JP2010040958A - Cooling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cooling device which obtains boil promotion effect even under a vacuum boiling condition with enormously enlarged bubbles of a boiled coolant, and improves bubble exhausting property from a heat transfer surface and a liquid-phase coolant. <P>SOLUTION: A region corresponding to a heating element fixing surface 320 on an inner surface 33 of a bottom wall 31 of a coolant tub 3 is set to be a boiling heat transfer surface 34 for promoting the boiling of the liquid-phase coolant. A fin 35 for standing up from the boiling heat transfer surface 34, having a top surface 350, and increasing a heat transfer area of the boiling heat transfer surface 34 is placed on the boiling heat transfer surface 34. A groove 36 for promoting boil of the liquid-phase coolant at the top surface 350 is formed on the top surface 350 having the highest height from the boiling heat transfer surface 34 on the fin 35. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a cooling device that cools a heating element such as a semiconductor element by latent heat transfer caused by vaporization and liquefaction of a refrigerant.

  In general, in order to improve the cooling performance of this type of cooling device, it is necessary to generate boiling even when the amount of heat generated from the heating element is small. For this purpose, it is important to supply foaming nuclei that become buds at the start of boiling on the heat transfer surface.

  In order to supply foam nuclei on the heat transfer surface, for example, Patent Document 1 discloses a method in which a porous layer is formed on the heat transfer surface and a groove is formed by crushing a part of the porous layer with a roller. It is shown. According to this, in the groove formed by crushing the porous material, a small opening part with a small porosity is generated, and in the region around the groove, a large opening part larger than the small opening part is generated. The large opening is a bubble growth opening, and the small opening is a liquid supply opening for supplying a liquid phase refrigerant into the porous body. As a result of the regular arrangement of the bubble growth aperture and the liquid supply aperture on the heat transfer surface at a certain ratio, the bubble growth and liquid supply are stabilized and the performance of the boiling heat transfer surface is improved. It becomes possible.

Moreover, in patent document 2, it is for boiling which has the hollow part provided under the outer peripheral surface of the heat exchanger tube, the some opening part which connects a cavity part and an outer peripheral part, and the fin provided by protruding outside from the heat exchanger tube A heat transfer tube is shown. According to this, some of the bubbles generated by boiling can be left in the cavity. In addition, an amount of liquid-phase refrigerant corresponding to the vapor separated from the cavity flows into the cavity, but since this liquid-phase refrigerant is heated by the heat released from the fins, the residual bubbles in the cavity are used as nuclei. It becomes possible to produce boiling with a small amount of heat.
Japanese Examined Patent Publication No. 2-53717 JP-A-6-323778

  By the way, depending on the type of refrigerant used in the cooling device and the heat resistance temperature of the element, the inside of the cooling device may be in a reduced pressure state to lower the boiling point of the refrigerant. In this case, when compared with the same amount of heating, starting boiling at a reduced pressure requires a greater degree of superheat, that is, the wall temperature of the heat transfer surface and the temperature difference between the refrigerants than under atmospheric pressure. It becomes. As a result, the initial bubble size and bubble growth rate at the start of boiling become larger than those under atmospheric pressure. For this reason, in the liquid phase refrigerant, the bubbles become enormous, and the detached bubble diameter from which the bubbles are detached from the heat transfer surface becomes larger than under atmospheric pressure.

  In the method described in Patent Document 1, when the inside of the cooling device is in a reduced pressure state, the porous material is reduced in thickness in order to improve the ability to discharge enormous bubbles from the inside of the porous material. It is necessary to increase the pore diameter. However, since a porous material having a good pore discharge property and a large pore diameter is difficult to hold bubbles serving as foam nuclei therein, the effect of promoting boiling is reduced.

  Further, since the amount of bubbles generated increases as the amount of heat of the heating element increases, it becomes difficult to discharge the bubbles from the porous material and to supply the liquid refrigerant into the porous material as the amount of heat increases. . As a result, the entire porous material is buried in the vapor film, and the performance of the boiling heat transfer surface is lowered. That is, on the heat transfer surface joined with the porous material, it becomes difficult to achieve both the promotion of boiling and the improvement of the discharge of enormous bubbles.

  Also, in the heat transfer tube for boiling described in Patent Document 2, when the amount of heat of the heating element is increased when the inside of the heat transfer tube is in a reduced pressure state, the entire cavity for promoting boiling is buried in the bubbles. Thus, the boiling promotion effect disappears.

  In view of the above points, the present invention is to improve the bubble heat transfer surface and the discharge property from the liquid refrigerant while obtaining the boiling promotion effect even under the reduced-pressure boiling condition where the bubbles of the boiling refrigerant become enormous. It is an object of the present invention to provide a cooling device that can perform the above.

  In order to achieve the above object, in the first aspect of the present invention, the portion corresponding to the heating element fixing surface (320) in the inner surface (33) of the bottom wall (31) of the refrigerant tank (3) is a liquid phase refrigerant. It is a boiling heat transfer surface (34) that promotes boiling, and the boiling heat transfer surface (34) rises from the boiling heat transfer surface (34) and has a top surface (350). Fins (35) that increase the heat transfer area of the surface (34) are provided, and the top surface (350) of the fin (35) is a boiling point that promotes boiling of the liquid-phase refrigerant at the top surface (350). The promotion means (36, 37) is provided.

  Thus, by providing the fin (35) that increases the heat transfer area of the boiling heat transfer surface (34), boiling of the refrigerant can be promoted. Furthermore, by providing boiling promotion means (36, 37) on the top surface (350) of the fin (35), the refrigerant can be boiled also on the top surface (350) of the fin (35). ) In which boiling occurs. Thereby, since the amount of steam generated per unit area in the fin (35) can be reduced, it is possible to improve the exhaustability of the boiled refrigerant bubbles. Therefore, even under reduced-pressure boiling conditions in which the bubbles of the boiled refrigerant become enormous, it is possible to improve the bubbling acceleration effect and improve the discharge characteristics of the bubbles from the heat transfer surface and the liquid phase refrigerant.

  Moreover, in invention of Claim 2, the corner | angular part (351) formed by the side surface (352) of a fin (35) and a boiling heat-transfer surface (34), and a boiling promotion means (36, 37) are The height from the heating element fixing surface (320) is different.

  Thus, by changing the height of the corner portion (351) and the boiling promotion means (36, 37) from the heating element fixing surface (320), the refrigerant bubbles discharged from the corner portion (351) and boiling Interference with the bubbles of the refrigerant discharged from the promotion means (36, 37) can be prevented. Thereby, it becomes possible to improve the discharge | emission property of a bubble more.

  In the invention according to claim 3, the top surface (350) is provided with a projection (37) protruding in a direction away from the boiling heat transfer surface (34), and the top of the projection (37). The cross-sectional area on the side close to the surface (350) is smaller than the cross-sectional area of the surface (370) having the highest height from the boiling heat transfer surface (34) in the protrusion (37), and the top surface (350). Constitutes boiling promotion means.

  Thus, by providing the fin (35) that increases the heat transfer area of the boiling heat transfer surface (34), boiling of the refrigerant can be promoted. Moreover, since the protrusion part (37) which protrudes in the direction away from the boiling heat-transfer surface (34) can be provided in the top surface (350) of the fin (35), the area | region where a boil can be expanded can be expanded. The amount of steam generated per unit area in (35) can be reduced. Thereby, the discharge property of bubbles can be improved. Therefore, even under reduced-pressure boiling conditions in which the bubbles of the boiled refrigerant become enormous, it is possible to improve the bubbling acceleration effect and improve the discharge characteristics of the bubbles from the heat transfer surface and the liquid phase refrigerant.

  In the invention according to claim 4, the top surface (350) is provided with a groove (36), and the groove (36) includes a first groove portion (361) and a second groove portion (362) communicating with each other. The first groove (361) is disposed on the side farther from the boiling heat transfer surface (34) than the second groove (362), and forms an opening on the top surface (350) side. The groove width of the first groove portion (361) is smaller than the groove width of the second groove portion (362), and the groove (36) constitutes a boiling promoting means.

  Thus, by providing the fin (35) that increases the heat transfer area of the boiling heat transfer surface (34), boiling of the refrigerant can be promoted. Further, by providing the groove (36) on the top surface (350) of the fin (35), the region where boiling occurs can be expanded, so that the amount of steam generated per unit area in the fin (35) is reduced. Can do. Thereby, the discharge property of bubbles can be improved. Therefore, even under reduced-pressure boiling conditions in which the bubbles of the boiled refrigerant become enormous, it is possible to improve the bubbling acceleration effect and improve the discharge characteristics of the bubbles from the heat transfer surface and the liquid phase refrigerant.

  Further, by making the groove width of the first groove portion (361) smaller than the groove width of the second groove portion (362), bubbles serving as foaming nuclei can be held inside the second groove portion (362). It becomes possible to further promote the boiling of water.

  The “groove width of the first groove portion (361)” in the present invention is the average groove width of the first groove portion (361) when the groove width of the first groove portion (361) is not constant in the height direction. Means. Similarly, the “groove width of the second groove portion (362)” in the present invention refers to the average groove of the second groove portion (362) when the groove width of the second groove portion (362) is not constant in the height direction. It means width.

  Further, the invention according to claim 5 is characterized in that the fin (35) is formed by laminating a plurality of thin plates (38) in the thickness direction of the thin plate (38). According to this, it becomes possible to manufacture a fin (35) easily.

  In the invention according to claim 6, the top surface (350) is formed with a groove (36) having a substantially rectangular cross section, and has a plate shape having an opening (71) penetrating in the plate thickness direction. The member (70) is disposed so that the groove (36) and the opening (71) communicate with each other, and the opening width of the opening (71) is smaller than the groove width of the groove (36). The groove (36) constitutes boiling promoting means.

  Thus, by providing the fin (35) that increases the heat transfer area of the boiling heat transfer surface (34), boiling of the refrigerant can be promoted. Further, by providing the groove (36) on the top surface (350) of the fin (35), the region where boiling occurs can be expanded, so that the amount of steam generated per unit area in the fin (35) is reduced. Can do. Thereby, the discharge property of bubbles can be improved. Therefore, even under reduced-pressure boiling conditions in which the bubbles of the boiled refrigerant become enormous, it is possible to improve the bubbling acceleration effect and improve the discharge characteristics of the bubbles from the heat transfer surface and the liquid phase refrigerant.

  In addition, by making the opening width of the opening (71) smaller than the groove width of the groove (36), it is possible to hold bubbles as foaming nuclei inside the groove (36), thereby further promoting the boiling of the refrigerant. It becomes possible to do. The “opening width of the opening (71)” in the present invention means a dimension in a direction parallel to the groove width direction of the groove (36) in the opening (71).

  In the invention according to claim 7, on the side far from the boiling heat transfer surface (34) of the fin (35), the steam discharge promoting means (80) for promoting the discharge of the refrigerant vapor boiled by the fin 35 (35). ), And the vapor discharge promoting means (80) includes an outer frame portion (81) that forms a vapor passage (800) through which the refrigerant vapor passes, and a plurality of narrow passages (801, 802) and the outer frame portion (81) and the partition member (82) are narrow passages (801, 802) toward the side away from the boiling heat transfer surface (34). The passage cross-sectional area is formed to be large.

  According to this, even when the central part of the heating element (2) becomes hotter than the other part and the amount of bubbles generated from the part corresponding to the central part of the heating element (2) in the fin (35) increases, Bubbles discharged from the fin (35) can be smoothly flowed. For this reason, while improving the discharge | emission property of the bubble from a liquid phase refrigerant | coolant, it becomes possible to prevent that a liquid phase refrigerant | coolant flows in into a thermal radiation part (4).

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings.

(First embodiment)
1st Embodiment of this invention is described based on FIGS. FIG. 1 is a perspective view showing a cooling device 1 according to the first embodiment, and FIG. 2 is a cross-sectional view showing the cooling device 1 according to the first embodiment. 1 and 2 is the vertical direction of the cooling device 1.

  As shown in FIG. 1 and FIG. 2, the cooling device 1 cools a heating element 2 such as a semiconductor element, in which liquid-phase refrigerant is stored, and the heating element 2 is installed outside. The refrigerant tank 3 is connected to the inside of the refrigerant tank 3, and is attached to the upper part of the refrigerant tank 3, and includes a heat radiating unit 4 that liquefies the refrigerant vaporized by the heat of the heating element 2 and returns the refrigerant tank 3 to the refrigerant tank 3. Yes.

  A part of the outer surface 32 of the bottom wall 31 in the refrigerant tank 3 is a heating element fixing surface 320 to which the heating element 2 is fixed. And the heat generating body 2 is being fixed to the heat generating body fixing surface 320 of the bottom wall 31 by clamping | tightening the bolt etc. which are not shown in figure, for example. Further, a boiling heat transfer surface 34 for promoting boiling of the refrigerant is provided in a region corresponding to the heating element fixing surface 320 in the inner surface 33 of the bottom wall 31. In the present embodiment, the boiling heat transfer surface 34 is formed integrally with the inner surface 33 of the bottom wall 31. The details of the boiling heat transfer surface 34 will be described later.

  The heat radiation part 4 liquefies the refrigerant by radiating the heat of the gas-phase refrigerant to the external air. In the present embodiment, the heat radiating section 4 is disposed on the upper side of the boiling heat transfer surface 34 of the refrigerant tank 3, and the vapor passage 41 through which the refrigerant vapor boiled by receiving heat from the heating element 2 passes, and the vapor passage 41. A header portion 42 that extends in the horizontal direction, a plurality of heat radiation tubes 43 that communicate with the header portion 42 and extend in the vertical direction, and heat radiation fins 44 interposed between the heat radiation tubes 43. It has.

  The lower ends of the plurality of heat radiating tubes 43 communicate with the internal space of the refrigerant tank 3, respectively. The heat radiating fins 44 are well-known corrugated fins and are used to increase the heat radiating area. Further, cooling air as an external fluid passes through the heat radiation fins 44 in the direction perpendicular to the paper surface of FIG. Hereinafter, the flow direction of the cooling air is referred to as the cooling air flow direction.

  A predetermined amount of refrigerant is sealed in the internal space of the evacuated cooling device 1.

  The cooling device 1 is made of, for example, copper or aluminum. When the cooling device 1 is made of copper, water or alcohol can be used as the refrigerant. Further, when the cooling device 1 is made of aluminum, alcohol as a refrigerant, a refrigerant that does not contain chlorine in its molecular structure, and has a small global warming coefficient or ozone depletion coefficient, specifically, a fluorine-based refrigerant or hydrofluoro An ether-based refrigerant can be used. In addition, when water is used as the refrigerant, the boiling point of water is 100 ° C. at 1 atm. However, since the cooling device 1 is evacuated, the boiling point is 30 to 40 ° C.

  FIG. 3 is an enlarged perspective view showing the boiling heat transfer surface 34 in the first embodiment. As shown in FIG. 3, the boiling heat transfer surface 34 is provided with a plurality of fins 35 for enlarging the heat transfer area and promoting thermal diffusion. The fins 35 are formed in a substantially rectangular parallelepiped shape that protrudes upward from the boiling heat transfer surface 34, that is, toward the heat radiating unit 4, and extends parallel to the flow direction of the cooling air. The plurality of fins 35 are arranged in parallel at predetermined intervals in a direction orthogonal to the flow direction of the cooling air.

  Hereinafter, the longitudinal direction of the fins 35 is referred to as a fin longitudinal direction, and the arrangement direction of the plurality of fins 35 is referred to as a fin arrangement direction. The fin longitudinal direction is parallel to the flow direction of the cooling air. The fin arrangement direction is orthogonal to the fin longitudinal direction, that is, the cooling air flow direction.

  On the upper surface of the fin 35, that is, the surface farthest from the boiling heat transfer surface 34 (hereinafter referred to as the top surface 350), a groove 36 is formed as a boiling promoting means for promoting boiling of the refrigerant on the top surface 350. ing. The groove 36 includes a first groove 361 and a second groove 362 that communicate with each other. The first groove 361 is disposed on the side farther from the boiling heat transfer surface 34 than the second groove 362, and forms an opening of the top surface 350. In the present embodiment, the first groove 361 has a rectangular cross section viewed from the fin longitudinal direction, and the second groove 362 has a circular cross section viewed from the fin longitudinal direction.

  Since the first groove portion 361 of the present embodiment is formed in a rectangular cross section, the groove width of the first groove portion 361 is constant over the fin height direction. In addition, since the second groove portion 362 of the present embodiment is formed in a circular cross section, the groove width of the second groove portion 362 changes in the fin height direction. Further, the groove width of the first groove portion 361 is smaller than the average groove width of the second groove portion 362. Accordingly, it is possible to retain the foaming nuclei that become the buds at the start of boiling inside the second groove 362.

  By the way, the temperature of the top surface 350 of the fin 35 is lowered from the root portion 351 of the fin 35, that is, the corner portion formed by the side surface 352 of the fin 35 and the boiling heat transfer surface 34. That is, the degree of superheating of the top surface 350 of the fin 35 is smaller than the root portion 351 of the fin 35. Moreover, the diameter of the bubble which can be boiled, ie, the bubble which can grow, becomes large, so that superheat degree becomes small. Therefore, in the present embodiment, the cross-sectional shape of the groove 36 is set to a shape that can hold bubbles having a bubble diameter of a size that allows boiling on the top surface 350 of the fin 350 having a small superheat degree.

  Further, the height of the groove 36 from the heating element fixing surface 320 is higher than the root portion 351 of the fin 35. That is, the root portion 351 of the fin 35 and the groove 36 are different from each other in height from the heating element fixing surface 320.

  Next, the operation of the cooling device 1 in the first embodiment will be described.

  As shown in FIG. 2, boiling occurs on the boiling heat transfer surface 34 due to the heat of the heating element 2, and bubbles 100 are generated from the liquid-phase refrigerant. Then, due to the buoyancy acting on the bubbles 100, the bubbles 100 are separated from the boiling heat transfer surface 34 and are discharged from the liquid phase refrigerant. The bubbles 100 move inside the cooling device 1 as a vapor flow 200. Then, by radiating the heat of the steam flow 200 to the air side through the radiation fins 44, the liquefied refrigerant 300 is boiled again on the boiling heat transfer surface 34. .

  FIG. 4 is an enlarged cross-sectional view showing the fin 35 in the comparative example, and FIG. 5 is an enlarged cross-sectional view showing the fin 35 in the first embodiment. 4A shows a case where the heat generation amount of the heat generating element 2 is small, and FIG. 4B shows a case where the heat generation amount of the heat generating element 2 is large.

  The fin 35 of the comparative example shown in FIG. 4 is a substantially rectangular parallelepiped projecting upward from the boiling heat transfer surface 34 and extending parallel to the cooling air flow direction, like the fin 35 of the present embodiment shown in FIG. It is formed in a shape. The plurality of fins 35 are arranged in parallel at a predetermined interval in a direction orthogonal to the cooling air flow direction. Further, the fin 35 of the comparative example has no groove formed on the top surface 350 thereof.

  When the heat generation amount of the heating element 2 is small, in the fin 35 of the comparative example, as shown in FIG. 4A, the start of boiling of the liquid-phase refrigerant occurs from the foam core 400 at the corner of the root portion 351 of the fin 35. . And if the emitted-heat amount of the heat generating body 2 increases, a boiling area will move the side surface 352 of the fin 35 toward upper direction. At this time, since the liquid-phase refrigerant is boiled also on the side surface 352 of the opposing fin 35, if the amount of heat generated by the heating element 2 is increased, the discharge performance of the bubbles 100 is lowered. In order to solve this problem, it is conceivable to increase the interval between the adjacent fins 35, but the cooling performance is deteriorated because the heat transfer area is reduced.

  Further, when the heat generation amount of the heating element 2 is large, in the fin 35 of the comparative example, the liquid-phase refrigerant boils on the side surface 352 of the fin 35 as shown in FIG.

  Therefore, the heat generated by the heating element 2 flows to the root portion 351 of the fin 35 as indicated by the arrow Y1 in FIG. 4A when the heat generation amount is small, and to the side surface 352 of the fin 35 when the heat generation amount is large. ) Flows as indicated by arrow Y2. That is, the top surface 350 of the fin 35 is not used effectively, and the effect of expanding the heat transfer area of the fin 35 is reduced. As a result, the fin 35 of the comparative example is difficult to apply to the cooling device 1 for cooling the heating element 2 that generates a large amount of heat.

  On the other hand, as shown in FIG. 5, the fin 35 of the first embodiment is provided with the groove 36 on the top surface 350 of the fin 35, so that foam nuclei that become buds of boiling start are formed inside the groove 36. Holding and inducing boiling at the top surface 350 of the fin 35. As a result, the boiling region is expanded to the root portion 351, the side surface 352, and the top surface 350 of the fin 35, and the heat generation of the heating element 2 is caused by the root portion 351, the side surface 352, and the top as indicated by the arrow Y3 in FIG. Flows to surface 350. As a result, the effect of expanding the heat transfer area is increased, and the temperature of the heating element 2 can be kept low. Further, by expanding the boiling region to the root portion 351, the side surface 352, and the top surface 350 of the fin 35, the amount of bubbles generated per unit area is reduced, and the bubble discharge property is improved. As a result, the heat removal limit of the cooling device 1 is improved.

  FIG. 6 is a characteristic diagram showing the relationship between the heating amount and the degree of superheat in the fins 35 of the first embodiment. 6 represents the ratio of the superheat degree of the fin 35 of this embodiment to the superheat degree of the fin 35 of the comparative example.

  As shown in FIG. 6, the degree of superheat of the fin 35 of the present embodiment is lower than that of the fin 35 of the comparative example both in the region where the amount of heat generated is small and in the region where the amount of heat is large. Therefore, in the fin 35 of this embodiment, since the thermal resistance at the time of boiling of the refrigerant can be reduced as compared with the fin 35 of the comparative example, the cooling performance of the entire cooling device 1 can be improved.

  As described above, the boiling of the refrigerant can be promoted by providing the fin 35 that increases the heat transfer area on the boiling heat transfer surface 34. In addition, by providing the groove 36 on the top surface 350 of the fin 35, the region where boiling occurs can be expanded, so that the amount of steam generated per unit area in the fin 35 can be reduced. In addition, by making the height of the root portion 351 and the groove 36 of the fin 35 different from the heating element fixing surface 320, the bubbles discharged from the root portion 351 of the fin 35 and the bubbles discharged from the groove 36 Can be prevented from interfering. Due to these effects, the discharge of bubbles can be improved. Therefore, even under reduced-pressure boiling conditions in which the bubbles of the boiled refrigerant become enormous, it is possible to improve the bubbling acceleration effect and improve the discharge characteristics of the bubbles from the heat transfer surface and the liquid phase refrigerant.

  Furthermore, it is possible to reduce the temperature of the boiling heat transfer surface 34, that is, the temperature of the heating element 2 by expanding the boiling occurrence region on the fin 35. In addition, by making the groove width of the first groove portion 361 smaller than the average groove width of the second groove portion 362, it is possible to hold the bubbles serving as foaming nuclei inside the second groove portion 362, thereby further promoting the boiling of the refrigerant. It becomes possible to do.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 7 is an enlarged perspective view showing the fins 35 in the second embodiment.

  As shown in FIG. 7, the second groove portion 362 in the fin 35 of the present embodiment has a rectangular cross section when viewed from the fin longitudinal direction. For this reason, the groove width of the second groove portion 362 is constant in the fin height direction. In the present embodiment, the groove width of the first groove portion 361 is smaller than the groove width of the second groove portion 362.

  According to this, since the region where boiling occurs can be enlarged, the amount of steam generated per unit area in the fin 35 can be reduced. Furthermore, the bubbles discharged from the root portion 351 of the fin 35 and the bubbles discharged from the groove 36 can be prevented from interfering with each other. Due to these effects, the discharge of bubbles can be improved. Therefore, even under reduced-pressure boiling conditions in which the bubbles of the boiled refrigerant become enormous, it is possible to improve the bubbling acceleration effect and improve the discharge characteristics of the bubbles from the heat transfer surface and the liquid phase refrigerant.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 8 is an enlarged perspective view showing the fins 35 in the third embodiment.

  As shown in FIG. 8, the top surface 350 of the fin 35 of the present embodiment is provided with a protrusion 37 that promotes boiling of the refrigerant on the top surface 350. The protrusion 37 protrudes upward from the top surface 350, that is, in a direction away from the boiling heat transfer surface 34. In the present embodiment, the protruding portion 37 is formed integrally with the fin 35. The surface of the protrusion 37 that is farthest from the boiling heat transfer surface 34 (hereinafter referred to as the upper surface 370) is parallel to the top surface 350 of the fin 35.

  The protrusion 37 has a substantially T-shaped cross section when viewed from the fin longitudinal direction. More specifically, the cross-sectional area of the portion close to the top surface 350 of the fin 35 in the protrusion 37 is a portion of the portion of the protrusion 37 that is far from the top surface 350 of the fin 35, that is, the portion constituting the upper surface 370. It is smaller than the area.

  Further, the protrusion 37 is higher in height from the heating element fixing surface 320 than the base portion 351 of the fin 35. That is, the root portion 351 and the protrusion portion 37 of the fin 35 are different from each other in height from the heating element fixing surface 320.

  In this way, by providing the protrusion 37 projecting in the direction away from the boiling heat transfer surface 34 on the top surface 350 of the fin 35, the region where the boiling occurs can be expanded, so that the unit area per unit area in the fin 35 can be increased. Steam generation can be reduced. Further, the height of the root portion 351 of the fin 35 and the protrusion portion 37 from the heating element fixing surface 320 is made different from each other, whereby the bubbles discharged from the root portion 351 of the fin 35 and the protrusion portion 37 are discharged. Interference with air bubbles can be prevented. Due to these effects, the discharge of bubbles can be improved. Therefore, even under reduced-pressure boiling conditions in which the bubbles of the boiled refrigerant become enormous, it is possible to improve the bubbling acceleration effect and improve the discharge characteristics of the bubbles from the heat transfer surface and the liquid phase refrigerant.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described based on FIG. 9 and FIG. FIG. 9 is an enlarged perspective view showing the fins 35 in the fourth embodiment.

  As shown in FIG. 9, a connection portion 355 that extends in the fin arrangement direction and connects the plurality of fins 35 is provided at a substantially central portion in the longitudinal direction of the fins 35. The connecting portion 355 is formed integrally with the plurality of fins 35. Here, the distance between the side surfaces 351 of adjacent fins 35, that is, the length in the fin arrangement direction is referred to as a fin pitch.

  Further, the fin 35 of the fourth embodiment is configured by stacking four plates 38 as thin plates formed in a predetermined shape in the plate thickness direction. The four plates 38 are press materials punched out of a press die from, for example, an aluminum plate or a stainless steel plate.

  The four plates 38 include two lower plates 381 disposed on the side close to the boiling heat transfer surface 34, one intermediate plate 382 disposed on the upper side of the two lower plates 381, The upper plate 383 is disposed on the upper side of the intermediate plate 382, that is, at the position farthest from the boiling heat transfer surface 34.

  FIG. 10 is a plan view showing the plate 38 forming the fins 35 in the fourth embodiment, where (a) shows the upper plate 383, (b) shows the intermediate plate 382, and (c) shows the lower plate 381. . In addition, the broken line in Fig.10 (a)-(c) has shown the arrangement | positioning site | part of the heat generating body 2. FIG.

  As shown in FIG. 10C, the lower plate 381 is provided with a plurality of slit-shaped first notches 391 from both ends in the fin longitudinal direction toward the center in the fin longitudinal direction. Accordingly, the fins 35 are formed between the first cutout portions 391 adjacent in the fin arrangement direction, and the connection portion 355 is formed between the first cutout portions 391 adjacent in the fin longitudinal direction. The width W1 of the first notch portion 391, that is, the length in the fin arrangement direction is equal to the fin pitch.

  As shown in FIG. 10B, the intermediate plate 382 is provided with a plurality of first cutout portions 391 similarly to the lower plate 381. Furthermore, a slit-shaped second notch 392 is provided from the both ends in the fin longitudinal direction toward the center in the fin longitudinal direction at a portion between the first notches 391 adjacent to the fin arrangement direction in the intermediate plate 382. ing. The width W2 of the second notch 392, that is, the length in the fin arrangement direction, is smaller than the width W1 of the first notch 391. Further, the length of the second notch 392, that is, the length in the fin longitudinal direction is equal to the length of the first notch 391.

  As shown in FIG. 10A, the upper plate 383 is provided with a plurality of first cutout portions 391 as with the lower plate 381 and the intermediate plate 382. Furthermore, a slit-like third notch portion 393 is provided in the lower plate 383 between the first notch portions 391 adjacent to each other in the fin arrangement direction from both end portions in the fin longitudinal direction toward the center portion in the fin longitudinal direction. It has been. The width W3 of the third notch 393, that is, the length in the fin arrangement direction is smaller than the width W2 of the second notch 392. The length of the third notch 393, that is, the length in the fin longitudinal direction, is equal to the length of the first and second notches 391 and 392.

  As shown in FIG. 9, the plurality of plates 381 to 383 formed in this manner are stacked in the order of two lower plates 381, an intermediate plate 382, and an upper plate 383 from the side close to the boiling heat transfer surface 34. The fins 35 are formed by thermally connecting the boiling heat transfer surface 34 and the plates 381 to 383 by brazing or welding.

  At this time, the second notch 392 of the intermediate plate 382 and the third notch 393 of the upper plate 383 communicate with each other to form the groove 36. More specifically, the first groove 361 is formed by the third notch 393 of the upper plate 383, and the second groove 362 is formed by the second notch 392 of the intermediate plate 382.

  As described above, by providing the fins 36 with the grooves 36, it is possible to expand the region where boiling occurs, so that the amount of steam generated per unit area in the fins 35 can be reduced. Furthermore, the bubbles discharged from the root portion 351 of the fin 35 and the bubbles discharged from the groove 36 can be prevented from interfering with each other. Due to these effects, the discharge of bubbles can be improved. Therefore, even under reduced-pressure boiling conditions in which the bubbles of the boiled refrigerant become enormous, it is possible to improve the bubbling acceleration effect and improve the discharge characteristics of the bubbles from the heat transfer surface and the liquid phase refrigerant.

  Furthermore, since the fins 35 can be formed simply by laminating the four plates 38, the fins 35 can be easily manufactured.

(Fifth embodiment)
Next, a fifth embodiment of the present invention will be described with reference to FIGS. FIG. 11 is an exploded perspective view showing the fins 35 in the fifth embodiment, and FIG. 12 is a cross-sectional view taken along line AA of FIG.

  As shown in FIGS. 11 and 12, the fin 35 according to the present embodiment includes a fin member 35 </ b> A and a plate-like member 70. The fin member 35 </ b> A protrudes from the boiling heat transfer surface 34 toward the upper side, that is, toward the heat radiating unit 4, and is formed in a substantially rectangular parallelepiped shape extending in parallel with the cooling air flow direction. The plurality of fin members 35A are arranged in parallel at a predetermined interval in a direction orthogonal to the flow direction of the cooling air.

  On the top surface 350A of the fin member 35A, that is, the surface having the highest height from the boiling heat transfer surface 34, a groove 36 extending in the fin longitudinal direction is formed. The groove 36 has a rectangular shape as viewed from the fin longitudinal direction.

  On the upper side of the fin member 35A, a plate-like member 70 having a plurality of first and second openings 71 and 72 penetrating in the plate thickness direction is disposed so as to contact the top surface 350A. The first and second openings 71 and 72 each have a slit shape extending in the fin longitudinal direction, and are alternately arranged in the fin arrangement direction.

  The first opening 71 is formed so as to communicate with the groove 36 when the plate-like member 70 is disposed above the fin member 35A. When the fin plate member 70 is disposed above the fin member 35A, the second opening 72 has a surface 720 parallel to the fin longitudinal direction of the inner peripheral surface of the second opening 72. It is formed so as to be flush with the side surface 352A. The opening width of the first opening 71, that is, the length in the fin arrangement direction is smaller than the groove width of the groove 36. Further, the upper surface of the plate-like member 70 constitutes the top surface 350 </ b> A of the fin 35.

  Although the plate member 70 does not need to be thermally connected to the fin member 35A, in this embodiment, the plate member 70 is a fin in order to prevent the plate member 70 from moving due to flowing bubbles. It is fixed to the member 35A.

  According to this embodiment, since the region where boiling occurs can be enlarged, the amount of steam generated per unit area in the fin 35 can be reduced. Furthermore, the bubbles discharged from the root portion 351 of the fin 35 and the bubbles discharged from the groove 36 can be prevented from interfering with each other. Due to these effects, the discharge of bubbles can be improved. Therefore, even under reduced-pressure boiling conditions in which the bubbles of the boiled refrigerant become enormous, it is possible to improve the bubbling acceleration effect and improve the discharge characteristics of the bubbles from the heat transfer surface and the liquid phase refrigerant.

  Furthermore, by making the opening width of the first opening 71 smaller than the groove width of the groove 36, it is possible to hold bubbles serving as foaming nuclei inside the groove 36, thereby further promoting the boiling of the refrigerant. It becomes.

(Sixth embodiment)
Next, a sixth embodiment of the present invention will be described with reference to FIGS. The same parts as those in the fifth embodiment are denoted by the same reference numerals and description thereof is omitted.

  FIG. 13 is an exploded perspective view showing the fins 35 in the sixth embodiment, and FIG. 14 is a sectional view taken along line BB in FIG. As shown in FIGS. 13 and 14, a guide 80 serving as a vapor discharge promoting means for promoting the discharge of the refrigerant vapor boiled by the fins 35 is disposed above the plate-like member 70.

  The guide 80 includes a substantially rectangular frame-shaped outer frame portion 81 that forms a vapor passage 800 through which refrigerant vapor passes, and a partition member 82 that extends in the fin longitudinal direction and partitions the vapor passage 800 in the fin arrangement direction. .

  The outer frame portion 81 is formed so that the cross-sectional area of the steam passage 800 increases toward the upper side. Specifically, of the four wall portions constituting the outer frame portion 81, the two wall portions 81a arranged substantially parallel to the fin longitudinal direction are directed outward in the fin arrangement direction toward the upper side. Inclined with respect to the vertical direction. Of the four wall portions constituting the outer frame portion 81, the two wall portions 81 b arranged substantially parallel to the fin arrangement direction are vertically oriented so as to go outward in the fin longitudinal direction toward the upper side. It is inclined with respect to.

  The number of the partition members 82 is one less than the plurality of fins 35 disposed on the boiling heat transfer surface 34 (five in this embodiment). Thereby, the steam passage 800 formed in the guide 8 is partitioned into six narrow passages 801 and 802. Further, the five partition members 82 are arranged so that the respective lower ends thereof face the space formed between the two adjacent fins 35 when the guide 80 is disposed above the plate-like member 70. Has been.

  Of the five partition members 82, the partition member (hereinafter referred to as the center partition member 82a) disposed at the center in the fin arrangement direction is parallel to the fin longitudinal direction and orthogonal to the fin arrangement direction. Is arranged. Of the five partition members 82, the four partition members excluding the central partition member 82 a (hereinafter referred to as a general partition member 82 b) are directed in the vertical direction so as to go outward in the fin arrangement direction toward the upper side. It is inclined. For this reason, in all the six narrow passages 801 and 802 formed in the guide 80, the passage cross-sectional area of the narrow passages 801 and 802 increases toward the upper side.

  Here, of the six narrow passages 801 and 802, two narrow passages arranged on the inner side in the fin arrangement direction are referred to as an inner steam passage 801, and two narrow passages arranged on the outer side in the fin arrangement direction are outer steam. It is called passage 802. The length W11 in the fin arrangement direction at the upper end portion of the inner steam passage 801 is longer than the length W12 in the fin arrangement direction at the upper end portion of the outer steam passage 802.

  By the way, when the center part of the heat generating body 2 is hotter than the other part, the amount of bubbles generated is the largest in the part corresponding to the center part of the heat generating element 2. As a result, at the portion corresponding to the central portion of the heating element 2, the liquid level of the liquid phase refrigerant when the refrigerant boils rises from the liquid level of the liquid phase refrigerant when it does not boil. Thereby, there exists a problem that the bubble of a refrigerant | coolant becomes difficult to be discharged | emitted from a liquid phase refrigerant | coolant. In addition, depending on the height of the refrigerant tank 3, the liquid-phase refrigerant directly flows into the heat radiating unit 4, so that there is a problem in that a phase change of the refrigerant cannot be expected in the heat radiating unit 4 and latent heat cannot be transported. Further, when the liquid phase refrigerant flows into the heat radiating section 4, there is a problem that the liquid phase refrigerant closes the vapor passage 41.

  On the other hand, as in this embodiment, the guide 80 having the outer frame portion 81 that forms the steam passage 800 and the partition member 82 that partitions the steam passage 800 into a plurality of narrow passages 801 and 802 is provided above the fins 35. And the outer frame portion 81 and the partition member 82 are formed so that the passage cross-sectional areas of the narrow passages 801 and 802 increase toward the upper side, so that the central portion of the heating element 2 has a higher temperature than other portions. Even in this case, the bubbles discharged from the fins 35 can flow smoothly. For this reason, it becomes possible to improve the discharge | emission property of the bubble from a liquid phase refrigerant | coolant, and to prevent that a liquid phase refrigerant | coolant flows in into the thermal radiation part 4. FIG.

(Other embodiments)
In addition, you may combine each above-mentioned embodiment suitably in the possible range. For example, the guide 80 in the sixth embodiment may be disposed above the fins 35 in the first embodiment.

It is a perspective view which shows the cooling device 1 which concerns on 1st Embodiment. It is sectional drawing which shows the cooling device 1 which concerns on 1st Embodiment. It is an expansion perspective view which shows the boiling heat transfer surface 34 in 1st Embodiment. It is an expanded sectional view showing fin 35 in a comparative example. It is an expanded sectional view showing fin 35 in a 1st embodiment. It is a characteristic view which shows the relationship between the heating amount in the fin 35 of 1st Embodiment, and a superheat degree. It is an expansion perspective view which shows the fin 35 in 2nd Embodiment. It is an expansion perspective view which shows the fin 35 in 3rd Embodiment. It is an expansion perspective view which shows the fin 35 in 4th Embodiment. FIG. 10 is a plan view showing a plate 38 forming the fins 35 in the fourth embodiment, where (a) shows an upper plate 383, (b) shows an intermediate plate 382, and (c) shows a lower plate 381. It is a disassembled perspective view which shows the fin 35 in 5th Embodiment. It is AA sectional drawing of FIG. It is a disassembled perspective view which shows the fin 35 in 6th Embodiment. It is BB sectional drawing of FIG.

Explanation of symbols

2 Heating Element 3 Refrigerant Tank 4 Heat Dissipating Part 31 Bottom Wall 34 Boiling Heat Transfer Surface 35 Fin 36 Groove (Boiling Promoting Means)
37 Protrusion (boiling promotion means)
38 Thin plate 70 Plate member 80 Guide (Vapor discharge promotion means)
81 Outer frame portion 82 Partition member 320 Heating element fixing surface 350 Top surface

Claims (7)

A part of the outer surface (32) of the bottom wall (31) is a heating element fixing surface (320) to which the heating element (2) is fixed, and boiled by receiving heat from the heating element (2). A refrigerant tank (3) for storing a liquid phase refrigerant;
A cooling device comprising a heat radiating section (4) for allowing the refrigerant vapor boiled in the refrigerant tank (3) to flow in, exchanging heat between the refrigerant vapor and an external fluid, and condensing the refrigerant vapor,
The part corresponding to the heating element fixing surface (320) in the inner surface (33) of the bottom wall (31) of the refrigerant tank (3) is a boiling heat transfer surface (34) that promotes boiling of the liquid phase refrigerant. And
The boiling heat transfer surface (34) has a top surface (350) that rises from the boiling heat transfer surface (34) and increases the heat transfer area of the boiling heat transfer surface (34) ( 35)
The top surface (350) of the fin (35) is provided with boiling promotion means (36, 37) for promoting boiling of the liquid-phase refrigerant on the top surface (350). Cooling system.   The corner portion (351) formed by the side surface (352) of the fin (35) and the boiling heat transfer surface (34), and the boiling promoting means (36, 37) are formed on the heating element fixing surface (320). The cooling device according to claim 1, wherein the heights from are different. The top surface (350) is provided with a protrusion (37) protruding in a direction away from the boiling heat transfer surface (34),
The cross-sectional area of the protrusion (37) on the side close to the top surface (350) is the cross-sectional area of the surface (370) having the highest height from the boiling heat transfer surface (34) in the protrusion (37). Smaller,
The cooling device according to claim 1 or 2, wherein the top surface (350) constitutes the boiling promotion means. The top surface (350) is provided with a groove (36),
The groove (36) is composed of a first groove part (361) and a second groove part (362) communicating with each other,
The first groove portion (361) is disposed on a side farther from the boiling heat transfer surface (34) than the second groove portion (362) and forms an opening on the top surface (350) side. ,
The groove width of the first groove part (361) is smaller than the groove width of the second groove part (362),
The cooling device according to claim 1 or 2, wherein the groove (36) constitutes the boiling promotion means.   The said fin (35) is comprised by laminating | stacking a plurality of thin plates (38) in the plate | board thickness direction of the said thin plate (38), The structure of any one of Claim 1 thru | or 4 characterized by the above-mentioned. Cooling system. A groove (36) having a substantially rectangular cross section is formed on the top surface (350), and a plate-like member (70) having an opening (71) penetrating in the plate thickness direction is formed on the groove (36). ) And the opening (71) communicate with each other,
The opening width of the opening (71) is smaller than the groove width of the groove (36),
The cooling device according to claim 1 or 2, wherein the groove (36) constitutes the boiling promotion means. On the far side of the fin (35) from the boiling heat transfer surface (34), steam discharge promoting means (80) for promoting discharge of the refrigerant vapor boiled at the fin (35) is provided,
The vapor discharge promoting means (80) partitions the outer frame portion (81) forming a vapor passage (800) through which the refrigerant vapor passes and the vapor passage (800) into a plurality of narrow passages (801, 802). A partition member (82),
The outer frame portion (81) and the partition member (82) are formed such that the passage cross-sectional area of the narrow passages (801, 802) increases toward the side away from the boiling heat transfer surface (34). The cooling device according to any one of claims 1 to 6, wherein:

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