JP2008267625A - Heat transfer tube for falling film refrigerator and its manufacturing method - Google Patents

Abstract

[PROBLEMS] To provide a heat transfer tube for a light single falling liquid film refrigerator that advantageously reduces pressure loss inside the tube without reducing the effect of improving heat transfer performance by grooves and fins formed on the outer surface of the tube. To provide.
A fin 12 formed on the outer surface of a pipe has a fin height (H): 0.15 to 0.35 mm, a fin pitch (P ₁ ): 0.9 to 2.4 mm, and a minimum width of the fin top ( W): 0.3 to 0.7 mm, tube bottom wall thickness (t): 0.40 to 0.55 mm, curvature radius of fin base (R): 0.05 to 0.3 mm, and groove 14 Groove depth (D): 0.1-0.3 mm, groove pitch (P ₂ ): 0.5-1.0 mm, difference between fin height and groove depth (d ₁ ) and fin height (H ) (D _{1 /} H): 0.05 to 0.25 in the axial direction of the tube, and the depth (d ₂ ) of the recess 16 formed on the inner surface of the tube is 0.03 mm or less. Then, the heat transfer tube 10 was formed.
[Selection] Figure 1

Description

  The present invention relates to a heat transfer tube suitably used for an absorber and an evaporator of an absorption chiller, an evaporator of an adsorption chiller, and the like, and in particular, the thickness of the tube is reduced in order to reduce the unit weight of the tube. The present invention relates to an improvement of a heat transfer tube for a falling liquid film type refrigerator.

  Conventionally, absorbers and evaporators of absorption refrigerators, evaporators of adsorption refrigerators, and the like have been provided with a plurality of heat transfer tubes and / or a plurality of rows such that the tube axis is in the horizontal direction. A grid or staggered arrangement is used, and an aqueous lithium bromide solution as a working medium is dropped from the upper dropping tray onto such a heat transfer tube so as to flow down in a film form on the horizontal tube. The so-called falling liquid film type has been widely adopted.

  As a heat transfer tube used in such a falling film type absorber, a smooth tube having a smooth inner peripheral surface can be manufactured at low cost, and the inner peripheral surface of the tube is also smooth. Therefore, it has been widely used because it has the advantage of low pressure loss. However, in such a smooth tube, since the outer peripheral surface of the tube is smooth, the liquid film of the lithium bromide aqueous solution easily flows down in the tube circumferential direction (gravity direction) and hardly spreads in the tube axis direction (horizontal direction). Therefore, the problem that sufficient heat transfer performance cannot be obtained is inherent.

  Therefore, for the purpose of improving the heat transfer performance, various heat transfer tubes having various heat transfer promoting functions on the outer surface of the heat transfer tube have been developed and adopted. For example, in Japanese Patent Application Laid-Open No. 1-134180 (Patent Document 1) and Japanese Patent Application Laid-Open No. 62-206356 (Patent Document 2), a plurality of grooves extending in the longitudinal direction are formed on the outer peripheral surface of the pipe, and finely spaced between the grooves. Each heat transfer tube formed with a large number of fins with an appropriate pitch has been clarified. According to such a heat transfer tube, the heat transfer area can be expanded by the fins on the outer peripheral surface of the tube, the heat transfer performance can be improved, and the inner surface of the tube remains smooth, so that the pressure loss in the tube is smoothed. It has the advantage that it can be made comparable to a tube.

  Furthermore, as a heat transfer tube whose heat transfer performance is further improved by optimizing the dimensions and shapes of grooves (notches) and fins formed on the outer peripheral surface of such a tube, for example, JP-A-10-318691 It is made clear in the publication (Patent Document 3). In this way, by optimizing the dimensions and shape of the fins, wetting and spreading of the liquid dropped on the outer surface of the tube is further improved, and the liquid outside the tube and the liquid that can be circulated in the heat transfer tube Heat exchange between the two is advantageously promoted, and the heat transfer performance can be improved.

  By the way, in recent years, in such a heat transfer tube for a falling liquid film type refrigerator, there has been an increasing demand for reducing the weight of the heat transfer tube. An extremely thin one of 0.5 mm or less is also beginning to be adopted. And when producing a heat transfer tube having such a thin tube wall and having fins and grooves formed on the outer surface of the tube, use an original tube with a thickness of around 0.6 mm, By subjecting the surface to rolling or the like, grooves and fins having predetermined dimensions are formed, and the target heat transfer tube is finished.

  However, when a predetermined groove or fin is formed on the outer peripheral surface by subjecting the outer peripheral surface of the original pipe having a thin wall thickness to a disk rolling process, a rolling disk is used. When the outer fin is formed, a hollow extending spirally corresponding to the fin formed on the outer peripheral surface is formed on the inner peripheral surface of the pipe. That is, when the disk rolling process is performed, the fins are formed by being raised from the outer peripheral surface of the pipe, so that the metal of the pipe wall is formed in the fin forming position from both the left and right sides. As a result of such a metal flow, a phenomenon occurs in which a spiral recess along the formed fin is formed on the inner surface of the tube immediately below the fin. is there.

  Such a spiral recess on the inner surface of the tube is unlikely to occur when the thickness of the original tube subjected to the disk rolling process is thick, but in order to form a light single heat transfer tube, When a thin original tube is used, it is difficult to suppress the occurrence. And the spiral hollow directly under the fin formed on the inner surface of the tube newly causes a problem that the pressure loss inside the tube increases. For this reason, it is possible to reduce the depression on the inner surface of the pipe by simply lowering the height of the fin formed on the outer surface of the pipe. However, there was a risk of causing a decrease in heat transfer performance. Therefore, in order to effectively suppress such an increase in pressure loss in the pipe while exhibiting the effect of improving heat transfer performance by the outer fins, for the falling liquid film type refrigerator where the dent depth on the pipe inner face is made as small as possible There is a need for heat transfer tubes.

JP-A-1-134180 JP-A-62-206356 Japanese Patent Laid-Open No. 10-318691

  Here, the present invention has been made in the background of such circumstances, the place to solve the problem, without reducing the heat transfer performance improvement effect by the grooves and fins formed on the outer surface of the tube, It is an object of the present invention to provide a heat transfer tube for a falling light film type refrigerator with a light single weight, in which the pressure loss inside the tube is advantageously reduced. Moreover, in the present invention, it is also an object to solve the problem by providing a method for advantageously producing such a heat transfer tube for a falling liquid film type refrigerator.

In the present invention, in order to solve such problems, the falling liquid film type refrigerator is configured such that the absorption liquid flows down in the form of a film on the outer surface of the pipe, while the cooling medium flows in the pipe. The heat transfer tube has fins extending in the tube axis direction and having a trapezoidal cross section on the outer surface of the tube, fin height: 0.15 to 0.35 mm, and fin pitch in the tube axis direction: 0.9 to 2 4 mm, fin minimum width: 0.3 to 0.7 mm, tube bottom wall thickness: 0.40 to 0.55 mm, root R in fin tube axis direction cross section: 0.05 to 0.3 mm, The axial groove having a groove depth shallower than the height of the fin is formed in a spiral form, and the groove depth is 0.1 to 0.3 mm. pitch: 0.5 to 1.0 mm, the difference between the fin height and the groove depth (d ₁₎ and the fin height (H) in the ratio (d ₁ /H):0.05~0.25 with, is formed in the tube axis direction, the depth of the recess is formed in the tube surface corresponding to the disposed position of the said fin ( The gist of the heat transfer tube for a falling liquid film type refrigerator is characterized in that d ₂ ) is configured to be 0.03 mm or less.

  Further, according to the present invention, there is provided a method for manufacturing such a heat transfer tube, wherein a metal tube having a simple circular cross-sectional shape and smooth on the inner and outer surfaces is used, and the radius of curvature of the edge portion of the tip is formed on the outer surface of the metal tube. Pressing a rolling disc having a thickness of 0.05 mm or more to form the fin on the outer surface of the metal tube, and pressing a gear-shaped disk tool against the formed fin, the shaft The gist of the present invention is also a method of manufacturing a heat transfer tube for a falling liquid film refrigerator, which includes a step of forming a directional groove in the fin.

  Therefore, according to the heat transfer tube for a falling liquid film type refrigerator configured in accordance with the present invention as described above, the fin having a trapezoidal cross section formed on the outer surface side of the heat transfer tube so as to extend in the tube axis direction. It is possible to secure a sufficient surface area from the fact that the height and fin pitch, and the groove depth and groove pitch of the axial groove having a groove depth shallower than the fin height of the fin are set to appropriate dimensions. In addition, high wettability on the surface of the tube can be obtained, so that the heat transfer performance of the heat transfer tube can be advantageously improved.

  In addition, when the size of the root R in the cross section in the tube axis direction of the fin formed on the outer surface of the heat transfer tube is 0.05 mm or more and 0.3 mm or less, the outer surface fin is formed by the disk rolling process. In addition, it is possible to effectively suppress the depression generated on the inner surface of the pipe due to the flow of the metal material forming the pipe wall, and to exhibit the characteristics that can advantageously suppress the root crack of the fin during fin processing. .

  And since the depth of the hollow formed in the inner surface side of a heat exchanger tube is 0.03 mm or less, it becomes possible to suppress effectively the pressure loss of the fluid circulated through the heat exchanger tube. Therefore, it is possible to advantageously realize the heat transfer tube for a falling liquid film type refrigerator that can sufficiently exert the heat transfer acceleration effect given to the outer surface of the tube and can advantageously reduce the pressure loss inside the tube. It was possible to do that.

  In addition, as a method of manufacturing a heat transfer tube for a falling liquid film type refrigerator according to the present invention, the radius of curvature of the edge portion of the tip is 0.05 mm on the outer surface of a circular metal tube having a simple cross section and smooth inner and outer surfaces. A method of forming the fins by pressing the rolling disk formed as described above, and pressing the gear-shaped disk tool against the formed fins to form the axial grooves in the fins. By adopting, the depth of the recess formed on the inner surface of the heat transfer tube with the formation of the outer fins can be effectively suppressed to 0.03 mm or less. In addition, it is possible to form the target heat transfer tube for the falling film type refrigerator only by rolling the smooth tube, so that the productivity can be advantageously improved. .

  Hereinafter, in order to clarify the present invention more specifically, embodiments of the present invention will be described in detail with reference to the drawings.

First, FIG.1 and FIG.2 each shows one Embodiment of the heat exchanger tube for falling film type refrigerators according to this invention. That is, FIG. 1 is a perspective view in which a part of the tube wall of such a falling film type refrigerator heat transfer tube is cut out, and FIG. 2A is a diagram in the tube axis direction of the tube wall. In the form of a cross-sectional view, FIG. 2 (b) shows a cross-sectional view in the pipe circumferential direction of the pipe wall. As shown in FIGS. 1 and 2, the heat transfer tube 10 is formed on the outer surface thereof with fins 12 extending spirally in the tube axis direction at a predetermined pitch (P ₁ ) in the tube axis direction. At the same time, grooves 14 having a groove depth shallower than the height of the fins 12 are formed with a predetermined pitch (P ₂ ) in the axial direction. In addition, a recess 16 corresponding to the fin 12 formed on the outer peripheral surface of the heat transfer tube 10 is inevitably formed with a depth: d ₂ on the inner peripheral surface of the heat transfer tube 10.

  More specifically, the heat transfer tube 10 is a tube formed using a metal material such as aluminum, copper, or an alloy thereof, and the diameter thereof is generally about 10 mm to 25 mm. , The bottom wall thickness (t) of the tube is desirably 0.55 mm or less. In addition, from the viewpoint of the rigidity and corrosivity of the heat transfer tube 10, such a bottom wall thickness is generally set to 0.40 mm or more in general.

Further, as shown in the cross-sectional views of FIGS. 2A and 2B, fins 12 extending spirally in the tube axis direction are provided on the outer peripheral surface of the fin height (H): 0. 15 to 0.35 mm, fin pitch (P ₁ ) in the tube axis direction: 0.9 to 2.4 mm, minimum fin top width (W): 0.3 to 0.7 mm, cross section (tube (Axial cross section) is formed to have a trapezoidal shape. In addition, the root 18 of such a fin 12 has a smooth arc shape in the cross section in the tube axis direction, and is formed so that the radius of curvature (R) is 0.05 to 0.3 mm. ing.

On the other hand, the groove 14 extending in the tube axis direction and having a groove depth shallower than the height (H) of the fin 12 has a groove depth (D) of 0.1 to 0.3 mm, and a groove pitch in the tube circumferential direction. (P ₂ ): The size is 0.5 to 1.0 mm, and the fins 12 are notched. The depth of the groove 14 is the ratio (d ₁ / H) of the difference (d ₁ ) between the height (H) of the fin 12 and the depth (D) of the groove 14 and the fin height (H). Is 0.05 to 0.25. This is because if this ratio is increased, wetting and spreading of the liquid film of the absorbing liquid dropped on the outer periphery of the tube in the tube axis direction will be hindered, resulting in a decrease in heat transfer performance. . On the other hand, when this ratio is less than 0.05, it becomes easy to cause cracks at the bottom of the groove when the groove 14 is processed into the fin 12, or unevenness due to the groove processing is formed on the inner peripheral surface of the pipe. The problem that it is easy to form will be caused.

Further, a recess 16 corresponding to the fin 12 formed so as to extend spirally in the tube axis direction with respect to the outer peripheral surface on the inner peripheral surface of the heat transfer tube 10 has a depth (d ₂ ) of 0. It is made to be 03 mm or less, and is unavoidably formed. Similar to the fin 12, the recess 16 extends spirally in the tube axis direction, and is continuous with the inner peripheral surface of the portion immediately below the fin 12, in other words, the portion corresponding to the substantially central portion in the width direction of the fin 12. Is formed.

  And the heat exchanger tube 10 comprised in this way suppresses the weight increase of the heat exchanger tube 10 by the volume of a fin part by the fin 12 and the groove | channel 14 which were formed in the outer peripheral surface with the optimized dimension, and the heat exchanger tube 10 It is possible to reduce the unit weight of the heat transfer tube 10 and to effectively increase the surface area thereof, advantageously increasing the contact area between the absorption liquid dropped onto the heat transfer tube 10 and the heat transfer tube 10, and heat exchange. The performance can be improved. Further, the absorbing liquid dropped on the outer peripheral surface of the heat transfer tube 10 is effectively spread in the tube axis direction and the tube circumferential direction by the fins 12 and the grooves 14, so that the wettability of the heat transfer tube 10 is increased. Therefore, the heat exchange performance of the heat transfer tube 10 can be further improved.

  Moreover, in this heat exchanger tube 10, since the bottom wall thickness (t) of the tube body constituting the heat transfer tube 10 is 0.40 mm to 0.55 mm, the weight (single weight) of the single tube is more increased. It is possible to reduce the weight.

  And by setting the curvature radius (R) of the base of the fin 12 to 0.05 mm or more, when the heat transfer tube 10 having such a small bottom wall thickness is formed by disk rolling, the base of the fin is cracked. The depth of the recess 16 formed on the inner peripheral surface of the pipe corresponding to the fin 12 during the disk rolling process of the fin 12 can be effectively reduced to 0.03 mm or less. It can be suppressed. If the radius of curvature (R) at the base of the fin 12 is too large, the substantial thickness of the fin 12 will increase, leading to an increase in the unit weight of the heat transfer tube 10. It is desirable to set it to 3 mm or less.

  Furthermore, the pressure loss inside the heat transfer tube 10 can be effectively reduced by suppressing the depth of the recess 16 formed on the inner peripheral surface of the heat transfer tube 10 to 0.03 mm or less by rolling the fins 12. It is possible to suppress it.

  Thus, according to the heat transfer tube 10 for a falling film membrane refrigerator according to the present invention, even if the bottom wall thickness of the tube is reduced to form a light single heat transfer tube, The depth of the formed depression 16 is effectively reduced to advantageously reduce the pressure loss inside the heat transfer tube 10 and the heat transfer performance is improved by the fins 12 and the grooves 14 formed on the outer peripheral surface of the heat transfer tube 10. The effect can be exhibited advantageously, and high heat exchange performance can be realized. And by using the heat transfer tube 10 having such a light unit weight and high heat transfer performance, the absorber and the evaporator of the falling liquid film type refrigerator or the evaporator of the adsorption type refrigerator are improved in performance. In addition, the effects of downsizing the device and lowering the manufacturing cost can be advantageously exhibited.

  By the way, as shown below, the heat transfer tube 10 for a falling liquid film type refrigerator configured as described above is provided with a rolling processing apparatus as shown in FIG. 3, for example, according to a known rolling processing method. To be produced advantageously.

  That is, the outer surface fin rolling tool 30 comprising a plurality of fin-forming disks 32 having concentrically increasing diameters, which are concentrically attached to the rotational drive shaft 34 at predetermined intervals, as shown in FIG. Around the elementary pipe 36 sized to give the flowing-down liquid film refrigerator heat transfer pipe 10, three are arranged with a phase difference of about 120 °. Further, as shown in FIG. 4, the plurality of fin forming disks 32 are concentrically and integrally formed by the rotation drive shaft 34 at intervals giving a pitch of the fins 12 formed on the outer peripheral surface of the raw tube 36. It is connected to. Further, such a rotational drive shaft 34 is positioned with respect to the tube axis of the tube 36 at an angle corresponding to the lead angle of the fin 12 formed on the outer surface of the tube 36. Further, a plug 38 is inserted inside the element tube 36 so as to face each fin forming disk 32, and the element tube 36 is deformed between the plug 38 and the fin forming disk 32. It has come to be.

  Then, using the three outer surface fin rolling tools 30 arranged in this way, the central portion of the three outer surface fin rolling tools 30 is rotated while rotating the fin forming disk 32 by the rotation drive shaft 34. As the raw pipe 36 passes, the fins 12 having a predetermined height are gradually projected outward in the radial direction on the outer peripheral surface of the raw pipe 36 so as to continuously extend in a spiral shape in the pipe axis direction. It will be formed by rolling.

  By the way, as shown in FIG. 5 (a), the fin forming disk 32 used when the fin 12 is formed by such an external fin rolling tool 30 has a radius of curvature (R ) Of 0.05 mm or more, the radius of curvature (R) of the root 18 of the fin 12 formed on the outer surface of the raw tube 36 can be effectively 0.05 mm or more, and As a result, it is possible to effectively reduce the depth of the recess 16 that is formed inside the pipe as the fin 12 is processed. 5B, when the fin 12 is formed, the recess 16 has a direction in which the metal on the tube wall of the base tube 36 protrudes by the fin forming disks 32 and 32. It will inevitably occur because it is made to flow.

  After that, by pressing the fin 12 and forming the groove 14 with a gear-shaped disk tool having a shape that gives a desired cross-sectional shape and depth, as shown in FIG. 1 and FIG. The heat transfer tube 10 for the falling liquid film refrigerator having the fins 12 and the grooves 14 formed on the outer peripheral surface is formed. In addition, the disk tool which forms such a groove | channel 14 is with respect to all the three tools at the minimum of one of the three fin rolling tools 30 arrange | positioned around this raw pipe | tube 36 at the maximum. Thus, it is attached to the rotary drive shaft 34 on the downstream side (the right side in FIG. 4) in the fin forming direction, and is pressed against the fin 12 of the raw pipe 36 where the fin 12 has been processed.

  Through such a process, the target heat transfer tube 10 for the falling film type refrigerator is formed from the simple pipe 36 having a circular cross section. For such a falling film type refrigerator, According to the method of manufacturing the heat transfer tube 10, the fins 12 and the grooves 14 are formed in the raw tube 36 having a simple circular cross section using only the rolling process in which the manufacturing process is relatively easy, and the heat transfer tube. Since it is possible to produce the heat transfer tube 10 in which the depth of the recess 16 formed on the inner surface of the tube 10 is effectively reduced, the productivity of the heat transfer tube 10 is increased, and the production cost is effectively reduced. It can be done.

  As mentioned above, one of the representative embodiments of the present invention and the manufacturing method thereof have been described in detail. However, these are merely examples, and the present invention is specific to such embodiments. It should be understood that the description is not to be construed as limiting in any way. Moreover, although not enumerated one by one, the present invention is implemented in an aspect to which various changes, modifications, improvements, and the like are added based on the knowledge of those skilled in the art. It goes without saying that any one of them falls within the scope of the present invention without departing from the spirit of the present invention.

  In the following, one of the representative embodiments of the present invention will be shown to clarify the features of the present invention. However, the present invention is not restricted by the description of such embodiments. It goes without saying that it is not a thing.

  First, as a test heat transfer tube, an outer diameter having a simple circular cross-sectional shape is used to form a heat transfer tube for a falling liquid film refrigerator having an outer surface shape as shown in FIG. 1 or FIG. : A raw tube made of phosphorous deoxidized copper (JIS H 3300 C1220) having a thickness of 16 mm and a wall thickness (tube wall thickness) of 0.65 mm was prepared.

  And according to the manufacturing method of the heat-transfer pipe | tube for flowing-down liquid film type refrigerators according to this invention mentioned above with respect to such an elementary pipe, a disk rolling process is given and the fin 12 and the groove | channel 14 are provided in this elementary pipe outer peripheral surface. The various heat transfer tubes 10 having different values such as the fin height, fin pitch, fin root R, etc. of the fins 12 and grooves 14 as shown in Table 1 were formed. . In addition, in each test heat transfer tube, each dimension value was within the range according to the present invention, and was designated as Example 1 to Example 13, and the dimension value outside the scope of the present invention, Comparative Examples 1 to 12 were used.

  For the test heat transfer tubes of Examples 1 to 13 and Comparative Examples 1 to 12 prepared in this way, a general testing machine composed of conventionally known absorbers, evaporators, regenerators, and condensers , Pressure inside the vessel: 840 Pa, inlet temperature of the lithium bromide aqueous solution dropped outside the heat transfer tube: 53.5 ° C., inlet concentration: 63.5%, liquid film flow rate: 0.015 kg / (m · s), under the conditions of the inlet temperature of the cooling water flowing through the heat transfer tube: 32 ° C. and the flow velocity in the tube: 1.5 m / s, an experiment was conducted to measure the absorption heat transfer performance, and the heat passage rate and the pressure in the tube Each loss was measured, and the results are shown in Table 2 below. In Table 2, the heat passage rate and the in-tube pressure loss of each test heat transfer tube when the heat passage rate and the in-tube pressure loss in Comparative Example 2 are set to 100 are shown as ratios, respectively.

As is clear from the results of Table 2, in each of the heat transfer tubes of Examples 1 to 13 in which the specification values of the fins 12 and the grooves 14 are within the scope of the present invention, the heat transfer rate is improved in all of them. It is recognized that Further, even in the pressure loss inside, the tube circumference formed in the recess depth: d ₂ than the heat transfer tube of Comparative Example 1 and Comparative Example 5 is outside the scope of the present invention, and within the scope of the present invention It can be confirmed that the pressure loss is reduced in all the heat transfer tubes of Examples 1 to 13.

It is an isometric view explanatory drawing which shows an example of the heat exchanger tube for falling liquid film type refrigerators according to this invention in the state which notched a part of tube wall. An example of a heat transfer tube for a falling liquid film type refrigerator according to the present invention is an explanatory diagram showing in the form of a cross-sectional view, (a) is a cross-sectional explanatory diagram in which the tube wall is cut in parallel to the tube axis direction, (B) is sectional explanatory drawing cut | disconnected by the surface parallel to the direction where an outer surface fin is extended. It is sectional explanatory drawing which shows an example of the rolling processing apparatus which manufactures the heat exchanger tube for falling liquid film type refrigerators according to this invention in a longitudinal cross-sectional form. It is a cross-sectional explanatory drawing which shows one of the tools for three fin rolling of the rolling processing apparatus shown by FIG. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional explanatory view schematically illustrating a state when forming outer surface fins of a heat transfer tube for a falling liquid film type refrigerator in a disk rolling process, wherein (a) is an edge portion at the tip of a rolled disk; Shows a case where the size is within the range according to the manufacturing method according to the present invention, and (b) shows a case where a conventional rolled disk is used.

Explanation of symbols

10 Heat Transfer Tube 12 Fin 14 Groove 16 Recess 18 Fin Base

Claims (2)

While the absorption liquid flows down in the form of a film on the outer surface of the pipe, a heat transfer pipe for a falling liquid film type refrigerator that allows the cooling medium to flow in the pipe,
A fin extending in the tube axis direction and having a trapezoidal cross section on the outer surface of the tube has a fin height of 0.15 to 0.35 mm, a fin pitch in the tube axis direction of 0.9 to 2.4 mm, and the top of the fin. Minimum width: 0.3 to 0.7 mm, tube bottom wall thickness: 0.40 to 0.55 mm, root R in fin tube axis direction cross section: 0.05 to 0.3 mm, rolled into a spiral shape As well as
For such fins, axial grooves having a groove depth shallower than the fin height are groove depth: 0.1 to 0.3 mm, groove pitch in the pipe circumferential direction: 0.5 to 1.0 mm, fins The ratio of the difference between height and groove depth (d ₁ ) to fin height (H) (d ₁ / H): 0.05 to 0.25, formed in the tube axis direction, and the arrangement of the fins A heat transfer tube for a falling liquid film type refrigerator, characterized in that the depth (d ₂ ) of a recess formed on the inner surface of the tube corresponding to the part is 0.03 mm or less. The method for manufacturing a heat transfer tube according to claim 1, wherein a metal tube having a simple circular cross-sectional shape and smooth on both the inner and outer surfaces is used, and the curvature radius of the edge portion of the tip is 0.05 mm on the outer surface of the metal tube. The step of pressing the rolling disk as described above to form the fin on the outer surface of the metal tube, and pressing the gear-shaped disk tool against the formed fin, the axial groove A method of manufacturing a heat transfer tube for a falling-film-type refrigerator.

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