JP2007107784A - Loop type heat pipe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a loop type heat pipe excellent in heat transportability. <P>SOLUTION: In this heat pipe, a porous wick 8 which permeates a working fluid 15 of liquid phase to generate capillary tube pressure is provided within a container 2 formed in an integrated manner by a vaporization part 3 connecting with a vapor pipe 6 and a liquid basin part 4 connecting with a liquid return pipe 7, and an O-ring 9 for shielding the inside of the container 2 is provided on the outer circumference of the porous wick 8 so that the internal pressure of the vaporization part 3 does not affect the internal pressure of the liquid basin part 4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a loop heat pipe in which a container that evaporates a working fluid that transports heat as latent heat and a condensing unit that condenses the vapor of the working fluid are connected by a circulation line.

  The fluid enclosed in a sealed container or pipeline is evaporated by the heat supplied from the outside, the vapor flows to a low-temperature and low-pressure location, then dissipated, and the condensed fluid is input from outside. An apparatus for transporting heat as latent heat of the fluid by recirculating to the evaporation section is conventionally known. As an example of this type of heat pipe, the inside of a pipe-shaped container is filled with a condensable fluid such as water, alcohol, or ammonia after degassing a gas such as air that does not condense at the operating temperature. There is.

  A heat pipe called a so-called thermosiphon is configured to recirculate condensed liquid-phase working fluid (liquid-phase working fluid) to the lower evaporation section by gravity, so that capillary pressure is generated as a pumping force. Although a wick is not provided, a general heat pipe is not necessarily used in the bottom heat mode where the evaporating part with heat input from the outside is on the lower side, so the liquid phase working fluid flows through the evaporating part. A wick that generates a pumping action is provided.

  Since the wick generates capillary pressure, it is preferable that the wick has a structure in which the effective capillary radius at the meniscus formed at the opening is as small as possible. ) Or the like formed on the inner surface of the metal), a bundled ultrafine wire, a porous material, or the like is used. In the part of the wick on the evaporation part side, the meniscus is lowered due to the evaporation of the working fluid, and capillary pressure is generated accordingly, so the liquid-phase working fluid is refluxed toward the evaporation part side inside the wick. . On the other hand, since the working fluid vapor (working fluid vapor) flows from the evaporating part side toward the condensing part where the working fluid condenses, the flow direction of the liquid working fluid recirculating along the wick and the working fluid The direction of steam flow is opposite to each other. For this reason, the liquid-phase working fluid is blown off or blown back by the working fluid vapor on the surface of the wick, which may become a so-called scattering limit and limit the heat transport capability of the heat pipe.

  A loop type heat pipe that can eliminate such inconvenience is known. This is configured by separating the evaporation section having heat input from the outside and the condensation section in which the working fluid dissipates heat and condenses, and a liquid flow pipe through which these liquid-phase working fluid flows toward the evaporation section; It is a heat pipe having a structure connected in a loop (loop shape) with a steam flow tube through which working fluid vapor flows. With such a structure, the liquid-phase working fluid and the working fluid vapor do not flow through the same location, and thus there is no restriction on the heat transport capability due to the scattering limit described above. Examples of this type of loop heat pipe are described in Patent Documents 1 to 3.

  The heat pipe described in Patent Document 1 includes an evaporator in which a liquid pipe (liquid return pipe) and a steam pipe are connected, and is linear in the axial direction on the inner surface of a container constituting the evaporator. A plurality of grooves are formed, and a porous ceramic is fitted in close contact with the inner surface where the grooves are formed. Therefore, in this heat pipe, the working fluid in contact with the inner peripheral surface of the container is heated and evaporated by the heat transferred to the outer peripheral surface of the evaporator, and the vapor is formed on the inner peripheral surface of the container. It flows axially through the groove and is sent out of the evaporator via a steam pipe. On the other hand, the liquid-phase working fluid is supplied from the liquid tube to the porous ceramic, that is, the wick, and since the wick is in contact with the inner surface of the container, capillary pressure is generated on the outer surface of the wick, resulting in the liquid-phase operation. Fluid is supplied to the outer surface of the wick, that is, the inner surface of the container. Then, since the liquid-phase working fluid is heated and evaporated and flows through the vapor pipe to the condensing part, heat can be transported as latent heat of the working fluid.

  Moreover, the heat pipe described in Patent Document 2 includes a wick through which the working fluid passes between the condenser side inlet and the steam pipe side outlet of the evaporator, and heats the working fluid on the condenser side than the filter. A heater is provided. Therefore, in this heat pipe, the working fluid heated by the heater wets the wick, so that dryout can be prevented. Therefore, the heat pipe can be activated and operated without reversing the posture at the time of activation under gravity (from top heat arrangement to bottom heat arrangement).

Furthermore, the heat pipe described in Patent Document 3 is provided in the middle of a buffer tank filled with a working medium, a supply pipe capable of supplying the working medium from the buffer tank into a closed loop pipe, and a supply pipe and a discharge pipe. And an operation valve, and is configured to control opening and closing of the operation valve in accordance with the amount of heat input to the heat receiving portion. Therefore, in this heat pipe, by supplying the opening and closing control of the operation valve, the filling rate is supplied so that the maximum transportation amount can be secured, and good heat transportation can be performed without drying out. On the other hand, when the amount of heat input decreases and falls within the specified value, the operating valve provided in the middle of the discharge pipe is opened and closed, and the working medium is discharged from the closed loop pipe through the discharge pipe. By returning to the filling rate, the maximum thermal conductivity can be ensured and good heat transport can be performed.
Japanese Patent Laid-Open No. 10-246583 Japanese Patent Laid-Open No. 2002-340489 JP-A-6-257969

  However, in the heat pipes described in Patent Document 1 and Patent Document 2, when the surface of the evaporator (evaporating part) is heated, heat is transmitted to the liquid pipe, and the inside of the evaporator has the same pressure ( Temperature). That is, the working fluid does not move inside the evaporator because there is no pressure difference. Further, in the heat pipe described in Patent Document 3, when the working fluid is supplied from the buffer tank into the loop type thin tube through the supply pipe, the vapor generated by the heat of the heat receiving portion is converted into the evaporator and the porous partition plate ( A so-called reverse flow phenomenon occurs, which flows through the interface with the wick and flows into the buffer tank, which may lead to a decrease in the cooling performance of the heat pipe or to an operation stop.

  For example, a wick is composed of a primary wick and a secondary wick, and a liquid return line is connected to the reservoir, which is the interior of the secondary wick. In the structure in which a reservoir and an evaporator are connected by this secondary wick, steam and bubbles (bubbles) generated by heating the evaporator surface are generated between the evaporator and the wick. There is a possibility that it flows through the interface and flows into the reservoir, leading to a decrease in the cooling performance of the heat pipe or a stoppage of operation. In addition, since this structure uses two types of wicks, a primary wick and a secondary wick, the structure is a little complicated, and steam and bubbles enter the interface between the secondary wick and the primary wick. There is also a risk that it may lead to a decrease in Furthermore, when the material of the bayonet tube that extends from the liquid return pipe into the secondary wick (primary wick) is the same material (copper, etc.) as the liquid return pipe, heat is transferred to the inside of the reservoir and the evaporator. The heat does not move between the bayonet tube and the liquid return tube. That is, the pressure difference between the inside of the reservoir and the inside of the evaporator is eliminated. Therefore, there is a possibility that the cooling performance of the heat pipe is lowered or the operation is stopped.

  The present invention has been made paying attention to the above technical problem, and an object thereof is to provide a loop heat pipe having a high heat transport capability.

  In order to achieve the above object, the invention according to claim 1 is a steam pipe comprising an evaporation section heated from the outside, a liquid storage section for storing a liquid-phase working fluid, and a condensation section for dissipating heat to the outside. A loop-type heat pipe that is communicated so as to form an annular flow path by a liquid return pipe, and in which the working fluid that is heated to evaporate and radiates and condenses is enclosed, A porous phase in which a liquid-phase working fluid is permeated into a container formed integrally by the evaporation section communicating with the vapor pipe and the liquid reservoir communicating with the liquid return pipe to generate capillary pressure. A wick is provided, and on the outer periphery of the wick, the evaporation part and the liquid reservoir inside the container are shielded from each other so that the internal pressure of the evaporation part does not affect the internal pressure of the liquid reservoir. There is a shielding part Is a heat pipe which is characterized in.

  According to a second aspect of the present invention, there is provided the heat according to the first aspect, wherein the shielding portion includes a polymer material used at a connection position between the evaporation portion and the liquid reservoir portion. It is a pipe.

  Furthermore, in the invention of claim 3, the tubular liquid flow path opened to the inside of the liquid reservoir in the invention of claim 1 or 2 is formed by a member having a lower thermal conductivity than the container. It is a heat pipe characterized by having.

  According to a fourth aspect of the present invention, there is provided a heat pipe characterized in that the evaporation section according to any one of the first to third aspects of the present invention is disposed substantially at the center toward the liquid reservoir.

  According to the first aspect of the present invention, the liquid phase working fluid is infiltrated into the container formed integrally by the evaporation portion communicating with the steam pipe and the liquid reservoir portion communicating with the liquid return pipe, thereby reducing the capillary pressure. A porous wick to be generated is provided, and on the outer periphery of the wick, there is provided a shielding part that shields the inside of the container so that the internal pressure of the evaporation part does not affect the internal pressure of the liquid reservoir. Even if steam is generated at the interface between the container and the container, the steam present in the evaporation section does not move (backflow) into the liquid reservoir. That is, the shielding portion can prevent vapor from entering from the inside of the evaporation portion to the inside of the liquid reservoir portion (so-called vapor backflow). Further, such a configuration ensures that a pressure difference (temperature difference) is generated between the internal pressure of the evaporation section and the internal pressure of the liquid reservoir, thereby preventing the cooling performance of the loop heat pipe from being deteriorated or stopped. be able to. As a result, a high heat transport capability can be maintained.

  According to the invention of claim 2, since the shielding part contains the polymer material used at the connection position of the evaporation part and the liquid reservoir part, it becomes difficult for heat from the container to be transmitted to the wick. . Therefore, it is possible to prevent the liquid-phase working fluid present in the wick from changing into a vapor phase.

  Further, according to the invention of claim 3, the tubular liquid flow path opened to the inside of the liquid reservoir is formed by the member having a lower thermal conductivity than the container, and therefore communicates with the inside of the wick. Heat becomes difficult to transfer to the tubular member. Therefore, for example, when heat is applied to the container from the outside, even if heat is transmitted from the container to the liquid flow path, an increase in the temperature or pressure inside the container (wick) can be suppressed.

  According to the fourth aspect of the present invention, since the evaporating part is disposed substantially at the center toward the liquid reservoir, a liquid-phase working fluid is always accumulated in the liquid reservoir. . Therefore, the time constant (constant indicating the temporal change) due to the heat capacity of the liquid-phase working fluid accumulated in the liquid reservoir can be used for the operation of the heat pipe.

  The best mode for carrying out the present invention will be described below. As shown in FIG. 1, a loop heat pipe 1 according to the present invention includes a container 2 in which an evaporation section 3 heated from the outside and a liquid storage section 4 for storing a liquid-phase working fluid are integrally formed, and a heat supply to the outside. The condensing part 5 that diffuses the water is communicated with the steam pipe (vapor line) 6 and the liquid return pipe (liquid line) 7 so as to form an annular flow path. The evaporator 3 and the liquid reservoir 4 are connected to a steam pipe 6 and a liquid return pipe 7, respectively.

  The container 2 is formed in a cylindrical shape, and a porous wick 8 for infiltrating a liquid-phase working fluid to generate capillary pressure is provided in the container 2. At least a part of the wick 8 is in contact with the inner surface of the container 2, and the liquid-phase working fluid that has permeated the wick 8 is supplied to the inner surface of the container 2. A steam channel extending in the axial direction is formed between the outer peripheral surface of the wick 8 and the inner peripheral surface of the container 2. This is for circulating the steam of the working fluid generated by receiving heat from the container 2, and is formed by a groove formed along the axial direction on one or both of the inner surface of the container 2 and the outer surface of the wick 8. Can be configured.

  By forming such a steam flow path or groove, the portion filled with steam inside the container 2 and the liquid reservoir 4 communicate with each other. Therefore, the porous wick 8 is used to shield these portions. An O-ring 9, which is an annular elastic member, is disposed at a location corresponding to the boundary portion between the evaporation portion 3 and the liquid reservoir portion 4. That is, this O-ring 9 is press-fitted between and shielded from a gap between the outer peripheral surface of the wick 8 and the inner peripheral surface of the container 2. Accordingly, the pressure of the evaporation unit 3 is configured not to affect the liquid reservoir 4. The O-ring 9 corresponds to the shielding part of the present invention.

  The evaporation part 3 is a cylindrical part from the outlet 2A of the container 2 to the contact part 2C between the inner peripheral surface 2B of the container 2 and the O-ring 9, and the inside is a space part 10. On the other hand, the liquid reservoir portion 4 is a cylindrical portion from the contact portion 2C to the inlet 2D of the container 2, and the inside is a space portion 11. The evaporation unit 3 has a smaller inner diameter than the liquid reservoir 4. Further, the evaporation unit 3 is disposed substantially at the center toward the liquid reservoir 4. A narrow groove 14 is formed on the inner surface of the evaporation section 3, and a vapor flow path is formed by the narrow groove 14. The evaporation part 3 has an inner diameter smaller than that of the liquid reservoir part 4, and the narrow groove 14 is not formed in the contact part 2C. The inside of the loop heat pipe 1 is almost completely degassed, and then a condensable fluid such as water or alcohol is enclosed as a working fluid 15.

  The O-ring 9 is used at the boundary position or connection position between the evaporation section 3 and the liquid reservoir section 4, and the porous wick 8 is inserted inside thereof. Therefore, the inside of the container 2 is sectioned by the O-ring 9 into the evaporator 3 and the liquid reservoir 4 and shielded from each other, and the internal pressure of the evaporator 3 does not affect the internal pressure of the liquid reservoir 4. Even if steam is generated at the interface between the porous wick 8 and the evaporation section 3 (thin groove 14), the O-ring 9 prevents the steam in the steam flow path from moving (reverse) to the space section 11. Can do. That is, it is possible to prevent the vapor from entering the space 11 from the vapor flow path (so-called vapor backflow). Further, by making the O-ring 9 a water-resistant member made of a polymer material, it is possible to prevent the heat of the contact portion 2C from being directly transmitted to the porous wick 8 at the same position. Therefore, the liquid-phase working fluid 15 is prevented from changing into vapor on the surface (interface) of the porous wick 8. That is, the O-ring 9 plays a role of a heat insulating effect at the interface with the porous wick 8.

  A hollow portion is formed in the inner peripheral direction of the porous wick 8, and the liquid return pipe 16 is inserted into the hollow portion. One end portion 8 </ b> A of the porous wick 8 protrudes into the space portion 11, and the hollow portion is opened to communicate with the space portion 11. The porous wick 8 is made of, for example, a porous material made of ceramic, nickel, copper, copper oxide or the like, or a porous material made of a polymer material such as polyethylene resin (for example, Ultra High Molecular Weight polyethylene). It is. The material of the container 2 is a metal having excellent thermal conductivity such as copper.

  The liquid return pipe 16 is a Teflon tube, a silicon tube, a glass pipe, or the like. The material of the steam pipe 6 and the liquid return pipe 7 (loop heat pipe 1) is pure copper or copper having excellent thermal conductivity. An alloy or a metal such as aluminum or nickel is employed.

  Next, the operation of the present invention will be specifically described. The loop heat pipe 1 described above can be used in a so-called top heat mode. In this case, the evaporation unit 3 to which the heat Q is transmitted from the outside is disposed at a position higher than the condensation unit 5 that radiates heat to the outside. The The amount of the working fluid 15 sealed inside is set such that the liquid level in the liquid reservoir 4 is higher than the lower end portion of the wick 8, so that the liquid-phase working fluid 15 is generated by the capillary action of the wick 8. It is supplied to the inner peripheral surface of the evaporation unit 3. More specifically, the liquid-phase working fluid penetrating the wick 8 is in contact with the inner surface of the evaporation section 3.

  The working fluid penetrating the wick 8 evaporates due to heat input from the outside to the evaporation unit 3, and the vapor fills the vapor flow path formed by the narrow grooves 14. The inside of the evaporation part 3 filled with the working fluid vapor is shielded from the liquid reservoir part 4 by the O-ring 9 described above, and the liquid-phase working fluid permeates even if the wick 8 is porous. The steam cannot be circulated. Accordingly, it is possible to prevent or suppress the working fluid vapor of the evaporation unit 3 from entering the liquid storage unit 4 or the pressure of the evaporation unit 3 from reaching the liquid storage unit 4.

  On the other hand, in the condensing part 5, since heat dissipation has occurred, the internal pressure is relatively low. Therefore, the working fluid vapor generated in the evaporation unit 3 flows toward the condensing unit 5 through the vapor pipe 6. Then, the latent heat is released to the outside and condensed.

  The other end of the liquid return pipe 7 whose one end communicates with the condensing unit 5 is inserted into the wick 8 described above, but a gap is formed between the two and the gap is formed through the gap. And communicated with the inside of the liquid reservoir 4. Accordingly, the liquid return pipe 7 substantially communicates the condensing part 5 and the liquid reservoir part 4 directly.

  In this way, one end of the condensing unit 5 communicates with the relatively high-pressure evaporator 3 via the vapor pipe 6, and the other end of the condenser 5 via the liquid return pipe 7. Since it communicates with the liquid reservoir 4, the liquid phase working fluid in the condensing unit 5 is pushed up toward the liquid reservoir 4 or sucked into the liquid reservoir 4 due to these pressure differences or energy differences. That is, the working fluid circulates between the evaporation unit 3 and the condensation unit 5 via the vapor pipe 6 and the liquid return pipe 7, and performs evaporation and condensation in the process. For 5, heat can be transported in the form of latent heat.

  In particular, in the loop heat pipe 1 according to the present invention described above, the liquid reservoir 4 provided on the same side as the evaporator 3 is shielded from the evaporator 3 so that the internal pressure of the evaporator 3 does not reach. Therefore, the liquid-phase working fluid is likely to rise against gravity, and as a result, the heat transport height in the so-called top heat mode can be made higher than before.

  The liquid phase working fluid 15 existing inside the liquid return pipe 16 flows out into the space 11 due to the capillary pressure. Here, since the evaporation unit 3 is disposed substantially in the center toward the liquid storage unit 4, the liquid phase working fluid 15 is always stored in the space 11. Therefore, the time constant (constant indicating temporal change) due to the heat capacity of the liquid-phase working fluid 15 accumulated in the space 11 can be used for the operation of the heat pipe.

  FIG. 2 shows a polymer cap 20 in a space 10A (one end 8A side of the porous wick 8) formed between the other end 8B of the porous wick 8 and the outlet 2A of the container 2. In this way, by attaching the cap 20 to the steam pipe 6 side of the container 2, for example, when the loop heat pipe 1 is started up, the liquid-phase working fluid (water) is shown. Even if 15 penetrates through the porous wick 8, it is possible to prevent the working fluid 15 from being ejected to the steam pipe 6 side.

It is a top view which shows simply the example of the loop type heat pipe of this invention. It is an enlarged view which shows the structure which attached the cap inside the evaporation part of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Loop type heat pipe, 2 ... Container, 3 ... Evaporating part, 4 ... Liquid reservoir part, 5 ... Condensing part, 6 ... Steam pipe, 7, 16 ... Liquid return pipe, 8 ... Porous wick, 9 ... O-ring 10, 11 ... space, 15 ... working fluid.

Claims (4)

An evaporation section heated from the outside, a liquid storage section for storing a liquid-phase working fluid, and a condensation section for dissipating heat to the outside are communicated so as to form an annular flow path by a steam pipe and a liquid return pipe. , A loop heat pipe in which a working fluid that is heated to evaporate and radiates and condenses is enclosed inside the annular flow path,
A porous phase in which a liquid-phase working fluid is permeated into a container formed integrally by the evaporation section communicating with the vapor pipe and the liquid reservoir communicating with the liquid return pipe to generate capillary pressure. A wick is provided, and on the outer periphery of the wick, the evaporation part and the liquid reservoir inside the container are shielded from each other so that the internal pressure of the evaporation part does not affect the internal pressure of the liquid reservoir. A loop-type heat pipe, characterized in that a shielding part is provided.   The loop heat pipe according to claim 1, wherein the shielding part includes a polymer material used at a connection position between the evaporation part and the liquid reservoir part.   The loop type heat according to claim 1 or 2, wherein the tubular liquid flow path opened to the inside of the liquid reservoir is formed by a member having a lower thermal conductivity than the container. pipe.   The loop type heat pipe according to any one of claims 1 to 3, wherein the evaporating part is disposed substantially at the center toward the liquid reservoir.

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