JP2960827B2 - Heat transfer tube for absorber and manufacturing method thereof - 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 pipe provided in an absorber such as an absorption refrigerator or an absorption heat pump, and a method of manufacturing the same. In particular, the present invention relates to a heat transfer pipe for an absorber having improved heat exchange efficiency. The present invention relates to a method for easily manufacturing a heat transfer tube for an absorber.

[0002]

2. Description of the Related Art In general, as a heat transfer tube used in an absorber such as the absorption refrigerator or the absorption heat pump, a smooth tube having a circular cross section with a smooth inner and outer surface is employed. The performance was low and it was difficult to meet the demand for higher performance and smaller size of the absorber.

Therefore, the applicant of the present application has previously filed Japanese Patent Application
In JP-A-330709 (Japanese Patent Application Laid-Open No. 2-176378) and the like, a plurality of peaks and valleys extending in the longitudinal direction on the outer surface of the tube are alternately formed with a cross-sectional shape curved in the circumferential direction of the tube. A heat transfer tube for an absorber provided with a plurality of curved grooves extending in the direction is proposed. In such a heat transfer tube, when used by being arranged in a horizontal direction,
When the absorbing liquid dropped or sprayed on the outer surface of the pipe flows down in the circumferential direction of the pipe, a disturbance or convection phenomenon can be effectively caused to the absorbing liquid due to a change in the inclination angle, and the concentration of the absorbing liquid is reduced. The dark portion is well exposed to the outer surface, and the effect of absorbing water vapor, that is, the heat transfer performance can be improved.

[0004] However, even with such a heat transfer tube having a curved groove formed of a peak and a valley, it is still difficult to sufficiently secure the required heat transfer performance. Improvement was required.

Further, in the conventional heat transfer tube, the surface tension of the absorbing solution is relatively large, and when the surface of the heat transfer tube is caused to flow down in the circumferential direction of the tube, the width of the absorbing solution flowing downward as it goes downward in the circumferential direction of the tube. Since it gradually narrows, it is difficult to secure a wet area where an effective heat exchange action is exhibited, and a thirst surface is easily generated on the outer surface of the tube, and LiBr and the like in the absorbing solution are precipitated and absorbed on the thirst surface. There was also a problem that the water vapor absorption rate of the liquid and, consequently, the heat transfer performance were reduced.

[0006]

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide an absorbent in which an absorbent flowing down a pipe outer surface in a circumferential direction is advantageous in a pipe longitudinal direction. The heat transfer tube for an absorber that can exhibit more excellent heat transfer performance than the conventional heat transfer tube having a curved groove by being expanded to increase the wet area,
Another object of the present invention is to provide a method capable of easily manufacturing such a heat transfer tube for an absorber.

[0007]

According to the present invention, there is provided a heat transfer tube for an absorber in which an absorbing solution is dropped or sprayed on an outer surface of a tube and cooling water outside the tube is cooled by cooling water in the tube. A plurality of peaks and valleys extending in the longitudinal direction of the heat transfer tube are alternately formed with a curved cross-sectional shape in the circumferential direction of the tube, and a depth of each of the peaks and valleys is formed on the outer peripheral surface of the pipe. : D is 0.02 mm to 0.2 mm
And an absorber formed by forming a large number of fine grooves extending in the longitudinal direction of the heat transfer tube, wherein the ratio of the depth: d to the pitch: p in the circumferential direction of the tube: (d / p) is 0.1 to 1. The heat transfer tube is a feature thereof.

Further, the present invention provides (a) a first step of reducing the diameter of the soft tube material by subjecting the tube material to a first drawing process, and (b) dividing the tube material in the circumferential direction. By using a split die having a large number of fine grooves formed in a die hole surface, the split die can be moved forward and backward in a direction perpendicular to the center line of the pipe material that has passed through the first step, and formed in the die hole surface. By inserting the plug and performing the second drawing process, the fine groove forming part where a large number of fine grooves extending in the longitudinal direction are formed on the outer peripheral surface and the fine groove non-forming part are alternately arranged in the tube axis direction. A second step of forming; and (c) a tubular material which is divided in a circumferential direction, is advanced and retracted in a direction perpendicular to a center line of the tubular material having passed through the second step, and is opened and closed. A plurality of valleys and peaks each having By performing a third drawing process using a groove, a plurality of peaks and valleys extending in the longitudinal direction are formed with a greater depth and a circumferential pitch than the fine grooves, and a curved groove forming portion and a curved groove not formed And (d) reducing the diameter of at least one of the curved groove forming portion and the curved groove non-forming portion of the tube material having undergone the third step. , And a fourth step of making the outer diameters of the curved groove forming portions and the curved groove non-forming portions substantially the same.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view of a heat transfer tube 10 for an absorber according to an embodiment of the present invention, and FIG. 2 is a side view thereof. That is, the heat transfer tube 1
0 has a peak 12 and a valley 14 in the circumferential direction of the pipe.
Are alternately curved. In the present embodiment, the peaks 12 and the valleys 14 are 12
The ridges 12 and the valleys 14 are formed at substantially equal intervals in the circumferential direction, and the ridges 12 and the valleys 14 are formed linearly and parallel to the pipe axis direction.

By the way, the peaks 12 and the valleys 14
The specific dimensions such as the depth: d 'and the pitch: p' are not particularly limited, but the depth of the valley 14: d 'or the ratio of the depth to the pitch: d' / p '. If the value is too small,
It is difficult for an effective disturbance and stagnation effect to be exerted on the absorbing liquid flowing down the outer peripheral surface of the pipe.
If the value of the depth: d 'or the ratio of the depth to the pitch: d' / p 'is too large, the absorbent flowing down the outer peripheral surface of the pipe tends to stay in the valley portion 14 and the cross-sectional area of the pipe And the head loss increases.

Therefore, in order to obtain effective heat transfer performance,
The depth d 'of the valley 14 is set to 0.1 mm to 1.0 mm, and the ratio of the depth to the pitch of the valley 14 is d' / d /.
It is desirable that p 'be 0.01 to 0.5.

Further, the entire outer peripheral surface of the heat transfer tube 10 including the ridges 12 and the valleys 14 is corrugated in the circumferential direction of the tube, and as a result, as shown in FIG. The peak 12 and the valley 14 are provided on the outer peripheral surface thereof.
A large number of microgrooves 16 are formed with a groove depth: d and a pitch: p smaller than the curved grooves formed by. In this embodiment, the fine grooves 16 are formed linearly and parallel to the tube axis direction.

In the heat transfer tube 10 having such a structure, the curved groove formed by the peak 12 and the valley 14 causes
Since the inclination angle in the circumferential direction of the tube is changed, an effective disturbance and convection phenomenon are caused to the absorbing solution such as the aqueous solution of LiBr attached to the outer surface of the tube and caused to flow down in the circumferential direction of the tube. A portion having a high concentration of the absorbing liquid is satisfactorily exposed to the outer surface, and the effect of absorbing water vapor is improved.

Moreover, in the heat transfer tube 10, a number of fine grooves 16 extending in the tube axis direction are formed with respect to the tube outer peripheral surface, and the absorbing liquid flowing down the tube outer peripheral surface is filled with the fine grooves. In this case, the absorbent flowing into the fine groove 16 is guided by the fine groove 16 in the pipe axis direction and spreads. It becomes.

That is, the fine grooves 16 are formed with a small groove width, and a surfactant such as octyl alcohol is added to the absorbing liquid as is known, so that the wettability to the heat transfer tube 10 is improved. Therefore, the absorbing liquid that has entered the fine groove 16 is guided in the tube axis direction in the fine groove 16 by a capillary action based on surface tension (surface force or interfacial force).

Here, if the groove depth d is too shallow, a remarkable effect of spreading the absorbing liquid in the tube axis direction cannot be expected. If the groove depth d is too deep, the friction coefficient at the time of processing will be small. It becomes large and processing becomes difficult. Therefore,
The depth d of the fine grooves 16 needs to be set so as to satisfy the following (Equation 1). 0.02 mm ≦ d ≦ 0.2 mm (Equation 1)

Further, when the ratio d / p between the groove depth and the pitch of the fine grooves 16 is too small, the capillary effect of spreading the absorbing solution in the tube axis direction is unlikely to occur. The effect of the groove is reduced,
At the time of processing, the contact area between the tube material and the die increases, and processing becomes difficult. Therefore, the ratio d / p between the groove depth and the pitch of the fine grooves 16 needs to be set so as to satisfy the following (Equation 2). 0.1 ≦ d / p ≦ 1 (formula 2)

Although the cross-sectional shape of the fine groove 16 is not particularly limited, in the present embodiment, an upwardly arcuate portion and a downwardly arcuate portion having substantially the same radius of curvature are formed in the circumferential direction. In a corrugated plate shape. When the fine groove 16 is formed with a corrugated structure as described above, the radius of curvature: R of the upwardly arcuate portion and the downwardly arcuate portion is generally given by the relationship with the pitch of the fine groove: p. It will be set to 0.01 mm to 1 mm.

Therefore, in the above-described heat transfer tube 10 provided with such fine grooves 16, the fine grooves 16 allow the absorbing liquid flowing down the outer peripheral surface of the tube to be advantageously spread in the tube axial direction. Therefore, the wet area where the heat exchange action is exhibited can be advantageously secured, and the occurrence of a thirst surface on the outer surface of the tube can be prevented, and the decrease in the water vapor absorption rate due to precipitation of LiBr can be effectively eliminated. It is.

Therefore, in the heat transfer tube 10, the effect of improving the absorption of water vapor based on the turbulence and the turbulent flow exerted on the absorbing liquid by the curved groove formed by the peaks 12 and the valleys 14 is obtained. The heat exchange efficiency is remarkably improved by synergistically exerting the effect of increasing the wetting area based on the expansion effect in the tube axis direction exerted on the absorbing liquid by 16.

In addition, since the outer surface of the tube is made uneven by the fine grooves 16, a more effective disturbing action is exerted on the absorbing liquid flowing down the outer surface of the tube.
This can also contribute to prolonging the contact time with the outer surface of the tube, and further increase the absorption of water vapor supplied from the evaporator.

By the way, using a copper tube of JIS H3300, a heat transfer tube 10 of the structure of the present embodiment having dimensions and the like as shown in the following [Table 1] is manufactured, and its effective length (heat transfer tube is The length excluding the cylindrical portions provided at both ends in the pipe axis direction for attachment to the absorber): 500 mm, and set horizontally in the experimental absorber at 35 mm pitch with 5 rows per row. While cooling water as a cooling medium is circulated in five passes from the lower side, an aqueous solution of LiBr to which 250 ppm of octyl alcohol is added is passed through a dropping hole having a diameter of 2 mm to the top of the heat transfer tube 10. The heat transfer coefficient outside the tube was determined for the heat transfer tube 10 having such a structure by dropping it on the outer surface. The other main conditions for such an experiment are described in [Table 2] below.

[0024]

[Table 1]

[0025]

[Table 2]

Further, in order to compare with the heat transfer tube 10 of the present embodiment, a smooth tube having a circular cross section having neither a curved groove nor a fine groove,
Only a curved groove consisting of a peak and a valley is formed in the pipe wall portion, and a curved groove tube having no fine groove on the outer peripheral surface,
The same experiment was performed for each, and the heat transfer coefficient outside the tube was obtained.
The results are shown in FIG. 4 together with the results for the heat transfer tube 10 of the present embodiment.

In this experiment, it was confirmed that in the heat transfer tube 10 having the structure of the present embodiment, the absorbing liquid flowing down the outer surface of the tube is easily spread in the axial direction as compared with the smooth tube and the curved groove tube. Was. Also, from the results shown in FIG.
The heat transfer tube 10 of the present embodiment is about 40% higher than the smooth tube (Comparative Example 1), and 15% higher than the curved groove tube (Comparative Example 2).
It is recognized that a relatively high extra-tube heat transfer coefficient can be exhibited.

Incidentally, such a heat transfer tube 10 can be advantageously manufactured by, for example, the following manufacturing method.

That is, first, a soft copper tube 20 as a raw material wound in a coil shape is prepared, and as shown in FIG.
2 is inserted, and a first drawing process is performed by the support die 24. Thus, the soft copper tube 20 is processed into a 1 / 2H tempered tube (hereinafter, simply referred to as a tube material) 26.

The first drawing is performed by a pair of upper and lower first belt feeders 28, 28 located in front of the support die 24 and opposed to each other with the tube 26 interposed therebetween.
This is performed by applying a pulling force to the tube 26.
In the first belt feeder 28, for example, as shown in FIG. 6, an endless belt 30 is supported by a support core 32 disposed behind the core belt 30 and a tube shaft is moved by a core moving device such as a motor (not shown). , And the endless belts 30, 3 of the two belt feeders 28, 28.
The tube 26 is sandwiched between 0 and the tube 26 is pulled in the axial direction.

As the endless belt 30 used in the first belt feeder 28, a leather belt or the like is preferably used in order to advantageously obtain a frictional resistance against the tube material 26. Further, the pressing force (clamping force) of the first belt feeders 28, 28 against the tube 26 by the endless belts 30, 30 is desirably 40 to 55 kg / cm ² . It ’s
If the pressing force is less than 40 kg / cm ² , the drawing force is weak and the drawing becomes difficult, and the pressing force is 55 kg / cm ^2.
If m ² is exceeded, the frictional force between the endless belt 30 and the support core 32 and the load on the core moving device will increase, and in addition, the interstitial material 26 may be deformed into an elliptical shape.

Subsequently, a second support plug 34 is inserted into the pipe member 26 that has been subjected to the first drawing process, and a second drawing process is performed by the split die 36 having fine grooves. Note that the second support plug 34 is formed by a core metal 35.
A second belt feeder 40 connected to the first support plug 22 and disposed on the same axis as the first support plug 22, and disposed in front of the fine grooved die 36. , 40, the pipe member 26 is pulled in the axial direction, so that the second drawing process is performed following the first drawing process. Also, the second belt feeder 4
As 0 and 40, those having the same structure as the first belt feeders 28 and 28 can be adopted.

In this case, the fine grooved dice 36
As shown in FIGS. 7 and 8, is divided into three substantially equally in the circumferential direction, and each is advanced and retracted in a direction perpendicular to the center line of the pipe member 26 by a hydraulic cylinder or the like (not shown). It is possible. That is, in the split die 36 having the fine groove, the die 26 is moved forward and backward toward the tube 26 so as to be brought into contact with and separated from the outer peripheral surface of the tube 26. .

A large number of fine grooves extending in the axial direction are formed on the inner surface of the dice hole 38 of the divided dice 36 with fine grooves. The fine grooves formed on the inner surface of the die hole 38 of the split die 36 with fine grooves have the same pitch as the fine grooves 16 to be formed in the target heat transfer tube 10 as shown in FIG. The depth of the fine groove 16 to be formed in the heat transfer tube 10 is larger than the depth: d by a predetermined dimension so that the second drawing process is performed stably. I have.

Accordingly, as shown in FIG. 7, the divided dies 36 having such fine grooves are brought into contact with the surface of the tube material 26 and are drawn to cooperate with the second support plugs 34. On the other hand, the fine groove 16 is formed on the outer peripheral surface of the tube material 26. On the other hand, as shown in FIG. State. Then, at the time of such a second drawing process, the split die 3 having fine grooves is used.
As shown in FIG. 9, the fine groove forming portions 42 and the fine groove non-forming portions 44 are alternately formed with a predetermined length in the tube axis direction by opening and closing the opening 6. A grooved cylindrical tube 46 is obtained.

Further, a third support plug 48 is inserted into the finely grooved cylindrical tube 46 having been subjected to the second drawing, and a third drawing is performed by a split die 50 with a curved groove. Note that the third support plug 48 is provided with the core 35
The first and second support plugs 22 and 34 are connected to the first and second support plugs 22 and 34 by the
And between the second support plug 34 and the second belt feeders 40 and 40 on the same axis. Then, by pulling the tube material 26 in the axial direction by the second belt feeders 40, 40, a third drawing process is performed following the second drawing process.

In this case, the split die 50 having a curved groove is used.
As shown in FIGS. 11 and 12, is divided into three substantially equally in the circumferential direction, and each is perpendicular to the center line of the fine grooved cylinder 46 by a hydraulic cylinder or the like (not shown). In any direction. In other words, in the curved grooved dice 50, by being moved forward and backward toward the tube 26, they can be brought into contact with and separated from the outer peripheral surface of the tube 26. .

A plurality of curved grooves 54, 56 extending in the axial direction are respectively provided on the inner surface of the die hole 52 of the split die 50 with the curved groove and the outer surface of the third support plug 48.
Are formed corresponding to each other. The curved grooves 54 and 56 formed on the inner surface of the die hole 52 of the split die 50 with the curved groove and the outer surface of the third support plug 48
As shown in FIG. 14, each of the heat transfer tubes 10 is formed at the same pitch as the curved groove formed by the peak portion 12 and the valley portion 14 to be formed in the target heat transfer tube 10, and the third drawing process is performed. The depth of the curved groove to be formed in the heat transfer tube 10 is set to be larger than the depth: d 'of the curved groove by a predetermined dimension so that the heat transfer is performed stably.

Therefore, as shown in FIG. 11, such a divided die 50 having a curved groove is brought into contact with the surface of the cylindrical tube 46 having a fine groove, and is subjected to a drawing process. In cooperation, the cylindrical tube 26 with the fine groove is curved to form a curved groove composed of the peak portion 12 and the valley portion 14, while, as shown in FIG. By separating the dies 50 from the cylindrical tube 46 with fine grooves, the cylindrical tube 46 with fine grooves is unprocessed. And at the time of such a second drawing process,
By opening and closing the divided dies 50 with curved grooves, as shown in FIG. 13, the curved groove forming portions 58 and the curved groove non-forming portions 60 are alternately arranged in the tube axis direction with a predetermined length, respectively. The thus formed tubular tube 62 with a curved groove is obtained.

Thereafter, the modified die 66 is attached to the cylindrical tube 62 having the curved groove subjected to the third drawing process as described above.
In this way, diameter reduction processing for correcting the pipe diameter is performed. In addition, the modified die 66 is provided with the second belt feeders 40 and 4.
After the third drawing, a diameter reducing process is continuously performed by applying a pulling force by a belt feeder (not shown) or the like.

That is, in the cylindrical tube 62 having a curved groove formed by performing the second and third drawing processes, the minute groove and the curved groove are partially formed to form the minute groove and the curved groove. There is a dimensional difference in the outer diameter between the portion and the unformed portion. In order to correct this dimensional difference and eliminate it, a diameter reduction process is performed. In addition, in general, the undrawn portion has a larger diameter than the formed portion of the fine groove and the curved groove due to the second and third drawing processes. Diameter reduction processing for making the outer diameters substantially the same is performed.

Then, the outer diameter is made uniform by such diameter reduction processing, whereby the intended heat transfer tube 10 is obtained. In addition, the heat transfer tube 10 may be cut, if necessary, at a portion where the fine groove and the curved groove are not formed, and the heat transfer tube 10 having a predetermined length having such a non-formed portion at both ends in the axial direction. Becomes That is, the portion where the fine groove and the curved groove are not formed serves as a conduit connection portion when the heat transfer tube 10 is mounted on the absorber.

Therefore, according to the manufacturing method as described above, the first, second, and third drawing processes are continuously performed on the soft copper tube 20 as a raw material, whereby the tube material 2 is formed.
From 6, it is possible to easily and continuously manufacture the desired heat transfer tube 10 having the fine groove 16 and the curved groove.

Further, by opening and closing the divided dies 36 with the fine grooves and the divided dies 50 with the curved grooves, the portions where the fine grooves 16 and the curved grooves are formed and the portions where the curved grooves are not formed are alternately arranged in the pipe axis direction without stopping the processing. The heat transfer tube 10 can be easily formed, so that the mounting portions (pipe connection portions) to the absorber at both axial ends of the heat transfer tube 10 can be easily formed.

In this embodiment, the first belt feeder 28 disposed between the first support die 24 and the divided die 36 with fine grooves is used as a belt feeder for exerting a pulling force on the tube material. And a second belt feeder 40 disposed between the split die 50 having a curved groove and the correction die 66, and the pulling force required at the time of the first to third drawing processes is reduced. One belt feeder 28
And the second belt feeder 40 divides the pipe material so that the pipe material can be effectively prevented from being broken.
It also has the advantage that it is possible to produce a zero.

Although the embodiments of the present invention have been described above in detail, these are literal examples, and the present invention is not construed as being limited to such specific examples.

For example, the heat transfer tube 10 shown in the above embodiment
In the above, each of the curved groove composed of the peak portion 12 and the valley portion 14 and the fine groove 16 is formed as a straight groove extending parallel to the tube axis direction.
Either one or both may be formed as a spiral groove extending in the longitudinal direction of the tube at a predetermined angle with respect to the tube axis.

Further, the heat transfer tube 1 having such a spiral groove
In the case of 0, for example, a lead angle is given to the fine grooves and the curved grooves provided in the die holes 38 and 52 of the divided grooved dies 36 and the divided grooved dies 50, and the dies are rotated around the axis at the time of drawing. By doing so, it can be manufactured.

Further, the heat transfer tube 10 shown in the above embodiment is used.
In the manufacturing method of (3), the third support plug 48 was used to define the shape of the inner surface of the tube during the third drawing process for forming the curved groove. In this case, the drawing process can be performed only by using the split die 50 having the curved groove without using such a support plug.

If the outer diameter of the third support plug 48 is tapered in the axial direction, the position of the third support plug 48 can be changed by adjusting the length of the metal core 35 or the like. By adjusting the relative position of the split die with the curved groove 50 in the axial direction, the outer diameter and groove depth of the formed curved groove can be appropriately changed.

In addition, although not enumerated one by one, the present invention
Based on the knowledge of those skilled in the art, various changes, modifications, improvements and the like can be implemented in an embodiment,
It goes without saying that all such embodiments are included within the scope of the present invention, without departing from the spirit of the present invention.

[0052]

As is apparent from the above description, in the heat transfer tube for an absorber having the structure according to the present invention, the disturbance exerted on the absorbing liquid by the curved groove composed of the peak and the valley,
The effect of improving the absorption of water vapor based on the turbulence effect and the effect of increasing the wetting area due to the expansion in the axial direction of the absorption liquid exerted on the absorbing liquid by the fine grooves provided on the surfaces of the peaks and valleys Are synergistically exerted, whereby the heat exchange efficiency can be drastically improved.

Further, according to the manufacturing method of the present invention, in the longitudinal direction of the tubular material, the formed portions and the unformed portions of the curved grooves and the fine grooves can be formed alternately and continuously at appropriate intervals. Therefore, the intended heat transfer tube can be manufactured continuously and with excellent mass productivity.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a heat transfer tube for an absorber having a structure according to the present invention.

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

FIG. 3 is an enlarged view of a main part of the heat transfer tube shown in FIG.

FIG. 4 is a graph showing the results of measuring the heat transmittance of the heat transfer tube having the structure of the present embodiment as shown in FIG. 1, together with a comparative example.

FIG. 5 is an explanatory longitudinal sectional view illustrating a method of manufacturing the heat transfer tube for an absorber shown in FIG. 1 according to the present invention.

FIG. 6 is an explanatory sectional view showing a structure of a belt feeder used when performing the manufacturing method as shown in FIG.

FIG. 7 is an explanatory cross-sectional view showing a structure of a fine grooved dice used for performing the manufacturing method as shown in FIG.

8 is an explanatory view showing another operation state of the fine grooved dice shown in FIG. 7;

FIG. 9 is a side view showing a finely grooved cylindrical tube manufactured by a second drawing process.

FIG. 10 is an explanatory diagram showing a processing state of a pipe material by a divided die with fine grooves shown in FIG. 7;

FIG. 11 is an explanatory cross-sectional view showing a structure of a split die with a curved groove used in performing the manufacturing method as shown in FIG.

FIG. 12 is an explanatory view showing another operation state of the curved grooved dice shown in FIG. 11;

FIG. 13 is a side view showing a curved grooved tubular tube manufactured by a third drawing process.

FIG. 14 is an explanatory view showing a processing state of a pipe material by a curved groove-divided die shown in FIG. 11;

DESCRIPTION OF SYMBOLS 10 Heat transfer tube 12 Crest portion 14 Valley portion 16 Micro groove 22 First support plug 24 First support die 26 Tube material 28 First belt feeder 34 Second support plug 35 Core metal 36 Split die 38 Die hole 40 Second belt feeder 42 Micro-groove forming portion 44 Micro-groove non-forming portion 46 Micro-grooved cylindrical tube 48 Third support plug 50 Divided die with curved groove 52 Dice hole 58 Curved groove forming portion 60 No curved groove formed Part 62 Tubular tube with curved groove 66 Correction die

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Haruo Tanaka 5-11-3 Shimbashi, Minato-ku, Tokyo Sumitomo Light Metal Industries Co., Ltd. (72) Inventor Masahiro Furukawa 2--18 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Inventor Kazuhiro Yoshii 2--18 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (56) References JP-A-2-176378 (JP, A) JP-A Sho 64-41779 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F25B 37/00 B21D 9/14 B21D 15/02 F28F 1/06 F28F 1/10

Claims (2)

(57) [Claims] An absorbent is dropped or sprayed on an outer surface of a tube,
A heat transfer tube for an absorber for cooling an absorbing liquid outside a tube by cooling water inside the tube, wherein a plurality of peaks and valleys extending in a longitudinal direction of the heat transfer tube are alternately formed with a cross-sectional shape curved in a circumferential direction of the tube. The depth: d is 0.02 mm to 0.2 mm, respectively, and the ratio of the depth: d to the pitch in the pipe circumferential direction: p is (d / p) is 0.1
A heat transfer tube for an absorber, wherein a number of fine grooves extending in the longitudinal direction of the heat transfer tube are formed. 2. A first step of reducing the diameter of the soft tubing by subjecting a soft tubing as a raw material to a first drawing process, and a process of dividing the tubing in the circumferential direction through the first step. It can be moved back and forth in a direction perpendicular to the center line,
Using a split die having a large number of fine grooves formed in the die hole surface, inserting a plug into the inner hole of such a tube material, and performing a second drawing process, whereby a large number of fine grooves extending in the longitudinal direction on the outer peripheral surface are formed. A second step of alternately forming the micro-groove forming portions and the non-micro-groove forming portions in which the grooves are formed in the pipe axis direction; and To move back and forth in the direction perpendicular to
A plurality of valleys and valleys extending in the longitudinal direction are formed by performing a third drawing using a split die in which a plurality of valleys and ridges having a curved surface shape in the die hole surface are alternately formed in the circumferential direction. A third step of alternately forming a curved groove forming portion and a curved groove non-formed portion in which the portion is formed with a depth and a circumferential pitch greater than the fine groove in the tube axis direction; A fourth step of reducing the diameter of at least one of the curved groove forming portion and the curved groove non-formed portion in the passed pipe material to make the outer diameters of the curved groove formed portion and the curved groove non-formed portion substantially the same; A method for producing a heat transfer tube for an absorber, comprising: