JP2012042115A - Loop-type heat pipe and electronic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a loop-type heat pipe excellent in stable operation and heat transport capacity and an electronic equipment having the same.SOLUTION: The loop-type heat pipe includes: an evaporation part for evaporating an operating fluid by receiving heat from the outside; a first condensation part for condensing vapor of the operating fluid by radiating heat outside; a second condensation part connected in series with the first condensation part at a side near a steam pipe thorough which the vapor from the evaporation part passes, which condenses the vapor of the operating fluid by radiating heat outside; a steam passage opening/closing mechanism arranged before and behind the second condensation part, which opens and closes the steam passage according to a predetermined temperature; and a bypass pipe for bypassing the vapor of the operating fluid in the steam pipe when the steam passage opening/closing mechanism is closed.

Description

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

  In recent years, the heat generation amount and heat generation density of electronic devices such as computers have increased, and improvement in cooling performance has been demanded. For this reason, there is a wide range of methods in which a heat sink is disposed in a location suitable for cooling, such as in the vicinity of a cooling fan, and an electronic component having a large amount of heat, such as a CPU (Central Processing Unit), and the heat sink are thermally connected by a heat pipe for cooling. It is used.

  Conventionally, as a heat pipe for thermally connecting a heat sink and an electronic component, a single-tube heat pipe having a simple structure has been used. However, the heat transport capacity of the single tube heat pipe is as low as about 30 to 50 W, which is not sufficient for cooling the electronic device.

  On the other hand, a loop heat pipe (LHP) has an excellent heat transport capability as compared with a single tube heat pipe, and therefore, development aimed at mounting on an electronic device is underway.

  As illustrated in FIG. 6, the LHP 10 includes an evaporation unit 12 that evaporates working fluid (liquid phase working fluid), a condensing unit 14 that condenses steam (gas phase working fluid), and a working fluid supplied to the evaporation unit. And an auxiliary chamber 11 for temporarily storing the. The evaporating unit 12 and the condensing unit 14 are connected by a steam pipe 13 that guides the steam, and the condensing unit 14 and the auxiliary chamber 11 are connected by a liquid pipe 15 that guides the working fluid. In addition, a porous member called a wick 17 is provided inside the evaporation section 12 to separate the working fluid flow path communicating with the liquid pipe 15 and the vapor flow path communicating with the steam pipe 13. The wick 17 has a function of sucking up the hydraulic fluid in the hydraulic fluid flow path with a capillary force and transporting it to the vapor flow path side, and a function of preventing the vapor in the vapor flow path from flowing backward to the hydraulic fluid flow path side. The working fluid is circulated between the section 12 and the condenser section 14.

JP 2009-168273 A JP 2009-115396 A Japanese Patent Laid-Open No. 2002-340489

  However, since the CPU of the electronic computer operates by changing the calculation load, the LHP condensing unit needs a heat radiation area corresponding to the heat generation amount. In the conventional LHP, the heat radiation area of the condensing part is designed so that the maximum heat generation amount can be dissipated. Therefore, when the heat generation amount is small, condensation occurs near the steam pipe, and the flow resistance of the working fluid increases. As a result of the circulation being stopped, there is a problem that the LHP does not operate.

  Therefore, in order to solve the above-described problem, the present invention provides a loop heat pipe that operates stably even if the calorific value fluctuates and has an excellent heat transport capability.

  According to one aspect of the present invention, an evaporation unit that receives heat from the outside and evaporates the working fluid, a first condensing unit that radiates heat to the outside and condenses the vapor of the working fluid, and a vapor from the evaporation unit Is connected in series with the first condensing unit on the steam pipe side through which the gas passes, and is installed at the second condensing unit for radiating heat to the outside and condensing the vapor of the working fluid, and at the inlet or the outlet of the second condensing unit A steam passage opening / closing mechanism that controls a passage amount of the steam according to a predetermined temperature, and a bypass pipe that sends the steam of the working fluid to the first condensing unit without passing through the second condensing unit. The present invention relates to a loop heat pipe.

  According to the present invention, when the temperature of an electronic component to be cooled is low by installing a temperature variable opening / closing valve at the inlet or outlet of the condenser on the steam pipe side, in which the condenser is divided in series, A loop heat pipe that operates stably and has excellent heat transport capability is realized.

It is a figure explaining the basic composition of the loop type heat pipe which becomes an embodiment of the invention, and its operation. It is a figure explaining the structure of the polymer valve installed in the vapor | steam passage before and behind the fragmentation condensation part which becomes embodiment of this invention, and its behavior. It is a figure which shows the relationship between the polymer valve opening degree which becomes embodiment of this invention, and the emitted-heat amount. It is a figure which shows the structure (sectional drawing) of the structure of the loop type heat pipe which becomes embodiment of this invention, and a principal part. It is a figure which shows the electronic device carrying the loop type heat pipe which becomes embodiment of this invention. It is a figure which shows the structural example of the conventional loop type heat pipe.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram for explaining the basic configuration and operation of a loop heat pipe of the present invention. The loop heat pipe 10 includes an evaporating unit 12 that receives heat from the outside and evaporates the working fluid, and a condensing unit 14 that radiates heat to the outside and condenses the vapor of the working fluid.

  The LHP 10 includes an auxiliary chamber 11 that stores hydraulic fluid to be supplied to the evaporator 12, a vapor pipe 13 that guides the vapor of hydraulic fluid generated in the evaporator 12 to the condenser 14, and an operation that is condensed in the condenser 14. A liquid pipe 15 for guiding the liquid to the auxiliary chamber 11 is provided. Further, the steam pipe 13 has a wick 17 made of a porous material that is disposed in the steam pipe and separates the working fluid flow path communicating with the auxiliary chamber 11 and the steam flow path communicating with the steam pipe 13.

  Further, the condensing unit 14 is installed in front of and behind the divided condensing units 14a and 14b divided in series and the condensing unit (14a) on the side close to the steam pipe 13, and opens and closes the working vapor liquid passage. 30 and a bypass pipe 31 that bypasses the steam that is blocked from being input to the split condenser 14a. Although not shown, the condensing unit 14 and the divided condensing units 14a and 14b include a tube having the same diameter as the condensing tube 13 and the liquid tube 15 and a radiating fin for cooling the tube around the tube. It has a structure. Further, a cooling fan (not shown) that blows and cools the radiating fins is provided in the vicinity of the condensing unit.

  The polymer valve 30 is made of a polymer material that absorbs vapor liquid when the temperature is lower than a predetermined temperature and expands to close the vapor passage, and contracts when the temperature is higher than the predetermined temperature to open the vapor passage. Applied. In addition, the valve | bulb of the back part of the division | segmentation condensation part 14a is for preventing a backflow. In addition, in the Example, although the condensation part 14 was shown in the example divided | segmented into two, you may divide | segment into two or more.

  The operating principle of the loop heat pipe of the present invention will be described below.

  When the calorific value is small (or when the operation is started), the polymer valve 30 is in a “closed” state, and the vapor passes through the bypass pipe 31 of the split condenser 14a and is liquefied in the condenser 14b. On the other hand, when the calorific value is large, the polymer valve 30 is in the “open” state and is liquefied in both the divided condensing unit 14a and the divided condensing unit 14b.

As a condition for fluid to flow to the condensing part when the valve is “open”, the magnitude relationship between the pressure loss resistance of the bypass pipe 31 and the divided condensing part 14a is
If the relationship of resistance of the bypass pipe> resistance of the condensing part is satisfied, the fluid passes through the divided condensing part 14a.

  In the embodiment, the inner diameters of the bypass pipe 31 (inner diameter d1) and the flow path pipe (inner diameter d2) of the divided condenser section 14a are d1 = 2 mm and d2 = 4 mm, respectively, and the length of the bypass pipe 31 is the divided condenser section. More than three times the length of the channel pipe of 14a.

  As a material used for the polymer valve 30, it is preferable to apply a temperature-responsive polymer having a property of gradually contracting with respect to temperature.

  As described above, the condensing unit is divided in series, and the opening and closing mechanism of the flow path by the polymer valve and the bypass pipe are arranged before and after the divided condensing unit on the side close to the steam pipe, so that the loop heat pipe corresponding to the heat generation amount can be obtained. Realized.

  FIG. 2 is a diagram for explaining the behavior of the polymer valve installed in the steam passages before and after the divided condensing unit of the present invention. FIG. 2A shows a configuration example of the polymer valve, and FIG. 2B shows the behavior of the temperature-responsive polymer applied to the polymer valve.

  As shown in FIG. 2A, the polymer valve 30 includes an absorption layer (temperature-responsive polymer) 30 a and a support layer 30 b attached to the frame body 40, and flows from the steam pipe 13 to the condensing unit 14. Control the passage of steam.

  The support layer 30a is made of a material having low chemical reactivity and solubility with respect to the working fluid 16, such as a nonwoven fabric made of polypropylene. In addition, the material of the support layer 30a is not limited to this, For example, metal materials, such as platinum, platinum black, gold | metal | money, palladium, rhodium, silver, mercury, tungsten and copper, or these alloys, Carbon materials such as graphite and carbon fiber, semiconductor materials such as single crystal silicon, amorphous silicon, silicon carbide, silicon oxide, silicon nitride, and SOI (silicon on insulator), glass, quartz glass, alumina, sapphire, various ceramics, Inorganic materials such as forsterite and photosensitive glass, and various polymer materials can be used.

  The absorption layer 30b is made of a resin material that absorbs the hydraulic fluid at a temperature lower than a predetermined phase transition temperature and expands, and releases the hydraulic fluid at a temperature higher than the phase transition temperature to contract. Here, poly N-isopropylacrylamide, which is a kind of temperature-responsive polymer that absorbs and releases the working fluid depending on the temperature, is used for the absorption layer 30b.

  The absorption layer 30b is chemically bonded on the surface of the support layer 30a in order to prevent it from dissolving and disappearing in the working fluid. When a polymer material is used as the support layer 30a, the surface of the support layer 30a and the polymer constituting the absorption layer 30b are graft-bonded.

  FIG. 2B shows a working fluid caused by expansion / contraction of a temperature-responsive polymer applied as a valve when the temperature of an object to be cooled (CPU or the like) is low or when the temperature of the object to be cooled is high. Each of these states is schematically shown.

  As shown in FIG. 2B, when the object to be cooled is at a low temperature, the polymer chain swells and the valve is closed, and when the vapor passes through the bypass pipe 31 and is at a high temperature, the polymer is The chain contracts, the valve is opened, and the vapor passes through a plurality of condensing parts. That is, when the LHP 10 operates, the temperature of the condenser rises, and the opening and closing of the valve before and after the condensing part is performed by utilizing the property that the polymer contracts at a predetermined temperature (= phase transition temperature) or higher, so that the LHP 10 when the calorific value is different. Can be operated stably.

  The polymer valve 30 is made of a resin material that expands by absorbing a working fluid at a temperature lower than a predetermined phase transition temperature, while releasing the working fluid at a temperature higher than the phase transition temperature. Here, poly-N-isopropylacrylamide, which is a kind of temperature-responsive polymer that absorbs and releases the working fluid depending on the temperature, is used.

  Poly-N-isopropylacrylamide has a phase transition temperature of about 32 ° C., and at a temperature higher than 32 ° C., the acrylamide portion of the side chain is dehydrated and the polymer chain contracts to reduce its volume. Further, at a temperature lower than 32 ° C., the acrylamide portion of the side chain absorbs moisture and the molecular chain expands, increasing its volume.

  The temperature-responsive polymer used for the polymer valve 30 is not limited to the above-described example. For example, poly (N-substituted acrylamide), poly (N-substituted methacrylamide), poly (N, N-disubstituted acrylamide), poly (N, N-disubstituted methacrylamide), polyvinyl ether (which may be partially substituted), and the like can be used. Here, the substituent of the above-described material is a linear or branched alkyl group having 1 to 20 carbon atoms, more preferably 1 to 6 carbon atoms, and a cyclohexane having 3 to 20 carbon atoms, more preferably 3 to 10 carbon atoms. It shall be selected from any one or more of alkyl groups.

  More specifically, poly (N-methylacrylamide), poly (N-ethylacrylamide), poly (N-cyclopropylacrylamide), poly (N-isopropylacrylamide), poly (Nn-propylacrylamide), N-methyl-N-ethylacrylamide, N-methyl-N-isopropylacrylamide, N-methyl-Nn-propylacrylamide, N, N-dimethylacrylamide, N, N-diethylacrylamide, poly (N-methylmethacrylamide) ), Poly (N-ethylmethacrylamide), poly (N-cyclopropylmethacrylamide), poly (N-isopropylmethacrylamide), poly (Nn-propylmethacrylamide), N-methyl-N-ethylmethacrylamide N-methyl-N-isopropylmeta Riruamido, N- methyl -N-n-propyl methacrylamide, N, N- dimethyl methacrylamide, N, N- diethyl methacrylamide, polyvinyl methyl ether and polyvinyl ether or the like can be used in the absorbent layer 30b.

  Further, not only the above-described polymer homopolymer, but also a copolymer obtained by combining two or more types of monomers constituting the polymer, or other types of monomers and monomers contained in the polymer described above. A combined copolymer may be used. In addition, any one of the above polymers may be used alone, or a plurality of types may be used in combination.

  The polymer valve 30 can be manufactured as follows. Here, an example in which a polypropylene nonwoven fabric is used as the support layer 30a and poly-N-isopropylacrylamide is graft-bonded to the surface of the support layer 30a as the temperature-responsive polymer of the absorption layer 30b will be described.

  First, as the support layer 30a, for example, a polypropylene nonwoven fabric having an average pore diameter of about 10 μm is prepared. Next, the surface of the support layer 30a is irradiated with plasma in an argon atmosphere to generate active species on the surface of the support layer 30a. The method of generating active species on the surface of the support layer 30a may be performed by radiation irradiation, electron beam irradiation, or the like in addition to plasma irradiation.

  Thereafter, the support layer 30a is immersed in a degassed 3% N-isopropylacrylamide aqueous solution having a temperature of about 60 ° C. Thereby, N-isopropylacrylamide is polymerized on the support layer 30a using the active species on the surface of the support layer 30a as a starting point, thereby forming an absorption layer 30b grafted to the support layer 30a.

  Next, the support layer 30a and the absorption layer 30b are taken out from the 3% N-isopropylacrylamide aqueous solution, washed with, for example, a washing solution in which water and methanol are mixed at a ratio of 1: 1, and vacuum dried. The polymer valve 30 of this embodiment is completed by laminating a plurality of support layers 30a and absorption layers 30b produced as described above.

  Instead of the method of generating active species on the surface of the support layer 30a described above, a functional group that reacts with the functional group can be generated by reacting the surface of the support layer 30a with a chemical treatment to generate a reactive functional group. A temperature-responsive polymer having In this case, the functional groups generated on the surface of the support layer 30a include carboxyl group, aldehyde group, amino group, imino group, sulfonic acid group, epoxy group, isocyanate group, acid chloride group, hydroxy group, thiol group, and disulfide. Groups and the like. Further, instead of subjecting the support layer 30a to chemical treatment, the support layer 30a may be formed of a polymer material having any of the functional groups listed above.

  FIG. 3 is a diagram showing the relationship between the opening degree of the polymer valve of the present invention and the calorific value. FIG. 3 is a graph in which the heat generation amount W is plotted on the horizontal axis and the valve opening degree (%) is plotted on the vertical axis, regarding the opening and closing performance of the valve when poly N-isopropylacrylamide is used as the polymer valve 30.

  As shown in FIG. 3, when the heating value is small, the opening of the polymer valve 30 is 0% at 30 W or less, and when the heating value is 30 W or more, the polymer valve 30 starts to open when the heating value is 30 W or less. The opening degree of the valve is 50%, and the opening degree of the polymer valve 30 is 100% at 50 W or more.

  FIG. 4 shows the structure of the loop heat pipe of the present invention and the structure (sectional view) of the main part. 4A shows the overall configuration of the loop heat pipe 10, FIG. 4B shows the cross-sectional structure of the evaporation unit 12 and the auxiliary chamber 11, and FIG. 4C shows the condensing unit 14. A cross-sectional structure is shown.

  As shown in FIG. 4A, the loop heat pipe 10 of this embodiment includes an auxiliary chamber 11, an evaporation unit 12, a vapor pipe 13, a condensing unit 14, and a liquid pipe 15. The liquid 16 is enclosed together with steam having a saturated vapor pressure. Here, water is used as the working fluid 16, but methanol, ethanol, or the like may be used.

  As shown in FIG. 4B, the auxiliary chamber 11 is disposed adjacent to the evaporation unit 12 and temporarily stores the working fluid 16 supplied to the evaporation unit 12.

  Further, the evaporation unit 12 includes a heat block 20, an evaporation tube 21, and a wick 17. The heat block 20 is a metal box filled with contents. The heat block 20 diffuses heat received from the outside throughout the heat block 20. An electronic component 85 is joined to the heat block 20 via thermal grease (not shown) or the like.

  A cylindrical evaporation tube 21 is accommodated in the center of the heat block 21. The evaporation pipe 21 is made of, for example, a copper pipe or the like, and a plurality of groove-like steam flow paths (grooves) 21 a extending in a direction parallel to the central axis of the evaporation pipe 21 are formed on the inner peripheral side thereof. These steam flow paths 21 a communicate with the steam pipe 13 via the steam converging part 23.

  The wick 17 is a tubular porous member whose end on the steam tube 13 side is closed, and the outer peripheral surface of the wick 17 is in contact with the inner peripheral surface of the evaporation tube 21 (excluding the steam channel 21a). 21. A hollow portion on the inner peripheral side of the wick 17 serves as a hydraulic fluid channel 17 a, and the hydraulic fluid channel 17 a communicates with the auxiliary chamber 11. The hydraulic fluid channel 17 a is separated from the vapor channel 21 a by the wick 17.

  The steam pipe 13 connects the evaporator 12 and the condenser 14, and guides the steam generated in the evaporator 21 of the evaporator 12 to the condenser 14. The condensing unit 14 includes a heat sink (not shown), and heat is radiated by the heat sink to condense the vapor and generate the working fluid 16. The liquid pipe 15 connects the condensing unit 14 and the auxiliary chamber 11, and guides the working fluid 16 generated in the condensing unit 14 to the auxiliary chamber 11.

  As shown in FIG. 4C, the condensing unit 14 is divided in series, and a polymer valve 30 is installed as a temperature-responsive opening / closing valve before and after the divided condensing unit 14a on the side close to the steam pipe. The When the polymer valve 30 reaches a temperature lower than a predetermined temperature, it absorbs the vapor liquid and expands, closes the vapor passage, and bypasses the vapor to the bypass pipe 31 provided separately. Further, when the temperature becomes higher than the predetermined temperature, it contracts to open the vapor passage and pass through the divided condensing parts 14a and 14b. Thus, the polymer valve 30 plays a role as an opening / closing mechanism of the working vapor liquid passage.

  Further, the operation of the loop heat pipe 10 will be described below with reference to FIGS. 4 (a), 4 (b), and 4 (c).

  When power is supplied to the electronic component (for example, CPU) 85, heat is transmitted from the outer peripheral side of the wick 17 through the heat block 20 and the evaporation tube 21, and the working fluid 16 evaporates on the outer peripheral side of the wick 17. At this time, since the holes of the wick 17 are blocked by the hydraulic fluid 16, the generated vapor cannot pass through the holes of the wick 17 and flow backward to the hydraulic fluid channel 17a. The concentration difference becomes a driving force due to the evaporation of the working fluid on the outer peripheral side of the wick 17, and the liquid is supplied from the working fluid flow path 17 a side. The working fluid circulates in the loop heat pipe 10, and the loop heat pipe 10 starts. To do.

  During operation of the loop heat pipe 10, the working fluid 16 flows into the auxiliary chamber 11 through the liquid pipe 15. The hydraulic fluid 16 that has moved into the hydraulic fluid flow path 17 a is carried to the outer peripheral side of the wick 17 by the capillary force of the wick 17, and is heated on the heat block 20 to evaporate on the outer peripheral side of the wick 17. The steam generated on the outer peripheral side of the wick 17 is collected in the steam converging part 23 through the steam flow path 21 a and then flows out from the evaporation part 12. The vapor that has flowed out of the evaporation unit 12 is guided to the condensing unit 14 by the vapor pipe 13, is condensed by the condensing unit 14, and returns to the working liquid 16. Thereafter, the working fluid 16 generated in the condensing unit 14 is pushed up in the liquid pipe 15 by the pressure difference between the vapor passage 21 a and the working fluid passage 17 a and moves into the auxiliary chamber 11.

  As described above, the loop heat pipe 10 circulates the working fluid while repeating evaporation and condensation, thereby transporting the heat on the evaporation unit 12 side to the condensation unit 14 side.

  As described above, the loop heat pipe 10 according to the present embodiment absorbs moisture at a temperature lower than the phase transition temperature before and after the condenser and releases moisture at a temperature higher than the phase transition temperature. A temperature-responsive opening / closing valve is provided. With such a configuration, the loop heat pipe 10 can change the vapor phase into a liquid in a designated condensing unit according to the amount of heat generated by the computer, and can be stably operated. The loop heat pipe 10 is also excellent in heat transport characteristics.

  FIG. 5 shows an electronic apparatus equipped with the loop heat pipe of the present invention.

  As shown in FIG. 5, an electronic device (computer) 80 includes an electronic component 85 having a large heat generation amount such as a CPU, a wiring board 81 on which the electronic component 85 is mounted, a cooling fan 82 for taking in outside air, and an auxiliary device. An HDD (hard disk drive) 83 as a storage device and a power supply unit 84 are included. The loop heat pipe 10 is mounted on the wiring board 81, and the capacitor tube 14 (and the heat sink) is disposed in the vicinity of the cooling fan 82. The evaporation unit 12 of the loop heat pipe 10 is joined to the upper surface of the electronic component 85 via thermal grease (not shown).

  By applying the loop heat pipe 10 configured as described above, the electronic device 80 has a high heat transport capability, and thus can be efficiently cooled. Further, it is expected that the air volume of the cooling fan 82 is suppressed to reduce the noise of the electronic device 80 and to suppress the driving power of the cooling fan 82.

  The present invention is applied to the technical field of loop heat pipes and electronic devices using the same.

DESCRIPTION OF SYMBOLS 10 Loop type heat pipe 11 Auxiliary chamber 12 Evaporating part 13 Steam pipe 14 Condenser pipe (condensing part)
DESCRIPTION OF SYMBOLS 15 Liquid pipe 16 Hydraulic fluid 17 Wick 17a Hydraulic fluid flow path 20 Heat block 20a Cavity part 21 Evaporation pipe 21a Steam flow path 23 Steam condensing part 80 Electronic device 81 Wiring board 82 Cooling fan 83 HDD (hard disk drive)
84 Power supply 85 Electronic parts

Claims (5)

An evaporating section that receives heat from outside and evaporates the working fluid;
A first condensing part that radiates heat to the outside and condenses the vapor of the hydraulic fluid;
A second condensing unit connected in series with the first condensing unit on the vapor pipe side through which the vapor from the evaporating unit passes, and radiating heat to the outside to condense the vapor of the working fluid;
A steam passage opening / closing mechanism that is installed at an inlet or an outlet of the second condensing unit and controls a passage amount of steam according to a predetermined temperature;
A bypass pipe for sending the vapor of the working fluid to the first condensing unit without passing through the second condensing unit;
A loop-type heat pipe characterized by comprising:   2. The loop heat pipe according to claim 1, wherein a member used for the steam passage opening / closing mechanism includes a temperature-responsive polymer that expands or contracts with a phase transition temperature as a boundary.   The member used for the steam passage opening / closing mechanism has a structure in which a plurality of support layers made of a material that does not dissolve in the hydraulic fluid and a plurality of absorption layers made of the temperature-responsive polymer are laminated. Loop type heat pipe described in 1.   The temperature-responsive polymer is a homopolymer of any one of poly N-substituted acrylamide, poly N-substituted methacrylamide, poly NN-2 substituted acrylamide, poly NN-2 substituted methacrylamide, and polyvinyl ether, or these The loop heat pipe according to claim 2 or 3, comprising a copolymer.   5. An electronic device equipped with the loop heat pipe according to claim 1, wherein a condensing unit that radiates heat to the outside and condenses the vapor of the working fluid is thermally coupled with an electronic component that generates heat. An electronic device characterized by being connected.