JPS6132598B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a leaded heat pipe that has excellent sulfuric acid dew point corrosion resistance and is used in a heat exchanger that recovers heat from waste gas containing sulfur oxides. In general, a heat exchanger for waste heat recovery using a heat pipe places the heat absorption side of the heat pipe in a duct through which high-temperature waste gas flows, and the heat radiation side of the heat pipe in a duct through which clean air flows or water flows through. They are placed inside pipes that carry water and recover waste heat to heat air and water. However, when fuel oil containing sulfur is used, the combustion gas contains sulfur oxides (SOx), and when this waste gas comes into contact with the heat pipe and its temperature drops below the sulfuric acid dew point, sulfuric acid forms on the surface. is generated, which causes corrosion. For this reason, leaded heat pipes are used in which the outer tube is coated with lead or a lead alloy that has excellent sulfuric acid dew point corrosion resistance. Conventionally, this leaded heat pipe manufacturing method was the first method.
It is manufactured by the method shown in FIGS. 5 to 5.
First, as shown in Figure 1, prepare a copper pipe with both ends open, which will become the inner pipe 1, and pass it through a lead-bearing machine that combines a pouring ring (nipple) and a die to pour semi-molten lead. Or cover the lead alloy and solidify the outer tube 2.
Then, a leaded double pipe 3 as shown in FIG. 2 is manufactured. Next, as shown in FIG. 3, after removing both ends of the outer tube 3 to expose the inner tube 1, a circular cap 4 is attached to one end of the inner tube 1 and the other end is removed as shown in FIG. A cap 6 with an injection capillary 5 is respectively brazed to the cap. Next, the injection capillary 5 is connected to a vacuum pump to degas the inside, and then a predetermined amount of the working fluid 7 is poured from there.
was injected, and then the injection tube 5 was sealed off to produce a leaded heat pipe 8 as shown in FIG. However, in the above method, the lead outer tubes 2 at both ends melt when the caps 4 and 6 are brazed, so these portions must be removed. This removal work of the leaded outer tube 2 is extremely troublesome, and the resultant leaded heat pipe 8 has the inner tube 1 at both ends exposed, so it has the disadvantage that this part is corroded. Ta. The present invention has been made as a result of conducting various studies in view of such conventional drawbacks, and has discovered a method for manufacturing a leaded heat pipe that enables complete lead coating at the end and improves sulfuric acid dew point corrosion resistance. . That is, the method of the present invention involves passing semi-molten lead or lead alloy around the outer periphery of the heat pipe, which serves as an inner pipe, through a lead-covered machine that combines a pouring ring (nipple) and a die, with both ends protruding from the heat pipe. After the coating is solidified in such a manner, both protruding ends of the formed lead outer tube are drawn and hermetically sealed. Hereinafter, the method of the present invention will be explained in detail with reference to the drawings. 6 to 12 show one method of the present invention. First, as shown in FIG. 6, a metal tube with open ends, such as copper, copper alloy, carbon steel, or alloy steel, is used as the inner tube 1. As shown in FIG. 7, a circular cap 4 is brazed to one open end, and a cap 6 having an injection capillary 5 is brazed to the other open end. Next, this injection tube 5 is connected to a vacuum pump (not shown) to degas the inside of the inner tube 1, and then water and
A working fluid 7 such as fluorocarbon is sealed, and then the injection tube 5 is sealed off to form a heat pipe 9 as shown in FIG. The heat pipe 9 obtained in this way is
The outer periphery of the heat pipe 9 is coated with semi-molten lead or lead alloy 13 by passing it through a lead coating machine 12 that combines a pouring ring (nipple) 10 and a die 11 formed to a predetermined inner diameter, as shown in the figure. After solidification, the lead outer tube 2 is passed through a water-cooled die 11 to adjust the thickness to a predetermined thickness, and the tip side is further water-cooled by a shower 14 to complete lead coating while cooling the heat pipe 9. As shown in FIG. 10, the lead outer tube 2 is formed to protrude from both ends of the heat pipe 9. In this case, the material for the outer tube 2 may be lead, but
Lead alloy 1 consisting of 0.5 to 11% by weight of one or both of tin (Sn) and antimony (Sb) in terms of workability and mechanical strength, and the balance being lead.
3 is preferred. In the present invention, the reason why the composition of the lead alloy 13 is limited to the above range is as follows. Tin and antimony have the effect of increasing the mechanical strength of lead alloy 13 and making it easier to work with.These elements may be added alone or both may be added at the same time. good. If the total amount added is less than 0.5% by weight, mechanical strength will be poor, and if it exceeds 11% by weight, the structure will become brittle and workability will decrease, which is not preferable. Note that if arsenic (As) is added in an amount of 0.3% by weight or less, the mechanical properties can be further improved without impairing processability. In addition, in order to improve the adhesion between the heat pipe 9 and the lead outer tube 2, the interference φ during lead processing, that is, the difference between the outer diameter d ₁ of the heat pipe 9 and the inner diameter d ₂ of the lead outer tube 2 in the empty state is determined. It is preferable to adjust the pouring ring (nipple) 10 of the leaded machine 12 and the die 11 so that the difference φ=d ₁ -d ₂ is in the range of 0.2 to 2.0 mm. If the interference φ is less than 0.2 mm, the adhesion between the heat pipe 9 and the lead outer tube 2 will deteriorate and the thermal resistance will increase, and if it exceeds 2.0 mm, internal stress will increase and the drawing process performed in the subsequent process will be difficult. Since cracks may sometimes occur, it is desirable that the interference φ be within the above range. Furthermore, during lead processing, the heat pipe 9 comes into contact with high-temperature lead or lead alloy 13 and is heated, but since the tip side is water-cooled by the shower 14, the entire body is cooled by the rapid heat transfer action of the heat pipe 9.
It is possible to prevent the heat pipe 9 from bursting and from increasing the thermal resistance at the interface of the contact portion. Note that the cooling temperature in this case is preferably 100°C or less. As mentioned above, the lead outer tube 2 is attached to the outer periphery of the heat pipe 9.
After coating the heat pipe with lead, as shown in FIG. 11, it is mounted on a turntable and rotated, while pressing the spatula 15 against the portion of the lead outer tube 2 that protrudes from both ends of the heat pipe 9, and the circular cap 4 side is A drawing process is performed so that it comes into close contact with this, and a drawing process is performed so that an air layer 16 is formed on the side of the cap 6 having the injection tube 5. Next, the small holes 17 formed at both ends of the lead outer tube 2 by this drawing process are sealed by melting with a burner or by brazing to complete the leaded heat pipe 8 as shown in FIG. . The lead-covered heat pipe 8 thus obtained is entirely covered with the lead outer tube 2, and both ends of the heat pipe 9 are not exposed, so there is no corrosion from this part and a long service life can be achieved. In addition, since the air layer 16 is formed in the sealed injection capillary tube 5, this portion can be protected from external impact. Note that the present invention provides a lead outer tube 2 as shown in FIG.
After drawing to form air layers 16, 16 at both ends of the leaded heat shield, the fins 18 are formed integrally with the outer tube 2 by rolling through a roller die with threaded grooves. It may also be pipe 8. Next, specific examples of the present invention will be described. Example A copper tube with an outer diameter of 32 mmφ, a wall thickness of 1.5 mm, and a length of 2 m is used as the inner tube 1. A circular copper cap 4 is brazed to one open end of the inner tube 1, and an injection thin tube 5 is provided at the other open end. After brazing the copper cap 6, the inside is degassed and water is filled in as the working fluid 7.
Thereafter, the injection tube 5 was sealed off, and a heat pipe 9 as shown in FIG. 8 was assembled. Next, this heat pipe 9 is passed through a lead-covered machine 12 as shown in FIG. Tube 2 was formed. Next, both ends of the lead outer tube 2 are drawn using an inner hemispherical die, and the formed small holes 17, 17 are heated with an oxygen-hydrogen burner to melt and seal, forming a lead-covered heat pipe as shown in FIG. 8 was manufactured. The leaded heat pipe 8 obtained in this way is
A total of 100 heat pipes were arranged in 10 rows and 10 stages to assemble a heat pipe heat exchanger. The endothermic side of this heat exchanger is connected to heavy oil combustion waste gas ( _SO2 300ppm, moisture 10%, sulfuric acid dew point 127).
The heat dissipation side was placed inside a duct through which outside air (25°C) flows, and waste heat was recovered. In this case, the inlet and outlet temperatures of the waste gas, the amount of recovered heat, and the surface temperature of the leaded heat pipe 8 were determined for one year under the conditions shown in Table 2 for each heat exchanger No. 1 to No. 4 above. Waste heat was recovered. As shown in Table 2, the surface temperature of the leaded heat pipe 8 was partially lower than the sulfuric acid dew point, but no corrosion was observed on the surface. Note that the heat exchanger No. 4 assembled using the lead-covered heat pipe 8 without water cooling had a slight decrease in performance. Comparative Example For comparison with the effects of the present invention, a leaded heat pipe 8 (No. 5) as shown in FIG. 10 in which both ends of the lead outer tube 2 are not sealed, and a lead outer tube 2 as shown in FIG. 8 were formed. A heat exchanger was assembled using each of the heat pipes 9 (No. 6) that had not been used, and waste heat recovery was performed in the same manner as in the above example. As shown in Table 2, this result shows that the lead outer tube 2
No. 5, in which the ends of the heat pipe were not sealed, corroded on both ends, and after about three months, a through hole was formed in one-third of the leaded heat pipe 8, and the operation stopped.
In addition, the heat pipe No. 6 that uses the heat pipe 9 without the lead outer tube 2 takes about one-third of the total heat in about one month.
A through hole was formed in the hole and the operation stopped.

【table】

[Table] As explained above, according to the method for manufacturing a leaded heat pipe according to the present invention, after the outer periphery of the heat pipe is coated with molten lead or lead alloy and solidified, both ends of the leaded outer pipe are squeezed. Since it is processed and sealed, it is extremely easy to work with, and the ends can be completely leaded, and it has excellent sulfuric acid dew point corrosion resistance. It has remarkable effects such as being able to improve performance and extend life.

[Brief explanation of the drawing]

FIGS. 1 to 5 are cross-sectional views sequentially showing a method for manufacturing a leaded heat pipe according to the conventional method, and FIGS. 6 to 12 are sectional views showing a method for manufacturing a leaded heat pipe by the method of the present invention. FIG. 13 is a cross-sectional view of a lead-covered heat pipe in which fins are formed by rolling. 1...Inner pipe, 2...Outer pipe, 3...Leaded double pipe,
4, 6...Cap, 5...Injection tube, 7...Working fluid, 8...Leaded heat pipe, 9...Heat pipe, 10...Pouring ring (Nitsupil), 11...
...Dice, 12...Leaded machine, 14...Shower,
15... spatula, 16... air layer, 17... small hole,
18...Fin.

Claims (1)

[Scope of Claims] 1. A heat pipe serving as an inner tube is passed through a lead-covered machine that combines a pouring ring (nipple) and a die, and semi-molten lead or lead alloy is passed around the outer circumference of the heat pipe, and both ends thereof are connected to the heat pipe. A method for producing a leaded heat pipe, which comprises solidifying the coating so that it protrudes more, and then drawing and sealing both protruding ends of the formed lead outer tube. 2. The method for manufacturing a leaded heat pipe according to claim 1, wherein the lead or lead alloy is coated and solidified while cooling the heat pipe on the outlet side of the leaded machine. 3. Claim 1, characterized in that lead or a lead alloy is coated and solidified so that the interference between the outer diameter of the heat pipe serving as the inner pipe and the inner diameter of the lead outer pipe is 0.2 to 2.0 mm. A method of manufacturing the described leaded heat pipe. 4. A lead alloy according to claim 1, characterized in that the lead outer tube is made of a lead alloy consisting of a total of 0.5 to 11% by weight of either one or both of tin and antimony, and the balance being lead. Method of manufacturing leaded heat pipes.