JPH112497A - Heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent condensate from invading a clearance between a heat transfer pipe and collar part of a fin by applying water repellent treatment to at least either one of an outer face of the heat transfer pipe or an inner face of the fin collar part and not applying the water repellent treatment to faces of the fins other than the inner face of the collar part. SOLUTION: A water-repellent coating 2 is formed on an outer face of a heat transfer pipe 1 and even if condensate is formed on a surface of a precoated fin 3 and retained in a vicinity of the heat transfer pipe, the condensate is hard to intrude into and adhere to a clearance between the heat transfer pipe 1 and a collar part 4 of the fin so that corrosion of the heat transfer pipe 1 is suppressed. And because hydrophilic coating is formed on the surface of the fin and therefore the condensate is hard to form a drop of water, the condensate hardly has a possibility of being scattered and wetting an interior of a room. Because the outer face of the heat transfer pipe is subjected to water repellent treatment, contact area between the heat transfer pipe and the condensate is very small and corrosion of the heat transfer pipe is surely suppressed even if the condensate is formed directly on the outer surface of the heat transfer pipe.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger which has excellent corrosion resistance and can be used for a long time.

[0002]

2. Description of the Related Art Heat exchangers are used in indoor units and outdoor units of air conditioners, and indoor units of air conditioners using cold and hot water. The structure of the heat exchanger is a cross fin type in which heat transfer tubes are expanded and joined to fins. Is the mainstream. The fins are mainly made of aluminum or an aluminum alloy, and the heat transfer tubes are mainly made of copper or a copper alloy. Such a heat exchanger is, for example, a color that passes a heat transfer tube through an aluminum strip.
The fins are formed by press working to form fins, a plurality of the fins are laminated with the collar portions aligned, a heat transfer tube is inserted into the collar portion of the laminate, and the heat transfer tube is expanded to form a fin collar. It is manufactured by a method of mechanically joining to the part. By the way, in the indoor unit during the cooling operation and in the outdoor unit during the heating operation, dew condensation occurs on the surface of the heat exchanger, and when the dew forms, a bridge is formed between the fins due to water droplets. Since this bridge increases ventilation resistance, the cooling and heating capacity is reduced.
For this reason, precoated fins whose entire surface is subjected to a hydrophilic treatment for preventing dew condensation are widely used.

[0003]

However, in a heat exchanger using a hydrophilic precoat fin, dew water easily enters the gap between the fin collar and the heat transfer tube and adheres to the heat exchanger. There is a problem that when the corrosive medium therein is dissolved, corrosion of the heat transfer tube is accelerated and the refrigerant leaks. Corrosion caused by the dew water can occur not only when aluminum fins and copper heat transfer tubes are combined but also when fins and heat transfer tubes are combined with various metal materials such as copper, aluminum, and iron. When the corrosive medium dissolved in the attached water is carboxylic acid, ant nest corrosion occurs in the heat transfer tube of the copper or copper alloy tube, and the refrigerant starts to leak in a relatively short period of time. Since the carboxylic acid is generated even when aldehyde or alcohol generated from the adhesive for plywood or cloth is oxidized, the indoor unit of the air conditioner has a high risk of being used in an environment containing a corrosive medium. .

On the other hand, as a method of preventing frost formation between the fins generated in the outdoor unit during the heating operation, water repellency is applied to the entire surface of the fin, or both the entire surface of the fin 6 and the outer surface of the heat transfer tube 1 as shown in FIG. A method for forming the film 2 has been proposed (Japanese Patent Application Laid-Open No. 6-123576). However, when this method is applied to an indoor unit during a cooling operation, there is a problem that as the water repellency deteriorates with time, water droplets condensed on the surface of the aluminum fins scatter and the interior becomes wet.

Meanwhile, in a cross-fin type heat exchanger in which a heat transfer tube is expanded and joined to a fin, the interval between the fins tends to be narrowed in order to reduce the size of the heat exchanger. Recently, as shown in FIG. The heat transfer tube 1 is provided with a color of the fin 6.
It is covered with the part 4 so that it is not exposed. Therefore, the ant nest-like corrosion of the heat transfer tube 1 occurs because dew condensation water enters and adheres to the gap between the heat transfer tube 1 and the fin collar portion 4.
Further, it is limited to a case where a corrosive medium such as a carboxylic acid is dissolved in the attached water. From these facts, the present inventors have found that it is only necessary to apply the water repellent treatment to the inner surface of the fin (the surface to be joined to the heat transfer tube) on the fin, and further research to complete the present invention. Reached. An object of the present invention is to provide a heat exchanger in which ant nest-like corrosion is unlikely to occur and water droplets are not scattered even when used for a long time.

[0006]

According to the first aspect of the present invention,
In a heat exchanger having a structure in which a fin and a heat transfer tube are mechanically joined, at least one of an outer surface of the heat transfer tube or an inner surface of a collar portion of the fin (a surface to be joined to the heat transfer tube) is subjected to a water-repellent treatment. The heat exchanger is characterized in that a water repellent treatment is not applied to a surface other than the inner surface of the collar portion of the fin.

A second aspect of the present invention is the heat exchanger according to the first aspect, wherein a surface other than the inner surface of the collar portion of the fin is subjected to a hydrophilic treatment.

According to a third aspect of the present invention, the heat transfer tube is made of copper or a copper alloy, and the fin is made of aluminum or an aluminum alloy.
Or the heat exchanger according to 2.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a partially enlarged longitudinal sectional view showing a first embodiment of the present invention. A water-repellent coating 2 is formed on the outer surface of the heat transfer tube 1. For this reason, even if dew condensation water is generated on the surface of the precoat fins 3 and accumulates near the heat transfer tubes, it is unlikely that the water will enter the gap between the heat transfer tubes 1 and the collar portions 4 of the fins and adhere to it. Corrosion of the heat tube 1 is suppressed. In addition, since a hydrophilic film is formed on the surface of the fin, the dew condensation water hardly forms water droplets, and the dew condensation water is unlikely to scatter and wet the room. In addition, since the outer surface of the heat transfer tube is water-repellent, even if dew condensation occurs directly on the outer surface of the heat transfer tube, the contact area between the heat transfer tube and the condensed water is extremely small, and the corrosion of the heat transfer tube is more reliable. Is suppressed.

FIG. 2 is a partially enlarged longitudinal sectional view showing a second embodiment of the present invention. The water-repellent film 2 is formed only on the inner surface of the fin collar portion 4 which is in contact with the outer surface of the heat transfer tube 1, and the water-repellent film is not formed on the outer surface of the heat transfer tube 1. Pleco
When the tofin 3 is used, it is more advantageous in terms of manufacturing cost to perform a water-repellent treatment on the inner surface of the fin collar portion 4 without removing the hydrophilic film 5.

FIG. 3 is a partially enlarged longitudinal sectional view showing a third embodiment of the present invention. A water-repellent coating 2 is formed on both the outer surface of the heat transfer tube 1 and the inner surface of the fin collar portion 4. In this case, since water repellent treatment is applied to both the outer surface of the heat transfer tube 1 and the inner surface of the fin collar portion 4, dew condensation water enters the gap between the heat transfer tube 1 and the collar portion 4 of the fin and adheres thereto. Is more reliably suppressed, and the heat transfer tube has extremely high corrosion resistance.

In the present invention, it is preferable that a surface other than the inner surface of the collar portion of the fin is subjected to a hydrophilic treatment from the viewpoint of preventing dew condensation water from being bridged and dew condensation water from being scattered.
As shown in FIG. 4, the water-repellent agent preferably has a contact angle θ with water of 90 ° or more. In consideration of the heat transfer performance of the heat exchanger, the total thickness of the water-repellent film formed between the heat transfer tube and the fin collar portion is desirably 10 μm or less. In the present invention, the inner surface of the collar portion of the fin to be subjected to the water-repellent treatment is the surface to be joined to the heat transfer tube, but it is desirable to perform the water-repellent treatment also in the vicinity thereof.

[0014]

The present invention will be described below in detail with reference to examples. (Example 1) Aluminum fins were formed by pressing two rows x 12 collars on an aluminum strip (JIS-A1200, 500 x 25 x 0.1 mm) to form aluminum fins. The phosphorous deoxidized copper tube (JIS-C1220, outer diameter 7 mm, wall thickness 0.3 mm) is inserted through the collar part of the laminated body, and then the phosphorus deoxidized copper tube is expanded with a mandrel. To form a cross-fin type heat exchanger (external dimensions 500 × 25 × 250 mm). The water repellent treatment was applied to the outer surface of the phosphor deoxidized copper tube, the inner surface of the fin collar, or both. In the case of precoat fins, a water repellent treatment was applied on the hydrophilic film.

The heat transfer performance and corrosion resistance of each of the obtained heat exchangers were examined. [Heat transfer performance] The air side heat exchange during evaporation was measured and examined under the following conditions. Refrigerant in pipe: R-22, dry bulb temperature of inlet air: 27.0
° C, wet bulb temperature: 19.0 ° C, wind speed: 1 m / sec, outlet refrigerant evaporation pressure: 5.4 Kg / cm ² , refrigerant temperature before expansion valve: 4
0.0 ° C, outlet refrigerant superheat: 5.0 ° C. [Corrosion resistance] Sample from heat exchanger (external size 100 × 25 × 150m
m) was cut out and exposed to the gas phase of a desiccator filled with an aqueous solution of 1 vol% formic acid for 1 month, and the outer surface of the heat transfer tube in contact with the fin collar was exposed to ant-nest corrosion. investigated. A similar investigation was conducted for conventional products.

The results are shown in Table 1. Table 1 also shows the conditions of the water-repellent treatment and the hydrophilic treatment. In the table, A is a water-repellent fluororesin film, B is a water-repellent silicone resin film, C is a water-repellent paraffin film, D is a hydrophilic water glass film,
Parent E is a hydrophilic acrylic resin film, and parent F is a hydrophilic cellulose resin film. Numerical values, for example, 5/100, the upper part represents the film thickness (μm) and the lower part represents the contact angle (degree) of the film with water. No treatment / 75 does not perform water repellent treatment or hydrophilic treatment,
The lower numerical values represent the contact angle (degree) between the untreated heat transfer tube outer surface or the fin surface and water.

[0017]

[Table 1] (Note) The contact angle was measured for a plate made of the same material as the heat transfer tube. The contact angle was measured by cutting out the collar part and making it flat. The contact angle was measured on the fin strip before pressing. Ant nest corrosion depth. Relative value based on No. 9 of conventional products.

As is clear from Table 1, the products of the present invention (N
In o.1 to 8), ant's nest-like corrosion occurred partially, but the degree was very small and of a degree that would not be harmful in practical use. Above all, No. 6 to 8 in which the water-repellent coating was formed on both the outer surface of the heat transfer tube and the inner surface of the fin collar did not cause any nest corrosion. The heat transfer performance was equal to or better than the conventional product.
On the other hand, the comparative example product did not undergo the water repellent treatment, so that the ant nest-like corrosion advanced deeply.

(Embodiment 2) The heat exchanger assembled in Embodiment 1 was used for an indoor unit during a cooling operation. However, good cooling performance was maintained and no water droplets were scattered during use. Was. A conventional heat exchanger (see FIG. 5) having the entire surface of the fins subjected to a water-repellent treatment was used in the same manner, but in this heat exchanger, water droplets began to scatter from a certain time. This is because the water repellency of the fins deteriorated with time, and the dew water generated on the fin surfaces was scattered.

[0020]

As described above, in the heat exchanger of the present invention, at least one of the outer surface of the heat transfer tube and the inner surface of the fin collar portion is subjected to the water-repellent treatment. It does not penetrate into and adhere to the gap with the part, and ant nest-like corrosion is unlikely to occur on the heat transfer tube. In addition, since the fins are subjected to the water-repellent treatment only on the inner surface of the collar portion which is in contact with the heat transfer tube, scattering of water droplets due to temporal deterioration of the water-repellency is suppressed. When the surface of the fin other than the inner surface of the collar portion is subjected to the hydrophilic treatment, the scattering of the water droplet is more reliably suppressed.

[Brief description of the drawings]

FIG. 1 is a partially enlarged longitudinal sectional view showing a first example of a heat exchanger of the present invention.

FIG. 2 is a partially enlarged longitudinal sectional view showing a second example of the heat exchanger of the present invention.

FIG. 3 is a partially enlarged longitudinal sectional view showing a third example of the heat exchanger of the present invention.

FIG. 4 is an explanatory diagram of a contact angle between a water-repellent film and water.

FIG. 5 is a partially enlarged longitudinal sectional view of a conventional heat exchanger.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 heat transfer tube 2 water repellent film 3 pre-coated fin 4 fin collar 5 hydrophilic film 6 fin

Claims (3)

[Claims] In a heat exchanger having a structure in which a fin and a heat transfer tube are mechanically joined, at least one of an outer surface of the heat transfer tube or an inner surface of a collar portion of the fin (a surface to be joined to the heat transfer tube) is repelled. A heat exchanger characterized by being subjected to a water treatment and not being subjected to a water-repellent treatment on surfaces other than the inner surface of the collar portion of the fin. 2. The heat exchanger according to claim 1, wherein a surface of the fin other than the inner surface of the collar portion is subjected to a hydrophilic treatment. 3. The heat exchanger according to claim 1, wherein the heat transfer tube is made of copper or a copper alloy, and the fin is made of aluminum or an aluminum alloy.