JP5447070B2 - Loop heat pipe and electronic equipment - Google Patents

Description

  The present invention relates to a loop heat pipe and an electronic device.

  2. Description of the Related Art Conventionally, a cooling method using a heat pipe is known as one of cooling methods for cooling a heating element (for example, a semiconductor element in an electronic device). A heat pipe is a heat transport device that transports heat using a phase change of a working fluid sealed inside. In addition, a heat transport device called a loop heat pipe has been proposed as a kind of the heat pipe.

  FIG. 20 schematically shows the operating principle of the loop heat pipe. The loop heat pipe includes an evaporator 101, a condenser 102, a steam pipe 103 and a liquid pipe 104 that connect the evaporator 101 and the condenser 102. The working fluid 106 is sealed at a constant pressure inside the loop heat pipe. The working fluid 106 changes from a liquid phase to a gas phase by heat supplied to the evaporator 101 from the outside, and then moves to the condenser 102 through the vapor pipe 103 with heat. After the working fluid 106 changes from the gas phase to the liquid phase due to heat radiation in the condenser 102, the working fluid 106 returns to the evaporator 101 through the liquid pipe 104, thereby transporting heat.

  A wick 105 that sucks up the liquid-phase working fluid 106 by capillary action is provided inside the evaporator 101 of the loop heat pipe. The liquid-phase working fluid 106 returned to the evaporator 101 is vaporized by receiving ambient heat while penetrating the inside of the wick 105 by capillary force.

U.S. Pat. No. 4,765,396 Japanese Patent Application Laid-Open No. 8-200196

The liquid phase working fluid and the gas phase working fluid coexist in the loop type heat pipe, and the distribution state of the gas phase working fluid and the liquid phase working fluid when starting the loop type heat pipe Is always different. For example, there is a case where the inside of the evaporation section is distributed so as to be completely filled with the liquid-phase working fluid.
In the above case, since there is no gas-phase working fluid in the evaporation section, there is no interface between the gas phase and the liquid phase (gas-liquid interface), which is the core of evaporation. For this reason, in the evaporation section, the working fluid in the liquid phase is evaporated to generate a working fluid in the gas phase, and the circulation of the working fluid is started after the gas-liquid interface is obtained. There is a problem that takes time to do.

  According to one aspect of the invention, a loop heat pipe having an evaporator connected between a liquid pipe and a steam pipe, the evaporator passing through a porous body that allows a working fluid flowing in from the liquid pipe to pass therethrough; , A porous body is housed inside, and a casing is formed between the casing and the porous body to form a vapor discharge part together with the porous body that guides the working fluid evaporated by the heat from the heating element to the steam pipe Then, a loop heat pipe is provided that includes a liquid repellent part exposed to the vapor discharge part and having liquid repellency with respect to the working fluid.

  According to another aspect of the invention, a semiconductor element and a loop heat pipe having an evaporator connected between a liquid pipe and a vapor pipe, in which the semiconductor element is in thermal contact, are provided and evaporated The vessel contains a porous body that allows the working fluid flowing in from the liquid pipe to pass through, and a porous body with a porous body that contains the porous body and guides the working fluid evaporated by the heat from the heating element to the steam pipe. There is provided an electronic device including a housing to be formed and a liquid repellent portion that is disposed between the housing and the porous body, is exposed to the vapor discharge portion, and has liquid repellency with respect to the working fluid.

  In one aspect of the loop heat pipe, the liquid repellent part between the case and the wick makes it difficult for the liquid-phase working fluid to enter the vapor discharge part of the evaporator, and it is easy to start instantaneously after heat input.

FIG. 1 is a perspective view showing an example of a computer and a loop heat pipe provided in the computer. FIG. 2 is a perspective view showing each part of an example of the evaporator unit. FIG. 3 is a cross-sectional view schematically showing a cross section in the longitudinal direction of the example (1) of the evaporator. FIG. 4 is a cross-sectional view showing a cross section taken along line A-A ′ of FIG. 3. FIG. 5 is a diagram showing an example of the relationship between the start time of the loop heat pipe and the temperature of the evaporator when the gas-liquid interface exists outside the wick. FIG. 6 is a diagram illustrating an example of the relationship between the start time of the loop heat pipe and the temperature of the evaporator when the outside of the wick is filled with a liquid-phase working fluid. FIG. 7 is a cross-sectional view schematically showing a cross section in the longitudinal direction of the example (2) of the evaporator. FIG. 8 is a cross-sectional view showing a cross section taken along line B-B ′ of FIG. 7. FIG. 9 is a perspective view showing an example of a liquid repellent structure. FIG. 10 is a cross-sectional view showing an example of a method for producing a liquid repellent structure in the evaporator example (2). FIG. 11: is sectional drawing which shows the cross section of the longitudinal direction of the example (3) of an evaporator. FIG. 12 is a cross-sectional view showing a radial cross section of the evaporator example (4). FIG. 13 is a cross-sectional view showing an example (4) of the evaporator, FIG. 13 (a) is a cross-sectional view schematically showing a cross-section along CC ′ in FIG. 12, and FIG. It is sectional drawing which shows typically the cross section in 12 DD '. FIG. 14: is sectional drawing which shows the cross section of the radial direction of the example (5) of an evaporator. FIG. 15 is a cross-sectional view showing a cross section in the radial direction when a liquid repellent portion is formed of a liquid-repellent processed metal in the evaporator example (4). FIG. 16: is sectional drawing which shows the cross section of the other example 1 of an evaporator unit. FIG. 17 is a cross-sectional view schematically showing a cross section taken along line E-E ′ of FIG. 16. FIG. 18 is a cross-sectional view showing a cross section of another example 2 of the evaporator unit. FIG. 19 is a cross-sectional view schematically showing a cross section taken along line F-F ′ of FIG. 18. FIG. 20 is a schematic diagram schematically showing the operating principle of the loop heat pipe.

  Hereinafter, an embodiment of an electronic device in which a loop heat pipe is mounted will be described with reference to the drawings. The electronic device described here is, for example, a computer having a CPU. The computer is provided with a loop heat pipe in order to cool the CPU that generates heat as the computer operates.

  FIG. 1 is a perspective view illustrating an example of a computer 1000 that is an embodiment of an electronic device and a loop heat pipe 200 provided in the computer 1000.

  The computer 1000 includes a power source 24 that stores electric power, a hard disk device 22 that stores information, and a substrate 21 having various electronic circuits. For example, the substrate 21 is provided with a memory 23 that temporarily stores information and a CPU 20 that is a semiconductor element that plays a central role in the operation of the computer 1000. The computer 1000 operates under the control of the CPU 20. The CPU 20 generates heat as the computer 1000 operates. For example, the CPU 20 has a square shape with a side length of 50 mm, and the heat generation amount of the CPU 20 is between 10 W and 120 W.

  The loop heat pipe 200 serves to cool the CPU 20 by absorbing heat from the CPU 20 and transporting the heat to the outside of the CPU 20. The loop heat pipe 200 includes the evaporator unit 10 that is in thermal contact with the CPU 20. The evaporator unit 10 receives heat from the CPU 20, which is a heating element, and evaporates the liquid-phase working fluid in the evaporator unit 10. In the embodiment shown in FIG. 1, for example, water is used as the working fluid of the loop heat pipe 200.

  For example, a copper hollow tube 8 is connected to the evaporator unit 10 in a loop so as to exit the evaporator unit 10 and return to the evaporator unit 10. And the inside of the hollow tube 8 can move the working fluid used as a heat transport material. As shown by a broken line in FIG. 1, a middle portion of the hollow tube 8 has a meandering portion 8a having a meandering shape, and copper radiating fins 7a are in contact with the meandering portion 8a. The heat of the gas phase working fluid that has moved through the hollow tube 8 in the direction of the solid line arrow shown in FIG. 1 is conducted to the heat radiating fins 7a through the meandering portion 8a that contacts the heat radiating fins 7a. Thereby, the gaseous working fluid is cooled and condensed. Here, in the hollow tube 8, the meandering portion 8 a with which the radiation fins 7 a are in contact becomes the condenser 2. In the embodiment shown in FIG. 1, the total length of the meandering portion 8a of the hollow tube 8 serving as the condenser 2 is, for example, about 250 mm.

  In addition, the vapor pipe 3 is a pipe that connects the evaporator unit 10 and the condenser 2 and moves the vapor-phase working fluid evaporated in the evaporator unit 10 to the condenser 2. In the embodiment shown in FIG. 1, the distance between the evaporator unit 10 and the condenser 2 is, for example, about 300 mm, and the pipe inner diameter of the steam pipe 3 is, for example, about 3 mm.

  Two fans 7 for exhausting the air inside the computer 1000 to the outside are provided in the vicinity of the heat radiation fins 7a. As the fan 7 is exhausted, hot air around the heat radiating fins 7 a is released to the outside of the computer 1000. As a result, the heat of the CPU 20 is finally released to the outside of the computer 1000. In the embodiment shown in FIG. 1, the size of each fan 7 is, for example, about 60 mm.

  On the other hand, the working fluid liquefied by the condenser 2 moves in the hollow tube along the solid line arrow shown in FIG. 1 and returns to the evaporator unit 10. The pipe that connects the evaporator unit 10 and the condenser 2 and moves the liquid-phase working fluid condensed in the condenser 2 to the evaporator unit 10 is the liquid pipe 4. In the embodiment shown in FIG. 1, the tube inner diameter of the liquid tube 4 is, for example, about 2 mm.

  Next, the evaporator unit 10 will be described in detail.

  FIG. 2 is a perspective view showing each part of an example of the evaporator unit 10. The evaporator unit 10 includes a main body part 11, a heat insulating member 12, a wick 5, a steam outlet part 13, and a liquid inlet part 14.

  The main body 11 has, for example, a dimension in the direction along the longitudinal direction of the steam outlet 13 and the liquid inlet 14 about 50 mm, a dimension in the direction of the steam outlet 13 or the liquid inlet 14 about 50 mm, and a dimension in the direction of the heat insulating member. A 20 mm metal (for example, copper) box body, the surface facing the lower side of FIG. The main body 11 contains three metal pipes 11a, each of which is a cylindrical case that accommodates the wick 5, in parallel at substantially equal intervals. And the main-body part 11 conducts the heat | fever received from CPU20 to each metal tube 11a. The main body 11 is formed with three double-tube evaporators in which the wick 5 is accommodated in the metal tube 11a. Each metal tube 11a is made of, for example, copper and has, for example, a longitudinal dimension of 50 mm, a tube thickness of about 2 mm, and an inner diameter of about 10 mm. In addition, the main-body part 11 and the metal pipe 11a can also be integrated by opening three holes which accommodate the wick 5 in a metal block, for example. By integrating the main body portion 11 and the metal tube 11a, the process of incorporating the metal tube 11a into the main body portion 11 can be omitted, so that the manufacturing cost can be reduced.

  The heat insulating member 12 is disposed on a surface (a surface facing the upper side in FIG. 2) opposite to a contact surface (a surface facing the lower side in FIG. 2) of the main body 11 with the CPU 20. The heat insulating member 12 plays a role of preventing the heat of the main body 11 from escaping to the outside. The heat insulating member 12 can be omitted.

  The wick 5 is a porous bottomed cylindrical member formed by sintering metal powder with a mold, and is housed in the metal tube 11a from one opening of the metal tube 11a. Further, the outside and the inside of the wick 5 communicate with each other through a fine hole. Thereby, the working fluid inside the wick 5 can be sucked outside the wick 5 by capillary action. FIG. 2 shows an example in which a member in which three wicks 5 are connected in an E shape is inserted into the metal tube 11 a of the main body 11.

  Further, on the outer periphery of each wick 5, steam discharge grooves (not shown) extending in the longitudinal direction of the wick 5 are formed at substantially equal intervals from the steam pipe side end of the wick 5 to the front of the liquid pipe side end. The A space formed between the inner wall of the metal pipe 11a and the steam discharge groove functions as a steam discharge portion that guides the vaporized working fluid to the steam pipe 3.

  The liquid inlet 14 is joined to one end of the main body 11 having one opening of the metal tube 11a. The liquid inlet part 14 has an inlet pipe 14a connected to the liquid pipe 4 (not shown in FIG. 2) of FIG. The liquid inlet section 14 divides the liquid-phase working fluid flowing in from the liquid pipe 4 into three and supplies it to the inside of the wick 5 of each evaporator 1.

  The steam outlet 13 is joined to the other end (shown by a broken line in FIG. 2) of the main body 11 having the other opening of the metal tube 11a. The steam outlet 13 has an outlet pipe 13a connected to the steam pipe 3 (not shown in FIG. 2) of FIG. The vapor outlet section 13 converges the vapor-phase working fluids respectively flowing out from the vapor discharge sections of the three evaporators 1 and sends them to the vapor pipe 3.

  As described above, the heat from the CPU 20 is conducted to the metal tube 11 a of the evaporator 1 in the evaporator unit 10. Inside each evaporator 1, the liquid-phase working fluid flowing from the liquid pipe 4 is sucked from the inside of the wick 5 to the outside by capillary force. And in the vapor | steam discharge part of the evaporator 1, the working fluid of a liquid phase evaporates with the heat | fever conducted to the metal pipe 11a. The working fluid that has been evaporated and changed to the gas phase moves to the condenser 2 via the vapor outlet 13 and the vapor pipe 3.

  FIG. 3 is a cross-sectional view schematically showing a cross section in the longitudinal direction of the evaporator example (1), which is an example of the evaporator 1 included in the evaporator unit 10. 4 is a cross-sectional view taken along the line A-A ′ of FIG. 3.

  The evaporator 1 includes a metal tube 11a, a wick 5 provided in the metal tube 11a, a seal member 15, and a liquid repellent layer 16.

  The wick 5 is arranged to divide the metal pipe 11a into a pipe on the inlet pipe 14a side and a pipe on the outlet pipe 13a side. At the outer periphery of the wick 5, the steam exhaust extending in the longitudinal direction of the wick 5 from the end of the wick 5 on the steam pipe side (exit pipe 13 a side) to the front of the end on the liquid pipe side (inlet pipe 14 a side). The grooves 5a are formed at substantially equal intervals. In this embodiment, eight steam discharge grooves 5a are provided in the wick 5 in 45 degree increments. A space formed between the inner wall of the metal pipe 11 a and the steam discharge groove 5 a functions as a steam discharge section for guiding the vapor-phase working fluid evaporated from the wick 5 to the steam pipe 3.

  The wick 5 is made of, for example, nickel sintered metal, and has an outer diameter of about 10 mm, an inner diameter of about 4 mm, a fine hole diameter of about 2 μm, and a porosity of about 50%. The groove width and groove depth of each steam discharge groove 5a is, for example, 1 mm. In addition, according to the present Example, although the vapor | steam discharge groove | channel 5a is provided in the wick side, a recessed part can also be provided in the inner wall of the metal pipe 11a, and a recessed part can also be used as a vapor | steam discharge groove.

  The seal member 15 is provided at the end of the wick 5 on the inlet tube 14a side in the metal tube 11a. When the evaporator unit 1 is assembled, the seal member 15 is provided between the side end portion of the liquid pipe of the wick 5 and the liquid inlet portion 14 to prevent the working fluid from leaking (not shown in FIG. 2). Has been inserted.

  A liquid repellent layer 16 having liquid repellency with respect to the working fluid (water) is formed at a position corresponding to the vapor discharge groove 5a on the inner wall surface of the metal tube 11a. For the liquid repellent layer 16, for example, a fluororesin film such as Teflon (registered trademark) can be used. The film thickness of the liquid repellent layer 16 is, for example, about 1 μm to 100 μm.

  Hereinafter, the operation of the evaporator example (1) will be described. When the heat generation of the CPU 20 is stopped due to the stop of the computer 1000, the circulation of the working fluid in the loop heat pipe 200 is also stopped. At this time, the working fluid may flow backward with respect to the flow direction at the time of heat input due to the influence of the thermal environment or gravity when the loop heat pipe 200 is stopped.

  However, in the example (1) of the evaporator, the liquid repellent layer 16 repels the liquid-phase working fluid in the vapor discharge groove 5 a of the evaporator 1. For this reason, the liquid-phase working fluid is less likely to enter the portion of the evaporator 1 where the liquid repellent layer 16 is formed, and vapor is generated around the liquid repellent layer 16 outside the wick 5 when the loop heat pipe 200 is not receiving heat. A pool is formed.

  Therefore, in the example (1) of the evaporator, the gas-liquid interface of the working fluid is ensured in the steam discharge portion even when the loop heat pipe 200 is not heat input. When the loop heat pipe 200 receives heat, the gas-liquid interface in the steam discharge portion serves as a core of evaporation, causing the working fluid to evaporate. Thereby, in the example (1) of the evaporator, since evaporation in the evaporator 1 is started without requiring overheating, the loop heat pipe is quickly activated after heat input, and the CPU 20 is operated when the computer 1000 is in operation. Is cooled efficiently.

  Here, FIG. 5 shows an example of the relationship between the start time of the loop heat pipe and the temperature of the evaporator when the gas-liquid interface exists outside the wick 5. FIG. 6 shows an example of the relationship between the start time of the loop heat pipe and the temperature of the evaporator when the outside of the wick 5 is filled with the liquid phase working fluid as a comparative example.

  In the case of FIG. 5, since the start-up time of the loop heat pipe is relatively short, the evaporator temperature quickly converges below the target temperature. On the other hand, in the case of FIG. 6, there is no gas-liquid interface serving as an evaporation core in the vapor discharge portion of the evaporator, and the loop heat pipe is activated after the working fluid starts to evaporate due to overheating of the evaporator. Therefore, in the example of FIG. 6, the time until the start of the loop heat pipe is longer than in the example of FIG. 5, and thus a period in which the temperature of the evaporator exceeds the specification temperature of the CPU may occur.

  FIG. 7 schematically shows a cross section in the longitudinal direction of an evaporator example (2), which is another example of the evaporator 1 included in the evaporator unit 10. FIG. 8 shows a B-B ′ cross section of FIG. 7. In addition, in the example (2) of the evaporator, the same reference numerals are given to the same components as those in the example (1) of the evaporator, and the duplicate description is omitted.

  In the example (2) of the evaporator, the liquid repellent structure 17 is disposed as a liquid repellent part in the vapor discharge groove 5a. FIG. 9 is a perspective view showing an example of the liquid repellent structure 17. In the liquid repellent structure 17, for example, a plurality of columnar bodies 17 a are arranged at substantially equal intervals at intervals of about 30 to 100 μm. The size of each columnar body 17 is, for example, about 10 μm in diameter and about several hundred μm to 1 mm in height. Furthermore, the liquid repellent structure 17 is subjected to a liquid repellent process using a film of a fluororesin such as Teflon (registered trademark).

  Here, an example of a manufacturing method of the liquid repellent structure in the example (2) of the evaporator will be described with reference to FIG.

  FIG. 10 is a cross-sectional view showing an example of a method for producing a liquid repellent structure in the evaporator example (2). In the first process shown in FIG. 10A, a resist mold 31 is formed by patterning a resist in the shape of each columnar body having a liquid repellent structure by X-ray lithography. In the second process shown in FIG. 10B, the resist mold 31 is plated with nickel, and then the resist mold 31 is removed to form a nickel mother mold 32 having the same shape as the liquid repellent structure. In the third process shown in FIG. 10C, the master mold 33 is formed by imprinting the resin on the mother mold 32 and curing the resin. In the fourth process shown in FIG. 10D, the master mold 33 is plated with copper, and then the master mold 33 is separated to obtain the electroformed structure 34. Thereafter, the electroformed structure 34 is subjected to a liquid repellent process using a fluororesin, whereby the liquid repellent structure 17 can be obtained.

  In the example (2) of the evaporator, the liquid repellent portion is formed in the evaporator 1 by the liquid repellent structure 17 in which a plurality of fine columnar bodies 17a subjected to liquid repellent processing are arranged. Since the liquid-phase working fluid does not easily enter the gap between the columnar bodies 17a in the liquid repellent part, a vapor pool is formed in the gap between the liquid repellent parts. Therefore, in the evaporator example (2), since the gas-liquid interface of the working fluid is secured in the steam discharge portion even when the loop heat pipe is not heat input, as in the case of the evaporator example (1), The loop heat pipe can be started immediately after heat input.

  FIG. 11 is a cross-sectional view showing a longitudinal section of an evaporator example (3), which is another example of the evaporator 1 included in the evaporator unit 10. In addition, in the example (2) of the evaporator, the same reference numerals are given to the same components as those in the examples (1) and (2) of the evaporator, and the duplicate description is omitted.

  In the example (3) of the evaporator, the liquid repellent structure 17 of the example (2) of the evaporator is disposed in the vapor discharge groove 5a, and the inner wall of the metal tube 11a is further provided in the same manner as in the example (1) of the evaporator. A liquid repellent layer 16 is formed on the substrate. In the example (3) of the evaporator, by having the configurations of the examples (1) and (2) of the evaporator, it becomes easier to secure the gas-liquid interface of the working fluid in the vapor discharge part. Therefore, in the example (3) of the evaporator, the loop heat pipe can be started immediately after heat input, as in the case of the examples (1) and (2) of the evaporator.

  FIG. 12 is a cross-sectional view showing a radial cross section of an evaporator example (4), which is another example of the evaporator 1 included in the evaporator unit 10. FIG. 13 is a cross-sectional view showing an example (4) of the evaporator, FIG. 13 (a) is a cross-sectional view schematically showing a cross-section along CC ′ in FIG. 12, and FIG. It is sectional drawing which shows typically the cross section in 12 DD '.

  In the evaporator example (4), the same components as those in the evaporator example (1) are denoted by the same reference numerals, and redundant description is omitted. In the example (4) of the evaporator, the inner diameter of the metal tube 11a is, for example, about 12 mm. In the example (4) of the evaporator, the outer diameter of the wick 5 is, for example, about 10 mm, and six steam discharge grooves 5a of the wick 5 are provided in increments of 60 degrees. Further, the groove width and groove depth of each steam discharge groove 5a are set to 1 mm.

  In the evaporator example (4), the liquid repellent portion 18 is formed so as to overlap the outer periphery of the wick 5. The liquid repellent part 18 is formed with a plurality of grooves (18a, 18b) that expose the surface of the wick 5. Each groove of the liquid repellent portion 18 extends in the longitudinal direction of the wick 5. The groove of the liquid repellent part 18 includes a first groove 18 a corresponding to the position of the steam discharge groove 5 a of the wick 5 and a second groove 18 b not corresponding to the position of the steam discharge groove 5 a of the wick 5.

  The liquid repellent portion 18 is formed by inserting a fluororesin cylinder such as Teflon (registered trademark) into the metal tube 11a. For example, a porous material can be used as the liquid repellent portion 18. For example, the inner diameter of the cylinder is about 10 mm and the thickness is about 1 mm.

  The liquid repellent portion 18 is formed with twelve grooves having a width of 1 mm every 30 degrees. And the liquid repellent part 18 is arrange | positioned so that six groove | channels may overlap the position of the vapor | steam discharge groove | channel 5a of the wick 5. FIG. Therefore, the groove that overlaps the position of the steam discharge groove 5a among the grooves of the liquid repellent portion 18 becomes the first groove 18a, and the groove that exposes the surface of the wick 5 without overlapping the position of the steam discharge groove 5a. Groove 18b.

  In the example (4) of the evaporator, since the liquid-phase working fluid is difficult to enter the second groove 18b of the liquid repellent portion 18, a vapor pool is formed in the space of the second groove 18b, and the wick 5 is formed. The surface becomes a gas-liquid interface. In the first groove 18a of the evaporator example (4), the liquid-phase working fluid is repelled to form a vapor pool, and the gas-liquid of the working fluid is near the boundary between the vapor discharge groove 5a and the first groove 18a. An interface is formed. Therefore, in the evaporator example (4), since the gas-liquid interface of the working fluid serving as the core of evaporation is secured on the vapor discharge side of the wick 5 even when the heat input of the loop heat pipe is not input, the loop heat pipe is After heat input, it can be activated quickly without requiring overheating.

  FIG. 14 is a cross-sectional view showing a radial cross section of the evaporator example (5), which is another example of the evaporator 1 included in the evaporator unit 10. The example (5) of the evaporator is a modification of the example (4) of the evaporator, and all the grooves of the liquid repellent part 18 are arranged so as to be shifted from the position of the vapor discharge groove 5a.

  For example, in the evaporator example (5), the steam discharge grooves 5a of the wick 5 and the grooves 18c of the liquid repellent part 18 are each formed in increments of 60 degrees. And the position of the vapor | steam discharge groove | channel 5a of the wick 5 and the position of the groove | channel 18c of the liquid repellent part 18 have shifted | deviated 30 degree | times mutually. In addition, since the other part of the example (5) of an evaporator is common in the example (4) of an evaporator, duplication description is abbreviate | omitted. In the case of the evaporator example (5), since the surface of the wick 5 becomes a gas-liquid interface in the groove 18c of the liquid repellent part 18, a loop heat pipe is inserted as in the case of the evaporator example (4). It can be activated immediately after heating.

  In examples (4) and (5) of the evaporator, for example, the liquid repellent portion 18 can be formed by applying a liquid repellent process using a fluorine resin or the like to the surface of a metal such as stainless steel. A porous metal material can also be used. Even in this case, the same effects as those of the evaporator examples (4) and (5) can be obtained.

  FIG. 15 is a cross-sectional view showing a cross section in the radial direction when the liquid repellent portion 18 is formed of a metal subjected to liquid repellent processing in the evaporator example (4). In FIG. 15, the metal portion subjected to the liquid repellent process is denoted by reference numeral 18d.

  FIG. 16 is a cross-sectional view showing a cross section of another example 1 of the evaporator unit 10. FIG. 17 is a cross-sectional view schematically showing a cross section taken along line E-E ′ of FIG. 16. In addition, in another example 1 of the evaporator unit 10, the same reference numerals are given to elements common to the example of FIG.

  In another example 1 of the evaporator unit 10 shown in FIGS. 16 and 17, the main body 11 of the evaporator unit 10 is a case. Then, one flat wick 5 is housed in the main body 11 to form the evaporator 1.

  In another example 1 of the evaporator unit 10, the main body portion 11 is formed of a stainless steel box. The wick 5 is formed of a copper sintered metal, and the width of the wick 5 (the length in the left-right direction in FIG. 16) is substantially the same as the width of the internal space of the main body 11. The dimensions of the wick 5 are, for example, a width of 30 mm and a thickness of 2 mm. The width and depth of the steam discharge groove are each 1 mm, for example. Vapor discharge grooves 5 a extending in the longitudinal direction of the wick 5 are formed on the upper surface and the lower surface of the wick 5 from the vapor pipe side end of the wick 5 to the front of the liquid pipe side end, respectively. The groove width and groove depth of each steam discharge groove is, for example, 1 mm. A gap of about 1 mm, for example, is formed between the upper and lower surfaces of the wick 5 and the main body 11.

  Further, a sheet-like polyethylene resin that forms the liquid repellent portion 19 is inserted into each of the upper and lower gaps of the wick 5. The thickness of the polyethylene resin of the liquid repellent part 19 is 1 mm. The liquid repellent portion 19 is formed with a plurality of grooves (19a, 19b) that expose the surface of the wick 5. Each groove of the liquid repellent portion 19 extends in the longitudinal direction of the wick 5. Further, the groove of the liquid repellent part 19 includes a first groove 19 a corresponding to the position of the steam discharge groove 5 a of the wick 5 and a second groove 19 b not corresponding to the position of the steam discharge groove 5 a of the wick 5. In another example 1 of the evaporator unit 10, for example, alcohol such as ethanol or methanol can be used as the working fluid of the loop heat pipe.

  In another example 1 of the evaporator unit 10 shown in FIGS. 16 and 17, as in the above example (4) of the evaporator, the working fluid gas-liquid is placed outside the wick 5 even when the loop heat pipe is not heat input. Since the interface is secured, the loop heat pipe can be started quickly after heat input.

  FIG. 18 is a cross-sectional view showing a cross section of another example 2 of the evaporator unit 10. FIG. 19 is a cross-sectional view schematically showing a cross section taken along line F-F ′ of FIG. 18. In addition, in another example 2 of the evaporator unit 10, elements that are the same as those in the first example of the evaporator unit 10 illustrated in FIGS. 16 and 17 are assigned the same reference numerals, and redundant description is omitted.

  Another example 2 of the evaporator unit 10 is a modification of the first example of the evaporator unit 10, and a sheet-like polyethylene resin that forms the liquid repellent portion 19 is disposed only on the upper side of the wick 5. In another example 2 of the evaporator unit 10, all the grooves 19c of the liquid repellent part 19 are displaced from the vapor discharge grooves 5a.

  In another example 2 of the evaporator unit 10, the gas-liquid interface of the working fluid is secured outside the wick 5 even when the loop heat pipe is not heat input, similarly to the above-described evaporator example (5). The loop heat pipe can be started immediately after heat input.

<Supplementary items of the embodiment>
Although FIG. 2 shows an example in which the evaporator unit 10 includes three cylindrical evaporators 1, the number of evaporators 1 in the evaporator unit 10 may be changed as appropriate.

  Further, in the above examples (1) to (3) of the evaporator, the liquid repellent layer 16 and the liquid repellent structure 17 may be formed using another water repellent material such as a hydrophobic silica compound. Good.

  Further, in examples (1) to (5) of the evaporator described above, the liquid repellent layer 16, the liquid repellent structure 17, and the liquid repellent portion 18 may be formed using a polyethylene resin. In the above case, alcohols can be used as the working fluid of the loop heat pipe.

  Moreover, in the other examples 1 and 2 of the evaporator unit 10 shown in FIGS. 16-19, you may form the liquid repelling part 19 using a fluororesin instead of a polyethylene resin. Alternatively, in another example 1 and another example 2 of the evaporator unit 10, as in the example of FIG. 15, the liquid repellent portion 19 may be formed by performing a liquid repellent process using a fluororesin on a metal material (in this case) (The illustration is omitted). In the above case, water can be used as the working fluid of the loop heat pipe.

  In the above description, the steam discharge groove 5a is formed in the wick 5. However, the steam discharge groove is not formed in the wick 5, but the steam discharge groove is formed on the case side of the evaporator 1. May be.

  From the above detailed description, features and advantages of the embodiments will become apparent. It is intended that the scope of the claims extend to the features and advantages of the embodiments as described above without departing from the spirit and scope of the right. Further, any person having ordinary knowledge in the technical field should be able to easily come up with any improvements and modifications, and there is no intention to limit the scope of the embodiments having the invention to those described above. It is also possible to use appropriate improvements and equivalents within the scope disclosed in.

DESCRIPTION OF SYMBOLS 1,101 ... Evaporator; 2,102 ... Condenser; 3,103 ... Steam pipe; 4,104 ... Liquid pipe; 5,105 ... Wick; 5a ... Steam discharge groove; 7 ... Fan; DESCRIPTION OF SYMBOLS ... Hollow pipe; 8a ... Serpentine part; 10 ... Evaporator unit; 11 ... Main-body part; 11a ... Metal pipe; 12 ... Thermal insulation member; 13 ... Steam outlet part; 13a ... Outlet pipe; DESCRIPTION OF SYMBOLS ... Inlet pipe; 15 ... Seal member; 16 ... Liquid repellent layer; 17 ... Liquid repellent structure; 17a ... Columnar body; 18, 19 ... Liquid repellent part; 18a-c, 19a-c ... Groove; 20 ... CPU; 21 ... Substrate; 22 ... Hard disk device; 23 ... Memory; 24 ... Power supply; 106 ... Working fluid; 200 ... Loop heat pipe;

Claims (4)

A loop heat pipe having an evaporator connected between a liquid pipe and a steam pipe,
The evaporator is
A porous body that allows the working fluid flowing in from the liquid pipe to pass through;
A housing that houses the porous body therein and forms a vapor discharge portion together with the porous body for guiding the working fluid evaporated by heat from the heating element to the steam pipe;
A loop heat pipe, comprising: a liquid repellent part disposed between the casing and the porous body, exposed to the vapor discharge part, and having liquid repellency with respect to the working fluid.   The loop heat pipe according to claim 1, wherein the liquid repellent part is formed in the vapor discharge part. The liquid repellent part is formed so as to overlap the outer periphery of the porous body,
The loop heat pipe according to claim 1, wherein a space for exposing the surface of the porous body is formed in the liquid repellent portion. A semiconductor element;
The semiconductor element is in thermal contact, and includes a loop heat pipe having an evaporator connected between a liquid pipe and a steam pipe,
The evaporator is
A porous body that allows the working fluid flowing in from the liquid pipe to pass through;
A housing that houses the porous body therein and forms a vapor discharge portion together with the porous body for guiding the working fluid evaporated by heat from the heating element to the steam pipe;
An electronic apparatus comprising: a liquid repellent part disposed between the casing and the porous body, exposed to the vapor discharge part, and having liquid repellency with respect to the working fluid.

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