KR20190084744A - A metal tube with enamel layer - Google Patents

Abstract

The present invention relates to a metal tube for a heat exchanger in which an electrothermal pin is formed on a surface and, more specifically, relates to a metal tube in which a thickness of an enamel layer is 250 ± 100 μm, wherein a length of the metal tube is more than or equal to 5 m, and the enamel layer is formed on a surface of the metal tube.

Description

A metal tube with enamel layer < RTI ID = 0.0 >

The present invention relates to a metal tube for a heat exchanger having a heat transfer fin, the metal tube having an enamel layer on its surface.

Japanese Patent No. 10-1474277, No. 10-1474278 and No. 10-1074438 disclose the applicants' prior patents relating to enamel coating method and enamel coating apparatus of a metal tube for a heat exchanger in which heat transfer fins are formed.

However, in general, a metal tube used as a generator heat exchanger is used in a harsh environment. Therefore, in order to prevent corrosion and maintain durability, it is necessary that the thickness of the coated enamel layer of the metal tube is sufficiently large.

However, according to the conventional enamel coating method, there is a problem that the enamel layer can not be formed to a sufficient thickness on the surface of the metal tube. When the metal tube having the heat conductive fins formed on the surface thereof is coated with enamel, the heat conductive fin ends of the metal tube before being completely fired after application of the enamel glaze come into contact with the rollers supporting the heat conductive fins, There is a problem in that the enamel coating of the coating layer is damaged.

Therefore, it is necessary to provide a method for providing a metal tube for a heat exchanger in which an enamel layer of a heat transfer fin is not damaged and an enamel layer of a predetermined thickness is formed.

Korean Patent No. 10-1474277 Korean Patent No. 10-1474278 Korean Patent No. 10-1074438

According to the present invention,

It is an object of the present invention to provide a metal tube for a heat exchanger in which a heat conductive fin is formed on a surface of the metal tube.

According to the present invention,

Wherein a length of the metal tube is 5 m, 10 m or 15 m or more, an enamel layer formed on the surface of the metal tube is formed, and the thickness of the enamel layer is 250 ± 100 μm And a metal tube. The maximum length of the metal tube is 30m or 40m or less.

The present invention can also provide a metal tube having improved durability by forming the thickness of the enamel layer in a predetermined range.

The metal tube for a heat exchanger of the present invention differs from a conventional metal tube in that a coating film of a sufficient thickness is not formed due to the damage of the enamel coating on the heat transfer fin end side of the metal tube in the firing process, It is possible to provide an enamel coated metal tube having excellent quality.

1 is a photograph of a metal tube on which an enamel layer according to the present invention is formed.
2 is a photograph of a metal tube on which an enamel layer is formed according to a conventional enamel coating method.
FIG. 3 is a simplified view of the coating section of the enamel coating apparatus used in the production of the metal tube with the enamel layer of the present invention.
FIG. 4 is an illustration of an enamel glaze part of an enamel coating apparatus used for manufacturing a metal tube with an enamel layer according to the present invention.
5 illustrates an enamel glaze spray nozzle and a recipient of an enamel coating apparatus used for manufacturing a metal tube having an enamel layer according to the present invention.
6 schematically shows an enamel coating apparatus employing an elongated roller used for manufacturing a metal tube having an enamel layer according to the present invention.
7 shows the coating chamber conveyor 400, the firing chamber conveyor 500, the additional coating chamber conveyor 600 and the re-firing chamber conveyor 700 of the enamel coating apparatus used for manufacturing the enamel layer-formed metal tube according to the present invention. As shown in FIG.
FIG. 8 is a simplified view of a section of the apparatus used in the enamel coating method using the trolley conveyor of the present invention.
FIG. 9 is an exemplary view of a hanger among apparatuses used in the enamel coating method using the trolley conveyor of the present invention.
10 is a view schematically showing a trolley conveyor passing through a firing chamber and a metal tube in a device used in an enamel coating method using the trolley conveyor of the present invention.
11 is a photograph of a metal tube for a heat exchanger in which heat conductive fins are formed on a surface used for manufacturing a metal tube having an enamel layer according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail since they would unnecessarily obscure the gist of the present invention.

Generally, the metal tube used as a generator heat exchanger is used in a harsh environment. Therefore, in order to prevent corrosion and maintain durability, it is preferable that the thickness of the coated enamel layer of the metal tube is 250 +/- 100 mu m.

In addition, it is preferable that the enamel layer on the side of the end of the heat transfer fin of the metal tube is also formed to have a thickness of 250 +/- 100 mu m.

First, the formation of a coating film having a sufficient thickness on the heat transfer fin end side of the metal tube will be described.

According to the prior art, a metal tube for a heat exchanger in which a heat transfer fin is formed on a surface,

(I) The surface of the metal tube is coated with an enamel glaze,

(II) a method of firing the coated metal tube at a temperature of 750 ° C to 1000 ° C.

The metal tube used in the heat exchanger for a power plant usually has a length of 5 m to 30 m. In order to rotate and move the circular metal tube, an elongated roller is usually arranged at 1.5 m intervals.

In general, about 10 minutes are required for firing (II). In the firing furnace used in the step (II), long rollers for holding six or seven metal tubes are usually used.

In the process of rotating and advancing the metal tube 10 coated with the enamel glaze using the long roller 270 in the firing furnace, as the end of the heat transfer fin of the metal tube contacts the long roller 270 There is a problem that the enamel coating of the part is damaged.

FIG. 2 is a photograph of a state in which enamel is not properly formed at the end portion of the heat transfer fin, that is, the outer edge portion, by a conventional method.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a method of coating a metal tube having a damaged enamel layer by further coating the end of a heat transfer fin or by using a trolley conveyor to move the metal tube vertically and horizontally, Thick enamel layer is formed.

Each of the above-described methods for forming the enamel layer of sufficient thickness on the side of the metal tube heat transfer fin end will be described below.

Additional coating on the end of metal tube heat transfer fin

The enamel glaze powder is applied to the end of the firing pin of the metal tube 10 after the firing process and is further coated and re-fired to re-form the enamel coating of the damaged portion.

As shown in FIGS. 3 and 4, an enamel glaze splitting 131 is disposed at a portion where the end of the heat conductive fin of the metal tube 10 moves, while the metal tube 10 is moved forward while rotating, The end of the heat conductive fin of the honeycomb structure 10 is buried in the enamel glaze powder 132 by about 1 mm to 5 mm, and the enamel glaze powder is coated.

The enamel glaze powder 131 is placed on the lower side of the metal tube so that the end portion of the heat transfer fin advancing and rotating is in contact with the enamel glaze powder 132 in a slightly pressing manner so that the application of the glaze powder is easy, The enamel layer on the end side of the heat conductive fins of the tube is damaged. However, since the enamel is thinly formed, the glaze powder easily adheres.

Further, the additional coating on the heat transfer fin side of the metal tube (10) may be a method of spraying enamel glaze on the end of the heat transfer fin of the metal tube (10) after the sintering process.

5, an enamel glaze spray nozzle 133 is disposed in the additional coating chamber 130, and the enamel glaze spray nozzle 133 is disposed in the enameled glaze spray nozzle 133 in the direction of the heat conductive fin end of the metal tube 10, Spray glaze. At this time, when the injected enamel glaze reaches the end of the heat conductive fin of the metal tube 10, the water of the enamel glaze is evaporated by the hot heat of the surface of the metal tube and the enamel glaze powder is attached to the end of the heat transfer fin of the metal tube 10.

The enamel glaze spraying may be performed such that the enamel glaze spraying nozzle 133 reciprocates at a predetermined interval along the traveling direction of the metal tube 10. The gap between the enamel glaze spray nozzles 133 is preferably 400 mm to 500 mm. In this case, the metal glaze may be more uniformly coated on the heat transfer fin end of the metal tube 10.

Next, the additional coated metal tube 10 is re-fired at 800 ° C to 1100 ° C.

In order to effectively re-form the enamel coating on the end of the heat conductive fin of the metal tube 10, the temperature of the surface of the metal tube 10 should be sufficiently raised so that the enamel glaze powder attached to the end of the heat conductive fin can be completely fired. However, since the re-plasticization chamber 140 in which the re-plasticization process is performed is shorter than the plasticization chamber 120, the time required for the metal tube 10 to pass therethrough is reduced. Therefore, in order to sufficiently increase the temperature of the surface of the metal tube 10, it is necessary to carry out a re-firing process at a temperature of 800 ° C to 1100 ° C higher than the temperature of the firing process.

The re-firing process of the metal tube is preferably performed for 1 minute to 3 minutes. In this case, the enamel coating can be effectively formed at the end of the heat conductive fin of the metal tube 10.

The re-burning chamber 140 is provided with a heating means. As the heating means, any of those commonly used in this field can be used without limitation. For example, an electric furnace, a plasma annealing furnace, a heavy oil furnace, a light oil furnace, a gas furnace, a hydrogen annealing furnace, and an induction heating furnace can be used.

The re-burning chamber 140 may further include a blower. In the course of the re-fired metal tube 10 moving to the outfeed conveyor 300, the enamel coating of the unheated heat transfer fin end may be damaged as it comes into contact with the rollers. Therefore, the temperature of the enamel portion re-formed at the end of the heat transfer fin can be lowered by allowing the metal tube 10 to be passed through the blower before the re-fired metal tube 10 is contacted with the roller of the outfeed conveyor 300, It is possible to prevent damage to the enamel layer re-formed at the end of the heat conductive fin of the tube 11.

Enamel coating of metal tube using trolley conveyor

The present invention can prevent the enamel layer damage on the end of the heat transfer fins of the metal tube (10) by moving the metal tube for heat exchanger having heat transfer fins on its surface by using a trolley conveyor.

The enamel coating method of the present invention will be described with reference to the metal tube enamel coating apparatus of the present invention exemplarily shown in Figs. 8 to 10 as follows.

A method for enamel coating by moving a metal tube (10) for a heat exchanger having heat conductive fins on its surface by using a trolley conveyor (800)

(A) placing a metal tube (10) on a trolley conveyor (800) having a plurality of hanger (820), immersing it in an enamel glaze, removing the enamel glaze, and coating the enamel glaze; And

(B) firing the metal tube coated with the enamel glaze into the firing chamber 120 and firing at a temperature of 750 ° C to 1000 ° C.

The trolley conveyor 800 includes a plurality of hangers 820 for receiving the metal tube 10. As shown in FIG. 9, the hanger 820 supports the metal tube 10 from below so that the metal tube 10 can be mounted on the trolley conveyor 800.

The hanger 820 may include at least two supporting portions 821 protruding in the direction of the metal tube at a portion for supporting the metal tube 10. By providing two or more support portions 821 in the hanger 820, the contact between the hanger 820 and the heat conductive fins of the metal tube 10 can be minimized, The enamel coating damage is prevented, and the enamel coated metal tube 11 of excellent quality can be manufactured.

The metal tube 10 may have a length of 5 m, 10 m or 15 m or more, and the maximum length of the metal tube is 30 m or 40 m or less. The hanger 820 may be provided in a required number according to the length of the metal tube 10 to be coated with enamel and each of the plurality of hanger 820 is provided at an interval of 1.0 m to 1.2 m . When a plurality of hanger (820) are provided at the above-described intervals, it is possible to prevent the metal tube (10) from being bent due to high temperature heat during the firing process.

8, the metal tube 10 is immersed in an enamel oil bath 900, and then the metal tube 10 is taken out of the metal tube 10, An enamel glaze is coated on the surface of the tube (10).

Seal both side openings of the metal tube 10 before the metal tube 10 is immersed in the enamel suspension tank 900. So as to prevent the enamel glaze from penetrating into the interior of the metal tube 10. The sealing method of the opening is not particularly limited as long as it can prevent the enamel glaze from penetrating into the interior of the metal tube 10.

In the step (B), the high-temperature firing step of the metal tube is performed at 750 ° C to 1000 ° C, more preferably 750 ° C to 870 ° C. Therefore, the firing chamber 120 is provided with a heating means. As the heating means, any of those commonly used in this field can be used without limitation. For example, an electric furnace, a plasma annealing furnace, a heavy oil furnace, a light oil furnace, a gas furnace, a hydrogen annealing furnace, and an induction heating furnace can be used.

The firing chamber 120 is provided with a passage 121 at an upper portion of the firing chamber 120 so that the trolley conveyor 800 can pass through the firing chamber 120 during the firing process.

The metal tube 10 coated with enamel glaze is heated to a high temperature inside the firing chamber 120 while the trolley conveyor 800 having the enamel glaze coated metal tube 10 passes through the firing chamber 120 Lt; / RTI > At this time, the trolley conveyor 800 passes through the passage part 121 provided in the upper part of the firing chamber 120. In this case, the trolley conveyor 800 passes through the passage part 121 provided in the upper part of the firing chamber 120, The heat inside the firing chamber 120 may flow out to the outside and the temperature inside the firing chamber 120 may not be maintained constant. Therefore, during the firing process of the metal tube 10, it is necessary to block the passage portion 121 from the outside to keep the temperature inside the firing chamber 120 constant.

Accordingly, in the metal tube enamel coating method of the present invention, the trolley conveyor 800 may include the heat block means 830 to block the passage portion 121 from the outside.

The heat block means 830 moves together along the passage portion 121 when the trolley conveyor 800 passes the firing chamber 120 and moves the width of the heat block means 830 to the passage portion 121, The passage portion 121 can be completely shut off from the outside. Accordingly, the temperature inside the firing chamber 120 can be kept constant while the trolley conveyor 800 passes through the firing chamber 120.

As described above, since the enamel coating is performed by moving the metal tube 10 using the trolley conveyor 100, unlike the conventional method, enamel coating can be effectively formed at the end of the heat conductive fin of the metal tube 10.

FIG. 1 is a photograph of a metal tube coated by the enamel coating method according to the present invention. It can be seen that the end of the heat transfer fin shows a clear blue color. FIG. In the photograph of the tube, it can be seen that the end of the heating pin of the metal tube shows a transparent color.

As shown in FIGS. 1 and 2, in the case of the metal tube coated by the conventional enamel coating method, the enamel coating at the end of the fin is partially damaged to show a transparent color, whereas the enamel coating method according to the present invention In the case of the coated metal tube, the end of the heating pin also shows a vivid blue color, thus effectively forming an enamel coating.

Hereinafter, formation of a coating film of sufficient thickness on the heat transfer fin end side of the metal tube will be described.

As described above, since the metal tube used as the generator heat exchanger is used in a harsh environment, it is preferable that the thickness of the coated enamel layer of the metal tube is 250 +/- 100 mu m in order to prevent corrosion and maintain durability.

However, when the viscosity of the enamel glaze is increased to increase the thickness of the enamel layer coated on the cylindrical metal tube, since the degree of the flow of the enamel glaze from the surface of the metal tube can be reduced, However, since the enamel glaze is not evenly applied due to the increased viscosity, it is difficult to form a uniform enamel layer.

In order to uniformly apply the glaze to the cylindrical metal tube, the viscosity of the glaze is preferably 9 to 13. The viscosity of the glaze is measured by immersing a 10 cm x 10 cm x 0.5 mm stainless steel plate in a glaze liquid, placing the iron plate with a forceps and vertically erecting the liquid to flow down, and then placing the glaze on the iron plate. That is, the weight of the iron plate after immersing in the glaze is measured in grams, and the viscosity of the glaze is measured.

When a glaze having a viscosity of 9 to 13 is coated on a cylindrical metal tube and then an enamel layer is formed by firing, the thickness of the enamel layer is formed to be thinner than 250 +/- 100 mu m.

In the present invention,

(a) coating the surface of the metal tube with an enamel glaze;

(b) firing the coated metal tube at a temperature of 750 ° C to 1000 ° C;

(c) further coating an enamel glaze on the end of the fins of the fired metal tube; And

(d) after the step of re-firing the further coated metal tube at a temperature of 800 ° C to 1100 ° C,

By repeating the above steps (a) to (d), a metal tube having an enamel layer thickness of 250 +/- 100 mu m was obtained.

In the present invention,

(A) placing a metal tube (10) on a trolley conveyor (800) having a plurality of hanger (820), immersing it in an enamel glaze, removing the enamel glaze, and coating the enamel glaze; And

(B) After the metal tube coated with the enamel glaze enters the firing chamber 120 and firing is performed at a temperature of 750 ° C to 1000 ° C,

By performing the above steps (A) and (B) once again, a metal tube having an enamel layer thickness of 250 ± 100 μm was obtained.

With the above-described method, a metal tube for a heat exchanger of excellent quality formed with a uniform enamel layer can be obtained without increasing the viscosity of the enamel glaze.

10: metal tube 11: enamel coated metal tube
100: coating part 110: coating chamber
120: firing chamber 121: passage part
130: additional coating chamber 131: enamel glaze minutes
132: enamel glaze powder 133: enamel glaze jet nozzle
134: Connection bar 135:
140: Re-plasticizing chamber 210: In-feed conveyor die
270: Long spherical roller 300: Out-feed conveyor
400: Coating chamber conveyor 500: Conveyor for plastic chamber
600: Additional coating chamber conveyor 700: Conveyor for re-plasticizing chamber
800: Trolley conveyor 810:
820: Hanger 821: Support
830: Train terminal unit 900: Emerald oil provision
The above description is merely illustrative of the technical idea of the present invention, and it will be apparent to those skilled in the art that various modifications may be made without departing from the essential characteristics of the present invention. Therefore, the technical idea of the present invention is not limited to the above embodiment.

Claims (1)

A metal tube for a heat exchanger in which a heat conductive fin is formed on a surface of the metal tube, the metal tube having a length of 5 m or more, an enamel layer formed on the surface of the metal tube, and an enamel layer having a thickness of 250 ± 100 μm.

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