JP4630005B2 - Internal grooved tube and manufacturing method thereof - Google Patents

Description

  The present invention relates to an internally grooved tube used as a heat transfer tube or a heat pipe, and a method for manufacturing the internally grooved tube, and more particularly to a condensation-promoting internal grooved tube and a method for manufacturing the same when using a non-azeotropic refrigerant.

  2. Description of the Related Art Heat transfer tubes for air conditioners such as room air conditioners are used in which a large number of fins (grooves between fins) are spirally processed on the inner surface. It is well known that heat transfer performance of a heat transfer tube is improved when fins (grooves) having a higher (deeper) and larger helix angle are processed as densely as possible on the inner surface. However, if a fin having a large fin height and spiral angle (lead angle) is processed on the inner surface, the heat transfer performance is improved, but the pressure loss in the pipe increases, and the energy efficiency is lowered due to an increase in the load on the compressor. .

In order to solve the above-mentioned problem, a large number of spiral fins having narrow openings at the top and groove-like cavities at predetermined intervals are processed on the inner surface of the pipe, and pressure loss can be suppressed by the cavities. It has been proposed (the cavity depth is 0.25 to 1.0 times the fin height. See Patent Document 1 below).
The inner surface grooved pipes each have a plurality of grooved plugs rotatably inserted into the raw pipes, and by pulling out the raw pipes, a large number of primary grooves having a rectangular cross section are formed on the inner surface of the pipe. Is manufactured by processing a large number of secondary grooves having a triangular cross section so as to intersect and spiral. That is, when the secondary groove is processed on the inner surface of the pipe, the fin by the primary groove is crushed to form a fin between the secondary grooves, and the primary groove portion is pressure-deformed and the fin between the secondary grooves As described above, the dovetail cavity is formed.
JP 7-12482 A

However, the refrigerant in the inner grooved tube finally condenses at the top of the fins when condensing. However, like the inner grooved tube, the refrigerant is formed in a spiral shape and has a fin cavity, and each fin has a groove shape. A discontinuity (opening) is formed at the position of the primary groove at the top of the tube, and the refrigerant does not condense at this discontinuity, so the condensing performance is reduced accordingly. Mixed refrigerants (azeotropic refrigerants, non-azeotropic refrigerants) are used for room air conditioners and the like, but the tendency of the above-mentioned reduction in condensation performance becomes particularly noticeable when non-azeotropic refrigerants are used.
In the manufacturing method, it is difficult to match the groove bottom of the primary groove and the groove bottom of the secondary groove (cavity depth = fin height), and usually the primary groove is completely crushed during the secondary groove processing, Since the bottom level of the cavity is higher than the bottom level of the secondary groove (a step is generated between the bottom of the cavity and the secondary groove), the effect of suppressing the pressure loss is small.

  The problem to be solved by the present invention is to provide an internally grooved tube having higher condensation performance and greater pressure loss suppression effect, and a method for producing the same.

In order to solve the above-mentioned problems, the internally grooved tube according to the present invention has firstly a plurality of fins having a predetermined lead angle β in the length direction on the inner surface and having a triangle or a triangle-like fin at a predetermined interval. Each fin has a tunnel-like portion at a predetermined interval so as to intersect with the fin , and the tunnel-like portion and the top of the fin are not interrupted, and the top of the fin passes through the joint of the top of the tunnel-like portion. with continuous, bottom and bottom surface of the tunnel portion in the groove between the fins is the feature that the surface of the same level to be continuous.
Second, the tunnel portion is formed along the length of the tube, the lead angle β is 40 to 70 °, and the bottom width of the tunnel portion is 0.4 to 1 of the fin height h. It is characterized by being doubled.

The method of manufacturing an internally grooved tube according to the present invention is a trapezoid having a rectangular or nearly rectangular cross section having a predetermined angle β1 with respect to the length direction on one surface of the metal strip while feeding the metal strip in a certain direction. A step of processing a number of primary fins that are interrupted at predetermined intervals through groove-shaped breaks in the crossing direction, and a state in which each of the primary fins has a triangular or triangular-like shape in cross section. and, together with the top one another before and after the fins of each discontinuity and its is continuous through the seam, the discontinuity is formed like a tunnel extending through the fins in the cross direction, the bottom surface and the tunnel of the grooves between the fins Forming the fins shaped by pressurizing and deforming into a state where the bottom surface of the shaped part is a continuous surface of the same level, and forming the metal strip into a tubular shape with the fin processed surface as the inner surface, welding It is characterized by a step of forming tube Te.

According to the internally grooved tube according to the present invention, a large number of fins spirally formed on the tube inner surface have tunnel-shaped portions at a predetermined interval. Therefore, the lead angle θ of the fin spiral is increased to reduce the heat transfer area. Even when it is further enlarged, the refrigerant smoothly flows in the downstream direction through the tunnel-like portion. Therefore, pressure loss can be sufficiently suppressed when a non-azeotropic refrigerant is used.
In addition, in the pipe, two refrigerant flows, one flowing along the fins and the other flowing in the downstream direction through each tunnel-like part, are created, effectively exhibiting the turbulence effect and improving the heat transfer performance, and the top of the fin is interrupted Condensation performance is not deteriorated because it is continuous.
According to the method for manufacturing an internally grooved tube according to the present invention, the internally grooved tube according to the present invention can be manufactured smoothly.

FIG. 1 is a partially enlarged perspective view showing a state in which an internally grooved tube according to an embodiment of the present invention is developed. A cross section having a predetermined lead angle β with respect to the length direction is triangular on the inner surface of a metal tube. Moreover, a large number of fins 1 similar to triangles are formed at predetermined intervals, and grooves 2 having a substantially inverted trapezoidal shape are formed between the fins 1.
Each fin 1 is formed with a tunnel-like portion 10 that crosses the fin and penetrates in the length direction of the tube at a predetermined interval. Since 10 is a tunnel-like portion, its bottom surface is a surface that is substantially continuous with the bottom of the groove 2, and the top portion of the fin 1 is continuous through a seam.
The material of the tube can be copper, a copper alloy, an aluminum alloy, a steel material, or other materials having excellent thermal conductivity, but oxygen-free copper, phosphorus deoxidized copper, or tough pitch copper is preferably used.

According to the inner surface grooved tube of the above embodiment, the numerous fins 1 formed in a spiral shape on the inner surface of the tube have the tunnel-shaped portions 10 at a predetermined interval, so that the spiral lead of the fin 1 is increased in order to increase the heat transfer area. Even if the angle θ is increased, the condensed refrigerant smoothly flows in the downstream direction through the tunnel-like portion 10. Therefore, pressure loss can be sufficiently suppressed when a non-azeotropic refrigerant is used.
Further, in the pipe, two flows of the refrigerant flowing along the fin 1 and the refrigerant flowing in the downstream direction through the respective tunnel-shaped portions 10 are generated, and the heat transfer performance is improved by efficiently exhibiting the turbulent flow effect. The top is continuous without interruption, and at the end of the condensation, the refrigerant condenses at each part of the top of the fin 1 so that the condensation performance does not deteriorate.

The manufacturing method of the internally grooved tube according to the above embodiment will be described below with reference to FIGS.
2 is a partially enlarged perspective view of a metal strip processed with a primary fin, FIG. 3A is a schematic plan view of a primary processing roll, and FIG. 2B is a schematic plan view of a secondary processing roll. 4 and 4 are partially enlarged cross-sectional views (cross-sections perpendicular to the fins) in the state where the primary fin is processed on the metal strip, and FIG. 5 is a portion where the primary fin of the metal strip is formed into a finished fin. It is an expanded section (cross section orthogonal to a fin) figure.

As shown in FIG. 3A and FIG. 4, the primary processing roll 3 includes a primary work roll 3 a that processes primary fins on the upper surface of the metal strip 1 a, and the primary work roll 3 a has a predetermined rolling force. And a primary smoothing roll 3b (FIG. 4) having a smooth outer peripheral surface in parallel with the upper part.
The primary work roll 3a includes a grooved roll portion (grooved roll piece) 30 in which a large number of primary grooves 30a having a predetermined lead angle β1 are formed on the outer peripheral surface at predetermined intervals, and an outer diameter of the grooved roll portion 30. A smooth roll portion (smooth roll piece) 31 having the same outer diameter as the groove bottom outer diameter and a smooth outer peripheral surface and a small width (thickness) is combined in a coaxial manner in close contact with each other.
The primary groove 30a has a rectangular cross section, but may have a trapezoidal shape close to a rectangle.

As shown in FIG. 3 (b) and FIG. 5, the secondary work roll includes a secondary work roll 4a for pressing and shaping the primary fin formed on the metal strip 1a, and a secondary work roll. A secondary smoothing roll 4b having a smooth outer peripheral surface with which the work roll 4a comes into contact with the upper part in parallel with a predetermined rolling force is provided.
A large number of secondary grooves 40 having the same lead angle β1 as the lead angle β1 of the primary work roll 3a are formed on the outer peripheral surface of the secondary work roll 4a.
The cross-sectional shape of the secondary groove 40 is triangular or similar to a triangle, and the groove bottom width w2 is the same as the groove bottom width w2 of the primary groove 30a, but the groove depth d is the groove depth of the primary groove 30a. The required amount is deeper than d1. That is, the depth d of the secondary groove 40 is designed such that the cross-sectional area of the secondary groove 40 is slightly smaller than or equal to the cross-sectional area of the primary groove 30a. The groove pitch p (the distance from the center of the adjacent groove to the center) of the primary groove 30a and the secondary groove 40 is the same.
The groove bottom width w2 of the secondary groove 40 may be slightly larger than the groove bottom width w2 of the primary groove 30a.

  As shown in FIG. 3, when the metal strip 1a is rolled, the metal strip 1a is rolled between the upper and lower rolls 3a, 3b of the primary processing roll 3 that rotates along the feeding direction while feeding the metal strip 1a of a predetermined width. The primary fin 11 having the same shape and size as the primary groove 30a of the primary work roll 3a is transferred and processed on the upper surface of the metal strip 1a as shown in FIGS. At this time, each primary fin 11 has a predetermined interval along the length direction of the metal strip 1a corresponding to the thickness of the smooth roll portion 31 of the primary work roll 3a as shown in FIG. The break 12 having a bottom surface at the same level as the groove bottom is processed. That is, the upper surface of the metal strip 1a has a predetermined lead angle β with respect to the length direction of the strip as shown in FIG. 2, has a rectangular cross section, and has the same length L1 as the thickness of the smooth roll portion 31 ( A large number of primary fins 11 are formed which are interrupted via the discontinuous portion 12 having a thickness of the smooth roll portion 31.

A secondary processing roll 4 that rotates along the feeding direction as shown in FIG. 3 is installed downstream of the first processing roll 3 in the feeding direction, and the metal strip 1a on which the primary fins 11 are processed. Is rolled between the secondary work roll 4a and the secondary smooth roll 4b. At this time, the secondary processing roll 4 is arranged so that the secondary fins 40 of the primary fin 11 and the secondary work roll 4a coincide. Further, the metal strip 1a is set so that each primary fin 11 enters the corresponding secondary groove 40 by the rotation of the rolls 4a and 4b, and the rolling of the metal strip 1a is resumed.
When the metal strip 1a is rolled by the rolls 4a and 4b of the secondary processing roll 4, each primary fin 11 has a corresponding secondary groove 40 as shown in FIG. And a part of the material at the top portion of the primary fin 11 moves in the direction of each discontinuous portion 12 and is pressed and deformed so that the fin top portions are continuous with each other. By the shaping by the pressure deformation, the continuous fins 1 having the tunnel-like portions 10 are processed at predetermined intervals as shown in FIG.

A forming roll group (not shown), a squeeze roll, and an induction heating coil are sequentially installed downstream of the second processing roll 4 in the feeding direction, and the metal strip 1a on which the shaped fins 1 are processed is formed by the forming roll group. After sequentially forming into a tubular shape so that the fin forming surface becomes the inner surface, both side edges are sequentially abutted by a squeeze roll, and the abutted portion is sequentially welded by an induction heating coil to produce a pipe.
After pipe making, the weld bead is cut and then the pipe is blanked and finished.
In the internally grooved tube manufactured as described above, the bottom width w1 of the tunnel-like portion 10 is substantially the same as the length L1 of the discontinuous portion 12 in the primary fin 11.

The tube size varies depending on the application, but is generally about 3 to 15 mm in outer diameter and about 0.2 to 1.0 mm in groove bottom thickness.
In addition to increasing the heat transfer area in proportion to the size of the lead angle β of the fin 1, the refrigerant liquid film in the groove is sufficiently agitated to reduce the concentration difference at the gas-liquid interface of the non-azeotropic refrigerant and diffuse Condensation heat transfer coefficient is improved by reducing resistance and thermal resistance. If the lead angle β is less than 40 °, the heat transfer area cannot be increased sufficiently, and the condensation heat transfer coefficient is insufficient due to the lower stirring of the refrigerant liquid film. On the other hand, if it exceeds 70 °, the pressure loss increases and the energy efficiency of the compressor or the like decreases. Therefore, the lead angle β of the fin 1 is preferably 40 to 70 °, more preferably 45 to 55 °.

Although depending on the tube size, if the fin height h is less than 0.10 mm, sufficient heat transfer performance cannot be obtained, and if it exceeds 0.35 mm, fin cracking is likely to occur when the tube is expanded for incorporation into the air conditioner. Therefore, the fin height h is preferably in the range of 0.10 to 0.35, and more preferably 0.15 to 0.30 mm.
If the fin width w is less than 0.05 mm, the fin strength is insufficient and fin cracking occurs during rolling. If the fin width w exceeds 0.20 mm, the tunnel-shaped portion 10 may not be processed during shaping. Accordingly, the fin width w is preferably 0.05 to 0.20 mm, and more preferably in the range of 0.10 to 0.15 mm.

Using the primary processing roll and the secondary processing roll having the following configuration, a number of fins 1 having tunnel-shaped portions 10 having different bottom widths w1 are processed on a metal strip 1a having a constant width of an aluminum alloy. Each sample strip 1a was formed into a tubular shape, and a test tube according to an example in which the tube was formed by welding was manufactured.
・ Primary work roll of primary processing roll Groove roll part × 5
Groove lead angle β1 = 40 °
Groove depth d1 = 0.20mm
Groove bottom width w2 = 0.13
Groove shape = rectangular cross section Groove pitch = constant Smooth roll part x 4
Thickness L1 (bottom width w1 of tunnel-shaped portion 10) = change in 0.05 mm increments in the range of 0.05 to 0.30 mm. Secondary work roll of secondary processing roll Groove lead angle β1 = 40 °
Groove depth d = 0.25mm
Groove bottom width w2 = 0.13
Groove shape = Triangular section Groove pitch = Same as primary work roll On the other hand, using a processing roll in which the next work roll is combined with a smooth roll, a large number of metal strips of the same material with the same width and no tunnel-like part A sample tube with an inner groove was manufactured as a comparative sample in which the fin was processed, the metal strip was formed into a tubular shape, and the tube was formed by welding.
Groove lead angle β1 = 40 °
Groove depth d1 = 0.25 mm
Groove bottom width w2 = 0.13
Groove shape = Triangular section Groove pitch = Same as primary work roll

The heat transfer coefficient and pressure loss at a refrigerant flow rate of 300 kg / m ² s were measured for the seven types of test tubes manufactured as described above, and the heat transfer coefficient and pressure loss of the test tube of the comparative sample were 100 respectively. Table 1 shows the heat transfer rate ratio and the pressure loss ratio.

As shown in Table 1, when the bottom width w1 of the tunnel-shaped portion 10 is less than 0.10 mm, the heat transfer coefficient ratio and the pressure loss ratio are not significantly different from the test tube of the comparative sample, and the bottom width w1 exceeds 0.25 mm. And the heat transfer coefficient tended to decrease.
Therefore, the bottom width w1 of the tunnel-like portion 10 is preferably in the range of 0.4 to 1 times the fin height h (2 / 5h ≦ w1 ≧ 1h).

  In the said embodiment, although demonstrated on the assumption that the inner surface grooved tube which concerns on this invention was used as a heat exchanger tube for heat exchangers, such as a room air conditioner, the inner surface grooved tube which concerns on this invention is also used as a heat pipe. be able to.

It is a partial expansion expansion perspective view showing one embodiment of an internally grooved pipe concerning the present invention. It is the partial expansion perspective view which illustrated the metal strip after primary groove processing. BRIEF DESCRIPTION OF THE DRAWINGS The outline of the processing roll for manufacturing the inner surface grooved pipe | tube which concerns on this invention is shown, (a) A figure is a schematic plan view which shows a primary processing roll, (b) A figure is a secondary processing roll. It is a schematic plan view which shows. It is a partial expanded sectional view which shows the state which is processing the primary fin to the metal strip with the primary processing roll. It is a partial expanded sectional view which shows the state which pressure-shapes the primary fin of a metal strip with the 2nd process roll.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fin 10 Tunnel-shaped part 11 Primary fin 12 Discontinuous part 1a Metal strip 2 Groove 3 Primary processing roll 3a Primary work roll 3b Primary smooth roll 30 Grooved roll part 31 Smooth roll part 30a Primary groove 4 Secondary process Roll 4a Secondary work roll 4b Secondary smooth roll 40 Secondary groove

Claims (3)

Section with a predetermined lead angle β to the longitudinal direction on the inner surface has a plurality of fins of triangular or triangle similar to the predetermined distance, wherein each fin tunnel portion at predetermined intervals in a state that intersects with the fin the not interrupted chromatic vital the tunnel-like portion and the top of the fin top of fins with continuous through seam of the tunnel-like portion top, bottom and bottom surface of the tunnel portion in the groove between the fin is continuous An internally grooved tube characterized by having the same level surface . The tunnel-like portion is formed along the length direction of the tube, the lead angle β is 40 to 70 °, and the bottom width of the tunnel-like portion is 0.4 to 1 times the fin height h. The internally grooved tube according to claim 1. While feeding the metal strip in a fixed direction, the cross section having a predetermined angle β1 with respect to the length direction on one surface of the metal strip is a rectangle or a trapezoid close to a rectangle, and groove-shaped breaks in the intersecting direction are formed at predetermined intervals. a step of processing a large number of primary fins at predetermined intervals intermittently through, each of said primary fins, the state in which its cross section exhibits a triangular or triangle like shape, and the top portion of the front and rear fins of the discontinuity and its Mutually continuing through the seam , the discontinuity is formed in a tunnel-like part penetrating the fins in the crossing direction, and the bottom surface of the groove between the fins and the bottom surface of the tunnel-like part is a continuous level surface. A step of forming a fin shaped by being pressure-deformed into a state, and a step of forming the metal strip into a tubular shape with the fin processing surface as an inner surface and welding the butt portions on both sides to form a pipe. When That method of inner grooved tube.

Images