METHOD FOR MANUFACTURING STEAM CONDENSATION HEAT TRANSFER
PIPE
This application claims the benefit of earlier filing date and right of priority to Korean Patent Application No. 10-2015-0169736, filed on December 01, 2015, the contents of which are hereby incorporated by reference in their entirety.
BACKGROUND OF THE DISCLOSURE
Field
The teachings in accordance with the exemplary embodiments of this present disclosure generally relate to a steam condensation heat transfer pipe, and more particularly, to aluminum clad oblong tube steam condensation heat transfer pipe used for air-cooling steam condensation facilities.
Background
An atomic power plant or a thermoelectric power plant uses fuels such as uranium, kerosene and coal to generate heat, and uses the heat to circulate water in a system and to generate steam. The generated steam rums a turbine to generate electricity, where the turbine-passed steam is cooled by a condenser to become water again.
Particularly, a water-cooling method, in which water is used to cool a condensing process in the steam circulation power generating method, needs a large amount of cooling water, such that sea water is usually used as cooling water in the condenser. Thus, the atomic power plant or the thermoelectric power plant is usually built near seaside to smoothly get supplied with and discharge the sea water that is used as cooling water.
Meantime, the sea water used as cooling water is discharged in a heated state by passing through a cooling system of the power plant. The sea water discharged to the sea from the power plant in the heated state amounts to hundreds of tons per hour. The sea water in the heated state increases temperature of sea water to create various environmental problems such as destructing marine ecosystem, to name a few.
Furthermore, an amount of cooling water to be supplied to steam condenser is absolutely

insufficient in land-locked countries, such that there arises a problem of using a water-cooling condenser as a cooling system.
In light of the aforementioned problems, power plants using air-cooling condenser has been recendy proposed, and are widely used in up-countries in China and US, for example, where sea water supply is insufficient. Although the power station using air-cooling condenser is disadvantageous in that facilities become bulky over the existing water-cooling condenser, the power station using air-cooling condenser has come into limelight as environment-friendly power generating facilities due to the fact that it can be advantageously installed at an inland area instead of seaside area to provide a relative flexibility in selecting a location for a power plant over a power plant that must use the water-cooling condenser, and can be free from fear of creating a marine pollution caused by temperature rise in sea water resultant from input/output of cooling water.
The air-cooling condenser uses a large number of tubes, where the tube may be categorized into two types based on the shape, that is, an SRC (Forged Row Condenser) tube and an MRG (Multi Row Galvanized) tube.
The steam condensing heat transfer pipe for power plants has a structure in which an aluminum fin is brazed to both sides of clad tube made of aluminum and steel stacks. An external surface of aluminum in the steam condensation heat transfer pipe for power plants is oxidized after brazing to be denaturalized in structure into aluminite, such that no surface corrosion is generated in the air above a predetermined level.
Furthermore, a borderline between an aluminum fin and aluminum clad material on external surface of the fused clad tube is a connective tissue of completely fused metal that has an advantageously perpetual heat transfer effect without any corrosion.
The steam condensing heat transfer pipe for power plants must maintain 5 ~10 times larger cross-section than that of a cylindrical small tube (1"~2") to have a relatively large cross-sectional area, whereby inside air of non-condensable gas can be rapidly removed to allow a rapid initial start operation and to advantageously dispense with an inner freezing of condensing water during winter operation due to larger flow of condensing water man that of a

heat transfer pipe with a small cross-section.
Meanwhile, the conventional heat exchange type cylindrical MRG tube is externally attached with cooling pins for increasing heat transfer effect using various methods. The metal fusion method is an electric resistance welding method using same kind metals, which is the closest method for obtaining an intrinsic tube effect by the welded cooling fins. However, the electric resistance welding method is disadvantageous in that each fin is thickened and difficulty arises in arranging a large number of pins in order to allow each of the cooling fins to have an adequate cross-section for electric resistance welding. The disadvantage results in degradation of cooling effect caused by decreased heating surface.
In order to solve the aforementioned disadvantages, the cooling fins may be embedded into the surface of the tube, but the embedment leads to decreased performance of entire facilities due to rapid degradation of heat transfer capability of intrinsic function of the tube caused by generation of galvanic corrosion at the borderline 2 ~ 3 months after exposure to air upon start of operation.
The conventional MRG tube heat transfer pipe has been largely applied for domestic and foreign consumption for heat transfer by air-cooling heat exchange, because the steam condensation heat transfer pipe is poor in pressure-resistance, and high in manufacturing cost over the MRG tube heat transfer pipe. However, the steam condensation transfer pipe is relatively excellent over the MRG tube heat transfer pipe, because steam condensation is easy if degree of vacuum is high and differential vacuum pressure is applied to an interior of the steam condensing tube.
Since 1990s, the conventional steam condensation heat transfer pipe for power plants developed and used particularly for European countries and US has a high defect rate in brazing process of aluminum pins and clad tubes due to outdated manufacturing method to act as a factor increasing a manufacturing cost of product.
FIG. 1 is an exploded perspective view and flow chart of manufacturing process of air-cooling steam condensation heat transfer pipe for steam condensation facilities according to the prior art.
In order to braze the clad tubes and aluminum fins according to the conventional method, steel fixed frames are vertically arranged between which an aluminum fin, a clad tube and an aluminum fin are sequentially arranged, and a portion where the aluminum fin and the clad tube

face each other is coated with flux, wrapped with steel wire and inputted into an electric heating furnace. Then, the aluminum fins are depressed inside the high-temperature furnace by self weight of the steel fixing frames to be fused to upper/lower surfaces of the clad tube.
At this time, in order to bond the aluminum fin and the clad tube, a strip fin, which is an aluminum fin, is made of post-processed aluminum 4XXXb in order to allow aluminum 4XXX, which is an AL-Si series alloy, to be exposed on a surface of aluminum alloy 3003.Thus, bondage is realized by coating flux on the clad tube using heat and pressure. Meantime, when the aluminum fins are partially and excessively heated, and applied with an excessive power, chances are the aluminum fins are fused to the clad tube and to the frame as well. Under these circumstances, a torch is used to separate the aluminum fin from the frame, where the product may be inevitably damaged and no longer unusable.
Furthermore, aluminum 4XXX is an non-heat treated alloy with silicon (Si) as a main added element, and used as a welding material, and relatively high-priced over aluminum alloy 3003 generally used for building materials, vehicular materials and various other materials. The reason of the relatively high-priced aluminum 4XXX being used for strip fins is to satisfactorily form a filler in the process of the aluminum alloy 4343 or 4045 material exposed to the strip fin being brazed in a heating furnace with the clad tube, when the clad tube and the strip fin are brazing-coupled. However, the aluminum 4XXX portion actually forming the filler is only at vicinity where the clad tube and the strip fin are mutually contacted, and other portions require no use of aluminum alloy 4343 or 4045 material such that improvement is demanded in terms of cost-saving aspect.
FIG. 2 is an exploded perspective view and flow chart of manufacturing process of air-cooling steam condensation heat transfer pipe for steam condensation facilities according to another prior art. FIG. 3 is an enlarged cross-sectional view of a joint between a fin strip member and a clad tube surface in the air-cooling steam condensation heat transfer pipe for steam condensation facilities.
First, a method for manufacturing steam condensation heat transfer pipe is performed as below: That is, a fin strip member is formed, a clad tube is pre-processed, and aluminum paste is coated on all lateral surface of the clad tube. Then, the fin s trip member is arranged on a surface coated with the aluminum paste of clad tube, the product is assembled inside a jig, brazed and

completed. At this time, the aluminum paste is in a state of the aluminum alloy 4XXX being mixed with the flux. The flux is coated on a whole lateral surface of the clad tube to be bonded with the fin strip member.
However, the conventional method of manufacturing the steam condensation heat transfer pipe suffers from disadvantages in that the flux or paste is coated on an area other than that abutted by the clad tube and the fin strip member. Thus, more fluxes and pastes are used than are actually necessary, causing a limitation in materials resultant therefrom.
SUMMARY
The present disclosure has been made to solve the foregoing disadvantages of the prior art and therefore an object of certain embodiments of the present disclosure is to provide a method for manufacturing steam condensation heat transfer pipe configured to reduce manufacturing cost of fin strip member by using a forged aluminum alloy such as aluminum alloy 3003 for fin strip member, and to couple a clad tube with a fin strip member using a small amount of brazing paste.
Technical subjects to be solved by the present disclosure are not restricted to the above-mentioned description, and any other technical problems not mentioned so far will be clearly appreciated from the following description by the skilled in the art. That is, the present disclosure will be understood more easily and other objects, characteristics, details and advantages thereof will become more apparent in the course of the following explanatory description, which is given, without intending to imply any limitation of the disclosure, with reference to the attached drawings.
An object of the invention is to solve at least one or more of the above problems and/or disadvantages in whole or in part and to provide at least advantages described hereinafter. In order to achieve at least the above objects, in whole or in part, and in accordance with the purposes of the disclosure, as embodied and broadly described, and in one general aspect of the present invention, there is provided a method for manufacturing steam condensation heat transfer pipe, the method comprising:
forming a fin strip member by bending a clad tube and a plate having an opening at both ends and including at least one pair of flat heat transfer parts several times and in same size and same

interval;
coating a paste on the clad tube and the heat transfer part abutted by the fin strip member by
forming a plurality of parallel linear lines, and coating a brazing stopper or anti-flux on an
outside of the paste coated on the heat transfer part; and
joining the clad tube and the fin strip member to allow the paste and a bent part of the fin strip
member to cross each other.
Preferably, but not necessarily, the step of joining the clad tube and the fin strip member may
include:
accommodating the fin strip member on the clad tube to allow the paste and the fin strip member
to cross (to be orthogonal to each other); and brazing the clad tube accommodated with the fin
strip member..
Preferably, but not necessarily, the paste may be comprised of 4XXX aluminum alloy.
Preferably, but not necessarily, the fin strip member may be an AA3003 alloy.
ADVANTAGEOUS EFFECTS
The present invention has an advantageous effect in that a manufacturing cost of fin strip member can be reduced by using a single aluminum alloy such as aluminum alloy 3003, and a flux coating process can be substituted with a simple paste coating process, and a brazing fillet can be formed with a thicker and excellent manner to thereby reduce the weight of steam condensation heat transfer pipe.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the disclosure, and together with the description serve to explain the principle of the disclosure. In the drawings:
FIG. 1 is an exploded perspective view and flow chart of manufacturing process of air-cooling steam condensation heat transfer pipe for steam condensation facilities according to the prior art;

FIG. 2 is an exploded perspective view and flow chart of manufacturing process of air-cooling
steam condensation heat transfer pipe for steam condensation facilities according to another prior
art;
FIG. 3 is an enlarged cross-sectional view of a joint between a fin strip member and a clad tube
surface in the air-cooling steam condensation heat transfer pipe for steam condensation facilities;
FIG. 4 is a flowchart of a method for manufacturing steam condensation heat transfer pipe
according to an exemplary embodiment of the present disclosure;
FIG. 5 is a perspective view illustrating a strip member according to an exemplary embodiment
of the present disclosure;
FIG. 6 is a perspective view illustrating a clad tube according to an exemplary embodiment of
the present disclosure;
FIG. 7 is a perspective view illustrating a state of paste being coated on the clad tube in a method
for manufacturing steam condensation heat transfer pipe according to an exemplary embodiment
of the present disclosure;
FIG. 8 is an enlarged view illustrating a contact surface between a clad tube of steam
condensation pipe and a fin strip member according to an exemplary embodiment of the present
disclosure;
FIG. 9 is a cross-sectional view of a steam condensation pipe manufactured according to the
conventional manufacturing method; and
FIG. 10 is a cross-sectional view of a steam condensation pipe manufactured according to an
exemplary embodiment of the present disclosure.
DETAILED DESCRIPTION
Various exemplary embodiments will be described more fully hereinafter with reference to the accompanying drawings, in which some exemplary embodiments are shown. The present inventive concept may, however, be embodied in many different forms and should not be construed as limited to the example embodiments set forth herein. Rather, these exemplary embodiments are provided so that this description will be thorough and complete, and will fully convey the scope of the present inventive concept to those skilled in the art.
It will be understood that when an element or layer is referred to as being "on," "connected to" or "joined to" another element or layer, it can be directly on, connected or joined to the other element or layer or intervening elements or layers may be present. In contrast, when an element

is referred to as being "directly on," "directly connected to" or "directly joined to" another element or layer, there are no intervening elements or layers present. Like numerals refer to like elements throughout.
It will be understood that, although the terms first, second, third etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present inventive concept.
As used herein, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this inventive concept belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments of the disclosure.
Hereinafter, a method for manufacturing a steam condensation heat transfer pipe according to an exemplary embodiment of the present disclosure will be described in detail with reference to the accompanying drawings.
FIG. 4 is a flowchart of a method for manufacturing steam condensation heat transfer pipe

according to an exemplary embodiment of the present disclosure.
The method for manufacturing steam condensation heat transfer pipe, may include coating a paste on the clad tube, and coupling the clad tube and the fin strip member.
The step of coating a paste on the clad tube includes a step of coating a paste, which is a bonding material for bonding the clad tube and the fin strip member, on the clad tube and the heat transfer part.
The fin strip member may be accommodated on the heat transfer part of the clad tube in a steam condensation heat transfer pipe to emit outside a heat of a material passing through an inside of the clad tube. That is, the fin strip member may perform a function of a cooling fin and discharge the heat transmitted dirough an inside of the clad tube by being accommodated on a pair of heat transfer part.
FIG. 5 is a perspective view illustrating a strip member according to an exemplary embodiment of the present disclosure.
As illustrated in the drawings, the fin strip member may be formed by bending a plate material several times with a same size and at a same interval. The bent-shaped fin strip member can be attached to a lateral surface of the clad tube to effectively discharge the heat generated from the clad tube because the fin strip member has a broader surface contacting an outside air.
The fin strip member may use AA3003, which is a forged rolled product. Although the conventional steam condensation heat transfer pipe was configured in such a manner that flux was coated on the clad tube on which the fin strip member was joined or bonded, and therefore, a single-surfaced rolled product in which AA3003 and 4XXX form two layers was used, the method for manufacturing the steam condensation heat transfer pipe according to die present disclosure is such that paste is coated and bonded to the fin strip member, and fin strip member can be used with a single-layered aluminum alloy, whereby process can be further simplified.
The clad tube may be a main body of the steam condensation heat transfer pipe, and include a flat heat transfer part formed with an opening at both ends.

FIG. 6 is a perspective view illustrating a clad tube according to an exemplary embodiment of the present disclosure.
The clad tube may be formed with an opening at both ends, and joined to the fin strip member at a flat heat transfer part having at least one pair of flat heat transfer parts. That is, when heat is emitted from a material passing through an inside of the clad tube, the heat is discharged through the heat transfer part, whereby the heat can be effectively discharged through the fin strip member.
The paste may be a material coated on the heat transfer part of clad tube in a plurality of linear shapes to couple the fin strip member with the clad tube. The paste may be formed by mixing the flux material with aluminum alloy material in a gel state. The aluminum alloy material may be Al-Si alloy and may be formed with aluminum alloy 4XXX-. The aluminum alloy 4XXX may be a non-heat treated alloy with Si as a main additive component and largely used for welding and brazing. The paste according to the present disclosure may further include an organic binder, and may be 4XXX aluminum alloy.
FIG. 7 is a perspective view illustrating a state of paste being coated on the clad tube in a method for manufacturing steam condensation heat transfer pipe according to an exemplary embodiment of the present disclosure.
The clad tube and the fin strip member are such that a bent part of the fin strip member contacts the heat transfer part of the clad tube, where a contacted portion becomes a plurality of parallel lines. The paste may be coated in a plurality of parallel lines to cross (to be orthogonal to) the plurality of parallel lines contacted by the clad tube and the fin strip member. That is, the fin strip member and the clad tube may be bonded or joined in order to allow the bent part of the fin strip member to be orthogonal to the paste by coating the paste on the clad tube in a plurality of linear lines.
At this time, an external part of the coated plurality of linear pastes may be coated with stopper or anti-flux. A distal end of the paste may be coated with brazing stopper to allow the aluminum fin strip member to be brazing-joined within a limited scope.
The step of joining the clad tube with the fin strip member includes, as discussed above, a

joining at a right angle between the plurality of parallel lines contacted by the clad tube and the fin strip member and the coated paste. When the clad tube and the fin strip member are joined to perform the brazing process, the paste partially contacting the bent part of the fin strip member is wetted and moved to the bent part of the fin strip member, where most of the pastes are moved to a portion contacted by die fin strip member and the clad tube, whereby a thin layer of some pastes is formed on the heat transfer part of the clad tube.
Here, the meaning of brazing is a metal-joining process in which two or more base metals are joined together at a temperature above 450°C by melting and flowing a filler metal into the joint with heat, the filler metal having a lower melting point than the adjoining metal without damaging the base metals below the melting point. That is, the brazing is a method of joining two base metals by applying a heat of less than solidus temperature, using a filler metal having a liquidus temperature of above 450°C. The most ideal brazing is to maintain an optimum temperature when a brazing filler metal is melted and flown between two adjoining metals, and it is possible to add various environmental characteristics thereto in addition to the brazing. At this time, a physical property indicating a degree of affinity of two base metals and filler metal is expressed as wetting, and the phenomenon of the filler metals being flown between two adjoining metals is called a capillary action. The brazing fillet formed by the brazing process can be excellently formed with a thicker thickness to thereby improve the brazing strength.
FIG. 8 is an enlarged view illustrating a contact surface between a clad tube of steam condensation pipe and a fin strip member according to an exemplary embodiment of the present disclosure.
Referring to FIG. 8, the steam condensation heat transfer pipe manufactured by the method for manufacturing steam condensation heat transfer pipe according to an exemplary embodiment of the present disclosure is configured such that the brazing fillet is excellently formed at a contact portion between the clad tube and the fin strip member, and the paste forms a thin film at an upper end of the clad tube to thereby function as a protective film at the upper end of the clad tube. Thus, the heat transfer pipe, which is an aluminum alloy, can be delayed in corrosion to maintain a long time durability for the heat transfer pipe in the power plant facilities.
FIG. 9 is a cross-sectional view of a steam condensation pipe manufactured according to the conventional manufacturing method, and

FIG. 10 is a cross-sectional view of a steam condensation pipe manufactured according to an exemplary embodiment of the present disclosure.
Referring to FIGS. 9 and 10, when the steam condensation heat transfer pipe is brazed, and when the steam condensation heat transfer pipe is perpendicularly and lengthwise inserted, the paste may be induced into the fin strip member to decrease the efficiency because of reduced cross-section of the fin strip member as illustrated in FIG. 9 according to the prior art. However, as illustrated in FIG. 10, the steam condensation pipe manufactured according to an exemplary embodiment of the present disclosure may be coated with an adequate amount of paste and wetted along the fin strip member during brazing process to thereby increase the efficiency over the steam condensation pipe manufactured according to the prior art because of no blocking of die fin strip member. Furthermore, an outside of the coated paste is coated with brazing stopper to prevent the paste from being flown out.
The previous description of the present invention is provided to enable any person skilled in the art to make or use the invention. Various modifications to the invention will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the spirit or SGope of the invention. Thus, the invention is not intended to limit the examples described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

WHAT IS CLAIMED IS:
1. A method for manufacturing steam condensation heat transfer pipe, the method comprising:
forming a fin strip member by bending a clad tube and a plate having an opening at both ends and including at least one pair of flat heat transfer parts several times and in same size and same interval;
coating a paste on the clad tube and the heat transfer part abutted by the fin strip member by forming a plurality of parallel linear lines, and coating a brazing stopper or anti-flux on an outside of the paste coated on the heat transfer part;
accommodating the fin strip member on the clad tube to allow the paste and the fin strip member are orthogonal to each other; and
brazing the clad tube accommodated with the fin strip member.
2. The method of claim 1, wherein the paste is comprised of 4XXX aluminum alloy.
3. The method of claim 1, wherein the fin strip member is an AA3003 alloy.