JP4810997B2 - Heat pipe and manufacturing method thereof - Google Patents

Description

  The present invention relates to a heat pipe that encloses a liquid such as water inside a sealed tube and transports heat using evaporation and condensation of the liquid, and a method for manufacturing the same.

  A heat pipe that transports heat by using latent heat that accompanies evaporation and condensation of liquid is a heat transfer element that has very good thermal conductivity, and is used in various fields by taking advantage of this characteristic. For example, it has been widely put into practical use as a heat dissipation device for dissipating heat generated by a computer or the like using a semiconductor device with a high degree of integration. A heat pipe can also be used as a waste heat recovery and transportation means when a heat source such as a Stirling engine is used.

  The heat pipe is manufactured by sealing water at both ends after filling the tube with water and evacuating it. Therefore, the inside of the pipe body has a saturated water vapor pressure, and the water vapor heated and evaporated at one end (evaporating part) of the pipe moves to the other end (condensing part) at a high speed, The water that has been cooled and condensed in the liquid state is moved to the heating unit again. In order to promote the reflux of water to the evaporation section, a fine cylindrical mesh body called a wick is inserted inside the heat pipe tube, for example, a metal net wound in multiple layers. Yes, the condensed water is transferred to the evaporation section using capillary action. Such a heat pipe is disclosed in, for example, Japanese Patent Application Laid-Open No. 2000-258080.

In addition to the wick made of a cylindrical mesh body, a groove type wick is also known, in which a fine groove in the axial direction is formed on the inner surface of the tube from the evaporation section to the condensation section, and water is circulated by the capillary phenomenon of this section. ing. Groove-type wicks can be installed by applying a simple process to the inner surface of the heat pipe tube, and may be used alone as a wick. It may be used in combination with a mesh wick to improve the condition.
JP 2000-258080 A

  In the evaporation part of the heat pipe, the heat from the heating source is transmitted to the water through the wall part of the tube, and the water that has absorbed the latent heat is evaporated here. On the other hand, in the condensing part, the steam releases latent heat to the cooling source through the wall part of the tube body and condenses to become liquid water. In order to improve the heat conductivity of the heat pipe and increase the amount of heat transport, it is necessary to increase the movement speed of water and water vapor as a heat transport medium and to promote heat transfer in the evaporation section and the condensation section. .

In the condensing part which is a heat transfer part, water vapor is condensed and becomes liquid water. When this water adheres to the inner surface of the pipe body, it becomes a thermal resistance that hinders heat transfer from the water vapor to the pipe body surface. That is, a steady temperature difference due to thermal resistance is generated between the tube surface and water vapor. In an ordinary heat pipe, condensed water adheres to the surface of the tube body of the condensing part in a film shape, which acts as a thermal resistance to reduce the heat radiation performance of the condensing part.
The present invention improves heat transfer in the condensing part of a heat pipe and increases the thermal conductivity of the heat pipe by increasing the moving speed of water as a heat medium. It makes it a subject to manufacture by a method.

In view of the above problems, the present invention forms a large number of grooves in the axial direction on the inner surface of the pipe body of the heat pipe and forms a water-repellent film on the inner surface other than the groove, It prevents the adhesion of water and improves heat transfer. That is, the present invention
"In a heat pipe in which water is enclosed in a sealed metal tube, and an evaporation part and a condensation part are provided at both ends of the tube,
On the inner surface of the tubular body, the evaporation section and the condensation section are connected , a plurality of grooves having a triangular shape with a tapered cross section are formed, and
At least on the inner surface of the condensing part, a coating layer having water repellency is provided on the surface other than the plurality of grooves, and in the part of the plurality of grooves, the tube extends from the condensing part to the evaporation part. The metal is exposed. ''
It is a heat pipe characterized by this.

  As a manufacturing method of the heat pipe of the present invention, as described in claim 2, after providing a coating layer having water repellency on the inner surface of the tubular body, cutting the plurality of grooves, A production method in which water is sealed in the tube body is preferable.

  In the heat pipe of the present invention, a plurality of grooves for connecting the evaporation section and the condensation section are formed on the inner surface of the tube body, and the inner surface of the condensation section has a water-repellent coating on the surface other than the plurality of grooves A layer is provided. The plurality of grooves formed on the inner surface of the tubular body function as a groove-type wick groove, and transfer water liquefied in the condensing unit to the evaporation unit by capillary action. At this time, in the condensing part, since the coating layer is provided on the portion other than the groove on the surface of the tube body and water repellency is imparted, the condensed water quickly moves to the relatively hydrophilic groove, It is possible to prevent the liquid film from forming on a portion other than the groove. Therefore, there is no thermal resistance due to the liquid film, and the heat transfer is promoted by direct contact between the water vapor and the tube of the condensing part. Here, when a liquid other than water is used as the heat medium, a coating layer for reducing the “wetting property” of the surface of the tubular body may be provided on the surface other than the groove portion.

Since the plurality of grooves having no coating layer are relatively hydrophilic, it is easy for the condensed water to flow in, and the water that has flowed in is quickly guided to the evaporation section by the capillary action of the grooves. When a water-repellent coating layer is provided on the surface other than the groove not only in the groove of the condensing part but also in the heat insulating part that is intermediate between the condensing part and the evaporation part, the water does not spread to the part other than the groove, It is smoothly transferred to the evaporator through the groove. As a result, the moving speed of water is increased and the thermal conductivity is further improved.
Incidentally, Patent Document 1 describes a technique in which a water-repellent synthetic resin coating layer is provided on the inner surface of a heat pipe tube. However, this technique is intended to improve the durability of the heat pipe, and no groove is formed on the inner surface of the heat pipe, which is completely different from the heat pipe of the present invention in terms of purpose, configuration, etc. Technology.

  When manufacturing the heat pipe of the present invention, as in the invention of claim 2, after providing a coating layer having water repellency on the inner surface of the tubular body, a plurality of grooves are cut by a simple manufacturing method. The heat pipe of the present invention can be obtained. In other words, when the groove is machined on the inner surface of the tubular body provided with the coating layer, the water-repellent coating layer is removed from the groove portion to expose the metal of the tubular body, and the surface other than the groove has water repellency. A tube body with a coating layer is produced. This method simplifies the manufacturing process and reduces the manufacturing cost compared to a method of performing a masking process or the like on a groove formed in advance and performing water-repellent processing on the remaining portion.

  Hereinafter, the heat pipe of the present invention and the manufacturing method thereof will be described with reference to the drawings. FIG. 1 shows a longitudinal sectional view and a transverse sectional view (XX cross section) of the heat pipe of the present invention, and FIG. 2 shows the difference in action and effect between the heat pipe of the present invention and the conventional heat pipe. It is explanatory drawing explaining these. Moreover, in FIG. 3, the manufacturing method of the heat pipe of this invention is shown.

  The pipe body 1 of the heat pipe of the present invention is made of a metal material having good thermal conductivity such as copper, aluminum, or stainless steel, and both ends are closed by the lid body 2 and the inside is a sealed space. Water, which is a medium for transporting heat, is enclosed in the tube body 1 and evacuation is performed to remove gas such as internal air, so that the inside of the tube body 1 is maintained at a saturated water vapor pressure. A condensing part A and an evaporating part B are arranged at both ends of the tube body 1, and an intermediate part thereof becomes a heat insulating part C. A plurality of thin grooves 3 are formed on the inner surface of the tube 1 over the entire length, as shown in the XX cross section.

The vapor generated by the heat transmitted from the heating source in the evaporation part B moves to the condensing part A at a high speed as indicated by the solid line arrow, where heat is released to the cooling source to become liquid water. The water liquefied in the condensing part A is transferred to the evaporating part B by the capillary action of the plurality of thin grooves 3 and evaporated again, and the heat of the heating source is conducted to the cooling source by repeating the same cycle. Such a configuration and operation are the same as those of a general groove type wick heat pipe.
In this embodiment, the tubular body 1 has a circular cross-sectional shape. However, depending on the purpose of use of the heat pipe and the place of use, the tubular body has various cross sections such as a rectangular cross section and a flat plate-shaped cross section. Can be adopted. Moreover, as shown by the mesh line part of FIG. 1, the wick 6 made of a mesh body can be inserted into the heat insulating part C or the like to assist the reflux of the condensed water.

  In the tubular body 1 of the present invention, a synthetic resin coating layer 4 having water repellency is provided on the inner surface of the condensing part A except for the groove 3, and water repellent processing is performed. As the synthetic resin having water repellency, for example, a fluorine resin such as polytetrafluoroethylene or a silicone resin is used. The water-repellent coating layer 4 can be provided not only on the cross section of the condensing part A but also on the inner surfaces of the heat insulating part C and the evaporation part B.

By providing the coating layer 4 of the synthetic resin having water repellency on the inner surface of the tubular body 1 other than the groove 3, in the heat pipe of the present invention, heat transfer in the condensing part A is promoted, and the condensed water is It quickly moves to the evaporation part B. This will be described with reference to FIG.
In the conventional heat pipe, as shown in FIG. 2 (b), the water liquefied by the heat radiation in the condensing part A adheres to the grooves 3 and also to the surface of the tube 1 between the grooves 3. The water adhering in the form of a film in such a state becomes a thermal resistance that inhibits heat transfer from the steam to the tube body 1. On the other hand, in the heat pipe of the present invention, since the water-repellent coating layer 4 is present on the surface of the tube 1 between the grooves 3, the liquefied water drops into the grooves 3 as shown in FIG. It adheres in a shape, and hardly adheres to the surface of the tube 1 between the grooves 3. Therefore, the heat resistance accompanying the attached liquid water is removed, heat transfer from the vapor to the tube body 1 is improved, and the liquefied water quickly flows into the relatively hydrophilic groove 3. Increase the moving speed of water, which is a heat medium.

  Subsequently, the manufacturing method of the heat pipe of this invention is demonstrated. The pipe body 1 of the heat pipe is provided with a plurality of grooves 3 acting as wicks in the axial direction. Such a pipe body can be manufactured by, for example, extrusion molding. A grooved tube is manufactured by extrusion molding, masking the groove, applying a water-repellent synthetic resin to form a coating layer, and then removing the masking to repel the surface other than the groove. The heat pipe of the present invention subjected to water processing can be obtained.

  Moreover, after forming a coating layer of a synthetic resin having water repellency on the entire inner surface of the tube 1 in advance, the groove 3 is cut to remove the coating layer of the groove portion, so that the heat pipe of the present invention is obtained. it can. That is, as shown in FIG. 3, a tube body 1 having a water repellent coating layer 4 provided on the inner surface is prepared, and the inner surface of the inner surface is provided using a broach 5 as shown by a broken line in FIG. Perform cutting. In this manufacturing method, operations such as installation and removal of masking are unnecessary, and the manufacturing process can be simplified and the manufacturing cost can be reduced.

As described above in detail, the present invention forms a large number of grooves in the axial direction on the inner surface of the tubular body, and forms a coating layer having water repellency on the inner surface other than the grooves in a heat pipe using this as a wick. It is. As a result, it is possible to prevent film-like water from adhering to the tube surface of the condensing part, improve heat transfer, and increase the heat conductivity of the heat pipe by increasing the moving speed of water as a heat medium. . In the above embodiment, a heat pipe that uses water as a heat medium is taken up, but the present invention can also be applied to a heat pipe that uses other liquids. Is provided with a coating layer that reduces the “wetting property” of the liquid as the heat medium. Thus, it is obvious that various modifications can be made to the above-described embodiment.

It is sectional drawing of the heat pipe of this invention. It is a figure explaining the effect | action of the heat pipe of this invention. It is a figure which shows the manufacturing method of the heat pipe of this invention.

Explanation of symbols

1 Tube 2 Lid 3 Groove 4 Covering Layer 5 Brooch

Claims (2)

In a heat pipe in which water is enclosed in a sealed metal tube (1), and an evaporation unit (B) and a condensation unit (A) are provided at both ends of the tube (1),
On the inner surface of the tube (1), the evaporation section (B) and the condensation section (A) are connected to each other, and a plurality of grooves (3) with a tapered section and a triangular shape are formed, and
At least the inner surface of the condensing part (A) is provided with a coating layer (4) having water repellency on the surface other than the plurality of grooves (3), and in the portions of the plurality of grooves (3), The heat pipe, wherein the metal of the tube body (1) is exposed from the condensation section (A) to the evaporation section (B) . It is a manufacturing method of the heat pipe of Claim 1, Comprising: After providing the coating layer (4) which has water repellency in the inner surface of the said pipe body (1), cutting process of these groove | channels (3) is implemented. Further, the manufacturing method is characterized in that water is sealed in the tube body (1).

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