JPH0160332B2 - - Google Patents

Description

[Detailed description of the invention]

(Technical Field) The present invention relates to a method for manufacturing heat transfer tubes suitable for use in condensers as heat exchangers for air conditioners, refrigerators, boilers, etc., which effectively improves heat transfer characteristics particularly on the outer surface of the tube. The present invention relates to a manufacturing method for easily manufacturing heat exchanger tubes. (Background Art) In general, such heat transfer tubes perform heat exchange between, for example, a heat transfer fluid (cooling liquid) that flows through the inner surface of the tube and a heat transfer fluid (condensable gas) that is brought into contact with the outer surface of the tube. It is used to condense and liquefy condensable gases. In this type of heat exchanger tube, especially in condensing heat exchanger tubes, an important issue is how to increase the heat transfer coefficient on the tube's outer surface, and ultimately the condensing efficiency.For this purpose, spiral fins are formed on the tube's outer circumferential surface. Loaf-in tubes are known. In such a loaf-in tube, by forming a large number of outer surface fins, a wider contact area is ensured than in a smooth tube in which no fins are formed at all.
Although we can expect some improvement in the heat transfer performance on the outer surface of the tube, this does not mean that we can be fully satisfied. The reality is that there is a strong demand for the development of even more advanced heat transfer tubes. (Object of the Invention) The present invention has been made based on the above-mentioned circumstances, and its object is to integrally form outer fins in the circumferential direction on the outer surface of the pipe at a predetermined pitch. In a heat transfer tube in which a groove is formed between the outer surface fins and extends in the circumferential direction of the tube,
It is an object of the present invention to provide a method for easily manufacturing a heat exchanger tube that can effectively increase its external heat transfer coefficient. (Solution Means) In order to achieve the above object, in the present invention, the outer fins are formed by rolling by pressing a fin forming disk against the outer peripheral surface of the raw tube that provides the intended heat transfer tube. On the other hand, on the downstream side of the fin forming disk in the outer fin forming direction, a cut groove forming disk having a plurality of cutting teeth at a predetermined pitch is arranged such that its axis is concentric with the outer fin forming disk. At the same time, the plurality of cutting teeth are inclined at an angle of 10 to 60 degrees with respect to the axis thereof, and the cutting depth thereof is set at an angle of 10 to 60 degrees with respect to the axis thereof, and the cutting depth thereof is The inclined cutting teeth of the groove-forming disk are pressed, and the portion pressed by the cutting teeth becomes a trough. A pressing force is applied to the cutting tooth pressing portion along the inclination direction of the cutting tooth on one side of the groove portion located on both sides of the outer surface fin. (Function/Effect) If a heat transfer tube is manufactured using such a groove-forming disk, the troughs will be inclined within the range of 10 to 60 degrees with respect to the direction perpendicular to the longitudinal direction of the fins. At the same time, due to the rotational pressing action of the cutting groove forming disk, pressing force is applied to one side of the groove along the inclination direction of the cutting teeth. The metal material that was present in the groove is moved to one side of the valley, and as a result, a hook-like portion can be easily formed. That is, according to this manufacturing method, peaks and valleys are alternately formed on the outer fin along its longitudinal direction, the outer fin is divided by the valleys, and the valleys form the fin. The fins are formed so as to be inclined parallel to each other within a range of 10 to 60 degrees with respect to the direction perpendicular to the longitudinal direction, and the fins are formed so as to be inclined in parallel to each other in the range of 10 to 60 degrees, and the fins become closer to the top and to one of the troughs in the longitudinal direction of the fin. The closer it gets, the more hook-like it is formed to extend toward one of the grooves located on both sides of the peak. In this way, the effective contact area on the outer surface of the tube can be increased by forming the troughs at an angle, and the hook-like extending portions of the crests also contribute to increasing the contact area. However, by combining these factors, we succeeded in effectively improving the heat transfer coefficient, especially the condensing performance, on the outer surface of the tube. In addition, considering the good results actually obtained,
In addition to simply being able to increase the contact area of the outer surface of the tube with the heat transfer fluid (e.g. condensable gas), the hook-like part of the peak plays a special role mainly in improving the condensing performance. It is speculated that this is because the tips of many hook-like parts form many points that promote condensation. In addition, when simply forming peaks and valleys,
According to the present invention, the peaks are in the form of sharp protrusions that protrude radially outward from the outer surface of the tube.
Since the hook-like portions of the peaks are formed so as to extend toward one of the grooves, the peaks are less likely to bite into each other when such heat exchanger tubes are loaded, and also has the advantage of improved handling properties. It is possible. (Specific Configuration/Examples) In order to clarify the configuration of the present invention more specifically, the present invention will be described in detail based on the examples shown in the drawings. First, FIG. 1 is a partially cutaway view showing an example of a condensing heat transfer tube obtained by applying the method of the present invention, in which 10 is a heat transfer tube made of copper, copper alloy, aluminum, aluminum alloy, etc. This is a condensing heat exchanger tube made of metal with high efficiency. On the outer circumferential surface of the heat transfer tube 10, spiral outer surface fins 12 are integrally formed in the tube circumferential direction at a predetermined pitch.
As a result, a groove portion 14 is formed between these outer surface fins 12 and extends spirally in the tube circumferential direction. A part of the outer surface of the heat exchanger tube 10 is shown in enlarged form in FIGS. 2a and 2b. FIG. 2a is an enlarged plan view of the tube outer surface viewed from directly above, and FIG. 2b is an enlarged view of the tube outer surface viewed from diagonally above. As is clear from these figures, the outer fin 12 has peaks 16 and troughs 18 alternately formed along its longitudinal direction, and the outer fin 12 is divided by the troughs 18. It's summery. Furthermore, the troughs 18 are provided so as to be inclined parallel to each other by an angle θ with respect to the tube axis direction, or more precisely, with respect to a straight line O perpendicular to the longitudinal direction of the outer surface fin 12. This angle θ is within the range of 10 to 60°. In addition, each mountain portion 16 is not simply made to protrude toward its top, but as shown in FIG. 2b.
As is clear from the figure, the grooves 1 located on both sides of the peak 16 grow closer to the top.
It is formed so as to extend in a hook shape toward one of the groove portions 14b among the groove portions 4a and 14b, and the portion extending in this manner is defined as a hook portion 20. Moreover, as shown in FIG.
Slope 16a on one side of valley 18 among a and 16b
The closer the hook-like portion 20 is to the groove portion 14b, the more it extends toward the groove portion 14b, and the tip of the hook-like portion 20 has a sharp point. In other words, each peak 16 is twisted by an angle θ rather than being perpendicular to the fin length direction, and a hook-shaped portion 20 is formed on one side of the fin, so that the hook-shaped portion 20 is formed on the same side. It extends to Moreover, in the adjacent outer surface fins 12, 12,
The respective peak portions 16 and valley portions 18 are formed approximately alternately in a direction forming an angle θ with respect to the straight line O, and the hook-shaped portions 20 extending toward the groove portion 14b are formed in the groove portion 14b. The grooves 14b extend toward the valleys 18 of the outer surface fins 12 adjacent to each other with the grooves 14b interposed therebetween, and the grooves 14b extend in the tube circumferential direction while maintaining a substantially constant width in a zigzag shape. The above can be said in common to the outer surface fin 12 located between the grooves 14b and 14c as well as to each of the grooves 14a and 14c. Note that Fig. 2 a and b are for the case of θ = 30°, Fig. 3 a and b are for the case of θ = 20°, and Fig. 4 a and b are for the case of θ = 45°. The modes for each case are shown. As is clear from those figures, the larger θ becomes, the more
The hook-like portion 20 of No. 6 is sharper and longer, and extends into the groove on one side. Incidentally, in the past, as shown in FIGS. 5a and 5b, the troughs 18 are parallel to the straight line O perpendicular to the longitudinal direction of the fin, that is, θ=0°, and the peaks 16 are approximately square. It has a truncated conical shape, and the bottom portion of the valley portion 18 is simply pushed out evenly to the groove portions 14 on both sides. On the other hand, Fig. 2 a, b to Fig. 4 a, b
In the heat exchanger tube obtained according to the present invention shown in FIG. , the contact area for the condensable gas brought into contact with the outer surface of the tube is large, and therefore the condensation efficiency is effectively increased. In addition to simply increasing the contact area, the presence of the hook-like portions 20 also provides a large number of sharp point-like portions. It is presumed that this prevents the formation of a liquid film and promotes droplet-like condensation, contributing to improved condensation performance. In fact, Figure 5 a, b
It has been confirmed that the condensing heat transfer performance is improved by approximately 30% compared to the conventional heat transfer tube shown in . Further, the peak portion 16 of the conventional heat exchanger tube existed as a sharp projection in the shape of a square frustum, but in the case of the heat exchanger tube obtained according to the present invention, the peak portion 16 is oriented radially outward from the outer surface of the tube. The heat exchanger tube does not protrude sharply, but rather has a hook-like portion 20 that is curved in a direction parallel to the tube axis. When handling the heat exchanger tubes, the fibers of the gloves are much less likely to adhere to the ridges 16 than in the past, and when the heat transfer tubes are stacked, the ridges are prevented from digging into each other. In order to
Another advantage is that it is easy to align the heat exchanger tubes in the tube axis direction in a stacked state. Incidentally, the inclination angle θ of the valley portion 18 with respect to the straight line O perpendicular to the longitudinal direction of the fin is 10 to 10, as described above.
Selected within the range of 60°. This is because when θ is smaller than 10°, there is no significant improvement in heat transfer efficiency or handling compared to the conventional heat transfer tubes shown in Figures 5a and b. ,θ
If the angle exceeds 60°, it becomes difficult to process the valley 18, although it is not impossible.
This is because even if θ is increased in this way, it is difficult to obtain a commensurate effect, leading to an increase in processing costs. Therefore, the above angle θ is 10~
It is necessary to select the angle within the range of 60°, but it can be said that the range of 15 to 45° is particularly suitable. By the way, a heat exchanger tube having the above-mentioned excellent characteristics can be easily manufactured as follows. A specific example of the manufacturing method will be explained based on FIGS. 6 and 7. In FIG. 6, reference numeral 22 denotes a plurality of fin-forming disks, which have gradually increasing diameters and are concentrically and integrally connected by a shaft 24 at intervals that provide the pitch of the outer fins 12. Ori,
Furthermore, adjacent to and concentrically with the largest diameter fin forming disk 22, a groove forming disk 26 is provided.
is attached to the shaft 24. This cutting groove forming disk 26 is disc-shaped and has a plurality of cutting teeth 28 at a predetermined pitch on its outer circumference, and the radius of the circumference drawn by the tips of the cutting teeth 28 is is smaller than the largest diameter of the fin-forming disks 22 by a certain amount. Moreover, as is clear from FIG. 7a, these cutting teeth 28 are all inclined at an angle θ with respect to the axis of the cutting groove forming disk 26, and this inclination angle θ is 10 -60°, which corresponds to the inclination angle θ of the trough 18 shown in FIG. 2a, etc. Then, the shaft 24 to which the outer surface fin forming disk 22 and the cut groove forming disk 26 are attached,
The plug 31 is positioned at an angle corresponding to the lead angle of the outer fin 12 to be formed with respect to the center line of the raw tube 30 that provides the intended heat transfer tube, and a plug 31 is inserted inside the raw tube 30. be done. In this state, by rotating the fin-forming disk 22 via the shaft 24 and pressing it against the outer peripheral surface of the raw tube 30, the outer surface fins 12 are gradually rotated while rotating the raw tube 30 around the tube axis. While forming the outer surface fins 12, the cut groove forming disk 26 disposed on the downstream side in the outer surface fin forming direction indicated by the white arrow of the fin forming disk 22 forms the outer surface fins 12 as described above.
By pressing the cut teeth 28 of the cut groove forming disk 26, rolling is performed so that the portion pressed by the cut teeth 28 becomes the valley portion 18, and the valley portion 18 and the peak portion as described above are formed. 16 are formed alternately. Therefore, the cutting teeth 28 of the cutting groove forming disk 26
is inclined at an angle θ with respect to its axis, so when the cut groove forming disk 26 is rotated and pressed against the raw pipe 30, as shown in FIG. 7b, the rotation Due to the pressing action, in the portion of the outer fin 12 that is pressed by the cutting teeth 28, as shown in FIG. A pressing force P along the line acts. This pressing force P is applied to the grooves 14 located on both sides of the outer fin 12.
As a result, the metal material that was present in the part that should become the valley 18 is
It is moved toward one of the grooves 14 along the cutting teeth 28, and the above-mentioned crest 12 and, in turn, the hook-shaped portion 20 are formed. Incidentally, when manufacturing a conventional heat exchanger tube as shown in FIGS. 5a and 5b, as shown in FIGS. A disk 32 is used with cutting teeth 34 parallel to the
4, the cross-sectional area of the tip of the outer fin 12 is significantly reduced, and the reduced area is pushed out toward the grooves 14 on both sides, and that portion G becomes the outer fin 12. The flow of condensate in the groove portion 14 between the two is likely to be obstructed. On the other hand, as mentioned above, the groove forming disk 26 is provided with the cutting teeth 28 inclined by the angle θ.
If the angle θ is about 20°, as shown in FIG. The groove 14 is divided into sections with almost no reduction in cross-sectional area at the groove 14, and extends in a hook-like manner toward one of the grooves 14. Note that if the inclination angle θ of the cutting teeth 28 is selected in the range of 30 to 45 degrees, as shown in FIG. If the angle θ exceeds 60°, durability problems such as the cutting teeth 28 becoming susceptible to chipping may occur, and processing costs for forming the cutting teeth 28 may increase. This is the main reason why the inclination angle θ of the cutting tooth 28 is set to 60° or less. In any case, the inclined cutting teeth 2 as described above
If the pressurizing force P is applied at step 8, the second
It is possible to easily manufacture a heat transfer tube with peaks 16 and valleys 18 as shown in Figures a, b, etc., and the processing cost of the cutting teeth 28 is slightly higher than that of conventional ones that are not inclined. However, since no special processing equipment is required, the increase in cost is practically negligible. Next, we will discuss specifically how much the condensing performance of the heat exchanger tube obtained in this way can be improved.
The data of the tests conducted by the present inventors are shown below. This test was conducted under the following test conditions for condensable gas (Freon R-22) that was brought into contact with the outside surface of the tube, and the results are shown in Table 1. However, for comparison, data on a conventional heat exchanger tube in which the inclination angle θ of the valley portion is 0° is also listed. [Test conditions] Outer diameter: 19.05mm (outer diameter of raw pipe) Number of fins: 19 threads/inch Cutting teeth: 1mm pitch x 0.7mm depth Inner diameter: 14.80mm Condensing temperature: 40℃ Cooling water inlet temperature: 30℃ Cooling water flow rate: 1.5~3.0m/sec

[Table] * Outer diameter standard As is clear from the results shown in Table 1, the diameters obtained according to the present invention were obtained when the inclination angle θ of the trough (cutting tooth) was 20°, 30°, and 45°. The condensation heat transfer coefficient h ₀ on the tube outer surface is approximately 30% higher than that of conventional heat exchanger tubes with an angle of inclination of 0°.
It is nearly 50% higher, which means that the condensation performance on the outer surface of the tube can be improved accordingly. Although the present invention has been described above based on specific examples and test data, it goes without saying that the present invention is not to be construed as being limited by such specific descriptions. For example, it is also possible to form recesses (dimples) in the bottom portions of the grooves of adjacent outer fin tubes, and to arrange inner protrusions in a spiral shape on the inner surface of the tubes corresponding to the recesses. By forming a recess in the groove on the outer surface of the tube and an inner protrusion on the inner surface of the tube, the contact area on the outer surface of the tube can be further increased, and the condensation efficiency can be further increased. By applying a turbulent flow to the flow of the heat transfer fluid (cooling water), it is possible to suppress the formation of a film that inhibits the heat transfer coefficient. In order to manufacture such a heat transfer tube, for example, a serrated disk is disposed downstream of the outer surface fin-forming disk and upstream of the notched tooth-forming disk, and the formed outer surface is By pressing the serrations of the serrated disk against the bottom of the groove between the fins, the pressed portion of the serration is made to protrude into the inner surface of the tube as a recess. The crests and troughs may be formed using the cutting tooth forming disc as described above. Furthermore, all the explanations so far have been about condensing heat exchanger tubes, but if the formation density of the outer surface fins is increased to, for example, 26 to 54 fins/inch,
The spacing between the hook-like portions of the peaks extending on one side of the groove is also very narrow, so that the gaps between these hook-like portions can perform the function of forming nuclei in boiling, and such If this is the case,
It is also possible to use it as an evaporation tube. In other words, the present invention can be applied not only to condensation pipes but also to evaporation pipes, and as mentioned above, if a recess is provided at the bottom of the groove, a synergistic effect can be expected. can. In addition, without departing from the spirit of the present invention, the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art.
There is no need to say it again.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway view of a condensing heat exchanger tube obtained according to the method of the present invention. However, to avoid complexity, the peaks and valleys are omitted. Figures 2 a and b show the outer surface of the heat exchanger tube,
These drawings are sketches of enlarged photographs taken from different angles, and show the case where the inclination angle θ is 30°. Figure 3 a and b and Figure 4 a
and b are views corresponding to FIGS. 2a and b, showing cases where the inclination angle θ is 20° and 45°, respectively. FIGS. 5a and 5b are views corresponding to FIGS. 2a and 2b, respectively, showing a part of a conventional heat exchanger tube in which the inclination angle θ is 0°. FIG. 6 is a process diagram briefly showing a specific example of the method of the present invention, and FIG.
Figures a and b are explanatory diagrams schematically showing, from different angles, how peaks and valleys are formed by this method. FIG. 8 is an explanatory diagram for explaining the state in which pressing force is applied by the inclined cutting teeth. FIGS. 9a and 9b are views schematically showing the conventional method of manufacturing the heat exchanger tube shown in FIGS. 5a and 5b from different angles, and correspond to FIGS. 7a and 7b. be. 10 is a diagram briefly explaining the shapes of peaks and valleys formed according to the method shown in FIGS. 9a and 9b, and FIG.
Figures 1 and 12 each briefly show the shapes of peaks and valleys formed depending on the inclination angle θ of the incisor teeth when the method of the present invention shown in Figure 6 etc. is used. It is a diagram. 10: Condensing heat transfer tube, 12: External fin, 14:
Groove portion, 16: Peak portion, 18: Valley portion, 20: Hook-like portion, 22: Outer surface fin forming disk, 26: Cut groove forming disk, 28: Cut tooth, 30: Raw tube.

Claims (1)

[Claims] 1 Roll-forming outer surface fins by pressing a fin-forming disk against the outer circumferential surface of the raw tube that provides the intended heat transfer tube, and at the same time rolling-forming the outer surface fins at a predetermined pitch on the downstream side of the fin-forming disk in the direction in which the outer surface fins are formed. A groove forming disk having a plurality of cutting teeth is arranged so that its axis is concentric with the outer fin forming disk, and the plurality of cutting teeth are set at an angle of 10 to 60 degrees with respect to the axis. and with respect to the outer fin formed by the outer fin forming disk,
The inclined cutting teeth of the cutting groove forming disk are pressed, and the pressed part by the cutting teeth is rolled to form a trough, and at the same time, due to the rotational pressing action of the cutting groove forming disk, the A heat transfer tube characterized in that a pressing force is applied to the notch pressing portion of the external fin on one side of a groove located on both sides of the external fin along the inclination direction of the notch. manufacturing method.