JP2018204882A - Ebullition cooler - Google Patents

Abstract

To provide an ebullition cooler including excellent cooling performance, and capable of sufficiently supporting cooling of an inverter in recent electric equipment, electric car, or hybrid vehicle.SOLUTION: A heat transfer wall part 22 corresponding to a position of a heating body 9 of a heat receiving part 2 comprises: an uneven surface 5 having a plurality of recesses 50 extending along an inner wall surface of the heat receiving part 2; and a metal porous body 6 attached to the uneven surface 5 so that at least a part of the recess 50 of the uneven surface 5 is overlapped so as to open toward the internal space, wherein the metal porous body 6 has a plurality of open holes 60 extending in a specific direction formed, one opening 60a of the open hole 60 faces the uneven surface 5, and the other opening 60b is attached so as to open toward the internal space.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a boiling cooling device using a refrigerant.

  A boiling cooling device is a device that cools a heating element by using a phase change from a liquid of a refrigerant to a gas. Specifically, the boiling cooling device includes a heat receiving portion and a heat radiating portion having internal spaces communicating with each other. It is known that a refrigerant is enclosed and a heating element is attached to the outer wall surface of the heat receiving part, and the refrigerant stored in the liquid phase inside the heat receiving part transports heat to the heat radiating part as latent heat by phase change. (For example, refer to Patent Document 1). The phase change of the refrigerant is caused by boiling / evaporation in which foaming occurs mainly using the inner surface corresponding to the mounting position of the heating element among the inner surfaces of the heat receiving portion in contact with the refrigerant. This boiling / evaporation occurs efficiently on the heat transfer surface (heat transfer wall), thereby improving the heat transfer rate, that is, the cooling efficiency of the heating element.

It has also been proposed to promote boiling / evaporation by forming a large number of holes in the heat transfer wall and making it a rough surface (see, for example, Patent Documents 2 and 3). However, in recent years, with the miniaturization and high performance of electronic devices, the heat generation density of electronic devices has rapidly increased, and a device having higher cooling efficiency has been demanded. For example, the inverter of a current hybrid vehicle has a maximum heat generation density exceeding 300 W / cm ² and adopts a cooling method by forced flow using a circulation pump. However, in order to reduce the power consumption of a hybrid vehicle or an electric vehicle, power consumption other than that of the motor is not desirable, and if it can be handled by a boiling cooling device, it can contribute to lowering the power consumption.

JP 2010-196912 A JP 2012-13396 A JP 2017-15269 A

  Therefore, in view of the above-described situation, the present invention intends to provide a boiling cooling device that has excellent cooling performance and can sufficiently cope with cooling of inverters of recent electronic devices, electric vehicles, or hybrid vehicles. There is in point to do.

The present invention includes the following inventions.
(1) A heat receiving portion and a heat radiating portion each having an internal space communicating with each other, a refrigerant is enclosed inside, and a heating element is attached to the outer wall surface of the heat receiving portion, and stored in a liquid phase state inside the heat receiving portion. The refrigerant is a boiling cooling device that transports heat to the heat radiating portion as latent heat due to phase change, and is arranged along the inner wall surface of the heat receiving portion on the heat transfer wall portion corresponding to the position of the heating element of the heat receiving portion. An uneven surface having a plurality of recesses extending, and a porous metal body attached to the uneven surface so that at least a part of the recesses of the uneven surface is open to the internal space. A plurality of through-holes extending in the direction are formed, and a metal porous body is provided so that one opening of the through-hole faces the uneven surface and the other opening is opened to the internal space. Boiling cooler characterized by.

  (2) The said uneven surface is comprised from the said several groove | channel extended in parallel or a grid | lattice form, and the said metal porous body is attached in the state by which the both ends of each groove | channel were open | released to the said internal space. (1) The boiling cooling device according to the above.

  (3) The metal porous body is formed by cutting a lotus-type porous metal molded body having a plurality of pores extending in one direction formed by a metal solidification method in a direction intersecting with the direction in which the pores extend. The boiling cooling device according to (1), wherein the through hole is the pore divided by the cutting.

  According to the boiling cooling apparatus according to the present invention as described above, by the dimensional design of the metal porous body and the concave and convex surfaces, the boiling from the metal porous body, acceleration of evaporation, or from the concave and convex surfaces of the concave and convex surfaces. Either boiling or evaporation will occur. When boiling and evaporation from the metal porous body are promoted, the vapor is discharged from the upper part of the metal porous body (or the open part of the groove), and the concave and convex surfaces (or the metal porous body) are formed. Thus, the refrigerant liquid is spontaneously supplied to the metal porous body, and boiling and evaporation from the metal porous body are continuously promoted. In addition, when boiling and evaporation from the groove are promoted, the vapor is discharged from the opening (or the metal porous body) of the groove and the through hole (or the groove opening) of the metal porous body. The cooling liquid is spontaneously supplied to the concave line through the part), and boiling and evaporation from the concave line are continuously promoted.

Thus, in any case, boiling / evaporation in the heat transfer wall is promoted more than before, and the cooling performance is remarkably improved. It has been confirmed that the specific cooling performance greatly exceeded 110 W / cm ² , which is the boiling cooling limit of the atmospheric pressure environment, and achieved about 280 W / cm ² . Therefore, it is possible to provide a boiling cooling device that can sufficiently cope with cooling of an electronic device in recent years and an inverter of an electric vehicle or a hybrid vehicle. In particular, by supporting inverter cooling, it can be provided as a self-supporting ultra-compact cooling device that eliminates conventional cooling circulation pumps and piping systems, improving and reducing the driving mileage of next-generation electric vehicles and hybrid vehicles. It can greatly contribute to electricity consumption.

  Further, the uneven surface is constituted by a plurality of the concave ridges extending in parallel or in a lattice shape, and the metal porous body is attached in a state where both end portions of the concave ridges are open to the internal space. Then, by opening both ends of the groove, the refrigerant is supplied more smoothly (or the steam is discharged smoothly), and the cooling efficiency is further improved.

  Further, the metal porous body is formed by cutting a lotus-type porous metal molded body having a plurality of pores extending in one direction formed by a metal solidification method in a direction crossing the direction in which the pores extend, In the case where the through hole is the pore divided by the cutting, it can be manufactured at a lower cost and more easily than machining each through hole by drilling or the like. Further, in such a metal porous body, a skin region in which no pores are present is formed at the peripheral end portion by the mold inner wall used for the molding. Accordingly, the porous bodies can be easily joined to each other in a state where the joining area is ensured at the end faces, and thus a single porous body can be configured by joining a plurality of the shaped bodies at the end faces in this way. This makes it easy to prevent a decrease in heat transfer at the joint.

Sectional drawing seen in the direction where the concave strip shows the boiling cooling device concerning typical embodiment of this invention. Sectional drawing of a boiling cooling device similarly seen in the direction orthogonal to the direction of FIG. (A), (b) is explanatory drawing which shows the effect | action in the heat-transfer wall part of a boiling cooling device similarly. Explanatory drawing which shows a modification. (A), (b) is explanatory drawing which shows an experimental apparatus. The graph which shows the boiling curve of an experimental result.

  Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  As shown in FIG. 1, the boiling cooling device 1 of the present invention includes a heat receiving portion 2 and a heat radiating portion 3 having internal spaces communicating with each other, and a refrigerant 4 is enclosed therein and an outer wall surface 21 of the heat receiving portion 2. The heat generating element 9 is attached to the refrigerant 4, and the refrigerant 4 stored in a liquid phase state inside the heat receiving part 2 transports heat to the heat radiating part 3 as latent heat by phase change.

  In particular, the heat transfer wall portion 22 corresponding to the position of the heating element 9 of the heat receiving portion 2 has an uneven surface 5 having a plurality of recesses 50 extending along the inner wall surface of the heat receiving portion 2, and the uneven surface 5. The metal porous body 6 is attached so that at least a part of the concave stripe 50 of the uneven surface 5 is opened to the internal space, and a plurality of through holes 60 extending in one direction are formed, One opening 60a of the through hole 60 faces the uneven surface 5, and the metal opening 6 is attached so that the other opening 60b is opened to the internal space.

  Although the heat receiving part 2 and the heat radiating part 3 are comprised from the one storage container 7, as long as it was provided with the internal space connected mutually, even if each container which comprises each part was connected by piping etc. Well, in that case, the flow path through which the refrigerant vaporized from the heat receiving section 2 toward the heat radiating section 3 and the flow path through which the refrigerant returned to the liquid at the heat radiating section 3 flows back to the heat receiving section 2 are communicated. In addition, the communication form of a conventionally known boiling cooling device can be widely applied.

  In this example, the heat dissipating unit 3 is provided with a condensing pipe 8 through which cooling water flows, and the vaporized refrigerant comes into contact with the condensing pipe 8 to remove heat and liquefy. However, the present invention is not limited to such a heat dissipation mode, and a conventionally known boiling cooling device, such as a device that dissipates heat from the refrigerant through the inner wall by providing a heat dissipating fin that dissipates heat by blowing or the like on the outer wall of the heat dissipating part. The heat radiation form can be widely adopted. Also for the refrigerant 4, conventionally known refrigerants such as water, alcohol, and fluorocarbon refrigerant can be appropriately used depending on the material of the container of the heat receiving unit 2 and the heat radiating unit 3.

  The concave / convex surface 5 constituting the heat transfer wall portion 22 together with the metal porous body 6 is configured by directly forming the concave stripe 50 on the inner surface (bottom surface) of the bottom wall of the container made of a highly heat conductive material in this example. However, it may be configured as a heat transfer member made of a highly heat conductive material separately from the container. The concavo-convex surface 5 of the concavo-convex surface 5 is composed of a plurality of recesses 50 extending in parallel.

  The metallic porous body 6 is layered on the uneven surface 5 and is set to a size smaller than the uneven surface 5 so that both end portions of each concave strip 50 are opened to the internal space of the storage container 7. Has been. Through the open part 51 opened to the internal space at the end of the concave line 50, the refrigerant is supplied more smoothly or the steam is discharged smoothly. In this example, the concave stripes 50 that are independent from each other are formed in parallel at a predetermined interval. However, the present invention is not limited to this.

  Depending on the dimensional design of the metal porous body 6 and the recess 50 of the concavo-convex surface 5, either boiling or evaporation from the metal porous body 6 or promotion of boiling or evaporation occurs. The generated steam is discharged from the through-hole opening 60b in the upper part of the metal porous body 6 as shown by the arrow in FIG. 3A, or the groove is opened as shown in FIG. 3B. Discharged from the unit 51. And when discharged | emitted from the through-hole opening 60b, the liquid of the refrigerant | coolant 4 is spontaneously supplied to the lower surface side of the metal porous body 6 through the groove 50 from the open part 51 of the groove 50, and boiling and evaporation continue. When the steam is discharged from the opening 51 of the concave stripe, the liquid of the refrigerant 4 spontaneously enters the inside of the metal porous body 6 through the through-hole opening 60b in the upper part of the metal porous body 6. It is supplied and boiling and evaporation are continuously promoted.

  Although only one metal porous body 6 is provided so as to cover all other parts in a state where both ends of the groove 50 are released with respect to the uneven surface 5, as shown in FIG. A plurality of them may be arranged side by side. Thereby, the open part of the groove 50 can be provided not only at both ends but also in the middle, and the cooling efficiency can be further increased.

  As a material used for a metal porous body, a metal material having good heat conductivity, such as aluminum, iron, copper, and the like used for piping and fins of conventional heat exchangers can be widely applied. A through hole extending in one direction can be formed by a known method such as drilling or laser processing. In this example, a metal porous body having a through hole extends in one direction formed by a metal solidification method. The porous porous metal molded body having a plurality of pores is made of a porous material obtained by cutting in a direction crossing the direction in which the pores extend.

  Such a Lotus-type porous metal molded body can be formed by a known method such as a high pressure gas method (for example, a method disclosed in Japanese Patent No. 423581) or a thermal decomposition method. it can. In this way, a skin region free from the pores is formed by the inner wall of the mold used for molding at the peripheral end portion of the metal porous body 6 made of the porous material cut out from the lotus-type porous metal molded body. The through hole 60 is the pore divided by the cutting.

  Thus, by using the porous material cut out from the lotus-type porous metal molded body, the metal porous body 6 having a large number of through-holes extending in one direction can be easily obtained at low cost, and the skin around it can be obtained. Since the region is formed, when the metal porous body 6 is constructed by joining the end faces of a plurality of porous materials by brazing or the like, the joining strength can be sufficiently maintained and the brazing operation is also easy. And heat conduction between each other can be maintained well.

  In the metal porous body 6 cut out from the lotus-type porous metal molded body, there are bottomed holes that do not penetrate other than the through holes 60. Such a bottomed hole also has an effect of increasing the surface area. There is an effect of promoting the evaporation of the refrigerant. The shape of the metal porous body 6 is a flat plate shape having a relatively small dimension in the direction in which the through hole 60 extends, but may be configured in various other shapes.

  Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and can of course be implemented in various forms without departing from the gist of the present invention.

  Next, the heat transfer wall portion according to the present invention in which the metal porous body is placed on the uneven surface (Example 1), the heat transfer wall portion in which the metal porous body is placed on a flat surface where no concave stripe exists (comparison) Example 1), the result of conducting a boiling cooling experiment for confirming the cooling effect on the heat transfer wall portion (Comparative Example 2) in which the metal porous body is omitted from Comparative Example 1 and only the flat surface without the concave stripes is present. Will be described.

(Experimental device)
The experimental apparatus is shown in FIG. In the experimental apparatus, a copper block was attached to the bottom surface of a boiling vessel having an inner diameter of 63 mm so that the upper surface was exposed to the inner space of the vessel as a cooling surface (10 mm square). On the bottom surface of the copper block, a heating block equipped with a heater was attached in contact. On the upper surface of the boiling vessel, a condenser (heat exchanger) was provided for heat-exchanging the refrigerant vapor, which became gas vapor, with the cooling water to condense and liquefy it. The refrigerant in the boiling vessel was water (distilled water), and was maintained at a saturation temperature (100 ° C.) by a heater wound around the boiling vessel. FIG. 5 (b) is an enlarged view of the copper block constituting the cooling surface, and thermocouples were respectively installed at positions 3 mm, 7 mm, 11 mm, and 15 mm away from the cooling surface.

(Electric heating wall)
In Example 1, a plurality of parallel concave stripes were directly formed on the cooling surface to form an uneven surface, and a metal porous body was placed thereon. The concave stripes had a depth of 0.4 mm, a width of 0.4 mm, and a pitch of 1 mm. The metal porous body was a copper porous body cut out from the lotus-type porous metal molded body, and was a 10 mm square and 2 mm thick plate material. A number of through-holes were provided in the thickness direction, the average pore (through-hole) diameter was 0.26 mm, and the number of pores was 355. The end surface of the concave line was opened to the inside of the container. In Comparative Example 1, the metal porous body was attached to the flat cooling surface as described above, and in Comparative Example 2, only the flat cooling surface was used.

(experimental method)
Using the above experimental apparatus, the heat transfer wall portions of Example 1 and Comparative Examples 1 and 2 were configured on the cooling surface, and in each case, the heating block was heated with a heater and the condenser was operated to transfer power. While the hot wall portion was boiled and cooled with a refrigerant, the temperature of each portion was measured with the thermocouples installed at four locations in the copper block. And the heat flux in each case was computed from the temperature measurement result using the well-known Fourier rule, and the boiling curve was obtained. In Example 1, experiments (Run 1 and Run 2) were performed twice in order to confirm reproducibility. FIG. 6 is a boiling curve obtained as a result of the experiment for each case.

As can be seen from the results of FIG. 6, according to the cooling wall portion of Example 1 according to the present invention, the maximum performance increases by about 140 W / cm ² compared to the case of the flat surface (Comparative Example 2), and is flat. Even when compared with the case where a metal porous body is attached to the surface (Comparative Example 1), the maximum performance is increased by about 50 W / cm ² and has excellent cooling performance. Although the maximum performance of Example 1 was 276 W / cm ^2, it was caused by the heating limit during the experiment, and the boiling cooling limit could be more than this.

DESCRIPTION OF SYMBOLS 1 Boiling cooler 2 Heat receiving part 3 Heat radiating part 4 Refrigerant 5 Uneven surface 6 Metal porous body 7 Storage container 8 Condensation pipe 9 Heat generating body 21 Outer wall surface 22 Heat transfer wall part 50 Concave 51 Open part 60 Through-hole 60a, 60b Opening

Claims (3)

The refrigerant having a heat receiving portion and a heat radiating portion having an internal space communicating with each other, in which a refrigerant is enclosed, a heating element is attached to an outer wall surface of the heat receiving portion, and stored in a liquid phase inside the heat receiving portion Is a boiling cooling device that transports heat to the heat dissipating part as latent heat by phase change,
In the heat transfer wall portion corresponding to the position of the heating element of the heat receiving portion,
An irregular surface having a plurality of concave stripes extending along the inner wall surface of the heat receiving portion;
It is a metallic porous body that is attached so as to be overlapped with at least a part of the concave and convex surfaces of the concave and convex surface in an open state in the internal space, and a plurality of through holes extending in one direction are formed, A metal porous body attached so that one opening of the through hole faces the uneven surface and the other opening is opened to the internal space;
A boiling cooling device characterized by comprising:   2. The metal porous body is attached in a state in which the uneven surface is composed of a plurality of the concave stripes extending in a parallel or lattice shape, and both end portions of the concave stripes are open to the internal space. The boiling cooling device as described.   The metal porous body is formed by cutting a lotus-type porous metal molded body having a plurality of pores extending in one direction formed by a metal solidification method in a direction crossing the direction in which the pores extend. The boiling cooling device according to claim 1 or 2, wherein the hole is the pore divided by the cutting.

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