JPH09303985A - Copper tube for heat exchanger excellent in tube expansion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an avec phenomenon from being generated on aluminium fins upon tube expansion in a mandrel by determining the average surface roughness of the surface of a copper tube in the axial direction as a specific value. SOLUTION: The average surface roughness in the axial direction of a copper tube 1 used for a heat exchanger is expressed by Ra=0.05 to 0.5μm. Further, the surface roughness Ra in the axial direction of the copper tube 1 for the heat exchanger is 0.1 to 0.35μm. Then, the copper tube 1 is a copper tube whose inner surface is provided with grooves. The heat exchanger is manufactured by inserting the copper tube 1 into the holes of the aluminium fins 2, expanding the copper tube 1 by the mandrel and forming the copper tube 1 integrally with the aluminium fins 2. Thus, an avec phenomenon that many aluminium fins provided at regular intervals before the expansion of the tube are deforemd during the tube expansion and the aluminium fins come into contact together can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper pipe for a heat exchanger, and more particularly to a copper pipe having excellent pipe expandability when manufacturing a heat exchanger.

[0002]

2. Description of the Related Art As is well known, heat exchangers such as room air conditioners, package air conditioners, etc., in which a large number of corrugated aluminum fins are provided in a hairpin-processed copper tube are used. Usually, this type of heat exchanger is manufactured by inserting a copper tube into a hole of an aluminum fin, and then expanding the copper tube with a mandrel to integrate the copper tube and the aluminum fin. This expansion is a mechanical method, that is, a burette with an outer diameter larger than the inner diameter of the copper tube is usually attached to the tip of the mandrel, and this mandrel is press-fit into the copper tube to expand the copper tube. Stick it to the fin. In this case, the expanded copper tube and the aluminum fin do not adhere to each other, in other words, when the copper tube and the aluminum fin do not adhere to each other, the corresponding amount causes
The heat efficiency of the heat exchanger deteriorates.

[0003]

However, when the pipe is expanded, a deformation defect of the aluminum fin, which is a so-called Abeck phenomenon, is likely to occur. This Abeck phenomenon is shown in Fig. 1.
With respect to the heat exchanger in the normal state of (a), as shown in FIG. 1 (b), a large number of aluminum fins 2 arranged at regular intervals before pipe expansion are deformed when the copper pipe 1 is expanded, It means that aluminum fins are in contact with each other. When this abec phenomenon occurs, not only is it unfavorable in appearance,
There is a problem that the ventilation resistance of the aluminum fins increases and the thermal efficiency deteriorates. The present invention has been made by elucidating the mechanism of this Abeck phenomenon, and is intended to provide a copper tube in which the Abeck phenomenon does not occur in an aluminum fin during tube expansion.

[0004]

To this end, the means of the present invention has a mean surface roughness Ra of the copper tube surface in the tube axis direction of 0.0.
It is to be 5 to 0.5 μm. The present inventors, as a result of elucidating the mechanism of the Abeck phenomenon, since the expansion of the copper pipe is performed by press-fitting the mandrel, the laminated aluminum fins are sequentially pushed in the expanding direction instead of all at the same time, on the contrary. We have found that the copper tube itself shrinks in the direction of expansion and the color height of the aluminum fin increases. When the color height of the aluminum fin is increased, friction between the copper tube and the aluminum fin is increased during the tube expansion, the deformation of the aluminum fin becomes uneven, and the Abeck phenomenon easily occurs. Further, this Abeck phenomenon is more likely to occur in the aluminum fins nearer the end of pipe expansion. Therefore, from this mechanism, if the friction between the copper tube and the aluminum fin is reduced, the abec phenomenon of the aluminum fin can be prevented.

In order to reduce the friction between the copper tube and the aluminum fin, first, a method of applying a surface treatment to the aluminum fin or the copper tube to reduce the friction can be considered. Even today, pre-coated fins that have undergone a surface treatment such as silica-based or resin-based film are often used for the purpose of imparting corrosion resistance and lubricity to aluminum fins, and a material that reduces friction is used as this surface treatment agent.
It is considered that the Abeck phenomenon can be prevented by improving the slipperiness of the aluminum fin. However, in the case of pre-coated fins, for example, even if the pre-coated fins have a high slipperiness (the surface of which is treated with a silica-based lubricant), there is a limit to reducing the friction to prevent the Abeck phenomenon, and the aluminum fins are also limited. On the other hand, the surface treatment of the copper tube and the copper tube to reduce friction results in impairing the heat conductivity of the aluminum fin and the copper tube itself. According to the studies made by the present inventors, there is no surface treatment agent capable of reducing friction to the extent that the Abeck phenomenon can be prevented without impairing the heat transfer properties of aluminum fins and copper pipes. Therefore, the use of surface-treated aluminum pre-coated fins is useful for other purposes such as imparting corrosion resistance, but is not practical for preventing the Abeck phenomenon.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, it is essential to reduce friction on aluminum fins and copper pipes without impairing the heat transfer properties of the heat exchanger. The average surface roughness Ra of is set to 0.05 to 0.5 μm. If the average surface roughness Ra in the tube axis direction exceeds 0.5 μm, the combination of the copper tube and the aluminum fins (including the pre-coated fins) cannot prevent the abeck phenomenon of the aluminum fins. Further, from the viewpoint of preventing the Abeck phenomenon, as described above, it is better that the average surface roughness in the tube axis direction is smaller, but if it is too small, a problem occurs in copper pipe production. That is, the average surface roughness Ra in the tube axis direction is 0.05 μm.
If it is less than 1, the rolling speed in the inner grooving step becomes small, particularly when the inner grooved copper tube is manufactured, and the productivity of the copper tube is significantly impaired. Therefore, the average surface roughness Ra in the tube axis direction is
Is required to be 0.05 to 0.5 μm. In addition, from the perspective of further preventing the Abeck phenomenon and improving productivity,
A more preferable range of the average surface roughness Ra in the tube axis direction is 0.
It is 1 to 0.35 μm.

In the present invention, the adjustment of the average surface roughness in the tube axis direction does not require a special step or means, and can be performed by means such as brushing in the adjusting step in the usual copper tube production. . The average surface roughness in the pipe circumferential direction has the same effect as the average surface roughness in the pipe axis direction on the abec phenomenon of the aluminum fins, but the average surface roughness in the pipe axis direction can be increased by means such as brushing. If the thickness is adjusted, the average surface roughness inevitably becomes the same as the average surface roughness in the pipe axis direction, and it is difficult to measure the average surface roughness in the pipe circumferential direction based on the JIS standard. not regulated.

The copper pipe used in the present invention may be a phosphoric acid deoxidized copper that is generally used, and the groove shape of the inner surface may be the groove shape that is commonly used. Further, as the aluminum fin, a generally used pure aluminum type aluminum alloy such as JIS A1100 or A1200 can be used, and the fin shape is appropriately selected from commonly used shapes such as corrugated. Further, as the surface treatment agent for the precoat fin, a commonly used silica type or resin type surface treatment agent is applied.

[0009]

EXAMPLE A copper tube has a phosphorus-deoxidized copper-soft material outer diameter of 9.52.
For a copper tube with an internal groove of mmφ and an average wall thickness of 0.35 mm, the average surface roughness Ra in the tube axis direction is variously changed by brushing in the adjusting step during copper tube production. I was there. Aluminum fin is JIS A110
0-H26, 0.110 mm thick aluminum plate, using ordinary pre-coated fins (silica surface treatment) and highly slippery pre-coated fins (silica surface treatment with lubricant), corrugated fin shape, by drawless molding , 1 row, 10 steps, color height 1.20 mm. The hole diameter of the collar was set to 9.80 mmφ. This aluminum fin 4
00 sheets were piled up, the above-mentioned hairpin-treated copper tube was inserted, and the tube was expanded by a tube expander. Pipe expansion conditions are pipe expansion speed 10m / min,
The pipe expansion ratio was 1.40% based on the fin holes. After the tube was expanded, the occurrence of the Aveck phenomenon was visually evaluated. In addition, the copper tube of each surface roughness was tested three times under the same conditions. Table 1 shows the average surface roughness Ra in the tube axis direction and the evaluation result of the Abeck phenomenon. From Table 1, No1.2 within the scope of the present invention
1 shows both the normal pre-coated fins and the highly slippery pre-coated fins, and no Abeck phenomenon occurred.
A normal heat exchanger as shown in (a) was obtained. On the other hand, in No. 3.4, which is out of the range of the present invention, the abec phenomenon as shown in FIG. 1B occurred not only in the normal pre-coated fins but also in the high-slip pre-coated fins.

[0010]

[Table 1]

[0011]

As described above, according to the present invention, the aluminum fin abeck phenomenon can be prevented from occurring by adjusting the average surface roughness Ra of the copper tube in the tube axis direction. This is a solution to a long-standing problem especially for copper tube expanding process such as copper tube with inner surface groove by simple means.The present invention enables heat exchange of room air conditioners and packaged air conditioners that are clean and have excellent thermal efficiency. It is of great industrial significance in that it makes it possible to manufacture vessels.

[Brief description of drawings]

FIG. 1 is an explanatory view of a usage state of a copper tube for a heat exchanger according to the present invention, in which a is a normal case and b is an abec phenomenon.

[Explanation of symbols]

 1: Copper tube 2: Aluminum fin

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kenji Noda 15 Kinugaoka, Moka City, Tochigi Prefecture Kamido Steel Works Moka Plant

Claims (3)

[Claims] 1. The average surface roughness of the copper pipe surface in the pipe axis direction is R
a = 0.05 to 0.5 μm, a copper tube for a heat exchanger, which is excellent in tube expandability. 2. The copper tube for a heat exchanger according to claim 1, wherein the Ra is 0.1 to 0.35 μm. 3. The copper tube is a copper tube having an inner groove,
A copper tube for a heat exchanger, which is excellent in tube expandability according to 2.