JP3297838B2 - Heat transfer tube and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat transfer tube used for a falling liquid film type heat exchanger and the like and a method for producing the same.
More particularly, the present invention relates to a heat transfer tube suitable for an absorption refrigerator using a corrosive absorbing solution such as an aqueous solution of lithium bromide, or a refrigerant, and a method for manufacturing the same.

[0002]

2. Description of the Related Art A falling liquid film type heat exchanger is widely used in an absorber or an evaporator of an absorption air conditioner or the like. For example, in an absorber, a large number of heat transfer tubes are arranged horizontally and in multiple stages in a closed container, and the absorbing solution flows down sequentially from the uppermost heat transfer tube to the lower stage, while the refrigerant vapor generated from the evaporator is closed. To absorb the refrigerant vapor into the absorbing liquid on the surface of the heat transfer tube. Then, the heat of absorption generated by the absorption reaction is cooled by a cooling medium flowing through the heat transfer tube.

A heat transfer tube used in such a falling liquid film type heat exchanger is disclosed in, for example, Japanese Patent Application Laid-Open No. Hei 5-340646.
As described in Japanese Patent Application Publication No. JP-A-Heisei 1-134180 or Japanese Patent Application Laid-Open No. 1-134180, fins are formed at equal pitches on the surface of a heat transfer tube to increase a heat transfer area to improve heat transfer. Have been. However, in the case of such a fin-type heat transfer tube, if the pitch of the fins is reduced, the thickness of the flowing liquid film formed between the fins may be increased. When the thickness of the liquid film is increased, the heat transfer of the absorbed heat generated by the absorption phenomenon occurring only on the surface of the falling liquid film is reduced, and the cooling capacity is reduced. Therefore, it has been proposed to increase the pitch of the fins and reduce the thickness of the liquid film formed between the fins, but on the other hand, the heat transfer area of the fins is reduced. When applied, there is a problem that it is difficult to realize an increase in absorption capacity as expected.

[0004] Apart from such a problem, in the case of the fin type heat transfer tube, there is a problem that the action of the fin to spread the liquid film in the tube axis direction is hindered. Therefore, when the flowing liquid flows down the heat transfer tubes arranged in multiple stages, the spread of the liquid film in the axial direction of the heat transfer tubes becomes poor, and the further down the heat transfer tubes, the worse the uniformity of the liquid film becomes. Then, a portion where the liquid film does not exist is generated. As described above, since the absorption phenomenon does not occur in the region where the liquid film such as the absorbing solution does not exist on the heat transfer tube, the fin formed for promoting the absorption phenomenon does not work effectively as a result.

In this regard, Japanese Patent Laid-Open Publication No. Hei 5-340646 proposes a method of improving the axial spreadability of a liquid film by cutting off a part of a lower fin of a heat transfer tube in a liquid film flowing direction. . However, since a post-process such as fin cutting is required, machining is difficult, and there is a problem that it is not practical in view of a manufacturing method and cost.

On the other hand, instead of the above-mentioned fin-type heat transfer tube, a plurality of depressions are formed by plastic deformation processing on the outer surface of the tube wall of the heat transfer tube as described in JP-A-6-25712, and It has been proposed that the depth of the depression is made smaller than the diameter of the depression so as to enhance heat transfer performance and absorption performance. According to this, the falling liquid film spreads in the tube axis direction and becomes uniform.

[0007]

SUMMARY OF THE INVENTION The above-mentioned JP-A-6-257
The hollow heat transfer tube described in Japanese Patent Publication No. 12 is easy to process, and the spreading of the falling liquid film in the tube axis direction becomes uniform.
It is suitable for a falling liquid film type heat transfer tube, but has the following problems to be solved.

That is, water is used as a refrigerant inside a heat transfer tube like a water-cooled absorber, and the water is circulated from an outdoor cooling tower or the like. , And other foreign substances. On the other hand, on the inner surface of the tube wall of the heat transfer tube,
A convex portion corresponding to the depression is formed. While the cooling water is flowing, those foreign substances move along with the flow, but the cooling water stops, and the foreign substances stay and adhere to the depressions between the convex parts. This causes problems such as a decrease in heat transfer performance and an increase in the possibility of corrosion. For example, fine linear foreign matter is fixed to a specific part of the inner surface of the pipe,
If the inner surface of the tube is repeatedly hit in accordance with the flow of the refrigerant, there arises a problem that the corrosion-resistant coating covering the inner surface of the tube is locally peeled off, and intensive corrosion occurs on the surface. Also, instead of a seamless pipe (seamless pipe),
In the case of a seam pipe (seam pipe), which is formed by bending a band-like plate into a tubular shape and welding the butt portion to form a pipe, according to normal welding such as TIG welding, burrs and scales remain near the welding line. Further, the possibility of corrosion is increased.

The present invention has high heat transfer performance and corrosion resistance,
It is an object to provide a heat transfer tube that can be easily processed and a method for manufacturing the same.

[0010]

SUMMARY OF THE INVENTION The present invention is to solve the above problems by the following means. fundamentally,
A heat transfer tube having a plurality of recesses formed by plastic deformation processing on the outer surface of the tube wall. As a result, Japanese Patent Laid-Open No. 6-2
As described in Japanese Patent No. 5712, heat transfer performance can be enhanced and processing is easy. Then, a smooth portion where the concave portion is not formed is formed on a part of the peripheral surface of the tube wall,
It is assumed that this smooth portion is provided to extend in the axial direction of the pipe. According to this, when the heat transfer tube is horizontally disposed, the smooth portion without the concave portion is disposed on the lower side, so that when the flow of the internal fluid is stopped, foreign matter is deposited on the smooth portion. Even so, foreign matter is discharged by flowing the internal fluid. As a result, adhesion of foreign substances can be suppressed or prevented, and corrosion resistance can be improved.

Here, even if a smooth portion is provided on a part of the tube surface,
Explain that the heat transfer performance and the absorption performance are not reduced as compared with the case where the concave portion is provided on the entire surface. Looking at the cross section of the falling film heat transfer tube, as shown in FIG. 3 (A), the liquid 10 flowing down from above flows down from the upper outer surface of the heat transfer tube 1 along the outer surfaces on both sides to the lower portion. It reaches the outer surface, from which it flows down to the top of the next lower heat transfer tube. At this time, heat transfer tube 1
As shown in the figure, the liquid film flow 11 having a funnel-shaped cross section is formed according to the liquid properties such as gravity, surface tension and viscosity of the liquid as shown in FIG.
The portion where the liquid film flow 11 having such a thickness is formed,
As described above, heat transfer of the liquid film is hindered. Therefore, even if there is a concave portion that increases the heat transfer area and the like, the contribution to the improvement of the heat transfer performance is small. Further, even if a concave portion is formed in this portion, the surface area of the liquid film does not increase, so that the absorption performance cannot be improved. In view of such findings, the present invention organically combines the heat transfer and absorption action of the liquid falling film below the heat transfer tube with the action of preventing foreign matter from adhering to the cooling water, and forms a smooth portion on a part of the pipe surface. This has solved the problem of the present invention.

By the way, forming a plurality of recesses in the pipe wall while forming a smooth portion extending in the pipe axis direction is practical in the case of a seamless pipe formed by a rolling method or the like in consideration of costs and the like. Have difficulty. That is, in the rolling method, the tube is rotated around the axis while pressing a roll having a projection corresponding to the concave portion on the outer surface of the tube, and the concave portion is formed on the outer surface of the tube wall while being fed in the axial direction. In the case of such a rolling method, since the circumference of the heat transfer tube changes with the processing, the relative positional relationship corresponding to the roll and the smooth portion of the heat transfer tube moves with the rotation, and the roll moves in a straight line in the tube axis direction. It is difficult to form a flat smooth portion.

On the other hand, if a heat transfer tube having a concave portion formed on the entire outer surface of the tube wall is to be formed by a seam tube, a clean and smooth welding line can be obtained because the butt weld does not become linear due to the concave portion. Not practical.

In this respect, since the heat transfer tube of the present invention has a smooth portion formed in the tube axis direction, the seam tube can be easily and smoothly formed by welding such as electric resistance welding using the smooth portion. Since it can be manufactured, it is preferable to form it with a seam tube. In this case, welding by high frequency welding is preferable because the welding line can be made smoother without burrs and the like, and the crystal grain size of the welded portion can be reduced, so that the corrosion resistance can be improved.

In the above case, the width of the smooth portion in the circumferential direction is preferably not less than 2 mm and not more than 120 ° in terms of the circumferential angle. 2 mm or more is preferable.
As shown in FIG. 3 (B), if there is unevenness in the region where foreign matter settles when the internal fluid is stopped, the foreign matter settled in the concave is difficult to be discharged even when the flow of the internal fluid is resumed.
This is because when seam welding is performed, a flat butted portion without unevenness processing is required. The reason why the thickness is preferably 120 ° or less is that the thickness of the liquid film flow 11 is determined by the viscosity and surface tension of the flowing liquid as described with reference to FIG.
This is because, when the smooth portion is provided beyond 120 °, the rate of decrease in the heat transfer effect due to the absence of unevenness increases.

The recess formed in the tube wall can be a depression or a groove. In particular, it is preferable that the depressions or grooves are continuously arranged with a certain regularity in the tube axis direction and the circumferential direction. The size of the depression can be made different in size. Furthermore, in the case of a large-diameter pipe, increasing the size and depth of the dent or groove on the outer surface of the pipe and forming a small dent or projection on the concave surface part improves the absorption efficiency and allows the inner fluid to communicate with the internal fluid. It is preferable in that the heat exchange efficiency is improved.

Further, when the maximum surface roughness of the outer surface of the tube wall excluding the smooth portion is set to 0.08 μm to 100 μm and the maximum surface roughness of the inner surface of the tube wall is set to 0.04 μm to 10 μm, the wettability is increased and the heat transfer is improved. This is preferable because the performance can be improved. The upper limit of the maximum surface roughness is based on the fact that foreign matter and residue are not easily attached and cleaning is easy. The lower limit is set in consideration of manufacturability (for example, lubricity, workability, feedability, etc.). preferable.

It is preferable that the crystal grain size of the seam welded portion be within three times the crystal grain size of the base metal in order to enhance corrosion resistance. Further, it is preferable to perform an annealing treatment at a temperature equal to or higher than the recrystallization temperature of the base material at least after welding, in order to further increase the corrosion resistance.

As the material of the heat transfer tube, it is preferable to use copper or an alloy containing copper as a main component in terms of workability, weldability, corrosion resistance and the like.

The heat transfer tube according to the present invention comprises a step of forming a plurality of recesses in a region excluding both side edges of the band-shaped metal plate by plastic deformation processing, and bending the band-shaped metal plate into a tubular shape and abutting both side edges, It is preferable to manufacture the heat transfer tube by a method for manufacturing a heat transfer tube including a step of performing high-frequency welding while applying a pressing force to the butted portion.

In this case, it is desirable to add a step of cutting and removing the molten metal portion extruded to the inner side and the outer side of the tube wall of the butt portion by high frequency welding with a cutting tool. It is preferable to add a step of annealing the heat transfer tube at a temperature equal to or higher than the recrystallization temperature of the base material after the high frequency welding. Further, in order to form a concave portion having improved wettability, press working is performed by a mold that combines a convex shape having a maximum surface roughness of 0.08 μm to 100 μm and a concave shape having a maximum surface roughness of 0.04 μm to 10 μm. By
realizable.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a conceptual configuration in a case where the heat transfer tube according to the present invention is used as a heat transfer tube of an absorber of an absorption type cooling and heating device, and FIG. 2 shows a cross section of the heat transfer tube. As shown in FIG. 1, the heat transfer tube 1 is used by being disposed horizontally and in multiple stages at intervals in a vessel into which the vapor of the medium to be absorbed is introduced. The absorption liquid flowing down the surface of the heat transfer tube 1 is allowed to absorb the vapor of the medium to be absorbed, and the heat generated by the absorption reaction is exchanged with the coolant 15 flowing inside the heat transfer tube. Then, as shown in FIGS.
A plurality of depressions 2 are formed by plastic deformation processing on the outer surface of the heat transfer tube at a portion where the flow-down of the pipes 0 flows, and a smooth portion 3 in which the recess 2 is not formed is formed on the lower surface of the tube wall. In the axial direction. As the absorbing liquid 10, for example, an aqueous solution of lithium bromide is used.
Are continuously arranged with a certain regularity in the tube axis direction and the circumferential direction. When the depression 2 is formed by plastic deformation processing, the cross-sectional shape of the inner surface of the tube corresponding to the depression 2 is a convex portion 4 of a spherical surface, a circular shape, or a smooth closed surface.
Are formed. Various shapes such as a truncated cone, a pyramid, and the like can be adopted as the shape of the depression 2. Further, the present invention is not limited to a point-like depression, and may be a groove-like depression extending in the tube axis direction or the spiral direction. The material of the heat transfer tube 1 is workability, weldability,
Copper or an alloy containing copper as a main component is preferable in terms of corrosion resistance and the like.

According to the absorber using the heat transfer tube shown in FIG. 1, since a plurality of depressions 2 are formed on the outer surface of the heat transfer tube 1, as shown in Japanese Patent Laid-Open No. The liquid film of the liquid can be made thin and uniform, and the spread in the axial direction can be improved. As a result, the width of the falling liquid film in the tube axis direction becomes narrower as it flows down to the lower heat transfer tube 1, and a dry portion is formed on the outer surface of the heat transfer tube 1, and the absorption capacity and the heat exchange capacity are reduced. Is solved, the heat transfer performance and the absorption performance can be improved, and the processing is easy. In particular, since the smooth portion 3 in which the depression 2 does not exist is formed at the lower part in the downflow direction of the absorbing liquid 10, the effect that the liquid film spreads in the tube axis direction when the liquid film leaves the heat transfer tube 1 is high.

In particular, when the heat transfer tube 1 is disposed horizontally, the smooth portion 3 having no concave portion is disposed on the lower side, so that the flow of the coolant 15 as the internal fluid is stopped. Even if foreign matter is deposited on the smooth portion 3 when the
The foreign matter is discharged along the flow by flowing the gas. As a result, adhesion of foreign substances can be suppressed or prevented, and corrosion resistance can be improved. Further, as described above with reference to FIG. 3 (A), even when the smooth portion 3 is provided on a part of the tube surface, the heat transfer performance and the absorption performance are lower than those provided with the depression 2 on the entire surface. is not.

However, the width of the smooth portion 3 in the circumferential direction is as shown in FIG.
As shown in (B), if unevenness is present in a region where foreign matter settles when the internal fluid is stopped, the foreign matter settled in the concave portion resumes the flow of the internal fluid (for example, a flow rate of about 2 m / s). It is difficult to discharge, or when welding by seam, a flat butted part without unevenness is required.
m or more. Also, if the upper limit of the circumferential width of the smooth portion 3 is too large, the heat transfer effect and the reduction rate of the absorption performance due to the absence of unevenness for improving the wettability increase, so that the circumferential angle is 120 °. It is preferable to be within the following range. Further, when processing the depression 2 in the heat transfer tube 1, the processing cost is increased and the weight per unit length is increased, so that the cost of the heat transfer tube is increased.
Therefore, it is advantageous not to provide a depression or the like in a portion where the rate of the heat transfer promotion or the absorption promotion effect is small, when performance improvement and cost reduction are comprehensively considered.

The recess formed in the tube wall may be a recess or a groove. In particular, it is preferable that the depressions or grooves are continuously arranged with a certain regularity in the tube axis direction and the circumferential direction. The size of the depression can be made different in size. Furthermore, in the case of a large-diameter pipe, increasing the size and depth of the dent or groove on the outer surface of the pipe and forming a small dent or projection on the concave surface part improves the absorption efficiency and allows the inner fluid to communicate with the internal fluid. It is preferable in that the heat exchange efficiency is improved.

Next, a preferred method of manufacturing the heat transfer tube according to the present invention will be described with reference to FIG. As described above, it is practically difficult to form the plurality of depressions 2 in the tube wall while forming the smooth portion 3 extending in the tube axis direction by a rolling method or the like, in consideration of costs and the like. . Therefore, it is preferable to form by the seam pipe method by the electric resistance welding by the process shown in FIG.

First, at the stage of a strip-shaped plate or strip, a desired depression or groove is formed by plastic deformation such as pressing or rolling. Then, the plate material 21 subjected to the processing such as the depression is directed to the tube forming section 22 shown in FIG. The two sides of the strip are abutted through a pair to form a tube. Next, a high-frequency current is supplied to the high-frequency coil 24 by guiding the electric current to the electric resistance welded portion 23, and the butted portion is subjected to high-frequency welding. At this time, welding is performed while applying pressure in the butting direction to the butting portions on both side edges of the strip, and the molten portion is extruded to the inside or outside of the pipe or to one surface, thereby removing dirt and deposits on the strip end to the welding section. And the metal structure near the weld is adjusted. Thereafter, the bead extruded and solidified on the outer surface or inner surface of the tube is removed with a cutting tool or the like, and then, if necessary, the tube is formed by drawing at the drawn portion 26. Furthermore, if necessary, in order to prevent corrosion near the weld line 25, after welding, an annealing treatment is performed at a temperature equal to or higher than the recrystallization temperature of the base material. At this time, the effect is high if the crystal grain size of the welded portion is within three times the base material crystal grain size. The measurement of the crystal grain size is based on JIS H0501.
The comparison method, the cutting method and the quadrature method defined in (established in 1957) can be applied, but the cutting method is preferred.

As described above, by performing welding while extruding the molten structure of the butt weld portion, as shown in FIG. 5, the nonuniformity of the crystal structure of the metal at the weld portion (arrow 31) can be reduced. FIG. 5 is a cross-sectional photograph of a welded portion of the heat transfer tube formed by high-frequency welding , and FIG. 6 is a cross-sectional photograph of a welded portion of the heat transfer tube formed by TIG welding for comparison. According to the high frequency welding shown in FIG. 5, the welding line is not clear. This is because the molten portion is extruded and processed outside the pipe, and the weld line is not a solidified structure but a structure close to the base metal structure, indicating that the crystal structure has not changed near the weld line. I have.

On the other hand, in the example of TIG welding shown in FIG. 6, since the solidified structure after melting remains as it is, and due to the effect of welding, the weld line (arrow 32)
In the vicinity, it can be seen that there is a structure having a crystal size different from that of the base material. Further, there is a high possibility that inclusions such as oxides and voids are involved in the welding.

FIGS. 7 and 8 are cross-sectional photographs obtained by immersing the heat transfer tubes corresponding to FIGS. 5 and 6 in a 55% aqueous solution of lithium bromide for 3 weeks and then breaking the weld. FIG.
Is for high frequency welding, but no change appears in the welded portion. On the other hand, in the case of the TIG welding shown in FIG. 8, it was recognized that corrosion started in the welded portion on the right side of the photograph. 9 and 10 show the results of immersing the heat transfer tubes corresponding to FIGS. 5 and 6 in 10% hydrochloric acid for 3 days. Similar to the case of the lithium bromide aqueous solution, it is recognized that the corrosion of the TIG welding (FIG. 10) has started when compared with the high frequency welding (FIG. 9). Therefore, when the heat transfer tube is used in an environment where a corrosive refrigerant or absorption solution is used, the corrosion resistance can be improved by using high-frequency welding instead of TIG welding.

Here, when examining the extrusion amount at the time of butt welding, it is preferable to set the amount of reduction in the circumferential length of the pipe after welding with respect to the circumferential length of the pipe before welding to be within a range of 2 to 10 mm. . That is, the amount of decrease in the perimeter is 2 mm
If less than the influence of the molten structure is likely to remain in the weld,
Also, coarsening of crystal grains is likely to occur. On the other hand, 10m
If it exceeds m, the dimensional accuracy of the heat transfer tube is affected, and the residual strain in the vicinity of the welded portion increases, which adversely affects corrosion resistance and the like.

Further, in order to enhance the anticorrosion performance, the grain size of the welded portion should be within three times the crystal grain size of the base material, or after the welding, annealing treatment should be performed at a temperature higher than the recrystallization temperature of the base material. Is desirable.

As described above, the manufacturing method shown in FIG. 4 is technically and economically advantageous as compared with forming a hollow or the like by rolling after forming a seamless pipe. . In particular, by appropriately designing the press die or the upper and lower rolls, it is possible to provide a depression structure corresponding to the upper surface and the lower surface of the plate material.

In addition, by bringing the welding line 4 to a smooth portion having no depression, it is possible to eliminate uneven flow of the liquid film caused by the welding line. Moreover, by forming the welding wire 4 by high-frequency welding, it is possible to reduce burrs and the like that are likely to cause uneven flow of the liquid film. At this time,
By abutting the short portions at both ends of the strip at the time of welding, and extruding the welded portion to the inside or outside of the tube or one surface while applying pressure, the crystal structure of the metal at the welded portion can be optimized and the corrosion resistance can be increased.

Next, modified examples of the depression 2 of the heat transfer tube according to the present invention are shown in FIGS. In order to improve the wettability of the inner and outer surfaces of the heat transfer tube 1, as shown in FIGS. 11 to 14, the maximum surface roughness of the outer surface and the depression 2 is preferably set to 0.08 μm to 100 μm. Further, the maximum surface roughness of the inner surface is preferably set to 0.04 μm to 10 μm. Such a roughness has a maximum surface roughness of 0.08μ.
m to 100 μm convex shape and maximum surface roughness of 0.04 μm
It can be formed by press molding with a mold combining concave molds of m to 10 μm. In order to facilitate such processing, the material of the heat transfer tube 1 is desirably copper or an alloy containing copper as a main component.

When the diameter of the heat transfer tube is large,
Unless the protrusion on the inner surface is enlarged, the effect of improving the internal heat transfer performance cannot be obtained. That is, regarding the outer surface of the heat transfer tube 1, the thickness of the liquid film flowing down is several tenths of a millimeter, and the depth of the depression is about 1 to 2 mm. The length does not depend on the diameter of the tube. However, looking at the inside of the heat transfer tube 1, the cooling water flows over the entire area of the cross section, and the optimum height of the convex portion for improving the heat transfer performance varies depending on the diameter of the tube. For example, the height of the convex portion is said to be high in the effect of improving the heat transfer performance when the height is 1 to several tenths of the tube diameter. Need to be bigger.

Therefore, as shown in FIGS. 15 to 18, a large depression 35 is formed on the surface of the heat transfer tube 1 and small depressions 36 and 37 are formed therein, or a small projection 3 is formed.
8, 39 are preferably formed. Alternatively, as shown in FIG. 19, it is also effective to form a large dent 40 and a small dent 16 adjacent to each other.

In the above description, an example in which the heat transfer tube according to the present invention is applied to an absorber has been described. However, the heat transfer tube of the present invention is not limited to this, and may be applied to a heat transfer tube of a falling liquid film heat exchanger. The same effect can be obtained by applying.

[0040]

As described above, according to the present invention,
A heat transfer tube suitable for a falling liquid film system, having high heat transfer performance and absorption performance, high corrosion resistance, and easy processing can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram showing a conceptual configuration when an example of a heat transfer tube according to the present invention is applied to an absorber.

FIG. 2 is a sectional view of the heat transfer tube shown in FIG.

FIG. 3 is a cross-sectional view for explaining the operation and the like of the heat transfer tube according to the present invention.

FIG. 4 is a diagram showing an example of a heat transfer tube manufacturing apparatus according to the present invention.

FIG. 5 is a photograph showing a metal structure of a welded portion welded by high-frequency welding.

FIG. 6 is a photograph showing a metal structure of a welded portion welded by TIG welding.

FIG. 7 shows a heat transfer tube 5 formed by welding by high frequency welding.
It is a photograph showing the metallographic structure of the weld after immersion treatment for 3 weeks in 5% lithium bromide aqueous solution.

FIG. 8 shows a heat transfer tube 5 formed by welding by TIG welding.
It is a photograph showing the metallographic structure of the weld after immersion treatment for 3 weeks in 5% lithium bromide aqueous solution.

FIG. 9 shows a heat transfer tube 1 formed by welding by high frequency welding.
It is a photograph showing the metallographic structure of a welding part after immersion treatment for 3 weeks in 0% hydrochloric acid.

FIG. 10 is a photograph showing a metallographic structure of a weld after a heat transfer tube formed by welding by TIG welding is immersed in 10% hydrochloric acid for 3 weeks.

FIG. 11 is an enlarged cross-sectional view showing an example in which the inner surface and the outer surface including the depression of the heat transfer tube are roughened.

FIG. 12 is an enlarged cross-sectional view showing an example in which the inner surface and the outer surface of the heat transfer tube including the depression are roughened.

FIG. 13 is an enlarged cross-sectional view illustrating an example in which the inner surface and the outer surface including the depression of the heat transfer tube are roughened.

FIG. 14 is an enlarged cross-sectional view showing an example in which the inner surface and the outer surface including the depression of the heat transfer tube are roughened.

FIG. 15 is an enlarged sectional view showing an example in which small depressions are formed on the inner and outer surfaces of the depressions of the heat transfer tube.

FIG. 16 is an enlarged cross-sectional view showing an example in which small projections are formed on the inner and outer surfaces of the depression of the heat transfer tube.

FIG. 17 is an enlarged sectional view showing an example in which a small dent is formed on the outer surface of the dent of the heat transfer tube.

FIG. 18 is an enlarged cross-sectional view showing an example in which small projections are formed on the outer surface of a depression of a heat transfer tube.

FIG. 19 is an enlarged sectional view showing an example in which a plurality of recesses having different sizes are formed on the outer surface of the heat transfer tube.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heat transfer tube 2 Depression 3 Smooth part 4 Convex part 10 Absorbent liquid 11 Falling liquid film 21 Plate material 22 Tube forming part 23 ERW welding part 24 High frequency coil 25 Welding line 26 Reducing part 31, 32 Welding line 35, 40, 41 recess 36,37 small recess 338,39 protrusion

──────────────────────────────────────────────────の Continuing on the front page (72) Michihiko Aizawa 603, Kandamachi, Tsuchiura-shi, Ibaraki Pref.Hitachi, Ltd., Tsuchiura Plant Hitachi, Ltd. (72) Inventor Takeshi Suzuki 128-7 Ogimachi, Aizuwakamatsu-shi, Fukushima Prefecture Inside Mitsubishi Shindo Copper Co., Ltd. (72) Inventor Masami Takahashi 128-7 Ogimachi, Aizuwakamatsu-shi, Fukushima Prefecture Mitsubishi Shindo Copper Co., Ltd. (72) Invention Person Yoshiji Saito 1-6-2 Ginza, Chuo-ku, Tokyo Mitsubishi Shindoh Co., Ltd. (56) References JP-A-7-208888 (JP, A) JP-A-4-172186 (JP, A) JP 60-108688 (JP, A) JP-A-64-46546 (JP, A) JP-A-1-108332 (JP, A) JP-A-6-58688 (JP, A) JP-A-3-99735 (JP, A) A) 307788 (JP, A) JP-A-5-340646 (JP, A) JP-A-1-134180 (JP, A) JP-A-7-24522 (JP, A) Jikken 46-6708 (JP, Y1) (58) Field surveyed (Int.Cl. ⁷ , DB name) F28F 1/06 F25B 37/00 F28F 1/10 F28F 1/12 F28F 1/42 F25B 37/00 F28F 1/40 B21D 53/08

Claims (4)

(57) [Claims] 1. A heat transfer tube having a plurality of recesses formed by plastic deformation processing on an outer surface of a tube wall, wherein the heat transfer tube has a smooth portion where the recess is not formed on a part of a peripheral surface of the tube wall.
The smooth portion is extended in the axial direction of the pipe, and the smooth portion is
The surface roughness of the outer wall of the tube excluding is 0.08μm ~ 100μ
m, the maximum surface roughness of the inner surface of the pipe wall is 0.04 μm
A heat transfer tube having a thickness of 10 μm . 2. A heat transfer tube having a plurality of recesses formed by plastic deformation processing on an outer surface of a tube wall, wherein the heat transfer tubes are disposed horizontally and in multiple stages at intervals. Has a smooth portion not formed, the smooth portion extending in the axial direction of the pipe, and a surface of the outer surface of the pipe wall excluding the smooth portion.
Surface roughness is 0.08μm ~ 100μm, also the inner surface of the tube wall
A heat transfer tube having a maximum surface roughness of 0.04 μm to 10 μm . 3. A step of forming a plurality of recesses in a region excluding both side edges of the band-shaped metal plate by plastic deformation processing, bending the band-shaped metal plate into a tubular shape and abutting both side edges, and pressing against the abutting portion. It has a process of applying high frequency welding while applying pressure ,
The step of forming the recess is by press working.
With a maximum surface roughness of 0.08 μm to 100 μm
And a concave shape with a maximum surface roughness of 0.04 μm to 10 μm
A method for manufacturing a heat transfer tube, characterized by processing with a combined mold . 4. A heat transfer tube is disposed in multiple stages horizontally and at intervals in a vessel into which the vapor of the medium to be absorbed is introduced, and the absorbing liquid flows down from above the heat transfer tube and flows down to the surface of the heat transfer tube. While absorbing the vapor of the medium to be absorbed into the absorbing liquid,
In an absorber for exchanging heat generated by an absorption reaction with a coolant flowing inside the heat transfer tube, the heat transfer tube has a plurality of concave portions formed by plastic deformation processing on an outer surface of the tube wall, and An absorber having a smooth portion in which the concave portion is not formed on a part of the lower surface of the tube, and the smooth portion extends in the axial direction of the tube.