JP2003294386A - Internally grooved heat transfer pipe and its manufacturing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internally grooved heat transfer pipe excellent in the property of contact between the outer surface of the pipe and fins and in heat- transfer performance, and also to provide a manufacturing apparatus for the pipe. <P>SOLUTION: The internally grooved heat transfer pipe has spiral grooves and/or crossing grooves formed on its inner surface. Sinusoidal, periodical projecting and recessed parts formed on the outer surface of the pipe have an average interval of 0.8 mm or more as measured over 5 mm in the direction of the pipe axis and have a height difference of not more than 5 μm between the apex of the highest projecting part and the bottom of the lowest recessed part. The average surface roughness Ra of the pipe outer surface measured in the direction of the pipe axis is not more than 0.4 μm, with the maximum surface roughness Rmax being 4 μm or less. Further, when grooves are transferred onto the inner surface of the heat transfer pipe by means of drum-shaped rolling rolls, the surface roughness Ra of the rolling roll in its circumferential direction and in the direction of the roll axis is 0.2 μm or less, with its maximum surface roughness Rmax being 1.5 μm or less. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seamless inner grooved heat transfer tube having spiral grooves and / or intersecting grooves formed on the inner surface of the tube, and a manufacturing apparatus therefor.

[0002]

2. Description of the Related Art In a heat exchanger, heat is exchanged using a heat transfer tube made of copper or a copper alloy. In this case, in order to improve the heat transfer performance, the inner surface of the heat transfer tube has a spiral shape and / or
Or, a cross-shaped groove is formed. As this inner surface grooved heat transfer tube, a grooved plug is arranged on the inner surface of the raw tube, and the raw tube is pressed against the grooved plug from the outside of the tube by a rolling ball or a rolling roll to transfer the groove shape to the inner surface of the tube. There is a seamless pipe manufactured by the above, or a welded pipe manufactured by transferring the groove shape to the upper surface of a strip-shaped base plate, then rolling the strip in the width direction of the strip and welding both ends.

In this case, although the welded pipe is easy to form grooves of various shapes, it is manufactured by rolling a copper or copper alloy strip having the grooves on one side thereof in the width direction and welding. However, the manufacturing process is complicated and the productivity is low. On the other hand, seamless tubes have the advantage of high productivity.

FIG. 3 is a diagram showing a conventional seamless pipe manufacturing apparatus. After being annealed, the blank 18 is reduced in diameter by the diameter reducing die 11, pressed by the rolling balls, and then reduced in diameter by the diameter adjusting die 17 to obtain the product diameter. Inside the tube 18, the diameter reduction die 11
Floating plug 1 at a position that matches the placement position of
2 are arranged, and the maximum diameter of the floating plug 12 is larger than the minimum diameter of the diameter-reducing die 11. Therefore, the floating plug 12 has a force acting in the direction of the arrow due to the frictional force generated by the element pipe 18 that is pulled out in the direction of the arrow, and is blocked by the diameter-reducing die 11 to be locked at that position.

On the other hand, a grooved plug 13 is connected to the floating plug 12 via a plug shaft 14, and the grooved plug 13 stops at a position aligned with the position of the rolling ball 15. There is. Rolled ball 1
5 is rotationally driven so as to revolve in the circumferential direction of the pipe while rolling on the outer surface of the pipe, and the rolling pipe 15 presses the raw pipe 18 toward the grooved plug 13 so that the outer surface of the grooved plug 13 is The groove shape is transferred to the inner surface of the tube, and the inner surface groove 16 is formed.

[0006]

However, the inner surface grooved tube pressed by the rolling ball 15 has a spiral ball shape on the outer surface of the tube because the rolling ball is pulled out while rotating the outer surface of the tube. There is a drawback that passage marks are formed. The ball passage mark has a sinusoidal surface shape with a specific period and depth in the tube axis direction.

This heat transfer tube is bent into a U-shape and then inserted into holes provided in a plurality of flat plate-shaped aluminum fins, a mandrel is inserted into the tube, and the tube is expanded by the mandrel. The heat transfer tube and the fin are fixed.

In this case, if the above-mentioned ball passage mark is present on the outer surface of the heat transfer tube, it is formed between the outer surface of the copper tube and the aluminum fin when the heat transfer tube is expanded to make close contact with the aluminum fin. As a result, the volume of the created gap becomes large, which causes a decrease in heat transfer performance.

The present invention has been made in view of the above problems, and provides an inner grooved heat transfer tube having good contact property between the outer surface of the tube and the fins and excellent heat transfer performance, and an apparatus for manufacturing the same. With the goal.

[0010]

A heat transfer tube with an inner surface groove according to the present invention is a heat transfer tube with an inner surface groove having a spiral groove and / or a cross groove formed on the inner surface of the tube. The average pitch when measured over 5 mm in the tube axis direction is 0.8 mm or more, and the height difference between the top of the highest convex portion and the bottom of the lowest concave portion is 5 μm or less. To do.

In this heat transfer tube with inner groove, the average surface roughness Ra of the outer surface of the tube measured in the tube axis direction is 0.4 μm or less,
The maximum surface roughness Rmax is preferably 4 μm or less.

The apparatus for manufacturing an inner grooved pipe according to the present invention comprises a diameter-reducing die for reducing the diameter of the elemental tube, and a rotation axis of the elemental tube located downstream of the diameter-reducing die in the flow direction of the elemental tube. At least one pair of drum-shaped rolls arranged perpendicularly to the tube axis, and a floating plug that is stopped by being locked by the diameter-reducing die inside the raw tube at a position that matches the position of the diameter-reducing die. A grooved plug that is connected to a floating plug through a plug shaft and that is arranged inside the element tube at a position that matches the arrangement position of the hourglass-shaped roll. In an apparatus for manufacturing an inner grooved tube for pressing a spiral groove and / or a cross groove to the inner surface of the raw tube by pressing it toward an attached plug, the surface roughness of the roll in the circumferential direction and the roll axial direction of the drum-shaped roll. Ra is 0.
It is characterized in that it is 2 μm or less and Rmax is 1.5 μm or less.

In the present invention, since the outer surface of the tube is rolled by the roll in the drawing direction of the tube, the passing mark of the ball unlike the case of ball rolling is not formed. Further, in the present invention, the surface profile of the outer surface of the tube has an average pitch of sinusoidal periodic unevenness of 0.8 mm or more when measured over the tube axis direction of 5 mm, and the height of the highest convex portion is Since the difference with the lowest concave portion is 5 μm or less, the outer surface of the tube is extremely smooth in the tube axis direction. Therefore, when the heat transfer tube is inserted through the fin hole and expanded,
Since the gap between the heat transfer tube and the fin is small and the fins are uniform, the contact between the heat transfer tube and the fin is high, and excellent heat transfer performance can be obtained.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.
A detailed description will be given with reference to the accompanying drawings. FIG. 1 is a view showing an apparatus for manufacturing a heat transfer tube with an inner groove according to the present invention. The diameter-reducing die 2, a pair of rolling rolls 3, the diameter-adjusting die 4, a pair of rolling rolls 5, and the diameter-adjusting die 6 are arranged in this order in the drawing direction of the tube 1, and the inside of the tube 1 , A floating plug 7 is arranged at a position aligned with the diameter reducing die 2, a grooved plug 9a is arranged at a position aligned with the rolling roll 3, and a grooved plug 9c is aligned at a position aligned with the rolling roll 5.
Are arranged. On the peripheral surfaces of the grooved plugs 9a and 9c,
Grooves 9b and 9d are formed, respectively. The floating plug 7, the grooved plug 9 a, and the grooved plug 9 c are connected by a plug shaft 10. The floating plug 7 includes a large-diameter portion 7a and a reduced-diameter portion 7b. Since the large-diameter portion 7a has a larger diameter than the minimum-diameter portion of the diameter-reducing die 2, the raw pipe 1 to be pulled out Due to the frictional force, a force is applied to the floating plug 7 in the pulling-out direction of the raw tube 1, and the diameter reduction die 2 prevents the floating plug 7 from passing therethrough, so that the floating plug 7 stays at the position of the diameter reduction die 2. As a result, the grooved plugs 9a and 9c connected to the floating plug 7 stop at the positions of the rolling rolls 3 and 5, respectively. A pair of rolling rolls 3
And the pair of rolling rolls 5 are arranged with their rotation axes orthogonal to the tube axis, but the rotation axis of the rolling roll 3 and the rotation axis of the rolling roll 5 are 0 to 90 degrees relative to each other. They intersect at an angle of °. In the illustrated example, the rotation axis of the rolling roll 3 and the rotation axis of the rolling roll 5 are orthogonal to each other. Therefore, the base pipe 1 has a portion subjected to reduction by the rolling rolls 3 and a portion subjected to reduction by the rolling rolls 5,
The center angle is deviated by about 90 ° in the pipe circumferential direction. This allows
The raw tube 1 is subjected to reduction by the rolling rolls in almost the entire area in the circumferential direction of the tube, and grooves are transferred to the inner surface in almost the entire area in the circumferential direction.

However, when the groove is formed on the inner surface of the raw tube 1, the grooved plugs 9a and 9c are rotatably supported with respect to the plug shaft 10, but the inner surface of the tube formed by the rolling by the rolling roll 3 is pressed. Since the groove of (1) passes through the groove 9b of the grooved plug 9a, the elemental tube 1 receives a twisting force in the direction of rotation in the tube circumferential direction. Therefore, when the rolling roll 3 receives the reduction (or the portion that does not receive the reduction) reaches the position where the rolling roll 5 is arranged, it is displaced at a slight central angle in the pipe circumferential direction. Therefore, it is preferable that the rotation axis of the rolling roll 5 and the rotation axis of the rolling roll 3 are not orthogonal to each other, but are deviated from the direction orthogonal to each other by the deviation. That is, the rotation axis of the rolling roll 5 coincides with the portion (or the portion that does not undergo reduction) by the rolling roll 3 that does not undergo reduction by the rolling roll 5 (or the portion that floats the reduction). As described above, it is preferable to shift the element tube by the angle of twist with respect to the direction orthogonal to the direction of the rotation axis of the rolling roll 3.

The diameter-adjusting die 4 has a function of returning the element tube 1 to a perfect circle when the element tube 1 is pressed by the rolling roll 3 and flattened into an elliptical shape.

In this way, the inner diameter grooved pipe 1a having a product diameter of a predetermined size and having the groove 1b formed on the inner surface of the pipe is manufactured by the diameter adjusting die 6.

Although the manufacturing apparatus shown in FIG. 1 has two sets of rolling rolls 3 and 5, and grooved plugs 9a and 9c provided at positions aligned with the rolling rolls of each set, If it is not necessary to form grooves on almost the entire surface of the pipe, or if it is not necessary to form cross grooves in the pipe, one pair of rolling rolls may be provided.

Thus, in the present invention, the surface roughness Ra of the surface of the rolling rolls 3, 5 rolling on the raw pipe 1 is 0.2 in both the circumferential direction of the roll and the axial direction of the roll.
μm or less.

By using the rolling rolls 3 and 5 as described above and forming a groove on the inner surface of the tube by the apparatus shown in FIG. 1, the surface profile of the outer surface of the tube can be made smooth. That is, the uneven shape on the outer surface of the pipe is 5 m in the axial direction of the pipe.
When measured over m, the average pitch of sinusoidal periodic irregularities becomes 0.8 mm or more, and fine irregularities disappear. Also, the uneven shape of the outer surface of the pipe is 5 mm in the pipe axis direction.
When measured over, the height difference between the top of the highest convex portion and the bottom of the lowest concave portion is 5 μm or less. Therefore, the unevenness of the outer surface of the tube is extremely small, and the smooth outer surface can be obtained.

Further, it is preferable that the surface roughness Ra of the outer surface of the tube measured in the tube axis direction is 0.4 μm or less and the Rmax is 4 μm or less.

Fine irregularities (surface roughness) on the outer surface of the pipe after rolling
Is the surface roughness of the raw pipe before rolling, the surface roughness of the rolling roll,
It is affected by the material of rolling rolls, rolling reduction, lubricating oil, etc. This surface roughness Ra is 0.4 μm or less and Rmax is 4
If the condition of not more than μm is not satisfied, the insertion resistance into the aluminum fin (damage of the fin, deterioration of workability, etc.) and the heat transfer performance are likely to be deteriorated. Therefore, Ra ≦ 0.
It is desirable that 4 μm and Rmax ≦ 4 μm. More preferably, Ra ≦ 0.3 μm, Rmax ≦ 3.5 μm
Is.

When the copper or copper alloy base pipe is rolled with a drum-shaped roll, fine projections on the outer surface of the copper or copper alloy base pipe are flattened by the rolling roll, and the uneven profile on the surface of the rolling roll is flat. Transferred to the surface of the tube. At this time, in order to reduce the surface roughness of the outer surface of the raw pipe, it is necessary that the surface roughness of the rolling roll is small. That is, when the surface roughness Ra of the rolling roll in the roll circumferential direction and the roll axial direction exceeds 0.2 μm, the surface roughness Ra of the rolled raw pipe is Ra.
Is difficult to be 0.4 μm or less. Therefore, the surface roughness Ra of the roll in the roll circumferential direction and the roll axial direction is
Needs to be 0.2 μm or less. Preferably, the surface roughness Ra of the roll is 0.15 μm or less.
The Rmax on the roll surface is preferably 1.5 μm or less, more preferably 1 μm or less.

The rolling roll is made of cemented carbide (JC
ISV1 etc.), HRC60 or higher SK3, SKD11 or other steel material, or Shore hardness 100 or higher ceramics (sialon, silicon nitride, etc.) and the like.

[0025]

EXAMPLE A heat exchanger using the heat transfer tube with internal groove according to the example of the present invention will be manufactured, and the result of comparison of its heat transfer performance with a comparative example outside the scope of the present invention will be described. The heat transfer performance was evaluated by the following steps. Grooving rolling process → LWC (level wound coil) winding process → Annealing (inert gas atmosphere) process → Straightening and cutting process → Hairpin bending process → Heat exchanger assembly (insertion into aluminum fin, expansion, brazing) Process) → airtightness test → heat transfer performance measurement test In the process of assembling this heat exchanger, a copper or copper alloy tube with inner groove is cut to a predetermined length from the annealed LWC, and pitch 2
A U-shaped tube was manufactured by bending a hairpin with 1 mm. Next, insert a hairpin-bent U-shaped tube into a number of aluminum fins arranged in parallel, and in order to improve the adhesion between the aluminum fin and the copper tube, the abacus ball shape that is slightly larger than the minimum inner diameter inside the tube is inserted into the copper tube. Insert a tube expansion bullet to expand the tube inner diameter (tube expansion), and braze a U-bend tube (U-shaped joint tube) to the open end of the hairpin so that it has a specified piping path, and then install the heat exchanger. I made it. The dimensions of this heat exchanger are 600 mm × 230 mm, the number of rows is 2 and the number of stages is 12.

The aluminum fin has a plate thickness of 0.11 m.
m JIS A1100-H26 aluminum alloy plate,
Normal precoat (silica surface treatment) and highly slippery precoat (lubricant-containing silica surface treatment) were carried out, and then the fin shape was made into a corrugated shape, and by drawless molding, 1 row 10 steps, color height 1.20 mm. Molded. The hole diameter of the collar is 7.20 mm in diameter.

The heat transfer performance was measured under the measurement conditions shown in Table 1 below. The measurement result of the heat transfer performance is shown as an index with the heat transfer performance of Example 3 being 1. Comparative Example 5 is a heat exchanger (conventional example) manufactured by using a seamless rolled tube (seamless tube manufactured by rolling balls). The refrigerant R410A is a non-azeotropic mixed refrigerant.

[0028]

[Table 1]

The surface shape of the rolling roll is shown in Table 2 below.
The surface irregularities of the obtained inner grooved tube are shown in Table 3 below,
The measurement results of the evaporation performance and the condensation performance are shown in Table 4 below.

[0030]

[Table 2]

[0031]

[Table 3]

[0032]

[Table 4]

2A and 2B are a chart and a chart showing the uneven pitch of the surface in Example 1 and Comparative Example 5, respectively. In this chart, the copper tube is fixed so that the tube axis is horizontal, the probe of the stylus type surface roughness meter is scanned in contact with the outer surface of the heat transfer tube, and the displacement of the probe is recorded. is there. The horizontal axis of the chart is the scan length of the probe, and one scale (1 mm) corresponds to 0.02 mm, and the horizontal direction is magnified 50 times. On the other hand, the vertical axis is the vertical position of the probe, and one scale (1 mm) is 0.5 μm.
And is enlarged 2000 times in the vertical direction.

As shown in FIG. 2, the outer surface of the heat transfer tube manufactured by the conventional rolling balls has unevenness with sine wave undulations, and its pitch is 0.7 mm as shown in Table 4. is there. On the other hand, Example 1 of the present invention
No such sinusoidal unevenness is observed. Further, the roughness Ra of the surface of the rolling roll of Examples 1 to 3 of the present invention is 0.2 μm or less, the uneven pitch of the outer surface of the heat transfer tube cannot be measured, and the maximum height difference between the convex portion and the concave portion is 5 μm or less. Yes, the surface roughness Ra of the heat transfer tube is 0.4 μm or less, Rmax
Since it is 4 μm or less, by using this heat transfer tube, a heat exchanger having excellent evaporation performance and condensation performance can be obtained.

[0035]

As described above, according to the present invention,
Since the unevenness of the outer surface of the heat transfer tube is small and there is no minute undulation, the gap between the heat transfer tube and the fin when the heat transfer tube is inserted into the fin can be eliminated or extremely reduced. As a result, the heat transfer performance of the heat exchanger can be improved.

[Brief description of drawings]

FIG. 1 is a view showing an apparatus for manufacturing a heat transfer tube according to an embodiment of the present invention.

FIG. 2 is a chart showing surface irregularities.

FIG. 3 is a view showing an apparatus for manufacturing a conventional heat transfer tube by rolling balls.

[Explanation of symbols]

1, 18: Tube 2, 11: Diameter reduction die 3, 5: Rolling roll 7, 12: Floating plug 9a, 9c, 13: grooved roll 15: Rolled ball

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kiyonori Ozeki             65 Hirasawa, Hadano City, Kanagawa Prefecture Kobe, Inc.             Steel Works Hadano Factory (72) Inventor Hideki Iwamoto             65 Hirasawa, Hadano City, Kanagawa Prefecture Kobe, Inc.             Steel Works Hadano Factory F term (reference) 3H111 AA01 BA04 CB02 CB14 CB22                       CB29 DB09 EA10                 4E028 HA02 HA07                 4E096 EA04 EA18 FA03 FA16 FA23                       FA24

Claims (3)

[Claims] 1. In a heat transfer tube with an inner groove having a spiral groove and / or a cross groove formed on the inner surface of the tube, the sinusoidal periodic unevenness formed on the outer surface of the tube is measured over 5 mm in the tube axial direction. The average pitch is 0.8 mm or more, and the height difference between the top of the highest convex portion and the bottom of the lowest concave portion is 5 μm.
A heat transfer tube with an internal groove, characterized in that: 2. The average surface roughness Ra of the outer surface of the pipe measured in the pipe axial direction is 0.4 μm or less, and the maximum surface roughness Rmax is 4 μm.
The heat transfer tube with an inner groove according to claim 1, wherein the heat transfer tube has an inner diameter of m or less. 3. A diameter-reducing die for reducing the diameter of the raw pipe, and at least a downstream side of the diameter-reducing die in the flow direction of the raw pipe, the rotation axis of which is perpendicular to the pipe axis of the raw pipe. A pair of drum-shaped rolls, a floating plug that is stopped by being stopped by the diameter-reducing die inside the element tube at a position matching the arrangement position of the diameter-reducing die, and connected to the floating plug through a plug shaft. And a grooved plug disposed inside the element tube at a position aligned with the arrangement position of the hourglass-shaped roll, wherein the element tube is pressed by the hourglass-shaped roller toward the grooved plug, and a spiral groove and / Or in the manufacturing apparatus of the heat transfer tube with the inner groove for transferring the cross groove to the inner surface of the raw tube, the surface roughness Ra of the roll in the circumferential direction and the roll axial direction of the drum-shaped roll is 0.2 μm or less, and Rmax is 1.5
An apparatus for manufacturing a heat transfer tube with an inner groove, characterized in that the diameter is not more than μm.