JPS6136155B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a leaded heat pipe that facilitates terminal processing and has a long service life, and a method for manufacturing the same.

In general, heat exchangers for waste heat recovery using heat pipes have the heat absorption side of the heat pipe placed inside a duct where high-temperature waste gas flows, and the heat radiation side of the heat pipe placed inside a duct where clean air or low-temperature gas flows. The waste heat is recovered by utilizing the rapid heat transfer effect of heat pipes.

However, when fuel oil containing sulfur is used, the combustion gas contains sulfur oxides (SOx),
When this waste gas comes into contact with the heat pipe and its temperature drops below the sulfuric acid dew point, sulfuric acid is produced on the surface, which causes corrosion.

For this reason, the present inventors have previously developed and proposed a lead-covered heat pipe whose outer tube is coated with lead or a lead alloy that has excellent sulfuric acid dew point corrosion resistance. As shown in Figure 1, this leaded heat pipe has an outer tube 3 made of lead or a lead alloy coated with good adhesion around the outer periphery of a heat pipe 2, which serves as an inner tube 1, and both ends of the lead outer tube 3 are drawn. It has a structure in which it is molded into a hemispherical shape and the small holes are sealed.

However, in the lead-covered heat pipe having the above structure, a space between both ends of the heat pipe 2 serving as the inner pipe 1 and both ends of the lead outer pipe 3 becomes hollow, and an air layer 4 is formed. For this reason, the end is vulnerable to external pressure, and in particular, the end opposite to the sealing section 5 side is often installed in a heat exchanger with the end facing downward, so it is not easily deformed or damaged by external pressure. easy. In addition, this air layer 4 repeatedly expands and contracts due to temperature changes, and in particular, the side opposite to the sealing section 5 is often placed on the endothermic side in contact with high-pressure waste gas, so the temperature changes rapidly and stress is applied repeatedly. As a result, fatigue cracks may occur, and once cracks occur, there is a risk that corrosive gas will enter the heat pipe 2 and corrode the heat pipe 2. In addition, since the air layer 4 is formed, there is a risk of drawing defects during the drawing process of the end portion, resulting in disadvantages such as poor workability.

As a result of various studies in view of the above, the present invention has excellent end processability of lead outer tubes, increases the strength of the ends, and eliminates air layers to prevent fatigue deterioration caused by expansion and contraction. We have developed a leaded heat pipe that prevents corrosion and extends its life, as well as a method for manufacturing the same.

That is, the present invention provides a lead-coated heat pipe in which an outer tube made of lead or a lead alloy is coated with lead with good adhesion around the outer periphery of the heat pipe, and both ends of the lead outer tube are tightly vibrated. A first leaded heat pipe characterized in that a substantially hemispherical block is inserted between at least the end opposite to the sealing part side and the end of the drawn lead outer tube. This is a summary.

Further, in the present invention, a heat pipe serving as an inner pipe is passed through a lead-covered machine that combines a nipple and a die, and semi-molten lead or lead alloy is coated and solidified on the outer periphery of the heat pipe so that both ends protrude from the heat pipe. After that, a substantially hemispherical block is inserted into the lead outer tube formed at least at the end opposite to the sealing part of the heat pipe that will become the inner tube, and then both ends of the lead outer tube are drawn. The second gist is a method for manufacturing a leaded heat pipe, which is characterized in that the small hole in the center of the drawing process is sealed.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

2 to 7 show an embodiment of the present invention. As shown in Figure 2, copper, copper alloy,
Prepare a metal tube with both ends open, such as aluminum, aluminum alloy, carbon copper, or alloy copper. This metal tube is used as the inner tube 1, and a circular cap 6a is brazed to one open end, and a cap 6b having an injection capillary 7 is brazed to the other open end.

Next, this enclosed thin tube 7 is connected to a vacuum pump (not shown) to deaerate the inside of the inner tube 1, and then water and
A working fluid 8 such as fluorocarbon is sealed, and then the injection tube 7 is sealed off to form the heat pipe 2.

The heat pipe 2 obtained in this way is
After solidifying semi-molten lead or lead alloy 3a on the outer periphery of the heat pipe 2 by passing it through a lead-covering machine 11 that combines a nipple 9 and a die 10 formed to a predetermined inner diameter as shown in the figure. , water-cooled dice 10
Adjust the wall thickness of the lead outer tube 3 to a predetermined thickness by passing it through. Furthermore, this tip side is cooled with water by the shower 12 to complete the lead coating while cooling the heat pipe 2, and as shown in FIG.
It is formed so that it protrudes from both ends. Furthermore, during this leaded processing, the heat pipe 2 comes into contact with the high-temperature lead or lead alloy 3a and is heated, but since the tip side is water-cooled by the shower 12, the entire body is cooled by the rapid heat transfer action of the heat pipe 2. This can prevent damage to the heat pipe 2 and separation of the brazed portions of the caps 6a and 6b.

After the outer lead tube 3 is formed in such a manner that both ends protrude from the heat pipe 2, a substantially hemispherical block 13 is inserted into the outer lead tube 3 formed on the side opposite to the sealing section 5. As shown in FIG. 5, this block 13 is composed of a cylindrical portion 13a and a convexly curved surface portion 13b integrally formed at the tip thereof.
The material of the block 13 may be lead, copper, aluminum, iron, or an alloy thereof, but lead or a lead alloy is preferable in consideration of the weldability of the small hole after drawing.

Further, in the block 13, the ratio of the length l ₁ of the cylindrical portion 13a to the length l ₂ of the convex curved surface portion 13b is the same as that of the convex curved surface portion 1.
If the shape of 3b is almost hemispherical, l ₁ ≒ l ₂ ,
In addition, by forming the weight W ₁ of the cylindrical portion 13a and the weight W ₂ of the convex curved surface portion 13b so that W ₁ >W ₂ , it is possible to prevent the block 13 from falling due to vibration during the drawing process. . Note that the protruding curved surface portion 1
When 3b is semi-elliptic spherical, l ₁ < l ₂ may also be satisfied. In addition, it is easier to insert the block 13 if its outer diameter d is about 0.3 to 0.8 mm smaller than the inner diameter D of the end of the lead outer tube 3, but if it is too small, it will rotate internally during the drawing process.
This is not desirable as there is a risk of falling. Note that the block 13 may be formed by any processing method such as casting, cutting, forging, etc.

Next, a substantially hemispherical block 13 is attached to one end of the lead outer tube 3.
The heat pipe 2 with the heat pipe 2 inserted therein is fixed by attaching it to a support stand (not shown), and as shown in FIG. Perform drawing processing.

This concave circular die 14 has a tapered part 14a formed so that it can smoothly enter the die even if the end of the lead outer tube 3 is bent or deformed to some extent, and a tapered part 14a that is formed so that the end of the lead outer tube 3 can be smoothly inserted into the die. It is composed of a parallel part 14b provided to prevent blistering, and a concave curved part 14c that has a protruding end and is finished in a hemispherical shape.In addition, an air vent is provided at the base end to speed up air venting during the drawing process. A hole 14d is provided.

After drawing both ends of the lead outer tube 3 with the concave circular die 14 in this manner, the small hole 15 formed at the center of the drawn portion is sealed to form a leaded heat pipe as shown in FIG. Manufacture. The small hole 15 may be sealed by, for example, a gas welding method using lead or a lead alloy as a brazing material, a welding method using an electric soldering iron, an ultrasonic welding method, a pressure welding method,
Any method that provides good airtightness and sealing, such as a lead plug press-in method, may be used.

Therefore, the leaded heat pipe obtained in this way has a substantially hemispherical block 13 between the end opposite to the sealing part 5 and the end of the drawn lead outer tube 3. Since it is inserted and attached, the strength is increased and it is possible to prevent deformation and damage due to external pressure. In addition, since the block 13 is inserted and there is no air layer 4 as in the conventional case, there is no expansion and contraction of air, and fatigue cracking caused by this can be prevented, resulting in corrosion of the heat pipe 2 due to corrosive gas. It is possible to prevent this and extend the life of the leaded heat pipe.

Further, in the portion of the lead outer tube 3 into which the substantially hemispherical block 13 is inserted, since the block 13 acts as a pad, a good aperture surface without defects can be obtained.

Further, according to the above manufacturing method, since the concave circular die 14 having a concave curved surface formed in advance is pressed to perform the drawing process so as to obtain the finished shape, the process can be performed in a short time. Furthermore, in this drawing process, the heat pipe 2 provided with the lead outer tube 3 is fixed and the concave circular die 14 is rotated, so that damage to the lead outer tube 3 can be prevented and a long leaded heat pipe can be obtained. becomes possible.

FIG. 8 shows another embodiment of the present invention, in which this leaded heat pipe has both ends of a heat pipe 2 serving as an inner pipe 1 and a leaded outer pipe 3 provided on the outer periphery thereof drawn. Approximately hemispherical blocks 13A and 13B are inserted between the two ends. In this case, the sealed portion 5 side of the heat pipe 2 has a hollow portion 1 into which the sealed injection thin tube 7 is inserted.
6 is inserted into the substantially hemispherical block 13B,
Further, on the side opposite to the sealing section 5, a substantially hemispherical block 13A similar to that shown in FIG. 5 is inserted.

The leaded heat pipe with the above structure has substantially hemispherical blocks 13A and 13B inserted on both ends, so it has great strength on both sides.Furthermore, since there is no air layer with high heat transfer resistance, it has good heat transfer characteristics. It is also excellent.

In the above embodiment, the heat pipe 2 is fixed, the concave circular die 14 is rotated, and the lead outer tube 3 is
Although the drawing process is described above, a method may also be used in which the heat pipe 2 is rotated and the concave circular die 14 is pressed without rotating. Further, the drawing process is not limited to the method using the concave circular die 14,
A method using a spatula drawing process may also be used.

Next, specific examples of the present invention will be described.

Example A heat pipe 2 was prepared by using a copper tube with an outer diameter of 34 mmφ, a wall thickness of 1.5 mm, and a length of 3300 mm as the inner tube 1, attaching caps 6a and 6b to both ends thereof, and sealing water as the working fluid 8. This heat pipe 2 is connected to the leaded machine 11.
2.5mm thick lead alloy (Pb-
The heat pipe 2 is coated with lead (2% by weight Sh), and is formed so that both ends of the lead outer tube 3 protrude from both ends of the heat pipe 2, as shown in FIG.

Next, the outer diameter is 30.5 mmφ, and the length of the cylindrical part 13a is l ₁ = 16
A substantially hemispherical block 13 with a length l ₂ =16 mm of the convex curved surface portion 13b is inserted into the lead outer tube 3 on the side opposite to the sealing portion 5 side, and then attached to a support stand. Next, while rotating the concave circular die 14, the lead outer tube 3 is
After drawing by pressing the two ends of the
The mixture was welded and sealed by oxygen welding, and a leaded heat pipe as shown in FIG. 7 was manufactured.

10 leaded heat pipes obtained in this way
A heat exchanger was assembled by arranging a total of 100 pieces in 10 rows and attaching them to the partition tube plate with the block insertion side facing downward. The endothermic side of this heat exchanger is placed in a duct through which combustion waste gas (SO ₂ 300PPm, moisture 10% sulfuric acid dew point 127°C) flows, and the heat radiating side is placed in a duct through which outside air (25°C) flows. Heat exchange was performed.

As a result, the exhaust gas temperature was 191℃ on the inlet side and 65℃ on the outlet side, the amount of recovered heat was 3.1×10 ₄ kcal/h, the surface temperature of the leaded heat pipe was 50 to 150℃, and there was no corrosion even after one year of operation. It was not recognized.

Comparative Example In the above example, approximately hemispherical block 13
A lead-covered heat pipe as shown in FIG. 1 was manufactured in the same manner except that the heat pipe was not inserted. A heat exchanger was similarly assembled using 100 of these leaded heat pipes, and heat exchange was performed under the same conditions as in the above example. After 3 months, approximately 1/3 of the leaded heat pipes had absorbed heat. Corrosion occurred from the side end, creating a through hole and stopping operation.

As explained above, according to the lead-covered heat pipe and the manufacturing method thereof according to the present invention, it is possible to easily process the end of a lead-covered pipe, increase the strength of the end, and prevent fatigue deterioration due to expansion and contraction. It has remarkable effects such as being able to prevent corrosion and extend life.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a conventional leaded heat pipe, Fig. 2 to Fig. 7 show an embodiment of the present invention, Fig. 2 is a cross-sectional view of the heat pipe, and Fig. 3 is a cross-sectional view of the heat pipe. Figure 4 is a cross-sectional view of the heat pipe after it has been leaded, Figure 5 is a front view of the block, and Figure 6 is the state in which the end is processed. 7 is a sectional view showing a leaded heat pipe, and FIG. 8 is a sectional view of a leaded heat pipe according to another embodiment of the present invention. 1...Inner tube, 2...Heat pipe, 3...Outer tube, 4...Air layer, 5...Sealing section, 11...
Lead-covered machine, 13, 13A, 13B...Block, 1
4...Concave circular die, 15...Small hole.

Claims (1)

[Scope of Claims] 1. A leaded heat pipe in which an outer tube made of lead or a lead alloy is tightly lead-coated around the outer periphery of the heat pipe, and both ends of the lead outer tube are sealed by drawing. A leaded heat pipe characterized in that a substantially hemispherical block is inserted between at least the end of the heat pipe opposite to the sealing part side and the end of the drawn lead outer tube. heat pipe. 2. The leaded heat pipe according to claim 1, wherein the substantially hemispherical block is composed of a cylindrical portion and a single convex curved surface portion formed at the distal end of the cylindrical portion. 3 Pass a heat pipe which becomes an inner tube through a lead-covered machine that combines a nipple and a die, cover the outer periphery with semi-molten lead or lead alloy so that both ends protrude from the heat pipe, and then cover the inner tube with lead or lead alloy. A substantially hemispherical block is inserted into the lead outer tube formed at least on the end side opposite to the sealing part side of the heat pipe that becomes the tube, and then both ends of the lead outer tube are drawn, and then, A method for manufacturing a leaded heat pipe characterized by sealing a small hole in the center of the drawn heat pipe. 4. The method for manufacturing a leaded heat pipe according to claim 3, characterized in that the drawing process of both ends of the lead outer tube is performed using a concave circular die.