Cooling device and cooling unit using latent heat of evaporation

Abstract

To provide a cooling device and a cooling unit that utilizes latent heat of evaporation and enables the entire device to be miniaturized. [Solution] A metal heat receiver (14) receives heat from a heating element (21) on one side and has multiple fins (14a) erected on the other side, thereby vaporizing the working fluid supplied to the base of each erected fin; a metal slit electrode having multiple electrode plates (15b) inserted in a non-contact state between the multiple fins formed on the heat receiver, with the base end of each electrode plate opened in a slit shape to form a flow path (15c) for the working fluid; and a DC power source (17) that generates an electric field between the alternatingly adjacent fins (14a) of the heat receiver and the electrode plates (15b) of the slit electrode by applying a DC voltage between the heat receiver (14) and the slit electrode (15).

Description

[Technical Field]

[0001] The present invention relates to a cooling device and a cooling unit that utilize latent heat of evaporation and that can be suitably used to cool laser diodes used as light sources for large-screen projection by projection mapping, for example. [Background technology]

[0002] Due to the demand for large-screen projection by the above-mentioned projection mapping, the output of laser diodes, which are the light sources, is increasing, and therefore cooling design is becoming increasingly important. Conventionally, this type of large projector has adopted a cooling device of the so-called water-cooling type, in which a fluid whose temperature has risen due to heat from the laser diode is cooled by a radiator, and the cooled fluid is returned to the heat-receiving part to circulate the fluid.

[0003] Similar water-cooled cooling devices are also used in power semiconductors used for driving control in fuel cell vehicles and electric vehicles, and in various industrial equipment such as laser processing machines and exposure machines. However, in recent years, as the output of power devices including the above-mentioned laser diodes has become even higher, the heat density from the power devices has been increasing, and this has led to an increase in the size of cooling devices.

[0004] Under such circumstances, the water-cooling method, which is the mainstream of conventional cooling devices, is insufficient in terms of capacity. For this reason, the inventor of the present application has previously proposed a cooling device that can efficiently cool heat-generating elements such as the power devices by utilizing the latent heat of evaporation when a working fluid serving as a cooling medium changes from a liquid phase (liquid) to a gas phase (gas), and this is disclosed in Patent Document 1.

[0005] Figures 11 and 12 show the cooling unit portion that constitutes the cooling device disclosed in Patent Document 1. That is, Figure 11 is a vertical cross-sectional view of cooling unit 91, and Figure 12 shows, in a partially enlarged cross-sectional view, the relationship between heat receiving plate 94 and electrode 95 with slit 95a that constitute cooling unit 91. The cooling unit 91 disclosed in Patent Document 1 has a rectangular conductive heat receiving plate 94 and an electrode 95 with multiple slits 95a attached at a predetermined interval to a frame-shaped lower case 92 with a spacer 92a, as shown in Figure 11, and the back surface of the heat receiving plate 94 forms the bottom surface of the lower case 92.

[0006] A rectangular upper case 93 is attached to the lower case 92 so as to cover an electrode 95 having a plurality of slits 95a, and a DC power supply 97 is provided between the electrode 95 and the heat receiving plate 94 to apply a predetermined voltage (several kV). A working fluid inlet 92b for introducing a working fluid as a cooling medium into the lower case 92 is formed in a part of the lower case 92, and a working fluid outlet 93a for discharging the working fluid is formed in a part of the upper case 93. A heat-generating element 99 such as a laser diode to be cooled by the cooling unit 91 is attached in close contact with the back surface of the heat-receiving plate 94.

[0007] A working fluid that boils and vaporizes below the upper limit of the allowable temperature of the heating element 99 is introduced into the working fluid inlet 92b. Therefore, the working fluid introduced into the lower case 92 from the working fluid inlet 92b receives heat from the heating element 99 via the heat receiving plate 94, boils and vaporizes, and is sent into the upper case 93 in a mixed state of liquid and gas phases through each of the multiple slits 95a formed in the electrode 95. The working fluid in the upper case 93 is then sent to the radiator from the working fluid outlet 93a of the upper case 93, where it is liquefied and condensed, and is then introduced again into the working fluid inlet 92b of the cooling unit 91 by the pump. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 6603895 Summary of the Invention [Problem to be solved by the invention]

[0009] Incidentally, the cooling unit 91 disclosed in Patent Document 1 employs a configuration in which a DC voltage is applied between an electrode 95 having a plurality of slits 95a and a heat receiving plate 94 facing it, as shown in FIG. 11, and this is called the microslit channel method (MSC method). According to this, an electric field is applied between each electrode 95 and the heat receiving plate 94, with the electric field lines indicated by the dashed lines, as shown in Figure 12. As will be explained in detail later, the effect of applying this electric field can be improved in the area where the electric field is formed, thereby reducing the thermal resistance and increasing the cooling effect on the heating element 99. However, the cooling effect on the heating element 99 by the MSC method described above occurs only in the local area between the tip of each electrode 95 and the opposing heat receiving plate 94, as shown in Figure 12. For this reason, the cooling effect achieved by adopting the MSC method cannot be fully exerted, and there is still room for improvement.

[0010] The present invention has been made in consideration of the above-mentioned problems, and aims to further increase the cooling efficiency of the heat-generating body by expanding the surface area on the heat receiving plate side where the electric field is formed, thereby providing a cooling device and cooling unit that utilizes the latent heat of evaporation and enables the entire device to be made smaller. [Means for solving the problem]

[0011] The cooling device according to the present invention, which has been made to solve the above-mentioned problems, comprises a cooling unit that receives heat from a heat-generating element and causes a phase change of at least a part of a working fluid from a liquid phase to a gas phase to cool the heat-generating element, a radiator that receives the working fluid that has undergone the phase change in the cooling unit and cools it to liquefy and condense the working fluid, and a pump that sends the working fluid liquefied by the radiator to the cooling unit, and the cooling device circulates the working fluid between the cooling unit and the radiator, and the cooling unit has a surface that is refrigerated from the heat-generating element. the metal heat receiver that receives heat from the heat receiving body and has a plurality of fins erected on the other surface thereof, thereby vaporizing the working fluid supplied to the base of each erected fin; a metal slit electrode that has a plurality of electrode plates that are inserted in a non-contact state between the plurality of fins formed on the heat receiver, and the base end of each electrode plate is opened in a slit shape to form a flow path for the working fluid; and a DC power source that generates an electric field between the fins of the heat receiver and the electrode plate of the slit electrode that are alternately adjacent to each other by applying a DC voltage between the heat receiver and the slit electrode.

[0012] The cooling unit according to the present invention, which has been made to solve the above-mentioned problems, is a cooling unit that receives heat from a heat generating element and changes the phase of at least a part of a working fluid from a liquid phase to a gas phase to cool the heat generating element, and the cooling unit has a metal heat receiving element that receives heat from the heat generating element on one side and has a plurality of fins erected on the other side, thereby vaporizing the working fluid supplied to the base of each erected fin, and a plurality of electrode plates that are inserted in a non-contact state between the plurality of fins formed on the heat receiving element, and a base end of each of the electrode plates is The device comprises a metal slit electrode that is opened in a slit shape to form a flow path for the working fluid, a first case that holds the heat receiver and the slit electrode, with the one surface of the heat receiver as its bottom surface and that forms an inlet for the working fluid, a second case that covers the slit electrode, is placed on top of the first case or is molded integrally with the first case, and forms an outlet for the working fluid, and a DC power supply that applies a DC voltage between the heat receiver and the slit electrode to generate an electric field between the fins of the heat receiver and the electrode plate of the slit electrode that are alternately adjacent to each other.

[0013] In this case, in the first embodiment of the cooling unit, the multiple fins formed on the heat receiving body are each formed as flat plates of equal thickness and arranged at equal intervals, and the multiple electrode plates formed on the slit electrode are each formed as flat plates of equal thickness and arranged at equal intervals, so that each fin and each electrode plate inserted between each fin in a non-contact state are arranged parallel to each other and at equal intervals.

[0014] In the second embodiment of the cooling unit, the plurality of fins formed on the heat receiving body are each Former The thickness of the fins gradually decreases from the base to the other end, and the electrode plates formed on the slit electrode are formed as flat plates of equal thickness and are arranged at equal intervals, so that the distance between each fin and each electrode plate inserted between the fins in a non-contact state gradually increases from the base to the other end of each fin.

[0015] Furthermore, in a third embodiment of the cooling unit, a plurality of fins formed on the heat receiving body are Former The thickness of the fins gradually decreases from the base to the other end, and the plurality of electrode plates formed on the slit electrode are formed in the shape of flat plates with the same thickness and are arranged at equal intervals, so that the interval between each fin and each electrode plate inserted between the fins in a non-contact state gradually increases from the base of each fin to the other end, and Former Between the sections, a circular groove is formed. Former It is characterized by being formed along the part.

[0016] The first case has a plurality of fins extending from the inlet of the working fluid to the heat receiving body. Former At both ends of the section, a guide passage for guiding the working fluid is formed. Furthermore, the slit electrode is made of aluminum, and an insulating layer of anodized aluminum is formed on the entire surface of the slit electrode. In this case, it is desirable that a positive voltage of the DC power supply is applied to the electrode plate of the slit electrode, and a negative voltage is applied to the fin of the heat receiving body. [Effects of the Invention]

[0017] In the cooling device and cooling unit according to the present invention, a heat receiving body that receives heat from a heat generating body is provided with a plurality of fins erected thereon and a slit electrode having a plurality of electrode plates inserted between the fins in a non-contact manner. In addition, a DC voltage is applied between the heat receiving body and the slit electrode, and an electric field is formed between the alternatingly adjacent fins of the heat receiving body and the electrode plates formed on the slit electrode. In the area where this electric field is formed, the supply effect of the liquid phase working fluid is enhanced, resulting in an improvement in the heat transfer coefficient to the working fluid, which can contribute to a reduction in thermal resistance.

[0018] Therefore, with the cooling device and cooling unit of the present invention, the increased heat dissipation area due to the multiple fins erected on the heat receiving body and the increased area for forming the electric field described above act synergistically, thereby making it possible to achieve high cooling efficiency for the heat generating body. This makes it possible to provide a cooling device and a cooling unit that enable the overall device to be miniaturized. Other characteristic functions and effects of the cooling unit according to the present invention will be described as appropriate in the explanation of the embodiments to be described later. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a schematic diagram showing a basic configuration of a cooling device according to the present invention. [Figure 2] 2 is a perspective view showing the external configuration of a cooling unit provided in the cooling device shown in FIG. 1. FIG. [Figure 3] FIG. 2 is a vertical cross-sectional view of the cooling unit of the first embodiment. [Figure 4] FIG. 10 is a perspective view showing the relationship between a heat receiving body and a slit electrode in the cooling unit of the first embodiment. [Figure 5] The individual components of the slit electrode are shown, with (A) being a top view, (B) being a perspective view, and (C) being an enlarged cross-sectional view of a portion. [Figure 6] 4 is a cross-sectional view of the first case taken along line II in FIG. 3 in the direction of the arrow. [Figure 7] 10A and 10B are schematic diagrams illustrating the effects of an electric field applied between the fins of the heat receiving body and the electrode plate of the slit electrode. [Figure 8] FIG. 2 is a partially enlarged cross-sectional view of the cooling unit of the first embodiment. [Figure 9] FIG. 10 is a partially enlarged cross-sectional view of a cooling unit according to a second embodiment. [Figure 10] FIG. 10 is a partially enlarged cross-sectional view of a cooling unit according to a third embodiment. [Figure 11] FIG. 1 is a vertical cross-sectional view showing an example of a conventional cooling unit. [Figure 12]12 is a partially enlarged cross-sectional view showing the relationship between the heat receiving plate and the electrodes of the cooling unit shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0020] The following describes an embodiment of a cooling device according to the present invention and a cooling unit used in the cooling device, with reference to the drawings. Note that the drawings described below are schematic diagrams that have been appropriately emphasized, partially omitted, and adjusted in proportion to illustrate the embodiment of the present invention, and may differ from the actual shapes, positional relationships, and proportions.

[0021] FIG. 1 shows the basic configuration of a cooling device according to the present invention. 1, cooling device 10 is a system that receives heat emitted from a heat generating element 21 such as a laser diode using cooling unit 11 and dissipates the heat using heat radiator 31, thereby cooling heat generating element 21. This system includes cooling unit 11, heat radiator 31, pump 41, and pipe member 51 that circulates working fluid in the direction of the arrow. The working fluid is a fluid for transporting heat, and in this specification and claims, it is used to include liquids, gases, and fluids in a mixed state of liquid and gas.

[0022] The cooling unit 11 receives heat from a heating element 21 such as the laser diode and has the function of cooling the heating element 21 by utilizing the latent heat of evaporation that occurs when at least a portion of the working fluid changes from a liquid phase (liquid) to a gas phase (vapor). The outer shell of the cooling unit 11 in this embodiment is configured by placing a second case 13 on a rectangular first case 12, and the internal configuration of the cooling unit 11 will be described later with reference to FIGS.

[0023] The radiator 31 is a heat exchanger that receives the working fluid sent from the cooling unit 11 and exchanges heat between the working fluid flowing inside the radiator and fluid in contact with the outside. In addition, since the vaporized working fluid is liquefied inside the radiator 31, the radiator 31 also functions as a condenser. The radiator 31 shown in this example includes, for example, a plurality of thin tubes (not shown) arranged at predetermined intervals and a fan 32 that circulates air between the thin tubes, and has the function of cooling the working fluid by exchanging heat between the working fluid flowing inside the thin tubes and the air, thereby liquefying the working fluid in a vaporized state.

[0024] The pump 41 serves to forcibly send the working fluid from the radiator 31 to the cooling unit 11 through a pipe member 51. Although the pump 41 is provided in the pipe member 51 that sends the working fluid from the radiator 31 to the cooling unit 11 in FIG. 1, the pump 41 may also be provided in the pipe member 51 that sends the working fluid from the cooling unit 11 to the radiator 31.

[0025] 2 to 6 show the configuration of cooling unit 11. As described above, this cooling unit 11 has an outer shell configured by placing second case 13 on top of square-shaped first case 12, and Fig. 3 shows cooling unit 11 in a vertical cross section. As shown in Figure 3, the cooling unit 11 comprises a rectangular conductive heat receiving body 14 equipped with a heating element 21 such as a laser diode, and a metal slit electrode 15 having a plurality of electrode plates 15b, which are attached at a predetermined interval to a frame-shaped first case 12 equipped with spacers 12a, and one side of the heat receiving body 14 equipped with the heating element 21 forms the bottom surface of the first case 12.

[0026] A second case 13 formed in a rectangular shape is attached to the first case 12 so as to cover the slit electrode 15 . A DC power supply 17 is provided between the slit electrode 15 disposed in the first case 12 and the heat receiving body 14 to apply a predetermined voltage. 2, in this embodiment, the inlet 12b for the working fluid is formed in the side wall of the first case 12. Also, the outlet 13a for the working fluid is formed in the top surface of the second case 13, but it can also be formed in the side surface of the second case 13.

[0027] As shown in FIGS. 3 and 4, on the other surface of the rectangular heat receiving body 14, i.e., on the upper surface of the heat receiving body 14, a plurality of fins 14a are provided perpendicular to the surface of the heat receiving body 14, and the fins 14a are formed in the shape of a rectangular plate, parallel to each other at equal intervals and with the same thickness. The material for the heat receiving body 14 and the fins 14a is preferably a material with high electrical and thermal conductivity, and metals such as copper and aluminum, or other alloys can be used. In this embodiment, copper is used for the heat receiving body 14 and the fins 14a. The fins 14a function as electrodes on the heat receiving body 14 side by facing the electrode plates 15b arranged on the slit electrode 15 described later.

[0028] Furthermore, it is desirable that the upper surface of the heat receiving body 14 on which the fins 14a are formed and the entire surface of each fin 14a be subjected to a so-called rough surface treatment, which creates minute irregularities. This makes it easier for bubbles to be generated from the working fluid, thereby promoting the evaporation of the working fluid. In this case, a method of roughening the surface can be adopted, such as coating (electrodeposition) with powder such as diamond, which has high thermal conductivity.

[0029] FIG. 5 shows the structure of the slit electrode 15 alone. The slit electrode 15 is configured by attaching both ends of a plurality of electrode plates 15b to two opposing longitudinal sides of a rectangular support frame 15a, and the base end of each electrode plate 15b on the support frame 15a side is opened in a slit shape to form a flow path 15c for the working fluid. As shown in FIG. 5(B), one of the electrode plates 15b is integrally formed with a gripping portion 15d that protrudes upward.

[0030] The electrode plates 15b are attached to the support frame 15a so as to be parallel to each other with the same intervals, and are formed into rectangular strips with the same thickness. The material constituting the electrode plates 15b is not particularly limited as long as it is an electrically conductive material, and metals such as copper and aluminum or alloys can be used, as with the materials of the heat receiving body 14 and the fins 14a. In this embodiment, the entire slit electrode 15, including the electrode plate 15b and the support frame 15a, is made of aluminum, the reason for which will be explained later.

[0031] FIG. 4 shows a state in which each electrode plate 15b of the slit electrode 15 is inserted between a plurality of fins 14a formed on the heat receiving body 14. In this embodiment, when the interval between the fins 14a formed on the heat receiving body 14 is a, the thickness of each fin 14a is b, the interval between the fins 14a and the electrode plate 15b is c, and the distance between the lower end of the electrode plate 15b and the heat receiving body 14 is d, The values ​​are set as a=1.7mm, b=0.5mm, c=0.6mm, and d=0.6mm. Furthermore, when the distance between the electrode plates 15b in the slit electrode 15 shown in FIG. 5(C) is e and the thickness of each electrode plate 15b is f, The values ​​are set to e=1.7 mm and f=0.5 mm.

[0032] As a result, in this embodiment, the multiple fins 14a formed on the heat receiving body 14 are each formed in a flat plate shape with the same thickness (b) and are arranged at equal intervals (a), the multiple electrode plates 15b formed on the slit electrode 15 are each formed in a flat plate shape with the same thickness (f) and are arranged at equal intervals (e), and a configuration is adopted in which each fin 14a and each electrode plate 15b inserted between each fin 14a in a non-contact state are arranged parallel to each other and at equal intervals (c).

[0033] The numerical values ​​of a to e are not particularly limited, as the optimum values ​​vary depending on, for example, the voltage applied between the slit electrode 15 and the heat receiving body 14, the flow velocity of the working fluid, etc. However, in this embodiment, the values ​​are selected based on the values ​​that can be machined under the current circumstances when the fins 14a of the heat receiving body 14 are formed by cutting. As shown in FIG. 4, an output voltage from the DC power supply 17 is applied between the electrode plate 15b of the slit electrode 15 and the fins 14a of the heat receiving body 14, and an electric field is applied as shown by the broken electric field lines.

[0034] FIG. 6 is a cross-sectional view of the first case 12 taken along line II in FIG. 3 and seen in the direction of the arrow. As shown in FIG. 6, the first case 12 has a plurality of fins 14a extending from an inlet 12b for the working fluid to the roots of the heat receiving body 14. Former At both ends of the portion, a conducting passage 12c for conducting the working fluid is formed. Therefore, the working fluid supplied to the working fluid inlet 12b is divided into left and right as shown by the broken lines and is guided to both ends of each fin 14a through the guide passage 12c. Then, the working fluid flows through the roots of each fin 14a as shown by the arrows. Former The air is supplied along the portion toward the center of each fin 14a. As a result, the working fluid receives heat from the heat receiver 14 and each fin 14a and boils to vaporize, and the latent heat of vaporization at this time can be used to effectively cool the heating element 21.

[0035] The working fluid preferably boils below the upper limit of the allowable temperature of the heating element 21. For example, if it is desired to maintain the heating element 21 at 60°C or below, a working fluid with a boiling point below 60°C is used. Furthermore, from the viewpoint of safety, a working fluid that is non-flammable or has low flammability is preferable, and one that is low in toxicity and further low in conductivity is also preferable. In this embodiment, the working fluid can be suitably refrigerant HCFO-1224yd manufactured by AGC, which is an organic solvent containing a single component, hydrochlorofluoroolefin (specifically, (Z)-1-chloro-2,3,3,3-tetrafluoropropene), has a low normal boiling point of 15°C, and is highly thermally and chemically stable.

[0036] The DC power supply 17 is preferably configured so that its output voltage can be switched in stages between 500V and 3000V. To generate an electric field using the DC power supply 17, it is sufficient to generate a potential difference between the electrode plate 15b of the slit electrode 15 and the fins 14a of the heat receiving body 14, and therefore, it is generally not necessary to distinguish and connect the positive (+) and negative (-) poles of the DC power supply 17.

[0037] However, in the present embodiment, the electrode plate 15b of the slit electrode 15 is prone to electric field concentration and has a high risk of discharge, so the entire slit electrode 15 is made of aluminum and the entire surface of the slit electrode 15 is anodized to form an electrically insulating layer. In this case, since there is a possibility that the oxide film of the anodized aluminum will peel off when a negative potential (negative pole (-)) is applied, the positive pole (+) of the DC power supply 17 is connected to the slit electrode 15, and the negative pole (-) is connected to the heat receiving body 14, and the negative pole (-) is also connected to the reference potential point (ground) of the cooling unit 11.

[0038] FIG. 7 illustrates the effect of reducing the thermal resistance due to the electric field generated by applying a DC voltage between the fin 14a of the heat receiving body 14 and the electrode plate 15b of the slit electrode 15. In FIG. 7, the electric field lines indicating the electric field are shown by dashed lines. In FIG. 7, the parts corresponding to those shown in FIG. 4 are denoted by the same reference numerals, and therefore detailed description thereof will be omitted.

[0039] The working fluid sent by the pump 41 passes through the working fluid passage 12c shown in FIG. 6 and flows through the roots of the plurality of fins 14a provided on the heat receiving body 14 as indicated by the symbol F in FIG. Former On the other hand, the root of the fin 14a Former Since heat from the heating element 21 is transmitted to the working fluid, the working fluid immediately boils and evaporates. Former A vaporization space is formed in the portion. Vapor B generated by boiling tends to stay between fins 14a and electrode plate 15b due to surface tension. However, due to the action of the electric field generated between fins 14a and electrode plate 15b, electrostatic pressure indicated by arrow P is generated at the gas-liquid interface between the vapor and liquid of the working fluid, i.e., on the surface of vapor B.

[0040] In this state, the pump 41 exerts a pressure on the working fluid, so that the vapor B of the working fluid flows through the roots of the fins 14a. Former The gas passes through the slits (working fluid passages 15c) of the slit electrode 15 from the vaporization space of the fin 14a and is transported together with the liquid working fluid into the second case 13 shown in FIG. Former The working fluid (liquid) is constantly drawn and supplied to the surface (boiling surface) facing the electrode plate 15b in this portion due to the action of the electric field, which promotes boiling and makes it possible to improve the heat transfer coefficient (h). The gas and liquid working fluid carried into the second case 13 are sent to the radiator 31 as a gas-liquid two-layer flow, where they are condensed and returned to the liquid working fluid.

[0041] The cooling effect of the cooling unit 11 on the heat-generating body 21 depends on the degree of reduction in thermal resistance (R) when heat is transferred from the boiling surface to the working fluid. The thermal resistance (R) can be calculated as the reciprocal of the heat transfer coefficient (h) due to the application of an electric field and the heat dissipation area (Aw) of the fins 14a of the heat receiving body 14. R=1 / hAw …… Equation 1

[0042] Therefore, according to the cooling device and cooling unit of the present invention, the increase in the heat dissipation area (Aw) due to the multiple fins 14a erected on the heat receiving body 14 and the improvement in the heat transfer coefficient (h) due to the increase in the area where the electric field is formed work synergistically, and the effect of reducing the thermal resistance (R) can be fully exerted. This makes it possible to achieve high cooling efficiency for the heat generating element 21, and to provide a cooling device and a cooling unit that enable the overall device to be made smaller.

[0043] The examples shown in FIGS. 8 to 10 show first to third embodiments of the cooling unit 11 described above, in which the heat transfer coefficient (h) is further considered. 8 to 10 show, in partial enlarged cross-sectional views, the relationship between a pair of fins 14a established on the heat receiving body 14 and the electrode plate 15b of the slit electrode 15 inserted therebetween. Also, the electric field lines are shown by dashed lines. The first embodiment shown in FIG. 8 has already been described based on FIGS. 3 and 4, and therefore FIG. 8 is used as an example to explain the technical issues regarding the heat transfer coefficient (h) in the first embodiment.

[0044] Regarding the effect of improving the heat transfer coefficient (h) by the first to third embodiments shown in Figures 8 to 10, it is necessary to understand that a dielectrophoretic force acts, which causes liquid to be attracted to and move in areas with a strong electric field, and vapor to be attracted to and move in areas with a weak electric field. 8, as already explained, the plurality of fins 14a formed on the heat receiving body 14 are formed as flat plates with the same thickness and arranged at equal intervals, and the plurality of electrode plates 15b formed on the slit electrode 15 are formed as flat plates with the same thickness and arranged at equal intervals. Therefore, the fins 14a and the electrode plates 15b inserted between the fins 14a in a non-contact state are arranged parallel to each other and at equal intervals.

[0045] According to the configuration shown in FIG. 8, the rising portion (near the corner of the base) of the fin 14a erected on the heat receiving body 14 is a region where the electric field is weaker than in other portions because the distance between the rising portion and the electrode plate 15b of the slit electrode 15 is large. According to this, a dielectrophoretic force acts on the vapor B of the boiling working fluid in the direction indicated by the white arrow, and therefore the vapor B tends to accumulate near the upper surface of the heat receiving body 14, including the rising portions of the fins 14a. For example, depending on the amount of working fluid introduced by the pump 41, there is a concern that dry-out may occur in the rising portions of the fins 14a. Therefore, when dryout actually occurs, the upper surface portion of the heat receiving body 14 indicated by the symbol D in FIG. 8 carries the risk of inhibiting the effect of improving the heat transfer coefficient (h) of the working fluid.

[0046] Next, in the second embodiment shown in FIG. 9, a plurality of fins 14a formed on the heat receiving body 14 are each Former The thickness of the fins 14a gradually decreases from the base to the other end, and the electrode plates 15b formed on the slit electrode 15 are formed as flat plates of equal thickness and are arranged at equal intervals. Therefore, the distance between each fin 14a and each electrode plate 15b inserted between the fins 14a in a non-contact state gradually increases from the base of each fin 14a to the other end.

[0047] With this configuration, in the region where the fins 14a and the electrode plate 15b face each other, the distance between them increases toward the top, and the electric field in this upper region is distributed so as to transition from strong to weak. Therefore, a dielectrophoretic force indicated by the upward white arrow acts on the boiling vapor B of the working fluid, which promotes the discharge of the vapor B and improves the heat transfer coefficient (h) of the working fluid.

[0048] On the other hand, in the second embodiment shown in Fig. 9, the rising portion of the fin 14a provided on the heat receiving body 14, i.e., the portion indicated by the symbol C, is far from the electrode plate 15b of the slit electrode 15, and the electric field is weaker in this portion than in other portions, as in the first embodiment shown in Fig. 8. Therefore, the dielectrophoretic force acts on the vapor B of the boiling working fluid in the direction indicated by the white arrow, and the discharge effect of the vapor B is low, and the effect of improving the heat transfer coefficient (h) by the working fluid is not sufficient.

[0049] In the third embodiment shown in FIG. 10, a plurality of fins 14a formed on the heat receiving body 14 are each Former The thickness of the fins 14a gradually decreases from the base to the other end, and the electrode plates 15b formed on the slit electrode 15 are arranged at equal intervals. The electrode plates 15b are formed in the shape of flat plates with the same thickness and arranged at equal intervals. Therefore, the distance between each fin 14a and each electrode plate 15b inserted between the fins 14a in a non-contact state gradually increases from the base of each fin 14a to the other end (upper portion). Former Between the parts, there is a circular groove R Former A configuration formed along the section is employed.

[0050] According to this configuration, in the region where the fin 14a and the electrode plate 15b face each other, the distance between them increases toward the top, so that, as in the second embodiment shown in Figure 9, the discharge effect of steam B is promoted, and the heat transfer coefficient (h) of the working fluid can be improved. In addition, the roots of the adjacent fins 14a Former Between the parts, there is a circular groove R Former Since the fins 14a are formed along the grooves R, the distance between the heat receiving body 14 and the electrode plate 15b at the bottom is inevitably close. As a result, the electric field near the arc-shaped grooves R is stronger and has a more uniform electric field distribution than in the upper region where the fins 14a and the electrode plate 15b face each other.

[0051] Therefore, dielectrophoretic force acts in the upward direction, as shown by the white arrow, on vapor B of the working fluid generated near the arc-shaped recessed groove R, achieving an efficient discharge effect of vapor B. This makes it possible to further improve the heat transfer coefficient (h) of the working fluid, and achieves the effect of reducing high thermal resistance (R).

[0052] 8 to 10 each have the advantages and disadvantages described above when comparing the effect of improving the heat transfer coefficient (h). However, in the cooling unit 11 of each of the first to third embodiments, compared to the cooling unit disclosed in Patent Document 1 cited as a prior art example, the effect of improving the heat transfer coefficient (h) can be greatly improved by increasing the heat dissipation area (Aw) and the area where the electric field is formed. As a result, as described above, it is possible to reduce the size of the entire device and provide a cooling device and a cooling unit that have high cooling efficiency for a heat generating body.

[0053] In the embodiment described above, the outer shell of the cooling unit 11 is constructed by stacking the second case 13 on the first case 12, but these first case 12 and second case 13 can also be integrally molded. [Industrial Applicability]

[0054] The cooling device and cooling unit according to the present invention have high cooling efficiency and can be suitably used to cool electronic components with high heat density, such as laser diodes used as light sources for large projectors as exemplified at the beginning, power semiconductors used in driving control of electric vehicles, or highly integrated microprocessing units (MPUs) used in computers. [Explanation of symbols]

[0055] 10 Cooling device 11 Cooling unit 12 First Case 12a spacer 12b Working fluid inlet 12c Working fluid passage 13 Second Case 13a Working fluid outlet 14 Heat receiver 14a Fins 15 slit electrodes 15a Support Frame 15b Electrode plate 15c Slit (working fluid passage) 15d Grip 17 DC power supply 21 Heating element 31 Heat radiator (heat exchanger) 32 fans 41 Pump 51 Pipe parts B Working fluid vapor R arc groove

Claims

1. a cooling unit that receives heat from the heating element and changes the phase of at least a part of the working fluid from a liquid phase to a gas phase, thereby cooling the heating element; a radiator in the cooling unit that receives and cools the working fluid that has undergone a phase change, thereby liquefying and condensing the working fluid; a pump that sends the working fluid liquefied by the radiator to the cooling unit; A cooling device that circulates a working fluid between the cooling unit and a radiator, The cooling unit includes a metal heat receiving body that receives heat from the heat generating body on one side and has a plurality of fins that are erected on the other side, thereby vaporizing the working fluid that is supplied to the base of each erected fin; a metal slit electrode having a plurality of electrode plates inserted between a plurality of fins formed on the heat receiving body in a non-contact state, and a base end of each of the electrode plates being opened in a slit shape to form a passage through which the working fluid passes; a DC power supply that applies a DC voltage between the heat receiving body and the slit electrode to generate an electric field between the fins of the heat receiving body and the electrode plates of the slit electrode that are alternately adjacent to each other; A cooling device comprising:

2. A cooling unit that receives heat from a heat generating element and cools the heat generating element by causing at least a part of a working fluid to change phase from a liquid phase to a gas phase, The cooling unit includes a metal heat receiving body that receives heat from the heat generating body on one side and has a plurality of fins that are erected on the other side, thereby vaporizing the working fluid that is supplied to the base of each erected fin; a metal slit electrode having a plurality of electrode plates inserted between a plurality of fins formed on the heat receiving body in a non-contact state, and a base end of each of the electrode plates being opened in a slit shape to form a passage through which the working fluid passes; a first case that holds the heat receiving body and the slit electrode, the first surface of the heat receiving body being a bottom surface, and that has an inlet for the working fluid; a second case that covers the slit electrode, is superposed on the first case, or is integrally formed with the first case, and forms an outlet for the working fluid; a DC power supply that applies a DC voltage between the heat receiving body and the slit electrode to generate an electric field between the fins of the heat receiving body and the electrode plates of the slit electrode that are alternately adjacent to each other; A cooling unit comprising:

3. The plurality of fins formed on the heat receiving body are formed into flat plate shapes with the same thickness and are arranged at equal intervals, and the plurality of electrode plates formed on the slit electrode are formed into flat plate shapes with the same thickness and are arranged at equal intervals, 3. The cooling unit according to claim 2, wherein the fins and the electrode plates inserted between the fins in a non-contact state are arranged parallel to each other and at equal intervals.

4. The plurality of fins formed on the heat receiving body are arranged at equal intervals with their thickness gradually decreasing from the base portion to the other end, and the plurality of electrode plates formed on the slit electrode are formed in the shape of flat plates with the same thickness and arranged at equal intervals, 3. The cooling unit according to claim 2, wherein the distance between each fin and each electrode plate inserted between the fins in a non-contact state gradually increases from the base of each fin toward the other end.

5. The plurality of fins formed on the heat receiving body are arranged at equal intervals with their thickness gradually decreasing from the base portion to the other end, and the plurality of electrode plates formed on the slit electrode are formed in the shape of flat plates with the same thickness and arranged at equal intervals, a distance between each of the fins and each of the electrode plates inserted between the fins in a non-contact state is gradually increased from a base portion of each of the fins toward the other end portion thereof; 3. The cooling unit according to claim 2, wherein a groove having an arcuate shape is formed along the base portions between adjacent fins.

6. 3. The cooling unit according to claim 2, wherein the first case has a conducting passage formed therein for guiding the working fluid from the inlet for the working fluid to both ends of the base portions of a plurality of fins erected on the heat receiving body.

7. The slit electrode is made of aluminum material, and an insulating layer made of alumite is formed on the entire surface of the slit electrode.

7. The cooling unit according to claim 2, wherein a positive voltage of the DC power supply is applied to an electrode plate of the slit electrode, and a negative voltage is applied to a fin of the heat receiving body.

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