JP2011106746A - Heat transfer tube, heat exchanger, and processed product of heat transfer tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat transfer tube with high heat exchange rate compared with the one having a constant depth of a corrugated groove, and reducing a pressure loss, and also to provide a heat exchanger, and a processed product of the heat transfer tube. <P>SOLUTION: The heat transfer tube 1 includes: a main tube 2 having an inner peripheral surface 2a and an outer peripheral surface 2b; and spiral convex parts 31 formed on the inner peripheral surface 2a of the main tube 2 by forming the spiral corrugated grooves 3 on the outer peripheral surface 2b. The inner peripheral surface 2a of the main tube 2 has an area where the heights of the convex parts 31 periodically change. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a heat transfer tube, a heat exchanger, and a heat transfer tube processed product.

  Natural refrigerant heat pump water heaters typified by water-refrigerant heat exchangers boil hot water mainly at night, etc., and the flow rate of water is small, and the flow classification is laminar as a whole. . In order to improve the performance of the heat exchanger under such conditions, it is essential to improve the heat transfer performance of the water pipe. There exists a corrugated pipe | tube as a heat exchanger tube corresponding to this (for example, refer patent document 1).

  The heat transfer tube described in Patent Document 1 is a heat transfer tube having a main tube, a corrugated groove formed on the inner peripheral surface of the main tube having a constant depth formed on the outer peripheral surface of the main tube, and a convex portion formed by the corrugated groove. Are listed.

JP 2007-218486 A

  However, although the heat transfer tube described in Patent Document 1 can improve the performance of heat exchange by using a tube having a deep corrugated groove depth, when trying to obtain a higher performance, the corrugated depth If the depth is further increased, the pressure loss increases. On the other hand, if the corrugated groove depth is reduced to reduce the pressure loss, the heat exchange rate cannot be improved.

  Accordingly, an object of the present invention is to provide a heat transfer tube, a heat exchanger, and a heat transfer tube processed product that have a high heat exchange rate and can reduce pressure loss as compared with a corrugated groove having a constant depth. There is to do.

  In order to achieve the above object, the present invention provides a main pipe having an inner peripheral surface and an outer peripheral surface, and a spiral convex portion formed on the inner peripheral surface by forming a corrugated groove provided in a spiral shape on the outer peripheral surface. The inner peripheral surface of the main tube provides a heat transfer tube having a region where the height of the convex portion is periodically changed.

  The heat transfer tube may be a heat transfer tube formed such that the maximum height and the minimum height of the convex portions on the inner peripheral surface appear every round.

  Further, in addition to the heat transfer tube, the heat transfer tube disposed so that the maximum height portion of the convex portion is positioned in the direction of gravity than the minimum height portion, and the portion of the maximum height of the convex portion It is also possible to provide a heat exchanger that includes a refrigerant pipe disposed in the heat transfer pipe.

  Furthermore, the heat transfer tube disposed so that the maximum height portion of the convex portion is positioned in the direction of gravity more than the minimum height portion, and the outer peripheral surface portion corresponding to the maximum height portion of the convex portion It is also possible to provide a heat exchanger provided with a refrigerant pipe.

  In addition, the radius of curvature of the outer peripheral surface on the side where the minimum height portion of the convex portion is formed is made smaller than the outer peripheral surface on the side where the maximum height portion of the convex portion is formed in the heat transfer tube. It is also possible to provide a heat transfer tube processed product that has been bent into a bent shape.

  According to each of the above configurations, heat transfer performance is improved at locations where the height of the convex portion due to the corrugated groove is high, while pressure loss is reduced at locations where the height of the convex portion due to the corrugated groove is low it can.

  According to the present invention, the heat exchange rate is high and the pressure loss can be reduced compared to a corrugated groove having a constant depth.

FIG. 1 is a longitudinal sectional view of a heat transfer tube according to the first embodiment of the present invention. FIG. 2 shows an example of a method for manufacturing a heat transfer tube according to the first embodiment of the present invention, in which (a) is a first manufacturing method, (b) is a second manufacturing method, and (c) to (c) e) is a diagram showing a disk used in the third manufacturing method. FIG. 3A is a view showing a heat pump type water heater to which a heat exchanger according to the second embodiment of the present invention is applied, and FIG. 3B is a longitudinal sectional view of the heat exchanger 10. FIG. 4 is a schematic diagram of a heat exchanger 10 according to the third embodiment of the present invention. FIG. 5A is a longitudinal sectional view of the heat transfer tube 1 according to the fourth embodiment of the present invention, and FIG. 5B is a longitudinal sectional view of the heat transfer tube processed product 4.

[First Embodiment]
FIG. 1: shows the outline | summary of the longitudinal cross-section of the heat exchanger tube which concerns on the 1st Embodiment of this invention. The heat transfer tube 1 includes a main tube 2 having an inner peripheral surface 2a and an outer peripheral surface 2b, and a helical convex formed on the inner peripheral surface 2a of the main tube 2 by forming a spiral corrugated groove 3 on the outer peripheral surface 2b. The inner peripheral surface 2a of the main pipe 2 has a region where the height of the convex portion 31 is periodically changed.

  Note that “the height of the convex portion changes periodically” means that the position of the maximum height and the position of the minimum height (including zero) appear periodically along the convex portion. For example, the maximum value may appear every n (n is an integer). In this embodiment, n = 1.

  The “region in which the height of the convex portion periodically changes” may be provided over the entire length, but may be provided in a portion excluding both ends, or may be provided in a plurality of locations. . In this embodiment, it is provided over the entire length.

  In the present embodiment, the location where the height of the convex portion 31 by the corrugated groove 3 is the highest, the maximum height portion 31a (hereinafter, referred to as the maximum height portion 31a of the convex portion 31 or simply the maximum height portion 31a). Periodically exists, and this height is defined as Hc1. The corrugated groove 3 on the outer peripheral surface 2b corresponding to this portion is deep.

  On the other hand, the place where the height of the convex part 31 by the corrugated groove 3 is the lowest, the minimum height part 31b (hereinafter referred to as the minimum height part 31b of the convex part 31 or simply the minimum height part 31b) periodically. It exists and this height is designated as Hc2. The corrugated groove 3 on the outer peripheral surface 2b corresponding to this portion is shallow.

  The maximum height Hc1 and the minimum height Hc2 are defined by the height from the inner peripheral surface 2a of the main pipe 2, and the thickness of the main pipe 2 (hereinafter also referred to as the bottom wall thickness Tw) is not considered. Shall.

  The minimum height Hc2 can be set to 0 to 0.1 mm according to the outer pipe OD of the main pipe 2, the bottom wall thickness Tw, the assumed flow state, and the required reduction rate of pressure loss. Similarly, the maximum height Hc1 can be set to 0.3 to 0.5 mm. Further, the ratio Hc2 / Hc1 between Hc2 and Hc1 can be set to 0 to 0.2.

  The ratio Hc1 / OD between the maximum height Hc1 and the outer diameter OD of the main pipe is set to 0.03 to 0.06, and the ratio Hc2 / OD between the minimum height Hc2 and the outer diameter OD of the main pipe is set to 0 to 0.00. 02.

  In FIG. 1, when the height of the convex portion 31 at a location parallel to the axis on the inner peripheral surface 2a of the main tube 2 does not change, that is, the cross section of the main tube 2 is set so that the maximum height Hc1 of the convex portion 31 appears. The corrugated grooves 3 are periodically formed in the main pipe 2 so that the same place is always the highest when a plurality of pieces are cut. The convex portion 31 formed by the corrugated groove 3 gradually changes from the maximum height Hc1 to the minimum height Hc2.

  As an example of specific dimensions of the present embodiment, the outer diameter OD of the main pipe 2 is 9.53 mm, the bottom wall thickness Tw of the main pipe 2 is 0.7 mm, the maximum height Hc1 is 0.5 mm, and the minimum height Hc2 is 0.1 mm.

  In the present embodiment, the height of the convex portion 31 formed in a spiral shape between the maximum height portion 31a having the maximum height Hc1 and the minimum height portion 31b having the minimum height Hc2 is continuous. Although a shape that is reduced or continuously increased is employed, the height may be increased or decreased within the range of the height between Hc1 and Hc2. For example, a plurality of relatively high places may be formed around the maximum height portion 31a having the maximum height Hc1 for the purpose of further improving the heat exchange rate.

  Further, the period in which the maximum height Hc1 and the minimum height Hc2 appear may be different. For example, Hc1 may be twice the period of Hc2, and the height Hc3 of the convex portion located in the middle between adjacent Hc1s may be such that Hc1> Hc3 ≧ Hc2.

(Material of heat transfer tube 1)
The heat transfer tube 1 is made of a material having good heat transfer properties. For example, it can be formed from a metal such as copper, copper alloy, aluminum or aluminum alloy.

(Production method)
FIG. 2 shows an example of a method for manufacturing the heat transfer tube 1.

(First manufacturing method)
As a first manufacturing method, as shown in FIG. 2 (a), the corrugated groove 3 is formed by cutting the corrugated disk-like disk 5 perpendicularly to the smooth tube, that is, the tube axis. Revolving around the main pipe 2 while being rotated while being continuously pressed against the main pipe 2 in a state inclined with respect to a direction perpendicular to the central axis 20 of the main pipe 2 made of a pipe having a circular cross section on the peripheral surface. Then, the main pipe 2 can be formed by pulling out at a predetermined speed.

  That is, the center 50 of the disc-shaped disk 5 for forming a corrugate is used as the disk rotating shaft 51, and the corrugated groove 3 is formed as described above while changing the distance 52 between the rotating shaft 51 and the center axis 20 of the main pipe. Thereby, the heat exchanger tube 1 from which the height of the convex part 31 changed can be formed.

  Here, the diameter and inclination angle of the disk 5 may be determined from the drawing speed of the main pipe 2, the outer diameter OD of the main pipe 2, the distance 52 between the rotary shaft 51 and the central axis 20, and the desired corrugated groove pitch Pd.

(Second manufacturing method)
In the second manufacturing method, as shown in FIG. 2B, the rotation shaft 51 of the corrugating disk 5 is shifted from the center 50 of the disk, and the distance 52 between the rotation shaft 51 and the center axis 20 of the main pipe 2 is shifted. While maintaining a constant angle, the main pipe 2 is rotated around the main pipe 2 while being continuously pressed against the main pipe 2 while being inclined with respect to the direction perpendicular to the central axis 20 of the main pipe 2, and the main pipe 2 is revolved. It can be formed by pulling out at a speed of.

(Third production method)
The third manufacturing method is a method using a disk 5 having a shape other than a perfect circle. For example, as shown in FIG. 2 (c), using an elliptical disk in which the distance that goes around the outer peripheral surface 2b of the main pipe 2 and half of the circumference of the disk are equal, the rotation axis 51 and the central axis of the main pipe 2 are used. While maintaining a constant distance 52 from 20, while being inclined with respect to a direction perpendicular to the central axis 20 of the main pipe 2, it is rotated around the main pipe 2 while being rotated while being continuously pressed against the main pipe 2. It can be formed by pulling out the main pipe 2 at a predetermined speed.

  Further, as shown in FIG. 2D, a distance 52 from the rotary shaft 51 and the central axis 20 of the main pipe 2 is obtained by using a disk 5 having a part of the corrugated disk 5 shorter than the disk reference radius 53. While maintaining a constant angle, the main pipe 2 is rotated around the main pipe 2 while being continuously pressed against the main pipe 2 while being inclined with respect to the direction perpendicular to the central axis 20 of the main pipe 2, and the main pipe 2 is revolved. It can be formed by pulling out at a speed of.

  Conversely, as shown in FIG. 2 (e), a part of the corrugated disk 5 is formed from the rotating shaft 51 and the central axis 20 of the main pipe 2 by using the disk 5 formed so as to be longer than the disk reference radius 53. While maintaining the distance 52 of the main pipe 2 constant, the main pipe 2 is rotated around the main pipe 2 while being rotated while being continuously pressed against the direction perpendicular to the central axis 20 of the main pipe 2. It can also be formed by pulling out 2 at a predetermined speed.

  It is also possible to form a combination of the above methods. For example, the processing pattern can be made more flexible by combining the first manufacturing method and the second manufacturing method.

(Effect of this embodiment)
In the portion where the height of the convex portion 31 is high, that is, around the maximum height portion 31a having the maximum height Hc1, the agitation of water becomes large and heat transfer can be improved, while the height of the convex portion 31 is low. In the vicinity of the portion, that is, the maximum height portion 31b having the minimum height Hc2, an increase in pressure loss can be minimized.

  Furthermore, when the flow rate is small and used in the vicinity of a laminar flow (for example, Reynolds number of 5000 or less), an improvement in heat transfer coefficient due to the leading edge effect can be expected.

[Second Embodiment]
Fig.3 (a) shows the structure of the heat pump type water heater to which the heat exchanger according to the second embodiment of the present invention is applied.

(Constitution)
The heat pump type hot water heater 100 has a heat exchanger 10 using the heat transfer tube 1 according to the first embodiment, and in this heat exchanger 10, the heat from the refrigerant tube 11 is transferred to water. It is a device which supplies. The low-temperature and high-pressure refrigerant deprived of heat in the heat exchanger 10 passes through the pipe 13 in a low-temperature and low-pressure state in the decompressor 12 and becomes a high-temperature and low-pressure state in the heat absorber 14. It returns to the heat exchanger 10 again.

  FIG.3 (b) shows an example of the heat exchanger 10 of Fig.3 (a). The heat exchanger 10 includes the heat transfer pipe 1 in which the corrugated groove 3 is formed such that the maximum height Hc1 and the minimum height Hc2 of the convex portion 31 of the inner peripheral surface 2a of the main pipe 2 appear every round, that is, the inner circumference of the main pipe 2 A refrigerant pipe 11 through which a refrigerant passes is arranged inside the heat transfer pipe 1 in which the corrugated groove 3 is formed so that the height of the convex portion 31 at a location parallel to the axis on the surface 2a does not change. .

  As the refrigerant tube 11, a smooth tube or an internally grooved tube using a material having good thermal conductivity such as copper can be used. Furthermore, it is also possible to use a pipe having a function of detecting leakage of refrigeration oil circulating with the refrigerant and refrigerant in the refrigerant pipe 11. For example, the refrigerant | coolant pipe | tube 11 which provided the some leak detection path in the thickness part of a smooth pipe or an inner surface grooved pipe | tube can be used. In general, in the case where safety is required for the water flowing in the heat transfer tube 1, this structure is more specifically refrigerated into the heat transfer tube 1 together with the refrigerant in the refrigerant tube 11 and the refrigerant. Used when machine oil is not allowed to leak.

  Further, in the heat transfer tube 1, the maximum height portion 31a having the maximum height Hc1 is located at the lowest portion, that is, faces the direction of gravity. Further, a refrigerant pipe 11 is inserted into the heat transfer pipe 1 as an inner pipe. At this time, the refrigerant tube 11 is disposed in the heat transfer tube 1 so that the lower portion thereof is in contact. The heat transfer tube 1 and the refrigerant tube 11 are fixed by brazing at both ends.

  In other words, the refrigerant tube 11 is in contact with the heat transfer tube 1 inside the heat transfer tube 1 below the cross section, and the contact on the heat transfer tube 1 side is the maximum height portion 31a having the maximum height Hc1. Fixed.

(Operation of heat exchanger)
A refrigerant is caused to flow through the refrigerant pipe 11 which is an inner pipe, and water is caused to flow into a space formed by the heat transfer pipe 1 which is an outer pipe and the outer wall of the refrigerant pipe 11. Since the distance between the inner peripheral surface 2a and the refrigerant pipe 11 is close to the lower side in the heat transfer pipe 1 (that is, in the direction of gravity), it greatly contributes to heat exchange between the water in the main pipe 2 and the refrigerant in the refrigerant pipe 11. In this portion, since the height of the convex portion 31 is high (around the maximum height portion 31a having the maximum height Hc1), the water is well stirred and combined with the effect of the arrangement of the refrigerant pipe, heat exchange is performed. The rate can be kept even higher.

  On the other hand, since the distance between the upper portion in the heat transfer tube 1 and the refrigerant tube 11 is farther than the distance between the lower portion in the heat transfer tube 1 and the refrigerant tube 11, the ratio contributing to heat exchange is small. For this reason, pressure loss is reduced by making the height of the convex portion 31 lower than the convex portion 31 below the heat transfer tube.

(Effect of this embodiment)
As described above, the heat transfer tube 1 can improve the heat transfer rate from the liquid flowing in the tube to the tube as compared with a smooth tube or a tube having a constant height of the convex portion due to the corrugated groove. In particular, the performance improvement is remarkable when the flow rate is small like a water pipe of a natural refrigerant heat pump type water heater.

  Moreover, it is difficult to keep the inner tube hollow in the outer tube in a normal double tube heat exchanger arranged concentrically, and it may be positioned below the tube by gravity. At this time, there is a concern that the heat transfer tube 1 and the inner tube, which are outer tubes, come into contact with each other and hinder the flow of water, leading to a decrease in heat exchange rate and a rapid increase in pressure loss. On the other hand, according to the present embodiment, since the maximum height portion 31a having the maximum height Hc1 is formed among the convex portions 31, even if the inner peripheral surface of the inner tube and the outer tube are in contact, There is no risk of lowering the exchange rate, but rather it can be improved. For this reason, it can fix in the state which made the inner pipe (namely, refrigerant pipe 11) contact beforehand. Thereby, the fixing structure can be simplified and can be applied to a long one.

  Furthermore, by adopting such a structure, the heat transfer performance is improved below the heat transfer tube 1 and the contradictory effect of reducing the pressure loss above is succeeded. Usually, the thing with the high height of the convex part 31 by the corrugated groove | channel 3 becomes large in heat transfer performance, However, as the height of the convex part 31 by the corrugated groove | channel 3 becomes high, a pressure loss also becomes large, and heat transfer performance. Improvement in pressure and pressure loss cannot be achieved at the same time. Therefore, when the pressure loss is taken into consideration, there is a limit to the height of the convex portion 31 that can be adopted. On the other hand, when this structure is used, it is possible to improve the heat transfer performance of the portion that greatly contributes to the improvement of the heat exchanger performance, and it is possible to suppress the increase in pressure loss in the portion that does not contribute much.

  In addition, when it is strongly desired to reduce the pressure loss, there is a concern that the pressure loss may increase, for example, when the outer diameter OD cannot be increased and the bottom wall thickness Tw must be relatively large. In this case, the minimum height Hc2 at a position far from the refrigerant pipe 11 is set to zero, and the groove processing may not be performed substantially.

[Third Embodiment]
FIG. 4 shows a heat exchanger according to the third embodiment. In the heat transfer tube according to the present embodiment, the refrigerant tube 11 is adjacent not to the inside of the heat transfer tube 1 but to the outside.

  That is, the refrigerant tube 11 is provided adjacent to the outer peripheral surface 2 b below the heat transfer tube 1. The outer peripheral surface 2 b corresponding to the maximum height portion 31 a of the convex portion 31 of the heat transfer tube 1, that is, the deepest portion of the corrugated groove 3 is in contact with the refrigerant tube 11. When this structure is used, the refrigerant pipe 11 does not need to have a leakage detection path because it does not directly contact water. Therefore, a general smooth tube or an internally grooved tube can be adopted as the refrigerant tube 11, and cost reduction can be achieved.

  Here, “contacting” includes the case where the refrigerant pipe 11 is disposed via a brazing material or another highly conductive member.

[Fourth Embodiment]
FIG. 5 shows an example of a method for manufacturing a heat transfer tube processed product according to the fourth embodiment of the present invention. First, the heat transfer tube 1 in which the tube axis of the first embodiment is a straight line is formed. The heat transfer tube 1 is bent as shown in FIG. 5B to form a heat transfer tube processed product 4. In the bending process, the minimum height part 31b is formed to have a smaller radius of curvature after the bending process than the maximum height part 31a.

  By this bending process, the minimum height portion 31b on the side with the smaller curvature radius becomes higher than the minimum height Hc2, and the maximum height portion 31a on the side with the larger curvature radius becomes lower than the maximum height Hc1.

  If the heights of the convex portions after bending corresponding to the maximum height Hc1 and the minimum height Hc2 before bending are Hc3 and Hc4, respectively, the difference between Hc1 and Hc2 is larger than the difference between Hc3 and Hc4. In addition, the height of the convex portion 31 formed by the corrugated groove 3 may be changed in advance according to the distance from the center of curvature after bending. Specific values of Hc1 and Hc2 may be determined according to the radius of curvature, the outer diameter OD of the main pipe 2, and the bottom wall thickness Tw.

  Furthermore, when the heights of the protrusions after bending corresponding to the heights Hc1 and Hc2 of the protrusions before bending are Hc3 and Hc4, it is also possible to form Hc3≈Hc4.

(Effect of this embodiment)
When using a normal corrugated tube, that is, a heat transfer tube in which the height of the convex portion before bending is uniformly increased, the convex portion of the portion with a small curvature radius protrudes too much after bending, and the local Turbulence occurs. Due to this, the pressure loss increases too much. In contrast, in the heat transfer tube processed product according to the present embodiment, a portion having a small radius of curvature, that is, a convex portion on the inner side of the bending does not protrude too much.

  Moreover, when the height of the convex part before a bending process is made low uniformly, a part with a large curvature radius will become flat, and a heat exchange rate will deteriorate. On the other hand, in the heat transfer tube processed product according to the present embodiment, the portion with a large curvature radius, that is, the convex portion on the outside of the bend maintains an appropriate height, so that the heat exchange rate can be maintained high.

  Example 1 relating to the fourth embodiment will be described below. As the heat transfer tube processed product according to Example 1 and the heat transfer tube processed product according to Comparative Examples 1 and 2, heat transfer tube processed products having the configurations shown in Table 1 were produced.

  The heat transfer tube processed product 4 of Example 1 uses the heat transfer tube 1 in which the corrugated groove 3 is formed so that the heights before bending are Hc1 = 0.1 mm and Hc2 = 1.0 mm, respectively. The heat transfer tube processed product 4 is manufactured by bending so that Hc1 is on the side having a small radius and the side having a large curvature radius. At this time, the heights Hc3 and Hc4 after bending are equal at 0.5 mm.

  On the other hand, Comparative Example 1 uses a heat transfer tube in which the corrugated groove 3 is formed so that the maximum height Hc1 and the minimum height Hc2 of the convex portion before bending are matched, and is bent to produce a heat transfer tube processed product. . Further, as Comparative Example 2, a smooth tube is bent to produce a heat transfer tube processed product.

About the smooth tube ratio of heat transfer performance according to Example 1 and Comparative Example 1 in Table 1 (more precisely, the performance ratio of the heat transfer tube processed product formed from the smooth tube according to Comparative Example 2) and pressure loss, It shows in Table 2. The K value was used for the heat transfer performance.
Here, the K value represents a heat passage rate indicated by total heat conductance [W / m ² · K] per unit area. Here, the low heat transfer from the refrigerant pipe 11 to water is shown. Regarding pressure loss, an example of an absolute value is described.

  From Table 2, it can be seen that in the heat transfer tube processed product 4 of Example 1, the heat transfer performance is improved by 14% compared to the heat transfer tube processed product (Comparative Example 2) prepared from the smooth tube. On the other hand, in Comparative Example 1, the heat transfer performance was improved by 16% compared to the heat transfer tube processed product made from a smooth tube (Comparative Example 2). It was.

  On the other hand, regarding the pressure loss, the heat transfer tube processed product according to Example 1 has a result that the heat transfer tube processed product made from the smooth tube is suppressed to 5 times compared with the heat transfer tube processed product (Comparative Example 2). The result of Example 1 reaches 9 times that of the heat transfer tube processed product of Comparative Example 2.

  From the above, it can be seen that the heat transfer tube processed product of Comparative Example 1 cannot be adopted because the pressure loss is too large. On the other hand, the heat transfer tube processed product of Example 1 achieved a K value of 110% or more and a pressure loss of 35 Kpa or less, and succeeded in reducing the pressure loss while improving the heat transfer performance comprehensively. ing.

DESCRIPTION OF SYMBOLS 1 ... Heat transfer tube, 2 ... Main pipe, 2a ... Inner peripheral surface, 2b ... Outer peripheral surface, 3 ... Corrugated groove, 4 ... Heat transfer tube processed product, 5 ... Disk, 10 ... Heat exchanger, 11 ... Refrigerant tube, 12 ... Depressurization 13 ... pipe, 14 ... heat absorber, 15 ... compressor, 20 ... center axis, 31 ... convex part, 31a ... maximum height part, 31b ... minimum height part, 50 ... center of disk, 51 ... rotary axis 52 ... Distance between the rotation axis and the central axis, 53 ... Disc reference radius, 100 ... Heat pump water heater

Claims (8)

A main pipe having an inner peripheral surface and an outer peripheral surface;
A helical projection formed on the inner peripheral surface by forming a spiral corrugated groove on the outer peripheral surface;
The inner peripheral surface of the main pipe is a heat transfer pipe having a region where the height of the convex portion is periodically changed.   2. The heat transfer tube according to claim 1, wherein the maximum height and the minimum height of the convex portions on the inner peripheral surface are formed so as to appear every round.   The heat transfer tube according to claim 2, wherein a ratio Hc2 / Hc1 of the minimum height Hc2 to the maximum height Hc1 is 0 to 0.2 in the convex portion.   The ratio Hc1 / OD between the maximum height Hc1 and the outer diameter OD of the main pipe is 0.03 to 0.06, and the ratio Hc2 / OD between the minimum height Hc2 and the outer diameter OD of the main pipe is 0 to 0. The heat transfer tube according to claim 2 or 3, which is 0.02. The heat transfer tube according to claim 2, wherein the portion of the maximum height of the convex portion is disposed so as to be positioned in the direction of gravity than the portion of the minimum height.
The heat exchanger provided with the refrigerant | coolant pipe | tube arrange | positioned in the said heat exchanger tube so that the site | part of the said convex part may contact the said maximum height. The heat transfer tube according to claim 2, wherein the portion of the maximum height of the convex portion is disposed so as to be positioned in the direction of gravity than the portion of the minimum height.
A heat exchanger comprising: a refrigerant pipe disposed so as to be in contact with a portion of the outer peripheral surface corresponding to the maximum height portion of the convex portion. The heat transfer tube according to claim 2,
Bending so that the radius of curvature of the outer peripheral surface of the convex portion on the side where the minimum height portion is formed is smaller than the radius of curvature of the outer peripheral surface of the convex portion on the side where the maximum height portion is formed. Processed heat transfer tube processed product. The heat transfer tube according to claim 3 or 4,
Bending so that the radius of curvature of the outer peripheral surface of the convex portion on the side where the minimum height portion is formed is smaller than the radius of curvature of the outer peripheral surface of the convex portion on the side where the maximum height portion is formed. Processed heat transfer tube processed product.

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