JP2024036773A - Method for manufacturing a boiling cooling device and a heat transfer part applied thereto - Google Patents

Abstract

An object of the present invention is to provide a boiling cooling device that can improve cooling performance. [Solution] The heat transfer part 3 is provided with a heat transfer part 3 that promotes heat transfer from an electronic device 2 to a refrigerant liquid 11, and the heat transfer part 3 is made of a porous material having a plurality of pores 31 and 32 with different diameters. Therefore, in the frequency distribution of the diameters of the pores 31 and 32 formed in the heat transfer part 3, at least two different peak values are formed, and the smaller of the two different peak values is called the small peak. When the larger peak value is taken as the large peak value, the small pores 31 forming the small peak value form a liquid phase refrigerant passage 310 that causes capillary action, forming the large peak value. The large pores 32 form a gas phase refrigerant passage 320 through which the boiled refrigerant liquid flows out of the heat transfer section. [Selection diagram] Figure 2

Description

The present invention relates to an evaporative cooling device that cools a heat generating element such as an electronic device with a refrigerant liquid, and a method for manufacturing a heat transfer unit applied thereto.

Patent Document 1 discloses a boiling cooling device having a heat transfer promoting section formed of a porous metal body. In the boiling cooling device described in Patent Document 1, a foam originating layer having a larger porosity and pore diameter than other parts is provided on the surface layer of the heat transfer promoting part. The surface of the metal porous body, that is, the surface of the foaming origin layer, serves as a bubble release surface.

Further, in the boiling cooling device described in Patent Document 1, a liquid phase refrigerant passage is provided inside the metal porous body to guide the liquid phase refrigerant to the heating element side by capillary action. The liquid phase refrigerant passage is formed from the upper end surface of the porous metal body toward the heating element.

Japanese Patent Application Publication No. 2015-197245

However, in the boiling cooling device of Patent Document 1, when the liquid phase refrigerant in the liquid phase refrigerant passage boils, the boiled gas phase refrigerant (i.e., boiling vapor) is transferred to the liquid phase refrigerant passage with a small porosity and pore diameter. The air bubbles are discharged through the air bubble release surface. For this reason, the pressure loss when the vapor phase refrigerant is discharged from the liquid phase refrigerant passage is large, and the vapor phase refrigerant is difficult to be discharged. This may deteriorate cooling performance.

In view of the above-mentioned points, an object of the present invention is to provide a boiling cooling device capable of improving cooling performance and a method of manufacturing a heat transfer section applied thereto.

In order to achieve the above object, the boiling cooling device according to claim 1 includes a heat transfer part (3) that promotes heat transfer from the object to be cooled (2) to the refrigerant liquid (11),
The heat transfer part is made of a porous material having a plurality of pores (31, 32) with different diameters,
In the frequency distribution of the diameter of the pores formed in the heat transfer part, at least two different peak values are formed,
Among two different peak values, when the smaller peak value is taken as the small peak value and the larger peak value is taken as the large peak value,
The pores (31) forming a small peak value form liquid phase refrigerant passages (310) that cause capillary action,
The pores (32) forming the large peak value form gas phase refrigerant passages (320) through which the boiled refrigerant liquid flows out of the heat transfer section.

According to this, the liquid-phase refrigerant liquid (11) is supplied into the heat transfer part (3) through the pores (31) forming a small peak value to form a boiling point of the refrigerant liquid (11). be able to. The pores (32) forming a large peak value allow the boiled refrigerant liquid (11) to flow out of the heat transfer section (3). At this time, the diameter of the pores (32) forming the gas phase refrigerant passage (320), that is, the pores (32) forming the large peak value, is larger than the diameter of the pore (31) forming the small peak value. Pressure loss when discharging the boiled refrigerant liquid (11) to the outside of the heat transfer section (3) can be reduced. As a result, it becomes possible to improve cooling performance.

Further, the method for manufacturing a heat transfer portion according to claim 4 is applied to a boiling cooling device, and is a method for manufacturing a heat transfer portion that transfers heat of an object to be cooled (2) to a refrigerant liquid (11). ,
a sintering step of sintering metal particles and spacer particles of at least two different diameters;
and a spacer removal step of dissolving and removing spacer particles.

According to this, the heat transfer part (3) having at least two types of pores (31, 32) with different diameters can be manufactured with high precision. By applying the heat transfer part (3) manufactured by this method to a boiling cooling device, the pressure loss when discharging the boiled refrigerant liquid (11) to the outside of the heat transfer part (3) can be reduced. I can do it. As a result, it becomes possible to improve cooling performance.

Note that the reference numerals in parentheses of each means described in this column and the claims indicate correspondence with specific means described in the embodiment described later.

BRIEF DESCRIPTION OF THE DRAWINGS It is a conceptual diagram which shows the whole structure of the boiling cooling device based on 1st Embodiment. It is a sectional view showing a heat transfer part in a 1st embodiment. It is a micrograph which shows the heat transfer part in 1st Embodiment. It is a micrograph showing the heat transfer part in a comparative example. It is a sectional view showing a heat transfer part in a 2nd embodiment. It is a top view which shows the heat transfer part in 2nd Embodiment. It is a conceptual diagram which shows the whole structure of the boiling cooling device based on 3rd Embodiment. It is a top view which shows the heat transfer part in other embodiments. It is a top view which shows the heat transfer part in other embodiments. It is a top view which shows the heat transfer part in other embodiments.

Embodiments of the present invention will be described below based on the drawings. Note that in each of the following embodiments, parts that are the same or equivalent to each other are given the same reference numerals in the drawings.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described using the drawings. In FIG. 1, the vertical direction of the paper surface is the direction of gravity. In FIG. 2, black arrows indicate the flow of the refrigerant liquid, white arrows indicate the flow of the gas phase refrigerant, and dotted hatched areas indicate the gas phase refrigerant (that is, bubbles) generated by boiling.

As shown in FIG. 1, the boiling cooling device 1 of this embodiment is provided with a cooling tank 10 for cooling an electronic device 2, which is an object to be cooled. The electronic device 2 is a heat generating element that generates heat during operation and requires cooling. As the electronic device 2, for example, an electronic board on which a heating element is mounted, an inverter, etc. can be used.

The cooling tank 10 is a container-shaped member in which a refrigerant liquid 11 for cooling the electronic device 2 is stored. The refrigerant liquid 11 may be any fluid that changes its vapor phase due to heat generated by the electronic device 2, and for example, water or an insulating fluid may be used. As the insulating fluid, for example, a fluorine-based inert liquid can be used.

The cooling tank 10 of this embodiment has a liquid-tight structure that does not communicate with the atmosphere. Since the pressure inside the cooling tank 10 fluctuates due to phase changes of the refrigerant liquid 11, the cooling tank 10 has a pressure-resistant structure.

In this embodiment, the electronic device 2 is provided outside the cooling tank 10. In this case, since heat exchange is performed between the electronic device 2 and the refrigerant liquid 11 via the wall surface of the cooling tank 10, the electronic device 2 is arranged so as to be in contact with the wall surface of the cooling tank 10. In the example shown in FIG. 1, the electronic device 2 is arranged so as to be in contact with the lower surface of the cooling tank 10. That is, the electronic device 2 is arranged so as to be in contact with the outer surface of the lower wall of the cooling tank 10 .

A heat conductive sheet (not shown) or the like may be interposed between the electronic device 2 and the wall surface of the cooling tank 10. The thermally conductive sheet can improve the adhesion between the electronic device 2 and the cooling tank 10 and improve the heat transfer coefficient between the electronic device 2 and the cooling tank 10.

The cooling tank 10 can be made of, for example, a metal material or a resin material. In this embodiment, the cooling tank 10 is made of a metal material with high thermal conductivity. When the electronic device 2 is provided outside the cooling tank 10 as in this embodiment, by using a metal material with high thermal conductivity as the cooling tank 10, the electronic device 2 can be connected to the cooling tank 10 through the wall surface. Heat exchange efficiency with the refrigerant liquid 11 can be improved.

The boiling temperature of the refrigerant liquid 11 is lower than the allowable temperature limit of the electronic device 2. That is, the boiling temperature of the refrigerant liquid 11 is lower than the temperature of the electronic device 2 when generating a high amount of heat. Therefore, the refrigerant liquid 11 can be boiled by the heat generated by the electronic device 2, and boiling cooling is performed in which the refrigerant liquid 11 boils in the cooling tank 10 and absorbs heat from the electronic device 2.

The cooling tank 10 has a heat transfer surface 13 that transfers heat from the electronic device 2 to the refrigerant liquid 11. In the present embodiment, the heat transfer surface 13 is provided on a surface of the wall of the cooling tank 10 that is opposite to the surface that contacts the electronic device 2 . That is, the heat transfer surface 13 is provided on the inner surface of the lower wall of the cooling tank 10 .

As shown in FIGS. 1 and 2, the heat transfer surface 13 is provided with a heat transfer section 3 that transfers heat from the electronic device 2 to the refrigerant liquid 11. The heat transfer section 3 is a heat transfer promoting section that promotes heat transfer from the electronic device 2 to the refrigerant liquid 11. The heat transfer section 3 is made of a material with excellent thermal conductivity. In this embodiment, the heat transfer section 3 is made of metal such as aluminum or copper.

As shown in FIG. 2, the heat transfer section 3 is made of a porous material having a plurality of pores 31 and 32 with different diameters. In this specification, the diameter of the pores 31 and 32 means the equivalent circle diameter of the pores 31 and 32.

Note that the diameters of the pores 31 and 32 in the heat transfer section 3 can be determined by a method such as image processing of a cross-sectional image obtained by cross-sectional observation. A common method for cross-sectional observation is to cut the sample to open the cross-section and observe it with an optical microscope or scanning electron microscope. Commercially available image processing software can be used. Alternatively, the diameters of the pores 31 and 32 may be measured and calculated manually from a cross-sectional photograph. If the cross section is an ellipse, the square root of the product of the major axis and minor axis should be treated as the diameter. In this embodiment, observations were made at multiple locations in the thickness direction of the heat transfer portion 3.

In the frequency distribution of the diameters of the pores 31 and 32 formed in the heat transfer portion 3 (hereinafter referred to as pore diameter frequency distribution), at least two different peak values are formed. In this specification, the frequency distribution refers to the distribution of data belonging to each class when the diameters of the plurality of pores 31 and 32 formed in the heat transfer section 3 are divided into several classes (i.e., sections). , and includes a histogram that graphs the frequency distribution. In the pore size frequency distribution, each class may be 20 μm, for example.

At least two different peak values are formed in the pore size frequency distribution. In the pore diameter frequency distribution of this embodiment, two different peak values are formed. Here, of the two different peak values, the smaller peak value is referred to as a small peak value, and the larger peak value is referred to as a large peak value.

Among the plurality of pores 31 and 32, the pore 31 that forms a small peak value (hereinafter referred to as small pore 31) forms a liquid phase refrigerant passage 310 that causes capillarity. Among the plurality of pores 31 and 32, the pore 32 that forms a large peak value (hereinafter referred to as large pore 32) is a gas phase refrigerant passage 320 through which the boiled refrigerant liquid 11 flows out of the heat transfer section 3. is formed.

In this embodiment, in the pore diameter frequency distribution, the small peak value is the diameter of the maximum value that causes capillarity to occur in the refrigerant liquid 11. The large peak value is five times or more the small peak value.

Next, the operation of the evaporative cooling device 1 of this embodiment having the above configuration will be explained.

Inside the cooling tank 10, the refrigerant liquid 11 boils due to the heat generated by the electronic device 2, and a vapor phase refrigerant is generated. In this embodiment, since the electronic device 2 and the refrigerant liquid 11 exchange heat via the heat transfer surface 13 of the cooling tank 10 and the heat transfer part 3, the refrigerant liquid 11 in contact with the heat transfer part 3 boils.

More specifically, the refrigerant liquid 11 is sucked into the small pores 31 of the heat transfer section 3 from the outermost surface of the heat transfer section 3 by capillary force. Then, the refrigerant liquid 11 within the small pores 31 is boiled to generate a gas phase refrigerant. The gas phase refrigerant generated by boiling flows out as bubbles to the large pores 32 scattered around the small pores 31 and is released from the outermost surface of the heat transfer section 3 .

Next, a method of manufacturing the heat transfer section 3 applied to the evaporative cooling device 1 of this embodiment will be explained. The heat transfer section 3 is formed by a sintered spacer method. Specifically, the method for manufacturing the heat transfer section 3 includes a sintering process and a spacer removal process.

First, a sintering step is performed in which metal particles and at least two types of spacer particles with different diameters are mixed and sintered. Hereinafter, among the two types of spacer particles having different diameters, the smaller diameter spacer particle will be referred to as a small spacer particle, and the larger diameter spacer particle will be referred to as a large spacer particle.

In this embodiment, aluminum powder with a particle size of 3 μm is used as the metal particles, sodium chloride particles with a particle size of 400 μm are used as the large spacer particles, and sodium chloride particles with a particle size of 30 to 50 μm are used as the small spacer particles. Further, in all the particles, 20% by volume (Vol%) of aluminum powder, 60% by volume of sodium chloride particles with a particle size of 400 μm, and 20% of sodium chloride particles with a particle size of 30 to 50 μm are contained.

Subsequently, a spacer removal step is performed in which the spacer particles are dissolved and removed. In this embodiment, since sodium chloride particles are used as spacer particles, the spacer particles are dissolved and removed by washing the sintered body with water.

As a result, in the sintered body, pores 31 and 32 are formed in the portions where the spacer particles were present. Specifically, in the sintered body, large pores 32 are formed in areas where large spacer particles were present, and small pores 31 are formed in areas where small spacer particles were present. In this way, the heat transfer section 3, which is a porous material having a plurality of pores 31 and 32 with different diameters, is completed. Note that if the large pores 32 are not exposed on the outermost surface of the heat transfer section 3 after the spacer removal process, the large pores 32 may be exposed by cutting the surface of the heat transfer section 3. good.

FIG. 3 shows a micrograph of the heat transfer section 3 manufactured by the above manufacturing method. In FIG. 3, gray areas indicate aluminum, and black areas indicate pores 31 and 32.

As shown in FIG. 3, a dense layer 301 made of densely sintered aluminum is formed on the lower side of the heat transfer section 3. A porous layer 302 in which a large number of pores 31 and 32 are arranged is formed above the dense layer 301. A large number of small pores 31 and large pores 32 are formed in the porous layer 302 .

Here, as a comparative example, FIG. 4 shows a micrograph of a heat transfer part 3A manufactured by sintering metal particles and spacer particles of one type of diameter in a sintering process.

In the comparative example, aluminum powder with a particle size of 3 μm is used as the metal particles, and sodium chloride particles with a particle size of 30 to 50 μm are used as spacer particles of one type of diameter. In addition, 20% by volume (Vol%) of aluminum powder and 80% of sodium chloride particles with a particle size of 30 to 50 μm are contained in all the particles.

In the comparative example, a sintering process was performed in which aluminum powder and sodium chloride particles with a particle size of 30 to 50 μm were mixed and sintered, and then a spacer removal process similar to that in the example was performed. As a result, pores 33 are formed in the sintered body in the portion where spacer particles of one type of diameter were present. In this way, the heat transfer part 3A, which is a porous material having a plurality of pores 33 with a single diameter, is completed.

As shown in FIG. 4, in the heat transfer section 3A of the comparative example, a large number of pores 33 are formed in the porous layer 302. The diameters of the large number of pores 33 are uniform. That is, one peak value is formed in the frequency distribution of the diameters of the pores 33 formed in the heat transfer section 3A of the comparative example.

As explained above, in the evaporative cooling device 1 of this embodiment, the heat transfer section 3 is made of a porous material having a plurality of pores 31 and 32 with different diameters. In the frequency distribution of the diameters of the pores 31 and 32 formed in the heat transfer section 3, at least two different peak values are formed. In the pore diameter frequency distribution, the small pores 31 that form a small peak value form a liquid phase refrigerant passage 310, and the large pores 32 that form a large peak value form a gas phase refrigerant passage 320. .

According to this, the small pores 31 can supply the liquid-phase refrigerant liquid 11 into the heat transfer section 3 to form a boiling point of the refrigerant liquid 11 . The large pores 32 allow the boiled refrigerant liquid 11 to flow out of the heat transfer section 3 . At this time, the diameter of the large pores 32 through which the boiled refrigerant liquid 11 flows is larger than the diameter of the small pores 31, so the pressure loss when discharging the boiled refrigerant liquid 11 to the outside of the heat transfer section 3 is reduced. can be reduced. As a result, it becomes possible to improve cooling performance.

Further, the method for manufacturing the heat transfer part 3 in this embodiment includes a sintering step of sintering metal particles and spacer particles of at least two different diameters, and a spacer removal step of melting and removing the spacer particles. ing. According to this, it is possible to manufacture the heat transfer part 3 with high precision in the diameters and porosity of the pores 31 and 32.

(Second embodiment)
Next, a second embodiment of the present invention will be described based on the drawings. In this embodiment, the configuration of the heat transfer section 3 is changed compared to the first embodiment.

Specifically, as shown in FIGS. 5 and 6, grooves 4 are formed in the heat transfer section 3. As shown in FIGS. By providing the groove portion 4 in the heat transfer portion 3, an uneven portion 40 is formed on the surface of the heat transfer portion 3. A plurality of ring-shaped (namely, annular) grooves 4 are formed in the heat transfer part 3 of this embodiment. The plurality of ring-shaped grooves 4 are arranged concentrically when viewed from the thickness direction of the heat transfer section 3.

Next, regarding the method of manufacturing the heat transfer section 3 of this embodiment, only the differences from the first embodiment will be described. The method for manufacturing the heat transfer part 3 in this embodiment includes forming an uneven portion 40 on the surface of a mixture of metal particles and spacer particles (in this example, a sintered body of metal particles and spacer particles) before the spacer removal step. The method includes a step of forming an uneven portion.

In the uneven portion forming step of this embodiment, after the sintering step, the groove portions 4 are formed by cutting the sintered body of metal particles and spacer particles. Thereafter, a spacer removal step is performed to remove spacer particles from the sintered body in which the groove portion 4 is formed. As a result, the heat transfer section 3 having the uneven portions 40 formed on its surface is completed.

The other configuration and manufacturing method of the heat transfer section 3 are the same as those in the first embodiment. Therefore, also in the evaporative cooling device 1 of this embodiment, it is possible to obtain the same effects as in the first embodiment. That is, according to the boiling cooling device 1 of this embodiment, it is possible to reduce the pressure loss when discharging the boiled refrigerant liquid 11 to the outside of the heat transfer section 3, and improve the cooling performance.

Furthermore, in this embodiment, since the uneven portion 40 is formed on the surface of the heat transfer section 3, the surface area of the heat transfer section 3 can be increased. Thereby, the number of small pores 31 and large pores 32 exposed on the surface of the heat transfer section 3 can be increased. Therefore, the area for supplying the refrigerant liquid 11 into the inside from the surface of the heat transfer section 3 and the area for discharging the boiled refrigerant liquid 11 (ie, bubbles) from the surface of the heat transfer section 3 can be increased. As a result, it becomes possible to further improve cooling performance.

(Third embodiment)
Next, a third embodiment of the present invention will be described based on the drawings. This embodiment differs from the first embodiment in that the refrigerant liquid 11 in the cooling tank 10 is circulated.

As shown in FIG. 7, the cooling tank 10 is connected to a circulation circuit 20 in which the refrigerant liquid 11 in the cooling tank 10 circulates. The circulation circuit 20 is provided with a circulation pump 21 and a heat exchanger 22.

The circulation pump 21 pumps the refrigerant liquid 11 to circulate through the circulation circuit 20 and supplies the refrigerant liquid 11 to the heat exchanger 22 . The heat exchanger 22 radiates heat from the refrigerant liquid 11 to cool it. As the heat exchanger 22, for example, a radiator that cools the refrigerant liquid 11 by exchanging heat with outside air, or a chiller that cools the refrigerant liquid 11 by exchanging heat with a low-temperature refrigerant of a refrigeration cycle, or the like can be used. By cooling the refrigerant liquid 11 with the heat exchanger 22, a rise in temperature of the refrigerant liquid 11 can be suppressed, and a subcooled state can be maintained.

The circulation circuit 20 is connected to the cooling tank 10 at a refrigerant liquid outlet section 23 and a refrigerant liquid inlet section 24 . The refrigerant liquid 11 in the cooling tank 10 flows out into the circulation circuit 20 via the refrigerant liquid outlet section 23 . The refrigerant liquid 11 that has circulated through the circulation circuit 20 flows into the cooling tank 10 via the refrigerant liquid inlet section 24 .

Inside the cooling tank 10, a flow of the refrigerant liquid 11 is formed from the refrigerant liquid inlet portion 24 toward the refrigerant liquid outlet portion 23. In the example shown in FIG. 7, a refrigerant liquid inlet portion 24 is provided on the left side of the cooling tank 10, and a refrigerant liquid outlet portion 23 is provided on the right side of the cooling tank 10. Therefore, a flow of the refrigerant liquid 11 from the left side to the right side is formed inside the cooling tank 10.

The rest of the configuration of the evaporative cooling device 1 is the same as that of the first embodiment. Therefore, also in the evaporative cooling device 1 of this embodiment, it is possible to obtain the same effects as in the first embodiment. That is, according to the boiling cooling device 1 of this embodiment, it is possible to reduce the pressure loss when discharging the boiled refrigerant liquid 11 to the outside of the heat transfer section 3, and improve the cooling performance.

Furthermore, according to the present embodiment, the refrigerant liquid 11 in the cooling tank 10 is supplied to the heat exchanger 22 via the circulation circuit 20 and cooled by the heat exchanger 22. Cooling by the heat exchanger 22 allows the refrigerant liquid 11 to actively maintain a subcooled state. As a result, it becomes possible to further improve cooling performance.

(Other embodiments)
The present invention is not limited to the above-described embodiments, and can be modified in various ways as described below without departing from the spirit of the present invention. Further, the means disclosed in each of the embodiments described above may be combined as appropriate within a practicable range.

(1) In the embodiment described above, an example was explained in which the electronic device 2 was provided outside the cooling tank 10, but heat exchange is possible between the electronic device 2 and the refrigerant liquid 11 in the cooling tank 10. If so, the electronic device 2 may be provided inside the cooling tank 10. That is, the electronic device 2 and the heat transfer unit 3 may be immersed in the refrigerant liquid 11 and the heat generated by the electronic device 2 may be radiated to the refrigerant liquid 11. In this case, an insulating fluid may be used as the refrigerant liquid 11. Specifically, a fluorine-based inert liquid may be used as the refrigerant liquid. Fluorine-based inert liquids are refrigerant liquids with excellent insulation, heat transfer properties, and stability.

(2) In the embodiment described above, an example was explained in which the evaporative cooling device 1 is a closed type, that is, the cooling tank 10 is a liquid-tight structure not communicating with the atmosphere. but not limited to. For example, the boiling cooling device 1 may be of an open type.

Specifically, by providing an atmospheric opening in the upper part of the cooling tank 10, the inside of the cooling tank 10 may be opened to the atmosphere through the atmospheric opening. In this case, the inside of the cooling tank 10 is maintained at atmospheric pressure. Further, a liquid storage tank may be provided outside the cooling tank 10 to store the refrigerant liquid 11 and communicate with the cooling tank 10, and an atmospheric opening may be formed in the liquid storage tank.

(3) In the second embodiment described above, an example was described in which a plurality of ring-shaped grooves 4 were formed in the heat transfer section 3, but the shape of the grooves 4 is not limited to this aspect. For example, as shown in FIG. 8, the groove portions 4 may be formed in the heat transfer portion 3 in a lattice shape (that is, a mesh shape). As shown in FIG. 9, a plurality of circular grooves 4 may be formed in the heat transfer section 3. As shown in FIG. 10, a plurality of rectangular (square-shaped in this example) groove portions 4 may be formed in the heat transfer portion 3.

(4) In the second embodiment described above, the uneven portion 40 is formed by cutting the sintered body in the uneven portion forming step, but the method for forming the uneven portion 40 is not limited to this mode. For example, in the sintering process, sintering is performed by transporting a mixture of metal particles and spacer particles into a heating furnace while being held down by a plate-shaped member from the thickness direction. The uneven portion 40 may be formed in the sintered body by forming unevenness on the sintered body. In this case, the sintering process and the unevenness forming process can be performed simultaneously.

2 Electronic equipment (object to be cooled)
3 Heat transfer part 11 Refrigerant liquid 31 Small pore (pore)
32 Large pore (pore)
310 Liquid phase refrigerant passage 320 Gas phase refrigerant passage

Claims (5)

comprising a heat transfer part (3) that promotes heat transfer from the object to be cooled (2) to the refrigerant liquid (11),
The heat transfer part is made of a porous material having a plurality of pores (31, 32) with different diameters,
At least two different peak values are formed in the frequency distribution of the diameter of the pores formed in the heat transfer part,
Among the two different peak values, when the smaller peak value is taken as the small peak value and the larger peak value is taken as the large peak value,
The pores (31) forming the small peak value form liquid phase refrigerant passages (310) that cause capillary action;
The pores (32) forming the large peak value form a vapor phase refrigerant passage (320) through which the boiled refrigerant liquid flows out of the heat transfer section. The boiling cooling device according to claim 1, wherein in the frequency distribution, the large peak value is 5 times or more the small peak value. The boiling cooling device according to claim 1 or 2, wherein an uneven portion (40) is formed on the surface of the heat transfer portion. A method for manufacturing a heat transfer part that is applied to a boiling cooling device and transfers heat of an object to be cooled (2) to a refrigerant liquid (11), comprising:
a sintering step of sintering metal particles and spacer particles of at least two different diameters;
A method for manufacturing a heat transfer part, comprising: a spacer removing step of dissolving and removing the spacer particles. 5. The method for manufacturing a heat transfer part according to claim 4, further comprising a step of forming an uneven portion (40) on the surface of the mixture of the metal particles and the spacer particles before the spacer removing step.

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