JPH0718458A - Al or al alloy fin material subjected to hydrophilic surface treatment and excellent in water dropping ability, its production and core of heat exchanger - Google Patents

Abstract

PURPOSE:To produce an Al fin material subjected to hydrophilic surface treatment and excellent in water dropping ability by forming a hydrophilic coating film having striped waviness on the surface of an Al substrate and regulating the pitch and height of the waviness CONSTITUTION:A hydrophilic coating film 2 having about 2.5mum thickness is formed on the surface of an Al or Al alloy substrate 1 to produce an Al or Al alloy fin material subjected to hydrophilic surface treatment. At this time, striped waviness is formed on the surface of the hydrophilic coating film 2 and the pitch (p) and height (h) of the waviness are regulated to 1-8mm and 0.1-3mu, respectively. The objective Al or Al alloy fin material maintaining satisfactory water dropping ability over a long period of time and having improved durability is obtd.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a surface of a substrate made of Al or an Al alloy (hereinafter, also simply referred to as Al),
The present invention relates to a hydrophilic surface-treated aluminum fin material having a film excellent in hydrophilicity, a method for producing the fin material, and a core of a heat exchanger to which the fin material is applied. A fin material made of hydrophilic surface-treated Al that maintains good hydrophilicity and exhibits excellent water drop properties even when deteriorated, a method for producing such fin material, and characteristics of the fin material The present invention relates to a core of a heat exchanger that effectively uses

[0002]

2. Description of the Related Art Various heat exchangers are equipped with fin materials in order to increase a heat dissipation area and improve heat exchange characteristics. Further, as a base material for fin materials, workability, economy and heat conduction are provided. Al plate (or Al alloy plate)
Is commonly used. By the way, when the heat exchanger is an evaporator of an air conditioner, etc., the surface temperature of the fin material is lower than the dew point of the atmosphere, so that moisture in the air is condensed on the surface of the fin material to cause water droplets. Becomes attached. Then, when this water drop grows and grows larger, water finally stays between the fins, increasing the passage resistance of the air passing through for heat exchange, and reducing the heat exchange efficiency. Happens. Such an inconvenience is particularly remarkable when the fin pitch is narrowed in order to improve the performance of the heat exchanger and reduce the size thereof.

Therefore, in order to keep the heat exchange efficiency in the heat exchanger high for a long period of time, it is necessary to promote the falling property of water and prevent the water from staying on the fin surface. Generally, as a means of promoting the fall of water,
(A) Water-repellent treatment to prevent water from adhering to the fin surface, and (B) Improve the fin surface wettability (hydrophilicity), that is, the water contact angle (angle formed by the fin material surface and the water drop surface). 2) is made smaller to prevent water from flowing down and to form a wide range of paths, and the latter is the most widely used method.

[0004]

[Problems to be Solved by the Invention] The hydrophilic surface treatment is
Generally, a hydrophilic film is formed on the surface of the fin material made of l. The physical properties of such a hydrophilic surface-treated fin material made of Al are defined by the water contact angle, and the water contact angle is 1
Those of 0 degrees or less are generally used. However, the hydrophilicity of the hydrophilic surface-treated Al fin material is
There is a problem in terms of durability because the water contact angle gradually deteriorates over time, and the water contact angle gradually increases to 30 to 60 degrees or more. When the hydrophilicity of the fin material deteriorates as described above, the condensed water tends to repel the fin material surface,
The condensed water becomes hard to drop and aggregates into individual large water droplets. Then, water spreads between the fins,
The air for heat exchange cannot pass through, and the performance as a heat exchanger is deteriorated.

The present invention has been made to solve the above problems, and its purpose is to show a tendency that the hydrophilicity of the hydrophilic film is deteriorated and the water contact angle is increased. However, a fin material made of Al (or Al alloy) having improved durability by maintaining good water drop property for a long time, a method for producing such fin material, and application of the fin material To provide the core of the heat exchanger.

[0006]

Means for Solving the Problems According to the present invention which achieves the above object, at least the surface of the hydrophilic film is formed with a striped undulation, and the undulation has a pitch of 1 to 8
mm, height: 0.1 to 3 μm, which is a fin material made of hydrophilic surface-treated Al or Al alloy. As a method for producing the fin material as described above, hydrophilic surface-treated Al or Al alloy fin material is press-molded to form the above-mentioned waviness on both the hydrophilic film surface and the substrate. The method of doing is proposed. Furthermore, the hydrophilic surface-treated Al or Al alloy fin material as described above is arranged and assembled so that the lengthwise direction of the striped pattern is the vertical direction, so that the heat exchanger excellent in water drop property. The core of is obtained.

[0007]

The present inventors paid attention to the state of water drop and examined from various angles means for exhibiting a good water drop property even when the water contact angle was increased. Then, first, if the water contact angle in the falling direction is made smaller, it acts in a direction to accelerate the falling property of water. Therefore, in order to realize this situation, attention was paid to the following phenomenon. That is, regarding the water contact angle, the larger the amount of dew condensation water, the larger the self-weight of water due to gravity and the smaller the water contact angle. After further study to apply this phenomenon, at least on the surface of the hydrophilic film, the specified requirements (pitch and height described later)
By forming a striped undulation satisfying the above condition, it was found that dew condensation water droplets can be aggregated, thereby making it possible to reduce the water contact angle and maintain good water dropability, and completed the present invention. In order to achieve the object of the present invention, it is sufficient that at least the above-mentioned undulations are formed on the hydrophilic film. Therefore, (1) the undulations are formed only on the hydrophilic film and the fin made of Al is used. The material does not have swell, and (2) not only hydrophilic film but also Al
Although the waviness is already formed on the fin material, it is meant to include both.

In the present invention, the height of the waviness formed on the hydrophilic film needs to be 0.1 to 3 μm, for the following reason. First, the thickness of the hydrophilic film normally formed is about 0.1 to 3 μm, and the thickness is 0.1 μm.
In the following, the original effect (that is, the effect of imparting hydrophilicity) due to the formation of the hydrophilic film is not exhibited, and if it exceeds 3 μm, the heat transfer resistance due to the film increases and the heat exchange efficiency decreases. The preferable film thickness of the hydrophilic film is about 2.5 μm. For a hydrophilic film having the above-mentioned thickness, a swell height of 0.1 μm is the minimum required to form a swell that allows the accumulation of condensed water, and the upper limit is the ventilation resistance. It is necessary to suppress the thickness to 3 μm or less so as not to affect the above.

On the other hand, as for the pitch of the swell, it is preferable that the pitch of the swell is as small as possible because condensed water begins to form from several μm and collects. However, the lower limit is set to 1 mm in consideration of the production limit. . In addition, in the case of a film with excellent hydrophilicity, the water spread of dew condensation water is about 8 mm, and if it is more than this, it means that the hydrophilicity of the film is sufficiently good, and it does not make sense to form undulations. The upper limit of the pitch was 8 mm.

The material of the hydrophilic film in the present invention may be any one commonly used, for example, sodium silicate-based water glass-polyacrylic acid-based water-soluble organic resin as shown in Examples below, and water glass. If it is a system, it may be a lithium system or a potassium system. Other water-soluble organic resins include polyvinyl alcohol, polyacrylamide,
Polymaleic acid, polyurethane type, urea resin type, cellulose type, polyepoxy type, etc. can be used. These hydrophilic films themselves have a water contact angle of 10 degrees or less at the initial stage of film formation, and thereafter, the numerical value thereof gradually increases with time and becomes 30 to 60 degrees or more. Even at this time in fin materials, by forming the above-mentioned striped undulations on the hydrophilic film, dew condensation water tends to collect and the amount of water apparently increases. Shows a tendency to decrease, and good water drop property can be maintained for a long period of time.

The hydrophilic surface-treated Al (or Al of the present invention
(Alloy) fin material has (1) waviness formed only on the hydrophilic film and no waviness on the Al fin material, and (2) not only on the hydrophilic film but also on the Al fin material. It is as described above that any of those having waviness already formed is included, and a method of forming waviness in the surface-treated Al fin material of each of these forms will be described.

First, as the method of forming the undulation of the above-mentioned form (1), the following methods (a) to (d) can be mentioned. According to these methods, an Al fin material having a form as shown in FIG. 1 (cross-sectional view) can be obtained (in the figure, 1 is an Al fin material, 2 is a hydrophilic film, p is a pitch, and h is a pitch). Show each height).

(A) First, as a first method, a method of reversely utilizing the liquid deviation phenomenon, which has been a problem at the time of conventional coating, and the coating liquid aggregates into a striped pattern after coating, is used. However, this method is a simple method, but it is a method that can be adopted when it is difficult to secure the height of swell and the hydrophilicity of the film is basically excellent. (B) As the next method, the above-mentioned liquid leaning is also used,
A method of increasing the viscosity of the coating liquid and transferring the striped adhesive release of a roll such as a roll coater can be mentioned. According to this method, a higher striped pattern / waviness can be formed as compared with the method (a).

(C) When the hydrophilic film is formed by the dipping treatment, the coating liquid causes dripping when pulled up in the plate direction, but such dripping can form a waviness. (D) The methods (a) to (c) have a drawback that the pitch control of the swell is random. Considering these points, the following method is available as a method for positively controlling the waviness shape. That is, a hydrophilic film is once formed on the entire surface of the material, and this is used as a base layer and then partially coated by a printing roll, a gravure roll, or the like so as to form a striped pattern,
This is a method of forming a portion corresponding to the undulation.

The above method is basically based on the assumption that the undulations are formed in the plate-shaped material, but the undulations may be formed either at the stage of the plate-shaped material or after the core is assembled. good. That is, regardless of whether or not the fin material is surface-treated, after assembling the core of the heat exchanger with the fin material, the fin material is immersed in a hydrophilic surface treatment agent, and then immersed in the fin plate direction. It is also possible to form a striped pattern / waviness due to dripping during pulling up.

Next, as a method of forming the undulation of the form (2), the following method may be mentioned. That is, a predetermined waviness shape is provided in a press die, and when a predetermined shape is imparted to the hydrophilic surface-treated Al fin material during fin press molding with this press die, the hydrophilic film surface (and the base material) It is a method of forming undulations. This method has the advantages that it is simple, the pitch can be easily controlled, and the undulation of a desired shape can be formed. A cross-sectional view of an Al fin material obtained by this method is shown in FIG. 2 (note that reference numerals 1, 2, p and h in FIG.
Has the same meaning as).

In the fin material made of the hydrophilic surface-treated Al or Al alloy of the present invention, the waviness as described above is formed at least on the surface of the hydrophilic film, so that the water falling property of the fin material can be favorably maintained for a long period of time. However, in order to achieve a better water drop property, when the Al fin material is assembled to the core of the heat exchanger, the stripe pattern is oriented vertically. It is preferable to arrange them as follows. The core of the heat exchanger assembled in this manner causes the condensed dew condensation water to drop promptly along the ridge groove.

The present invention will be described in more detail with reference to the following examples, but the following examples are not intended to limit the present invention, and any modification of the present invention can be made without departing from the spirit of the preceding and following paragraphs. It is included in the technical scope.

[0019]

【Example】

Example 1 No. 3 sodium silicate-based water glass 3 as a hydrophilic surface treatment agent
% -Polyacrylic acid-based water-soluble organic resin 1% was used, and the aqueous solution was applied to the surface of the fin material made of Al by a roll coater and then baked to form a hydrophilic film. At this time, the above-mentioned aqueous solution tends to lean,
The thicker the film, the greater the phenomenon of liquid leaning, and the larger the swell. Then, the coating thickness is 0.1 μm, 0.
5μm, 1.0μm, 1.5μm, 2.0μm, 2.5
Various undulations were formed as shown in Table 1 below to obtain a surface-treated Al fin material as shown in FIG.

With respect to each of the hydrophilic surface-treated Al fin materials obtained, the hydrophilic characteristics after the initial test and after the durability test were examined by the water contact angle, and the ventilation resistance at each time was also examined. The durability test conditions at this time were as follows: (Left in running water for 8 hours
→ 20 cycles of drying at 80 ° C and leaving for 16 hours)
Cycle (480 hours), and the ventilation resistance ratio was measured by making a heat exchanger and measuring the pressure loss generated by the wind tunnel measuring device based on JIS B 8330 (pressure loss during cooling).
/ (Pressure loss during blast drying), and the durability was evaluated after repeating cooling operation for 8 hours and heating operation for 16 hours for 3 months (2160 hours). The results are shown in Table 1.
Also described in.

[0021]

[Table 1]

From Table 1, the following can be considered. First, for those that do not have undulations (No. 1), the ventilation resistance ratio tends to increase as the hydrophilicity of the hydrophilic film itself decreases, but by forming undulations (No. 2).
7) The water contact angle in the direction in which the condensed water falls can be kept low, and the increase in the ventilation resistance ratio can be kept within the allowable range. It can also be seen that the ventilation resistance ratio rises even if the swell becomes too large (No. 8). It is considered that this is because the heat transfer resistance increases due to the film thickness becoming too thick, and the space between the fins narrows, so that the heat exchange efficiency rather decreases and the ventilation resistance ratio tends to increase.

Example 2 Using the same hydrophilic surface treating agent as used in Example 1, the treating agent was applied on the surface of the fin material made of Al by a roll coater and then baked to form a hydrophilic film. did.
At this time, the thickness of the film was 0.5 μm. When the Al fin material having the hydrophilic film formed thereon is press-formed into a fin shape, various undulations are formed as shown in Table 2 below to obtain the surface-treated Al fin material as shown in FIG. It was The same investigation as in Example 1 was conducted for each of the obtained hydrophilic surface-treated Al fin materials. The results are shown in Table 2.
Also described in.

[0024]

[Table 2]

As is apparent from Table 2, it is understood that forming waviness having a predetermined shape is effective for maintaining good water drop properties, as in Example 1.

[0026]

The present invention is constituted as described above, and even if the hydrophilicity of the hydrophilic coating itself is deteriorated by forming a waviness satisfying predetermined requirements on the surface of the hydrophilic coating. Thus, a fin material made of hydrophilic surface-treated Al or Al alloy, which maintains good water dropability and does not invite an increase in ventilation resistance ratio, was realized.

[Brief description of drawings]

FIG. 1 is a sectional explanatory view showing an embodiment of the present invention.

FIG. 2 is a cross sectional view showing another embodiment of the present invention.

[Explanation of symbols]

 1 Al fin material 2 Hydrophilic coating p Pitch h Height

Claims (4)

[Claims] 1. A hydrophilic surface-treated Al or Al alloy fin material having a hydrophilic coating formed on the surface of an Al or Al alloy base material, wherein at least the hydrophilic coating surface has a striped undulation. In addition, the undulation has a pitch of 1 to 8 mm and a height of 0.1 to 3 μm, which is a fin material made of hydrophilic surface-treated Al or Al alloy excellent in water drop property. 2. The hydrophilic surface-treated Al or Al alloy fin material according to claim 1, wherein the base material has a waviness with a pitch of 1 to 8 mm and a height of 0.1 to 3 μm. 3. The hydrophilic surface-treated Al or Al alloy fin material according to claim 2 is manufactured by press-molding the hydrophilic surface-treated Al or Al alloy fin material, which is excellent in water drop property. A method for manufacturing a fin material made of hydrophilic surface-treated Al or Al alloy. 4. The hydrophilic surface-treated Al or Al alloy fin material according to any one of claims 1 to 3 is arranged and assembled such that the lengthwise direction of the striped pattern is the vertical direction. The core of the heat exchanger characterized by that.