JPH08159605A - Heat-transfer tube for absorber - Google Patents

Abstract

PURPOSE: To provide a weight-reducible heat-transfer tube for an absorber which is excellent in a heat-transfer ability without lowering in an assembling workability to amount the tube to a refrigerator. CONSTITUTION: Absorber heat-transfer tubes 10 which comprise a plurality of horizontally laid out tubes are provided with a plurality of recessed parts 11 which extend in the tube axial direction and laid out intermittently where the center P of the recessed parts 11 between the rows of adjacent tubes in the tube peripheral direction and the center Q of the other rows between the recessed parts 11 are identical to each other about the tube axial direction while the ration Lo /L between the length Lo of the overlapped areas of the recessed parts in the adjacent rows in the tube peripheral direction and the length L of the recessed parts range from 0.2 to 0.8. The ratio between the width in the tube peripheral direction of the recessed parts and the width of recessed parts 12 between the recessed parts ranges from 0.5 to 1.5mm where the length of the recessed parts ranges from 10 to 50mm. An even area 13 having no recessed part which includes both ends in the longitudinal direction is installed to at least two locations. The ratio between a radius of curvature of a circle comprising an envelop which connects the tops of the projected parts between the recessed parts in the cross section which intersects to the tube axis at a right angle and a radius of curvature of the even area is specified to range from 0.97 to 1.03.

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 for an absorber used in an absorber of an absorption heat exchanger such as an absorption refrigerator and an absorption chiller / heater, and more specifically, a heat transfer performance. Also, the present invention relates to a heat transfer tube for an absorber having excellent assembling property.

[0002]

2. Description of the Related Art In an absorption heat exchanger such as an absorption refrigerator,
The inside of the container is kept vacuum, the refrigerant is evaporated at a low temperature, and cold water is taken out by the latent heat of evaporation and used for air conditioning.

The absorber and the evaporator are housed in an integral body, and in order to continuously obtain evaporation, the refrigerant vapor generated in the evaporator is dispersed on the surface of the heat transfer tube of the absorber. The inside of the body is maintained at a certain degree of vacuum. Therefore, in order to improve the refrigerating capacity of the heat exchanger, it is necessary to increase the amount of refrigerant vapor generated in the evaporator and increase the amount of absorption, that is, the absorption capacity. Regarding the increase of the absorption capacity, the improvement of the performance of the heat transfer tube is the most effective means, and heat transfer tubes having various shapes have been studied and proposed.

For example, in the technique disclosed in Japanese Utility Model Laid-Open No. 2-89270 and Japanese Patent Application Laid-Open No. 2-176378, vertical grooves which are continuous in the pipe axis direction are arranged and peaks and valleys formed in the direction perpendicular to the pipe axis. The parts have a shape with curvatures that form a predetermined relationship.

These are characterized in that they do not hinder the swinging of the absorbing liquid in the pipe axis direction caused by Marangoni convection, and a further disturbing effect is obtained when the absorbing liquid crosses the troughs and the ridges. .

Further, a technique for forming intermittent irregularities is disclosed in Japanese Utility Model Publication No. 46-67080 and Japanese Patent Publication No. 5-22838. These are characterized in that the absorbent is disturbed by intermittent irregularities or the residence time is lengthened.

[0007]

However, although the above-mentioned conventional technique can improve the heat transfer performance to some extent, it has various problems as described below.

First, in a heat transfer tube having a groove having continuous grooves in the tube axial direction as disclosed in Japanese Utility Model Laid-Open No. 2-89270 and Japanese Patent Application Laid-Open No. 2-176378, heat transfer depends on the installation direction of the tube. There is a difference in performance.

Specifically, when the heat transfer tubes are arranged so that the valleys are located above the vertical direction, the absorbing liquid is likely to collect in the valleys and the absorbing liquid cannot be discharged properly. The absorption liquid with reduced temperature remained, resulting in deterioration of heat transfer performance. In addition, when the flow rate of the absorbing liquid increases, as shown in FIG.
As shown in 0, the absorbing liquid 1 may drop out at the mountain portion of the lower part of the tube, and in this case also, the heat transfer performance was deteriorated. In order to prevent these adverse effects, it is effective to arrange the row of tube groups so that the peaks are at the top, but in this case, when inserting the tubes into the refrigerator, It is necessary to proceed with the work while checking, and this puts a great burden on the worker.

Further, as the depth of the valley becomes deeper, the amount of retention of the absorption liquid increases, so that the required circulation amount of the absorption liquid for driving the refrigeration cycle increases and the weight of the device increases. .

Next, the heat transfer tube described in Japanese Utility Model Publication No. 46-67080 has intermittent recesses, but as shown in FIG. 11, the recesses 2 are adjacent to each other in a row in the circumferential direction of the tube. When the recesses of the corresponding rows are overlapped with each other, and viewed in the tube axis direction, there is a band-shaped region in which there are no recesses.
For this reason, when Marangoni convection occurs due to the absorption of the refrigerant vapor, the flowing down absorbing liquid rises in a streak shape and flows down while oscillating in the pipe axis direction.
As shown in Fig. 5, there are some places where the absorbent does not flow into the recess. As a result, there is a drawback in that the absorption liquid does not sufficiently stay and improvement in absorption performance cannot be expected.

The heat transfer tube described in Japanese Examined Patent Publication No. 5-22838 is an improved version of the structure of the heat transfer tube described in Japanese Utility Model Publication No. 46-67080, but it has the following problems. That is, the heat transfer tube of Japanese Examined Patent Publication No. 5-22838 has a structure designed to allow the absorbing liquid to stay on the surface of the pipe for a long time as much as possible. The absorption liquid flows down while bypassing the flat portion between them.

With such a structure, the retention time of the absorption liquid can be lengthened and the retention amount of the absorption liquid can be increased, but since the absorption liquid stays on the tube surface more than necessary, the absorption liquid is absorbed as described above. The required circulation amount of the liquid increases, and the weight of the device increases. Further, since the flow path of the absorbing liquid is determined by the concave portion and the absorbing liquid does not flow over the top of the protrusion to flow down, the top of the protrusion does not come into contact with the absorbing liquid. Therefore, the heat transfer area of the heat transfer tube cannot be effectively secured, and there is a limit to improving the heat transfer performance.

The present invention has been made in view of the above problems, and has excellent heat transfer performance, and increases the weight of the device without deteriorating the workability when assembling the pipe to the refrigerator. It is an object of the present invention to provide a heat transfer tube for an absorber, which has an excellent characteristic of being able to prevent the above.

[0015]

A heat transfer tube for an absorber according to the present invention includes a plurality of heat transfer tubes for an absorber used in an absorber configured by horizontally arranging a plurality of tubes horizontally. The recesses are arranged intermittently in the pipe axis direction, and in the recess row adjacent to each other in the pipe circumferential direction, the centers of the recesses in one row and the centers between the recesses in the other row coincide with each other in the pipe axis direction. The ratio L ₀ / L of the length L ₀ of the overlapping portion of the recesses to the length L of the recesses in the rows adjacent to each other is 0.2 to 0.8,
The tube circumferential direction of the convex portion between the width W ₁ and the recess of the tube circumferential direction of the concave portion W ₂
And the ratio W ₁ / W ₂ is 0.5 to 2.5, and the depth h of the recess is
Is 0.5 to 1.5 mm, and the length L of the recess is 10 to 5
It is characterized by being 0 mm.

In this case, a non-concave region having no recess is provided in at least two sites including both ends of the pipe in the longitudinal direction of the pipe, and an envelope curve connecting the peaks of the protrusions between the recesses in the cross section orthogonal to the pipe axis. The ratio R ₀ / R of the radius of curvature R _{0 of the} circle consisting of and the radius of curvature R of the non-concave region is 0.97 to 1.03.
Can be.

[0017]

With this configuration, the heat transfer tube for an absorber according to the present invention has the following actions. First, regarding the rows of the intermittent recesses extending in the pipe axis direction, the ratio of the length of the recesses in one row to the length of the recesses in the other row adjacent to this is It is arranged so as to have a predetermined value.

In a flute having a continuous groove in the pipe axis direction,
As described above, the performance varies depending on the installation direction, but since the heat transfer tube for an absorber according to the present invention has intermittent recesses, it has no directionality and is substantially constant even if the top surface of the tube is arranged in any direction. Shows the heat transfer performance of.

Further, depending on the length and the positional relationship of the concave portion, there arises a problem as in Japanese Utility Model Laid-Open No. 46-67080, but in the present invention, since these are set in an appropriate range, the absorbing liquid flowing down is surely. The absorbent flows into the recesses, the absorption liquid is reliably captured in the recesses, and the absorption liquid stays in the recesses in an appropriate amount. Further, in the present invention, unlike in Japanese Patent Publication No. 5-22838, a fixed flow path for the absorbing liquid is not formed, and since the absorbing liquid flows down while uniformly wetting the pipe wall, high absorption performance is obtained. can get.

[0020]

The present invention will be further described below. FIG.
Is a front view showing a heat transfer tube 10 for an absorber according to an embodiment of the present invention, and FIG. 2 is a sectional view orthogonal to the tube axis. In the heat transfer tube 10 of the present invention, recesses 11 extending in the tube axis direction are intermittently formed in the tube axis direction on the peripheral surface thereof, and the recesses 11 are arranged in rows in the tube axis direction. . A plurality of such recess rows are provided in the circumferential direction. Recess 11
The area between them becomes the convex portion 12. Further, a non-concavo-convex region (hereinafter referred to as a flat portion 13) having no such concavity and convexity is provided in the pipe end portion or an appropriate region in the pipe axial direction.

The recesses 11 are arranged so that the center position P thereof coincides with the center position Q between the recesses 11 of the adjacent rows in the tube axis direction. This recess 11
It is said that the center position P of the position P and the center position Q between the recesses 11 in the adjacent rows coincide with each other in the pipe axis direction.
It means that the position Q is located in the cross section orthogonal to the tube axis at. Further, it is not necessary that the position P and the position Q coincide with each other in the pipe axis direction in this manner, but it is sufficient that they substantially coincide with each other.

In the rows adjacent to each other in the pipe circumferential direction, the recesses 11 overlap each other at their ends, and the sum L ₀ of the lengths L ₁ and L ₂ of the overlapping portions and the length L of the recesses 11 are formed. Ratio L ₀
/ L is 0.2 to 0.8. Also, the depth h of the recess 11
Is 0.5 to 1.5 mm, and the length L of the recess is 10 to 5
It is 0 mm. Furthermore, the ratio W ₁ / W ₂ of the tube circumferential direction of W ₂ of the convex portion 12 between a width W ₁ and the recess of the tube circumferential direction of the concave portion 11 is 0.
5 to 2.5.

In the present invention, the ratio L ₀ / L between the overlapping length L ₀ of the recesses in the adjacent rows in the pipe circumferential direction and the recess length L is 0.2.
Although it is set to 0.8, if L ₀ / L is larger than 0.8, the processing becomes complicated, but the performance is almost the same as that of the heat transfer tube having continuous recesses, and L ₀ / L is more than 0.2. If it is small, the absorption liquid will not be sufficiently captured as described above. Therefore, L ₀ / L is set to 0.2 to 0.8.

Further, in the present invention, the depth and length dimensions of the concave portion and the width ratio of the concave portion and the convex portion are set within predetermined ranges. The depth of the recess is 0.5 to 1.5 mm. When the depth of the recess is smaller than 0.5 mm, the absorption liquid stays short and the absorption liquid flows down without being able to perform a predetermined absorption. This is because. Further, if the depth of the recess is larger than 1.5 mm, the absorption liquid stays too long, the absorption flow rate on the pipe surface increases, the required circulation amount of the absorption liquid increases, and the weight of the device increases. The depth of the recess is 0.5 to 1.5 mm
With this, the absorbing liquid can be appropriately retained. If the length of the concave portion is longer than 50 mm, the absorption flow rate on the surface of the pipe increases and the above-mentioned problem occurs, and further, the performance varies depending on the installation direction of the pipe. If the length of the concave portion is shorter than 10 mm, the number of processed portions of the concave portion increases, but the performance cannot be improved so much.

Next, if the ratio W ₁ / W ₂ between the width W ₁ of the concave portion in the circumferential direction of the pipe and the width W ₂ of the convex portion in the circumferential direction of the pipe is smaller than 0.5, the amount of the absorbed liquid retained is sufficient. Therefore, the absorption performance decreases. On the other hand, if W ₁ / W ₂ is larger than 2.5, the flow passage area of the cross section perpendicular to the pipe axis becomes too small, and the pressure loss of the cooling water in the pipe becomes large. Although the cooling water is transferred by an electric pump, if the pressure loss becomes large, a pump having a large output is required, and the total energy efficiency of the device is reduced.

When W ₁ / W ₂ is 0.5 to 2.5, the absorbing liquid is retained appropriately, and the pressure loss of the cooling water in the pipe becomes an appropriate value.

On the other hand, according to the present invention, the non-concave area (smooth portion: a portion having no recess) is provided at least at two or more locations including both ends of the tube in the longitudinal direction, so that the refrigerator can be easily attached to the tube sheet. Becomes Further, the smooth portion can be arranged at a position corresponding to the baffle plate (baffle plate) of the refrigerator. Therefore, it is possible to reduce the clearance between the hole of the tube sheet and the tube, and it is possible to suppress the fretting corrosion of the tube caused by the rubbing of the tube and the tube sheet due to vibration during operation of the refrigerator.

If the ratio R ₀ / R of the radius of curvature R _{0 of the} circle formed by the envelope line connecting the tops of the convex portions in the cross section to the radius of curvature R of the non-concave region is larger than 1.03, At the time of insertion work, the pipe is easily caught in the hole of the tube sheet, which makes insertion difficult and the workability is significantly reduced. R ₀ / R is 0.97
If it is smaller, the cross-sectional flow passage area of the pipe becomes smaller and the pressure loss becomes smaller, so that the above-mentioned overall energy efficiency of the device lowers. In the heat transfer tube of the present invention, R ₀ / R is set to 0.
Since it is 97 to 1.03, the pipe can be inserted smoothly without getting caught in the hole of the tube plate during the insertion work of the pipe,
The workability is good, and the pressure loss is not increased due to the reduction of the flow passage cross-sectional area.

Next, the results of manufacturing the heat transfer tubes according to the examples of the present invention and comparing the characteristics thereof with the comparative examples will be described.

As the present example and comparative example, a raw tube made of phosphorous deoxidized copper (JIS H3300 C1201) was used, and the concavo-convex process was performed using the apparatus having the structure shown in FIG. 8 (a). . That is, in this apparatus, the die 5, the openable split die 6 and the finishing die 7 are arranged in the moving direction of the pipe 4, and the pipe 4 is sequentially drawn.

As shown in FIG. 8 (b), the split die 6 is designed to be radially divided from the center of the split die 6 to be assembled, and the split die 6 is angled β with respect to the pipe in the circumferential direction of the pipe.
There are provided a drive mechanism (not shown) for making a swivel motion and an opening / closing mechanism (not shown) for expanding and contracting the split die 6 in the radial direction of the pipe. While pulling out the tube 4 in the direction of the arrow in the figure,
The drive mechanism reciprocates the split die 6 at a constant cycle, and the opening / closing mechanism opens and closes, whereby unevenness processing for forming a recess is performed.

Further, a finishing die is provided downstream of the recess processing mechanism in the pipe withdrawing direction, and the smooth portion which is not subjected to the uneven processing is sized to a predetermined size.

In this embodiment, the device of a single turnable open / close die is disclosed, but this may be a mechanism in which a plurality of open / close dies are arranged in tandem with their phases shifted in the rotational direction.

The tubes of this example and the comparative example were subjected to heat treatment at 250 ° C. for 1 hour in a reducing atmosphere as a degreasing treatment after the above steps. Further, the dimensions of the heat transfer tube are such that the outer diameter of the smooth portion is 16 mm and the wall thickness is 0.7 mm, the outer diameter of the uneven portion is 15.7 to 16.0 mm, and other dimensions are as shown in Table 1 below. . Comparative Example 1 is a flute tube having continuous recesses, and Comparative Example 2 is a smooth tube, that is, a tube having no uneven portion.

In Table 1, the ratio L ₀ / L of the overlapping length L ₀ of the recesses in the adjacent rows in the pipe circumferential direction and the recess length L is L ₀ / L.
Is processed to be about 1.0.

[0036]

[Table 1]

The tubes of the above-mentioned Examples and Comparative Examples were arranged in one row × 10.
The heat transfer performance was measured under the measurement conditions shown in Table 2 by arranging in stages. The absorption capacity of the heat transfer tube is substantially proportional to the heat transfer performance, and the higher the heat transfer performance, the higher the absorption capacity.

Regarding the heat transfer performance, the heat transfer performance was evaluated by arbitrarily setting and arranging the tubes one by one. As shown in FIG. 3, the heat transfer tube of the comparative example has high performance, but the variation in performance is about 12%, and the variation depending on the installation direction of the tube is large. On the other hand, Examples 1 and 2 of the present invention show high heat transfer performance, and the variation in performance is as small as about 5% or less.

[0039]

[Table 2]

Further, an example in which the liquid flow-down characteristics of the tubes of Examples 1 and 2 and Comparative Example 1 are examined will be described. FIG. 4 is a schematic diagram showing an apparatus for examining the liquid flow-down characteristics. A certain amount of water is dropped from the spray pipe 21 to the pipe 23, and the range in which the water flows from the lower part of the pipe to the floor surface 24 is measured and sprayed. Tube 21
The value obtained by subtracting from the sprayed length of, that is, the liquid cut length is measured.

FIG. 5 shows the liquid cut length when the tube is tilted. The liquid cut length increases as the heat transfer tube tilts, but Comparative Example 3 is different from Examples 1 and 2. The rate of increase in the liquid breakage length is large. That is, the heat transfer tube of the present invention has excellent characteristics that the wetted area does not decrease so much even if the refrigerator has a slight inclination, and the performance hardly deteriorates. In a large refrigerator, since the pipe is long, it may be bent by its own weight, and the device may be slightly inclined when the refrigerator is installed. In such a case, the performance of the conventional heat transfer tube is likely to deteriorate, but the performance of the heat transfer tube of the present invention does not occur due to the inclination of the tube as described above.

Next, an example in which the liquid retention, the pipe passage area, the heat transfer performance, and the pressure loss with respect to the dimensions of the concave portion and the convex portion are investigated will be described.

FIG. 6 shows the ratio of the width W ₁ of the concave portion to the width W ₂ of the convex portion, W
It is an example of investigating the retention amount of the absorbing liquid with respect to ₁ / W ₂ and the flow path area in the pipe, and shows comparative values when a smooth pipe is used as a reference. The depth h of the recess is 1 mm, and the length L of the recess is 30 mm.

W ₁ is the distance between the inflection points of the concave portion, and W ₂ is the distance between the inflection points of the convex portion. The absorbing liquid used has a concentration of 55%, and the retention amount of the liquid is obtained by calculating the difference between the flow amount of the absorbing liquid sprayed on the pipe and the absorbing liquid flowing down from the lower part of the pipe, and calculating the adhesion amount per unit time. .

If W ₁ / W ₂ is less than 0.5, the flow passage area in the pipe is large, but the amount of liquid retained is small. W ₁ / W ₂ is 2.5
If it becomes larger, the amount of liquid retained becomes larger, but on the other hand, the flow passage area in the pipe becomes too small. Since the pressure loss of the cooling water passing through the pipe increases as the flow area in the pipe decreases,
The required pump power increases, and the overall efficiency of the refrigerator decreases as described above.

When W ₁ / W ₂ is 0.5 to 2.5, the amount of liquid retained can be increased without causing a large decrease in the flow path area in the pipe.

Next, an example of investigating the heat transfer performance and the pressure loss with respect to the depth h of the recess will be shown. The conditions for performance evaluation were the same as those in Table 2 above. Also, W ₁ / W ₂ is 2,
The length of the recess was 30 mm.

As shown in FIG. 7, the depth h of the recess is 0.5.
If it is less than mm, the amount of retention of the absorbing liquid is small and the performance is largely deteriorated. The performance improves as the depth h of the recess increases, but even if the depth h of the recess exceeds 1.5 mm, the performance is not improved so much, but the pressure loss in the pipe increases. As a result, the overall efficiency of the refrigerator decreases.

Next, an example of investigating the influence of the length L of the recess on the heat transfer performance will be shown. Table 2 shows the conditions for performance evaluation.
The flow rate of the absorption liquid is 0.05mg
The performance was evaluated at a constant value of / m · s. In addition, here W ₁
/ W ₂ was 2, h was 1.0 mm, and the length of the convex portion was set to be shorter than the length L of the concave portion by approximately 5 to 10 mm.

FIG. 9 shows the relationship between the length L of the recess and the heat transfer performance. If L is larger than 50 mm, there will be large variations in performance depending on the tube installation direction. On the other hand, as L becomes smaller, the variation due to the installation direction of the pipe tends to decrease, but when it becomes smaller than 10 mm, the difference is not recognized and it is necessary to open and close the opening and closing die frequently, and the control of opening and closing becomes troublesome. Therefore, productivity is reduced.

When L is 10 to 50 mm, it is possible to perform processing without causing variations in performance and without reducing productivity.

Finally, the relationship between the ratio L ₀ / L between the overlapping length L ₀ of the recesses in the adjacent rows in the pipe circumferential direction and the length L of the recesses and the heat transfer performance outside the pipe will be described.

In this case, W ₁ / W ₂ is 2, and h is 1.0 mm. FIG. 12 is a diagram showing the relationship between L ₀ / L and the heat transfer coefficient outside the pipe. The flow rate of the absorbing liquid is 0.05 mg / m · s.
It is constant. If L ₀ / L is larger than 0.8, the heat transfer coefficient outside the tube tends to decrease. On the other hand, when L ₀ / L is less than 0.2, the increase in the heat transfer coefficient outside the pipe hardly occurs, but on the other hand, there is a difference in the performance depending on the installation direction of the pipe, such as the heat transfer pipe having the above-mentioned continuous recess. ing. Therefore, 0.2 to 0.8 is an appropriate range for L ₀ / L.

In the heat transfer tube of the present invention described above, the cross-sectional shape of the concave portion and the convex portion may be a substantially trapezoidal shape having a substantially flat tip, but in order to allow the absorbing liquid to flow down smoothly, an arc shape such as an ellipse is used. Then, it is even more effective.

Further, although copper is used as the tube material in the present embodiment, it goes without saying that the present invention can be applied to other metal materials, for example, iron heat transfer tubes.

[0056]

As described above, in the heat transfer tube for absorption and absorption according to the present invention, since the continuous recesses are arranged at proper positions in the tube axis direction, it is possible to suppress variations in the flow of the absorbing liquid. Since the absorbing liquid can be retained appropriately, the variation in performance depending on the installation direction of the pipe is small.
Furthermore, since the size of the recess is optimized, the absorption liquid can be retained appropriately in the pipe, the pressure loss of the cooling water in the pipe can be appropriately suppressed, and the refrigerator has a slight inclination. Even so, there is little variation in performance. Further, as described in claim 2, by setting the ratio of the radius of curvature R ₀ of the concavo-convex processed portion and the radius of curvature R of the substantially smooth portion to an appropriate value, insertability of the pipe into the refrigerator, that is, assembling Workability is improved.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an appearance of a heat transfer tube according to the present invention.

FIG. 2 is a cross-sectional view of a cross section of a heat transfer tube according to the present invention which is perpendicular to the tube axis, in which AA is a cross-sectional view of an uneven processed portion and BB is a cross-sectional view of a non-uneven region.

FIG. 3 shows external heat transfer coefficients (vertical axis) with respect to the absorbed liquid flow rate (horizontal axis) of the heat transfer tube according to the example and the heat transfer tube of the comparative example.

FIG. 4 is a schematic diagram of an apparatus for investigating liquid flow-down characteristics with respect to the inclination of a tube.

[Fig. 5] Liquid flow-down characteristics with respect to pipe inclination (liquid break length)
FIG.

FIG. 6 is a diagram showing a liquid flow rate and a flow path area ratio in a pipe with respect to a ratio W ₁ / W ₂ of a width W ₁ of a concave portion and a width W ₂ of a convex portion.

FIG. 7 is a diagram showing the ratio of the heat transfer coefficient outside the tube and the pressure loss ratio (smooth tube ratio) with respect to the depth h of the recess.

FIG. 8 is a schematic view showing an apparatus for manufacturing the heat transfer tube of the present invention.

FIG. 9 is a diagram showing the ratio of the heat transfer coefficient outside the tube to the length L of the recess.

FIG. 10 is a schematic diagram showing a state in which the absorbing liquid causes dropouts in the heat transfer tube according to the conventional technique.

FIG. 11 is a diagram showing a state in which a heat transfer tube according to a conventional example is flowing down an absorbing liquid.

FIG. 12 is a diagram showing a relationship between a ratio L ₀ / L between an overlapping length L ₀ of recesses in adjacent rows in the pipe circumferential direction and the length L of the recesses and the heat transfer performance outside the pipe.

[Explanation of symbols]

1; Absorbing liquid 5; Dies 6; Retractable split dies 7; Finishing dies 10; Pipes 11; Recesses 12; Convex parts 13; Smooth parts 14; Envelopes 21 connecting the tops of the convex parts 21; Scattering pipes 22; Flowing liquids 23 Pipe 24; floor surface W ₁ ; width of concave portion W ₂ ; width of convex portion h; depth of concave portion R; radius of curvature of concave and convex portion R ₀ ; radius of curvature of smooth portion θ; inclination angle of pipe X; liquid cut length Size β: Retractable split die rotation angle L ₀ ; Length of overlap between recesses in adjacent rows in the pipe circumferential direction L: Length of recess

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomio Higo 65 Hirazawa, Hadano City, Kanagawa Prefecture Kobe Steel Works Hadano Plant (72) Inventor Masashi Ishida 1-2-2 Marunouchi, Chiyoda-ku, Tokyo Stock Company Kobe Steel, Tokyo Head Office

Claims (2)

[Claims] 1. A heat transfer tube for an absorber used in an absorber configured by arranging a plurality of tubes horizontally, wherein a plurality of recesses extending in the tube axis direction are intermittently arranged in the tube axis direction, and a tube circumference is provided. The center of the recesses in one row in the row of recesses adjacent in the direction,
The center between the recesses in the other row coincides with the tube axis direction,
The ratio L ₀ / L between the length L ₀ of the overlapping portion of the recesses and the length L of the recesses in the rows adjacent to each other in the pipe circumferential direction is 0.2 to 0.8, and the width W ₁ of the recesses in the pipe circumferential direction is W _1. And the ratio W ₁ / W ₂ of the convex portion between the concave portion and W _{2 in} the tube circumferential direction is 0.5 to 2.5, the depth h of the concave portion is 0.5 to 1.5 mm, and Length L is 1
A heat transfer tube for an absorber, which has a length of 0 to 50 mm. 2. An envelope in which a non-concave region having no recess is provided in at least two portions including both ends of the pipe in the longitudinal direction of the pipe, and the peaks of the protrusions between the recesses in a cross section orthogonal to the pipe axis are connected. The ratio R ₀ / R of the radius of curvature R _{0 of the} circle formed by the line to the radius of curvature R of the non-concave / convex region is 0.97 to 1.03.
The heat transfer tube for an absorber according to claim 1, wherein: