JP2000205781A - Inner surface grooved heat transfer tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal surface grooved heat transfer tube with improved heat exchange efficiency by preventing to the utmost a boundary layer from being produced in the vicinity of a bottom surface of a groove, and further preventing heat insulation action by the boundary layer. SOLUTION: Many spiral long fins 2 are formed in parallel on an internal peripheral surface of a metal tube 1, each fin taking an axis of the metal tube 1 as a spiral axis. A first groove 6 is formed between these fins 2, and a short fin 4 is formed at least in a part of the aforementioned groove 6 while extending in parallel with the longer fins 2. There is further formed a second groove 8 having a narrower opening width than the first groove 6 between the longer fin 2 and the shorter fin 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a metal pipe having an inner surface
The present invention relates to a heat transfer tube having an inner surface groove formed with fins for improving heat exchange efficiency.

[0002]

2. Description of the Related Art An inner grooved heat transfer tube of this type 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.

[0004] In the heat transfer tube with an inner groove formed with such a spiral fin, if the steam flow flowing through the tube is sufficiently fast,
The heat transfer medium liquid accumulated on the lower side inside the heat transfer tube is wound up along the spiral fin while being swept away by the vapor flow, and spreads over the entire inner peripheral surface of the tube. By this action, the entire inner circumferential surface of the pipe is almost uniformly wetted, so that it is possible to prevent so-called dryout in which a part of the inner circumferential surface of the pipe is dried, and it is possible to increase the area of a region where boiling occurs and increase the boiling efficiency. it can.

On the other hand, when a heat transfer tube with an inner groove formed with spiral fins is used as a condensation tube for liquefying a heating medium gas, the fin tip protrudes from a liquid film that wets the inner surface of the tube. Thus, the effect of increasing the contact efficiency between the metal surface and the heat medium gas and increasing the condensation efficiency can be obtained.

[0006]

According to the study of the present inventors, it has been found that the heat transfer tube with the inner groove having the spiral fins has the following problems. That is, in the conventional tube, when the heat transfer liquid flows through the heat transfer tube, the heat transfer liquid flows through the groove between the spiral fins and the spiral fin. A boundary layer is generated, and the movement of the heat medium is hindered in the boundary layer. For this reason, the boundary layer acts as a so-called heat insulating layer and hinders heat exchange between the heat medium flowing in the pipe and the metal pipe.

The present invention has been made in view of the above circumstances, and minimizes the generation of a boundary layer near the bottom of a groove.
It is an object of the present invention to provide an inner grooved heat transfer tube capable of improving heat exchange efficiency by preventing a heat insulating effect by a boundary layer.

[0008]

In order to solve the above-mentioned problems, a heat transfer tube with an inner surface groove according to the present invention is formed in a spiral shape on the inner peripheral surface of a metal tube with the tube axis of the metal tube as a helical axis. A number of long fins are formed in parallel, a first groove is formed between the long fins, and a short fin extending parallel to the long fin is provided in at least a part of the first grooves. A second groove having a smaller opening width than the first groove is formed between the long fin and the short fin.

According to such a heat transfer tube with internal grooves, when a part of the heat medium flowing in the metal tube flows along the first groove between the long fins, this flow is divided by the tips of the short fins. In addition, it flows through the narrow second groove and merges again at the rear end of the shorter fin. Since the boundary layer generated near the bottom surface of the first groove in the process of the division and merging is separated and broken,
It is possible to prevent the heat insulation effect of the boundary layer, reduce the heat transfer resistance between the heat medium and the metal tube, and increase the heat exchange efficiency.

[0010]

[First Embodiment] FIGS. 1 and 2
FIG. 2 is a plan view and a cross-sectional view in which the first embodiment of the heat transfer tube with internal grooves according to the present invention is partially developed. The heat transfer tube 1 with an inner groove is generally formed of a metal such as copper, copper alloy, aluminum, or an aluminum alloy. On its inner peripheral surface, a long fin 2 having a spiral shape having a tube axis as a spiral axis is provided. A large number of fins 2 are formed in parallel with each other, and a first groove 6 is formed between the long fins 2. Further, short fins 4 extending in parallel with the long fins 2 are respectively formed in at least some of the first grooves 6, and an opening width between the long fins 2 and the short fins 4 is larger than that of the first groove 6. The second groove 8 is formed to be narrow.

In this embodiment, the long fins 2 are formed over the entire circumference of the inner peripheral surface of the inner grooved heat transfer tube 1. The helix angle α of the long fin 2 is not limited, but is preferably 5 to 30 °. If the helix angle exceeds 30 °, the fins 2 and 4 become nearly perpendicular to the flow, and the flow blocking effect is large and the pressure loss is undesirably large. When the helix angle is less than 5 °, the fins 2 and 4 become nearly parallel to the flow, and the effect of scraping the heat transfer medium upward by the fins and the effect of improving the heat transfer efficiency are reduced.

The height H1 of the long fin 2 (see FIG. 2) is not limited in the present invention, but is preferably 0.1 to 0.3 m.
m, more preferably 0.15 to 0.25 mm. In this embodiment, since the width W2 of the first groove 6 is larger than usual and the pressure loss is reduced by the formation of the short fin 4, the height H1 of the long fin 2 is reduced by the corresponding amount. It may be higher than the attached heat transfer tube. If the length of the long fins 2 is too low, the effect of scraping up the heat transfer medium liquid is reduced, and if the length of the long fins 2 is too high, the pressure loss increases. The bottom width W1 (width in the direction perpendicular to the tube axis) of the long fin 2 is not limited, but is preferably 0.10 to 0.25 mm, and more preferably 0.15 to 0.20 mm. The ratio H1 / W1 of the height H1 of the long fins 2 to the bottom width W1 is 0.1.
It is preferable that the number is about 4 to 3. Within this range, the balance between the effect of agitating the heat transfer liquid and the pressure loss is improved.

The width W2 of the first groove 6 (the width in the direction perpendicular to the tube axis) is not limited, but is preferably 0.5-1.
2 mm, and more preferably 0.7 to 1.0 mm. When the width W2 is less than 0.5 mm, it is difficult to form the short fins 4.
Is not sufficiently broken by the short fins 4.

Although the length of the short fin 4 is not limited, in this embodiment, the length of the heat transfer tube 1 with the inner surface groove is 1/1 of the entire circumference of the inner circumferential surface.
4, and the fins 4 are provided at every 90 ° of the inner peripheral surface of the heat transfer tube 1 with the inner surface as shown in FIG.
Are formed alternately with the band-shaped region where the first groove 6 is formed. With such an arrangement, when the fins 2 and 4 are rolled on the plate material, each area divided for every 1/4 circumferential length is divided into four rolling grooves having different rolling pitches. Rolling can be performed at a time by a laminated type rolling roll in which forming rolls are stacked, and there is an advantage that manufacture of the inner grooved heat transfer tube 1 is facilitated.

As described above, in this embodiment, the length of the short fin 4 and the length of the first groove 6 are substantially equal, but the present invention is not limited to this configuration. Short fins 4
The ratio L1: L2 of the length L1 of the first groove 6 to the length L2 of the first groove 6 is not limited, but is preferably 2: 1 to 2. If either is extremely longer than the other, the effect of breaking the boundary layer is reduced. Further, the lengths of the short fins 4 may not be all constant, and the length of some short fins 4 may be different from the length of other short fins 4.

The cross-sectional shapes of the long fin 2 and the short fin 4 are triangular, isosceles triangular, triangular, semicircular, arcuate, rectangular, trapezoidal, and chamfered with rounded apex angles, respectively. Any shape such as a trapezoidal shape may be used.

In this embodiment, both ends of the short fin 4 are sharply formed in a V-shape as shown in FIG. Thereby, care is taken to prevent excessive turbulence from being generated by the fin tip. The tip shape may be symmetrical as shown in FIG.

The height H2 of the short fins 4 is not limited, but is preferably 60 to 100 times the height H1 of the long fins 2.
%, More preferably 60 to 90%. When the short fins 4 are higher than the long fins 2, when the heat dissipation fins are fixed to the outer peripheral surface of the inner grooved heat transfer tube 1 and expanded through the expansion plug into the inner grooved heat transfer tube 1, the inner surface of the tube is increased. Since the contact of the plug with the plug becomes uneven, the tube cannot be expanded uniformly. However, if the expansion is not performed, the short fins 4 may be higher than the long fins 2. The ratio H2 / W between the height H2 of the short fin 4 and the bottom width W3.
3 is preferably about 0.4 to 3. Within this range, the effect of breaking the boundary layer of the heat transfer liquid is good.

The width W4 of the second groove 8 (the width in the direction perpendicular to the tube axis) is not limited, but is preferably 0.1 to 0.2.
3 mm, more preferably 0.15 to 0.25 mm
It is. If the width W4 is less than 0.1 mm, the flow rate of the heat medium liquid flowing in the second groove 8 becomes too small, and the destruction effect of the boundary layer becomes small. Therefore, the rate at which the boundary flow formed by the short fins 4 is broken is reduced.

The diameter and thickness of the inner grooved heat transfer tube 1 are not limited, but may be any size and thickness of a general heat transfer tube, for example, an outer diameter of 6 to 10 mm and a thickness of 0.2 to 0. .3
mm. Of course, products outside this range can also be manufactured.

The method of manufacturing the inner grooved heat transfer tube 1 is not limited, but it can be manufactured efficiently by using an electric resistance welding method. In this case, a welded portion 10 extending in the tube axis direction is formed on a part of the heat transfer tube 1 with the inner surface groove in the circumferential direction as shown in FIG. The position of the welded portion 10 is not limited, and may be located at the boundary between the short fin 4 and the first groove 6 as shown in FIG. It may be located at the center of the groove 6. However, considering the ease of manufacture, it is preferable that the fin 4 is located at the boundary between the short fin 4 and the first groove 6.

In the case where the welded portion 10 is formed, at the intersection of the long fin 2 and the welded portion 10, as shown in FIG. May be formed in parallel. These non-grooved portions 7 are desirable in order to make the welding current density generated on the end face of the strip material uniform when the strip material is subjected to ERW to form a tubular shape.

It is preferable that the welding portion 10 is a ridge having a projection smaller than that of the long fin 2 so as not to hinder the expansion of the heat transfer tube 1 through the expansion plug. The cross-sectional shape of the welded portion 10 is not limited, but generally has a shape such as a semi-elliptical shape. If necessary,
The projecting welded portion 10 generated by the electric resistance welding may be removed by machining.

In this embodiment, the cross-sectional shape of the inner grooved 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. Further, it is also possible to fill a working fluid such as pure water, alcohol, chlorofluorocarbon, or a mixed solvent under reduced pressure in the inside grooved heat transfer tube 1 and close both ends of the tube to use as a heat pipe.

An example of a method of manufacturing the above-described heat transfer tube 1 with inner grooves will be described. First, the fins 2 and 4 and the grooves 6 and 6 are formed by rolling rolls while running a metal plate having a constant width.
After the formation of 8, the plate material is gradually rolled into a pipe shape by a roll forming apparatus, and the both side edges of the plate material are abutted after induction heating. As a result, the side edges are welded to form a metal tube, and the welded portion is formed as necessary to obtain the inner grooved heat transfer tube 1.

The heat transfer tube 1 with an inner groove is used, for example, incorporated in a heat exchanger such as an air conditioner or a cooler. The heat transfer liquid flowing through the tube is vaporized by heat supplied from outside the tube, It is used for the purpose of condensing the heat carrier gas flowing through the tube and releasing heat outside the tube. In each case, FIG.
Alternatively, as shown in FIG. 4, when a part of the heat medium liquid flowing in the heat transfer tube 1 with the inner surface flows along the first groove 6 between the long fins 2, the flow is caused by the tip of the short fin 4. After being divided, they flow through the narrow second groove 8 and merge again at the rear end of the shorter fin 4. In the process of this division and merging,
Since the boundary layer generated near the bottom surface of the groove 6 is peeled and broken, the heat insulation effect of the boundary layer is prevented, the heat transfer resistance between the heat medium and the metal tube is reduced, and the heat transfer of the heat transfer tube 1 with the inner surface groove is reduced. Exchange efficiency can be increased.

[Second Embodiment] FIG. 5 shows a heat transfer tube with an inner groove according to a second embodiment of the present invention. In the first embodiment, the area where the short fins 4 are formed and the area where the first grooves 6 are formed are divided every 90 ° in the circumferential direction of the inner peripheral surface of the inner grooved heat transfer tube 1. In this embodiment, short fins 4 are formed between different pairs of long fins 2 at every 90 ° in the circumferential direction of the inner peripheral surface, and the short fins 4 are arranged in a staggered manner.

According to the second embodiment, since the distribution density of the short fins 4 is uniform as compared with the first embodiment, there is an advantage that the distribution of heat quantity can be uniform. Further, even when the expansion plug comes into contact with the short fin 4 during expansion, there is an advantage that expansion can be performed relatively uniformly.

Third Embodiment FIG. 6 shows a third embodiment of the present invention. In the first embodiment, the area where the short fins 4 are formed and the area where the first groove 6 is formed are divided every 90 °. In the third embodiment, each of the areas is divided every 180 °. It is characterized by. Also in this case, the short fins 4 may be arranged in a staggered manner as in the second embodiment.

[Fourth Embodiment] FIG. 7 shows a fourth embodiment of the present invention. The fourth embodiment is characterized in that regions for forming the short fins 4 and regions for forming the first grooves 6 are alternately formed every 60 ° in the circumferential direction of the inner peripheral surface of the inner grooved heat transfer tube 1. . With such a configuration, the same effect as in the first embodiment can be obtained. Also in this case, the short fins 4 may be arranged in a staggered manner as in the second embodiment.

Although the embodiments of the present invention have been individually described above, the present invention is not limited to only the above-described embodiments. For example, the angle may be 120 °, 72 °, 45 °, or other angles other than those described above. The regions may be divided, or the components of the above embodiments may be combined with each other.

[0032]

As described above, according to the heat transfer tube with internal grooves according to the present invention, when a part of the heat medium flowing in the metal tube flows along the first groove between the long fins, The flow is divided by the leading end of the short fin, flows through the narrow second groove, and joins again at the trailing end of the shorter fin. Since the boundary layer formed near the bottom of the first groove is separated and broken in the process of the division and merging, the heat insulation effect of the boundary layer is prevented, the heat transfer resistance between the heat medium and the metal pipe is reduced, Exchange efficiency can be increased.

[Brief description of the drawings]

FIG. 1 is a partially developed plan view of a first embodiment of an internally grooved heat transfer tube according to the present invention.

FIG. 2 is a cross-sectional view of the same embodiment.

FIG. 3 is an explanatory diagram of an effect of the present invention.

FIG. 4 is an explanatory diagram of an effect of the present invention.

FIG. 5 is a partially developed plan view of an inner surface showing a second embodiment of the present invention.

FIG. 6 is a partially developed plan view of an inner surface showing a third embodiment of the present invention.

FIG. 7 is a partially developed plan view of an inner surface showing a fourth embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 heat transfer tube with internal groove 2 long fin 4 short fin 6 first groove 8 second groove 10 welded part

Claims (4)

[Claims] 1. A large number of long fins (2) having a helical shape with the tube axis of the metal tube (1) as a helical axis are formed in parallel on the inner peripheral surface of the metal tube (1). (2)
A first groove (6) is formed therebetween, and a short fin (4) extending in parallel with the long fin (2) is formed in at least a part of the first groove (6). A second groove (8) having a smaller opening width than the first groove (6) is provided between the long fin (2) and the short fin (4).
A heat transfer tube with an inner surface groove, wherein a heat transfer tube is formed. 2. The height of the short fins (4) from the inner peripheral surface of the metal tube is 60 to 100% of the height of the long fins (2) from the inner peripheral surface of the metal tube. The heat transfer tube with an inner groove according to claim 1. 3. A part of the inner peripheral surface of the metal tube (1)
The heat transfer tube with an inner groove according to claim 1 or 2, characterized in that a weld (10) extending in the tube axis direction is formed, and the long fin (2) is divided by the weld. 4. The heat transfer tube with an inner groove according to claim 1, wherein an inclination angle of the long fin (2) with respect to an axial direction of the metal tube is 5 to 30 °.