JPH0953893A - Heat transfer tube having internal groove - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the heat transfer efficiency of a heat transfer tube having internal grooves. SOLUTION: In a heat transfer tube having internal grooves in which a large number of fins inclined in the axial direction of a metallic tube are formed on the inner circumferential surface of the metallic tube, the fins 2 are formed so that the positive and negative signs of the angles α, β, α', β' of inclination relative to the axis are opposite to each other for the prescribed interval in the axial direction. The absolute value of the angle of inclination of the fins 2 is 10-20 deg. relative to the axis. The fins 2 are of zigzag shape continuously in the circumferential direction of the inner circumferential surface of the metallic tube.

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 A heat transfer tube with an inner groove of this kind is mainly used as an evaporation tube or a condensation tube in a heat exchanger of an air conditioner or a cooling device, and recently, it has a spiral shape over the entire inner surface. A heat transfer tube having a fin shape is widely available on the market.

The heat transfer tube, which is currently the mainstream, is a metal tube obtained by passing a floating plug having a spiral groove formed on the outer peripheral surface inside a seamless (seamless) tube obtained by drawing or extruding. The fins are manufactured by a method of rolling the fins over the entire inner peripheral surface of the, and in a commonly used heat transfer tube having an outer diameter of about 10 mm, 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 set to 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. When used as a condensing tube for liquefying the heat transfer medium gas, the fin tips are exposed from the liquid surface, so that the contact efficiency between the metal surface and the heat transfer medium gas 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 inventors of the present invention created various types of heat transfer tubes with inner groove by changing the developed shape of the groove of the heat transfer tube variously, and conducted an experiment to compare their performances. It has been found that, when the positive and negative inclination angles are reversed at regular intervals in the axial direction, higher heat exchange performance can be obtained compared to other groove shapes. Also, when the fins are formed continuously or in a plurality in the circumferential direction so as to form a zigzag shape, or when the fins are divided in a large number in the circumferential direction and adjacent fins are inclined in the same direction. Found that the heat exchange performance can be further improved.

[0006]

The present invention has been made on the basis of the above findings, and the heat transfer tube with an inner groove of the present invention is inclined to the inner peripheral surface of the metal tube with respect to the axial direction of the metal tube. A large number of fins are formed, and the fins are formed such that the positive and negative inclination angles with respect to the axis line are reversed at regular intervals in the axial direction.

[0007]

FIG. 1 is a development view of a first embodiment of a heat transfer tube with an inner surface groove according to the present invention. This heat transfer tube with inner groove 1 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. The fins 2 have positive and negative inclination angles α and β with respect to the axis. Is reversed at every constant interval L in the axial direction (α → α ′ → α → α ′
,, β → β ′ → β → β ′ ...). A groove portion 4 having a constant width is formed between the adjacent fins 2, and a protrusion having a constant width extending over substantially the entire circumference in the circumferential direction of the inner peripheral surface is provided at the boundary portion where the direction of the fin 2 changes. Article 6 is formed.

A finless portion 8 of a constant width extending in the axial direction is formed over the entire length on a part of the inner peripheral surface of the inner surface grooved heat transfer tube 1. As shown in FIG. A weld line 10 is formed along the center of the portion 8 over the entire length. The fin 2 is divided by the finless portion 8 and the welding line 10. The welding line 10 may be a ridge protruding toward the inner peripheral side of the heat transfer tube 1 with an inner groove, but when expanding the pipe by inserting a diameter expansion plug into the inner diameter of the heat transfer tube 1 with an inner 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 FIG. 4, four regions R1 to R4 are provided at every 90 ° circumferential direction.
Is divided into four equal parts, and one of the areas (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 ′) formed by the fin 2 and the axis line are opposite to each other. Is formed. The absolute values of the inclination angles (α, β, α ', β') are all preferably 10 to 25 °. If the absolute value of the inclination angle exceeds 25 °, the fins 2 become nearly perpendicular to the flow, blocking 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 effect of turbulent flow generation by the fins 2 decreases.

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 range.
Similarly, the absolute values of the inclination angles α and α'and the inclination angle β
The absolute values of 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 made parallel to each other in the same region, but they do not necessarily have to be parallel, and as long as they are within the angle range, the The angles may be different.

The interval L for reversing the angle of the fin 2 is not limited, but 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 unevenness of the heat medium by the fins 2 can be obtained while sufficiently exerting the stirring effect of the heat medium by the fins 2, and the balance between the two is good.

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

However, the protrusions 6 do not necessarily have to be formed 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 end portions of the fins 2 may be abutted to each other to form the abutting portion 14 as shown in FIG. 6, or the fins 2 may be continuous to each other as shown in FIG. 7. . Also in these cases, it is possible to prevent the deterioration of the deformation resistance strength at the boundary portion of the fin 2.

As shown in FIG. 4, the cross-sectional shape of the fins 2 is such that the pitch P of the fins 2 in the same region is preferably 0.
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, more preferably 0.22 to 0.26 mm. In this way, when the fin shape which is taller than the conventional one is adopted, the turbulent flow 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. In addition, since the fin 2 having such a thin shape has a good drainage property at the tip of the fin 2 even when the inner surface of the metal tube 1 is covered with the heat medium liquid, it is used as a condenser tube. In this case, the tip metal surfaces of the fins 2 are likely to come into direct contact with the heating medium gas, and good condensing performance can be obtained.

The angle γ (vertical angle) formed by 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 fins 2 is small as described above, the side surfaces of the fins 2 stand upright almost vertically from the inner peripheral surface of the pipe, and therefore at least V is viewed from the upstream side of the heat transfer medium of the fins 2.
The heat medium liquid is rarely blown up onto the fins 2 by the wind pressure of the heat medium gas flowing in the heat transfer tube 1 except for the portion which becomes the V-shaped valley. For this reason, not only the effect of restricting the flow of the heat medium liquid by the fins 2 to cause turbulent flow is increased, but also when the heat transfer pipe 1 is used as a condensing pipe, the tips of the individual fins 2 are exposed. The tendency becomes higher, the contact area between the heat medium gas and the metal surface is increased, and 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 of the outer diameter, wall thickness, length, etc. of the heat transfer tube 1 are not limited, and the present invention can be applied to any heat transfer tube of any size that has been conventionally used. Copper or a copper alloy is generally used as the material of the heat transfer tube 1, but the present invention is not limited thereto, and various metals such as aluminum can also be used. Although the heat transfer tube 1 has a circular cross section in this embodiment, the present invention is not limited to the circular cross section, and may have an elliptical cross section, a flat tubular shape, or the like as necessary. Furthermore, it is also effective to enclose a heat medium and use it as the body of the 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 used for the fins 2 and the groove portions 4.
The fins 2 and the groove portions 4 are simultaneously formed on the surface of the strip material by rolling by passing between a rolling roll and a receiving roll each having a cross section having a complementary shape. As the rolling roll, it is also possible to use a laminated roll in which rolling rolls with spiral grooves for forming the fins 2 and the groove portions 4 are alternately stacked with the spiral directions reversed, and in that case, each of the laminated rolls is laminated. By exchanging the rolls, the shape of each part can be set arbitrarily.

Next, the metal sheet material on which the fins 2 and the groove portions 4 have been transferred is set in an electric sewing machine with the groove forming surface facing the inner surface side, and is passed between the forming rolls in multiple stages as shown in FIG. As shown in (4), the strip material is rolled in the width direction, and the finless portions 8 which are finally butted are welded to each other to form a circular tube shape to obtain an inner grooved heat transfer tube. At this time, the welding line 10 is formed at the center of the finless portion 8. The electric sewing machine may be one that is normally used, and the electric sewing conditions may be the same as in normal processing. Then, after shaping the welded portion on the outer peripheral surface of the heat transfer tube, the heat transfer tube is wound into a roll or cut into a predetermined length.

According to the heat transfer tube with inner groove 1 having the above-mentioned 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 agitated in the process. In addition to facilitating heat exchange between the heat transfer tube 1 with inner groove and the heat medium,
Even if the heat medium is concentrated on a certain portion of the inner surface of the heat transfer tube with inner groove 1 in this stirring process, the heat medium is inclined again by the fin 2 in the next region where the inclination angle of the fin 2 is reversed. In the process, heat medium agitation is performed. In this way, the action of forcibly changing the direction of the flow of the heat medium and stirring is repeated for each constant distance L, so that the heat exchange efficiency can be improved.

In particular, in this embodiment, since the fins 2 formed on the inner surface of the heat transfer tube 1 with the inner surface groove are arranged so as to form two pairs of V-shapes that open to the upstream side of the heat transfer medium flow. , The heat medium collides and joins at the V-shaped butting parts,
It flows over these butted parts. In this process, the heat medium is agitated to generate irregular turbulent flow, so that the stirring effect is further enhanced in combination with the above effect, and it is possible to prevent a temperature gradient from occurring in the flow of the heat medium, and the heat medium and the metal. It is possible to enhance heat transfer efficiency by promoting heat exchange with the surface.

[Second Embodiment] FIG. 8 is a development view of the inner surface of a second embodiment of the heat transfer tube with inner groove according to the present invention. This embodiment differs from the first embodiment in that the fin 2 does not bend in a zigzag shape and has a simple spiral shape, and other configurations may be the same as those in the above-described embodiment. According to the heat transfer tube 1 with such an inner groove, since the heat medium flowing in the tube is alternately rotated in the opposite direction by the spiral fins 2 which are inverted at regular intervals L, a simple spiral fin is formed. Unlike the heat transfer tube, the heat medium does not flow in a specific place in a lump, and a high stirring effect can be obtained. Therefore,
It is possible to improve the heat exchange efficiency.

[Third Embodiment] FIG. 9 is a developed view of the inner surface of a third embodiment of the heat transfer tube with an inner groove according to the present invention.
In this embodiment, the first point is that the fin 2 is formed in a V shape.
Different from the embodiment. That is, in this embodiment, the inner peripheral surface of the pipe is divided into two regions R1 and R2 in the circumferential direction, and the angles α and β formed by the axis and the fins 2 in each of these regions R1 and R2 are opposite to each other. ing. Further, the inclination angles α and β in the respective regions R1 and R2 are opposite in positive and negative (α → α ′ → α ..., β → at every constant interval L in the tube axis direction).
It is formed so that β '→ β ...). Other configurations may be the same as in the first embodiment.

According to the heat transfer tube 1 with such an inner groove, the heat medium flowing inside the tube tends to concentrate toward the valleys of the V-shaped fins 2, and the heat medium flow is V-shaped. They collide and join at the valley of the letter, but the direction of the fin 2 is reversed next time,
The heat medium flow is divided into the right and left 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 for every constant distance L, the heat exchange efficiency between the heat medium and the inner grooved heat transfer tube 1 is enhanced, and high heat transfer performance is obtained.

[Fourth Embodiment] FIG. 10 is an inner surface developed view showing a fourth embodiment of the heat transfer tube with inner groove according to the present invention. In this embodiment, the developed shape of the fins 2 is changed to the inner peripheral surface of the tube. This is different from the first embodiment in that it has a “VVV” shape in which the light is refracted 5 times in the circumferential direction. That is, in this embodiment, the inner peripheral surface of the pipe is divided into six regions R1 to R6 in the circumferential direction, and the axis and the fin 2 are formed in each of these regions R1 to R6.
The angles α and β formed by and are opposite to each other. Further, the inclination angles α and β in the respective regions R1 and R2 are opposite in positive and negative (α → α ′ → α ..., β → at every constant interval L in the tube axis direction).
It is formed so that β '→ β ...). Other configurations may be the same as in the first embodiment. The same effect as that of the first embodiment can be obtained also by such a heat transfer tube 1 with an inner surface groove.

If the number of divided regions is too large, the flow resistance due to 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 an even number,
Even an odd number has little effect on the effect.

[Fifth Embodiment] FIG. 11 is an inner surface development view showing a fifth embodiment of the heat transfer tube with inner groove according to the present invention. In this embodiment, the V-shaped fin 2 shown in FIG. 9 is used. A new feature is that a gap 20 is formed in the central portion of the. That is, in this heat transfer tube 1 with groove on the inner surface, two fins 2 which are inclined in the circumferential direction of the inner surface of the tube are arranged in a zigzag pattern at intervals. The inclination angle and other configurations may be the same as in the first embodiment.

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

According to the fifth embodiment having such a configuration, the heat medium collected by the side surface of each fin 2 collides at the V-shaped abutting portions and merges, and further passes through the gap 20. In the process. The heating medium is agitated. Therefore,
It is possible to suppress the pressure loss of the heat medium flowing in the heat transfer tube 1 to be small without substantially impairing the heat medium stirring effect of the fins 2. As described above, the fact that two contradictory effects of improving the heat transfer efficiency and reducing the pressure loss can be achieved at the same time is an important effect of the present embodiment. Of course, also in this embodiment, the fins 2 are provided at regular intervals L in the tube axis direction.
Since the inclination angle of is reversed, the effect of alternately diffusing and concentrating the flow of the heat medium is obtained.

[Sixth Embodiment] FIG. 12 is an inner surface development view showing a sixth embodiment of the heat transfer tube with inner groove according to the present invention. In this embodiment, the W-shaped fin 2 shown in FIG. 1 is used. A new feature is that the gap 20 is formed at each of the refraction points. 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 suppressed to be small without impairing the effects of the embodiment of FIG.

[Seventh Embodiment] FIG. 13 is an inner surface development view showing a seventh embodiment of the heat transfer tube with inner groove according to 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. Also in this case, the effect of the embodiment of FIG. 8 can be obtained, and the effect of suppressing the pressure loss of the heat medium flowing in the heat transfer tube 1 can be obtained by appropriately releasing the heat medium through the gap 20.

[Eighth Embodiment] FIG. 14 is an inner surface development view showing an eighth embodiment of the heat transfer tube with inner groove according to the present invention. In this embodiment, the "VVV" shape shown in FIG. 10 is formed. A new feature is that a gap 20 is formed at every other refraction point of the fin 2. Also in this case, the effect of the embodiment of FIG. 10 can be obtained, and the effect of suppressing the pressure loss of the heat medium flowing in the heat transfer tube 1 can be obtained by appropriately releasing the heat medium through the gap 20.

[Ninth Embodiment] FIG. 15 shows a ninth embodiment of the present invention.
It is an inner surface development view showing an embodiment, and in this embodiment, a new feature is that the interval in which the inclination direction of the fin 2 is reversed in each region is made different for each region. That is, the positions of the ridges 6A and 6B formed at the inversion boundary are displaced from each other in the tube axis direction. Also in this case, the shape of the boundary portion may be any of the structures shown in FIGS. 2, 5, 6 and 7.

The inner surface grooved heat transfer tube according to the present invention is not limited to the above-mentioned embodiments, but various other structures are possible. For example, when the outer diameter of the heat transfer tube is large, it is possible to partition the inner peripheral surface of the heat transfer tube into seven or more regions, and if necessary, each fin 2 is not linear when deployed, It is also possible to form an arc shape when unfolding. Further, only the fins in the even or odd areas may be changed such that the fins are displaced by an anti-pitch in the tube axis direction, or recesses or notches may be separately formed at appropriate positions of each fin 2.

[0034]

EXAMPLES Next, the effects of the present invention will be demonstrated with reference to examples. Five types of heat transfer tubes A1 that differ only in the planar shape of the fins
-A5 were formed, and the heat transfer efficiency of these heat transfer tubes was compared. The fin plane shape of each heat transfer tube is as follows. A1: A simple spiral type in which the fin angle is not reversed A2: A spiral type in which the fin angle is reversed every 300 mm in the axial direction (Fig. 8) A3: A V shape in which the V-shaped fin is reversed every 300 mm in the axial direction (Fig. 9) A4 : W-shaped fin in which the W-shaped fin reverses every 300 mm in the axial direction (Fig. 1) A5: VVV-shaped fin in which the VVV-shaped fin reverses every 300 mm in the axial direction (Fig. 10)

The inclination angle of the fin with respect to the axis of the heat transfer tube was 15 ° or -15 °, and the size of the fin 2 was thinner and higher than the conventional product (see FIG. 4). Fin pitch P: 0.36 mm Fin height H: 0.24 mm Fin angle on both side surfaces γ: 17 ° Groove width between fins: 0.22 mm Further, the outer diameter of the heat transfer tube 1 with inner groove 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 velocity: 1.5 m / s Total length of heat transfer tube: 3.5 m Saturation temperature during evaporation: 5 ° C Superheat degree 3 deg Saturation temperature during evaporation: 45 ° C Supercooling degree 5 deg Heat medium: Freon "R-22" (trade name)

18 and 19 show the results of the evaporation performance, the condensation performance, and the pressure loss obtained by the above experiment expressed as a ratio with respect to the A1 type heat transfer tube. As is clear from these graphs, A1 with simple spiral fins formed
In contrast, in A2 to A5 in which the fin inclination angle was reversed at regular intervals in the axial direction, although the pressure loss was slightly large, the evaporation performance and the condensation performance were improved to some extent by supplementing it. Among the tubes with the fin angles reversed, the A3, A4, and A5 heat transfer tubes exhibited particularly excellent condensation performance.

[0039]

As described above, according to the heat transfer tube with the inner groove 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. Heat transfer between the inner grooved heat transfer tube and the heat medium is promoted, and even if the heat medium is concentrated on a certain part of the inner surface of the inner grooved heat transfer tube during this stirring process, this heat medium flow causes the inclination of the fins. In the next region where the angle is reversed, the traveling direction is changed again by the fins, and the heating medium is stirred again in the process. In this way, the action of forcibly changing the direction of the flow of the heat medium and stirring is repeated at regular intervals, so it is possible to improve heat exchange efficiency.

[Brief description of drawings]

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

FIG. 17 is a schematic diagram showing a measuring device for 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]

 1 Heat Transfer Tube with Inner Surface Groove 2 Fin 4 Groove 6 Protruding Strip 8 Finless Part 10 Weld Line 12 Intersection 14 Intersection 20 Gap α, β, α ', β'Inclination Angle of Fin to Pipe Axis L Inversion Intervals R1 to R6 Area divided in the circumferential direction

Claims (8)

[Claims] 1. A heat transfer tube with an inner surface groove, wherein a large 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, wherein the fins have positive and negative inclination angles with respect to the axis. Is formed so as to be reversed at regular intervals in the axial direction. 2. The heat transfer tube with an inner surface groove according to claim 1, wherein the absolute value of the inclination angle of the fin is 10 to 25 ° with respect to the axis. 3. The heat transfer tube with internal groove according to claim 1, wherein each of the fins has a zigzag shape continuous in the circumferential direction of the inner peripheral surface of the metal tube. 4. The fins are each divided into a plurality of pieces in the circumferential direction of the inner circumferential surface of the metal tube, and the fins adjacent to each other in the circumferential direction have positive and negative opposite angles with respect to the heat transfer tube axis. The heat transfer tube with an inner surface groove according to claim 1 or 2. 5. The fins are each divided into a plurality of pieces in the circumferential direction of the inner peripheral surface of the metal tube, and the fins adjacent to each other in the circumferential direction have the same angle with respect to the heat transfer tube axis. Alternatively, the heat transfer tube with the inner groove described in 2. 6. The heat transfer tube with internal groove according to claim 4, wherein a gap is formed between the end portions of the fins that are adjacent to each other in the circumferential direction. 7. The fin pitch is 0.3 to 0.45.
mm, the height of the fin from the inner peripheral surface of the metal tube is 0.15
~ 0.30 mm, the angle between both sides of the fin is 10
The heat transfer tube with an inner groove according to any one of claims 1 to 6, wherein the heat transfer tube has an angle of -25 °. 8. The inner surface according to claim 4, wherein the fins are divided into any number of 2 to 6 in a circumferential direction of an inner peripheral surface of the metal tube. Groove heat transfer tube.