JPH09113164A - Heat transfer tube for absorber - Google Patents

Abstract

(57) Abstract: [PROBLEMS] To provide a heat transfer tube for an absorber, which has a high heat exchange efficiency and can suppress the pressure loss in the tube and the required filling amount of the absorbing liquid to be low. SOLUTION: In a heat transfer tube for an absorber in which an absorbing liquid is dropped or sprinkled onto the outer surface of the pipe and the absorbing liquid outside the pipe is cooled by cooling water in the pipe, a mountain portion extending in the pipe axial direction on the outer surface of the pipe. Is formed with a curved surface shape of an arc in the pipe circumferential direction, and the radius of curvature of the crests and / or the depth of the troughs formed between the crests are made different.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a heat transfer tube for an absorber, which is piped in an absorber such as an absorption refrigerator or an absorption heat pump,
In particular, the present invention relates to a heat transfer tube for an absorber having excellent heat exchange efficiency while keeping the pressure loss in the tube and the required amount of absorbing liquid low.

[0002]

BACKGROUND ART Generally, a smooth tube having a circular cross section with a smooth inner and outer surface is adopted as a heat transfer tube used in an absorber such as the absorption refrigerator or the absorption heat pump. However, since such a smooth tube has low heat transfer performance, it has been difficult to meet the demand for higher performance and smaller size of the absorber. Further, in such a smooth pipe, the width of the absorbing liquid which is caused to flow down the pipe outer peripheral surface in the pipe circumferential direction is
Since it becomes narrower as it goes downward, it is difficult to secure the necessary wetted area for exhibiting an effective heat exchange action, and also a dry surface is likely to occur on the outer surface of the pipe, and the water vapor absorption rate of the absorbing liquid Also had a problem that the heat transfer performance was reduced.

Therefore, as an attempt to solve these problems, for example, Japanese Utility Model Laid-Open No. 2-89270 and Japanese Patent Laid-Open No. 2-27070.
A heat transfer tube having a structure as shown in Japanese Patent No. 176378,
Proposed. That is, in these heat transfer tubes, a plurality of crests extending in the longitudinal direction on the outer surface of the tube and troughs formed between the crests are formed with a curved surface shape that is continuous in the tube circumferential direction. The radius of curvature of the valley is set to be larger than the radius of curvature of the peak.

In such a heat transfer tube, when it is used by arranging it in the horizontal direction in the absorber, the absorbing liquid dropped or sprinkled on the outer surface of the tube is more curved than the peaks. By smoothly flowing into the valley with a large radius, the replacement of the absorbing liquid in the valley becomes smooth, and by evenly flowing over the entire circumference of the heat transfer tube, the Marangoni convection (absorption (Tension convection due to surface tension difference due to concentration distribution on the liquid film surface of the surfactant contained in the liquid) and Marangoni convection generated in the troughs interfere with each other, resulting in large disturbance in the longitudinal direction, that is, the pipe axis direction. By causing the action to occur, heat exchange on the outer surface of the pipe can be promoted, and thus the heat exchange efficiency is improved.

However, although the heat transfer tube having such a structure has improved heat transfer performance as compared with the smooth tube, it is difficult to form peaks and valleys with ideal curved surfaces in terms of processing. Moreover, there is a problem that the processing speed is slow.

On the other hand, in order to reduce the manufacturing cost and improve the processing speed by simplifying the manufacturing of the heat transfer tube, it is effective to reduce the number of peaks in the tube circumferential direction. Is a problem, and if the depth of the valley is increased to reduce the decrease in heat transfer performance,
This time, the head loss of the cooling water, which is the cooling fluid, increases due to the decrease in the cross-sectional area of the pipeline, the capacity of the cooling water pump becomes insufficient, and the absorption liquid stagnates in the valley, which delays the progress of the absorption liquid exchange And the heat exchange efficiency decreases,
Furthermore, when a large number of heat transfer tubes are installed in order to suppress a decrease in heat exchange efficiency, problems such as an increase in the required amount of filling of the absorbing liquid may occur.

Further, in the heat transfer tube as described above, the plurality of peaks formed in the longitudinal direction on the outer surface of the heat transfer tube have the same shape, and the valleys have the same depth. The thickness and flow rate of the liquid film of the absorbing liquid flowing down in the pipe circumferential direction in the pipe portion and the expanding action of the absorbing liquid in the pipe axial direction in the valley portion become substantially uniform. Therefore, since the interference between the Marangoni convections generated in the peaks and valleys is almost the same over the entire circumference of the heat transfer tube, there is also a problem that the disturbance action of the absorbing liquid cannot be sufficiently obtained. I had it.

[0008]

The present invention has been made in view of such circumstances, and its object is to have higher heat exchange efficiency and to reduce pressure loss in a pipe. It is an object of the present invention to provide a heat transfer tube for an absorber, which can advantageously reduce the required amount of absorption liquid to be filled.

[0009]

In order to solve such a problem, according to the present invention, an absorbing liquid is dropped or sprayed on the outer surface of the pipe, and the absorbing liquid outside the pipe is cooled by a cooling fluid such as cooling water inside the pipe. In the heat transfer tube for an absorber as described above, a plurality of ridges extending in the pipe axial direction on the outer surface of the pipe are formed with arcuate curved surface shapes in the pipe circumferential direction, and the curvature radius and / or the ridges of the ridges are formed. The gist is that the depths of the valleys formed between the parts are made different.

That is, in the heat transfer tube having the structure according to the present invention, the absorbing liquid such as the LiBr aqueous solution adhered to the outer surface of the tube is effectively cast along the trough portion in the axial direction of the tube. As well as being pushed down, it will be able to flow down in the circumferential direction of the pipe over each mountain portion. At that time, since each crest is formed with an arcuate curved surface shape, the absorbing liquid adhering to the surface of the heat transfer tube should flow smoothly over the crests in the pipe circumferential direction. It is possible to effectively maintain the wet state of the surface of the mountain portion, effectively prevent the deterioration of heat transfer performance due to the occurrence of a so-called dry surface, and when the absorbing liquid is made to flow down over the mountain portion, the inclination Disturbance and convection phenomena can be effectively caused in the absorbing liquid due to changes in the angle, and the portion having a high concentration of the absorbing liquid is well exposed to the outer surface, so that the absorbing action of water vapor is improved.

Further, in such a heat transfer tube, in the peaks and valleys formed on the outer surface of the heat transfer tube, Marangoni convections having different strengths in proportion to the thickness of the liquid film of the absorbing liquid generate peaks and valleys. The Marangoni convection that occurs in the mountain part is caused by the fact that the liquid film thickness of the absorbing liquid in the mountain part is greatly different from the liquid film thickness of the absorbing liquid in the valley part. And the strength of Marangoni convection generated in the valley are very different. And
The Marangoni convections having different intensities interfere with each other to strongly disturb the absorbing liquid.

Further, in the heat transfer tube having the structure according to the present invention, since the radii of curvature of the ridges and / or the depths of the valleys are made different, the ridges and the depths thereof having different radii of curvature are different. The thickness of the liquid film of the absorbing liquid is different between the valleys, and the strength of the Marangoni convection generated there is also different, which causes the interference effect of the Marangoni convection generated in the peaks and valleys as described above. The strength depends on the combination of the crests and troughs that interfere with each other. Therefore, the disturbing action caused by the absorbing liquid becomes very strong, and the heat exchange efficiency is remarkably improved.

According to a preferred embodiment of the heat transfer tube for an absorber according to the present invention, at least the depths of adjacent valleys and / or at least the radii of curvature of adjacent peaks are made different. In particular, by adopting such a configuration, when the absorbing liquid is caused to flow down the outer surface of the heat transfer tube, at least one of repetition of peak-valley-peak or valley-peak-valley is performed. , The strength of the interference effect of Marangoni convection can be made to be different, and thus the strength of the interference effect of Marangoni convection can be advantageously changed, so that the absorption liquid can be more reliably disturbed. It is done.

Further, according to a desirable mode of the heat transfer tube for an absorber according to the present invention, a groove portion extending in the pipe axial direction is provided at the bottom of the valley portion with a cross-sectional shape connecting with a discontinuous surface in the pipe circumferential direction. It will be. Then, due to the formation of such a groove portion, the thickness of the liquid film of the absorbing liquid is discontinuously changed in the pipe circumferential direction at the portion where the groove portion is formed, and accordingly, it is generated in each of the mountain portion and the valley portion. The interference effect of Marangoni convection is magnified. Moreover, since the groove is formed in the valley, the difference between the thickness of the liquid film of the absorbing liquid in the mountain and the thickness of the liquid film of the absorbing liquid in the groove is further increased. , Therefore, as in normal operation,
Not only can Marangoni convection be effectively generated when the prescribed amount of absorbing liquid is dripping, but also when the amount of dripping absorbing liquid is small at the time of start-up, the thickness of the liquid film is advantageously generated. As a result, the disturbing action due to effective Marangoni convection can be exhibited, and by extension, the heat transfer performance can be effectively improved. Since this groove has a shallow depth, it does not hinder the replacement of the absorbing liquid, and the absorbing liquid on the outer surface of the heat transfer tube moves quickly in the circumferential direction. Of.

Further, according to another preferred embodiment of the heat transfer tube for an absorber according to the present invention, the plurality of valleys existing in a predetermined region in the pipe circumferential direction have their depths gradually reduced, and the valleys of the valleys are reduced. The radius of curvature of the peak is gradually increased in accordance with the gradual decrease in depth. And in the heat transfer tube having such a configuration,
When the piping in the absorber is taken into consideration, the flow rate of the absorbing liquid will be advantageously suppressed by considering the directionality of its arrangement.Therefore, let the absorbing liquid contact the outer surface of the heat transfer tube for a long time. In addition, the heat transfer performance can be advantageously improved in combination with the various actions described above. In addition, even when the amount of the absorbing liquid that is dripped is small, such as when starting up, strong Marangoni convection is ensured because a sufficient liquid film thickness of the absorbing liquid is secured in the dripped valley. Will be generated.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION By the way, in such a heat transfer tube for an absorber, a peak portion extending in the tube axial direction on the outer surface thereof is
A plurality of ridges are formed with an arcuate curved surface shape in the pipe circumferential direction, and the radius of curvature of the crests and / or the depth of the troughs formed between the crests are made different. The radius of curvature of the portion or the depth of the valley portion may be different in all in the pipe circumferential direction or may be different in only a part. In order to more effectively exert the disturbing action of the absorbing liquid due to the interference of Marangoni convection, for example, the radius of curvature of the adjacent peaks or the depth of the valleys should be different, for example, the radius of curvature of the peaks. Alternatively, it is desirable to arrange the depths of the valleys so as to gradually increase or decrease, or to arrange two types of peaks having different radii of curvature or two types of valleys having different depths, respectively. Of.

The number of the peaks in the pipe circumferential direction is
Although not particularly limited, it is appropriately selected in consideration of the diameter of the heat transfer tube and the like. That is, if the number of peaks is too small, heat transfer performance will not be sufficiently obtained, and if it is too large, the workability will deteriorate.
The number of peaks is about 25 per pipe, and the radius of curvature of the peaks is 0.5 mm to 5.0 mm in order to realize such a number of peaks.
It is a degree.

Further, the valley formed between the peaks is
Although the shape of the peak portion defines the shape, the depth of such a valley portion is usually 0.1 mm to 1.
It is set to be about 0 mm. This is because when the valley portion is too deep, the cross-sectional area of the heat transfer tube is reduced and the head loss is increased. In the present invention, the depth of the valley means a straight line from the bottom of the valley (the bottom of the groove when a groove is provided at the bottom of the valley) to the peaks located on both sides of the valley. It means the length of the vertical line.

In addition, in the heat transfer tube for an absorber according to the present invention, it is preferable to form a groove at the bottom of the valley in order to further increase the disturbing action. , Are formed so as to be connected at a discontinuous surface in the pipe circumferential direction. In addition, the term "connecting with a discontinuous surface" as used herein means that the outer peripheral curved surfaces of the ridges and valleys and the outer peripheral surface of the groove are in a pipe circumferential direction at an intersection point having no common tangent line in a cross section perpendicular to the pipe axial direction. Is meant to be connected to.

The cross-sectional shape of such a groove is not particularly limited, and various shapes such as an arc shape, a U shape, a V shape, a U shape, or a trapezoidal shape are appropriately adopted. However, the depth is 0.01 to 0.15 m in order to prevent unnecessary retention of the absorbing liquid inside.
It is set to about m.

By the way, various known materials can be used as the material of the heat transfer tube for the absorber as described above, but in order to obtain the heat transfer tube having more excellent heat transfer performance, the heat transfer property is excellent. It is desirable to use a material such as copper or a copper alloy. The diameter of the obtained heat transfer tube is usually
It is about 6.35 mm to 25.4 mm.

The heat transfer tube for an absorber according to the present invention as described above is basically disclosed in Japanese Utility Model Laid-Open No. 2-89270.
JP-A-2-176378, JP-A-7-24522
In accordance with a known technique such as that disclosed in
Will be manufactured. Specifically, the outer peripheral surface shape of the target heat transfer tube, that is, a die having die holes having shapes corresponding to peaks and valleys is used, and the cylindrical pipe to be processed made of copper or copper alloy is cooled. It will be manufactured by drawing hot or hot. At that time, a plug is inserted into the pipe to be processed, if necessary,
The shape of the inner peripheral surface of the pipe is maintained, and as the die, in addition to the one having the integral cylindrical structure, a split die is also used appropriately.

Of course, the production of the heat transfer tube according to the present invention is not limited to the method for producing the heat transfer tube by cold or hot drawing as described above, and for example, a copper pipe having a predetermined composition is used. It goes without saying that there is no problem even if the method is manufactured by hot extrusion, cold extrusion or the like.

The groove formed in each valley in the heat transfer tube according to the present invention has a structure in which the groove and the valley are connected to each other through a discontinuous curved surface. Therefore, in the manufacturing method as described above, By using the ordinary different-diameter pipe processing technology together, it is possible to easily manufacture and the shape stability becomes extremely excellent.

The peaks and valleys formed on the outer surface of the heat transfer tube for an absorber according to the present invention are not limited to those formed linearly in the axial direction of the tube as shown above. There is no problem even if it is formed in a spiral shape in the tube axis direction. However, at that time, if the twist angle with respect to the tube axis of the crest and trough becomes too large, the amount of the absorbing liquid flowing down over the crest decreases, and the heat transfer performance deteriorates. Generally, it is desirable to set it to 15 ° or less.

Further, the heat transfer tube having such spiral peaks and valleys may be formed by using a die having spiral valleys and peaks, or a cylindrical tube as a pipe to be processed and a die may be made to face each other. By performing drawing processing etc. while rotating,
Can be manufactured.

[0027]

EXAMPLES In order to clarify the present invention more specifically, examples of the present invention will be shown below. However, the present invention is not limited by the description of such examples. Needless to say, it is not something to receive. In addition, the present invention, in addition to the following examples, in addition to the above specific description, various modifications based on the knowledge of those skilled in the art, unless departing from the spirit of the present invention,
It should be understood that modifications, improvements and the like can be made.

First, FIGS. 1 and 2 show an absorber heat transfer tube 2 according to an embodiment of the present invention. This heat transfer tube 2 was obtained by subjecting a phosphorus-deoxidized copper tube (outer diameter: 16 mmφ, wall thickness: 0.6 mm) made of C1220 (JIS H3300) material to cold drawing using a die. On the outer surface of the pipe, the ridges 4 linearly extending in the pipe axis direction and the valleys 6 formed between the ridges 4 are formed.
They are provided alternately in the pipe circumferential direction. And 1 / the circumference
In the region of No. 4, the peaks are peaks 4a to 4c having different radii of curvature, while the valleys are valleys 6a to 6d having different depths. Further, a groove portion 8 connected to the peak portion 4 and the valley portion 6 via a discontinuous surface is provided at the bottom of the valley portion 6, respectively.

In this heat transfer tube 2, the mountain portion 4a
The diameter (d in FIG. 2) of the heat transfer tube extending from the center to the mountain portion 4a located on the opposite side in the pipe circumference is 16 mm, and the radius of curvature of the mountain portion 4a: Ra is 1.75 mm, the mountain portion 4b. Has a radius of curvature Rb of 2.05 mm, the radius of curvature of the crest 4c is Rc of 2.25 mm, the depth of the valley 6a: Da is 0.9 mm, and the depth of the valley 6b: Db is 0. 7
mm, the depth of the valley 6c: Dc is 0.5 mm, and the depth of the valley 6d: Dd is 0.3 mm. Also, the groove 8
Has a depth of 0.03 mm.

More specifically, as shown in FIG. 2, the heat transfer tube 2 has a plurality of valleys existing in a predetermined region in the circumferential direction of the tube, the depth of which gradually decreases. The radius of curvature of the crests is gradually increased corresponding to the gradual decrease of the depth of the valleys. That is, the heat transfer tube shown here has a depth of the valley portion: Da over 1/4 of the circumference of the tube.
~ Dd is set to be Da>Db>Dc> Dd, while the radius of curvature of the peak portion formed between the valley portions: Ra ~
Since Rc is set to satisfy Ra <Rb <Rc, the cross-sectional shape is a flat cross-sectional shape that is short in the vertical direction and long in the horizontal direction in FIG. In short, in the heat transfer tube 2 shown in FIG. 2, the valleys 6d located on both left and right sides of the tube have the smallest depth, while the valleys 6a located above and below the tube have the largest depth. , The depth is gradually changed between them. Similarly, even in the radius of curvature of the crests, the radius of curvature of the crests 4a is the smallest and the radius of curvature of the crests 4c is also the largest.

Therefore, in the heat transfer tube 2, since the radius of curvature of the peaks Ra to Rc and the depth of the valleys Da to Dd formed on the outer surface of the tube are different from each other, Due to the combination of the crests 4 and the troughs 6 that interfere with each other, the interference action of the Marangoni convection generated in each of the crests 4 and the troughs 6 is different, and the disturbing action of the absorbing liquid is advantageously strengthened, so that the heat transfer tube surface The absorption liquid is effectively stirred, and the heat exchange of the heat transfer tube 2 can be efficiently performed.

In this heat transfer tube 2, the thickness of the liquid film of the absorbing liquid that is made to flow down from the outer surface of the tube is provided by the grooves 8 as shown in FIG. 3 being provided at the bottom of each valley 6. Can be changed discontinuously, and the interference effect of Marangoni convection that occurs in the peaks and valleys is advantageously strengthened, so that the heat transfer performance can be effectively improved. . Moreover, since the groove portion 8 is provided not in the mountain portion 4 but in the valley portion 6, the difference in the thickness of the liquid film between the mountain portion 4 and the valley portion 6, and hence the strength of Marangoni convection. The difference is further increased, and as a result, the disturbing action of the absorbent is advantageously enhanced.

By the way, the heat transfer tube 2 is generally
As shown in FIG. 4, a plurality of cooling fluids are piped inside the absorber 10 of the absorption chiller in a substantially horizontal posture so as to be arranged in parallel in the vertical direction, and are circulated in the heat transfer tubes 2. The absorbing liquid on the outer surface of the tube is cooled by the barrel cooling water. That is, the absorbing liquid 16 such as a lithium bromide aqueous solution containing a surfactant is dropped or sprinkled on the heat transfer tube 2 from the absorbing droplet lower hole 14 of the tray 12 provided above the heat transfer tube 2. Since the dripped absorption liquid 16 has a high concentration, it smoothly flows down the outer surface of the heat transfer tube 2 while absorbing the water vapor existing in the absorber, and the heat generated at that time is absorbed. It is cooled by transferring heat to the cooling water that is passed inside the heat transfer tube 2. Since the strength of the Marangoni convection that is generated when flowing down the outer surface of the pipe is made different, the disturbing action of the absorbing liquid 16 can be effectively enhanced, so that the heat transfer efficiency is improved. It can be advantageously improved.

More specifically, as shown in FIG. 5, the absorption liquid 16 dripping from the absorption liquid droplet lower hole (not shown) located above the heat transfer pipe 2 is first in the valley 6a. And then over the ridge 4a, and in turn, the valley 6
b, crest 4b, trough 6c, crest 4c, trough 6d, crest 4
c, the valley portion 6c, ... The valley portion 6a and the pipe circumference are sequentially flowed down, and depending on the thickness of the liquid film of the absorbing liquid 16 in each of the peak portions 4a to 4c or the valley portions 6a to 6d. Marangoni convection occurs. Then, at that time, since the depths of the valleys: Da to Dd are gradually changed to be shallow, the thickness of the liquid film of the absorbing liquid is gradually reduced,
Marangoni convection with different strength is generated in the axial direction in each valley. In addition, since the thickness of the liquid film of the absorbing liquid in each of the peaks 4a to 4c is considerably smaller than that in the case of the valley, relatively weak Marangoni convection occurs in the peaks 4a to 4c in the tube axis direction. Then, the Marangoni convections generated in the peaks 4a to 4c and the valleys 6a to 6d interfere with each other, which causes a large disturbing action in the tube axis direction. , Because the strength of interference is different,
The disturbing action of the absorbing liquid is remarkably improved.

Further, as in the present embodiment, in the absorber, the heat transfer tube 2 is arranged such that the deepest valley portion 6a is located in the vertical direction of the tube, while the shallowest valley portion 6d is formed. By arranging so that the depth is gradually changed between them so that they are located on both left and right sides of the pipe, in other words, by arranging so that their cross-sectional shape becomes longer in the horizontal direction, The apparent downflow rate of the absorbing liquid can be suppressed, which greatly improves the heat and substance exchange efficiency.

Furthermore, the heat transfer tube 2 having the structure according to the present invention is
Since the groove 8 is formed in each of the valleys 6a to 6d, the thickness of the liquid film is configured to be larger in each valley, so that the absorption liquid is present in the valleys as in normal operation. Not only strong Marangoni convection occurs during constant amount dropping, but also when the amount of dropping is small, such as at startup, when the absorbing liquid gathers in the groove portion 8 to give a predetermined thickness, The strength of Marangoni convection can be advantageously increased, and the heat transfer performance can be improved. The depth of the groove portion 8 is set to a small value of 0.03 mm, and since the depth is small, there is no problem in exchanging the absorbing liquid, and the absorbing liquid on the outer surface of the heat transfer tube 2 is no problem. Is quickly moved in the pipe circumferential direction. And
In the heat transfer tube 2 according to the present invention, the heat exchange efficiency can be effectively improved only by increasing the absorption liquid corresponding to the groove portion 8 as compared with the conventionally used heat transfer tube. In comparison with a heat transfer tube having an improved heat exchange efficiency, the heat exchange efficiency can be improved and the pressure loss inside the tube can be reduced even if the required amount of absorbing liquid is small.

Further, in the heat transfer tube 2, since the inner surface of the tube is formed into a curved surface corresponding to the outer surface of the tube, adhesion of scale in the cooling fluid to the inner surface of the tube can be effectively prevented, and the inside of the tube can be prevented. It made cleaning easier.

Further, FIG. 6 shows another embodiment of the heat transfer tube for the absorber according to the present invention. That is, in the heat transfer tube 18 shown here, the mountain portion 4 is composed of mountain portions 4d and 4e having different radii of curvature: Rd (= 2.7 mm) and Re (= 3.3 mm). 4d and Yamabe 4
e are arranged alternately. The diameter d of the heat transfer tube 18 is 16 mm, and the depth of the valley 6 is 0.6 m.
m.

When the absorbing liquid 16 is allowed to flow down on the outer surface of the heat transfer tube 18, the thickness of the absorbing liquid film at the ridge 4d is smaller than the thickness of the absorbing liquid film at the ridge 4e. In addition, the strength of the generated Marangoni convection differs, and the difference in the radius of curvature of the ridges changes the flow rate of the absorbing liquid. Moreover, these 4d and 4e are one in the pipe circumferential direction. It is arranged every other time. Therefore,
The interference effect between the Marangoni convection generated in the mountain portion 4d or the mountain portion 4e and the Marangoni convection generated in the valley portion 6 is advantageously made different, so that the disturbing action of the absorbing liquid is further extended to the transfer of the heat transfer tube 18. The thermal performance can be effectively improved.

Further, FIG. 7 shows a further different embodiment of the heat transfer tube for the absorber according to the present invention. That is, in the heat transfer tube 20 shown here, the valley portions 6 have different depths: D.
It is composed of valleys 6e and 6f having e (= 0.6 mm) and Df (= 0.3 mm), and these valleys 6e and 6f are
They are arranged alternately. The diameter of the heat transfer tube 20: d
Is 16 mm, and the radius of curvature of the mountain portion 4 is 2.5 mm.
It is.

Even in such a heat transfer tube 20, when the absorbing liquid 16 is caused to flow down on the outer surface thereof,
The thicknesses of the liquid films of the absorbing liquid in the valleys 6e and 6f are different, and the strength of the generated Marangoni convection is changed. Moreover, these valleys 6e and 6f are alternate in the pipe circumferential direction. It is located in. Therefore, there is a difference in the intensity of the interference between the Marangoni convection generated in the mountain portion 4 and the Marangoni convection generated in the valley portion 6e or the mountain portion 6f, which causes the disturbance action of the absorbing liquid, and by extension, the heat transfer tube 20. The heat transfer performance can be effectively improved.

[0042]

As is apparent from the above description, in the heat transfer tube for an absorber according to the present invention, the interference action between the Marangoni convection generated in the mountain portion and the Marangoni convection generated in the valley portion causes interference. It is made different by the combination of the crests and troughs that are in contact with each other.Therefore, it is possible to exert a strong disturbing action of the absorbing liquid, which was not possible with the conventional heat transfer tubes for absorbers, and heat on the outer surface of the tubes can be exerted. The exchange efficiency can be effectively improved. And, such an improvement in heat exchange efficiency can be achieved by making the radius of curvature of at least adjacent peaks or the depth of at least adjacent valleys different.
It can be further enhanced.

Further, in the heat transfer tube for an absorber according to the present invention, the heat exchange efficiency is advantageously improved, so that it is not necessary to form many peaks or deep valleys. Therefore, it can be easily manufactured by various conventionally known methods, for example, cold drawing or different diameter pipe processing, and the head loss in the pipe can be effectively reduced.

Further, in order to further enhance the disturbing action of the absorbing liquid flowing down to the outer surface of the tube, when the bottom of the valley is provided with a groove having a cross-sectional shape connected by a discontinuous surface, the discontinuity is formed. The presence of the surface enhances the disturbing action of the absorbing liquid, and even when the amount of the absorbing liquid is small, the thickness of the liquid film is advantageously ensured, and Marangoni convection can be efficiently generated. The required amount of absorption liquid can be effectively reduced.

Further, in the heat transfer tube, a plurality of troughs existing in a predetermined region in the circumferential direction of the tube are gradually reduced in depth, and in correspondence with the gradual decrease in depth of the troughs, the crests are formed. When the radius of curvature of is gradually increased, the apparent downflow speed of the absorbing liquid dropped into the heat transfer tube can be suppressed by considering the arrangement direction, and the efficiency of heat and substance exchange can be improved. It can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a perspective explanatory view showing an example of a heat transfer tube for an absorber according to the present invention.

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

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

FIG. 4 is an explanatory diagram showing an example of a state in which a plurality of heat transfer tubes shown in FIG. 1 are arranged in an absorber.

5 is a cross-sectional explanatory view of a heat transfer tube in the absorber shown in FIG.

FIG. 6 is a cross-sectional explanatory view similar to FIG. 2, showing a different example of the absorber heat transfer tube according to the present invention.

FIG. 7 is a cross-sectional explanatory view similar to FIG. 2, showing a further different example of the heat transfer tube for an absorber according to the present invention.

[Explanation of symbols]

 2, 18 and 20 Heat transfer tube 4, 4a to 4e Mountain part 6, 6a to 6f Valley part 8 Groove part 10 Absorber 12 Tray 14 Absorbing liquid droplet lower hole 16 Absorbing liquid

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yoshihiro Nishimoto Sumitomo Light Metal Industry Co., Ltd. 5-11-3 Shimbashi, Minato-ku, Tokyo

Claims (5)

[Claims] 1. A heat transfer tube for an absorber in which an absorbing liquid is dropped or sprinkled onto the outer surface of a pipe to cool the absorbing liquid outside the pipe by a cooling fluid inside the pipe, which extends in the axial direction of the pipe on the outer surface of the pipe. A plurality of ridges are formed with an arcuate curved surface shape in the pipe circumferential direction, and the radius of curvature of the ridges and / or the depth of valleys formed between the ridges are made different. Heat transfer tube for absorber. 2. The heat transfer tube for an absorber according to claim 1, wherein the depths of at least adjacent valleys are different from each other. 3. The heat transfer tube for an absorber according to claim 1, wherein at least adjacent peaks have different radii of curvature. 4. The groove according to claim 1, wherein a groove extending in the pipe axis direction is provided at a bottom of the valley with a cross-sectional shape connected by a discontinuous surface in the pipe circumferential direction. Heat transfer tubes for absorbers. 5. A plurality of valleys existing in a predetermined region in the pipe circumferential direction have their depths gradually reduced, and the radius of curvature of the peaks corresponds to the depths of the valleys. The heat transfer tube for an absorber according to claim 1, wherein the heat transfer tube is gradually increased.