JPH0335011B2 - - Google Patents

Description

[Detailed description of the invention]

(Technical Field) The present invention relates to a method for manufacturing a heat exchanger tube, and particularly to a method for advantageously manufacturing a condensing heat exchanger tube that is suitably used in a condenser as a heat exchanger in an air conditioner, a refrigerator, a boiler, etc. It is. (Background Art) In general, in such a heat transfer tube, heat is exchanged between a heat transfer fluid (cooling water) that flows through the tube's inner surface and a heat transfer fluid (condensable gas) that is brought into contact with the tube's outer surface. However, traditionally,
Condensers for fluorocarbon-based refrigerant gases such as R11 and R12 are equipped with a loaf-in tube in which spiral fins are formed on the outer circumferential surface of the tube by pressing a fin-forming disk, and to promote heat transfer in such loaf-in tubes. As shown in Special Publication No. 52-11670,
A loaf-in tube with internal ribs has been used in which a spiral rib is provided on the inner peripheral surface of the loaf-in tube. By the way, in a normal loaf-in tube with a smooth inner surface, the heat transfer fluid flowing inside the tube becomes a laminar flow and tends to form a film with poor heat transfer efficiency on the inner circumferential surface of the tube. In loaf-in tubes, the swirling flow created by the swirling of the fluid flow by the inner surface ribs makes it relatively difficult to form a membrane, and is said to be effective in improving the heat transfer coefficient on the inner surface of the tube. . However, even with such a swirling flow, a fluid flow similar to a laminar flow still remains, so the problem of the boundary film has not been solved, and there are limits to promoting internal heat transfer. It was hot. On the other hand, regarding the heat transfer coefficient on the outer surface of the tube, since the formation of a large number of outer surface fins ensures a wide contact area, it is expected that the heat transfer performance will be improved to some extent, but even higher external heat There is a deep-rooted demand for conductivity, and there is a need for heat transfer tubes that have as high an internal and external heat transfer coefficient as possible and have excellent overall heat transfer performance. For this reason, in Japanese Patent Application Laid-open No. 54-157369, a rotary tool placed so as to intersect with the outer fins of the above-mentioned loaf-in tube is pressed against the outer fins to cut the outer fins at a predetermined pitch. At the same time, a heat exchanger tube has been proposed in which the cut portions are arranged at a lead angle opposite to the outer surface fins, and protrusions are formed on the inner surface of the tube at the cut portions. The formation of turbulent zones on the inner and outer surfaces of the tube is contemplated. However, in the heat transfer tube manufacturing method disclosed in this publication, a disc-shaped rotating tool is pressed against the outer fins to cut the outer fins and at the same time cause the parts to protrude inward. For some reason, there is a problem in that the protrusions formed on the inner surface of the tube cannot be formed at a height sufficient to induce effective turbulence, and when the outer fins are cut with a rotating tool, the outer fins are subject to large deformations. There was a problem with receiving it. (Problem to be Solved) The present invention has been made in view of the above circumstances, and its main purpose is to provide effective turbulence to the flow of fluid flowing through the pipe to destroy the film. A heat transfer tube that can cause a flow to effectively increase the internal heat transfer coefficient, and in addition, a heat transfer fluid that is brought into contact with the external surface of the tube can be effectively brought into contact with the external fins to increase the external heat transfer coefficient. It is an object of the present invention to provide a method for easily and advantageously manufacturing a heat exchanger tube that can be further improved. (Solution/Effects) In the present invention, in order to manufacture a heat exchanger tube that exhibits the above-mentioned excellent characteristics, fins are formed on the outer peripheral surface of the base tube that provides the intended heat exchanger tube. A serrated disk in which external fins of a predetermined height are spirally rolled by pressing the disk, and serrations are provided at predetermined intervals on the outer periphery on the downstream side of the fin forming disk in the direction in which the external fins are formed. is arranged so that its rotational axis is positioned at an angle corresponding to the lead angle of the outer fins with respect to the center line of the blank pipe, and the serrated disk is arranged along the groove between the formed outer fins. By rotating the disk and pressing the sawtooth of the serrated disk against the bottom of the groove between the outer fins, a method is adopted in which the pressed portion by the sawtooth protrudes into the inner surface of the tube. In addition, in the present invention, the outer surface fins of a predetermined height are spirally rolled by pressing the fin forming disk against the outer circumferential surface of the raw tube that provides the intended heat transfer tube, and the fins are A serrated disk having serrations provided at predetermined intervals on its outer periphery is provided on the downstream side of the forming disk in the outer fin forming direction, the rotation axis of which corresponds to the lead angle of the outer fin with respect to the center line of the blank pipe. by rotating the serrated disk along a groove between formed outer fins and pressing the serrations of the serrated disk against the bottom of the groove between the outer fins. , the pressing portion of the sawtooth protrudes from the inner surface of the tube, and furthermore, cuts are made at predetermined intervals in the length direction of the rolled outer surface fin. It is. In this way, the inner protrusion can be easily formed at a sufficient height by the serrated disk without damaging the outer surface fin or deforming its shape, and also pressing the outer surface of the tube. Even if an inner protrusion is formed to make it protrude inward,
This provides advantages such as not causing an increase in the weight of the heat exchanger tube. In addition, a heat transfer tube in which spiral outer surface fins made of a tube material are integrally formed on the outer circumferential surface of the tube, which is obtained according to the method of the present invention, is provided, and a plurality of inner surface protrusions are formed on the inner circumferential surface of the tube. , and in the case of a heat transfer tube in which such inner surface protrusions are arranged in a spiral shape, the heat transfer fluid flowing through the tube overcomes the plurality of inner surface protrusions or the direction of flow is changed by such inner surface protrusions. At this time, subtle turbulence occurs, and this change in the flow near the inner surface of the tube effectively destroys the film that tends to form near the inner circumferential surface of the tube, effectively increasing the inner heat transfer coefficient. be. In addition, a plurality of inner protrusions are formed in the arrangement as described above, and the spiral outer surface fins formed on the outer peripheral surface of the tube are cut out by notches spaced at predetermined intervals in the length direction. , and for heat exchanger tubes configured to be divided,
While effective turbulence is induced by the plurality of inner surface protrusions, the heat transfer fluid brought into contact with the outer circumferential surface of the tube can flow across adjacent outer surface fins through the above-mentioned notches, so that the Since the fluids are effectively brought into contact with each other and the contact area is increased, the external heat transfer coefficient can be further increased compared to the conventional method. (Specific Configuration/Example) In order to clarify the configuration of the present invention more specifically, a detailed description will be given below based on drawings showing examples of the present invention. First, FIG. 1 is a partially cutaway view showing an example of a heat exchanger tube obtained according to the method of the present invention, in which 2 is a heat exchanger tube made of a metal with good heat transfer coefficient, such as copper. The outer circumferential surface of the electric heating tube 2 is integrally provided with spiral outer fins 4 made of tube material moved from the tube wall at a predetermined pitch, while the inner circumferential surface of the tube is provided with a plurality of inner surface fins. A protrusion 6 is formed. These inner surface protrusions 6 are formed on the inner peripheral surface of the tube corresponding to the grooves 8 between the outer surface fins 4, and the bottom portions of the grooves 8 in which the inner surface protrusions 6 are located are defined as dimples 10. That is, in this case, by forming the rectangular recess 10 in the bottom portion of the groove 8, the inner surface of the tube corresponding to the recess 10 is made to protrude in the shape of an elliptical hill, and the inner surface protrusion 6 is formed. be. As a result of the inner surface protrusions 6 being formed along the spiral groove 8, the inner surface protrusions 6 are naturally arranged in a spiral shape similar to the spiral shape of the groove 8 on the inner peripheral surface of the pipe. However, depending on the pitch of the recess 10, the inner surface protrusions 6 provided on the inner surface of the tube corresponding to the grooves 8 adjacent to each other in the tube axis direction may have a spiral shape different from that of the grooves 8 as a whole. For example, a clear spiral pattern as shown in FIG. 1 may be formed, or a staggered pattern in which the inner protrusions 6 that are closest to each other are staggered as shown in FIG. It shows a pattern. When the inner surface protrusion 6 is arranged so as to have a spiral shape different from the spiral shape of the groove part 8, the pitch thereof is generally 0.5 to 10 mm in the tube axis direction, and the lead in the tube axis direction. It is preferable that the angle is at least 10° or more, particularly preferably in the range of 20 to 70°. Further, the size of the outer surface fin 8 is such that the pipe diameter is, for example,
In the case of about 20 mm, the fin thickness is usually about 0.2 to 0.4 mm, the height is about 1 to 3 mm, and the interval between the grooves 8 is about 0.5 to 1.3 mm in the tube axis direction. On the other hand, the size of the inner protrusion 6 has a height (protrusion amount) of 0.2 to 1.0.
It is preferable that the length in the longitudinal direction of the protrusion is approximately 1 to 5 mm. Therefore, the depth and length of the recess 10 provided in the bottom part of the groove 8 should also be determined by the inner protrusion having such a height and length. It is desirable that the dimensions be sufficient to obtain 6. Furthermore, if the amount of protrusion of the inner surface protrusions 6 from the inner circumferential surface of the pipe becomes too large, the pressure loss (head loss) of the heat transfer fluid flowing through the pipe becomes large. etc., should be determined appropriately to avoid causing too large a pressure loss. In the case of a heat transfer tube having such an inner surface protrusion 6, turbulence occurs in the flow of the heat transfer fluid flowing through the tube when it passes over the inner surface protrusion 6. The flow of the heat transfer fluid flowing in the tube axial direction along the inner surface of the tube is divided to the left and right, and in addition to this, the spiral flow effect of the heat transfer fluid near the inner surface of the tube due to the spiral arrangement of the inner surface protrusions 6 is combined. As a result, the flow on the inner surface of the pipe takes on a complex and subtle turbulent flow, which effectively destroys the film that tends to form near the inner peripheral surface of the pipe, effectively increasing the inner heat transfer coefficient. It will be done. Further, the fluid contact area on the inner surface of the tube is increased by the inner surface protrusion 6, and the contact area on the outer peripheral surface of the tube is also increased by the presence of the recess 10. By the way, the present invention allows the heat exchanger tube 2 as shown in FIGS. 1 and 2 to be easily manufactured according to the method shown in FIG. 3. In FIG. 3, reference numeral 12 denotes a plurality of fin-forming disks, each of which gradually increases in diameter, concentrically and integrally connected by a shaft 14 at intervals that provide the pitch of the outer fins 4; Additionally, a serrated disk 16 is mounted on the shaft 14 adjacent and concentrically to the largest diameter fin-forming disk 12. As shown in FIG. 4, for example, this serrated disk 16 is provided with serrations 18 at a predetermined pitch on its outer periphery, and the radius of the circumference drawn by the tips of the serrations 18 is equal to the radius of the fin formation. It is larger by a certain amount than the largest diameter of the disks 12. The shaft 14 to which each of the fin-forming disks 12 and the serrated disks 16 is attached corresponds to the lead angle of the outer fins 4 to be formed with respect to the center line of the raw tube 20 that provides the intended heat transfer tube. The base pipe 20 is positioned at an angle of
A plug 22 is inserted inside the fins, facing each fin-forming disc 12 but not facing the serrated disc 16. In this state, the fin forming disk 12 is rotated via the shaft 14 and pressed against the outer peripheral surface of the raw tube 20, thereby gradually forming the outer surface fin 1.
4 is rolled and formed while the fin forming disk 12
By the serrated disk 16 disposed downstream in the direction of outer fin formation indicated by the arrow,
By pressing the sawtooth 18 of the sawtooth disk 16 against the bottom of the groove 8 between the outer fins 4 formed, the pressed portion by the sawtooth 18 is made to protrude to the inner surface of the tube. As a result, a recess 10 is formed at the bottom of the groove 8 between the outer fins 4 on the outer peripheral surface of the tube, and the recess 1
An inner surface protrusion 6 is formed on the inner circumferential surface of the tube at a position corresponding to 0. The arrangement form of the inner surface protrusions 6 formed on the inner circumferential surface of the pipe is determined by the pitch of the sawteeth 18 with respect to the diameter of the raw pipe 20. For example, when the sawtooth pitch is small as shown in FIG. If the serrated disk 16 is used, the inner surface protrusions 6 in the arrangement shown in FIG. 2 can be easily formed, and the fifth
If a serrated disk 28 with a large serration pitch as shown in the figure is used, the inner surface protrusions 6 will be formed in the arrangement shown in FIG. 1, for example. By the way, the heat exchanger tube 2 shown in FIGS. 1 and 2
If the heat transfer tube 26 is not provided with the outer surface fins 4 continuous in a spiral shape as shown in FIG. 6, but the outer surface fins 4 are formed with cuts 24 as shown in FIG. is valid. That is, although not shown, the heat exchanger tube 26 has grooves 8 between the outer surface fins 4 like the heat exchanger tube 2 described above.
By forming the recess 10 in the bottom part of the
Although a plurality of inner protrusions 6 are formed on the inner surface of the tube,
Further, the spiral outer surface fin 4 is cut out with notches 24 spaced at predetermined intervals along its length,
They are being divided. Such depth of cut 2
The fins 4 can be provided in a spiral shape spanning between adjacent outer surface fins 4 with respect to the tube axis of the heat transfer tube 26, or can be provided in a straight line, or can be provided in a staggered manner so as to be staggered. You can also do that. In any case, by dividing the outer surface fins 4 by these cuts 24, in addition to improving the inner heat transfer coefficient based on the turbulence-inducing effect of the inner surface protrusions 6, the outer surface fins 4 are brought into contact with the outer surface of the heat exchanger tube 26. Since the heat transfer fluid is brought into effective contact with the outer surface fins 4 through the notches 24, and the notches 24 also contribute to increasing the contact area, the outer surface heat transfer coefficient is also effectively increased. In order to manufacture such a heat exchanger tube 26, for example, in FIG.
A notch forming disk is arranged further downstream of 6,
Following the rolling of the outer fins 4, cuts 24 can be formed at predetermined pitches. Further, in a separate process, a knurling roller is pressed against the outer periphery of the outer fins 4 of the heat exchanger tube in which the outer fins 4 and the inner protrusions 6 are formed as described above.
It is also possible to form such a cut 24.
Even if such a knurling tool is used, it is possible to make a sufficient depth of cut 24 on the outer fin 4. For example, for an outer fin with a height of about 1.5 mm, it is possible to make a cut 24 with a sufficient depth of about 0.8 mm. It is possible to make deep cuts. Next, in order to compare the heat transfer performance of the heat transfer tube obtained according to the method of the present invention with that of a conventional heat transfer tube, the results of experiments conducted on each sample tube are shown below. Shown in Table 1. In addition, as sample tubes, conventional tubes A, B, C,
D, H and pipes E, F, and G manufactured according to the present invention were selected, and their structures were as follows. Conventional pipe A; fin height: 1.2 mm, average groove width: 0.8 mm, outer surface fins are formed with 19 ridges/inch, and a rib-forming disk pressed against the tube outer surface with a lead angle different from that of the outer surface fins. The inner surface of the tube is provided with an inner rib having a chevron-shaped cross section and having a height of 0.5 mm, which is spirally formed at a pitch of 9.7 mm in the tube axis direction (see Japanese Patent Laid-Open Publication No. 157369/1983). Conventional B: Fin height: 1.1 mm, average groove width: 0.35 mm, the outer fins are formed with 40 ridges/inch, and at the same time, the grooved die inserted into the inner surface of the tube allows the tube axis to be fixed without crushing the outer fins. Equipped with internal ribs of a trapezoidal cross section (upper width: 1 mm, lower width: 1.8 mm) with a height of 0.4 mm and a spiral shape with a pitch of 6 mm in the direction (Special Publications Showa 52-
(See Publication No. 11670). Conventional pipe C; fin height: 1.2 mm, average groove width: 0.35 mm, outer surface fins are formed with 40 ridges/inch, and inner ribs have a chevron cross-sectional shape (height: 0.5 mm) similar to conventional pipe A. is provided in a spiral shape (pitch: 10 mm) in the tube axis direction (see Japanese Patent Laid-Open No. 157369/1983). Conventional pipe D; fin height: 0.9 mm, average groove width: 0.3 mm, outer surface fins are formed with 40 ridges/inch, and the same height as conventional pipe B: 0.4
Trapezoidal cross section of mm (upper width: 1 mm, lower width: 1.8
mm) inner ribs are provided in a spiral shape (pitch: 6 mm) in the tube axis direction, and triangular notches with a pitch of 0.3 mm and a depth of 0.3 mm are further formed on the outer surface fins. Pipe E manufactured by the present invention; fin height: 1.0 mm, average groove width: 0.8 mm, outer surface fins are formed with 19 ridges/inch, and along the spiral shape of the groove, approximately
Multiple elliptical hills formed on the inner surface of the tube with a pitch of 5.6 mm (length: 1 mm, width: 0.5 mm, height: 0.3
mm), and a triangular cut with a pitch of 1.1 mm and a depth of 0.7 mm is added to the outer fin. Pipe F manufactured by the present invention: fin height: 1.0 mm, average groove width: 0.6 mm, outer surface fins are formed with 26 ridges/inch, and along the spiral shape of the groove, approximately
Multiple elliptical hills formed on the inner surface of the tube with a pitch of 5.6 mm (length: 0.9 mm, width: 0.4 mm, height: 0.2
mm), and a triangular cut with a pitch of 1.1 mm and a depth of 0.7 mm is added to the outer fin. Pipe G manufactured by the present invention; fin height: 1.1 mm, average groove width: 0.8 mm, outer surface fins are formed with 19 ridges/inch, and a plurality of inner protrusions similar to the pipe E manufactured by the present invention are provided on the inner surface of the tube. have In short, the inner surface is the same as the tube E manufactured by the present invention, but the outer surface fins are not cut. Conventional pipe H; fin height: 1.2mm, average groove width: 0.8mm
, a basic tube whose outer surface fins are formed with 19 threads/inch. No inner protrusions are provided. The outer diameter and inner diameter of each sample tube are also listed in Table 1.

[Table] However, in Table 1, hi; tube inner surface heat transfer coefficient ho; tube outer surface heat transfer coefficient Kt; sample tube heat transfer coefficient Ks; /inch, and the heat transfer rate of a conventional loaf-in tube with a smooth inner surface This is the value when a condensable gas is brought into contact. As is clear from the test results shown in Table 1, sample tubes E, obtained according to the method of the present invention,
In F, high values are obtained for both hi and ho, and Kt/Ks, which is a guideline for transmission performance, is lower than that of conventional pipe A.
It is understood that all of the values are higher than those of ~D and H. Furthermore, the difference between the conventional tube A and the tube G manufactured by the present invention is that in the conventional tube A, spiral processing was applied from the outside to promote heat transfer on the inside.
As a result, the fins on the outer surface are crushed to a considerable extent, and the heat transfer on the outer surface is reduced, as is clear from the comparison with conventional pipe H (Table 1).
The pipe G manufactured according to the present invention has higher performance than the conventional pipe A because its outer surface fins are not crushed. However, since the pipe G manufactured by the present invention does not have any cuts in the fins on the outer surface, it is recognized that it is inferior to the pipe E manufactured by the present invention, which has the same number of fins on the outer surface (19 fins/inch). Although the present invention has been explained in detail above based on specific examples and experimental data, the present invention should not be construed as being limited by such specific examples and experimental data, and various modifications may be made based on the knowledge of those skilled in the art. It goes without saying that the present invention can be implemented with other changes, improvements, etc.

[Brief explanation of drawings]

1 and 2 are partially cutaway front views showing different specific examples of heat exchanger tubes obtained according to the method of the present invention, and FIG. 3 is a front view of the method of the present invention for manufacturing such heat exchanger tubes. FIG. 2 is an explanatory diagram showing one specific example. 4 is a front view of the serrated disk used in FIG. 3, and FIG. 5 is a partial front view showing still another specific example of the serrated disk. Moreover, FIG. 6 is a partially enlarged view showing a main part of a specific example of another type of heat exchanger tube obtained according to the method of the present invention. 2: heat exchanger tube, 4: outer surface fin, 6: inner surface protrusion,
8: groove, 10: recess, 12: fin-forming disk, 16: sawtooth disk, 18: sawtooth, 20:
Base pipe, 22: Plug, 24: Notch.

Claims (1)

[Scope of Claims] 1. By pressing the fin forming disk 12 against the outer circumferential surface of the raw tube 20 that provides the intended heat transfer tube, the outer surface fins 4 of a predetermined height are formed in a spiral shape. A serrated disk 16 having serrations 18 provided at predetermined intervals on the outer periphery on the downstream side in the fin forming direction on the outer surface of the fin forming disk.
The serrated disc 16 is arranged such that its rotation axis is positioned at an angle corresponding to the lead angle of the outer fin with respect to the center line of the blank pipe.
is rotated along the groove 8 between the outer surface fins formed, and the sawtooth 18 of the serrated disk 16 is pressed against the bottom of the groove between the outer surface fins, so that the pressed portion by the sawtooth is pressed against the inner surface of the tube. A method for manufacturing a heat exchanger tube, characterized in that the tube is made to protrude (6). 2. By pressing the fin forming disk 12 against the outer circumferential surface of the raw tube 20 that provides the desired heat transfer tube, the outer surface fins 4 of a predetermined height are spirally rolled, while the outer surface fins of the fin forming disk are rolled. A serrated disk 16 having saw teeth 18 provided at predetermined intervals on the outer periphery on the downstream side in the forming direction.
The serrated disc 16 is arranged such that its rotation axis is positioned at an angle corresponding to the lead angle of the outer fin with respect to the center line of the blank pipe.
is rotated along the groove 8 between the outer surface fins formed, and the sawtooth 18 of the serrated disk 16 is pressed against the bottom of the groove between the outer surface fins, so that the pressed portion by the sawtooth is pressed against the inner surface of the tube. A method for manufacturing a heat exchanger tube, characterized in that the external fins 4 are made to protrude (6), and cuts 24 are added at predetermined intervals in the longitudinal direction of the rolled external fins 4.