JPH07198290A - Aluminum fin material for heat exchanger with excellent hydrophilic property and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide an aluminum fin material for a heat exchanger having excellent hydrophilic property as compared with conventional surface treating material and a method for manufacturing the same. CONSTITUTION:An aluminum fin material for a heat exchanger having excellent hydrophilic property comprises a finely uneven surface formed by chemically dissolving reaction or electrolytic dissolving using electricity on a surface in such a manner that a surface area due to the uneven surface is set to 20cm<2> or more per a square of 1cm<2> of the material. This surface area is obtained by controlling the chemical etching, electrolytic etching conditions. The hydrophilic property having a water contact angle of 10 deg. or less is obtained even at an initial or after the material is repeatedly dried and humidified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum fin material used in a heat exchanger such as a room air conditioner.

[0002]

2. Description of the Related Art Conventionally, aluminum has been used as a fin material for a heat exchanger because of its excellent thermal conductivity and moldability. And this aluminum fin material has excellent anti-corrosion treatment for the purpose of preventing the occurrence of corrosion, and further has excellent water wettability for the purpose of improving drainage so that condensed water during cooling operation does not accumulate between the fins. A hydrophilic surface treatment is carried out.

Japanese Patent Publication No. 3-77
The treatment using silicate as shown in No. 440 and the one coated with hydrophilic resin have been put to practical use, and reduction of ventilation resistance at the time of ventilation, and eventually improvement of heat exchange efficiency, etc. It contributes to the performance improvement of the heat exchanger.

However, in recent heat exchangers, miniaturization and higher performance have been achieved, and the fin spacing is
In the indoor unit, the conventional size was 1.5 to 2.0 mm, but it has been narrowed to 1.2 to 1.4 mm, and the fin shape is cut and raised, and many slits are formed to improve thermal efficiency. Is being improved.

In the case of such a fin shape, water droplets or a water film are formed in the collar portion or the slit portion during the cooling operation, the resistance during ventilation (ventilation resistance) increases, and the effect of improving the heat efficiency by the fin shape is offset. And the heat exchange capacity decreases,
There is a demand for fin materials that have better drainage properties and excellent hydrophilicity than ever before.

In order to meet such demands, it is an object of the present invention to provide an aluminum fin material for a heat exchanger, which has hydrophilicity superior to that of a conventional surface-treated material, and a manufacturing method thereof.

[0007]

Means for Solving the Problems As a result of earnest research for solving the above problems, the present inventor has responded to the above-mentioned miniaturization and high performance of the heat exchanger, and the dew condensation water spreads completely, that is, The aluminum fin material that makes the contact angle as close as possible to 0 °, reduces the formation of water drops on the fins as much as possible, and also reduces the water film thickness, and maximizes the effect of improving the heat exchange efficiency by the fin shape. It was developed.

That is, the present invention has fine irregularities formed on the surface of an aluminum plate material by a chemical dissolution reaction or electrolytic dissolution utilizing electricity, and the surface area due to the fine irregularities is 1 cm ² square per material. The gist is an aluminum fin material for a heat exchanger having excellent hydrophilicity, which is characterized by having a size of 20 cm ² or more.

Further, the manufacturing method is such that the surface of the aluminum plate is melted by a chemical dissolution reaction or by electrolytic dissolution using electricity, and the surface area is ² per 1 cm ² square of the material.
The feature is that fine irregularities of 0 cm ² or more are formed.

[0010]

The present invention will be described in more detail below.

In short, the present invention is characterized in that the surface of an aluminum plate is eroded by electrolytic etching or chemical etching so that the microscopic surface area obtained by the BET method is 20 cm ² or more per 1 cm ² square of the material. .

Here, the surface area is a value obtained by the BET method. The BET method is known as a method in which nitrogen atoms are used as an adsorbed gas and the surface area is obtained from the adsorbed amount of the adsorbed gas. Since a measuring device is commercially available, it can be easily analyzed. Further, in the present invention, etching means dissolution from the surface of the material to the inside.

As the aluminum fin material used in the present invention, any aluminum material such as pure aluminum which is generally used for this type of application can be applied. Since the plate thickness is reduced by etching the surface, it is preferable to use a plate having a plate thickness including an etching allowance in advance so that sufficient strength can be obtained even after the etching.

In the present invention, the surface of the aluminum material is etched to form a large number of fine depressions. As such an etching method, electrolytic etching using an electrolytic current or chemical etching utilizing a chemical reaction is most suitable. There is. This is because electrolytic etching or chemical etching utilizing a chemical reaction produces a large number of uniform and fine depressions, a large material surface area is obtained, and the contact angle is greatly reduced.

However, although it is possible to roughen the surface by mechanical polishing such as ordinary sandpaper polishing or imparting irregularities with a rolling roll, the intervals between the irregularities are too large or non-uniform, and therefore large. The material surface area cannot be obtained and the contact angle cannot be sufficiently reduced.

Further, in the case of the surface-treated material of the prior art, in the case of the hydrophilic resin coating material and the silicate-treated material, the surface is not roughened and the surface is smooth, and the surface treatment material is roughened by the treatment by mixing the resin and the silicate. Even if surfaced, there is a limit to roughening, and a large surface area cannot be obtained.

In the present invention, the surface obtained by etching has a microscopic surface area (geometrical surface area) as material 1.
It is necessary to carry out etching so as to be 20 cm ² or more per cm ² square. As a result, an initial contact angle of 10 ° or less and a contact angle of 10 ° or less after aging (after a dry-wet cycle) can be obtained. When the initial contact angle is 10 ° or less, the water droplet spreads instantly after the water droplet adheres, and the water film thickness becomes very thin. The contact angle after aging is a necessary index of hydrophilicity because condensation of moisture in the atmosphere and drying by blowing are repeated in an actual heat exchanger, and the contact angle after aging is 10 ° or less, which is sufficient even after aging. Excellent water spreadability is obtained. However, it is less than 1 cm ² per 20 cm ² surface area of the material, the initial contact angle 1
Even if 0 ° or less is not obtained, and even if the initial contact angle is 10 ° or less, the contact angle after aging exceeds 10 ° and the spreadability in water is insufficient.

The surface area of such a material can be easily obtained by controlling conditions such as electrolytic etching or chemical etching processing solution or processing time.

The aluminum fin material for a heat exchanger obtained according to the present invention is mainly effective in improving drainage (spreading of water), but after the main treatment, it is immersed in hot water to roughen the surface. Further, it is possible to form a hydrated oxide film (boehmite film) or perform chromate treatment to impart corrosion resistance.

It is also possible to carry out the etching process by a dipping process after assembling the heat exchanger.

Next, examples of the present invention will be described.

[0022]

[Example] Aluminum plate material (JIS 1100H, 10
(cm × 20 cm, plate thickness 0.12 mm) was etched under the conditions shown in Table 1, and then hydrophilic (initial hydrophilicity, hydrophilicity after aging).
investigated. The results are shown in Table 1.

The hydrophilicity was evaluated by measuring the contact angle and the water spread. The contact angle is an angle θ formed by the tangent line of the water droplet in FIG.
The amount of 5 g was investigated within 20 seconds after the dropping. The water spread is a value obtained by (a + b) / 2 from the spreads a and b in the two vertical and horizontal directions in FIG. 1, and the amount of water when measuring the water spread is 0.01
The test was conducted within 10 seconds after the dropping.

Also, since the condensation of moisture in the atmosphere and the drying by blowing air are repeated in the actual machine, after the cycle of running water → drying (7 cycles of running tap water for 7 hours → 80 ° drying for 17 hours, one cycle is carried out) Hydrophilicity (hydrophilicity over time)
Was similarly investigated.

If the hydrophilicity of the surface is poor, the contact angle becomes high,
In the actual heat exchanger, water droplets are attached and a thick water film is formed, which increases ventilation resistance and significantly reduces the heat exchange capacity. In Table 1, the invention example No. 1
It can be seen that in all of Nos. 4 to 4, contact angles of 10 ° or less were obtained both in the initial stage and after the dry and wet conditions, and the water spread was superior to the case where the conventional silicate-based treatment was carried out (No. 1).

Nos. 5 and 6 are treatment materials that are currently put into practical use as surface-treated fin materials for heat exchangers. No. 5 is a silicate-based treatment, and No. 6 is an acrylic hydrophilic hydrophilic material. It is coated with resin. No. 5 has a contact angle of 10 ° or less at the initial stage, but exceeds 20 ° after dry and wet and the hydrophilicity is lowered, and there is a problem in maintaining a low contact angle. No. 6, which is a resin-based hydrophilic treatment material, had a high contact angle of more than 10 ° from the initial stage, and a contact angle of about 50 ° after dry and wet, indicating poor hydrophilicity.

Nos. 7 and 8 are cases where the surface area is less than 20 cm ² , and in both cases, the contact angle is high and the water spreading property is insufficient as compared with the examples of the present invention.

No. 9 is a case where the surface is roughened by rolling a pre-roughened roll, and Nos. 10 and 11 are a case where the surface is roughened by paper polishing, both of which have a small surface area and are hydrophilic. It has a high angle and is at the same level as or lower than that of the conventional water glass type hydrophilic treatment material.

[0029]

[Table 1]

[0030]

EFFECTS OF THE INVENTION Conventional fins that have been subjected to hydrophilic treatment such as silicate coating or hydrophilic resin coating have problems in that the contact angle is high or the contact angle is low, and the size of the heat exchanger is reduced. While there was a limit in high performance, according to the present invention, since it is possible to suppress an increase in ventilation resistance due to retention of condensed water because of excellent hydrophilicity at the initial stage and after aging,
Further miniaturization and higher performance of the heat exchanger can be achieved.

[Brief description of drawings]

FIG. 1A is a diagram for explaining a contact angle, and FIG. 1B is a diagram for explaining spreading of water.

Claims (2)

[Claims] 1. The aluminum plate material has fine irregularities formed by a chemical dissolution reaction or electrolytic dissolution utilizing electricity, and the surface area of the fine irregularities is 20 cm ² or more per 1 cm ² square of the material. An aluminum fin material for a heat exchanger which is excellent in hydrophilicity. 2. Hydrophilicity characterized in that the surface of an aluminum plate is dissolved by a chemical dissolution reaction or by electrolytic dissolution utilizing electricity to form fine irregularities having a surface area of 20 cm ² or more per 1 cm ² square of the material. A method for producing an aluminum fin material for a heat exchanger, which has excellent properties.