JP3587599B2 - Heat transfer tube for absorber - Google Patents

Description

[0001]
【Technical field】
The present invention relates to a heat transfer tube for an absorber piped in an absorber such as an absorption refrigerator or an absorption heat pump, and particularly has excellent heat exchange efficiency while keeping the pressure loss and the required amount of the absorption liquid in the tube low. The present invention relates to a heat transfer tube for an absorber.
[0002]
[Background Art]
Generally, 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 smooth inner and outer surfaces is employed. However, since the heat transfer performance of such a smooth tube is low, it has been difficult to meet the demand for higher performance and smaller size of the absorber. Further, in such a smooth tube, the width of the absorbing liquid which is caused to flow down the outer peripheral surface of the tube in the circumferential direction of the tube is reduced due to surface tension, so that the effective heat exchange effect is exhibited. In addition, it is difficult to secure a required wet area, and there is also a problem that a thirst surface is easily generated on the outer surface of the tube, and the water vapor absorption rate of the absorbing solution, and thus the heat transfer performance, are reduced.
[0003]
In order to solve these problems, for example, a heat transfer tube having a configuration as disclosed in Japanese Utility Model Laid-Open No. 2-89270, Japanese Patent Laid-Open No. 2-176378, and the like has been proposed. That is, in the heat transfer tubes, a plurality of ridges extending in the longitudinal direction on the outer surface of the tubes and valleys formed between the ridges are formed with a curved surface shape continuous in the tube circumferential direction, and The radius of curvature of the valley is larger than the radius of curvature of the peak.
[0004]
In such a heat transfer tube, when used in a horizontal arrangement in the absorber, the absorbing liquid dropped or sprayed on the outer surface of the tube has a larger radius of curvature than the peak portion. By flowing smoothly to the valley, the replacement of the absorbing liquid at the valley becomes smooth, and by flowing uniformly over the entire circumference of the heat transfer tube, the Marangoni convection generated at the hill (including in the absorbing liquid) Convection caused by the surface tension difference due to the concentration distribution of the surfactant liquid film surface) and the Marangoni convection generated in the valley interfere with each other, and a large disturbance action occurs in the longitudinal direction, that is, in the tube axis direction. By doing so, heat exchange on the outer surface of the tube can be promoted, thereby improving the heat exchange efficiency.
[0005]
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 the peaks and valleys with ideal curved surfaces, and furthermore, the processing is difficult. There was a problem that the speed was slow.
[0006]
On the other hand, it is effective to reduce the number of peaks in the circumferential direction of the tube in order to reduce the manufacturing cost and improve the processing speed by simplifying the manufacture of the heat transfer tube. If the depth of the valley is increased to reduce the decrease in heat transfer performance, the head loss of the cooling water, which is the cooling fluid, will increase due to the decrease in the pipe cross-sectional area. Insufficient capacity of the pump or the stagnation of the absorbing liquid in the valley delays the progress of the absorbing liquid exchange, thereby reducing the heat exchange efficiency or further suppressing the heat exchange efficiency from decreasing. In addition, when a large number of heat transfer tubes are installed, a problem such as an increase in the required amount of filling of the absorbing liquid occurs.
[0007]
In the heat transfer tube as described above, the shape of the plurality of ridges formed in the longitudinal direction on the outer surface thereof is the same, and the depth of the valleys is the same. The thickness of the liquid film of the absorbing liquid flowing down in the circumferential direction, the flowing speed, and the effect of expanding the absorbing liquid in the tube axis direction at the valleys become substantially uniform. Therefore, since the interference between the Marangoni convections generated at 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 effect of the absorbing liquid cannot be sufficiently obtained. I had it.
[0008]
[Solution]
Here, the present invention has been made in view of the above circumstances, and has as its object to have higher heat exchange efficiency, reduce pressure loss in the pipe, and fill the absorbing liquid. An object of the present invention is to provide a heat transfer tube for an absorber that can advantageously reduce a required amount.
[0009]
[Solution]
In order to solve such a problem, the present invention provides an absorbent in which the 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 in the pipe. In the heat transfer tube, a plurality of ridges extending in the tube axis direction on the outer surface of the tube are formed with a curved surface shape having an arc shape in the circumferential direction of the tube, and a radius of curvature of the ridges and / or a gap between the ridges are formed. The main point is that the depths of the valleys are different.
[0010]
That is, in such a heat transfer tube having the structure according to the present invention, the absorbing liquid such as the LiBr aqueous solution attached to the outer surface of the tube is effectively cast along the valley portion toward the tube axis direction. Therefore, it can be made to flow down in the circumferential direction of the pipe beyond each peak. At this time, since each peak is formed in an arcuate curved surface shape, the absorbent adhering to the surface of the heat transfer tube smoothly flows down over the peaks in the circumferential direction of the tube. It is possible to advantageously maintain the wet state of the surface of the peak portion, effectively prevent the deterioration of the heat transfer performance due to the generation of a so-called thirst surface, and at the same time, when the absorbent is allowed to flow down over the peak portion, Due to a change in the angle or the like, a disturbance and a convection phenomenon can be effectively caused in the absorbing solution, and a portion having a high concentration of the absorbing solution is well exposed to the outer surface, so that the action of absorbing water vapor is improved.
[0011]
Further, in such a heat transfer tube, Marangoni convection having different strength is formed along the peaks and valleys in the peaks and valleys formed on the outer surface thereof in proportion to the thickness of the liquid film of the absorbing liquid. Although the thickness of the liquid film of the absorbing liquid at the peak and the thickness of the liquid film of the absorbing liquid at the valley are significantly different, the strength of the Marangoni convection generated at the peak is The strength of Marangoni convection generated in the valley differs greatly. Then, the Marangoni convections having different intensities interfere with each other, so that the absorbing liquid is strongly disturbed.
[0012]
Further, in the heat transfer tube having the structure according to the present invention, since the radius of curvature of the peaks and / or the depth of the valleys are made different, between the peaks having different radii of curvature or the valleys having different depths. In the above, the thickness of the liquid film of the absorbing liquid is different, and the strength of the Marangoni convection generated there is also different, and the strength of the interference action of the Marangoni convection generated in the peaks and valleys as described above is reduced. It depends on the combination of peaks and valleys that interfere with each other. Therefore, the disturbance effect caused by the absorbing liquid becomes very strong, and the heat exchange efficiency is remarkably improved.
[0013]
By the way, according to the preferred embodiment of the heat transfer tube for an absorber according to the present invention, at least the depth of adjacent valleys and / or the radius of curvature of at least adjacent ridges 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 the repetition of the peak-valley-peak or the valley-peak-valley is performed. However, the strength of the interference effect of Marangoni convection is always made different, so that the strength of the interference action of Marangoni convection can be advantageously changed, and the disturbance of the absorbing solution can be performed more reliably. It is done.
[0014]
Further, according to a preferred aspect of the heat transfer tube for an absorber according to the present invention, a groove portion extending in the tube axis direction is provided at the bottom of the valley portion with a cross-sectional shape continuous with a discontinuous surface in the tube circumferential direction. . Then, due to the formation of such a groove, the thickness of the liquid film of the absorbing liquid is changed discontinuously in the circumferential direction of the tube at the formation portion of the groove, and thus occurs at each of the peak and the valley. The interference effect of Marangoni convection is greatly exaggerated. In addition, since such a groove is formed in the valley, the difference between the thickness of the liquid film of the absorbing liquid in the peak and the thickness of the liquid film of the absorbing liquid in the groove is further increased. Therefore, as in normal operation, when a predetermined amount of absorbing liquid is dripped, not only Marangoni convection is effectively generated, but also when the amount of dripping of the absorbing liquid is small at the time of startup or the like. Advantageously, the thickness of the liquid film is generated, and a disturbance effect due to effective Marangoni convection can be exerted, so that the heat transfer performance can be effectively improved. Since the depth of the groove is shallow, the replacement of the absorbing solution does not hinder the replacement of the absorbing solution at all, and the moving of the absorbing solution on the outer surface of the heat transfer tube in the circumferential direction of the tube is quickly performed. It is.
[0015]
Furthermore, according to another preferred embodiment of the heat transfer tube for an absorber according to the present invention, the plurality of valleys present in a predetermined region in the circumferential direction of the tube have their depths gradually reduced, and the depth of the valleys is reduced. In response to the gradual decrease, the radius of curvature of the peak is gradually increased. In the heat transfer tube having such a configuration, the flow rate of the absorbing liquid is advantageously suppressed by considering the directionality of the arrangement when piping in the absorber. The liquid is brought into contact with the outer surface of the heat transfer tube for a long time, and the heat transfer performance can be advantageously improved in combination with the various actions as described above. In addition, even when the amount of the absorbing liquid dropped is small, such as at the time of startup, since a sufficient liquid film thickness of the absorbing liquid is secured in the dropped valley, strong Marangoni convection occurs. Will be generated.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
By the way, in such a heat exchanger tube for an absorber, a plurality of ridges extending in the tube axial direction on the outer surface thereof are formed with a curved surface shape having an arc shape in the circumferential direction of the tube, and a radius of curvature and / or The depths of the valleys formed between the peaks are made different. Even if the radii of curvature of the ridges or the depths of the valleys are made different in the entire circumferential direction of the pipe, one difference is obtained. Only the parts may be different. Then, in order to more effectively exert the disrupting action of the absorbing solution due to the interference of Marangoni convection, the curvature radius of at least the adjacent peaks or the depth of the valleys are made different, for example, the curvature radius of the peaks. Alternatively, it is desirable to arrange the valley depth so as to gradually increase or decrease, or to arrange two types of ridges having different radii of curvature or two types of valleys having different depths, respectively. It is.
[0017]
In addition, the number of the peaks in the pipe circumferential direction is not particularly limited, but 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, sufficient heat transfer performance cannot be obtained, and if it is too large, workability deteriorates. Therefore, the number of peaks is generally about 3 to 25 per pipe circumference. Is realized, the radius of curvature of the peak is set to about 0.5 mm to 5.0 mm.
[0018]
Further, the shape of the trough formed between the peaks is determined by the shape of the peak, and the depth of such a trough is usually 0.1 mm to 1.0 mm. To be on the order. This is because if the valley is too deep, the cross-sectional area of the heat transfer tube decreases, and the head loss increases. In the present invention, the depth of the valley is defined as a straight line that is in contact with the ridges adjacent to both sides of the valley from the bottom of the valley (or the bottom of the groove when a groove is provided at the bottom of the valley). Means the length of the vertical line.
[0019]
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 disturbance action. It is formed so as to be connected in a discontinuous plane in the direction. In addition, the term “joining at a discontinuous surface” as used herein means that the outer peripheral surface of the crest and the valley and the outer peripheral surface of the groove at the intersection perpendicular to the tube axis direction at the intersection where there is no common tangent line. Is connected to.
[0020]
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 may be appropriately adopted. The depth is set to about 0.01 to 0.15 mm in order to prevent unnecessary retention of the absorbing liquid inside.
[0021]
By the way, as a material constituting such a heat transfer tube for an absorber, various known materials can be used, but in order to obtain a heat transfer tube having more excellent heat transfer performance, a material having excellent heat transfer properties, for example, It is desirable to use copper or copper alloy. The diameter of the obtained heat transfer tube is usually about 6.35 mm to 25.4 mm.
[0022]
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, Japanese Patent Laid-Open No. 2-176378, Japanese Patent Laid-Open No. 7-24522 and the like. It will be manufactured according to a known method. Specifically, using a die having a die hole having a shape corresponding to the outer peripheral surface shape of the target heat transfer tube, that is, a shape corresponding to the peaks and valleys, a cylindrical processing tube made of copper or a copper alloy is cooled. It is manufactured by drawing or the like during hot or hot. Also, at this time, a plug is inserted into the pipe to be processed as necessary, so that the shape of the inner peripheral surface of the pipe is retained. Dice are also used as appropriate.
[0023]
Of course, the manufacture of the heat transfer tube according to the present invention is not limited to the method of manufacturing the heat transfer tube by cold or hot drawing as described above. It goes without saying that there is no problem with a method manufactured by extrusion, cold extrusion, or the like.
[0024]
Further, since the groove formed in each valley in the heat transfer tube according to the present invention is configured to be connected to the ridge and the valley via a discontinuous curved surface, the manufacturing method as described above uses a usual method. The combined use of the different-diameter pipe processing technology enables easy production and extremely excellent shape stability.
[0025]
Note that the peaks and valleys formed on the outer surface of the absorber heat transfer tube according to the present invention are not limited to those formed linearly in the tube axis direction as described above, and are not limited at all. Even if it is formed spirally in the axial direction, there is no problem. However, at that time, if the twist angle of the peak and the valley with respect to the pipe axis becomes too large, the amount of the absorbing liquid flowing down over the peak is reduced, and the heat transfer performance is reduced. Generally, it is desirable to set the angle to 15 ° or less.
[0026]
Further, such a heat transfer tube having a spiral ridge and a valley, by using a die having a spiral valley and a ridge, or while relatively rotating the cylindrical tube and the die as a pipe to be processed. It can be manufactured by performing a drawing process or the like.
[0027]
【Example】
Hereinafter, in order to clarify the present invention more specifically, embodiments of the present invention will be described. However, the present invention is not limited by the description of such embodiments. That goes without saying. In addition, in addition to the following examples, the present invention, in addition to the above-described specific description, various changes, modifications, and modifications based on the knowledge of those skilled in the art without departing from the spirit of the present invention. It should be understood that improvements and the like can be made.
[0028]
First, FIGS. 1 and 2 show a heat transfer tube 2 for an absorber according to an embodiment of the present invention. The heat transfer tube 2 is obtained by subjecting a phosphorus-deoxidized copper tube (outer diameter: 16 mmφ, wall thickness: 0.6 mm) made of C1220 (JIS H3300) to cold drawing using a die. On the outer surface of the pipe, ridges 4 extending linearly in the pipe axis direction and valleys 6 formed between the ridges 4 are alternately provided in the pipe circumferential direction. And in the 1/4 region of the pipe circumference, the peaks are respectively composed of peaks 4a to 4c having different radii of curvature, while the valleys are respectively composed of valleys 6a to 6d having different depths. In the bottom of the valley 6, a groove 8 connected to the ridge 4 and the valley 6 via a discontinuous surface is provided.
[0029]
In this heat transfer tube 2, the diameter (d in FIG. 2) of the heat transfer tube extending from the peak 4 a to the peak 4 a located on the opposite side of the pipe periphery from the center through the center is 16 mm, and the diameter of the peak 4 a Radius of curvature: Ra is 1.75 mm, radius of curvature of peak 4b: Rb is 2.05 mm, radius of curvature of peak 4c: Rc is 2.25 mm, and depth of valley 6a: Da is 0.9 mm. 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. The groove 8 has a depth of 0.03 mm.
[0030]
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, and the valleys have a gradually decreasing depth. The radii of curvature of the peaks are gradually increased in accordance with the gradual decrease of the depth of the ridges. That is, in the heat transfer tube shown here, the depths of the valleys: Da to Dd satisfy Da>Db>Dc> Dd over one-fourth of the tube circumference, while the valleys are formed. Since the radii of curvature of the peaks formed between the parts are set to satisfy Ra <Rb <Rc, the cross-sectional shape thereof is shorter in the vertical direction in FIG. It has a long, flat cross-sectional shape. In short, in the heat transfer tube 2 shown in FIG. 2, the depth of the valleys 6d located on the left and right sides thereof is made the smallest, while the depth of the valleys 6a located above and below the tube is made the deepest. Between them, the depth is gradually changing. Similarly, the radii of curvature of the peaks are similarly gradually changed so that the radius of curvature of the peaks 4a is the smallest and the radius of curvature of the peaks 4c is the largest.
[0031]
Therefore, in such a heat transfer tube 2, the radii of curvature of the peaks: Ra to Rc and the depths of the valleys: Da to Dd formed on the outer surface of the tube are different from each other, so they interfere with each other. Depending on the combination of the peaks 4 and the valleys 6, the interference action of Marangoni convection generated in each of the peaks 4 and the valleys 6 is different, and the disturbance action of the absorbent is advantageously strengthened, and the absorption of the absorbent on the surface of the heat transfer tube is improved. The stirring is effectively performed, and the heat exchange of the heat transfer tube 2 can be efficiently performed.
[0032]
Further, in this heat transfer tube 2, since a groove 8 as shown in FIG. 3 is provided at each of the bottoms of the valleys 6, the thickness of the liquid film of the absorbing liquid flowing down the outer surface of the tube is not sufficient. It can be changed continuously, and the interference effect of Marangoni convection generated at the peaks and valleys is advantageously enhanced, so that the heat transfer performance can be effectively improved. In addition, since the groove 8 is provided not in the peak 4 but in the valley 6, the difference in the thickness of the liquid film between the peak 4 and the valley 6 and, consequently, the strength of Marangoni convection. Is further increased, so that the disturbing effect of the absorbing solution is advantageously enhanced.
[0033]
By the way, as shown in FIG. 4, such heat transfer tubes 2 are generally piped inside the absorber 10 of the absorption refrigerator in such a manner that a plurality of the heat transfer tubes 2 are arranged in a substantially horizontal posture in a vertical direction. The absorbing liquid on the outer surface of the heat transfer tube 2 is cooled by the cooling water as the cooling fluid flowing through the heat transfer tube 2. That is, the absorbing liquid 16 such as an aqueous solution of lithium bromide containing a surfactant is dropped or sprayed on the heat transfer tube 2 from the absorbing droplet preparation hole 14 of the tray 12 provided thereabove. Since the dropped absorbent 16 has a high concentration, it absorbs water vapor existing in the absorber and flows down the outer surface of the heat transfer tube 2 smoothly. It is cooled by transferring heat to the cooling water passed inside the heat transfer tube 2. And since the strength of the Marangoni convection generated when flowing down the outer surface of the tube is made different, the disturbing action of the absorbing liquid 16 can be effectively increased, and the heat transfer efficiency can be improved. It can be advantageously improved.
[0034]
More specifically, as shown in FIG. 5, the absorbing liquid 16 dropped from the absorbing liquid drop hole (not shown) located above the heat transfer tube 2 first contacts the heat transfer tube at the valley 6a. The valley 6b, the valley 4b, the valley 6c, the valley 4c, the valley 6d, the valley 4c, the valley 6c,... Then, the Marangoni convection corresponding to the thickness of the liquid film of the absorbing liquid 16 occurs in each of the peaks 4a to 4c or the valleys 6a to 6d. At this time, since the depth of each valley portion: Da to Dd is gradually changed to be shallower, the thickness of the liquid film of the absorbing liquid is gradually reduced. Marangoni convection of different strength occurs in the direction. Further, since the thickness of the liquid film of the absorbing liquid in each of the peaks 4a to 4c is considerably thinner than that in the case of the valleys, a relatively weak Marangoni convection occurs in the peaks 4a to 4c in the tube axis direction. The interference of the Marangoni convections generated at the peaks 4a to 4c and the valleys 6a to 6d causes a large disturbance action in the tube axis direction. In addition, the disturbing action of the absorbing solution is remarkably improved because of the difference in the interference strength.
[0035]
Further, as in the present embodiment, in the absorber, the heat transfer tube 2 is arranged such that the deepest valley 6a is located in the vertical direction of the tube, while the shallow valley 6d is positioned in the tube in the vertical direction. By arranging them so that the depth is gradually changed between them, in other words, by arranging them so that their cross-sectional shape becomes longer in the horizontal direction, the absorption liquid The apparent flow velocity can be suppressed, thereby greatly improving the heat and substance exchange efficiency.
[0036]
Further, since the heat transfer tube 2 having the configuration according to the present invention is configured such that the groove 8 is formed in the valleys 6a to 6d, the thickness of the liquid film is configured to be larger in each valley. In addition, not only strong Marangoni convection occurs when a predetermined amount of the absorbing liquid is dripped as in normal operation, but also when the amount of dripping is small, such as during startup, the absorbing liquid is in the groove 8. From the point of gathering and providing a predetermined thickness, the strength of Marangoni convection can be advantageously increased, and thus the heat transfer performance can be improved. The depth of the groove 8 is set to be as small as 0.03 mm. Since the depth is small, there is no problem in replacing the absorbing liquid, and the absorbing liquid on the outer surface of the heat transfer tube 2 is not affected. Is quickly moved in the pipe circumferential direction. Then, 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 heat transfer tube conventionally used. Further, even when compared with a heat transfer tube having an increased heat exchange efficiency, the heat exchange efficiency can be improved even if the required amount of the absorbing liquid is small, and the pressure loss in the tube can be reduced. .
[0037]
Further, in the heat transfer tube 2, since the inner surface of the tube is formed to have a curved surface corresponding to the outer surface of the tube, it is possible to effectively prevent scale in the cooling fluid from adhering to the inner surface of the tube and to easily clean the inside of the tube. It was a break.
[0038]
FIG. 6 shows another embodiment of the heat transfer tube for an absorber according to the present invention. That is, in the heat transfer tube 18 shown here, the peaks 4 are composed of peaks 4d and 4e having different radii of curvature: Rd (= 2.7 mm) and Re (= 3.3 mm). 4d and ridges 4e 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 mm.
[0039]
When the absorbing liquid 16 is caused to flow down the outer surface of the heat transfer tube 18, the thickness of the liquid film of the absorbing liquid at the peak 4d is smaller than the thickness of the liquid film at the peak 4e. A difference occurs in the strength of the generated Marangoni convection, and the difference in the radius of curvature of the peak changes the flow rate of the absorbing liquid. In addition, these 4d and 4e are arranged alternately in the pipe circumferential direction. Have been. Therefore, the interference between the Marangoni convection generated at the peak 4d or the peak 4e and the Marangoni convection generated at the valley 6 is advantageously differentiated, so that the disturbing action of the absorbing liquid and the heat transfer pipe 18 are reduced. The heat transfer performance can be effectively improved.
[0040]
Further, FIG. 7 shows still another embodiment of the heat transfer tube for an absorber according to the present invention. That is, in the heat transfer tube 20 shown here, the valleys 6 are composed of valleys 6e and 6f having different depths: De (= 0.6 mm) and Df (= 0.3 mm). And the valleys 6f are arranged alternately. The diameter d of the heat transfer tube 20 is 16 mm, and the radius of curvature of the peak 4 is 2.5 mm.
[0041]
Even in such a heat transfer tube 20, when the absorbing liquid 16 is caused to flow down to the outer surface thereof, the thickness of the liquid film of the absorbing liquid at the valleys 6e and 6f is different, and the generated Marangoni. The strength of the convection is changed, and the valleys 6e and 6f are arranged alternately in the pipe circumferential direction. Therefore, there is a difference in the intensity of the interference between the Marangoni convection generated at the peak 4 and the Marangoni convection generated at the valley 6e or the peak 6f, thereby disturbing the absorption liquid and, consequently, the heat transfer tube 20. The heat transfer performance can be effectively improved.
[0042]
【The invention's effect】
As is clear from the above description, in the heat transfer tube for an absorber according to the present invention, the interference between the Marangoni convection generated at the peak and the Marangoni convection generated at the valley causes the interference with the crest. Depending on the combination of the valleys, it is made different, so that a strong absorber disturbing action that could not be obtained with the conventional heat transfer tube for the absorber can be exhibited, and the heat exchange efficiency on the outer surface of the tube is effective Can be improved. Such improvement in heat exchange efficiency can be further enhanced by making at least the radius of curvature of adjacent peaks or the depth of at least adjacent valleys different.
[0043]
And, in the heat transfer tube for an absorber according to the present invention, since the heat exchange efficiency is advantageously improved, it is not necessary to form many ridges or to form valleys deeply. It can be easily manufactured by various conventionally known methods, for example, cold drawing and processing of different diameter pipes, and the head loss in the pipes can be effectively reduced.
[0044]
In addition, in order to further enhance the disturbing action of the absorbing liquid flowing down to the outer surface of the tube, when a groove having a cross-sectional shape connected by a discontinuous surface is provided at the bottom of the valley, the presence of the discontinuous surface is present. Thereby, the disturbing action of the absorbing solution is enhanced, and even when the amount of the absorbing solution is small, the thickness of the liquid film is advantageously secured, so that Marangoni convection can be efficiently generated. The required amount can be effectively reduced.
[0045]
Further, in the heat transfer tube, a plurality of valleys existing in a predetermined region in the circumferential direction of the tube are gradually reduced in depth, and the radii of curvature of the ridges are corresponding to the gradual decrease in the depth of the valleys. Considering the arrangement direction when the temperature is gradually increased, the apparent flow speed of the absorbing liquid dropped on the heat transfer tube will be suppressed, and the heat and substance exchange efficiency will be greatly improved. You can be sullen.
[Brief description of the drawings]
FIG. 1 is an explanatory perspective view showing an example of a heat transfer tube for an absorber according to the present invention.
FIG. 2 is an explanatory cross-sectional view of the heat transfer tube shown in FIG.
FIG. 3 is an enlarged explanatory view of a main part of a cross section of the heat transfer tube shown in FIG. 2;
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.
FIG. 5 is an explanatory sectional 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 heat transfer tube for an absorber according to the present invention.
FIG. 7 is a cross-sectional explanatory view similar to FIG. 2, showing still another example of the heat transfer tube for an absorber according to the present invention.
[Explanation of symbols]
2, 18, 20 Heat transfer tubes 4, 4a-4e Yamabe
6, 6a to 6f Valley 8 Slot
10 absorber 12 tray
14 Absorbing droplet pilot hole 16 Absorbing liquid

Claims (5)

Absorbent liquid is dropped or sprayed on the outer surface of the tube, and the cooling fluid in the tube is used to cool the absorbent outside the tube to a heat transfer tube for an absorber,
A plurality of ridges extending in the pipe axis direction on the outer pipe surface are formed with a curved surface shape having an arc shape in the circumferential direction of the pipe, and the radius of curvature of the ridges and / or A heat transfer tube for an absorber characterized by having different depths. The heat exchanger tube for an absorber according to claim 1, wherein at least the depths of adjacent valleys are different. The heat transfer tube for an absorber according to claim 1 or 2, wherein at least adjacent ridges have different radii of curvature. The heat transfer tube for an absorber according to any one of claims 1 to 3, wherein a groove portion extending in the tube axis direction is provided at a bottom of the valley portion, with a cross-sectional shape connected by a discontinuous surface in the tube circumferential direction. . The plurality of valleys existing in the predetermined region in the circumferential direction of the pipe are gradually decreasing in depth, and the radius of curvature of the ridge is gradually increased in accordance with the gradual decrease in the depth of the valley. The heat transfer tube for an absorber according to any one of claims 1 to 4.

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