JP2006023019A - Fin-and-tube type heat exchanger and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To exhibit an excellent adhesion property or anticorrosive effect even in a highly corrosive environment in painting of a fin-and-tube type heat exchanger used for a refrigerator or the like. <P>SOLUTION: This heat exchanger comprises a number of fins 12 arranged in parallel at fixed intervals, U-shaped tubes 13 inserted at right angles to the fins 12, in which a fluid flows, and a return bend 14 mutually connecting the U-shaped tubes 13. A part increased in surface area of the return bend 14 by making the surface to a finely irregular shape 15 is subjected to painting. According to this, even if the heat exchanger is placed in a highly corrosive environment, and a sulfur-based or carboxylic corrosive substance gradually intrudes into the paint film layer, the adhesion of the paint film can be kept by the effect of increasing the surface area without causing floating of the paint film, and the corrosion is not promoted. Thus, an excellent anticorrosive effect can be exhibited to maintain the operation for a long period as a refrigeration system. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fin-and-tube heat exchanger used for a refrigerator or the like.

  In general, fin-and-tube heat exchangers (evaporators) for refrigerators are exposed to the atmosphere in the cabinet. Especially, commercial refrigerators store a large amount of food that generates highly corrosive gas in the cabinet. However, compared with a refrigerator for home use, there are many cases where food is not wrapped or the like, and thus highly corrosive gas is likely to be generated. For example, sulfur-based gas is generated from eggs, mayonnaise, cheese, seafood, and the like, and carboxylic acids (organic acids such as acetic acid and formic acid) are generated from mayonnaise, sauce, baker's yeast, and the like. In addition, when food rots, proteins and fats and other organic substances possessed by the food itself undergo oxidative decomposition and hydrolysis, generating sulfur-based gas, carboxylic acid, ammonia gas, and ethylene gas.

  Recently, bleaching agents, bactericides, or alcohol for disinfection have been used more frequently than the problem of pathogenic E. coli O-157. Bleaching agents and disinfectants use sodium hypochlorite and generate chlorine-based gases. Disinfecting alcohol generates carboxylic acid by oxidative decomposition. Thus, corrosive gas enters the inside of the refrigerator from the outside of the refrigerator when the refrigerator door is opened and closed.

  If the interior is exposed to the corrosive environment as described above, sulfur, which is a corrosion medium, carboxylic acid such as formic acid or acetic acid, chlorine, etc., dissolves in the condensed water generated when the refrigerator is cooled, and further defrosts. This causes repeated drying and wetting, and corrosion of fins and tubes begins. When corrosion begins, corrosion products such as white rust, black rust and patina are generated. When such a corrosion product is generated, the corrosion product is peeled off and blown off by the wind from the fan, and there is a problem that the product value is lost by adhering to the food in the warehouse. Further, when the corrosion is accelerated, the tube is pitted due to the action of the corrosion cell, eventually leading to a refrigerant gas leak, leading to a fatal defect that the tube cannot be cooled.

  Conventionally, as a technique for preventing corrosion of the fin-and-tube heat exchanger as described above, a rust preventive paint is mainly applied to the entire surface of the heat exchanger after the heat exchanger is assembled (for example, see Patent Document 1). ).

  Hereinafter, a conventional technique will be described with reference to the drawings.

  FIG. 3 is a schematic configuration diagram of a conventional fin-and-tube heat exchanger, and FIG. 4 is a cross-sectional view of a main part of the conventional fin-and-tube heat exchanger.

  As shown in FIG. 3, the conventional fin-and-tube heat exchanger 1 includes a large number of fins 2 arranged in parallel at regular intervals, and a U-shape in which fluid flows through the inside inserted at right angles to the fins 2. A U-shaped tube 3 and a return bend 4 for connecting the U-shaped tubes 3 to each other. By expanding the U-shaped tube 3, the U-shaped tube 3 and the fin 2 are brought into close contact with each other. Welding is performed to connect the distal end of the U-shaped tube 3 and the return bend 4 to form a circuit through which fluid flows.

  And the coating-film layer 5 is formed by baking-coating a rust-proof coating material by coating systems, such as a dip coating system or a spray coating system, on this fin and tube type heat exchanger 1 whole surface.

  The coating layer 5 is generally baked and coated by 5 to 25 μm, 1 coat 1 bake or 2 coat 2 bake.

  Usually, about the fin 2 and the U-shaped tube 3 in which the fin 2 is inserted, there is little heat influence at the time of welding, and a favorable coating layer is formed.

On the other hand, as shown in FIG. 4, the surface of the return bend 4 is affected by the influence of heat when the tip of the U-shaped tube 3 and the return bend 4 are welded and the influence of the generated oxide scale (including oxide film). It becomes the coating-film layer 5 which applied the antirust coating as received. In places where the corrosive environment is severe, this oxide scale may be removed and painted, but an oxide film residue remains on the surface.
JP 2003-139485 A

  However, the coating film layer coated on the return bend is inferior to the coating film adhesion of fins and U-shaped tubes due to the influence of heat during welding and the influence of oxide scale (including oxide film). In general environments, there is no problem with the adhesion of the return bend coating, but corrosive substances such as sulfur and carboxylic acid gradually enter the coating layer in highly corrosive environments such as sulfur and carboxylic acids. However, the coating of the return bend cannot withstand, and as a result, the floating of the coating (blister) is generated, the effect as a coating is lost, corrosion is accelerated, and there is a problem of pitting corrosion.

  The present invention solves the above-mentioned conventional problems, and by applying a coating layer coated with a rust-preventive paint at a location where the surface area of the return bend is finely uneven and increased in a highly corrosive environment. Even if it is placed, the adhesion of the coating film is maintained by the effect of increasing the surface area, so there is no occurrence of coating floating and corrosion and corrosion is not accelerated. An object is to provide a mold heat exchanger.

  In order to solve the above-described conventional problems, the fin-and-tube heat exchanger of the present invention is a coating in which the surface of the return bend is finely uneven and the surface area is increased.

  As a result, even when placed in a highly corrosive environment, the degree of adhesion of the coating film is maintained by the effect of increasing the surface area, so that the coating film does not float and corrosion is not promoted.

  The fin-and-tube heat exchanger of the present invention is placed in a highly corrosive environment by coating the surface of the return bend with fine irregularities and increasing the surface area. Even when corrosive substances such as systems and carboxylic acids gradually invade, the adhesion of the coating film is maintained by the effect of increasing the surface area, so there is no occurrence of coating film floating and corrosion is not promoted An excellent anticorrosion effect can be exhibited, and the operation as a refrigeration system can be maintained for a long time.

  The invention described in claim 1 includes a large number of fins arranged in parallel at regular intervals, a U-shaped tube through which fluid flows through an inside inserted perpendicularly to the fins, and the U-shaped tube. The surface of the return bend is processed into fine irregularities, and the surface area is reduced to fine irregularities even when placed in a highly corrosive environment. Since the coating film adhesion is maintained by the effect of increasing the coating film, there is no occurrence of coating film floating and corrosion is not promoted, so that an excellent anticorrosive effect can be exhibited.

  The invention according to claim 2 is the invention according to claim 1, wherein the fins and the U-shaped tube are coated on the surface processed into fine irregularities, and the fins and U-shaped The coating adhesion of the tube-like tube can be further improved, and the anticorrosion effect of the entire fin-and-tube heat exchanger can be enhanced.

  The invention according to claim 3 is a large number of fins arranged in parallel at regular intervals, a U-shaped tube through which fluid flows in an interior inserted perpendicularly to the fins, and the U-shaped tube A fin and tube type heat exchanger having a surface of the return bend processed into fine irregularities before the surface of the return bend is coated, and a highly corrosive environment. Even when placed underneath, the coating adhesion is maintained by the effect of increasing the surface area by making fine irregularities, so there is no occurrence of coating float and corrosion is not accelerated, so excellent anti-corrosion effect Can be demonstrated.

  According to a fourth aspect of the invention, there is provided the method according to the third aspect of the invention, wherein the method of making the surface of the return bend uneven is obtained by etching or chemical conversion treatment of the surface with a chemical or the like, The surface area can be increased.

  The invention according to claim 5 is the invention according to claim 3, wherein the method of making the surface of the return bend uneven is an automatic device such as an air blast injection device using a material having an abrasive action such as glass beads or alumina. The surface can be made fine and uneven, and the surface area can be increased.

  Hereinafter, embodiments of a fin-and-tube heat exchanger according to the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a schematic configuration diagram of a fin-and-tube heat exchanger according to Embodiment 1 of the present invention, and FIG. 2 is a cross-sectional view of a main part of the fin-and-tube heat exchanger according to the embodiment.

  As shown in FIG. 1, the fin-and-tube heat exchanger 11 includes a large number of fins 12 arranged in parallel at regular intervals, and a U-shape in which a fluid flows inside the fins 12 inserted at right angles. A tube 13 and a return bend 14 for connecting the U-shaped tubes 13 to each other are provided. By expanding the U-shaped tube 13, the U-shaped tube 13 and the fin 12 are brought into close contact with each other. The tube 13 is welded to connect the tip of the tube 13 and the return bend 14 to form a circuit through which fluid flows.

  And the coating-film layer 16 is formed by baking-coating a rust-proof coating material by coating methods, such as a dip coating system or a spray coating system, on this fin and tube type heat exchanger 11 whole surface.

  The coating layer 16 is generally baked and coated with 5 to 25 μm, 1 coat 1 bake or 2 coat 2 bake.

  As shown in FIG. 2, the surface of the return bend 14 has a structure in which a coating layer 16 coated with a rust preventive paint is applied to a portion having a fine unevenness 15.

  As described above, in the present embodiment, the surface of the return bend is finely uneven, and the surface area is increased so that the surface is increased. Even when corrosive substances such as systems and carboxylic acids gradually invade, the adhesion of the coating film is maintained by the effect of increasing the surface area, so there is no occurrence of coating film floating and corrosion is not promoted Therefore, an excellent anticorrosion effect can be exhibited, and the operation as a refrigeration system can be maintained for a long time.

  In addition, by applying the coating on the fins and U-shaped tubes with fine irregularities, the coating adhesion of the fins and U-shaped tubes can be further improved. The anticorrosion effect of the entire exchanger can be enhanced.

  The method of making the surface of the fin, U-shaped tube, and return bend uneven is by etching or chemical conversion reaction of the surface with chemicals, etc., and the surface can be made fine uneven, Can be increased. Examples of chemicals that make the surface uneven are acid chemicals such as sulfuric acid, nitric acid and hydrochloric acid, and alkaline chemicals such as caustic soda because the outermost surface is corroded and scraped off. The chemical conversion treatment includes phosphoric acid film treatment and anodized film for the reason of activating the outermost surface.

  In addition, the method of making the surface of the fin, U-shaped tube, and return bend uneven is made by spraying with an automatic device such as an air blast spray device using a material having an abrasive action such as glass beads or alumina, The surface can be formed into fine irregularities, and the surface area can be increased. In addition, materials such as glass beads and alumina have high safety, good workability, and easy process control. Furthermore, by using an automatic device, the number of workers can be reduced and the cost can be reduced.

  In this embodiment, the surface of the fin, U-shaped tube, and return bend is coated with fine irregularities, but the U-shaped tube and fin-and-tube heat exchanger It goes without saying that the same effect can be obtained even if the same treatment is applied to the surface of the straight pipe used as the entrance / exit pipe.

  As described above, the fin-and-tube heat exchanger of the present invention is placed in a highly corrosive environment by coating the portion of the return bend with a fine uneven surface to increase the surface area. Even when corrosive substances such as sulfur and carboxylic acid gradually infiltrate inside the film layer, coating surface adhesion is maintained by the effect of increasing the surface area, so there is no occurrence of coating film lifting and corrosion is accelerated The anti-corrosion effect which is not performed can be exhibited, and since it can maintain a long-term operation as a refrigeration system, it can be applied as a fin-and-tube heat exchanger for a refrigerator and a showcase.

1 is a schematic configuration diagram of a fin-and-tube heat exchanger according to Embodiment 1 of the present invention. Sectional drawing of the principal part of the fin and tube type heat exchanger of the embodiment Schematic configuration diagram of a conventional fin-and-tube heat exchanger Sectional view of the main part of a conventional fin-and-tube heat exchanger

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Fin and tube type heat exchanger 12 Fin 13 U-shaped tube 14 Return bend 15 Fine uneven surface 16 Coating layer

Claims (5)

  A large number of fins arranged in parallel at regular intervals; a U-shaped tube through which fluid flows through an interior inserted perpendicular to the fins; and a return bend connecting the U-shaped tubes; A fin-and-tube heat exchanger characterized in that a coating is applied to a portion where the surface of the return bend is processed into fine irregularities.   2. The fin-and-tube heat exchanger according to claim 1, wherein the fins and the U-shaped tube are coated at portions where the surface of the U-shaped tube is processed into fine irregularities.   A large number of fins arranged in parallel at regular intervals; a U-shaped tube through which fluid flows through an interior inserted perpendicular to the fins; and a return bend connecting the U-shaped tubes; A method of manufacturing a fin-and-tube heat exchanger in which the surface of the return bend is processed into fine irregularities before coating the surface of the return bend.   4. The method for manufacturing a fin-and-tube heat exchanger according to claim 3, wherein the method of processing the surface of the return bend into a concavo-convex shape is performed by etching or chemical conversion reaction of the surface with a chemical or the like.   4. The fin according to claim 3, wherein the method of processing the surface of the return bend into a concavo-convex shape is performed by an automatic device such as an air blast injection device using a material having a polishing action such as glass beads or alumina. Manufacturing method of an and tube type heat exchanger.

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