JP4899997B2 - Thermal siphon boiling cooler - Google Patents

Description

  The present invention relates to a cooler for semiconductor devices, electronic devices, and the like, and more particularly to a thermal siphon-type boiling cooler that circulates a refrigerant using a boiling phenomenon.

  In recent years, in order to cool a large amount of heat generated in semiconductor devices, electronic devices, etc., a material having high thermal conductivity is bonded to the outside of the semiconductor device, etc. Methods have been developed to obtain cooling performance. In addition, a method for obtaining a higher cooling effect by boiling the refrigerant with a heat absorber has been developed. In these cooling methods, it is necessary to circulate the refrigerant between the heat absorbing portion and the heat radiating portion in order to release the heat taken away by the refrigerant to the outside, and a pump is generally used as the circulating means. Yes.

  In the case of a boiling cooler, the vapor collects on the upper side with respect to the direction of gravity due to the density difference between the vapor and the liquid generated by boiling the refrigerant. By utilizing this principle, a thermal siphon type cooling structure that does not require a pump has been proposed by installing a heat absorption part at the lower part of the cooler and a heat radiation part at the upper part. For example, the structures disclosed in Patent Document 1 and Patent Document 2 correspond to this. In addition, various boiling coolers as shown below have been proposed. Unless otherwise specified, the “boiling cooler” or “siphonic boiling cooler” refers to a thermal siphonic boiling cooler.

  Patent Document 1 proposes a siphon-type boiling cooler for cooling an electronic device mounted on a vehicle. This boiling cooler is characterized in that, in addition to not requiring a pump, the heat absorption part and the heat radiation part can be formed relatively integrally.

  Patent Document 2 proposes a siphon type and pumpless boiling cooler by arranging a heat dissipating part on the upper side in the direction of gravity and a heat absorbing part on the lower side while installing the heat absorbing part and the heat dissipating part at positions separated from each other. ing. This boiling cooler is characterized in that the heat absorbing portion and the heat radiating portion are connected by a steam tube and a liquid tube described below. That is, a thick steam pipe is used in the direction from the heat absorption part to the heat radiation part, and is connected to the upper part of the heat radiation part. A thin liquid tube is used in the direction from the heat radiating portion to the heat absorbing portion, and is connected to the lower portion of the heat radiating portion. In addition, the structure which arrange | positions a thermal radiation part in the upper part of a gravitational direction and a thermal absorption part in the lower part is proposed also in patent document 3. FIG.

  Patent Document 4 proposes a siphon type structure that promotes convection of the refrigerant in the heat radiating part on the screen side of the notebook PC. In this structure, from the heat absorption part to the heat dissipation part, the heat pipe is used to maintain the mobility while thermally connecting the hinge part of the notebook PC.

  Patent Document 5 proposes a structure in which a radiator for radiating heat is constructed at a position extremely above a heat absorbing portion, whereby steam generated in the heat absorbing portion is cooled and condensed and then returned to the heat absorbing portion. This structure is intended to optimize the heat transfer performance by forming a “pyramid fin” in the heat absorption part to promote boiling in a pool boiling type cooling device that does not use forced convection.

  Patent Document 6 proposes a method that uses a heat pulse that pushes the refrigerant by connecting the heat absorbing part and the heat radiating part with a pipe, vaporizing the refrigerant with a heater and using the vapor pressure to promote circulation of the refrigerant. ing.

Japanese Patent Laid-Open No. 2001-268843 (page 5-6, FIG. 6, FIG. 7) JP 2002-168547 A (page 6-7, FIG. 1, FIG. 2, FIG. 3) Japanese Patent Laying-Open No. 2005-195226 (pages 13-17) Japanese Patent No. 3037931 (page 8, FIG. 1) Japanese Patent No. 3777964 (page 8, FIG. 11) JP 2006-237188 A (page 7)

  However, the conventional boiling cooler described above has the following problems. The refrigerant used in the siphon-type boiling cooler flows into the heat absorption part as a liquid phase, and after boiling (vaporization) by heat exchange in the heat absorption part, it becomes steam and travels to the heat dissipation part. During this boiling, the vapor bubbles generated on the heat transfer surface of the heat absorbing part adhere and stay. Since the vapor bubbles have a smaller heat transfer effect than the refrigerant, they stay on the heat transfer surface and cause the cooling performance of the boiling cooler to deteriorate. For example, in the conventional boiling coolers disclosed in Patent Documents 1 to 5, the circulation of the refrigerant depends on the gravitational effect of the difference in height between the heat absorbing portion and the heat radiating portion, and a structure that prevents the retention of vapor bubbles. Not shown. For this reason, there is a possibility that sufficient cooling performance cannot be obtained.

  On the other hand, for example, by circulating and convection of the refrigerant using an external device such as a pump, it is possible to peel the vapor bubbles and prevent the cooling effect from decreasing. Such a so-called forced convection effect corresponds to circulating the refrigerant by the vapor pressure of the refrigerant vaporized by the heater in the boiling cooler shown in Patent Document 6. However, from the viewpoint of the second law of thermodynamics, this method of obtaining power using heat is very inefficient considering that power is already supplied to the heater. I must say. Furthermore, since an electric circuit for generating heat pulses and a check valve for maintaining pressure are necessary, the system becomes expensive even when compared with a method using a conventional pump. There is.

  In addition to this, in the conventional boiling cooler, because it depends on the above-described gravity effect, the positional relationship between the heat absorption part and the heat generation part is the use state of the equipment in which the boiling cooler is mounted (for example, There is a problem that sufficient cooling performance cannot be obtained if it is changed depending on “horizontal placement” and “vertical placement”. Further, for example, in the conventional boiling cooler disclosed in Patent Document 4, there is a risk that the thermal resistance from the heat absorption part to the heat pipe and from the heat pipe to the heat radiation part increases. For this reason, there is a possibility that the temperature of the gas-liquid phase of the heat radiating portion may cause a large temperature difference from the temperature of the cooling component, and as a result, there is a problem that the effect of boiling cannot be realized ideally.

  The present invention has been made in view of such problems, and improves the cooling performance without requiring an external device such as a pump, and the two modes in which the positional relationship between the heat absorbing portion and the heat radiating portion changes mutually. It is an object of the present invention to provide a thermal siphon-type boiling cooler that can provide sufficient cooling performance.

  The thermal siphon type boiling cooler according to the present invention includes a refrigerant flow path inside, a heat absorption part that cools the heating element using the heat of vaporization of the refrigerant, a heat radiation part that radiates heat of the gas-phase refrigerant, and this heat radiation. A steam pipe and a liquid pipe provided between the heat sink and the heat absorption part, and the refrigerant flow path includes a plurality of cross-sectional areas that increase from the upstream side to the downstream side of the refrigerant. The first flow path is included.

  In the present invention, by providing a plurality of first channels whose cross-sectional areas increase from the upstream side to the downstream side of the refrigerant, the downstream side of the first channel is lower than the upstream side. Kept in pressure. Thereby, since the refrigerant | coolant (steam) vaporized by heat exchange is suck | inhaled downstream by a pressure difference, a vapor | steam can be discharged | emitted from a heat absorption part effectively. Further, by providing a plurality of first flow paths, the heat transfer area between the flow paths and the refrigerant can be increased. For this reason, the cooling performance of the boiling cooler can be improved.

  In this case, it is preferable that the first channel has a rectangular cross-sectional shape in which each channel has a shorter side length of 1 mm or less when viewed from the upstream side of the refrigerant. This makes it easier for the gas-phase refrigerant to flow through the first flow path than the liquid-phase refrigerant, thereby further promoting the discharge of the vapor. Further, since the flow velocity in the first flow path is increased, the vapor bubbles of the refrigerant generated by boiling due to the forced convection effect can be separated from the inner wall of the flow path immediately after the generation. For this reason, the fall of the cooling performance by retention of the vapor bubble with a low heat-transfer effect can be suppressed effectively.

  The refrigerant flow path further includes a second flow path in parallel with the first flow path, and the first flow path and the second flow path are viewed from the upstream side of the refrigerant. The first channel can be configured to have a comb-like cross-sectional shape connected as teeth. As a result, the liquid phase refrigerant flows through the second flow path, and the refrigerant that has become vapor due to boiling is sucked into the first flow path, so that the liquid phase / gas phase separation can be further promoted.

  In the case where the second flow path is provided, the second flow path has at least an area of a surface on the side where heat of the heating element is transmitted is larger than an area of a surface where the heating element and the heat absorbing portion are in contact with each other. It is preferable to have a rectangular cross-sectional shape that is large and has a shorter side length of 2 mm or less when viewed from the upstream side of the refrigerant. Thereby, since the flow rate of the liquid-phase refrigerant in the second flow path is increased, it is possible to further promote the separation of the vapor bubbles due to the forced convection effect.

  Furthermore, it is possible to configure a closed-loop pipeline in the order of the heat absorption part, the steam pipe, the heat radiation part, and the liquid pipe so that there is no external device for circulating the refrigerant. Even in this case, since the peeling of the vapor bubbles is promoted by the forced convection effect, it is possible to effectively suppress the decrease in the cooling effect. Further, this eliminates the need for an external device such as a pump, thereby reducing the cost and further improving the reliability of the boiling cooler.

  Furthermore, when p is the pressure loss of the refrigerant in the heat absorbing part, ρ is the liquid density of the refrigerant, and g is the gravitational acceleration, the position of the refrigerant outlet of the heat radiating part in the usage mode is the refrigerant inlet of the heat absorbing part. It is configured to be higher than the position h by a distance h that satisfies the following mathematical formula (h1 = p / (ρ · g)) in the direction of gravity and at least a distance h in the horizontal direction with respect to the position of the refrigerant inlet of the heat absorption part. be able to. Thus, for example, in each of the two usage modes rotated 90 degrees such as horizontally and vertically, the circulation of the refrigerant in the boiling cooler can be appropriately maintained, and sufficient cooling performance can be obtained. it can.

  Furthermore, the refrigerant can be configured to be a liquid having a surface tension smaller than that of water.

  According to the present invention, a thermal siphon that improves cooling performance without requiring an external device such as a pump, and can provide sufficient cooling performance in two modes in which the positional relationship between the heat absorbing portion and the heat radiating portion changes mutually. A type boiling condenser is obtained.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. First, a first embodiment of the present invention will be described. FIGS. 1A and 1B are diagrams showing a configuration of a thermal siphon-type boiling cooler according to the first embodiment, and FIGS. 2A to 2C are cross-sectional views showing a boiling-type heat absorption part. FIG.

  As shown in FIG. 1 (a), a boiling heat absorption part 1 is provided so as to be in contact with the heating element 3. A heat radiating part 2 is arranged at the upper right part of the boiling heat absorbing part 1. The liquid inlet 9 of the boiling heat absorption part 1 and the liquid outlet 11 of the heat radiating part 2 are connected by a liquid pipe 5. In addition, the steam outlet 10 of the boiling heat absorption part 1 and the steam inlet 12 of the heat radiating part 2 are connected by a steam pipe 4. These boiling type heat absorption part 1, steam pipe 4, heat radiation part 2, and liquid pipe 5 constitute a closed pipe, and have a refrigerant (not shown) inside. As the refrigerant, a liquid having a surface tension smaller than that of water, for example, alcohols is used. The heat dissipating part 2 includes a cooling fan 6 outside thereof. In the following description, it is assumed that gravity works from the upper side to the lower side of FIGS. 1 (a) and 1 (b). In addition, a state in which the positional relationship between the boiling heat absorbing portion 1 and the heat radiating portion 2 is as shown in FIG. 1A is referred to as a “first usage mode”.

  FIG. 1 (b) shows a state where the boiling cooler of FIG. 1 (a) is rotated 90 degrees to the left so that the heat dissipating part 2 is located at the upper left part of the boiling heat absorbing part 1. It is. In addition, the state in which the positional relationship between the rising-type heat absorbing unit 1 and the heat radiating unit 2 is as shown in FIG.

  Next, the operation of this embodiment will be described. The present embodiment shown in FIGS. 1A and 1B is a cooler that is expected to be used in two directions (for example, “horizontal” and “vertical”), such as a desktop PC (Personal Computer). Assumed.

  In the first usage mode shown in FIG. 1A, the heat generated in the heating element 3 is transmitted to the boiling heat absorption part 1 in contact with the heating element 3. With this heat, the liquid refrigerant inside the boiling heat absorbing portion 1 boils and becomes steam, thereby depriving the heating element 3 of thermal energy. The refrigerant that has become vapor collects on the upper side with respect to the direction of gravity due to the density difference from the liquid. For this reason, the steam moves into the heat radiating section 2 via the steam outlet 10, the steam pipe 4 and the steam inlet 12. The vapor in the heat radiating unit 2 is cooled and condensed by the heat radiating unit 2 and the cooling fan 6 to become a liquid. The refrigerant that has been condensed into a liquid collects downward with respect to the direction of gravity due to the density difference from the vapor. For this reason, the refrigerant flows out from the liquid outlet 11, flows in the liquid pipe 5 in the direction of the arrow in the figure, and returns from the liquid inlet 9 to the boiling heat absorption unit 1. Since this refrigerant tends to return to the boiling-type heat absorption part 1 by one way, the liquid column which returns to the boiling-type heat absorption part 1 arises. As a result, a static pressure due to the liquid column is generated at the liquid inlet 9, and the static pressure causes the refrigerant to be sent into the boiling heat absorbing portion 1. Here, in order to circulate the refrigerant in the closed pipe, the difference in height between the boiling heat absorbing portion 1 and the heat radiating portion 2 is set to be equal to or greater than the vertical distance h1 obtained by the following Equation 1.

ここで、ｐは吸熱部圧力損失、ρは冷媒液密度、ｇは重力加速度である。吸熱部での圧力損失は冷却に必要な冷媒の流量に依存する。また、沸騰冷却器の冷却性能も冷媒の流量に依存するので、同じ吸熱構造であれば、高さｈ１を変化させることにより、冷却能力を変化させることができる。もちろん、受熱部の構造を変えることにより、同じ高さｈ１でも冷却能力を変化させることもできる。

Here, p is the heat absorption part pressure loss, ρ is the refrigerant liquid density, and g is the gravitational acceleration. The pressure loss in the heat absorption part depends on the flow rate of the refrigerant necessary for cooling. In addition, since the cooling performance of the boiling cooler also depends on the flow rate of the refrigerant, the cooling capacity can be changed by changing the height h1 with the same endothermic structure. Of course, by changing the structure of the heat receiving part, the cooling capacity can be changed even at the same height h1.

  In the second usage mode shown in FIG. 1 (b), the boiling heat absorption part 1 is vertical. The liquid flows in from the lower part (liquid inlet 9) of the boiling heat absorption part 1, and the steam generated by boiling is exhausted from the upper part (steam outlet 10). In this case, the vertical distance between the heat dissipating part 2 and the boiling heat absorbing part 1 is set at a distance h2. This distance h2 is desirably equal to or longer than h1 obtained by Equation 1 for the same reason as in the first usage mode.

  Next, the detailed structure of the boiling type heat absorption part 1 is demonstrated with reference to Fig.2 (a) thru | or (c). 2A corresponds to a cross-sectional view taken along line AA shown in FIG. 2C, and FIG. 2B corresponds to a cross-sectional view taken along line BB shown in FIG. FIG. 2C corresponds to a cross-sectional view taken along line CC shown in FIG.

  As shown in FIG. 2A, the boiling heat absorption part 1 has a configuration divided into a first heat absorption part 13 and a second heat absorption part 14. For the first heat absorption part 13 and the second heat absorption part 14, for example, a material having high thermal conductivity such as copper is used. Further, the second heat absorbing portion 14 is formed with the following grooves and the like. Thus, the boiling-type heat absorption part 1 is made into a divided structure, and the periphery of the joint of the first heat absorption part 13 and the second heat absorption part 14 is made into a frame, thereby creating a sealing surface for making a sealed structure. Can be made easier. As a result, for the formation of the wedge-shaped flow path above the heat receiving structure, it is possible to form a fine flow path as will be described later by using cutting, wire electric discharge machining, or the like.

  In the first heat absorption part 13, a main heat receiving liquid flow path 8 is formed which becomes a passage for the liquid refrigerant flowing into the boiling heat absorption part 1 from the liquid inlet 9. As shown in FIG. 2B, the main heat receiving liquid channel 8 has a wide width parallel to the lower surface (the side in contact with the heating element 3) and a forced convection effect within the main channel 8 as shown in FIG. It has a flat shape with the following thickness (height).

  A liquid inlet 9 and a steam outlet 10 are formed in the second heat absorption part 14. In addition, a plurality of steam evacuation channels 7 are formed mainly as a steam channel from the liquid inlet 9 to the steam outlet 10. The steam escape passage 7 is a fine groove having a width of, for example, 1 mm or less from the side in contact with the main heat receiving liquid passage 8 toward the top of the figure, and is directed to the direction from the liquid inlet 9 to the steam outlet 10. They are formed in parallel. The flow path close to the diameter of the vapor bubbles generated by boiling is formed with the vapor escape flow path width of 1 mm or less, and the effect of effectively sucking the vapor bubbles is obtained. It is preferable that the area of the main heat receiving liquid channel 8 on the side in contact with the first heat absorbing portion 13 is equal to or larger than the contact area between the first heat absorbing portion 13 and the heating element 3. Further, the vapor escape passage 7 has a wedge shape whose height gradually increases from the liquid inlet 9 side toward the vapor outlet 10, for example, has a height of at least 1 mm or more. Yes.

  The operation in the boiling heat absorbing part 1 shown in FIG. 2 will be described. In the first usage mode, the refrigerant that has flowed in as liquid from the liquid inlet 9 flows through the main heat receiving liquid flow path 8 and is in contact with the lower surface of FIGS. 2A and 2B (not shown). Boiling due to the heat transferred from. Although the boiled refrigerant becomes vapor, a part of the refrigerant becomes vapor bubbles and adheres to the inner wall of the boiling heat absorption part 1. If the vapor bubbles stay, the heat transfer from the boiling heat absorbing portion 1 to the refrigerant is hindered, which causes a decrease in the cooling performance of the boiling cooler. Here, since the main heat receiving liquid channel 8 is formed flat, the refrigerant passes through the vicinity of the heating element 3 at a speed. For this reason, due to the forced convection effect on the refrigerant, the adhering vapor bubbles are peeled off from the inner wall of the boiling heat absorbing portion 1 and sucked into the vapor retreat channel 7 perpendicular to the main heat receiving liquid channel 8. More specifically, since the wedge-shaped flow path is directly connected to the steam outlet 10 and the low pressure in the vicinity of the outlet is maintained by being filled with steam, the wedge-shaped flow path is generated on the heat transfer surface. Vapor bubbles are sucked into the vapor evacuation channel 7 due to a pressure difference with the liquid channel. As a result, the vapor bubbles are kept away from the heat transfer surface immediately after the occurrence of the vapor bubbles, so that the heat transfer performance can be maintained by suppressing the retention of the vapor bubbles in an extremely thin flow path. The reason why the thickness of the main heat receiving liquid channel 8 is set to 2 mm or less is that it has been confirmed through experiments that the effect of removing the steam bubbles is increased. In this case, the thickness of the main heat receiving liquid channel 8 is sufficiently smaller than the length and width of the main heat receiving liquid channel 8.

  The vapor escape passage 7 is a finer passage than the main heat-receiving liquid passage 8 and thus has a structure that allows the vapor to pass more easily than the liquid. Further, since the steam escape passage 7 has a wedge shape, more steam can be smoothly flowed without hindering the flow of steam due to back pressure or the like with respect to the amount of steam that increases downstream. Can be discharged from the steam outlet 10. Further, since the pressure in the steam retraction channel 7 is lower than the pressure in the main heat receiving liquid channel 8, the steam has a bypass structure to the steam outlet 10 and collects the steam bubbles so as to be absorbed from the heat absorption surface. be able to. The reason why the width of each flow path of the vapor retreat flow path 7 is set to 1 mm or less is that it has been confirmed through experiments that the effect of discharging the steam bubbles is increased. In this case, the width of each flow path of the steam retraction flow path 7 is sufficiently smaller than the length and height of the vapor retraction flow path 7.

  In this embodiment, the flow rate of the refrigerant flowing into the boiling heat absorption part 1 is generated by static pressure due to the difference between the height of the liquid column on the inflow side and the height of the liquid column on the outflow side. . When the calorific value is small, the amount of evaporation is small, so the flow rate of the refrigerant is small and the difference in liquid column length is also small. When the calorific value reaches the maximum, the evaporation amount increases, the steam outflow side is filled with steam, and the flow rate is determined depending on the static pressure at which the liquid column length on the liquid inflow side is generated. As a result, the boiling cooler of the present embodiment can automatically adjust the forced convection effect by increasing the flow rate of the refrigerant and increasing the flow velocity according to the calorific value.

  As described above, even when an external device such as a pump is not used, the retention of bubbles that causes a decrease in the heat transfer effect is suppressed by the forced convection effect, so that the cooling performance of the boiling cooler is effectively improved. Can be improved. Further, in the second usage mode, a part of the refrigerant also flows into the vapor retreat channel 7, thereby increasing the heat transfer area between the refrigerant and the boiling heat absorbing unit 1. For this reason, the cooling performance which is not different from the first usage mode can be obtained. Furthermore, by forming the boiling endothermic portion 1 by processing the inside thereof, it is possible to effectively separate the liquid inside while making the outer shape of the boiling endothermic portion 1 compact.

  As the refrigerant used in the present invention, a liquid having a smaller surface tension than water is suitable. In the boiling of water, the diameter of vapor bubbles generated by the surface tension is about several millimeters, and a reforming process is required to make it smaller. By modifying the water or using a material whose surface tension is originally smaller than that of water, the diameter when the bubbles are peeled off from the endothermic surface can be reduced. It is conceivable that a temperature change locally occurs in the growth of bubbles, and there is a risk of a large temperature distribution when cooling an electronic component of about 10 mm is considered. By reducing the bubbles, the foaming point is increased, the electronic component is kept at a constant temperature, and can be effectively exhausted from the vapor escape passage 7.

  Next, a second embodiment of the present invention will be described. FIG. 3A to FIG. 3C are cross-sectional views showing a boiling heat absorption part of a thermal siphon boiling cooler according to the second embodiment. 3A corresponds to a cross-sectional view taken along line XX shown in FIG. 3B, and FIG. 3B corresponds to a cross-sectional view taken along line YY shown in FIG. (C) corresponds to a cross-sectional view taken along line ZZ shown in FIG. 3A to 3C are the same as those of the first embodiment except for the items described below, and in FIGS. 3A to 3C, FIGS. The same components are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 3C, a flat channel corresponding to the main heat receiving liquid channel 8 of FIG. 2 is not provided, and a plurality of channels 15 similar to the vapor escape channel 7 are provided. Is provided. The liquid refrigerant flowing from the liquid inlet 9 is distributed to the plurality of flow paths 15. This flow path 15 also serves as a vapor escape flow path. Other configurations are the same as those in the first embodiment described above. In the present embodiment, heat exchange is performed in the plurality of groove-shaped flow paths 15. Thereby, the heat transfer area of the boiling-type heat absorption part 1 and a refrigerant | coolant can be increased. Further, by increasing the flow velocity in the flow path 15, it is possible to promote the separation of the vapor bubbles as in the first embodiment. Furthermore, since the cross-sectional area of the flow path 15 increases toward the steam outlet 10, the steam can be discharged smoothly. As described above, also in the present embodiment, the same effect as in the first embodiment can be obtained.

(A) And (b) is a figure which shows the structure of the thermal siphon-type boiling cooler which concerns on 1st Embodiment. (A) thru | or (c) is sectional drawing which shows the boiling-type heat absorption part of the thermal siphon-type boiling cooler which concerns on 1st Embodiment. (A) thru | or (c) are sectional drawings which show the boiling-type heat absorption part of the thermal siphon-type boiling cooler which concerns on 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1; Boiling type heat absorption part 2; Heat radiation part 3; Heat generating body 4; Steam pipe 5; Liquid pipe 6; Cooling fan 7; Steam retraction flow path 8; Outlet 11; liquid outlet 12; steam inlet 13; first heat absorption part 14; second heat absorption part 15; flow path

Claims (7)

A heat absorption part that has a refrigerant flow path inside and cools the heating element using the heat of vaporization of the refrigerant, a heat radiation part that dissipates the gas-phase refrigerant, and a vapor provided between the heat radiation part and the heat absorption part The refrigerant flow path includes a plurality of first flow paths in which the cross-sectional area of each flow path increases from the upstream side to the downstream side of the refrigerant. Thermal siphon boiling cooler. 2. The thermal siphon according to claim 1, wherein each of the first channels has a rectangular cross-sectional shape in which each channel has a shorter side length of 1 mm or less when viewed from the upstream side of the refrigerant. Type boiling cooler. The refrigerant flow path further includes a second flow path in parallel with the first flow path, and the first flow path and the second flow path are the first flow path when viewed from the upstream side of the refrigerant. The thermal siphon-type boiling cooler according to claim 1 or 2, characterized in that it has a comb-like cross-sectional shape connected to each other as teeth. The second flow path has at least an area of a surface on the side where heat of the heating element is transmitted is larger than an area of a surface where the heating element and the heat absorbing portion are in contact, and is shorter when viewed from the upstream side of the refrigerant. The thermal siphon-type boiling cooler according to claim 3, which has a rectangular cross-sectional shape with a side length of 2 mm or less. 5. The apparatus according to claim 1, wherein a closed loop pipe line is formed in the order of the heat absorption part, the steam pipe, the heat radiation part, and the liquid pipe, and no external device for circulating the refrigerant is provided. Thermal siphon type boiling cooler as described. When p is the pressure loss of the refrigerant in the heat absorption part, ρ is the liquid density of the refrigerant, and g is the gravitational acceleration, the position of the refrigerant outlet of the heat dissipation part in the usage mode is more than the position of the refrigerant inlet of the heat absorption part. 6 has a distance h that is equal to or higher than a distance h that satisfies the following mathematical formula in the direction of gravity, and has a distance that is equal to or longer than the distance h in the horizontal direction with respect to the position of the refrigerant inlet of the heat absorption unit. Thermal siphon boiling cooler.
h1 = p / (ρ · g) The thermal siphon boiling cooler according to any one of claims 1 to 6, wherein the refrigerant is a liquid having a surface tension smaller than that of water.

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