JP2019157013A - Carbon fiber-containing paint, and heat exchanger coated therewith - Google Patents

Abstract

To provide: a carbon fiber-containing paint that can improve the heat conductivity efficiency even in the configuration of existing heat exchangers made of metal, etc.; and a heat exchanger coated with the carbon fiber-containing paint.SOLUTION: Provided is a carbon fiber-containing paint that is applied on metal parts such as tubes 3 and fins 4 of a heat exchanger 1, and in which, to a matrix resin obtained by adding a dispersant to a varnish-based resin, pulverized carbon fibers are mixed. As the carbon fiber, carbon fibers coarsely pulverized to have an average fiber length of 10 to 100 μm and an average fiber diameter of 5 to 15 μm, and carbon fibers finely pulverized to have an average fiber length of 0.5 to 5 μm and an average fiber diameter of 0.3 to 1 μm are contained in a proportion of weight ratio 20:80 to 10:90.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a carbon fiber-containing paint applied to a heat exchanger, and a heat exchanger applied with the carbon fiber-containing paint, and more specifically, to protect tubes and fins made of metal. The present invention relates to a carbon fiber-containing paint that is improved in thermal conductivity.

  Generally, a heat exchanger is configured to include a tube through which a fluid to be heat exchanged passes and a plurality of fins provided so as to cross the tube. A fluid to be heated is passed through the tube, and heat is exchanged between the fluid and the fluid flowing outside the fin.

  Such a heat exchanger is used in a wide variety of fields. For example, when water is heated using exhaust gas from a boiler using heavy oil, the following problems arise.

  That is, when water is heated by burning heavy oil containing sulfur, it is generally said that the heat exchange efficiency increases by 1% each time the temperature of the exhaust gas decreases by 10 ° C. However, when the exhaust gas temperature is 120 ° C. or lower, sulfur contained in the exhaust gas is extracted on the surfaces of the tubes and fins and becomes sulfuric acid to corrode the tubes and fins. For this reason, conventionally, the temperature of the exhaust gas is raised to 200 ° C. However, if this is done, not only will the sulfur content be released into the atmosphere, causing acid rain, but also the heat exchange efficiency. Will also fall.

  In contrast, the fins are made of matrix resin. A heat exchanger in which carbon fiber is contained therein has also been proposed.

  For example, Patent Document 1 below proposes a heat exchanger using a resin in which carbon fibers are arranged in a direction orthogonal to the longitudinal direction of the tube. In such a heat exchanger, the metal is not corroded by sulfur, and heat can be transferred to the fins by the carbon fiber in the direction perpendicular to the tube. Therefore, carbon fiber with high thermal conductivity instead of metal Can be used for heat exchange.

JP 2017-219214 A

  However, in such a configuration, it is necessary to mold a resin having carbon fibers arranged in a grid in advance, which not only increases the manufacturing cost, but also in the gaps between the grid-like carbon fibers. Cannot be transmitted. Moreover, such a configuration cannot be adopted later in existing heat exchangers. Furthermore, since the boundary portion between the tube and the fin is bent, it becomes difficult to bend the carbon fiber along such a situation, and a gap is formed, resulting in a decrease in thermal conductivity.

  Therefore, the present invention was made paying attention to the above problems, and in the configuration of an existing heat exchanger made of metal or the like, a carbon fiber-containing paint that can improve the thermal conductivity efficiency, And it aims at providing the heat exchanger which apply | coated this carbon fiber containing coating material.

  That is, in order to solve the above problems, the present invention is configured by providing a pulverized carbon fiber powder and a matrix resin containing the carbon fiber powder in a carbon fiber-containing coating applied to a heat exchanger. It is a thing.

  If constituted in this way, it is possible to attach the pulverized carbon fiber powder just by applying such paint to an existing metal heat exchanger, and heat exchange by transferring heat of tubes and fins. To be able to. In addition, since fins and the like can be coated with a paint, the metal is not corroded even if the sulfur content is adhered, and the need for maintenance can be reduced. Thereby, the temperature of exhaust gas can be lowered and the heat exchange efficiency can be improved.

  Furthermore, in such an invention, the carbon fiber powder is composed of carbon fibers having a fiber length of 100 μm or less.

  If it does in this way, it will become possible to make carbon fiber stick to the junction part of a tube and fin of a heat exchanger, etc., and it will become possible to raise thermal conductivity with each part and carbon fiber.

  Further, carbon fibers having an average fiber length of 5 to 100 μm and an average fiber length of 0.5 to 5 μm are blended.

  In this way, the contact area between the carbon fibers can be increased to improve the thermal conductivity, and the aggregation of the carbon fiber powder at the time of firing can be suppressed. Can be prevented.

  Moreover, carbon fiber powder is mix | blended in the ratio of 5-35 weight part.

  If it does in this way, while being able to improve the contact property of a tube or a fin, and carbon fiber, it will become possible to carry out heat exchange between the carbon fiber and the carbon fiber exposed to the coating-film surface. Further, if the carbon fiber content is excessively increased, cracks will occur in the coating film, but in this ratio, cracks will not occur. In addition, if the carbon fiber content is too small, the heat exchange efficiency decreases. However, with such a content, the heat exchange efficiency can be improved.

  According to the present invention, the carbon fiber-containing coating applied to the heat exchanger is provided with the pulverized carbon fiber powder and the matrix resin containing the carbon fiber powder. By simply applying such a paint to the exchanger, the pulverized carbon fiber powder can be adhered, and the heat of the tubes and fins can be transmitted to exchange heat. In addition, since fins and the like can be coated with a paint, the metal is not corroded even if the sulfur content is adhered, and the need for maintenance can be reduced. Thereby, the temperature of exhaust gas can be lowered and the heat exchange efficiency can be improved.

Heat exchanger to which carbon fiber-containing paint is applied in one embodiment of the present invention

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  The heat exchanger 1 to which the carbon fiber matrix resin of this embodiment is applied is configured to heat water using waste heat from the boiler. As shown in FIG. A heat exchange chamber 2 into which exhaust gas is put, a tube 3 provided so as to meander in the heat exchange chamber 2, and a plurality of parallel fins 4 arranged so as to be orthogonal to the tube 3 are provided. Composed. Then, cold water is passed through the tube 3, high-temperature exhaust gas is allowed to flow into the heat exchange chamber 2, and heat is exchanged with water in the tube 3 through the fins 4 to heat the water. And, characteristically, this heat exchanger 1 is coated with a matrix resin containing pulverized carbon fibers, thereby preventing metal corrosion due to sulfur and improving heat exchange efficiency. Is. Hereinafter, an embodiment of the present invention will be described in detail.

  First, the outline of the heat exchanger 1 to which the carbon fiber-containing paint is applied will be briefly described.

  First, in the heat exchange chamber 2 constituting the heat exchanger 1, a fluid such as high-temperature exhaust gas is passed, and as shown in FIG. 1, the inlet 21 is on one side and the outlet 22 is on the other side. Is provided. Then, the high-temperature first fluid that has flowed into the charging port 21 is passed through the fin gap and discharged from the discharge port 22. In FIG. 1, the inlet 21 is provided in a direction (normal direction) perpendicular to the fin 4, but the first fluid is put in a direction parallel to the fin 4 and the exhaust gas is passed through the gap of the fin 4. You may make it easy.

  On the other hand, the tube 3 is provided so as to meander to the left and right, and allows the second fluid to be heat exchanged to pass therethrough. Here, cold water is used as the second fluid, and this cold water is heated and discharged as hot water. Although the tube 3 is meandered here, headers (not shown) for meandering the second fluid in the tube 3 are provided at the left and right ends, and the linear tube 3 is connected to the headers to meander. It may be.

  Further, the fin 4 provided so as to cross the tube 3 is configured to exchange heat between the second fluid in the tube 3 and the first fluid in the heat exchange chamber 2, and is welded to the tube 3. Provided. Then, heat is absorbed by the fins 4 through the first fluid which is exhaust gas in the gap, and the heat is transmitted to the second fluid in the tube 3.

  In such a configuration, when the exhaust gas obtained by burning heavy oil is used as the first fluid, sulfur contained in the heavy oil adheres to the inner wall of the heat exchange chamber, the tubes 3, the fins 4, etc., and the metal It reacts with and corrodes. In addition, conventionally, a method of opening a gap between the fin 4 and the fin 4 in order to dissolve the adhered dirt with a solution and periodically remove it has been adopted. In addition, it was necessary to use expensive metals such as titanium and SUS316L in order to prevent corrosion. Therefore, in this embodiment, in a conventional metal heat exchanger, by applying a matrix resin containing carbon fiber, the metal surface is coated with a coating to prevent corrosion, and the conventional Thus, the dirt is not removed by dissolving it with a solution, but the dirt can be easily removed.

  Such a carbon fiber-containing paint is configured to contain carbon fibers and a matrix resin.

  When such a carbon fiber is used, if the fiber length of the carbon fiber is too long, the carbon fiber is moved along the connecting portion of the tube 3 and the fin 4, the bent portion or the outer peripheral portion of the tube 3, the end of the fin 4, and the like. It cannot be attached well. Further, if the fiber length is too short, not only the connection with each carbon fiber is reduced, but also aggregation occurs when mixed in the matrix resin. For this reason, it is preferable to pulverize the carbon fiber within an average fiber length of 100 μm or less so that the carbon fiber is in close contact with the end of the fin 4 or the bent portion of the tube 3. At this time, the coarsely pulverized carbon fiber has an average fiber length of 5 to 100 μm and an average fiber diameter of 5 to 15 μm. Moreover, with such coarsely pulverized carbon fibers alone, the contact area between the carbon fibers becomes small, resulting in poor heat conduction efficiency. Therefore, in the present embodiment, carbon fibers having a fiber length of 5 μm or less (preferably, an average fiber length of 0.5 to 5 μm) and an average fiber diameter of 0.3 to 1 μm are contained as finely pulverized carbon fibers. . By including such fine carbon fibers, it is possible to prevent aggregation of carbon fibers in the matrix resin, and also prevent re-aggregation, generation of pinholes, and peeling during matrix resin firing. Will be able to. The ratio of the coarsely pulverized carbon fiber to the finely pulverized carbon fiber is set in the range of 20:80 to 10:90 by weight.

  As such carbon fibers, new or recycled carbon fibers can be used, and the types of carbon fibers may be PAN or pitch. When such carbon fiber is pulverized into particles, it can be pulverized using a known method. For example, airflow pulverization, a ball mill, a crusher mill, or the like can be used.

  On the other hand, the matrix resin contains carbon fiber and is attached to a metal such as the tube 3 or the fin 4. Here, the varnish resin, the silicon resin, the acrylic resin, the vinyl acetate resin is used. Resin etc. can be used and what was copolymerized as needed can also be used. Here, a polyimide varnish is used, and one diluted with a solvent pororidone is used. Since this varnish resin is a polyamic acid solution that is a polyimide precursor, it is applied to the surface of the heat exchanger 1 and baked at a high temperature, whereby the solvent is removed and the imidization reaction proceeds. Thus, a polyimide coating film having excellent insolubility, heat resistance, body chemical properties, and electrical insulation is obtained. Then, a dispersant is appropriately added to the matrix resin so that the carbon fibers are dispersed in the solution.

  The operation when this varnish matrix resin is used will be described.

  When molding a polyimide coating, the coating is formed on the metal surface by imidizing (ring-closing) the polyamic acid contained in the varnish resin. In general, a diamine component or a tetracarboxylic dianhydride component is used. However, this diamine component or tetracarboxylic dianhydride component is greatly affected by the carbon fiber dispersant, and in particular, pyrrolidone when imidizing a varnish resin at the initial firing at 100 to 120 ° C. The residual content of the solvent, such as, decreases to around 10 ppm, and when it exceeds 180 ° C., the vaporization of the aqueous dispersant used to disperse the carbon fiber powder begins, and the carbon particles that have lost steric hindrance have melted. Re-aggregation occurs in the matrix resin that is thermoset from the state, and the airway in the matrix resin is widened to become a foamed state. Therefore, it is impossible to disperse into the above situation by molding a polyimide resin with a dispersant having a small number of lipophilic groups that have been used to disperse carbon fibers and having a large number of hydrophilic groups that easily adsorb on the surface of carbon particles. It becomes. For this reason, a phosphate-based dispersant having no adsorption suitable for nonpolar surfaces is used, and 1 to 3 parts by weight of this is mixed with the total amount. As a result, carbon fiber re-aggregation due to vaporization and movement of water molecules is reduced from 200 ° C. to high temperature decomposition, and pinholes can be prevented from being generated.

  When carbon fiber is contained in such a matrix resin, if the ratio of the carbon fiber is small, the carbon fiber is not continuous between the tube 3 or the fin 4 and the outside of the coating film, and heat exchange cannot be performed. On the other hand, if the proportion of carbon fibers is too large, cracks and separation between metals will occur. For this reason, carbon fiber is preferably blended in a proportion of 5 to 35 parts by weight, and preferably in the range of 10 to 20 parts by weight in consideration of prevention of peeling and cracking after curing of the coating film.

  When the carbon fiber-containing paint blended in this way is applied to the heat exchanger 1, various methods can be used. For example, a coating method for fitting to a varnish with thixotropy, a spray coating method using an air cup A coating method using a defoaming roller, a dipping coating method, a brush coating, or the like can be used. At this time, if a dipping coating method is used, a coating film can be uniformly formed, the exposed portion of the metal is eliminated, and the carbon fiber is continuously contacted between the metal and the coating film surface with a uniform thickness. Heat exchange can be performed.

  In such a configuration, first, when producing a carbon fiber-containing coating, PAN-based or pitch-based carbon fibers are coarsely pulverized to produce chipped fibers, and the chipped fibers are put into an airflow pulverizer or the like. And crude carbon fiber powder with an average fiber length of 5-100 micrometers and an average fiber diameter of 5-15 micrometers is produced | generated. And while taking out the crude carbon fiber powder, a part of the carbon fiber powder is put into the grinder again, and this time, fine carbon having an average fiber length of 0.5 to 5 μm and an average fiber diameter of 0.3 to 1 μm as fine grinding. A fiber powder is produced, and the coarsely pulverized carbon fiber powder and the finely pulverized carbon fiber powder are mixed at a weight ratio of 20:80 to 10:90.

  On the other hand, in order to produce a matrix resin together with this, a dispersant is added to the varnish resin, and the mixed carbon fiber powder is added at a ratio of 5 to 35 parts by weight and mixed.

  At this time, if the input carbon fiber powder is only finely pulverized carbon fiber powder, agglomeration occurs, but by mixing coarsely pulverized carbon fiber and finely pulverized carbon fiber, Aggregation can be prevented and the contact area between the carbon fibers can be increased to ensure thermal conductivity. Then, the matrix resin charged with carbon fibers is stirred as described above to disperse the carbon fibers in the solution.

  Next, the matrix resin thus generated is applied to the tubes 3 and fins 4 of the heat exchanger 1. In this application process, when applying to the existing heat exchanger 1, it is difficult to apply between the fins 4 and 4, so that a matrix resin is put in the bathtub, and the heat exchanger 1 is placed there. Dipping. Then, after the heat exchanger 1 is taken out and dried, heat treatment is performed in the baking chamber.

  In this heat treatment step, the solvent is removed at a high temperature and the imidization reaction proceeds to produce a polyimide coating film excellent in insolubility and infusibility, heat resistance, chemical resistance and the like. In addition, by using a fatty acid-based dispersant that does not contain phosphate as a dispersant, carbon fiber re-aggregation due to vaporization and movement of water molecules is reduced even during high-temperature heating, preventing the occurrence of pinholes, etc. can do.

  Thus, according to the above embodiment, in the carbon fiber-containing coating applied to the heat exchanger 1, the pulverized carbon fiber powder and the matrix resin containing the carbon fiber powder are provided. By simply applying such a paint to the existing metal heat exchanger 1, the pulverized carbon fiber powder can be adhered, and the heat of the tubes 3 and fins 4 can be transferred to exchange heat. It becomes like this. In addition, since the fins 4 and the like can be coated with a paint, the metal is not corroded even if the sulfur content is attached, and the need for maintenance can be reduced. Thereby, the temperature of exhaust gas can be lowered and the heat exchange efficiency can be improved.

  In addition, since the carbon fiber powder is composed of carbon fibers having an average fiber length of 100 μm or less, the carbon fibers can be brought into close contact with the joint portion between the tube 3 and the fin 4 of the heat exchanger 1. Thus, the adhesion of the carbon fibers in each part can be improved.

  Furthermore, since carbon fibers having an average fiber length of 5 to 100 μm and an average fiber length of 0.5 to 5 μm are blended, the contact area between the carbon fibers can be increased to improve the thermal conductivity, Aggregation of fibers can be suppressed during firing, and obstacles such as pinholes and peeling can be prevented.

  Moreover, since the carbon fiber powder was blended at a ratio of 5 to 35 parts by weight, the contact between the tube 3 and the fin 4 and the carbon fiber can be improved, and the carbon fiber and the coating film surface were exposed. Heat exchange can be performed with the carbon fiber. Further, if the carbon fiber content is excessively increased, cracks will occur in the coating film, but in this ratio, cracks will not occur. In addition, if the carbon fiber content is too small, the heat exchange efficiency decreases. However, with such a content, the heat exchange efficiency can be improved.

  In addition, this invention can be implemented in various aspects, without being limited to the said embodiment.

  For example, in the above embodiment, carbon fiber powder having an average fiber length of 100 μm or less is used. However, depending on the size of the heat exchanger 1, carbon fiber powder having a larger average fiber length may be used. Also good. That is, the average fiber length, the average fiber diameter, and the like may be changed according to the size of the heat exchanger 1 and the complexity of the structure.

  Moreover, in the said embodiment, although the coating film containing carbon fiber powder was produced | generated in the heat exchanger 1, resin may be lose | eliminated by use and a coating film may become thin. Even in such a case, only the carbon fibers remain, but it is also possible to ensure thermal conductivity by forming a coating film in a similar manner from above.

DESCRIPTION OF SYMBOLS 1 ... Heat exchanger 2 ... Exchange chamber 21 ... Input port 22 ... Discharge port 3 ... Tube 4 ... Fin

Claims (5)

In the carbon fiber-containing paint applied to the heat exchanger,
Pulverized carbon fiber powder,
A matrix resin containing the carbon fiber powder;
A carbon fiber-containing paint characterized by comprising: The carbon fiber-containing paint according to claim 1, wherein the carbon fiber powder is composed of carbon fibers having an average fiber length of 100 µm or less. The carbon fiber-containing paint according to claim 1, wherein the carbon fiber powder is obtained by blending carbon fiber powder having an average fiber length of 5 to 100 µm and carbon fiber powder having an average fiber length of 0.5 to 5 µm. The carbon fiber-containing paint according to claim 1, wherein the carbon fiber powder is blended at a ratio of 5 to 35 parts by weight. The heat exchanger which apply | coated the carbon fiber containing coating material of Claims 1 thru | or 4.

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