JP2006125659A - Fin and tube type heat exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To exercise superior adhesiveness and anticorrosive effect even under severe high corrosive environment with respect to the coating of a fin and tube type heat exchanger used in a refrigerator and the like. <P>SOLUTION: This fin and tube type heat exchanger comprises a number of fins 12 arranged in parallel at constant intervals, U-shaped tubes 13 which are inserted into the fins 12 at a right angle and in which fluid flows, and return bends 14 connecting the U-shaped tubes 13 with each other. As surfaces of the fins 12, U-shaped tubes 13 and return bends 14 are coated with urethane modification epoxy resin as a thermosetting resin, superior anticorrosive effect can be exercised as the adhesiveness with a basis material is improved by the effect of an OH group (hydroxyl group) in the coating by urethane bond, while keeping water permeability-proof property of the coating as original properties of the epoxy resin, even when the heat exchanger is placed under severe high corrosive environment, and corrosive substances such as sulfur and carboxylic acid gradually intrude inside of a coating layer, thus the heat exchanger can be operated 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 perspective view of a main part of the conventional fin-and-tube heat exchanger.

  As shown in FIGS. 3 and 4, the conventional fin-and-tube heat exchanger 1 has a large number of fins 2 arranged in parallel at regular intervals and a fluid flowing 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. Further, welding is performed to connect the tip of the U-shaped tube 3 and the return bend 4 to form a circuit through which fluid flows. The fin 2, the U-shaped tube 3, and the return bend 4 constituting the conventional fin-and-tube heat exchanger 1 are provided with a resin layer 5 coated with a thermosetting resin.

After the fin-and-tube heat exchanger 1 is assembled, a rust preventive paint, which is a thermosetting resin, is baked and applied on the entire surface of the heat exchanger 1 by a coating method such as a dip coating method or a spray coating method. Form. The film thickness of the resin layer 5 is 5 to 25 μm, and the baking coating is performed by 1 coat 1 bake or 2 coat 2 bake. In addition, as a rust preventive paint that is a thermosetting resin, a paint of polyester resin, alkyd resin, acrylic resin, or epoxy resin is used.
JP 2003-139485 A

  However, coating of alkyd resin, acrylic resin, and polyester resin has an anticorrosive effect in a general environment, but in a highly corrosive environment such as sulfur-based or carboxylic acid, the cross-linked portion between cross-linked resin monomers is hydrolyzed and destroyed. There is a problem in that condensed water containing corrosive substances is absorbed and the anticorrosion effect is remarkably lowered.

  On the other hand, epoxy resin coating has higher water-resistant permeability than alkyd resin, acrylic resin, and polyester resin coating, so the cross-linked part of crosslinked resin monomers is hydrolyzed even in highly corrosive environment such as sulfur and carboxylic acid. Although the anticorrosion effect is relatively maintained since it is difficult to do, the adhesion is lowered with the passage of time, and there is a problem that the anticorrosion effect is lowered. When the glass transition point of the epoxy resin is increased and the coating film is hardened, the water permeability is increased, but on the other hand, it becomes brittle and the adhesion is lowered. When it is down, there is a problem that sufficient anti-corrosion effect cannot be obtained even with epoxy resin coating.

  In recent years, the problem of sick house due to formaldehyde has become a social problem, and paints are also required to be environmentally friendly. Many thermosetting rust preventive paints such as polyester resin, alkyd resin, acrylic resin, and epoxy resin use melamine resin or phenol resin as a curing agent, and because this resin contains formaldehyde, there is a problem of work safety. There has been a demand for further measures for the environment, such as exhaust problems in baking ovens and baking, and VOC (organic volatile compound) regulations.

  The present invention solves the above-mentioned conventional problems, and since it does not use melamine resin or phenol resin as a curing agent for the paint, it does not contain formaldehyde, is a paint that is environmentally friendly and is placed in a severe and highly corrosive environment. An object of the present invention is to provide a fin-and-tube heat exchanger capable of exhibiting an excellent anticorrosion effect by maintaining and improving the adhesion while maintaining the water-resistant permeability of the coating film even in the case where it is applied.

  In order to solve the above-described conventional problems, the fin-and-tube heat exchanger of the present invention is obtained by applying a urethane-modified epoxy resin to a thermosetting resin to be coated on the surfaces of fins and tubes.

  As a result, by modifying the epoxy resin using urethane bonds, the coating film has more OH groups (hydroxyl groups) and can improve adhesion to the substrate, so it was placed in a severely corrosive environment. Even in this case, it is possible to maintain and improve the adhesion while maintaining the water permeability of the coating film.

  The fin-and-tube heat exchanger of the present invention is a urethane-modified epoxy resin coated on the surface of fins and tubes, and is placed in a severe and highly corrosive environment. Even if corrosive substances such as sulfur and carboxylic acid gradually invade into the resin, the effect of OH groups (hydroxyl groups) in the paint film due to urethane bonds is maintained while maintaining the water resistance of the paint film inherent to the epoxy resin. Since the adhesion to the substrate can be improved, an excellent anticorrosion effect can be exhibited, and the operation as a refrigeration system can be maintained for a long period of time.

  The invention according to claim 1 is composed of a large number of fins arranged in parallel at regular intervals, and a tube through which a fluid flows inside the fin inserted at right angles to the fins, and the fin and the surface of the tube In a heat exchanger coated with a thermosetting resin, the thermosetting resin is a urethane-modified epoxy resin, and even when placed in a severe and highly corrosive environment, the water resistance of the original coating film of the epoxy resin Since the adhesion to the substrate can be improved by the effect of the OH group (hydroxyl group) in the coating film due to the urethane bond while maintaining the permeability, an excellent anticorrosive effect can be exhibited.

  The invention according to claim 2 is the invention according to claim 1, wherein the urethane-modified epoxy resin has an epoxy resin average molecular weight of 5000 to 15000, and the coating film is obtained by polymerizing the epoxy resin average molecular weight. The water permeation resistance can be increased. When the average molecular weight of the epoxy resin exceeds 15000, the viscosity of the coating becomes high, and only a strong solvent can be made into a coating, which makes it unsuitable as a coating for immersion. When the average molecular weight of the epoxy resin is less than 5000, the water permeability of the coating film becomes low, and the anticorrosion effect cannot be exhibited in a severe and highly corrosive environment.

  Invention of Claim 3 made the glass transition point of the coating film of the said urethane modified epoxy resin 80-120 degree | times in the invention of Claim 1, and made the glass transition point of the coating film high. As a result, the coating film becomes hard, and it becomes difficult for water containing corrosive substances such as sulfur and carboxylic acid to penetrate into the coating film layer, thereby improving water permeability. When the glass transition point exceeds 120 degrees, the coating film becomes very hard, but on the other hand, it is brittle and the adhesiveness is lowered, and the balance between water permeation resistance and adhesiveness is lost. When the glass transition point is less than 80 degrees, water containing a corrosive substance such as sulfur or carboxylic acid easily enters the coating layer, resulting in low water permeability.

  Invention of Claim 4 adds the antirust pigment to the said urethane modified epoxy resin in invention of Claim 1, and contains corrosive substances, such as sulfur type and carboxylic acid, in the coating-film layer inside. When water enters, it dissolves in the water, delays the progress of corrosion, and has the effect of protecting the fins and tubes by reaction with the pigment component, preventing corrosion of the fins and tubes, and further exhibiting an anticorrosive effect be able to.

  The invention according to claim 5 is the invention according to claim 4, wherein the rust preventive pigment uses zinc dust, and is generated while protecting fins and tubes by galvanic action (sacrificial anodic action) of zinc dust. The corrosion product has the effect of greatly delaying the progress of corrosion, and further anticorrosion effect can be expected.

  The invention according to claim 6 is the invention according to claim 5, wherein the added amount of the zinc powder is 5 to 20% by weight ratio of the solid content of the coating film, and the effect of the galvanic action of the zinc powder is reduced. While exhibiting, the anti-corrosion effect can be exhibited while maintaining the water-resistant permeability and adhesion of the urethane-modified epoxy resin. If the added amount of zinc powder exceeds 20%, the water-resistant permeability and adhesion of the urethane-modified epoxy resin cannot be maintained, and the anticorrosive effect cannot be exhibited. If the amount of zinc powder added is less than 5%, the effect of galvanic action of zinc powder cannot be sufficiently exhibited.

  Hereinafter, embodiments of the 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 perspective view of a main part of the fin-and-tube heat exchanger according to the embodiment.

  As shown in FIGS. 1 and 2, the fin-and-tube heat exchanger 11 includes a large number of fins 12 arranged in parallel at regular intervals, and a U flow through which fluid flows through the inside inserted at right angles to the fins 12. A U-shaped tube 13 and a return bend 14 for connecting the U-shaped tubes 13 to each other; by expanding the U-shaped tube 13, the U-shaped tube 13 and the fin 12 are brought into close contact with each other; Further, welding is performed to connect the distal end of the U-shaped tube 13 and the return bend 14 to form a circuit through which the fluid flows. The fin and tube heat exchanger 11 has a structure in which a fin 12, a U-shaped tube 13, and a return bend 14 are coated with a resin layer 15 coated with a thermosetting resin.

  After the fin-and-tube heat exchanger 11 is assembled, the entire surface of the heat exchanger 11 is baked with a rust preventive paint, which is a thermosetting resin, by a coating method such as a dip coating method or a spray coating method, and the resin layer 15 is coated. Form. The film thickness of the resin layer 15 is 5 to 25 μm, and the baking coating is performed by 1 coat 1 bake or 2 coat 2 bake. A rust-proof paint, which is a thermosetting resin, is a urethane-modified epoxy resin paint, and the painted resin layer 15 is coated with a urethane-modified epoxy resin.

  As described above, in the present embodiment, the thermosetting resin to be applied to the surfaces of the fins and tubes is made of urethane-modified epoxy resin, so that it is placed in a severe and highly corrosive environment, and the inside of the coating layer Even if corrosive substances such as sulfur and carboxylic acid gradually invade into the resin, the effect of OH groups (hydroxyl groups) in the paint film due to urethane bonds is maintained while maintaining the water resistance of the paint film inherent to the epoxy resin. Since the adhesion to the substrate can be improved, an excellent anticorrosion effect can be exhibited, and the operation as a refrigeration system can be maintained for a long period of time.

  When the urethane-modified epoxy resin has an average epoxy resin molecular weight of 5000 to 15000 and the resin is polymerized, the water permeability of the coating film is increased and the basic anticorrosive effect is enhanced. When the average molecular weight of the epoxy resin exceeds 15,000, the viscosity of the coating becomes very high, the fluidity is lost, and it becomes impossible to make a coating for immersion. If the average molecular weight of the epoxy resin is less than 5,000, the water permeability of the coating film becomes low, and the anticorrosion effect cannot be exhibited in a severe and highly corrosive environment (the average molecular weight of the conventional epoxy resin is about 500 to 3000, In such an environment, the water permeability of the coating film was not sufficient).

  In addition, by increasing the glass transition point of the coating film of urethane-modified epoxy resin to 80 to 120 degrees and increasing the glass transition point of the coating film, the coating film becomes hard, such as sulfur-based or carboxylic acid inside the coating film layer Water containing a corrosive substance is difficult to enter, and water permeability is increased, and the anticorrosion effect is further enhanced. When the coating film becomes hard, the adhesiveness decreases, but the adhesiveness can be greatly improved by the action of the urethane bond, so that the adhesiveness can be improved together with the curing of the coating film. When the glass transition point exceeds 120 degrees, the coating becomes very hard, but on the other hand, it is fragile and the adhesion is extremely lowered, and the effect of improving the adhesion of urethane bonds is not seen, and the balance between water permeability and adhesion is lost. . When the glass transition point is less than 80 degrees, water containing a corrosive substance such as sulfur or carboxylic acid easily enters the coating layer, resulting in low water permeability.

  In addition, by adding anti-corrosive pigments to urethane-modified epoxy resins, if water containing corrosive substances such as sulfur and carboxylic acid infiltrates inside the coating layer, it dissolves in the water and delays the progress of corrosion. The fin and the tube are protected by the reaction with the pigment component, the corrosion of the fin and the tube can be prevented, and the anticorrosive effect can be exhibited.

  By using zinc dust, this rust preventive pigment protects the fins and tubes by the galvanic action (sacrificial anodic action) of the zinc dust, and has the effect of greatly delaying the corrosion progression due to the generated corrosion products. Can be expected.

  The amount of zinc powder added is 5 to 20% by weight ratio of the solid content of the coating, thereby maintaining the water permeability and adhesion of the urethane-modified epoxy resin while demonstrating the galvanic effect of the zinc powder. The anticorrosion effect can be exhibited as it is. If the added amount of zinc powder exceeds 20%, the water-resistant permeability and adhesion of the urethane-modified epoxy resin cannot be maintained, and the anticorrosive effect cannot be exhibited. If the amount of zinc powder added is less than 5%, the effect of galvanic action of zinc powder cannot be sufficiently exhibited.

  This urethane-modified epoxy resin does not use melamine resin or phenol resin that contains formaldehyde as a curing agent for paints, so it can ensure the safety of painters, and there is no formaldehyde contained in the exhaust of the baking and drying furnace. There is no worry that the sick house problem that is a social problem will occur. The paint is also environmentally friendly.

  Even when the embodiments are used in combination, the same effect as the above embodiments can be expected.

  As described above, the fin-and-tube heat exchanger of the present invention is placed in a severe and highly corrosive environment by applying urethane-modified epoxy resin to the thermosetting resin to be applied to the surfaces of the fins and tubes. Even when corrosive substances such as sulfur and carboxylic acid gradually infiltrate into the coating layer, the OH groups in the coating due to urethane bonds ( Adhesion with the substrate can be improved by the effect of the hydroxyl group), so that an excellent anticorrosion effect can be exhibited, and the operation as a refrigeration system can be maintained for a long time.

  Therefore, it can be applied as a fin-and-tube heat exchanger for a refrigerator-freezer or a showcase.

Schematic configuration diagram of a fin-and-tube heat exchanger in Embodiment 1 of the present invention The principal part perspective view of the fin and tube type heat exchanger of the embodiment Schematic configuration diagram of a conventional fin-and-tube heat exchanger Main part perspective view 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 Resin layer (coating film)

Claims (6)

  The heat is composed of a large number of fins arranged in parallel at regular intervals, and a tube through which fluid flows through the inside inserted at right angles to the fins, and the surface of the fin and the tube is coated with a thermosetting resin. The exchanger is a fin-and-tube heat exchanger in which the thermosetting resin is a urethane-modified epoxy resin.   The fin-and-tube heat exchanger according to claim 1, wherein the urethane-modified epoxy resin has an average epoxy resin molecular weight of 5000 to 15000.   The fin-and-tube heat exchanger according to claim 1, wherein a glass transition point of the urethane-modified epoxy resin coating film is 80 to 120 degrees.   The fin-and-tube heat exchanger according to claim 1, wherein a rust preventive pigment is added to the urethane-modified epoxy resin.   The fin-and-tube heat exchanger according to claim 4, wherein the antirust pigment uses zinc dust.   The fin-and-tube heat exchanger according to claim 5, wherein the amount of zinc powder added is 5 to 20% in terms of the solid content weight ratio of the coating film.

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