipation section 20, to the heat receiving section 10. One end of the second pipe section 40 is not exposed in the condensation chamber S20, and the other end of the second pipe section 40 is exposed in the containment chamber S10 and in contact with the refrigerant RE. The width of the second flow path S40 is constant, and the cross-sectional area of ​​the second flow path S40 is constant, but these do not have to be constant. The cross-sectional shape of the second flow path S40 is circular, but this is just an example, and it can be any desired shape as appropriate.

[0033] The material of the second tube section 40 is, for example, a metallic material such as copper, aluminum, or an alloy of any of these. However, the material of the second tube section 40 is not limited to a metallic material; for example, it may be a ceramic material or a resin material. The second tube section 40 is fixed to the top plate 112 and the bottom plate 211 by brazing or the like.

[0034] In this boiling cooling device 1, heat from the two heating elements 100 is transferred to the refrigerant RE in the container 11 via the first member 5 or the second member 6, causing the refrigerant RE to boil near the heat transfer surfaces 50 and 60. As a result, bubbles B are generated on the heat transfer surfaces 50 and 60. The generated bubbles B detach from the heat transfer surfaces 50 and 60 due to buoyancy and become gaseous refrigerant RE above the liquid surface of the refrigerant RE. This gaseous refrigerant RE is transported from the heat receiving section 10 to the heat dissipation section 20 via the first pipe section 30. The gaseous refrigerant RE transported to the heat dissipation section 20 is condensed there and returns to liquid refrigerant RE. This liquid refrigerant RE is transported from the heat dissipation section 20 to the heat receiving section 10 via the second pipe section 40.

[0035] In the boiling cooling device 1, the two heat-generating elements 100 can be cooled by the phase change of the refrigerant RE near the heat transfer surfaces 50 and 60. Furthermore, the repeated vaporization of the refrigerant RE in the heat receiving section 10 and liquefaction in the heat dissipation section 20 allows the heat-generating elements 100 to be cooled continuously and stably.

[0036] The boiling cooling device 1 is not limited to the configuration shown in Figure 1, and may be, for example, a thermosiphon in which the heat receiving section 10, heat dissipation section 20, first pipe section 30, and second pipe section 40 are integrated. Furthermore, the boiling cooling device 1 may be a pool boiling type or a forced convection boiling type that forcibly generates the flow of refrigerant RE. In the case of a forced convection boiling type, for example, a pump (not shown) is connected to the first pipe section 30.

[0037] 1-2. Refrigerant RE Refrigerant RE contains a solvent and a surfactant. The solvent is the main component of refrigerant RE and is typically a medium that is liquid at room temperature under a predetermined pressure. Specific examples of the solvent are not particularly limited, but include, for example, water, alcohols such as methanol or ethanol, ketones such as acetone, glycols such as ethylene glycol, fluorocarbons such as Fluorinert, chlorofluorocarbons such as HFC134a, and hydrocarbons such as butane. One of these can be used alone or two or more can be used in combination as a mixture.

[0038] Surfactants are used, for example, to suppress the aggregation of bubbles B. The surfactant may be a nonionic surfactant, or an ionic surfactant such as an anionic surfactant or a cationic surfactant. By using an anionic or cationic surfactant, the aggregation of bubbles B is suppressed, for example, by the repulsive force based on the Coulomb force of the surfactant. Alternatively, by using a nonionic surfactant, the aggregation of bubbles B is suppressed, for example, by the steric hindrance of the nonionic surfactant.

[0039] Specific examples of surfactants include fluorine-based surfactants, silicone-based surfactants, and hydrocarbon-based surfactants. When the solvent contained in the refrigerant RE is water, it is preferable to use a hydrocarbon-based surfactant that has excellent solubility in water.

[0040] By including a surfactant in the refrigerant RE, the surface tension γ of the refrigerant RE can be reduced. This reduces the pressure difference Δp and the degree of superheating ΔT inside and outside bubble B. As a result, bubble B grows more easily. Furthermore, the reduced surface tension of the refrigerant RE reduces the adhesion force of bubble B to the heat transfer surfaces 50 and 60. Therefore, less buoyancy is required for bubble B to detach from the heat transfer surfaces 50 and 60, thus reducing the diameter of bubble B when it detaches from the heat transfer surfaces 50 and 60.

[0041] Furthermore, as mentioned above, the presence of a surfactant in the refrigerant RE suppresses the aggregation of adjacent bubbles B. As a result, each bubble B generated on the heat transfer surfaces 50 and 60 is more likely to detach while maintaining a small diameter. This shortens the generation cycle of bubbles B, meaning that the number of bubbles B generated per unit time can be increased. Moreover, the suppression of aggregation of adjacent bubbles B prevents the area of ​​the heat transfer surfaces 50 and 60 in contact with each bubble B from increasing. This prevents the heat transfer surfaces 50 and 60 from being covered for extended periods by dry areas that do not contribute to heat transfer. Therefore, by including a surfactant, the heat transfer characteristics of the heat transfer surfaces 50 and 60 can be improved compared to the case without the surfactant. Consequently, the cooling performance of the boiling cooling device 1 can be improved.

[0042] The surfactant may be omitted. Furthermore, the refrigerant RE may contain substances other than the solvent and surfactant, such as additives. However, in this case, these substances must be included in the refrigerant RE at a concentration that does not adversely affect its function.

[0043] 1-3. First member 5 and second member 6 Figure 3 is a perspective view of the first member 5 and the second member 6 shown in Figure 1. Figure 4 is a perspective view of the first member 5 shown in Figure 3.

[0044] As shown in Figure 3, the first member 5 and the second member 6 face each other and are spaced apart from each other. Each first member 5 is positioned along the Z-axis. Similarly, each second member 6 is positioned along the Z-axis. The heat transfer surface 50 is the surface of the first member 5 facing the second member 6. The heat transfer surface 60 is the surface of the second member 6 facing the first member 5. Each of the heat transfer surfaces 50 and 60 is positioned along the Z-axis. Each of the heat transfer surfaces 50 and 60 has a series of elongated protrusions and indentations along the Z-axis.

[0045] As shown in Figures 3 and 4, the first member 5 has a first base 51 and a plurality of first protrusions 52. The first base 51 is a flat plate along the XY plane. Each first protrusion 52 projects from the first base 51 toward the second member 6 in the Y2 direction. Each first protrusion 52 is elongated and parallel to the surface of the first base 51. In particular, in the illustrated example, the longitudinal direction of each first protrusion 52 is parallel to the direction along the Z axis. The plurality of first protrusions 52 are spaced apart from each other and arranged at equal pitches. The plurality of first protrusions 52 are aligned in the X2 direction, which is a "predetermined direction" that intersects the longitudinal direction of each first protrusion 52.

[0046] Similarly, the second member 6 has a second base 61 and a plurality of second protrusions 62. The second base 61 is a flat plate along the XY plane. Each second protrusion 62 projects from the second base 61 toward the first member 5 in the Y1 direction. Each second protrusion 62 is elongated and parallel to the surface of the second base 61. In particular, in the illustrated example, the longitudinal direction of each second protrusion 62 is parallel to the direction along the Z axis. The plurality of second protrusions 62 are spaced apart from each other and arranged at equal pitches. The plurality of second protrusions 62 are aligned in the X2 direction, which is a "predetermined direction". Also, the plurality of first protrusions 52 and the plurality of second protrusions 62 face each other in a one-to-one ratio and are spaced apart from each other.

[0047] In the illustrated example, the number of first protrusions 52 is 4, but it may be between 1 and 3, or 5 or more. Similarly, the number of second protrusions 62 is 4, but it may be between 1 and 3, or 5 or more. However, in this embodiment, since the first protrusions 52 and the second protrusions 62 face each other in a one-to-one ratio, the number of first protrusions 52 and the number of second protrusions 62 are equal to each other.

[0048] Figure 5 is a cross-sectional view of the first member 5 and the second member 6 shown in Figure 3. As shown in Figure 5, the multiple first protrusions 52 and the multiple second protrusions 62 face each other and divide the storage chamber S10. Specifically, the multiple first protrusions 52 and the multiple second protrusions 62 divide the storage chamber S10 into multiple first spaces V1 and multiple second spaces V2.

[0049] Each first space V1 is located between one first protrusion 52 and one second protrusion 62. Each first space V1 is a long space along the Z axis. Multiple first spaces V1 are spaced apart from each other and arranged in the X2 direction. Also, each second space V2 is located between two first spaces V1. Each second space V2 is a long space along the Z axis. Multiple first spaces V1 and multiple second spaces V2 are arranged alternately in the X2 direction. Furthermore, the volume of each second space V2 is much smaller than the volume of each first space V1. Thus, multiple first members 5 and multiple second members 6 divide the accommodation chamber S10 into a very narrow first space V1 and a second space V2 that is wider than the first space V1.

[0050] Furthermore, the heat transfer surface 50 has a plurality of first top surfaces 501, a plurality of first side surfaces 502, and a plurality of connecting surfaces 503. The plurality of first top surfaces 501 and the plurality of first side surfaces 502 are surfaces belonging to a plurality of first protrusions 52. Specifically, each first protrusion 52 has one first top surface 501 and two first side surfaces 502. Each first top surface 501 faces the second member 6. Each first top surface 501 extends along the Z axis and is parallel to the ZX plane. The first top surface 501 also has two first edges 504 that extend in the longitudinal direction of the first protrusion 52. Furthermore, each first side surface 502 extends along the Z axis and is parallel to the YZ plane. Each first side surface 502 connects the first top surface 501 and the connecting surface 503. The multiple connecting surfaces 503 are surfaces belonging to the first base 51 and are located between two adjacent first protrusions 52.

[0051] Similarly, the heat transfer surface 60 has a plurality of second top surfaces 601, a plurality of second side surfaces 602, and a plurality of connecting surfaces 603. The plurality of second top surfaces 601 and the plurality of second side surfaces 602 are surfaces belonging to a plurality of second protrusions 62. Specifically, each second protrusion 62 has one second top surface 601 and two second side surfaces 602. Each second top surface 601 faces the first member 5. Each second top surface 601 extends along the Z axis and is parallel to the ZX plane. The second top surface 601 also has two second edges 604 that extend in the longitudinal direction of the second protrusion 62. Each second side surface 602 extends along the Z axis and is parallel to the YZ plane. Each second side surface 602 connects the second top surface 601 and the connecting surface 603. The multiple connecting surfaces 603 are surfaces belonging to the second base 61 and are located between two adjacent second protrusions 62.

[0052] The width W51 of the first protrusion 52 and the width W61 of the second protrusion 62 are equal to each other. Also, the distance W52 between two adjacent first protrusions 52 and the distance W62 between two adjacent second protrusions 62 are equal to each other. In the illustrated example, the width W51 is greater than the width W52, but the width W51 may be less than or equal to the width W52. Similarly, the width W61 is greater than the width W62, but the width W61 may be less than or equal to the width W62. Furthermore, the widths W51 and W61 may be different from each other. The distances W52 and W62 may be different from each other.

[0053] Furthermore, the pitch of the multiple first protrusions 52 and the pitch of the multiple second protrusions 62 are equal to each other. This pitch is the distance between the centers. Note that the multiple first protrusions 52 and the multiple second protrusions 62 do not need to be at equal pitch, as long as they face each other. Also, the height H51 of the first protrusions 52 and the height H61 of the second protrusions 62 are equal to each other. Note that the heights H51 and H61 are not equal to each other.

[0054] Furthermore, the distance L1 between the first protrusion 52 and the second protrusion 62 is much smaller than the distance L2 between the first base 51 and the second base 61. Also, the distance L1 is the detached bubble diameter D of the bubbles B generated by the boiling of the refrigerant RE on the plane. base It is less than twice that. Note that distance L1 can also be considered as the distance between the first protrusion 52 and the second member 6.

[0055] Departure bubble diameter D base is the diameter of the bubble B when it departs from the heat transfer surface 50 or 60. Departure bubble diameter D base is obtained, for example, by calculation using the Cole and Rohsenow equation for pure water in a reduced pressure field. The said equation is represented by the following equation (1). D base = 1.5×10 -4 √(σ / g(ρ L - ρ V ))×Ja 5 / 4 ···(1) Ja = ρ L c PL T sat / ρVh fg T sat is the saturation temperature, σ is the surface tension, ρ L is the liquid density, ρ V is the vapor density, c PL is the specific heat of the liquid, h fg is the latent heat of evaporation, and g is the acceleration of gravity.

[0056] For example, when obtaining the departure bubble diameter D of pure water at a pressure of 50 kPa base Saturation temperature T sat : 355 [K] Surface tension σ: 62.4 [mN / m] Liquid density ρ L : 971 [kg / m 3 Vapor density ρ V : 0.309 [kg / m 3 Specific heat of liquid c PL : 4.20 [kJ / kg·K] Latent heat of evaporation h fg : 2305 [kJ / kg] Acceleration of gravity g = 9.81 [m / s 2 and by calculating using equation (1), the departure bubble diameter D base is 5.24 [mm].[[]END]

[0057] ​​​​As mentioned above, the addition of a surfactant to the refrigerant RE reduces the surface tension of the refrigerant RE. Therefore, for example, if the surface tension σ is 26.5 [mN / m], the detached bubble diameter D base This is 3.41 [mm].

[0058] Also, detached bubble diameter D base This may be measured using, for example, an imaging device such as a camera. In this case, the detached bubble diameter D base This measurement is taken when no forced convection is occurring in the refrigerant RE.

[0059] 3-2. Behavior of bubbles Figures 6, 7, and 8 are diagrams illustrating the growth of bubble B. Bubble B is generated by the heat from the heating element 100, for example, at the first apex 501 and the second apex 601.

[0060] As shown in Figure 6, when a bubble B1 generated on the first apex 501 grows, a microliquid film F1 is formed between the bubble B1 and the first apex 501. Similarly, when a bubble B2 generated on the second apex 601 grows, a microliquid film F2 is formed between the bubble B2 and the second apex 601.

[0061] As shown in Figure 7, as bubble B1 grows further and its radius increases, a dry region S1 that does not contribute to heat transfer is formed between bubble B1 and the first apex 501. Similarly, as bubble B2 grows further and its radius increases, a dry region S2 that does not contribute to heat transfer is formed between bubble B2 and the second apex 601.

[0062] As shown in Figure 8, as bubbles B1 and B2 grow further, they merge to form a larger bubble B0. As mentioned above, the distance L1 is equal to the detached bubble diameter D. baseSince it is less than twice as large, the first space V1 is much narrower than the second space V2. For this reason, bubbles B1 and B2 are more likely to come into contact and merge in the first space V1 than in the second space V2. Bubble B0 is in contact with the first apex 501 and the second apex 601. A microliquid film F1 and a dry region S1 exist between bubble B0 and the first apex 501, and a microliquid film F2 and a dry region S2 exist between bubble B0 and the second apex 601.

[0063] Figures 9, 10, and 11 are diagrams illustrating the detachment of bubble B0. As shown in Figures 9 and 10, as bubble B0 grows, it attempts to evacuate from the first space V1 to the second space V2. During the process of bubble B0 evacuating from the first space V1 to the second space V2, the dry regions S1 and S2 disappear, leaving only the microliquid films F1 and F2. Therefore, the first apex 501 and the second apex 601 are not covered by the dry regions S1 and S2 for an extended period. Then, as shown in Figure 11, bubble B0 is discharged from the first space V1 to the second space V2.

[0064] As described above, the multiple first protrusions 52 and the multiple second protrusions 62 are arranged in a one-to-one opposing configuration. The distance L1 between each first protrusion 52 and the opposing second protrusion 62 is the detached bubble diameter D. baseis not more than twice that of. The first convex portion 52 and the second convex portion 62 divide the accommodation chamber S10 into a narrow first space V1 and a wide second space V2. Therefore, the narrow first space V1 and the wide second space V2 can be made adjacent to each other. The wide second space V2 has a smaller pressure loss than the narrow first space V1. Therefore, the bubbles B0 in the first space V1 are easily discharged into the adjacent second space V2. Therefore, even if the bubbles B1 and B2 coalesce to form a large bubble B0, the bubble B0 is immediately discharged into the second space V2. In other words, by intentionally coalescing the bubbles B1 and B2, the smooth discharge of the bubbles B existing in the first space V1 into the second space V2 is promoted. For this reason, the period during which the first top surface 501 and the second top surface 601 are covered with the dry regions S1 and S2 can be shortened. Therefore, even if the accommodation chamber S10 is a narrower space than before, it is possible to suppress a decrease in heat transfer performance or to improve heat transfer performance.

[0065] Thus, when the distance L1 is not more than twice the departure bubble diameter D base it is possible to promote the coalescence of the bubbles B1 and B2 and the smooth discharge of the bubble B0 into the second space V2. On the other hand, when the distance L1 exceeds twice the departure bubble diameter D base it is difficult for the bubbles B1 and B2 to coalesce with each other, and thus the first space V1 is likely to be filled with a large number of bubbles B1 and B2. As a result, the heat transfer performance deteriorates. The first convex portion 52 and the second convex portion 62 only need to be separated from each other. Therefore, the distance L2 satisfies the relationship of 0 < L1 < departure bubble diameter D base ×2.

[0066] In addition, the heat transfer surfaces 50 and 60 have a simple structure with long protrusions and depressions. In a complex and fine structure, there is a risk that the heat transfer performance will deteriorate due to blockage by foreign matter. On the other hand, since the heat transfer surfaces 50 and 60 have a simple structure with long protrusions and depressions, there is no risk of blockage by foreign matter. Also, because of the simple structure, an increase in cost can be suppressed. Therefore, with the heat transfer surfaces 50 and 60, it is possible to improve the heat transfer characteristics over a long period with a simple configuration.

[0067] Figure 12 is a cross-sectional view showing the behavior of bubble B in the containment chamber S10. Figure 13 is a perspective view showing the behavior of bubble B in the containment chamber S10. As shown in Figure 12, bubbles B5 are generated on multiple first top surfaces 501 and multiple second top surfaces 601, as well as on multiple connecting surfaces 503 and each of the multiple connecting surfaces 603. Also, as shown in Figure 13, bubbles B5 present in the first space V1 rise along the vertical line due to buoyancy. Therefore, bubbles B5 rise as indicated by arrow A1 and are discharged from between the first member 5 and the second member 6.

[0068] Furthermore, as mentioned above, the bubble B0 in the second space V2 is discharged from the first space V1 into the second space V2. Therefore, the bubble B0 moves from the second space V2 to the first space V1 as shown by arrow A2. Then, in the first space V1, the bubble B0 rises along the vertical line due to buoyancy. Therefore, the bubble B0 rises as shown by arrow A3 and is discharged from between the first member 5 and the second member 6.

[0069] As mentioned above, each first protrusion 52 is elongated, and similarly, each second protrusion 62 is elongated. Because each first protrusion 52 and each second protrusion 62 is elongated, it is easy to move bubbles B0 and B5 along the first protrusion 52 and each second protrusion 62 in the first space V1. Therefore, by aligning the longitudinal directions of the first protrusion 52 and each second protrusion 62 with the discharge direction of bubbles B, it is possible to make it easier to discharge bubbles B. In other words, by aligning the direction of the first protrusion 52 and each second protrusion 62 in a direction that intersects with the discharge direction of bubbles B, it is possible to make it easier to discharge bubbles B. Specifically, in this embodiment, when the first member 5 and the second member 6 are arranged along a vertical line, aligning the longitudinal directions of each first protrusion 52 and each second protrusion 62 along a vertical line makes it easier to discharge bubbles B0 and B5 vertically upward.

[0070] Furthermore, having multiple first protrusions 52 and multiple second protrusions 62 allows the containment chamber S10 to be divided into multiple spaces compared to the case where there is only one first protrusion 52 and one second protrusion 62. By dividing it into multiple spaces, the widths W51 and W61 shown in Figure 5 can be shortened, making it easier to discharge the bubbles B0 from the first space V1 to the second space V2. Thus, the heat transfer performance can be improved.

[0071] Furthermore, as mentioned above, the distance L1 is equal to the detached bubble diameter D. base By being less than twice the distance, the coalescence of bubbles B1 and B2, and the smooth discharge of bubble B0 into the second space V2 can be promoted. Therefore, the distance L1 is equal to the detached bubble diameter D. base It is acceptable if it is less than twice the size of the detached bubble diameter D. base It is more preferable that the detached bubble diameter D is 1.8 times or less. base It is even more preferable that the distance L1 is 1.5 times or less. A smaller distance L1 can further promote the merging of bubbles B1 and B2, and the smooth discharge of bubble B0 into the second space V2.

[0072] Furthermore, while the distance L2 is not particularly limited, it is preferably five times or more the distance L1, and preferably ten times or more. Increasing the distance L2 can suppress the filling of bubbles B0 in the second space V2.

[0073] Furthermore, the volume of the first space V1 is preferably 10 times or less, and more preferably 20 times or less, the volume of the second space V2. By making the volume of the first space V1 significantly smaller than that of the second space V2, the pressure loss in the second space V2 can be made significantly smaller compared to the pressure loss in the first space V1. Therefore, the smooth discharge of bubbles B0 into the second space V2 can be further promoted.

[0074] Furthermore, from the viewpoint of promoting the merging of bubbles B1 and B2, and the smooth discharge of bubble B0 into the second space V2, the widths W51 and W61 are not particularly limited, but the detached bubble diameter D baseIt is preferable that it be more than 2 times and less than 10 times. Also, from the viewpoint of suppressing the filling of bubbles B0 in the second space V2, the widths W52 and W62 are not particularly limited, but the detached bubble diameter D base It is preferable that it be between 5 and 10 times the amount.

[0075] Figures 14, 15, 16, and 17 show the growth of bubbles B on the heat transfer surfaces 50x and 60x of the comparative example container 11x. As shown in Figure 14, the heat transfer surfaces 50x and 60x have no irregularities. Therefore, the distance between the heat transfer surfaces 50x and 60x is constant. Consequently, the length of the containment chamber S10x along the Y axis of the comparative example container 11x is uniform. Furthermore, the containment chamber S10x is assumed to be a narrower space than conventional containers, from the viewpoint of improving placement efficiency, etc.

[0076] As shown in Figure 14, in the containment chamber S10x, multiple bubbles B1 are generated on the heat transfer surface 50x, and multiple bubbles B2 are generated on the heat transfer surface 60x. As bubbles B1 grow, a dry region S1 that does not contribute to heat transfer is formed between bubbles B1 and the heat transfer surface 50x, in addition to a microliquid film F1. Similarly, as bubbles B2 grow, a dry region S2 that does not contribute to heat transfer is formed between bubbles B2 and the heat transfer surface 60x, in addition to a microliquid film F2.

[0077] As shown in Figure 15, as bubbles B1 and B2 grow, they merge to form bubble B0. Subsequently, as other bubbles B1 and B2 grow, these other bubbles B1 and B2 come into contact with bubble B0 and merge. As a result, as shown in Figure 16, bubble B0 becomes even larger. Then, the microliquid films F1 and F2 are each lost through evaporation, and the dry regions S1 and S2 expand over time. Consequently, as shown in Figure 17, the heat transfer surface 50x is covered by a dry region S1 that does not contribute to heat transfer, and the heat transfer surface 60x is covered by a dry region S2 that does not contribute to heat transfer.

[0078] Furthermore, because the containment chamber S10x is narrower than conventional chambers, the pressure loss within the narrow containment chamber S10x is large. As a result, bubbles B0 are difficult to expel from the narrow containment chamber S10x, and thus the period during which bubbles B0 remain on the heat transfer surfaces 50x and 60x is prolonged. Consequently, the period during which the heat transfer surface 50x is covered by a dry region S1 that does not contribute to heat transfer, and the period during which the heat transfer surface 60x is covered by a dry region S2 that does not contribute to heat transfer, increases. Therefore, the heat transfer performance deteriorates. Thus, when the containment chamber S10x is narrower than conventional chambers, bubbles B are difficult to expel, and thus the heat transfer performance deteriorates.

[0079] In contrast, in this embodiment, as shown in Figure 5, the heat transfer surfaces 50 and 60 have irregularities. Therefore, although the containment chamber S10 is a narrow space similar to the containment chamber S10x, unlike the containment chamber S10x, it has a first space V1 and a second space V2 with different volumes. Therefore, if the containment chamber S10 is formed between the irregular heat transfer surfaces 50 and 60 of this embodiment, as described above, air bubbles B can be smoothly discharged from the containment chamber S10. Thus, even if the containment chamber S10 is narrower than conventional chambers, it is possible to suppress the decrease in heat transfer performance or improve the heat transfer performance.

[0080] The aforementioned first top surface 501, first side surface 502, and connecting surface 503 are flat surfaces, but are not limited to flat surfaces; they may also have irregularities or curved surfaces.

[0081] 2. Second Embodiment The following describes a second embodiment of this disclosure. For elements whose operation and function are the same as those of the first embodiment described above, the reference numerals used in the description of the above embodiment will be reused, and detailed descriptions of each will be omitted as appropriate.

[0082] Figure 18 is a cross-sectional view of the first member 5A and the second member 6A of the second embodiment. As shown in Figure 18, the first top surface 501A of the first protrusion 52A of the first member 5A has two first edges 504 and 504A. The first edges 504 and 504A extend along the Z axis. One of the two first edges 504 and 504A, the first edge 504A, is chamfered. Specifically, the first edge 504A is R-chamfered and rounded. Similarly, the second top surface 601A of the second protrusion 62A of the second member 6A has two second edges 604 and 604A. The second edges 604 and 604A extend along the Z axis. One of the two second edges 604 and 604A, the second edge 604A, is chamfered. Specifically, the second edge portion 604A is rounded with an R-chamfer.

[0083] Because the first edge 504A and the second edge 604A are both chamfered, there is a portion between the first protrusion 52A and the second protrusion 62A where the distance L1 increases in the direction toward the second space V2. As a result, it becomes easier to discharge the air bubbles B0 from the first space V1 into the second space V2 along the first edge 504A and the second edge 604A.

[0084] Furthermore, the first edge portion 504A is located in the X2 direction, which is a "predetermined direction" relative to the first edge portion 504, and the second edge portion 604A is located in the X2 direction, which is a "predetermined direction" relative to the second edge portion 604. Therefore, the first edge portion 504A and the second edge portion 604A are located in the same direction. As a result, it becomes easier to discharge the bubbles B0 into the second space V2, which is located in the X2 direction relative to the first space V1.

[0085] Furthermore, the first edges 504A of the multiple first top surfaces 502A are all located in the same direction. Similarly, the second edges 604A of the multiple second top surfaces 602A are all located in the same direction. As a result, the bubbles B0 in each first space V1 are easily discharged in the same direction. Therefore, collisions between bubbles B0 in one second space V2 can be reduced. Thus, the bubbles B0 can be smoothly discharged from the first space V1 through the second space V2 to the outside of the containment chamber S10.

[0086] 2A. Variant The second embodiment described above can be modified in various ways, for example, as described below. Furthermore, these modifications may be combined as appropriate.

[0087] 2A-1. First Variation Figure 19 is a cross-sectional view of the first member 5Aa and the second member 6Aa of the first modified example. As shown in Figure 19, the first top surface 501Aa of the first protrusion 52Aa of the first member 5Aa has two first edges 504 and 504Aa. One of the two first edges 504 and 504Aa, the first edge 504Aa, is chamfered. Specifically, the first edge 504Aa is C-chamfered and is inclined with respect to the portion of the first top surface 501Aa excluding the first edge 504Aa. Also, the first edge 504Aa is located in the X2 direction with respect to the first edge 504.

[0088] Similarly, the second top surface 601Aa of the second protrusion 62Aa of the second member 6Aa has two second edges 604 and 604Aa. One of the two second edges 604Aa is chamfered. Specifically, the second edge 604Aa is C-chamfered and inclined with respect to the portion of the second top surface 601Aa excluding the second edge 604Aa. Also, the second edge 604Aa is located in the X2 direction with respect to the second edge 604. Therefore, the first edge 504Aa and the second edge 604Aa are located in the same direction.

[0089] The provision of the first edge portion 504Aa and the second edge portion 604Aa allows for the same effects as those of the second embodiment described above.

[0090] 2A-2. Second Variation Figure 20 is a cross-sectional view of the first member 5Ab and the second member 6Ab of the second modified example. As shown in Figure 20, the first top surface 501Ab of the first protrusion 52Ab of the first member 5Ab has two first edges 504A. Each of the two first edges 504A is rounded with a R-chamfer. Similarly, the second top surface 601Ab of the second protrusion 62Ab of the second member 6Ab has two second edges 604A. Each of the two second edges 604A is rounded with a R-chamfer. In this second modified example, as in the second embodiment, it is easier to discharge the bubbles B0 in the first space V1 into the second space V2.

[0091] 2A-3. Third Variation Figure 21 is a cross-sectional view of the first member 5Ac and the second member 6Ac of the third modified example. As shown in Figure 21, the first top surface 501Ac of the first protrusion 52Ac of the first member 5Ac has two first edges 504Aa. Each of the two first edges 504Aa is chamfered and inclined with respect to the portion of the first top surface 501Ac excluding the first edges 504Aa. Similarly, the second top surface 601Ac of the second protrusion 62Ac of the second member 6Ac has two second edges 604Aa. Each of the two second edges 604Aa is chamfered and inclined with respect to the portion of the second top surface 601Ac excluding the second edge 564Aa. In this third modified example, as in the first modified example, it is easier to discharge the bubbles B0 in the first space V1 into the second space V2.

[0092] 3. Third Embodiment A third embodiment of this disclosure will now be described. For elements whose operation and function are the same as those of the first embodiment described above, the reference numerals used in the description of the above embodiment will be reused, and detailed descriptions of each will be omitted as appropriate.

[0093] 3-1. First member 5 and second member 6B Figure 22 is a cross-sectional view of the first member 5 and the second member 6B of the third embodiment. As shown in Figure 22, the second member 6B is flat. The second member 6B is positioned opposite the first member 5. The surface of the second member 6B facing the first member 5 is the heat transfer surface 60B that boils the refrigerant. The second member 6A is positioned along the Z-axis, similar to the first member 5.

[0094] Multiple first protrusions 52 of the first member 5 divide the storage chamber S10. Specifically, the multiple first protrusions 52 divide the storage chamber S10 into multiple first spaces V1B and multiple second spaces V2B. The first space V1B is the space between the first protrusions 52 and the second member 6A. The second space V2B is the space between the connecting surface 503 and the second member 6B. Each of the first space V1B and the second space V2B is a long space along the Z axis. The multiple first spaces V1B and the multiple second spaces V2B are arranged alternately along the X axis. Furthermore, the volume of each first space V1B is much smaller than the volume of each second space V2B. Therefore, the multiple first members 5 divide the storage chamber S10 into very narrow first spaces V1B and second spaces V2B that are wider than the first spaces V1B.

[0095] The distance L1 between the first protrusion 52 and the second member 6A is much smaller than the distance L2 between the first base 51 and the second member 6A. Also, the distance L1 is the diameter D of the detached bubbles B generated by the boiling of the refrigerant RE on a plane. base It is less than twice that amount.

[0096] 2-2. Behavior of bubble B Figure 23 is a cross-sectional view showing the behavior of bubble B in the containment chamber S10. As shown in Figure 23, the first space V1B is much narrower than the second space V2B. Therefore, as in the first embodiment, bubble B0 is formed in the first space V1B. A microliquid film F1 and a dry region S1 exist between bubble B0 and the first top surface 501, and a microliquid film F2 and a dry region S2 exist between bubble B0 and the heat transfer surface 60B. Also, as in the first embodiment, as bubble B0 grows, bubble B0 is discharged from the first space V1B to the second space V2B. Also, as in the first embodiment, bubbles B5 are generated at each connection surface 503 in the second space V2.

[0097] In this embodiment as well, similar to the first embodiment, bubbles B5 generated in the second space V2B rise along the vertical line due to buoyancy and are discharged from between the first member 5 and the second member 6B. On the other hand, bubbles B0 generated in the first space V1B are discharged into the second space V2B, which has a smaller pressure loss than the first space V1B. Therefore, bubbles B0 move from the first space V1B to the second space V2B, and then rise along the vertical line due to buoyancy in the second space V2B. They are then discharged from between the first member 5 and the second member 6B.

[0098] As described above, in this embodiment, the second member 6B is flat, while the first member 5 has a plurality of first protrusions 52. The distance L1 between the second member 6B and each first protrusion 52 is the diameter of the detached air bubble D. base The first space V1B is less than twice the size of the second space V2B, and is narrower than the second space V2B. The first protrusion 52 divides the containment chamber S10 into the narrow first space V1B and the wider second space V2B. As a result, the containment chamber S10 can have the narrow first space V1B and the wider second space V2B adjacent to each other. The wider second space V2B has less pressure loss than the narrow first space V1B. As a result, bubbles B0 are easily discharged from the first space V1B to the second space V2B. Thus, the first top surface 501 and the heat transfer surface 60B are prevented from being covered by dry regions S1 and S2 for a long period of time. Therefore, even with a containment chamber S10 that is narrower than conventional designs, it is possible to suppress the decrease in heat transfer performance or improve the heat transfer performance.

[0099] Furthermore, as mentioned above, the heat transfer surface 50 has a simple structure with elongated irregularities, and the heat transfer surface 60B has a simple structure with a flat surface. With complex and fine structures, there is a risk of reduced heat transfer performance due to blockage by foreign matter, but since the heat transfer surfaces 50 and 60B have a simple structure, there is no risk of blockage by foreign matter. In addition, because of their simple structure, cost increases can be suppressed. Therefore, with heat transfer surfaces 50 and 60B, it is possible to improve heat transfer characteristics over the long term with a simple configuration.

[0100] Furthermore, as mentioned above, each first protrusion 52 is elongated. The elongation of each first protrusion 52 makes it easier to move the bubble B along the first protrusion 52 in the first space V1B. Therefore, by aligning the longitudinal direction of each first protrusion 52 with the discharge direction of the bubble B, it is possible to make it easier to discharge the bubble B. Specifically, in this embodiment, the first member 5 and the second member 6B are arranged along a vertical line. In this case, by arranging each first protrusion 52 along a vertical line, it becomes easier to discharge the bubble B vertically upward.

[0101] Furthermore, having multiple first protrusions 52 allows the containment chamber S10 to be divided into multiple spaces compared to the case where there is only one first protrusion 52. Dividing it into multiple spaces makes it easier to discharge the bubbles B0 from the first space V1B to the second space V2B. Therefore, the heat transfer performance can be improved.

[0102] 3A. Variant The third embodiment described above can be modified in various ways, for example, as described below. Furthermore, these modifications may be combined as appropriate.

[0103] As described in the second embodiment and the first modification above, one of the two first edges 504 of the first protrusion 52 may be chamfered. Even in this case, it becomes easier to discharge the bubbles B0 in the first space V1 and to suppress the filling of bubbles B0 in the first space V1.

[0104] As described in the second and third modified examples above, both of the two first edges 504 may be chamfered. Even in this case, the bubbles B0 in the first space V1 are more easily discharged.

[0105] 4. Fourth Embodiment A fourth embodiment of this disclosure will now be described. For elements whose operation and function are the same as those of the first embodiment described above, the reference numerals used in the description of the above embodiment will be reused, and detailed descriptions of each will be omitted as appropriate.

[0106] Figure 24 is a perspective view showing the first member 5C of the fourth embodiment. Figure 25 is a cross-sectional view of the first member 5C and the second member 6C of the fourth embodiment. As shown in Figure 24 or 25, each of the first member 5C and the second member 6C has a plurality of scattered protrusions.

[0107] As shown in Figure 24 or Figure 25, the first member 5C has a first base 51C and a plurality of first protrusions 52C. The first base 51C is a flat plate along the XY plane. Each first protrusion 52C projects from the first base 51C in the Y2 direction. Each first protrusion 52C is a rectangular prism. The plurality of first protrusions 52 are spaced apart from each other. The plurality of first protrusions 52C are scattered. In the illustrated example, the plurality of first protrusions 52C are arranged in a matrix in plan view.

[0108] Similarly, the second member 6C has a second base 61C and a plurality of second protrusions 62C. Although not shown in detail, the second member 6C has the same configuration as the first member 5C. Therefore, the second base 61C is a flat plate along the XY plane. Each second protrusion 62C projects from the second base 61C toward the first member 5C in the Y1 direction. Each second protrusion 62C is a rectangular prism. The plurality of second protrusions 62 are spaced apart from each other. The plurality of second protrusions 62C are scattered. In the illustrated example, the plurality of second protrusions 62C are arranged in a matrix in plan view. Also, the first protrusion 52C and the second protrusions 62C are arranged opposite each other in a one-to-one ratio and spaced apart from each other.

[0109] The number of first protrusions 52C and second protrusions 62C is not particularly limited and can be arbitrary. However, in this embodiment, the number of first protrusions 52C and the number of second protrusions 62C are equal so that they face each other. In addition, although the multiple first protrusions 52C and the multiple second protrusions 62C are arranged in a matrix, they may be scattered or arranged randomly.

[0110] Multiple first members 5C and multiple second members 6C divide the housing chamber S10. Specifically, multiple first protrusions 52C and multiple second protrusions 62C divide the housing chamber S10 into multiple first spaces V1C and second spaces V2C.

[0111] Each first space V1C is located between pairs of one first protrusion 52 and one second protrusion 62. Multiple first spaces V1C are arranged in a matrix in plan view. Second space V2C is the space excluding the multiple first spaces V1C. Second space V2C is grid-like in plan view. Furthermore, the volume of each first space V1C is much smaller than the volume of the second space V2C. Thus, the multiple first members 5C and the multiple second members 6C divide the accommodation chamber S10 into multiple very narrow first spaces V1C and second spaces V2C which are wider than each first space V1C.

[0112] Furthermore, the heat transfer surface 50C has a plurality of first top surfaces 501C, a plurality of first side surfaces 502C, and a connecting surface 503C. The plurality of first top surfaces 501C and the plurality of first side surfaces 502C are surfaces belonging to a plurality of first protrusions 52C. Specifically, each first protrusion 52C has one first top surface 501C and one first side surface 502C. Each first top surface 501C faces the second member 6C. Each first top surface 501C is a rectangle in plan view. Also, each first side surface 502C connects the first top surface 501C and the connecting surface 503C. The connecting surface 503 is a surface belonging to the first base 51C, and is the portion of the first base 51C that does not have the plurality of first protrusions 52C.

[0113] Similarly, the heat transfer surface 60C has a plurality of second top surfaces 601C, a plurality of second side surfaces 602C, and a connecting surface 603C. The plurality of second top surfaces 601C and the plurality of second side surfaces 602C are surfaces belonging to a plurality of second protrusions 62C. Specifically, each second protrusion 62C has one second top surface 601C and one second side surface 602C. Each second top surface 601C faces the first member 5C. Each second top surface 601C is a rectangle in plan view. Also, each second side surface 602C connects the second top surface 601C and the connecting surface 603C. The connecting surface 603C is a surface belonging to the second base 61, and is the portion of the second base 61C that does not have the plurality of second protrusions 62C.

[0114] In this embodiment as well, similar to the first embodiment, the distance L1 between the first protrusion 52C and the second protrusion 62C is much smaller than the distance L2 between the first base 51C and the second base 61C. Furthermore, the distance L1 is the detached bubble diameter D of the bubbles B generated by the boiling of the refrigerant RE on a plane. base It is less than twice as large. Furthermore, the first protrusion 52C and the second protrusion 62C divide the containment chamber S10 into a narrow second space V2C and a wide first space V1C. As a result, the narrow second space V2C and the wide first space V1C can be adjacent to each other in the containment chamber S10. Therefore, bubbles B0 can be easily discharged from the first space V1C to the second space V2C. Consequently, the first top surface 501C and the second top surface 601C are prevented from being covered by dry areas for a long period of time. Therefore, even with a containment chamber S10 that is narrower than conventional designs, it is possible to suppress the decrease in heat transfer performance or improve the heat transfer performance.

[0115] Furthermore, the heat transfer surfaces 50C and 60C have a simple structure with multiple scattered protrusions. Complex and fine structures may suffer from reduced heat transfer performance due to blockage by foreign matter. In contrast, the heat transfer surfaces 50C and 60C have a simple structure with multiple scattered protrusions, eliminating the risk of blockage by foreign matter. Moreover, their simple structure helps to suppress cost increases. Therefore, with heat transfer surfaces 50C and 60C, improved heat transfer characteristics can be achieved over the long term with a simple configuration.

[0116] 4A. Variant The fourth embodiment described above can be modified in various ways, for example, as described below. Furthermore, these modifications may be combined as appropriate.

[0117] The connection between the first top surface 501C and the first side surface 502C may be chamfered. Similarly, the connection between the second top surface 601C and the second side surface 602C may be chamfered. If chamfered, it is preferable that the chamfered portion is located in the direction of bubble B0 discharge. When the first member 5B and the second member 6B are arranged along a vertical line, the bubble B0 is discharged vertically upward due to buoyancy. Therefore, in this case, it is preferable that the chamfered portion is located in the vertically upward portion of the first top surface 501C and the second top surface 601C. This makes it easier for the bubble B0 in the first space V1 to be discharged.

[0118] The shapes of the first protrusion 52C and the second protrusion 62C are not limited to a rectangular prism and can be arbitrary. Examples of the shape of the first protrusion 52C are shown in the fourth and fifth modified examples.

[0119] 4A-1. Fourth variation Figure 26 shows the first member 5Ca of the fourth modified example. As shown in Figure 26, each first protrusion 52Ca of the first member 5Ca may be cylindrical. In this case, the first top surface 501Ca is circular. Although not shown, the shape of the second protrusion 62C can also be similarly modified.

[0120] 4A-2. Fifth variation Figure 27 shows the first member 5Cb of the fifth modified example. As shown in Figure 26, the cross-sectional area of ​​each first protrusion 52Cb of the first member 5Cb decreases as it moves away from the first base 51C. Although not shown, the shape of the second protrusion 62C can also be similarly modified.

[0121] Furthermore, the shapes of the first protrusion 52C and the second protrusion 62C may be the same or different.

[0122] Furthermore, in the fourth embodiment, the second member 6B of the third embodiment may be used instead of the second member 6C. The same applies to the fourth and fifth modified examples.

[0123] Although the boiling cooling device of the present invention has been described above based on the illustrated embodiments, the present invention is not limited to these. Furthermore, the configuration of each part of the present invention can be replaced with any configuration that performs a similar function to the above-described embodiments, and any configuration can also be added.

[0124] Furthermore, in the embodiments and modifications described above, the "first member" and the "second member" were arranged along a vertical line, but they do not necessarily have to be arranged along a vertical line.

[0125] Figures 28 and 29 show examples of the arrangement of the first member 5 and the second member 6, respectively. For example, as shown in Figure 28, the first member 5 and the second member 6 of the first embodiment may be inclined at an angle θ with respect to both the horizontal plane and the vertical line. In this case, the longitudinal directions of the first protrusion 52 and the second protrusion 62 are arranged along the direction of the inclination, allowing for the smooth discharge of bubbles B. Therefore, bubbles B5 generated in the second space V2 are discharged from between the first member 5 and the second member 6, as shown by arrow A1. Bubbles B0 generated in the first space V1 move to the second space V2, as shown by arrow A2, and then are discharged from between the first member 5 and the second member 6, as shown by arrow A3.

[0126] Furthermore, as shown in Figure 29, for example, the first member 5 and the second member 6 of the first embodiment may be arranged along a horizontal plane. Even in this case, bubbles B5 generated in the second space V2 are discharged from between the first member 5 and the second member 6 as shown by arrow A1. Bubbles B0 generated in the first space V1 move to the second space V2 as shown by arrow A2, and then are discharged from between the first member 5 and the second member 6 as shown by arrow A3.

[0127] In the embodiments described above, each of the "first member" and the "second member" has a "heat transfer surface," but either one may have a "heat transfer surface" that receives heat from the heating element 100. Therefore, one of the "first member" and the "second member" may be in thermal contact with the heating element 100.

[0128] Furthermore, the present invention can be used in a wide range of devices that utilize heat transfer through boiling phenomena, in addition to cooling devices for power semiconductor elements. [Explanation of symbols]

[0129] 1...Boiling cooling device, 5...First component, 5A...First component, 6...Second component, 10...Heat receiving section, 11...Container, 20...Heat dissipation section, 21...Container, 22...Heat dissipation fin, 30...First pipe section, 40...Second pipe section, 50...Heat transfer surface, 51...First base section, 52...First protrusion section, 60...Heat transfer surface, 60x...Heat transfer surface, 61...Second base section, 62...Second protrusion section, 100...Heating element, 111...Bottom plate, 112...Top plate, 113...Side wall, 211...Bottom plate, 212...Top plate, 213...Side wall, 501...First top surface, 502...First side surface, 503...Connecting surface, 504...First edge section ,601...Second top surface, 602...Second side surface, 603...Connecting surface, 604...Second edge, A1...Arrow, A2...Arrow, A3...Arrow, B0...Bubble, B1...Bubble, B2...Bubble, B5...Bubble, F1...Microliquid film, F2...Microliquid film, H51...Height, H61...Height, L1...Distance, L2...Distance, RE...Refrigerant, S1...Region, S2...Region, S10...Containment chamber, S10x...Narrow containment chamber, S20...Condensation chamber, S30...First flow path, S40...Second flow path, V1...First space, V2...Second space, W52...Distance, W62...Distance, θ...Angle.

Claims

1. Liquid refrigerant and It comprises a first member and a second member facing each other, a refrigerant contained in a chamber between the first member and the second member, and a heat receiving section that receives heat from a heating element, The first member has a first base and a first protrusion that extends from the first base toward the second member and divides the housing chamber. The inner wall surface of the first member and the inner wall surface of the second member, or both, are heat transfer surfaces that cause the refrigerant to boil. The distance between the first protrusion and the second member is less than or equal to twice the diameter of the detached bubbles generated by the boiling of the refrigerant on a flat surface. A boiling cooling device characterized by the following features.

2. The first base is flat, The first protrusion is elongated and parallel to the surface of the first base. The boiling cooling device according to claim 1.

3. The first protrusion has an elongated first top surface facing the second member, The first top surface has two first edges extending in the longitudinal direction of the first protrusion, One of the two first edges is chamfered. The boiling cooling apparatus according to claim 1 or 2.

4. The heat receiving portion has a plurality of first protrusions, including the first protrusion, Each of the plurality of first protrusions is elongated and parallel to the surface of the first base, The plurality of first protrusions are arranged in a direction intersecting the longitudinal direction of the first protrusions, The boiling cooling device according to claim 1.

5. The second member has a second base and a second protrusion that protrudes from the second base toward the first member and, together with the first protrusion, divides the housing chamber. The first protrusion and the second protrusion are opposite to each other, The boiling cooling device according to claim 1.

6. The heat receiving portion has a plurality of first protrusions including the first protrusion, and a plurality of second protrusions including the second protrusion, The first base is flat, The second base portion is flat, Each of the plurality of first protrusions is elongated and parallel to the surface of the first base, Each of the plurality of second protrusions is elongated and parallel to the surface of the second base, The plurality of first protrusions are arranged in a predetermined direction intersecting the longitudinal direction of the plurality of first protrusions, The plurality of second protrusions are arranged in the predetermined direction, The boiling cooling apparatus according to claim 5.

7. The first protrusion has an elongated first top surface facing the second member, The first top surface has two first edges extending in the longitudinal direction of the first protrusion, One of the two first edges located in the predetermined direction is chamfered. The second protrusion has an elongated second top surface facing the first member, The second top surface has two second edges extending in the longitudinal direction of the first protrusion, One of the two second edges located in the predetermined direction is chamfered. The boiling cooling device according to claim 6.

8. The heat receiving portion has a plurality of first protrusions, including the first protrusion, The aforementioned multiple first protrusions are scattered, The boiling cooling device according to claim 1.

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