JPH11183079A - Heat exchanger tube with internal groove and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a higher evaporation performance, especially n a low heat medium mass velocity area in a heat exchanger tube with an internal groove having a pine needle-shaped circumferential groove while ensuring excellent condensing performance and moreover, holding a pressure loss lower. SOLUTION: An axial groove 20 is formed in each of fin-shaped protrusions 18 on an imaginary division line while an overhung part 22 is formed axially extending the tip part of the fin-shaped protrusion 18 where the axial groove 20 is formed. A cavity 24 covered with the overhung part 22 is formed on the bottom part of the circumferential groove. A gas and steam supplemented by the cavity 24 allow the promoting of nucleus boiling thereby achieving a higher evaporation performance in a low heat medium mass velocity area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat transfer tube having an inner surface groove which is suitably used for refrigeration equipment, air conditioning equipment and the like, and a method for manufacturing the same. The present invention relates to an inner grooved heat transfer tube that can be obtained and an advantageous manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, as one type of heat exchange tubes in refrigeration equipment, air conditioning equipment, etc., Japanese Utility Model Laid-Open No. 57-183487, JP-A-9-26279, and JP-A-9-2363.
As described in Japanese Patent Application Publication No. 95-1995, the inner circumferential surface of the pipe is divided into a plurality of divided areas in the circumferential direction by virtual dividing lines extending linearly in the pipe axis direction. Fin-shaped protrusions that are inclined with respect to the axial direction and that have opposite inclination directions on both sides of the virtual dividing line are formed apart from each other in the tube axis direction, so that fin-shaped protrusions adjacent in the tube axis direction are formed. 2. Description of the Related Art There is known an inner grooved heat transfer tube in which a circumferential groove extending between the protrusions and extending in the circumferential direction of the tube is provided in a shape like a pine needle.

[0003] In such a heat transfer tube (pine tube grooved tube) having a pine needle-shaped inner surface groove, when used as a condensing tube, the tip portion of the fin-shaped projection is particularly located upstream of the flow of the heat medium. The helical groove is formed in the inner peripheral surface of the tube because the V-shaped portion is easily exposed at the abutting portion on the expanding side of the V-shape, which advantageously secures the contact area of the heat transfer gas with the metal surface of the heat transfer tube. The condensation performance can be advantageously obtained even compared to a spiral grooved tube formed with, and is attracting attention as a technique for improving the heat transfer promoting effect.

[0004] By the way, even when such a tube with a pine needle groove is used as an evaporating tube, the heat medium gas flowing through the heat transfer tube allows the heat medium liquid to be wound up along the pine needle-shaped groove so as to form an inner circumferential surface of the tube. Because of the spread, the wide area of the inner surface of the pipe is wetted and the area where boiling occurs is enlarged, so that excellent evaporation performance can be exhibited.

However, as a result of further studies by the present inventors, it has been found that the evaporation performance due to the heat transfer promoting effect as described above in the conventional pine needle grooved tube has a high heat transfer mass velocity which is a region of forced convection heat transfer. It is clear that in the low heating medium mass velocity region where nucleate boiling is dominant during evaporation, excellent evaporation performance due to the effective heat transfer promotion effect is not necessarily obtained. .

In order to improve the evaporating performance, it is conceivable to reduce the pitch of the fin-like projections in the tube axis direction, or to increase the fin-like projections to make the spiral groove deeper. In pine needle grooved pipes, compared to spiral grooved pipes, the pressure loss of the heat medium flowing through the pipes tends to increase, and when the pressure loss increases, the refrigerant temperature in the pipes increases, and a sufficient temperature difference with air can be obtained. For reasons such as disappearance, the evaporating capacity is reduced, and such a formation of a high fin or a deep groove further increases the pressure loss of the heat medium, and is not always an effective method.

[0007]

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to solve the problem while ensuring excellent condensation performance and suppressing pressure loss to a low level. , Evaporative performance can be improved,
An object of the present invention is to provide an inner grooved heat transfer tube having a pine needle-shaped inner groove.

Another object of the present invention is to provide a method of manufacturing an inner grooved heat transfer tube capable of easily manufacturing such an inner grooved heat transfer tube having the structure according to the present invention. .

[0009]

In order to solve such a problem, a feature of the present invention relating to a heat transfer tube with an inner groove is that the inner circumferential surface of the tube is formed by a virtual dividing line extending linearly in the axial direction of the tube. Is divided into multiple sub-regions by
In each of the divided regions, a large number of fin-shaped projections that are inclined with respect to the tube axis direction and are opposite in the inclination direction to each other on both sides of the virtual division line are formed apart from each other in the tube axis direction. In the heat transfer tube with an inner surface groove provided with a circumferential groove extending in the circumferential direction of the tube and located between the adjacent fin-like protrusions in the tube axial direction, the protrusion of the fin-like protrusion is formed on at least one of the virtual dividing lines. An axial groove having a reduced height and extending in the pipe axis direction on the virtual dividing line is formed, and the circumferential portion is formed with respect to a tip end portion of the fin-shaped projection having a low protruding height forming the axial groove. An overhang portion projecting in the pipe axis direction toward the direction groove is provided integrally,
A cavity covered by the overhang is formed at the bottom of the circumferential groove.

[0010] In the heat transfer tube with an inner surface groove having the structure according to the present invention, a configuration in which the fin-like projection and the circumferential groove are formed in a continuous annular shape in the circumferential direction is preferably adopted. .

Furthermore, in order to solve the above-mentioned problems, a feature of the present invention relating to a method of manufacturing a heat transfer tube having an inner surface groove is that one side of the heat transfer tube material in the form of a strip has a plate length. In a plurality of divided areas divided by virtual dividing lines extending linearly in the direction, fin-shaped projections that are inclined with respect to the plate longitudinal direction and whose inclination directions are opposite to each other on both sides of the virtual dividing line, After forming a large number in the longitudinal direction, the heat transfer tube material is curved in the plate width direction, and both side edges in the plate width direction are butt-joined to each other, so that the fin-shaped projections adjacent in the tube axis direction are formed. When manufacturing a heat transfer tube with an inner surface groove having a circumferential groove extending in the circumferential direction of the tube and located between the heat transfer tube material, after forming the plurality of fin-like projections on the heat transfer tube material, On the dividing line, The inner groove obtained by crushing the tip of each fin-like projection to lower the projection height of the fin-like projection and projecting the projection tip of the fin-like projection on the virtual dividing line. In the heat transfer tube, an axial groove extending in the axial direction of the tube is formed by a crushed portion of the fin-shaped protrusion, and the circumferential groove is covered by the protrusion of the fin-shaped protrusion by covering the circumferential groove. Is to form an overhang portion that forms a cavity at the bottom.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, in order to make the present invention clearer, embodiments of the present invention will be described in detail with reference to the drawings.

First, FIG. 1 is a plan view of a heat transfer tube 10 having an inner surface groove according to a first embodiment of the present invention, which is cut open along a cutting surface in the tube axis direction and is developed into a flat plate shape. 2 and 3 show such a heat transfer tube 10 having an inner groove.
A plan view and a vertical cross-sectional view showing an enlarged main part of FIG. The inner grooved heat transfer tube 10 is employed as a condensation tube, an evaporation tube, a heat pipe body, or the like.
It has an appropriate hollow tube structure such as a circular tube cross-section, an elliptical tube cross-section, and a flat tube cross-section so that a closed heat medium flow path can be formed inside. An appropriate metal material such as copper, a copper alloy, or an aluminum alloy is selected as the material according to the employed heat medium or the like.

The inner grooved heat transfer tube 10 has a smooth outer peripheral surface, and a plurality of pine needle-shaped circumferential grooves 12 formed on the inner peripheral surface. More specifically, the inner peripheral surface of the heat transfer tube 10 with the inner surface groove is divided into four divided portions located at every 90 degrees in the circumferential direction by four virtual dividing lines 14a, 14b, 14c, and 14d extending in the tube axis direction. Area 1
6a, 16b, 16c and 16d. In each of these four divided regions 16a to 16d, a large number of inclined regions extending in the circumferential direction of the tube are inclined in directions in which the inclination angles with respect to the tube axis direction are opposite to each other across the virtual dividing lines 14a to 14d. A large number of fin-like projections 18 are formed in the tube axis direction and are separated from each other by a substantially constant distance. Further, thereby, each of the four divided areas 16a to 16d has a fin-shaped projection 18 adjacent to each other in the pipe axis direction.
A circumferential groove 12 extending inclining in the pipe circumferential direction is formed.

In particular, in this embodiment, a large number of fin projections 18 formed in each of the four divided regions 16a to 16d are parallel in each divided region 16, and the four divided regions 16a , The two ends located on the virtual dividing lines 14a to 14d on both sides in the circumferential direction are continuously connected to the fin strip projections 18 adjacent in the circumferential direction. Thereby, each of the four divided areas 16a-
d, a large number of fin projections 18 and a circumferential groove 12 formed between the fin-like projections 18,
Each of them is formed in a continuous annular shape so that the inner circumferential surface of the pipe extends in a zigzag shape in the circumferential direction. In short, each of the fin-shaped protrusions 18 and each of the circumferential grooves 12 have a V-shaped or inverted V-shaped bent point on each of the virtual dividing lines 14a to 14d, and the large number of such circumferential grooves. Reference numeral 12 denotes an annular closed channel which is independent of each other, and has a pine needle shape as a whole.

The fin-like projections 18 and the circumferential grooves 1
2 and the fin-like projection 18
And the cross-sectional shape and pitch of the circumferential groove 12 are all
It is appropriately determined according to the use of the heat transfer tube, the type of the heat medium to be adopted, the mass velocity of the heat medium circulated in the tube, and the like, and is not limited. In the present embodiment, the fin-shaped protrusion 18 is formed with a trapezoidal cross-section that becomes narrower toward the tip, and the circumferential groove 12 is formed on the opening side. It has an inverted trapezoidal cross section that expands toward the front. Further, the protrusion height of the fin-like projections 18, in other words, the depth of the circumferential groove 12: d, is preferably 0.05 ≦ 2 d / with respect to the maximum inner diameter dimension D of the heat transfer tube 10.
It is set so that D ≦ 0.087. Further, the pitch P between the fin-like projections 18 and the circumferential grooves 12 is preferably 0.35 to 0.5 mm in the circumferential direction of the heat transfer tube 10.
Set to about. Further, the inclination angle θ of the fin-like projections 18 and the circumferential grooves 12 with respect to the tube axis direction is preferably set to satisfy 5 ° ≦ θ ≦ 45 °. By adopting such set values, the effect of increasing the heat transfer area by the pine needle-shaped fin-shaped protrusions 18 and the circumferential grooves 12 and the effect of improving the heat transfer performance based on the guide action to the heat transfer liquid and the like are more advantageous. It can be demonstrated.

Further, as described above, a large number of fin-like projections 1 are provided.
8 has a lower protruding height at a portion located on each of the virtual dividing lines 14a to 14d, so that the tube extends across all the fin-like projections 18 located on the virtual dividing lines 14a to 14d. Axial groove 20a extending in the axial direction
d is formed. That is, each of these axial grooves 20a-
d is such that a number of circumferential grooves 12 formed between the fin-like projections 18 are communicated with each other,
It is formed linearly in the tube axis direction. The cross-sectional shape of the axial groove 20 is not particularly limited. However, in the present embodiment, the effect of reducing the pressure loss of the heat medium is more effectively exhibited in consideration of manufacturability and strength. As described above, the cross section has an inverted trapezoidal shape that expands toward the protruding tip side of the fin-shaped projection 18.

In this embodiment, the fin-like projections 18 are used.
Axial grooves 20 on all the virtual dividing lines 14a to 14d
Is formed, it is sufficient that such an axial groove 20 is formed on at least one imaginary dividing line 14, whereby the effect of reducing the pressure loss of the heat medium circulated in the pipe can be exhibited. . Furthermore, the axial groove 20 is
It is not necessary to form the fin-like projections 18 located on the virtual division line 14 continuously in the tube axis direction. May be formed in a divided form.

Further, in the fin-like projection 18, the portion in which the axial groove 20 is formed and the protruding height is reduced is such that the protruding tip part constituting the bottom wall of the axial groove 20 extends in the tube axial direction. Accordingly, the overhang portion 22 projecting toward the circumferential groove 12 is formed integrally with the fin-like projection 18. Then, at the portion where the overhang portion 22 is formed, the bottom of the circumferential groove 12 is covered by the overhang portion 22, and thus the cavity 24 is formed at the bottom of the circumferential groove 12.

Here, the height of the fin-like projections 18 at the location where the axial groove 20 is formed, that is, the depth h of the circumferential groove 12 is not particularly limited, but the axial groove 20
Depth of the circumferential groove 12 at a portion where no is formed:
It is desirable to set d in a range of 0.01d ≦ h ≦ 0.1d. When 0.01d> h, it is difficult to form the cavity 24 at the bottom of the circumferential groove 12, so that an effective boiling promoting effect cannot be obtained. When h> 0.1d, the cavity 24 becomes too deep, Cavity 2
This is because the heat medium liquid can easily enter into No. 4 and the effect of accelerating boiling may not be effectively obtained.

When the overhanging tip of the overhang portion 22 reaches the fin-shaped projection 18 adjacent in the tube axis direction and the opening of the cavity 24 is completely covered, the cavity 24 is replaced with a mere gap. Because it may be difficult for the nucleate boiling promoting effect to be effectively exhibited,
It is desirable that a gap is formed between the protruding tip portion of the overhang portion 22 and the adjacent fin-shaped projection 18. Then, the gap, in other words, the opening width of the cavity 24:
It is more desirable to set w in the range of 0.002 mm ≦ w ≦ 0.2 mm. When 0.002 mm> w, the opening of the cavity 24 is substantially closed, and it is difficult to generate bubbles due to cavitation of the cavity 24 and the like, and it may be difficult to effectively obtain the nucleate boiling promoting effect. If w> 0.2 mm, the opening of the cavity 24 is too wide, and the heating medium liquid fills the cavity 24, so that bubbles are unlikely to be generated, and the effect of promoting boiling may not be effectively obtained. Because.

Thus, the heat transfer tube 10 having the inner surface groove having such a structure is assembled to the heat exchanger in the same manner as the conventional heat transfer tube. The condenser and the evaporator are configured by being installed in a horizontal direction with the pipes being mounted on and the like.

Here, in the heat transfer tube 10 with the inner surface groove as described above, the guide action of the heat medium and the like by the large number of pine needle-shaped circumferential grooves 12 formed on the inner surface of the tube are exhibited, so that the conventional heat transfer tube 10 has the conventional structure. Like the pine grooved tube, for example, when used as a condensing tube, the contact area of the heat transfer gas to the metal surface of the heat transfer tube is advantageously ensured, excellent condensing performance is exhibited, and the tube is used as an evaporating tube. Even in such a case, particularly in a high heat medium mass velocity region, the region where evaporation occurs is enlarged, and excellent evaporation performance is exhibited. In particular, when four or more virtual dividing lines 14 are provided and the inner peripheral surface is divided into four or more divided regions 16 as in the heat transfer tube 10 of the present embodiment, the guide by the circumferential groove 12 is used. Since a plurality of virtual dividing lines 14 in which the heat medium is collected in the circumferential direction based on the function and the like and a plurality of virtual dividing lines 14 in which the heat medium is diffused in the circumferential direction are provided, the flow direction of the heat medium is specially adjusted. Even if it is arranged without consideration, the effect of improving the heat transfer performance based on the guide action of the heat medium by the circumferential groove 12 is effectively exhibited, and the excellent heat transfer performance is stably exhibited. There is. Although it depends on the inner diameter of the heat transfer tube 10 and the like, if the virtual dividing lines 14 are set too much, the circumferential grooves 1
Since the effect of improving the heat transfer performance based on the heat medium guiding action by the heat medium 2 becomes difficult to be sufficiently exerted, the virtual dividing line 14
Is preferably 10 or less. Further, when an odd number of virtual dividing lines 14 are provided, there are divided regions 16, 16 in which the inclination direction of the fin-shaped projections is the same with respect to the tube axis on both sides of one virtual dividing line 14, As a result, the heat transfer performance may be reduced, and therefore it is desirable to provide the virtual dividing line 14 and the divided region 16 in even numbers. Furthermore, the circumferential intervals of the virtual dividing lines 14 can be made different from each other for the purpose of further improving the heat transfer performance in consideration of the direction of the heat transfer tubes 10 at the time of piping. In consideration of the above, it is preferable that the circumferential interval between the virtual dividing lines 14 be set to be substantially constant in the circumferential direction of the heat transfer tube 10.

In addition to this, the heat transfer tube 10 having the inner groove is provided.
Is located on the imaginary dividing line 14, and the circumferential groove 1
2 has a cavity 24 at the bottom,
In this cavity 24, nucleate boiling is advantageously promoted. That is, the heat medium liquid flows through the inside grooved heat transfer tube 10,
While being guided by the circumferential groove 12 along the inner peripheral surface, it is circulated in the pipe axis direction.
The cavity 24 is formed as a recessed portion that opens to the inner peripheral surface of the heat transfer tube 10 and is covered by the overhang portion 22 with respect to the flow of the heat transfer liquid, so that the inside of the cavity 24 has heat. It is difficult to be filled with the medium liquid, and gas and vapor are apt to remain trapped inside to some extent. Since it is considered that the nucleate boiling phenomenon accompanied by the generation of bubbles from the solid surface at the time of boiling depends on the gas or vapor that has existed in advance, the gas or vapor is easily captured in the cavity 24 as described above. By
In such a cavity 24, bubbles are generated at a lower degree of superheat, and nucleate boiling is advantageously generated. As a result, by promoting nucleate boiling, a good heat transfer promoting effect can be exhibited even in a low heat medium mass velocity region in which nucleate boiling is dominant in evaporation.

In addition, the cavity 24 is formed so as to be located on the virtual dividing line 14 where the flow of the heat transfer liquid tends to be in the direction of the tube axis. Since the bulge is formed in the flow direction, the gas and vapor can be more effectively captured in the cavity 24, and the effective heat transfer promoting effect can be obtained in a wider range of the low heat medium mass velocity region. It is demonstrated.

Further, in the heat transfer tube 10 having the inner surface groove having the above-described structure, the fin-shaped projection 18 is formed with the axial groove 20 extending along the virtual dividing line 14. Since the heat medium flowing through the inner circumferential surface of the tube is released in the axial direction of the tube through the groove 20, the pressure loss of the heat medium flowing through the heat transfer tube 10 can be reduced.

By the way, such a heat transfer tube 1 with an inner groove is used.
0, for example, the following manufacturing method,
It is preferably adopted.

That is, as shown in FIG. 4, a strip-shaped heat transfer tube material 30 made of a predetermined material for providing a target heat transfer tube 10 is prepared.
The sheet is passed through the rolling and tube forming device 32 in one longitudinal direction by a drive roll (not shown). Then, in the device 32, first, the heat transfer tube material 30 is pressed by a predetermined pressure with the primary grooved roll 34 and the primary support roll 36 as rolling rolls sandwiching the heat transfer tube material 30 from both sides in the plate thickness direction. Here, the primary support roll 3
The outer peripheral surface of the primary grooved roll 34 has irregularities on the outer peripheral surface of the primary grooved roll 34 corresponding to the circumferential grooves 12 formed on the inner peripheral surface of the target heat transfer tube 10. Is attached. Then, by the rolling operation using the primary grooved roll 34, as shown in FIGS. 5 to 7, a large number of fin-shaped protrusions extending in the circumferential direction and extending on one surface of the heat transfer tube material 30. The 18 and the circumferential groove 12 are formed in a pine needle-like form in which the inner surface of the target heat transfer tube 10 is developed.

In addition, the rolling and tube forming device 32 is located in front (downstream) of the primary grooved roll 34,
A secondary grooved roll 38 as a rolling roll and a secondary support roll 40 are provided, and the primary grooved roll 3 as described above is provided.
The heat transfer tube material 30 sent out from between 4 and the primary support roll 36 is subsequently fed between the secondary grooved roll 38 and the secondary support roll 40 and rolled. put it here,
The outer peripheral surface of the secondary support roll 40 is substantially smooth, but the outer peripheral surface of the secondary grooved roll 38 corresponds to the axial groove 20 formed on the inner peripheral surface of the intended heat transfer tube 10. It has irregularities in the shape of a circle. Then, by the rolling operation using the secondary grooved roll 38, as shown in FIGS. 1 to 3, the distal end portion of the fin-shaped protrusion 18 formed by the primary grooved roll 30 is transferred to the target transmission. On four virtual dividing lines (14) extending linearly in the longitudinal direction of the heat transfer tube material 30 with respect to each virtual dividing line 14 in the heat pipe 10,
Each is crushed. Thereby, each fin-like projection 1
8, an axial groove 20 extending on each imaginary dividing line is formed, and at the same time, the excess thickness of the crushed fin-like projection 18 is extended in the longitudinal direction of the heat transfer tube material 30, so that the fin-like projection 18 is formed. On the other hand, the overhang portion 22 is integrally formed.

Thereafter, the surface on which the fin-shaped protrusions 18 and the like are formed is turned inside by a plurality of rolls (not shown).
The heat transfer tube material 30 is bent in the width direction, and a pair of seam guide rolls 42, 42 are used to send out the widthwise side edges of the heat transfer tube material 30 with each other, and then, using a high-frequency induction coil (not shown) or the like, The butted portion of the heat transfer tube material 30 is continuously welded in the longitudinal direction of the heat transfer tube material 30. Furthermore, after that, after the shape is adjusted using a squeeze roll or the like as necessary, the desired inner surface groove is provided by cutting to a predetermined length as necessary or winding up in a roll shape. The heat transfer tube 10 can be obtained.

In the present embodiment, the fin-like projections 18 and the like of the heat transfer tube material 30 are formed in a form developed on one virtual dividing line 14, and are welded on the virtual dividing line 14. From that,
By the rolling operation using the secondary grooved roll 38, one virtual dividing line 14 is formed by being divided into both widthwise side edges of the heat transfer tube material 30, and the three virtual dividing lines 14 are formed.
Are formed at positions where the heat transfer tube material 30 is divided into approximately three equal parts in the width direction.

According to such a manufacturing method, the axial groove 2
0 can be easily formed and the axial grooves 20 can be formed.
The overhang portion 22 is formed at the same time as the formation of the heat transfer tube without any special operation or process. It can be manufactured with In addition, in such a manufacturing method, not only the depth and width of the axial groove 20 but also the overhang by changing the height and width of the concave and convex portions formed on the primary grooved roll 34 and the secondary grooved roll 38. There is also an advantage that the shape and size of the portion 22 can be easily adjusted.

In addition, according to this manufacturing method, the tip portion of the fin-like projection 18 formed first by the primary grooved roll is crushed at a predetermined position by the secondary grooved roll later, whereby the shaft is formed. Since the directional grooves 20 are formed, the load acting on the forming rolls during rolling can be reduced as compared with the case where the circumferential grooves 12 and the axial grooves 20 are simultaneously formed by a single grooved roll. Therefore, there is an advantage that breakage prevention of the forming roll can be advantageously achieved.

The embodiments of the present invention have been described in detail above. However, the present invention is not to be construed as being limited by the above-described specific description and the description of the following examples, and is understood by those skilled in the art. The present invention can be carried out in an embodiment in which various changes, modifications, improvements, and the like are added based on the above, and all such embodiments fall within the scope of the present invention unless departing from the gist of the present invention. It goes without saying that it is included.

For example, a large number of fin-like projections 18 do not need to be parallel to each other in each divided region 16, and the inclination angle of each fin-like projection 18 with respect to the tube axis direction is made different in one divided region 16. May be. Further, each fin-shaped projection 18 does not need to be linear when the heat transfer tube 10 is deployed, and a fin-shaped projection extending in a curved manner can be adopted. Furthermore, it is also possible to make the pitch of the fin-shaped projections 18 different in the divided regions 16, 16 adjacent in the circumferential direction with the virtual dividing line 14 interposed therebetween. Alternatively, the divided regions 16 and 1 adjacent in the circumferential direction with the virtual dividing line 14 interposed therebetween
6, the fin-like projections 18 formed at the same pitch
Are shifted from each other in the pipe axis direction, and on the virtual dividing line 14,
The ends of the fin-shaped projections 18 formed in the divided regions 16 on both sides may be alternately positioned at a predetermined distance.

It is also possible to provide a recess or a cut in the fin-shaped projection 18 in a portion other than the virtual dividing line 14.
Pressure loss can be further reduced, and the flow of the heat medium can be adjusted. Further, it is possible to form the overhang portion 22 that defines the cavity 24 at the bottom of the circumferential groove 12 not only on the virtual dividing line 14 but also in other portions.

Further, as described above, the heat transfer tube with an inner groove having the structure according to the present invention is provided with the rolling stand with the primary grooved roll 34 and the rolling stand with the secondary grooved roll 38 arranged side by side in the passing direction. It can be manufactured by various manufacturing methods in addition to the manufacturing method using a tandem one-pass rolling mill. Specifically, for example, after passing the strip-shaped heat transfer tube material 30 through a rolling mill provided with a rolling stand using a primary grooved roll 34 to form the circumferential grooves 12, the obtained heat transfer tube material is obtained. 30 with a secondary grooved roll 38
It is also possible to adopt a two-pass rolling method in which a plate is passed through a rolling mill provided with a rolling stand to form the axial groove 20 and the overhang portion 22.

[0038]

First, as shown in FIG. 8, which is an exploded view at the welding position, a large number of circumferential grooves 12 and fin-like projections 18 are formed on the inner surface of the pipe so as to extend continuously in the circumferential direction. In addition, two imaginary boundary lines 1 are configured with dimensional specifications as shown in Table 1 below.
Axial grooves 20a, 20 extending in the tube axis direction are provided for all the fin-like projections 18 located on the 4a, 14b.
An inner grooved heat transfer tube having the structure according to the present invention and formed with b was prepared as an example. In Table 1 below and Table 2 described below, the peripheral groove refers to a circumferential groove, and the axial groove refers to an axial groove. The apex angle indicates the magnitude of the apex angle of the fin-shaped projection, and the lead angle indicates the magnitude of the inclination angle of the fin-shaped projection with respect to the tube axis. Furthermore,
The number of fins indicates the number of fin-like protrusions per revolution, that is, the number of fin-like protrusions formed on the end surface in a cross section perpendicular to the tube axis.

For comparison, a large number of circumferential grooves 12 and fin-like projections 18 are formed in the same manner as in this embodiment. As shown in FIG. No fin-shaped projections are formed on the two virtual dividing lines 14a and 14b, and the bottom surface having the same height as the bottom surface of the circumferential groove 12 is provided on the virtual dividing lines 14a and 14b in the pipe axis direction. A heat transfer tube with an inner surface groove provided with a shaft groove 46 extending linearly is referred to as a comparative example 1. Further, as shown in a developed view cut out at the welding position in FIG. 10, two virtual dividing lines 14a are provided. , 14b on which the fin-like projections 18 and the circumferential groove 12 are continuous, and the heat transfer tubes with inner grooves having no axial grooves formed therein are shown in Table 1 below as dimensions of Comparative Example 2. With specifications Form was.

[0040]

Next, the prepared three types of heat transfer tubes with inner grooves (Examples and Comparative Examples 1 and 2), a heat transfer performance test device as shown in FIG. 11, and a heat transfer fluid as a heat transfer fluid. Using a fluorocarbon (R22), various heat transfer tubes are assembled in a single tube to the test section of the heat transfer performance test apparatus, and an evaporation performance test and a condensation performance test are performed under the test conditions shown in Table 2 below. Done.

[0042] *: Gauge pressure (1 MPa = 10.1978 kgf / cm ² )

As shown in FIG. 12, the direction in which the heat transfer tubes are arranged in the test section of the heat transfer performance test apparatus is such that, during the evaporation performance test, the circumferential grooves are arranged in the heat medium flow direction. On the other hand, in the condensation performance test, on the contrary, the circumferential groove was set so as to fall forward with respect to the heat medium flowing direction.
The heating medium mass speed is 250 kg / (m ² · s) as the heating medium mass speed substantially equal to the rated operating condition in the actual machine, and 150 kg as the heating medium mass speed substantially equal to the intermediate capacity operating condition in the actual machine. Each test was performed for the case where / (m ² · s) was adopted.

The experimental results under the respective mass velocity conditions of the heat medium were compared with the heat transfer in a heat transfer tube (heat transfer tube with a spiral groove) provided with a spiral circumferential groove on the inner peripheral surface, which is a mass-produced product at present. FIGS. 13 and 14 show heat transfer coefficient ratios in the three types of heat transfer tubes with internal grooves and pressure loss ratios in the tubes when the heat transfer rate and the pressure loss in the pipes are set as a reference (1).

As is clear from the results shown in FIG. 13, at a high mass flow rate of the heat medium, the heat transfer tube with the inner surface groove according to the embodiment can be used in both the evaporation performance test and the condensation performance test.
It is recognized that the pressure loss is significantly suppressed as compared with the heat transfer tube of Comparative Example 2 having no axial groove, and that the condensation performance is remarkably excellent. Also, compared with the heat transfer tube of Comparative Example 1, It is recognized that they have equal or higher evaporation performance and condensation performance.

Further, as is apparent from the results shown in FIG. 14, the heat transfer tube with the inner surface groove of the embodiment has a lower pressure than the heat transfer tube of the comparative example 2 having no axial groove at a low mass velocity of the heat medium. The heat transfer coefficient is of course equal to or higher than that of the heat transfer tubes of Comparative Examples 1 and 2, as well as the loss is largely suppressed. In particular, the evaporation performance is sufficiently higher than any of the heat transfer tubes of Comparative Examples 1 and 2. The heat transfer tubes of Comparative Examples 1 and 2 have the same performance as the conventional heat transfer tubes with spiral grooves, whereas the heat transfer tubes with inner surface grooves of the present embodiment have the conventional heat transfer tubes. It is noteworthy that a heat transfer coefficient improvement of as much as 30-40% has been achieved over the spiral grooved heat transfer tubes. From such facts, as described in detail in the above embodiment, the effect of reducing the pressure loss by the axial groove formed on the inner peripheral surface of the heat transfer tube with the inner surface groove of the example, and the bottom of the circumferential groove by the overhang portion It can be understood that the heat transfer promoting effect of the cavity formed in the hole is effectively exhibited.

[0047]

As is apparent from the above description, in the heat transfer tube with the inner surface groove having the structure according to the present invention, the heat transfer performance is improved by the pine needle-shaped circumferential grooves formed to be inclined on the inner circumferential surface of the tube. The effect of improvement is exhibited, and the effect of reducing the pressure loss is exhibited by the axial groove extending in the pipe axis direction on the virtual dividing line, and furthermore, the overhang portion that projects in the pipe axis direction from the bottom of the axial groove. The nucleate boiling promoting effect is exerted by the cavity formed at the bottom of the circumferential groove. As a result, in such a heat transfer tube with an inner groove, the evaporation performance can be improved while securing excellent condensation performance and keeping the pressure loss low, particularly in the low heat medium mass velocity region. The dramatic improvement in the evaporation performance in can be achieved.

Further, according to the method of the present invention, a heat transfer tube with an inner surface groove having the structure according to the present invention having the above-described excellent heat transfer performance and low pressure loss performance can be obtained with excellent mass productivity and cost performance. It can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is an exploded view of an inner peripheral surface cut by a cut surface extending in a tube axis direction, showing an example of an inner grooved heat transfer tube having a structure according to the present invention.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a sectional view taken along the line III-III in FIG. 2;

FIG. 4 is an explanatory view schematically showing a rolling and tube forming apparatus for manufacturing the heat transfer tube with inner grooves shown in FIG.

FIG. 5 is a development view corresponding to FIG. 1, showing a heat transfer tube material after processing by a primary grooved roll and before processing by a secondary grooved roll in the rolling and tube forming apparatus shown in FIG. 4;

FIG. 6 is an explanatory view of a relevant part, showing an enlarged part (b) in FIG. 4;

FIG. 7 is a sectional view taken along the line VII-VII in FIG. 6;

FIG. 8 is a development view of an inner peripheral surface cut out by a cut surface extending in a tube axis direction, showing a heat transfer tube as an example of the present invention used for measuring heat transfer performance.

FIG. 9 is a developed view corresponding to FIG. 8, showing a heat transfer tube as Comparative Example 1 used for measuring heat transfer performance.

FIG. 10 is a development view corresponding to FIG. 8, showing a heat transfer tube as Comparative Example 2 used for measuring heat transfer performance.

FIG. 11 is an explanatory view schematically showing a test apparatus for measuring the heat transfer performance of various heat transfer tubes.

FIG. 12 is a perspective view for explaining the arrangement of heat transfer tubes in the test apparatus shown in FIG. 11;

FIG. 13 is a graph showing the results of measuring the heat transfer performance in the low heat transfer medium mass velocity region using the test apparatus shown in FIG. 11 for various heat transfer tubes as examples and comparative examples.

FIG. 14 is a graph showing the results of measuring the heat transfer performance of the various heat transfer tubes as examples and comparative examples in the high heat transfer medium mass velocity range using the test apparatus shown in FIG. 11;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Heat transfer tube with an inner groove 12 Circumferential groove 14 (ad) Virtual division line 16 (ad) Division area 18 Fin-shaped ridge 20 (ad) Axial groove 32 Overhang part 24 Cavity

Claims (3)

[Claims] An inner circumferential surface of a pipe is divided into a plurality of divided areas in a circumferential direction by a virtual dividing line extending linearly in a pipe axis direction, and each of the divided areas is inclined with respect to the pipe axis direction. In addition, a large number of fin-shaped protrusions whose inclination directions are opposite to each other on both sides of the virtual dividing line are formed apart from each other in the tube axis direction, so that the fin-shaped protrusions are located between the fin-shaped protrusions adjacent in the tube axis direction. In the heat transfer tube with an inner surface groove provided with a circumferential groove extending in the circumferential direction of the tube, the projecting height of the fin-shaped projection is reduced on at least one of the virtual dividing lines, and the tube is moved in the axial direction on the virtual dividing line. And an overhang portion that projects in the tube axis direction toward the circumferential groove with respect to the tip portion of the fin-shaped projection having a low protruding height that forms the axial groove. Provided integrally with the periphery Inner surface grooved heat transfer tube, characterized in that the overhang portion covered with the cavity is formed in the bottom of the groove. 2. The heat transfer tube with an inner surface groove according to claim 1, wherein the fin-shaped protrusion and the circumferential groove are formed in a ring shape continuously in the circumferential direction. 3. A plurality of divided regions separated by virtual dividing lines extending linearly in the plate longitudinal direction with respect to one surface of the strip-shaped heat transfer tube material, and are inclined with respect to the plate longitudinal direction; After forming a large number of fin-shaped projections having inclined directions opposite to each other on both sides of the virtual dividing line, spaced apart in the plate longitudinal direction, the heat transfer tube material is curved in the plate width direction, and the heat transfer tube material is bent in the plate width direction. When manufacturing a heat transfer tube with an inner surface groove having a circumferential groove extending between the fin-like protrusions adjacent in the tube axis direction and extending in the tube circumferential direction by butt-joining both side edge portions, the heat transfer tube After forming the plurality of fin-shaped projections on the material, on at least one of the virtual dividing lines,
An inner surface groove obtained by crushing the tip of each of the fin-like projections to lower the projection height of the fin-like projection, and projecting the projection tip of the fin-like projection on the virtual dividing line. In the heat transfer tube, an axial groove extending in the axial direction of the tube is formed by a crushed portion of the fin-shaped protrusion, and the circumferential groove is covered by the protrusion of the fin-shaped protrusion by covering the circumferential groove. A method of manufacturing a heat transfer tube with an inner surface groove, wherein an overhang portion is formed in which a bottom portion of the heat transfer tube has a cavity shape.