JPH11294993A - Heat exchanger fin and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide hydrophilic performance and deodorizing performance and to prolong the effective period thereof by coating a fin substrate with a film containing a photocatalyst. SOLUTION: The heat exchanger fin 1 is a metal plate having one end fixed to a heating tube 3 coupled with a heat exchanger body 2. Aluminum or aluminum alloy is generally employed and coated with a film of crystalline titania. The film on the aluminum plate is or radiated with UV-rays for 1 min at an intensity about ten times as high as that of solar beam using an UV-lamp to produce a plate excellent in pencil hardness, adhesion, water contact angle, anti-fog property and organic matter decomposition property. Consequently, a heat exchanger fin coated with a photocatalyst, i.e., a titania film, can be obtained. A photocatalyst film 12 is formed on the surface of a fin substrate 10 through a barrier film 11. The barrier film 11 is not essential and the photocatalyst film 12 may be formed directly on the surface of a fin substrate 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fin of a heat exchanger in an air conditioner or a refrigerator. More specifically, the present invention relates to a fin of a heat exchanger in an air conditioner or a refrigerator formed with a film having excellent hydrophilicity and deodorization.

[0002]

2. Description of the Related Art Conventionally, in air conditioners and refrigerators,
Atmospheric moisture condenses and accumulates as water droplets on the fin surface of the heat exchanger, which forms a so-called water bridge between the fins and, in some cases, freezes, causing the air to flow. Since the passage is narrowed, the flow of air is hindered, and as a result, the heat exchange efficiency and the cooling efficiency are reduced, increasing the power consumption, generating noise, and splashing water droplets. I have. As a solution to the problem of the condensed water droplets, conventionally, it has been proposed that the fin surface of the heat exchanger is subjected to a hydrophilic treatment to prevent water droplets from adhering to the fin surface or forming a bridge due to the water droplets. And
As a method of hydrophilizing the fin surface, for example, a method of coating with a film of a hydrophilic synthetic resin such as a copolymer of a lower ester of methacrylic acid and a cationic monomer, an amide resin, or a method of, for example, a fluorosilicate solution or the like A method of forming a hydrophilic film by treating with an inorganic surface treating agent solution has been proposed.

[0003] In addition to the problem of condensed water droplets, the air conditioner produces an unpleasant odor at the start of use. In particular, when the air conditioner is used again one year later without using it until the summer of the following year, the odor is felt stronger. It is also a problem. The cause of this off-flavor was that when the hydrophilic film provided on the fin surface adsorbed organic substances such as odor substances floating in the atmosphere (air) during the unused period, and when the operation was started at the time of resumption, the adsorbed odor was absorbed. It is considered that organic substances such as odorous substances are desorbed in a short time and released into the atmosphere. As a method for solving the problem of the unpleasant odor, a method has been proposed in which the fin surface of the heat exchanger is coated with a hydrophilic film, such as a synthetic resin film in which silica particles or the like are dispersed, in which organic substances are hardly adsorbed. . However, none of the solutions proposed so far has sufficient hydrophilicity and deodorant performance, and their sustainability is not fully satisfactory.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above circumstances, and has a hydrophilicity and a deodorant performance which are far superior to those of the prior art, and which has excellent durability. It is to provide a deodorant heat exchanger fin.

[0005]

In order to achieve the above object, a heat exchanger fin according to the present invention is characterized in that a fin substrate is coated with a film containing a photocatalyst.
In the heat exchanger fin of the present invention, excellent hydrophilicity is obtained by the action of the photocatalyst, and even when an organic substance such as an odorous substance is attached, it can be removed by the photolytic action. In addition, titania used as a photocatalyst has a higher thermal conductivity than a conventional hydrophilic film mainly composed of a resin, so that even if a thick film is formed, the performance of the heat exchanger is not reduced, Hydrophilicity and deodorization can be maintained for a longer period than before.

The present invention also relates to a method for producing the above heat exchanger fin, in which a sol obtained by reacting a metal alkoxide, alcohol, water and a reaction accelerator is applied to a fin substrate, and the resulting wet gel is obtained. After drying the film, the film is crystallized. In the present invention, by employing a sol-gel method, a film containing a photocatalyst (hereinafter referred to as a “photocatalyst film”) can be formed with high purity while controlling the amount (film thickness) of the film. It can be formed uniformly over the entire surface.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. As schematically shown in FIG. 1 (A), the heat exchanger fin 1 is a metal plate mounted on a heat transfer tube 3 having one end connected to the heat exchanger body 2. As a metal to be used, aluminum or an aluminum alloy is generally used, but it is not necessary to limit to this. In addition, usually, a plurality of heat exchanger fins 1 are attached to the heat transfer tube 3 at predetermined intervals in order to increase the heat exchange efficiency. Further, a plurality of insertion holes 4 may be formed in the heat exchanger fin 1, and the heat transfer tubes 3 are inserted into each of them. The present invention is characterized in that the heat exchanger fins 1 are formed by coating a metal plate (hereinafter, referred to as a "fin substrate") with a photocatalytic film.

The photocatalyst used for the heat exchanger fin of the present invention
TiO_Two, ZnO, SnO _Two, SrTiO_Three,
WO_Three, Bi_TwoO_Three, Fe_TwoO_ThreeMetal oxides such as
Can be Among them, TiO_Two(Titania) is harmless
Most chemically stable and cheap.
Commonly used. As titania, anatase or
Any crystal form of rutile can be used.
Natase type has higher photocatalytic activity and decomposes odorous substances
More preferred in terms of performance.

When the fin substrate is coated with the photocatalyst film, the fin substrate may contain an impurity element which diffuses into the photocatalyst film and lowers the performance of the photocatalyst. In order to prevent intrusion, it is preferable to previously form a barrier film made of silica or the like on the fin substrate.

The method for coating the fin substrate with a photocatalytic film is preferably a so-called sol-gel method. Hereinafter, a method of coating a fin substrate with a photocatalytic film by the sol-gel method will be described, taking the case where the photocatalyst is titania as an example. (A) Preparation of sol: a titanium alkoxide is used as a precursor. Examples thereof include tetraethoxytitanium, tetraisopropoxytitanium, tetra-n-propoxytitanium, tetraisobutoxytitanium, tetra-n-butoxytitanium, tetramethoxytitanium and the like. And
An alcohol is added to these titanium alkoxides to dilute them, water is added thereto, a hydrolysis accelerator is further added thereto, and the mixture is stirred to prepare a mixed solution. At this time, the preparation temperature is generally appropriate from room temperature to 70 ° C.

The alcohol used for preparing the mixed solution is ethanol, methanol, n-propanol,
Isopropanol, n-butanol, isobutanol and the like. The use amount of these alcohols is 10 mol or more, preferably 2 mol, per 1 mol of titanium alkoxide.
0 to 100 mol. If the amount of the alcohol used is less than 10 mol, the stability of the produced sol becomes insufficient. The amount of water is 7 mol or less, preferably 2 to 5 mol, per 1 mol of titanium alkoxide. If more than 7 moles of water are added, the resulting sol may have insufficient stability. Examples of the reaction accelerator include inorganic and organic acids such as hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, acetic acid, and oxalic acid, and inorganic and organic bases such as sodium hydroxide, potassium hydroxide, and alkylamine. The amount of the hydrolysis accelerator used is 0.002 to 2 mol, preferably 0.01 to 0.5 mol, per 1 mol of the titanium alkoxide.
Is a mole. If the amount of the hydrolysis accelerator is less than 0.002 mol, the hydrolysis / polycondensation reaction does not sufficiently occur, the gel is insufficiently formed, and the formation of the photocatalyst film may be insufficient. is there. On the other hand, if the amount of the hydrolysis accelerator exceeds 2 mol, the stability of the produced sol becomes insufficient, and a precipitate may be formed in the sol. That is, in preparing the above-mentioned mixed solution, it is desirable that the ratio of the alcohol is 10 mol or more, the amount of water is 7 mol or less, and the amount of the reaction accelerator is 0.002 to 2 mol with respect to 1 mol of the titanium alkoxide.

(B) Coating and gelling of the sol:
The mixed solution prepared as described above is applied to a fin substrate processed into a predetermined shape. This coating includes dip coating, spin coating, spray coating,
The coating itself such as roll coating can be performed by appropriately selecting a known coating method. Among them, the dip coating method is simple and preferably applied. In the case of the dip coating method, the fin substrate is immersed in the mixed solution for 1 second or more, and then the fin substrate is pulled up at a constant speed, whereby a coating film of the mixed solution is formed on the fin substrate. When a heat exchanger fin is used, the thickness of the coating film is generally 10 angstrom or more and 100 μm.
The following ranges are preferred. If the film thickness is less than 10 angstroms, sufficient hydrophilicity and deodorization effect may not be obtained,
On the other hand, if it exceeds 100 μm, peeling or cracking may occur in the coating film.

In the present invention, the thermal conductivity of the metal oxide as a photocatalyst is about 20 to 50 times higher than the thermal conductivity of a conventional hydrophilic film mainly composed of a resin, and even if the film thickness is increased. A decrease in the heat exchange performance (radiation) of the heat exchanger fins can be suppressed lower than in the past. Therefore, in the above-mentioned film thickness range, the film thickness can be made thicker, and the hydrophilicity and the deodorant property can be maintained for a longer period than before.

Here, it is known that the thickness of the coating film generally conforms to the following formula (I), and the thickness can be controlled based on this. t = K · (ηυ / pg) ^1/2 (I) (where, t is the film thickness, η is the viscosity of the solution, υ is the lifting speed, p is the density of the solution, g is the gravitational acceleration, K Is a constant including the number of capillaries.) If the desired film thickness cannot be obtained by one immersion of the fin substrate, the desired film thickness can be obtained by repeating the immersion of the fin substrate a plurality of times. it can. In this way, a gel coating applied to the fin substrate is formed.

Prior to the application of the mixed solution to the fin substrate, it is preferable that the fin substrate be subjected to a treatment of washing with a surfactant such as an organic alkali or an acid such as hydrofluoric acid and drying in advance. . As described above, it is also preferable to apply a barrier film such as silica in advance. In this case, the silica barrier film can be formed, for example, by mixing silicon alkoxide, water, alcohol, and a reaction accelerator, and by a sol-gel method.

(C) Crystallization: Next, the fin substrate coated with the gel film is fired to crystallize the film. This firing can be performed by any known firing means. In addition, this firing does not require any special control of the atmosphere, but requires oxygen. Heating rate is 100 ° C / min
The following is preferable, and above this, the organic residue in the gel may not be sufficiently removed. Maximum firing temperature is 300 ℃
The above is preferred. By promoting the gel reaction by adjusting the components of the sol or irradiating ultraviolet rays, crystallization can be performed even at a low temperature equal to or lower than the above temperature.

Thus, a heat exchanger fin coated with a titania film as a photocatalyst is obtained. FIG. 1B shows an enlarged cross-sectional view, in which a photocatalytic film 12 is formed on the surface of a fin substrate 10 via a barrier film 11.
The barrier film 11 is not essential, and the fin substrate 10
Of course, it is also possible to form the photocatalytic film 12 directly on the surface.

[0018]

EXAMPLES The present invention will be described in more detail with reference to the following Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Example 1 A mixed solution was prepared by mixing 44.93 mol of ethanol, 2.43 mol of water and 0.21 mol of hydrochloric acid with respect to 1 mol of tetraisopropoxytitanium. did. This mixed solution was previously washed with Semico Clean (manufactured by Furuuchi Chemical Co., Ltd.) and applied to a dried aluminum plate by dip coating at a dip coating speed of 10 cm / min and three times of dips. After drying the quartz substrate coated with the coating film of this mixed solution at 500 ° C. for 8 hours, an aluminum plate coated with a crystalline titania coating was obtained. Then, after irradiating the aluminum plate film with ultraviolet rays of about 10 times the intensity of sunlight for 1 minute using an ultraviolet lamp, the pencil hardness, adhesion, water contact angle, anti-fogging property and organic matter decomposability were evaluated. did. The results are shown in Table 1. For comparison, a film was formed on the same aluminum plate as above using a commercially available polyvinyl acetate-based hydrophilic treatment agent (manufactured by Nippon Light Metal Co., Ltd.), and the same evaluation as above was performed. The results are shown in Table 1.

[0020]

[Table 1]

* 1: Pencil hardness, adhesion = JIS-K54
00 based. * 2: Heat resistance: After raising the temperature to each temperature in the atmosphere, the temperature was returned to room temperature, and the temperature at which the film was not decomposed and hydrophilicity was maintained was measured. * 3: Organic substance decomposability = 1 mg of edible oil per 10 cm ²
While applying, while irradiating ultraviolet rays with the above ultraviolet lamp,
The time required for the oil to decompose was measured.

As shown in Table 1, Example 1 was remarkably superior in both pencil hardness and adhesion to the comparative experiment.
Has heat resistance of 0 ° C or higher. In Example 1, the edible oil was decomposed in 10 hours, and the organic matter decomposability (deodorization properties) was excellent. On the other hand, the polyvinyl acetate-based hydrophilic treatment agent film of the comparative experiment was basically deodorized. No effect was observed.

Further, actual heat exchanger fins were formed at a pitch of 1.5 mm from a 0.1 mm-thick aluminum plate coated with a crystalline titania film in the same manner as in Example 1 at 60 ° C. and 98% humidity. And then returned to normal temperature and normal humidity for 5 minutes,
After irradiation for 1 minute, a test for observing water droplets condensing on the fins was repeated several times. For comparison, a similar test was conducted on an aluminum plate coated with a film of a commercially available polyvinyl acetate-based hydrophilic treatment agent in the same manner as in the above comparative experiment. As a result, in the first test, water spread in both heat exchanger fins in a film form, and formation of water droplets was not recognized. However, in the tenth test, Example 1
In the heat exchanger fin according to the above, water spread in the form of a film, whereas in the heat exchanger fin according to the comparative experiment, water droplets were generated. In other words, the film of the resin-based hydrophilic treatment agent of the comparative experiment is not sufficiently stable, and water droplets are formed after long-time use, thereby impeding the flow of air, thereby lowering heat exchange efficiency and cooling efficiency. However, the crystalline titania film of Example 1 does not cause any inconvenience due to the formation of water droplets.

A crystalline titania film and a film of a polyvinyl acetate-based hydrophilic treatment agent are formed on the same aluminum plate so as to have the same film thickness of 0.5 μm, and the thermal conductivity including each aluminum plate is formed. Was measured, the one coated with a crystalline titania film was 75 W / m ^-1 k ^-1 ,
On the other hand, those coated with a film of a polyvinyl acetate-based hydrophilic treatment agent had a power of 58 W / m ^-1 k ^-1 . The thermal conductivity of the aluminum plate alone was 236 W / m ^-1 k ^-1 , and the decrease in thermal conductivity was smaller when the aluminum plate was coated with a crystalline titania film.

[0025]

As described above, according to the present invention,
A hydrophilic and deodorant heat exchanger fin which has both hydrophilic performance and deodorant performance and has excellent durability can be provided by a simple method.

[Brief description of the drawings]

FIG. 1A is a view schematically showing heat exchanger fins, and FIG. 1B is a partially enlarged view showing an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heat exchanger fin 2 Heat exchanger main body 3 Heat transfer tube 4 Insertion hole 10 Fin substrate 11 Barrier film 12 Photocatalytic film

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yasunori 1500 Yazaki Sogyo Co., Ltd., Onjuku 1500, Susono City, Shizuoka Prefecture

Claims (4)

[Claims] 1. A heat exchanger fin comprising a fin substrate coated with a film containing a photocatalyst. 2. The heat exchanger fin according to claim 1, wherein the photocatalyst is titania. 3. A sol obtained by reacting a metal alkoxide, alcohol, water and a reaction accelerator is applied to a fin substrate, and the obtained wet gel film is dried and then crystallized. Manufacturing method of exchanger fins. 4. The method according to claim 3, wherein the metal alkoxide is an alkoxide of titanium.