JP4085693B2 - Heat pipe and heat pipe adapter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heat pipe, and more particularly to a heat pipe using carbon fiber reinforced carbon as a structural material.
[0002]
[Prior art]
The heat pipe can transport the heat generated from the electronic device to a radiator or heat sink to equalize the heat. An example of the internal structure of the heat pipe will be described with reference to US Pat. No. 6,184,578. 4A is an external view of the heat pipe, and FIG. 4B is a cross-sectional view thereof. The heat pipe includes a tube 15 that contains a working fluid (not shown), a long surrounding member 16 and an annular surrounding member 17 that are wound around the tube 15. The long encircling member 16 and the annular encircling member 17 are actually mounted from end to end of the tube 15, but are drawn only on the left side of the tube 15 for easy understanding of the structure. .
[0003]
A wick 14 made of a mesh-like two-layer plate is accommodated in the tube 15. The wick 14 carries the working fluid in the longitudinal direction of the tube 15 by capillary action. As the working fluid, ammonia having a pressure of 900 PSI (pounds per square inch) is used, and the thickness of the aluminum tube 15 is 0.015 inch.
[0004]
The heat pipe operates as follows. When heat is applied to the end of the heat pipe and the temperature rises, the working fluid evaporates in that part (high temperature part), and the evaporated gas moves to the low temperature part and condenses and liquefies. The liquefied working fluid moves in the wick by capillary action, reaches the high temperature portion again, and evaporates. By repeating the above process, heat is transported from the high temperature part to the low temperature part, and the temperature is made uniform at all positions of the heat pipe. Here, the temperature range indicated by the high temperature portion and the low temperature portion corresponds to the operating temperature of the working fluid.
[0005]
[Problems to be solved by the invention]
In the heat pipe, the aluminum tube 15 is reinforced from the outside by the long surrounding member 16 and the annular surrounding member 17 so that the tube 15 can withstand the high pressure of the working fluid even if the tube 15 is thin. The long surrounding member 16 and the annular surrounding member 17 are made of a carbon fiber reinforced composite material, and the outer diameter of the heat pipe can be made smaller and lighter than when the tube 15 is made of only aluminum. It is.
[0006]
Further, since the outermost surface of the heat pipe is not metal, it is easy to electrically insulate the heat pipe from the electronic device. In addition, although not described in the above-mentioned U.S. Patent, since the coefficient of thermal expansion of carbon fiber reinforced composite materials is generally smaller than that of metal materials, there is an advantage that a heat pipe having a low coefficient of thermal expansion can be obtained.
[0007]
However, in the above heat pipe, when heat from the outside is transferred to the working fluid inside the heat pipe, a large thermal resistance is generated, and the heat transfer performance of the heat pipe may be deteriorated. This is because the heat conduction characteristics of the carbon fiber reinforced composite material surrounding the outer periphery of the heat pipe are anisotropic and the heat conduction in the longitudinal direction of the fiber is good, whereas the heat conduction in the orthogonal direction of the fiber is low caused by. That is, when heat from the outside is transmitted to the working fluid inside the heat pipe, heat is transmitted so as to cross the fibers of the carbon fiber reinforced composite material surrounding the outer periphery, so that a large thermal resistance is generated.
[0008]
For example, in the above reference, THORNEL P-120 (manufactured by Union Carbide) is used as the carbon fiber constituting the carbon fiber reinforced composite material. This carbon fiber has a large thermal conductivity of 610 W / mK in the longitudinal direction of the fiber, but only has a thermal conductivity of about 3 W / mK in the direction perpendicular to the fiber. For this reason, when a carbon fiber reinforced composite material is manufactured from a carbon fiber reinforced plastic using a resin as a base material, the thermal conductivity in the thickness direction of the reinforced composite material surrounding the outer periphery of the heat pipe is about 1 W / mK. This value is considerably low considering that the thermal conductivity of the aluminum alloy that is the tube material is about 190 W / mK.
[0009]
In order to improve the heat conduction in the thickness direction of the reinforced composite material, even if the reinforced composite material is manufactured from carbon fiber reinforced carbon using carbon as a base material, the thermal conductivity does not exceed 10 W / mK. Absent. Moreover, if the metal is used as a base material with priority given to heat conduction performance, the weight of the heat pipe increases, and the meaning of manufacturing the heat pipe with a reinforced composite material is lost.
[0010]
When comparing the thermal expansion coefficients of aluminum and carbon fiber reinforced composite materials, the former is 23 ppm / K, while the latter is approximately 3 ppm / K. Since the two values differ greatly, there is a problem that when the temperature changes repeatedly in the heat pipe, peeling occurs due to thermal stress between the inner aluminum tube and the outer carbon fiber reinforced composite material, and the thermal contact is lost. is there.
[0011]
The present invention has been made to solve the above-described problems, and provides a heat pipe excellent in durability against heat cycle and heat equalization characteristics, and a heat pipe adapter that can be suitably attached to the heat pipe. For the purpose.
[0012]
[Means for Solving the Problems]
A heat pipe according to the present invention is disposed in close contact with a working fluid capable of condensing and evaporating within the operating temperature range, an airtight container containing the working fluid and having a wick on the inner wall, and the airtight container. was now provided with a reinforcing member, airtight container in shall be coated with a metal impregnated have a carbon fiber reinforced carbon, the inner surface of the metal thin film of the airtight container is impregnated metal in the gap of the carbon fiber reinforced carbon is there.
[0014]
The reinforcing member has carbon fiber reinforced carbon.
[0015]
Moreover, the carbon fiber reinforced carbon which a reinforcement member has is a thing in which the carbon fiber is orientated in the direction in alignment with the outer peripheral surface of an airtight container.
[0016]
The metal impregnated in the metal-impregnated carbon fiber reinforced carbon is copper, silver, aluminum, or silicon.
[0017]
The heat pipe adapter according to the present invention is closely connected to a working fluid capable of condensing and evaporating within the operating temperature range, an airtight container containing the working fluid and having a wick on the inner wall, and the airtight container. The airtight container includes an inner member into which a heat pipe having a metal-impregnated carbon fiber-reinforced carbon in which a metal is impregnated in a gap between carbon fiber-reinforced carbons, and both sides of the inner member. And an inner member and a skin member disposed in close contact with the end face of the honeycomb member, the inner member and the skin member having metal-impregnated carbon fiber reinforced carbon and carbon fiber reinforced carbon, respectively. It is.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1.
FIG. 1A is an external view of a heat pipe according to Embodiment 1 of the present invention. A working fluid (not shown) is sealed inside the tubular heat pipe 1 sealed at both ends. FIG.1 (b) is sectional drawing which shows the state which cut the heat pipe 1 into the ring. The airtight container 3 is made of metal-impregnated carbon fiber reinforced carbon, and a wick 4 made up of a number of grooves continuous in the longitudinal direction of the heat pipe 1 is formed on the inner surface thereof.
[0019]
The wick 4 is provided with a metal coating 5 such as nickel plating on its surface, and transports a working fluid (not shown) contained in the internal space 6 in the longitudinal direction of the heat pipe 1 by capillary action. . During operation, the pressure inside the airtight container 3 and the wick 4 becomes considerably high, so that the airtight container 3 is reinforced by the reinforcing member 2 made of carbon fiber reinforced carbon.
[0020]
The reinforcing member 2 and the airtight container 3 may be attached by fitting the two parts separately. Alternatively, a carbon fiber reinforced carbon member may be wound around a core material to be an airtight container, and the raw material may be integrally formed, and then processed into a predetermined shape.
[0021]
As the working fluid, for example, ammonia having both a liquid phase and a gas phase can be used. During operation of the heat pipe, the ammonia in the liquid phase moves between the wicks 4 by capillary action. Although the groove type wick is shown here, even if the internal space 6 is filled with a cylindrical tube, a wire mesh, fine particles, fibers, or the like, it acts effectively as a wick.
[0022]
How to make metal-impregnated carbon fiber reinforced carbon is explained. First, carbon fiber reinforced plastic is baked, and carbon fiber reinforced carbon is manufactured by carbonizing the base plastic. In the carbon fiber reinforced carbon, the base material contracts during the firing process, and a large number of voids (holes) are generated inside the base material. Next, a metal such as copper, silver, or aluminum is heated to its melting point or higher to be melted, and the molten metal is impregnated into carbon fiber reinforced carbon under a high pressure environment exceeding 100 atm. When the molten metal enters the voids inside the base material and cools, metal-impregnated carbon fiber reinforced carbon containing metal in the base material is obtained.
[0023]
Silicon may be used instead of copper, silver, or aluminum. Since silicon has a low viscosity when melted, it can be impregnated without applying pressure. Strictly speaking, silicon is a nonmetal, but in the present invention, silicon is included in the “metal” of the metal-impregnated carbon fiber reinforced carbon.
[0024]
As already mentioned, the thermal conductivity in the direction perpendicular to the fiber is about 1 W / mK in the case of carbon fiber reinforced plastic and does not exceed 10 W / mK in the case of carbon fiber reinforced carbon. By impregnating, the thermal conductivity of the metal-impregnated carbon fiber reinforced carbon is improved to exceed 50 W / mK.
[0025]
In the case of the reinforcing member 2, it is preferable from the viewpoint of heat conduction that the carbon fibers are oriented in a direction orthogonal to the outer peripheral surface of the heat pipe 1, but the carbon fibers are not broken against the pressure of the working fluid sealed inside. In order to give sufficient strength, it is desirable to arrange in a direction along the outer peripheral surface. Further, in the case of the airtight container 3, the carbon fibers of the metal-impregnated carbon fiber reinforced carbon are oriented in the longitudinal direction of the heat pipe 1 in order to enhance heat conduction in the longitudinal direction and improve the soaking characteristics of the heat pipe. If it does so, the heat conductivity of the thickness direction of the reinforcement member 2 and the airtight container 3 will exceed 50 W / mK. Since the heat conductivity in the thickness direction of the heat pipe is large, heat outside the heat pipe 1 is quickly transmitted to the working fluid inside the heat pipe.
[0026]
Since the thermal resistance between the outside of the heat pipe 1 and the working fluid is inversely proportional to the thermal conductivity of the reinforcing member 2 and the airtight container 3, in this embodiment, this thermal resistance is obtained by using carbon fiber reinforced plastic. Is about 1/50, and even less than 1/5 of the carbon fiber reinforced carbon. If a temperature imbalance of 5 ° C. has occurred in a conventional heat pipe, the temperature is improved to about 0.1 ° C. to 1 ° C.
[0027]
As the carbon fiber used for the reinforcing member 2 and the airtight container 3, for example, pitch-based carbon fiber K13C (manufactured by Mitsubishi Chemical Corporation) having a thermal conductivity in the fiber axis direction of 600 W / mK can be used. . The metal-impregnated carbon fiber reinforced carbon using the high thermal conductivity carbon fiber as a reinforcing fiber is higher in thermal conductivity than copper (thermal conductivity 390 W / mK) known as a high thermal conductivity metal in the plane in which the fibers are oriented. Have a rate.
[0028]
In the metal-impregnated carbon fiber reinforced carbon, since the pores in the carbon fiber reinforced carbon are filled with metal or silicon, leakage of the internal working fluid can be prevented while ensuring airtightness. In this embodiment, the metal coating 5 is applied to the airtight container 3 in order to further ensure the airtightness of the heat pipe. Furthermore, since the entire heat pipe is made of the same material (carbon fiber reinforced carbon), peeling hardly occurs between members. For this reason, heat transfer performance is not reduced by thermal stress generated in the heat pipe, and the reliability of the heat pipe is improved.
[0029]
Embodiment 2. FIG.
Considering the fact that a heat pipe is actually attached to an electronic device or the like, the heat pipe may be formed in a quadrangular shape in order to ensure thermal contact between the heat pipe and the electronic device. In this case, the heat pipe 1 must be thick, resulting in a large thermal resistance. In the present invention, it is of course possible to create a heat pipe having a square cross-sectional shape, but here, as shown in FIG. 2, an example of connecting to an electronic device using a heat pipe adapter 7A is shown.
[0030]
The heat pipe adapter 7A is provided with a through hole, and the heat pipe 1 is inserted into the through hole. The heat pipe adapter 7A is made of carbon fiber reinforced carbon, and the carbon fiber is oriented in the direction of the arrow 10 (direction orthogonal to the longitudinal direction of the electronic device and the heat pipe) in the member. If, for example, pitch-based carbon fiber K13C is used as the carbon fiber included in the heat pipe adapter 7A, the thermal conductivity in the direction of the arrow 10 is a value exceeding 400 W / mK. The electronic device 8 is fixed to the heat pipe adapter 7A via the heat pipe panel 9.
When the heat generated in the electronic device 8 is transmitted to the heat pipe 1, the heat transfer direction and the orientation direction of the carbon fiber of the heat pipe adapter 7A coincide with each other. However, it is lower than copper, which is a highly heat conductive metal, and the generated heat is quickly transferred to the heat pipe 1.
[0032]
Embodiment 3 FIG.
Embodiment 3 shows another form of the heat pipe adapter. As shown in FIGS. 3A and 3B, the heat pipe adapter 7 </ b> B has a sandwich panel type structure, and includes a skin member 11, a honeycomb member 12, and an inner member 13. The heat pipe 1 is fixed to the center portion of the inner member 13 by a method such as fitting or bonding.
[0033]
For example, the skin member 11 is made of carbon fiber reinforced plastic or carbon fiber reinforced carbon, the honeycomb member 12 is made of an aluminum honeycomb core, and the inner member 13 is made of metal-impregnated carbon fiber reinforced carbon.
[0034]
A sandwich panel heat pipe adapter mounted on an artificial satellite is required to have a coefficient of thermal expansion smaller than 3 ppm / K in order to guarantee the performance of the connected electronic device and optical device. Since the heat pipe adapter 7B is made of the same material (carbon fiber reinforced carbon) even if the heat pipe 1 is made of carbon fiber reinforced carbon having a small coefficient of thermal expansion, the carbon fiber reinforced plastic or carbon fiber is used. It can prevent that the thermal stress generate | occur | produces and breaks in the skin member 11 in which reinforced carbon is used.
[0035]
On the other hand, when a metal heat pipe is embedded in the inner member 13 instead of the heat pipe 1 according to the present invention, a large thermal stress is generated in the skin due to the difference in thermal expansion coefficient between the heat pipe 1 and the skin member 11. As a result, the skin member 11 may be damaged.
[0036]
【The invention's effect】
A heat pipe according to the present invention is disposed in close contact with a working fluid capable of condensing and evaporating within the operating temperature range, an airtight container containing the working fluid and having a wick on the inner wall, and the airtight container. be provided with a reinforcing member, airtight container have a metal-impregnated carbon fiber reinforced carbon which is impregnated with a metal in the gap of the carbon fiber reinforced carbon, the inner surface of the airtight container by Rukoto covered with a metal thin film It has excellent soaking properties and high airtightness.
[0038]
Further, the reinforcing member is made of carbon fiber reinforced carbon, so that a light and high strength member can be obtained.
[0039]
Moreover, the carbon fiber reinforced carbon which a reinforcement member has has high intensity | strength because carbon fiber orientates in the direction in alignment with the outer peripheral surface of an airtight container.
[0040]
Moreover, the metal impregnated in the metal-impregnated carbon fiber reinforced carbon is copper, silver, aluminum, or silicon, and thus has high thermal conductivity.
[0041]
The heat pipe adapter according to the present invention is closely connected to a working fluid capable of condensing and evaporating within the operating temperature range, an airtight container containing the working fluid and having a wick on the inner wall, and the airtight container. The airtight container includes an inner member into which a heat pipe having a metal-impregnated carbon fiber-reinforced carbon in which a metal is impregnated in a gap between carbon fiber-reinforced carbons, and both sides of the inner member. And the inner member and the skin member disposed in close contact with the end face of the honeycomb member, and the inner member and the skin member have metal-impregnated carbon fiber reinforced carbon and carbon fiber reinforced carbon, respectively. Therefore, thermal conductivity is high.
[Brief description of the drawings]
FIG. 1 is a view showing an appearance and an internal structure of a heat pipe according to the present invention.
FIG. 2 is a view for explaining the structure of a heat pipe adapter 7A for connecting a heat pipe and an electronic device.
FIGS. 3A and 3B are a perspective view and a cross-sectional view for explaining the structure of a heat pipe adapter 7B. FIGS.
FIG. 4 is a view for explaining a heat pipe disclosed in US Pat. No. 6,184,578.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Heat pipe, 2 Reinforcement member, 3 Airtight container, 4 Wick, 5 Metal film, 6 Internal space, 7A, 7B Heat pipe adapter, 11 Skin member, 12 Honeycomb member, 13 Inner member

Claims (5)

A working fluid capable of condensing and evaporating within a range of operating temperature; an airtight container containing the working fluid and having a wick on an inner wall; and a reinforcing member disposed in close contact with the airtight container becomes, the airtight container have a metal-impregnated carbon fiber reinforced carbon which is impregnated with a metal in the gap of the carbon fiber reinforced carbon, the inner surface of the airtight container is characterized that you have been coated with a metal thin film heat pipe.   The heat pipe according to claim 1, wherein the reinforcing member has carbon fiber reinforced carbon. The heat pipe according to claim 2, wherein the carbon fiber reinforced carbon included in the reinforcing member is oriented in a direction along the outer peripheral surface of the airtight container.   The heat pipe according to claim 1, wherein the metal impregnated in the metal-impregnated carbon fiber reinforced carbon is copper, silver, aluminum, or silicon. A working fluid capable of condensing and evaporating within a range of operating temperature; an airtight container containing the working fluid and having a wick on an inner wall; and a reinforcing member disposed in close contact with the airtight container The airtight container is a heat pipe adapter for loading a heat pipe having a metal-impregnated carbon fiber-reinforced carbon in which a metal is impregnated in a gap between carbon fiber-reinforced carbon, and an inner member into which the heat pipe can be inserted; A honeycomb member disposed on both sides of the inner member, and a skin member disposed in close contact with the inner member and an end surface of the honeycomb member, wherein the inner member and the skin member are each a metal-impregnated carbon fiber. A heat pipe adapter comprising reinforced carbon and carbon fiber reinforced carbon.

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