JP2922824B2 - Heat transfer tube with internal groove - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inner grooved heat transfer tube used for a heat exchanger of an air conditioner or a cooling device.

[0002]

2. Description of the Related Art This type of heat transfer tube with an inner groove is mainly used as an evaporator tube or a condenser tube in a heat exchanger of an air conditioner or a cooling device. Heat transfer tubes having a shape of a fin are widely commercially available.

[0003] A heat transfer tube, which is currently the mainstream, is formed by passing a floating plug having a spiral groove on the outer peripheral surface thereof through a seamless (seamless) tube obtained by drawing or extruding. Is manufactured by a method of rolling fins over the entire inner peripheral surface of a fin. In a generally used heat transfer tube having an outer diameter of about 10 mm, the fin height is 0.15 to 0.20 mm and the fin height is 0.15 to 0.20 mm. Pitch (distance between vertices of adjacent fins) is 0.45
0.55 mm, the bottom width of the groove formed between the fins is 0.2
It is about 0 to 0.30 mm.

[0004] In such a heat transfer tube with an inner surface groove formed with a spiral fin, the heat transfer liquid accumulated in the lower portion inside the heat transfer tube is
It is blown by the steam flow flowing in the pipe, is wound up along the spiral fins, and spreads over the entire inner peripheral surface of the pipe. By this action, the entire inner peripheral surface of the pipe is almost uniformly wetted. Therefore, when the pipe is used as an evaporating pipe for evaporating the heating medium liquid, the area of the region where boiling occurs can be increased to increase the boiling efficiency. Further, when the heat transfer medium is used as a condensing tube for liquefying the heat transfer medium, the fin tips are exposed from the liquid surface, so that the contact efficiency between the metal surface and the heat transfer medium can be increased, and the condensation efficiency can be increased.

[0005]

However, it has been found that the effect of improving the heat transfer efficiency by the spiral fins leaves room for further improvement. Therefore, the present inventors made various types of heat transfer tubes with internal grooves by changing the development shape of the grooves of the heat transfer tubes in various ways, and conducted experiments to compare their performance. It has been found that, when the positive and negative of the inclination angle are formed so as to be reversed at regular intervals in the axial direction, a higher heat exchange performance can be obtained as compared with other groove shapes. Also, when the fins are formed continuously or in the circumferential direction so as to form a zigzag shape by dividing into a large number, or when the fins are divided into a large number in the circumferential direction and the adjacent fins are inclined in the same direction. Found that the heat exchange performance could be further improved.

[0006]

Means for Solving the Problems The present invention has been made based on the above findings, and a first heat transfer tube with an inner surface groove of the present invention is provided on the inner peripheral surface of a metal tube in the axial direction of the metal tube. An inner grooved heat transfer tube in which a large number of fins inclined with respect to the inner tube are formed, and the inner peripheral surface of the metal tube is divided into a plurality of regions in a circumferential direction, and each region is formed with respect to an axial direction of the metal tube. A large number of fins extending in the inclined direction are respectively formed, and the inclination angles of the fins formed in each of the adjacent regions are alternately reversed in the positive and negative directions, and each of the regions is arranged at regular intervals in the axial direction of the metal tube. Is characterized in that the positive and negative angles of the fins are alternately reversed. Further, the second internally grooved heat transfer tube of the present invention is an internally grooved heat transfer tube in which a number of fins inclined with respect to the axial direction of the metal tube are formed on the inner peripheral surface of the metal tube. The fin has an inclination angle of 100 to 500 mm in the axial direction with respect to the axis.
It is characterized in that it is formed so as to be inverted at every interval, and furthermore, ridges extending in the circumferential direction of the metal tube are formed at places where the inclination angle of the fin is inverted.

[0007]

FIG. 1 is a developed view of a first embodiment of a heat transfer tube with an inner surface groove according to the present invention. This heat transfer tube 1 with an inner groove has a large number of fins 2 extending in a zigzag shape in the circumferential direction on the inner peripheral surface of a metal tube, and these fins 2 have positive and negative inclination angles α and β with respect to an axis. Are reversed at regular intervals L in the axial direction (α → α ′ → α → α ′).
.., Β → β ′ → β → β ′ ...). A groove 4 having a constant width is formed between adjacent fins 2, and a protrusion having a constant width extends over substantially the entire circumference in the circumferential direction of the inner peripheral surface at a boundary where the direction of the fin 2 changes. Article 6 is formed.

A finless portion 8 having a constant width extending in the axial direction is formed on a part of the inner peripheral surface of the inner grooved heat transfer tube 1 over its entire length. As shown in FIG. A weld line 10 is formed over the entire length along the center of the portion 8. The fin 2 is divided by the finless portion 8 and the welding line 10. The welding wire 10 may be a ridge protruding toward the inner peripheral side of the heat transfer tube 1 with an inner surface groove. It is preferable that the protrusion amount is smaller than that of the fin 2 so that the plug does not hit the welding line 10.

The inner peripheral surface of the heat transfer tube 1 of this embodiment is shown in FIG.
As shown in the figure, four regions R1 to R4 are provided every 90 ° in the circumferential direction.
Into approximately four equal parts, and any one region (in this case, R
In the odd-numbered regions R1 and R3 and the even-numbered regions R2 and R4 counted from 1), the inclination angles (α and β; α ′ and β ′) between the fin 2 and the axis are opposite to each other. It is formed to become. It is preferable that the absolute values of the inclination angles (α, β, α ′, β ′) are all 10 to 25 °. If the absolute value of the inclination angle exceeds 25 °, the fins 2 become almost perpendicular to the flow, interrupting the flow and increasing the pressure loss, which is not preferable. If the absolute value of the inclination angle is less than 10 °, the fins 2 become nearly parallel to the flow, and the turbulence generation effect of the fins 2 is reduced.

The absolute values of the inclination angles α and β and the absolute values of the inclination angles α ′ and β ′ may be equal to each other, but may be different as long as they are within the above-mentioned range.
Similarly, the absolute values of the inclination angles α and α ′, and the inclination angle β
And β ′ may be equal to each other, but may be different as long as they are within the above range. Further, in the embodiment of FIG. 1, the fins 2 are parallel to each other in the same region, but they are not necessarily parallel to each other, and as long as the fins 2 are within the aforementioned angle range, the fins 2 are tilted for each fin. The angles may be different.

Although the interval L of the angle reversal of the fin 2 is not limited, it is preferably 100 to 500 mm, more preferably 200 to 400 mm. 100-5
Within the range of 00 mm, the effect of correcting the bias of the heat medium by the fins 2 can be obtained while sufficiently exerting the effect of stirring the heat medium by the fins 2, and the balance between the two is good.

As shown in FIG. 2, the ridge 6 has a gentle convex curved cross section, and the maximum protrusion amount is smaller than that of the fin 2. By forming such ridges 6, the average thickness of the heat transfer tube 1 with the inner surface groove at the reversal boundary of the fin 2 is made almost the same as other portions, and the deformation resistance at the boundary of the fin 2 is reduced. Can be prevented.

However, it is not always necessary to form the ridges 6 at the boundary portions of the fins 2 as shown in FIG. 2, and for example, as shown in FIG. The portion 12 may be formed, the butting portion 14 may be formed by abutting the ends of the fins 2 as shown in FIG. 6, or the fins 2 may be continuous as shown in FIG. . Also in these cases, it is possible to prevent a decrease in the deformation resistance at the boundary between the fins 2.

As shown in FIG. 4, the cross-sectional shape of the fins 2 is preferably such that the pitch P of the fins 2 in the same region is 0.1 mm.
3 to 0.45 mm, more preferably 0.33 to 0.3
The height H of the fin 2 from the inner peripheral surface of the metal tube is preferably 0.15 to 0.30 mm, and more preferably 0.22 to 0.26 mm. When a fin shape that is taller than the conventional fin shape is used, the turbulence generation effect is good, and the heat exchange efficiency of the heat transfer tube 1 can be further improved in combination with the effect of the special fin arrangement. Further, according to the thin and high fins 2 described above, even when the inner surface of the metal tube 1 is covered with the heating medium liquid, the drainage at the tip of the fins 2 becomes good, so that the fins 2 are used as a condensation tube. In this case, the metal surface at the tip of the fin 2 easily comes into direct contact with the heat medium gas, and good condensation performance can be obtained.

The angle γ (vertical angle) between both side surfaces of the fin 2 is preferably 10 to 25 °, more preferably 15 to 20 °.
さ れ る. When the apex angle of the fin 2 is small as described above, the side surface of the fin 2 stands almost perpendicularly from the inner peripheral surface of the tube.
Except for the valley-shaped valleys, the heat medium liquid rarely blows up onto the fins 2 due to the wind pressure of the heat medium gas flowing in the heat transfer tube 1. For this reason, not only the effect of restricting the flow of the heat medium liquid by the fins 2 and causing a turbulent flow is increased, but also when the heat transfer tube 1 is used as a condensing tube, the tips of the individual fins 2 are exposed. The tendency increases, and the contact area between the heat medium gas and the metal surface is increased, so that high condensation efficiency can be obtained. In the illustrated example, the apexes of the fins 2 are semicircular in cross section, but the present invention may have a trapezoidal cross section or a triangular cross section.

The dimensions such as the outer diameter, wall thickness, and length of the heat transfer tube 1 are not limited, and the present invention can be applied to a heat transfer tube of any size conventionally used. Copper or a copper alloy is generally used as a material of the heat transfer tube 1, but the present invention is not limited thereto, and various metals such as aluminum can be used. In this embodiment, the cross-sectional shape of the heat transfer tube 1 is circular. However, the present invention is not limited to a circular cross-section, and may be an elliptical cross-section or a flat tube if necessary. Furthermore, it is also effective to enclose a heat medium and use it as a main body of a heat pipe.

In order to manufacture such a heat transfer tube with an inner groove, the following method can be adopted. First, a strip-shaped metal plate material is prepared, and this plate material is provided with the fin 2 and the groove 4.
The fins 2 and the grooves 4 are formed simultaneously on the surface of the sheet material by rolling between a rolling roll and a receiving roll each having a cross section complementary to each other. As the rolling roll, a laminating roll in which spiral rolls with spiral grooves for forming the fins 2 and the groove portions 4 are alternately stacked with the direction of the spiral reversed may be used. By exchanging the rolls, the shape of each part can be set arbitrarily.

Next, the metal plate material on which the fins 2 and the groove portions 4 have been transferred is set on an electric resistance sewing machine with the groove forming surface facing the inner surface side, and is passed between forming rolls in multiple stages as shown in FIG. As shown in (1), the plate material is rolled in the width direction, and the finless portion 8 that is finally abutted is welded and formed into a circular tube shape to obtain an inner surface grooved heat transfer tube. At this time, a welding line 10 is formed at the center of the finless portion 8. The ERW device may be a commonly used one, and the ERW conditions may be the same as those for normal processing. Thereafter, the welded portion is shaped on the outer peripheral surface of the heat transfer tube, and the heat transfer tube is wound into a roll or cut to a predetermined length.

According to the heat transfer tube with inner groove 1 having the above structure, the heat medium flowing in the heat transfer tube with inner groove 1 is inclined in the traveling direction along the fins 2, and the heat medium is stirred in the process. Heat exchange between the inner grooved heat transfer tube 1 and the heat medium is promoted,
Even if the heat medium concentrates on a certain portion of the inner surface of the heat transfer tube 1 with the inner surface in the stirring process, the heat medium is again inclined in the traveling direction by the fin 2 in the next region where the inclination angle of the fin 2 is reversed. In this process, the heating medium is stirred. As described above, since the action of forcibly changing the direction of the flow of the heat medium and stirring is repeated for each predetermined distance L, the heat exchange efficiency can be improved.

In particular, in this embodiment, the fins 2 formed on the inner surface of the inner grooved heat transfer tube 1 are arranged so as to form two pairs of V-shapes that open upstream of the heat medium flow. , The heat medium collides and merges at the abutting portion of each V-shape,
It flows over these butted parts. In this process, the heating medium is agitated and irregular turbulence is generated, so that the stirring effect is further enhanced in combination with the above-mentioned effect, and a temperature gradient can be prevented from being generated in the flow of the heating medium, and the heating medium and metal It is possible to enhance heat transfer efficiency by promoting heat exchange with the surface.

[Second Embodiment] FIG. 8 is a developed view of the inner surface showing a second embodiment of a heat transfer tube with an inner groove according to the present invention. This embodiment is different from the first embodiment in that the fins 2 do not bend in a zigzag shape and have a simple spiral shape, and other configurations may be the same as those in the above embodiment. According to such a heat transfer tube 1 with an inner groove, a simple spiral fin is formed because the heat medium flowing in the tube is alternately rotated in the opposite direction by the helical fins 2 which are inverted every predetermined distance L. Unlike the heat transfer tube, the heat medium does not flow in a specific portion at a time, and a high stirring effect can be obtained. Therefore,
It is possible to improve the heat exchange efficiency.

[Third Embodiment] FIG. 9 is an inner developed view showing a third embodiment of a heat transfer tube with an inner groove according to the present invention.
In this embodiment, the point that the fin 2 is formed in a V-shape is the first point.
Different from the embodiment. That is, in this embodiment, the inner circumferential surface of the pipe is circumferentially divided into two regions R1 and R2, and the angles α and β formed by the axis and the fin 2 in these regions R1 and R2 are opposite in sign. ing. In addition, the inclination angles α and β in the respective regions R1 and R2 are opposite in sign at regular intervals L in the tube axis direction (α → α ′ → α..., Β →
β ′ → β ...). Other configurations may be the same as in the first embodiment.

According to such a heat transfer tube 1 with an inner groove, the heat medium flowing inside the tube tends to concentrate toward the valley of the V-shaped fin 2, and the heat medium flow is Although they collide and merge at the valley of the character, since the direction of the fin 2 is reversed next,
The heat medium flow is separated left and right by the fins 2 and is collected again in the valley located on the opposite side in the circumferential direction. By repeating such a cycle at every fixed distance L, the heat exchange efficiency between the heat medium and the heat transfer tube 1 with the inner surface groove is enhanced, and high heat transfer performance is obtained.

[Fourth Embodiment] FIG. 10 is a developed view of the inner surface of a heat transfer tube with an inner groove according to a fourth embodiment of the present invention. Is different from the first embodiment in that it has a “VVV” shape that is bent five times in the circumferential direction. That is, in this embodiment, the inner circumferential surface of the tube is divided into six regions R1 to R6 in the circumferential direction, and the axis and the fin 2 are defined in each of these regions R1 to R6.
And the angles α and β are made to have opposite signs. In addition, the inclination angles α and β in the respective regions R1 and R2 are opposite in sign at regular intervals L in the tube axis direction (α → α ′ → α..., Β →
β ′ → β ...). Other configurations may be the same as in the first embodiment. The same effect as in the first embodiment can be obtained also by such an inner grooved heat transfer tube 1.

If the division number of the region is too large, the flow liquid resistance by the fins 2 becomes too large. Therefore, when the outer diameter of the heat transfer tube 1 is about 10 mm or less, about 2 to 6 is preferable. Also, the number of divisions of the area is not limited to only an even number,
Even odd numbers have little effect on the effect.

[Fifth Embodiment] FIG. 11 is a developed view of the inner surface of a heat transfer tube with an inner groove according to a fifth embodiment of the present invention. In this embodiment, the V-shaped fin 2 shown in FIG. A new feature is that a gap 20 is formed in the center of the. That is, in the heat transfer tube 1 with the inner surface groove, the two fins 2 inclined in the circumferential direction of the inner surface of the tube are arranged in a staggered manner at intervals. The tilt angle and other configurations may be the same as in the first embodiment.

The width C of the gap 20 is not limited, but is preferably 0.05 to 0.5 mm for a general heat transfer tube having an outer diameter of about 10 mm. This value is common to the following embodiments. Within such a range, the effect of reducing the flow liquid resistance of the heat medium while obtaining excellent heat exchange performance becomes remarkable. The gap 20 having the same depth as the groove 4 is more effective in reducing the flow liquid resistance, but may be shallower than the groove 4 in some cases. For example, it may be a gentle recess.

According to the fifth embodiment having such a configuration, the heat medium collected by the side surfaces of the fins 2 collides and merges at the V-shaped abutting portion, further passes through the gap 20, and in the process. The heating medium is agitated. Therefore,
The pressure loss of the heat medium flowing through the heat transfer tube 1 can be suppressed to a small value without substantially impairing the heat medium stirring effect of the fins 2. Thus, the important effect of the present embodiment is that the two opposing effects of improving the heat transfer efficiency and reducing the pressure loss can be achieved at the same time. Of course, also in this embodiment, the fins 2 are provided at regular intervals L in the pipe axis direction.
Has an effect of alternately diffusing and concentrating the flow of the heat medium.

[Sixth Embodiment] FIG. 12 is a developed view of the inner surface of a heat transfer tube with an inner groove according to a sixth embodiment of the present invention. In this embodiment, the W-shaped fin 2 shown in FIG. A new feature is that a gap 20 is formed at each refraction point. According to such an embodiment, the fluid resistance of the heat medium can be reduced by the gap 20 and the pressure loss of the heat medium flowing in the heat transfer tube 1 can be reduced without impairing the effects of the embodiment of FIG.

[Seventh Embodiment] FIG. 13 is a developed view of the inner surface of a heat transfer tube with an inner groove according to a seventh embodiment of the present invention. In this embodiment, the spiral fin 2 shown in FIG. A new feature is that the gaps 20 are formed at regular intervals in the longitudinal direction. In this case as well, while the effect of the embodiment of FIG. 8 is obtained, the heat medium is appropriately released by the gap 20, whereby the effect of suppressing the pressure loss of the heat medium flowing in the heat transfer tube 1 can be obtained.

[Eighth Embodiment] FIG. 14 is an inner developed view showing an eighth embodiment of an inner grooved heat transfer tube according to the present invention. In this embodiment, the "VVV" shape shown in FIG. Another feature is that a gap 20 is formed at every other refraction point of the fin 2. In this case as well, the pressure medium of the heat medium flowing in the heat transfer tube 1 can be reduced in pressure by appropriately releasing the heat medium through the gap 20 while obtaining the effects of the embodiment of FIG.

[Ninth Embodiment] FIG. 15 shows a ninth embodiment of the present invention.
FIG. 4 is an inner surface developed view showing the embodiment, and this embodiment has a new feature that the interval at which the inclination direction of the fin 2 is reversed in each region is different for each region. That is, the positions of the ridges 6A and 6B formed at the reversal boundary are mutually shifted in the pipe axis direction. Also in this case, the shape of the boundary may be any of the structures shown in FIGS. 2, 5, 6, and 7.

The heat transfer tube with an inner groove according to the present invention is not limited to the above embodiments, and various other structures are possible. For example, when the outer diameter of the heat transfer tube is large, it is possible to divide the inner peripheral surface of the heat transfer tube into seven or more regions. It can be formed in an arc shape when unfolded. Further, a change may be made such that only the fins in the even or odd regions are shifted by an anti-pitch in the tube axis direction, or a concave portion or a cut may be separately formed at an appropriate portion of each fin 2.

[0034]

Next, the effects of the present invention will be demonstrated with reference to examples. Five types of heat transfer tubes A1 differing only in the plan shape of the fins
To A5, and the heat transfer efficiency was compared for these heat transfer tubes. The fin plane shape of each heat transfer tube is as follows. A1: Simple spiral type in which the fin angle is not inverted A2: Spiral type in which the fin angle is inverted every 300 mm in the axial direction (FIG. 8) A3: V-shaped type in which the V-shaped fin is inverted every 300 mm in the axial direction (FIG. 9) A4 A: W-shaped fin with W-shaped fins inverted every 300 mm in the axial direction (FIG. 1) A5: VVV-shaped fins with VVV-shaped fins inverted every 300 mm in the axial direction (FIG. 10)

The angle of inclination of the fin with respect to the axis of the heat transfer tube was set to 15 ° or −15 °, and the size of the fin 2 was smaller and higher than that of the conventional product (see FIG. 4). Fin pitch P: 0.36 mm Fin height H: 0.24 mm Fin angle on both sides γ: 17 ° Groove width between fins: 0.22 mm Further, the outer diameter of the inner grooved heat transfer tube 1 is 8.0 mm. The average thickness was 0.35 mm and the material was copper.

Next, the heat transfer performance (evaporation performance, condensation performance) of each of the obtained heat transfer tubes A1 to A5 was measured using the apparatus shown in FIGS. When measuring
Each heat transfer tube was set in the “measurement section” in the figure, and the evaporation performance and the condensation performance were measured by the following evaluation methods. The evaluation conditions are as follows.

[Evaluation method] Counterflow double tube system Water flow rate: 1.5 m / s Total length of heat transfer tube: 3.5 m Evaporation saturation temperature: 5 ° C Superheat degree 3 deg Evaporation saturation temperature: 45 ° C Subcooling degree 5 deg Heat medium: Freon "R-22" (trade name)

FIGS. 18 and 19 show the results obtained by expressing the evaporation performance, the condensation performance, and the pressure loss obtained by the above experiment in terms of the ratio to the A1 type heat transfer tube. As is clear from these graphs, A1 formed a simple spiral fin.
A2 to A5 in which the inclination angles of the fins were inverted at regular intervals in the axial direction, as compared with, had a slightly large pressure loss, but the evaporation performance and the condensation performance were improved as much as the pressure loss was compensated. In addition, among the tubes whose fin angles were inverted, the heat transfer tubes of A3, A4, and A5 showed particularly excellent condensation performance.

[0039]

As described above, according to the heat transfer tube with inner grooves according to the present invention, the heat medium flowing in the heat transfer tube is inclined in the traveling direction along the fins, and the heat medium is agitated in the process. The heat transfer between the heat transfer medium and the heat transfer medium is promoted, and even if the heat medium is concentrated on a certain part of the inner surface of the heat transfer pipe with the inner groove during this stirring process, the heat medium flow is inclined by the fins. In the next area where the angle is reversed, the traveling direction is changed again by the fins, and the heating medium is again stirred in the process. As described above, since the action of forcibly changing the direction of the flow of the heat medium and stirring is repeated at regular intervals, the heat exchange efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a developed view of an inner surface of a first embodiment of a heat transfer tube with an inner surface groove according to the present invention.

FIG. 2 is an enlarged perspective view of a fin inversion boundary portion of the embodiment.

FIG. 3 is a plan view showing an electric sewing process of the embodiment.

FIG. 4 is an enlarged cross-sectional view of the fin of the embodiment.

FIG. 5 is an enlarged perspective view of a modification of the fin inversion boundary portion of the embodiment.

FIG. 6 is an enlarged perspective view of a modification of the fin inversion boundary portion of the embodiment.

FIG. 7 is an enlarged perspective view of a modification of the fin inversion boundary portion of the embodiment.

FIG. 8 is a developed view of an inner surface of a heat transfer tube with an inner groove according to a second embodiment of the present invention.

FIG. 9 is a developed view of an inner surface of a heat transfer tube with an inner surface groove according to a third embodiment of the present invention.

FIG. 10 is a developed view of an inner surface of a heat transfer tube with an inner surface groove according to a fourth embodiment of the present invention.

FIG. 11 is a developed view of an inner surface of a heat transfer tube with an inner groove according to a fifth embodiment of the present invention.

FIG. 12 is a developed view of the inner surface of a heat transfer tube with an inner surface groove according to a sixth embodiment of the present invention.

FIG. 13 is a developed view of an inner surface of a heat transfer tube with an inner surface groove according to a seventh embodiment of the present invention.

FIG. 14 is a developed view of the inner surface of the eighth embodiment of the heat transfer tube with an inner groove according to the present invention.

FIG. 15 is a developed view of the inner surface of the ninth embodiment of the heat transfer tube with an inner surface groove according to the present invention.

FIG. 16 is a schematic diagram showing an apparatus for measuring evaporation performance.

FIG. 17 is a schematic view showing an apparatus for measuring condensation performance.

FIG. 18 is a graph showing evaporation performance and pressure loss during evaporation.

FIG. 19 is a graph showing condensation performance and pressure loss during condensation.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 heat transfer tube with inner groove 2 fin 4 groove 6 ridge 8 finless part 10 welding line 12 intersection 14 butt 20 gap Gap angle of α, β, α ', β' fin with respect to pipe axis L Inversion intervals R1 to R6 Circumferentially separated area

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-158193 (JP, A) JP-A-2-78897 (JP, A) JP-A-2-37294 (JP, A) 71274 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) F28F 1/40 F28F 1/42

Claims (6)

(57) [Claims] An inner grooved heat transfer tube having a plurality of fins inclined with respect to an axial direction of the metal tube formed on an inner surface of the metal tube , wherein the metal tube has a plurality of inner circumferential surfaces in a circumferential direction. Area of
And each region has an axial direction of the metal tube.
Fins extending in the direction of inclination
The angle of inclination of the fins formed in each adjacent area
The sign is reversed, and the axial direction of the metal tube is
The fin inclination angle in each area changes at regular intervals of
An internally grooved heat transfer tube characterized in that the signs are reversed . 2. The fin according to claim 1 , wherein each of said fins is inside said metal tube.
A zigzag shape that is continuous in the circumferential direction of the peripheral surface
The heat transfer tube with an inner surface groove according to claim 1, wherein: 3. A gap is provided between fins adjacent in the circumferential direction.
3 is formed.
Heat transfer tube with inner groove. 4. The method according to claim 1, wherein the metal tube is disposed at regular intervals in the axial direction.
In the places where the inclination angle of the fins is reversed,
Characterized in that ridges extending in the direction are formed respectively.
The heat transfer tube with an inner surface groove according to claim 1. 5. An inner peripheral surface of a metal tube, wherein an axial direction of the metal tube is
Internal grooved transmission with many fins inclined to the direction
A heat tube, wherein the fin has an inclination angle with respect to the axis;
The sign of the degree is every 100 to 500 mm in the axial direction.
The fin is formed to be reversed, and the inclination angle of the fin is further reduced.
At the point where the degree is reversed, a ridge extending in the circumferential direction of the metal tube
Heat transfer with internal grooves characterized by being formed respectively
tube. 6. The metal pipe according to claim 6 , wherein each of said fins has an inner periphery.
The surface is divided into multiple parts in the circumferential direction,
A gap is formed between the fins
The heat transfer tube with an inner surface groove according to claim 5, wherein