JPH06300482A - Heat exchanger - Google Patents

Abstract

PURPOSE:To obtain an aluminum-made heat exchanger which has a specific film that is hydrophilic without producing water drops and able to restrain the growth of frost depositing. CONSTITUTION:A heat exchanger has a film which is formed by applying and drying a water-based treatment liquid containing one or more water soluble polymers (I) selected from polyvinyl alcohol and its derivatives, water-soluble polymers (II) containing at least one of primary, secondary and tertiary amino groups and quaternary ammonium group in a molecule, a crosslinking agent (III) which can be mixed with (I) and (II), and silica fine particles (IV) or one or more sorts of metallic compounds (V) selected from lithium, magnesium, and barium.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger made of aluminum or aluminum alloy used for domestic and commercial room air conditioners (hereinafter collectively referred to as "air conditioners"). More specifically, it is applied to the surface of aluminum and aluminum alloys (hereinafter collectively referred to as "aluminum") to impart excellent hydrophilicity to the surface to prevent the formation of water droplets and suppress the growth of frost that adheres. And a heat exchanger coated with the coating composition.

[0002]

2. Description of the Related Art In air conditioners, an air heat source heat pump system (hereinafter referred to as a heat pump) is becoming popular because of its advantages such as economy, clean heating, and space saving.
The heat radiating or cooling section of the heat exchanger used in the heat pump is made of aluminum fin material, and the surface area per unit volume is designed to be as large as possible in order to improve the heat exchange efficiency, and the fin spacing is extremely narrow. Therefore, during cooling operation, moisture in the atmosphere condenses on the fin surface, which is the heat transfer surface of the indoor unit, and the more hydrophobic the fin surface, the more easily the condensed water becomes water droplets, causing clogging in the fin gap. ,
Airway resistance increases, reducing thermal efficiency.

On the other hand, during heating operation, if the outside air temperature drops, frost forms on the fin surface of the outdoor unit, and the heating capacity drops.
Therefore, it is necessary to perform defrosting, and reverse cycle defrosting is generally performed. However, during this period, the heating operation must be temporarily stopped, which results in discomfort in the room. If the fin surface is hydrophobic, the water melted by the defrosting operation tends to remain between the fins, and when the heating operation is restarted, the remaining water re-freezes and reduces the heating capacity. In addition, since new frost is formed on the frozen residual water, the frequency of the defrosting operation is increased and the heating efficiency is significantly reduced.

Therefore, in order to improve the operation efficiency of the air conditioner, the hydrophilicity of the fin surface is increased to prevent the generation of water droplets on the fin surface during the cooling operation, and the high frost generated on the fin surface during the heating operation. It is necessary to keep the height as low as possible, and to make the time required for frost formation as long as possible.

In a heat exchanger of an air conditioner, as a means for reducing air passage resistance and improving thermal efficiency, a method of hydrophilizing a fin surface which is a heat transfer surface includes hydrophilic inorganic compounds such as water glass and silica sol. Various methods have been proposed in which an organic compound such as a surfactant or a water-soluble resin is used alone or in combination.

Of these methods, a method of using an organic polymer resin and silica in combination is disclosed in Japanese Patent Laid-Open No. 142426/1979.
"A method for surface treatment of an aluminum heat exchanger characterized by surface-treating with an organic polymer resin solution containing fine particles of porous silica", JP-A-55-164264, "Resin for water-based coating, surface active Agent, an aqueous coating composition containing a specific amount of synthetic silica ".

Organic polymer resins used in these,
Alternatively, the water-based coating resin itself is hydrophobic rather than hydrophilic, or is insufficient in hydrophilicity, or even if hydrophilic, the film dissolves in water. In these inventions, a hydrophilic surface is formed only by using silica in the resin film.
Furthermore, although the hydrophilicity in the initial state can be exhibited by the effect of silica, the immobilization of silica in the film is not taken into consideration, and it is considered that the silica may fall off due to dew condensation water.
The sustainability of performance cannot be expected. Further, no mention is made of the effect of silica for suppressing frost formation failure (the effect of preventing frost from forming on the fin surface in a bulky manner and increasing the airway resistance to reduce the operating efficiency of the air conditioner).

[0008]

DISCLOSURE OF THE INVENTION The present invention is to uniformly disperse silica particles having a specific particle size and a specified metal compound having good dispersibility in a hydrophilic organic film having excellent hydrophilicity for a long time. An object of the present invention is to provide a heat exchanger having a function of maintaining stable hydrophilicity by immobilizing and having a function of maintaining an excellent frosting disorder suppressing effect for a long period of time.

[0009]

The present inventors have found that the following method is effective for achieving the above object. For the heat transfer part of the aluminum heat exchanger, selected from polyvinyl alcohol and its water-soluble derivatives 1
At least one water-soluble polymer (I), a primary amino group in one molecule,
Water-soluble polymer (II), (I) containing at least one member selected from the group consisting of secondary amino group, tertiary amino group and quaternary ammonium group
The application of an aqueous treatment liquid containing a cross-linking agent (III) and silica fine particles (IV) that can be mixed with (2) and (II) is defined as the first invention, and one or more water-soluble agents selected from polyvinyl alcohol and water-soluble derivatives thereof are used. Polymer (I), a water-soluble polymer (II) containing at least one member selected from the group consisting of primary amino group, secondary amino group, tertiary amino group and quaternary ammonium group in one molecule, (II), I) and (II) and a crosslinkable agent (III) that can be mixed,
A second invention is applied with an aqueous treatment liquid containing fine silica particles (IV) and one or more metal compounds (V) selected from the group consisting of lithium compounds, magnesium compounds and barium compounds.

The polyvinyl alcohol and its water-soluble derivative (I) described here have the general formula

[Chemical 1] The polymer which can be represented by (1) is usually a water-soluble copolymer obtained by hydrolysis of vinyl acetate or its copolymer, or a water-soluble polymer obtained by further post-reacting these. Here, 1 is an integer of 50 to 100 and m is 0 to 50.
And n is an integer of 0 to 50, and R ₁ is H or CH ₃ . When X is an anionic substituent containing at least one of a galboxyl group, a sulfonic acid group and a phosphonic acid group, it is, for example, a copolymer with acrylic acid, methacrylic acid, maleic anhydride, vinylsulfone sun or the like. An anion-modified PVA is mentioned. Also included are those that become anionic by hydrolysis, such as methacryloxyethyl phosphate and acrylic acid ester. In the case of a cationic substituent, X is any of primary to tertiary amino groups or a quaternary ammonium group. next,
Examples of PVA-based materials include active methylene-modified products.
A reaction product of A and diketene, for example, acetoacetylated PV
There are A etc. In addition, X includes at least one of the above groups.

As the water-soluble derivative of PVA, in addition to the above structure, styrene, acrylonitrile, vinyl ether, and other nonionic polymerizable monomers copolymerized to the extent that water solubility is not impaired are also included.

The water-soluble polymer (II) is ethyleneimine,
Homopolymers such as N, N-dimethyl-N, N-diallylammonium salt or the like, or with these, acrylic acid, methacrylic acid, itaconic acid, maleic acid, vinyl sulfonic acid,
Styrene sulfonic acid, sulfoethyl acrylate, acrylamide, N-methylene sulfonic acid acrylamide,
2-acrylamido-2-methylpropanesulfonic acid,
Copolymers with polymerizable monomers such as N-methylolacrylamide, Hoffmann reaction products of polyacrylamide, polyacrylamide, Mannich modified products of polyvinylphenol, polyN-vinylphthalimide, polyvinylsuccinimide, hydrolysates of polyvinylisocyanate, Reduced products of polynitroethylene and its derivatives, quaternized ammonium salts, cationic nylons obtained by condensation reaction, cationic polyamides, epoxy-modified cationic polyamides, etc. having a primary amino group in one molecule. , A water-soluble polymer containing at least one selected from the group consisting of a secondary amino group, a tertiary amino group and a quaternary ammonium group.

Examples of the water-soluble organic cross-linking agent (III) include water-soluble blocked polyisocyanates, water-soluble polymethylols, polyglycidyls, polyaziridyl compounds and aldehydes, such as sodium bisulfite-blocked isocyanate and methylolmelamine. , Methylolurea, methylolated polyacrylamide, diglycidyl ether of polyethylene oxide, diaziridylated polyethylene oxide glyoxal and the like, which can be mixed with (I) and (II).

The silica fine particles (IV) are powdered silica or silica sol produced by a wet method or a dry method, and have a primary particle size of 0.005 to 50 μm, preferably 0.01 to 10 μm.

The lithium compounds include LiF and LiC.
l, LiBr, LiI, LiNO₃, Li₂CO₃, L
i₃PO_Four, LiMnO_Four, Li₂Cr₂O₇, Li_Four
SiO_Four, Li₂SiO₃, LiBO₂, Li₃V
O_Four, Li₂WO_Four, HCOOLi, Li₂C₂O_Four,
CH₃COOLi, C₂H_FiveCOOLi, LIOOCC
H ₂COOLi, lithium citrate, lithium tartrate,
Lithium trimellitic acid, lithium pyromellitic acid,
MgF compound is MgF₂, MgCl₂, M
gBr₂, MgI₂, Mg (NO₃)₂, MgCO₃,
Mg₃(PO_Four)₂, Mg (MnO_Four)₂, MgCr₂
O₇, Mg₂SiO_Four, MgSiO₃, Mg (BO₂)
₂, Mg₃(VO_Four)₂, MgWO_Four, (HCOO)₂
Mg, MgC ₂O_Four, (CH₃COO)₂Mg, (C₂
H_FiveCOO)₂Mg, magnesium oxalate, citric acid
Magnesium, magnesium tartrate, trimellitic acid
Gnesium, magnesium pyromellitic acid, barium conversion
As a mixture, BaF₂, BaCl₂, BaBr₂, B
aI₂, Ba (NO₃)₂, BaCO₃, Ba₃(PO
_Four)₂, Ba (MnO_Four)₂, BaCr₂O₇, Ba₂
SiO_Four, BaSiO₃, Ba (BO₂)₂, Ba
₃(VO_Four)₂, BaWO_Four, (HCOO)₂Ba, B
aC₂O_Four, (CH₃COO)₂Ba, (C₂H_FiveCO
O)₂Ba, barium oxalate, barium citrate, liquor
Barium tartrate, barium trimellitate, pyromerit
Examples thereof include barium acid.

These can be used alone or in combination of two or more. The silica fine particles (IV) and the metal compound (V) are used after being subjected to a special surface treatment in order to improve the dispersibility. In addition to this, rust inhibitor,
Fillers, colorants, surfactants, defoamers, leveling agents,
Antibacterial and antifungal agents and the like may be added within the scope of the purpose of the present application and the range of not impairing the film performance.

As the coating method, dipping, spraying, rolling,
A flow coat method or the like is used. The concentration and the viscosity are appropriately selected depending on the coating method used, the desired film thickness and the like. The coating thickness is 0.0 to improve thermal efficiency.
The thickness is preferably 5 to 10 μ, and more preferably 0.2 to 2 μ. In this case, silica having a particle size larger than the film thickness protrudes from the film surface and is fixed to the film.

Aluminum may be subjected to degreasing treatment in advance and then directly applied or subjected to chemical conversion treatment such as boehmite treatment and chromate treatment, and then treated with a suitable primer such as acrylic resin type, urethane resin type and epoxy resin type. After applying the treatment, the treatment agent may be applied. Drying is generally 90-
It is carried out at 300 ° C, more preferably 100 to 250 ° C.

[0019]

The film of the present invention has excellent hydrophilicity for a long time,
The heat transfer part of the aluminum heat exchanger is provided with a function of continuing the effect of suppressing the frost formation disorder. In this film,
The tertiary amino group or quaternary ammonium group in the polymer imparts hydrophilicity, and the polymer having these functional groups is a network resin and IPN highly crosslinked by the reaction of the PVA-based polymer and the crosslinking agent. (Inter Penet
A hydrophilic network is formed, and hydrophilic groups are constantly transferred to the surface of the coating film, or a very small portion of the hydrophilic group is dissolved to maintain the hydrophilicity. Therefore, the water-soluble polymer
The organic film obtained by the reaction with (I), the water-soluble polymer (II), and the organic cross-linking agent (III) has excellent hydrophilicity and hydrophilic durability.

Silica particles, Li, added in the coating
The effect of suppressing the frosting disorder of the Mg and Ba compounds is considered as follows. First, the process of frost formation will be described. When the heat exchanger operates in a state where the heat transfer surface temperature is lower than 0 ° C., water in the air is condensed to generate supercooled water droplets on the heat transfer surface, and the water droplets grow to a certain size while being supercooled for a while. When water droplets grow, adjacent water droplets often coalesce, which stimulates the water droplets to freeze and become ice crystal nuclei. In addition, water droplets become ice crystal nuclei due to various causes such as some irritation from the air. After becoming ice crystal nuclei, crystals on the dendrites gradually form from the surface of the nuclei, and a frost layer is formed. In addition to frost formation starting from supercooling, sublimation may directly generate ice crystal nuclei on the heat transfer surface, but it is considered that frost formation due to sublimation is small in the operation of an air conditioner or a refrigerator.

The above is the process of frost formation. When the amount of frost increases, the pressure loss of the heat exchanger increases and the air volume decreases, making it difficult to obtain a predetermined amount of heat exchange. . In order to control such an obstacle due to frost formation, it is first necessary to reduce the frost formation height as much as possible, that is, increase the frost formation density. Since the frost layer is generated from the freezing of supercooled water droplets as described above, it is considered that the number of crystal nuclei, and thus the number of supercooled water droplets, should be increased in order to increase the frost density.

Therefore, in order to increase the number of supercooled water drops, it is necessary to increase the number of sites where water molecules are adsorbed in the film on the heat transfer surface. To this end, in the present invention, compounds of silica particles Li, Mg, and Ba that have been subjected to a special surface treatment and have good dispersibility are added in order to uniformly distribute them in the film. When water in the air is condensed, the silanol groups of the silica particles have a strong bonding force with water molecules and strongly adsorb condensed water. As a result, the silica particles serve as an adsorption site for water molecules, so that the number of crystal nuclei increases and the frost height can be controlled to be low. Since the hydration energy of the ions was large, the Li, Mg, and Ba compounds had the same effect. It is considered that the silica fine particles added to the present film are fixed in the film by dehydration reaction with the amino groups in the resin, and therefore the frost damage prevention effect can be maintained without dropping off due to dew condensation water.

[0023]

The present invention will be described below with reference to examples. Using the hydrophilicity-imparting organic polymer resin base samples having the treatment liquid compositions shown below, treated plate samples having the contents shown in Examples 1 to 6 and Comparative Examples 1 to 3 were prepared, and FACE contact angle meter CA- Hydrophilicity was evaluated by using P type (manufactured by Kyowa Interface Science Co., Ltd.) and measuring the contact angle of the sample surface immediately after the treatment and after immersion in running water for 72 hours at room temperature. The results are shown in Table 1. Regarding the frosting disorder suppression effect, Examples 1 to 6 and Comparative Examples 1 to 3
The treated sample of No. 1 was cut into a 50 mm square, the untreated aluminum surface was brought into close contact with the cooling plate, and the air temperature was + 2 ° C., the relative humidity was 80%, the air flow rate was 1 m / sec. , Aluminum surface temperature-5
A frosting test was performed under frosting conditions of ℃ and frosting time of 2 hours, and the amount of frost and the height of frost were measured. Examples 1 to 6 and Comparative Example 1 with the amount of frost on the untreated surface, the height of frost, and the frost density being 1
Table 2 shows the results of comparing the frost formation amount, the frost formation height, and the frost formation density generated on the treated sample surfaces of Nos. 3 to 3.

<Base Sample 1> 60 parts by weight of PVA (Nippon Gosei Kagaku Kogyo Co., Ltd., Gohsenol CH-20), 30 parts by weight of cationic polyamide (Mitsui Toatsu Chemical Co., Ltd., Euramine P5600), water soluble Sexual melamine (Mitsui Cyanamid Co., Ltd., Cymel 350) 10 parts.

<Base sample 2> 70 parts by weight of cation-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., Gohsefimer K), amphoteric polyacrylamide (manufactured by Showa Polymer Co., Ltd.),
20 parts by weight of cogum 205), 10 parts by weight of glyoxal.

Example 1 A 1 mm thick aluminum plate (A1100) that had been degreased and washed
The material was bar-coated with a heat-effect type urethane resin-based primer (Paltop 3975, manufactured by Nippon Parkerizing Co., Ltd.) to a thickness of about 1 μm, and heated and dried at 160 ° C. for about 3 minutes. On this film, 30% by weight of silica particles having an average particle size of 5 μm was added and dispersed with respect to the solid content of the base sample 1, and the dispersion was bar-coated to a film thickness of about 1 μm.
It was dried by heating at 30 ° C. for about 3 minutes.

Example 2 The same material as in Example 1 was applied with the same primer, and 30% by weight of silica particles having an average particle diameter of 0.05 μ was added and dispersed on the solid content of the base sample 1. Bar coating the dispersion to a film thickness of approximately 1μ
It was dried by heating at 0 ° C. for about 3 minutes.

Example 3 The same material as in Example 1 was applied with the same primer, and 20% by weight of silica particles having an average particle size of 1 μ and 10% by weight of LiF were added to the solid content of the base sample 1 on this plusmer. Was added and dispersed to form a dispersion having a film thickness of about 1 μm, which was bar-coated and dried by heating at 230 ° C. for about 3 minutes.

Example 4 The same material as in Example 1 was applied with the same primer, and 20% by weight of silica particles having an average particle size of 1 μ and 10% by weight of MgCO ₃ were added to the solid content of the base sample 1. %, And the dispersion was dispersed by bar coating to a film thickness of about 1 μm and dried by heating at 230 ° C. for about 3 minutes.

Example 5 The same material as in Example 1 was applied with the same primer, and on this primer, 20% by weight of silica particles having an average particle size of 1 μ and 20% by weight of BaSO ₄ with respect to the solid content of the base sample 2. %, And the dispersion was dispersed by bar coating to a film thickness of about 1 μm and dried by heating at 230 ° C. for about 3 minutes.

Example 6 The same material as in Example 1 was applied with the same primer, and 5% by weight of silica particles having an average particle size of 1 μm and 5% by weight of lithium silicate based on the solid content of the base sample 2 were applied on this primer.
The dispersion liquid to which 0% by weight was added and dispersed was bar-coated to a film thickness of about 1 μm, and dried by heating at 230 ° C. for about 3 minutes.

Comparative Example 1 The same material as in Example 1 was applied with the same primer, and the primer was bar-coated with the composition of only the base sample 1 to a film thickness of about 1 μm and heated at 230 ° C. for about 3 minutes. Dried.

Comparative Example 2 The same material as in Example 1 was applied with the same primer, and the primer was bar-coated on the primer with the composition of the base sample 2 only to a film thickness of about 1 μm and heated at 230 ° C. for about 3 minutes. Dried.

Comparative Example 3 The same material as in Example 1 was applied with the same primer, and an aqueous solution of PVA (Gosenol GH-20, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was applied on this primer and dried by heating at 200 ° C. did.

Comparative Example 4 The same material as in Example 1 was applied with the same primer, and an aqueous solution of PVA (Nippon Gosei Kagaku KK, Gohsenol GH-20) aqueous solution was applied onto this primer to give an average particle diameter of 0.02 μm.
20% by weight of the silica particles of the above was added to the PVA solid content and dispersed, and the resulting dispersion was applied, and dried by heating at 200 ° C.

Comparative Example 5 The same material as in Example 1 was degreased.

Example 7 Practical heat exchanger (fin pitch 1.7 mm, fin width 22 mm, pipe diameter 9.52 mm, stage pitch 5.4 mm, number of rows 1)
After degreasing the column, thermosetting urethane resin-based primer (Nippon Parkerizing Co., Ltd., Paltop 397)
5) was applied by dip coating to a thickness of about 1 μm, and dried by heating at 160 ° C. for 20 minutes. On this primer, Example 3
The dispersion described in 1 above was applied by dip coating to a film thickness of about 1 μm, and dried by heating at 230 ° C. for 20 minutes.

Comparative Example 6 A heat exchanger similar to that of Example 7 was subjected to the same primer treatment as in Example 7, and the dispersion liquid described in Comparative Example 1 was applied by dip coating to a film thickness of about 1 μm. Heat dried for minutes.

Comparative Example 7 The same heat exchanger as in Example 7 was degreased.

In the heat exchanger of Example 7, the air temperature was 2 ° C., the relative humidity was 80%, the refrigerant temperature was −6 ° C., the initial front wind speed was 1 m / se.
c. The frosting test was conducted under the frosting conditions of The blower rotation speed was constant during the experiment. The comparison of the air passage resistance with the heat exchangers of Comparative Examples 6 and 7 is shown in FIG.

[0041]

[Table 1]

[0042]

[Table 2]

From Table 1, Comparative Example 3 is a single film of PVA, but the hydrophilicity of this film is not high. In Comparative Example 4 in which silica is dispersed therein, the hydrophilicity immediately after the treatment is good, but the sustainability is long. It turns out that he lacks strength. On the other hand, the hydrophilicity of the systems obtained by removing the silica or the metal compound from the coatings of the present invention of Comparative Examples 1 and 2 is good, and the hydrophilic durability of Examples 1 to 6 of the present invention is further excellent. I understand.

From Table 2, Comparative Examples 1 and 2, which have relatively good hydrophilicity, have a frost formation height and a frost formation density obtained by dividing the frost formation amount by the frost formation height, which is almost 1 without any treatment. Almost the same as a plate, the effect of reducing air resistance cannot be expected. Compared with this, Examples 1 to 6 of the present invention containing silica and a specific metal compound
The frost formation height is low and the frost formation density is 20 to 61% larger, and the effect of suppressing frost formation is recognized. As shown in FIG. 1, the treated material of the present invention described in Example 7 has a higher frost density and a lower frost height than the untreated material.
The air passage resistance is reduced, the front wind speed (the air inflow speed into the heat exchanger) is suppressed from decreasing, and the air volume is increased.

[0045]

As can be seen from the above, the heat exchanger of the present invention has excellent hydrophilicity, long-lasting hydrophilicity, and excellent frost damage inhibiting effect, and is extremely useful.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between front wind speed and time in a frosting test for each heat exchanger of Example 7, Comparative Example 6, and Comparative Example 7.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical indication location C09D 129/04 PFN 6904-4J (72) Inventor Takao Kawamoto 3-18-1 Oga, Shizuoka-shi, Shizuoka No. Mitsubishi Electric Co., Ltd. Shizuoka Works (72) Inventor Mitsuru Ikegaya 3-18-1, Oka Shizuoka City, Shizuoka Prefecture Mitsubishi Electric Co., Ltd. Shizuoka Works (72) Inventor Tomomasa Takeshita 3-18, Oka Shizuoka City, Shizuoka Prefecture No. 1 Mitsubishi Electric Corporation Shizuoka Factory

Claims (2)

[Claims] 1. One or more water-soluble polymers (I) selected from polyvinyl alcohol and water-soluble derivatives thereof, wherein a primary amino group, a secondary amino group, a tertiary amino group and a quaternary ammonium are included in one molecule. A cross-linking agent (I) which is miscible with the water-soluble polymers (II), (I) and (II) containing at least one selected from the group of groups
A heat exchanger made of aluminum or an aluminum alloy, which has a coating formed by applying an aqueous treatment liquid containing II) and silica fine particles (IV) and drying. 2. One or more water-soluble polymers (I) selected from polyvinyl alcohol and water-soluble derivatives thereof, wherein a primary amino group, secondary amino group, tertiary amino group and quaternary ammonium are included in one molecule. A cross-linking agent (I) which is miscible with the water-soluble polymers (II), (I) and (II) containing at least one selected from the group of groups
II), silica fine particles (IV) and an aqueous treatment liquid containing at least one metal compound (V) selected from the group consisting of lithium compounds, magnesium compounds and barium compounds,
A heat exchanger made of aluminum or an aluminum alloy having a film formed by drying.