Manufacturing method for heat exchanger core

Abstract

To reduce a manufacturing process in a manufacturing method of a core part where a corrugated fin surface needs to be protected from oxidation corrosion in which the core part is arranged in a heat exchanger with the corrugated fin at a flow channel for heat exchange between high-temperature fluid and low-temperature fluid.SOLUTION: A manufacturing method of a core part of a heat exchanger 6 where a corrugated fin 6c is arranged between a plurality of plates 6w and an apex part 6 of the corrugated fin is bonded to the plate comprises the steps of: laminating a brazed sheet 6m which is made of a brazing filler metal and formed shaped to conform to a wavy shape of the corrugated fin on the corrugated fin so that the wavy shape of the brazed sheet is overlapped with the wavy shape of the corrugated fin; sandwiching the laminated body between the plurality of plates; and heating the plurality of plates and the laminated body held therebetween and melting the brazing filler metal of the brazed sheet to braze the apex part of the corrugated fin to the plates and coat a whole area of the corrugated fin surface with the brazing filler metal.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a heat exchanger for exchanging heat between a high-temperature fluid and a low-temperature fluid, and more particularly to a method for manufacturing a core portion of a heat exchanger through which a fluid passes. [Background technology]

[0002] Heat exchangers that exchange heat between a high-temperature fluid and a low-temperature fluid are used in various industrial machines, plants, etc. For example, in a gas turbine engine, high-temperature exhaust gas discharged from a combustor through a turbine and low-temperature compressed air sent to the combustor are passed through the heat exchanger to transfer heat from the high-temperature exhaust gas to the low-temperature compressed air, thereby increasing the energy efficiency of the engine. In a typical structure of the core part of such a heat exchanger, that is, the part that defines the flow path through which the high-temperature fluid and the low-temperature fluid flow while being in thermal contact with each other, for example, as shown in Fig. 3(B) , corrugated fins made of a thin metal plate deformed into a wave shape are arranged in the flow path so that grooves formed between the waves are aligned along the flow direction of the fluid, thereby increasing the heat transfer area between the fluids.

[0003] In the core of the above-mentioned heat exchanger, the corrugated fins need to be more appropriately joined to the inner wall, which is made of a partition plate or the like that defines the flow path, so as to prevent leakage of fluid and falling off or deformation of the fins, and various techniques for this purpose have been proposed. For example, Patent Document 1 proposes that in a structure in which the corrugated fins are sandwiched between a number of plates, a sheet-like brazing material is interposed between the plates and the fins, and in a state in which sidewall materials are adjacent to both edges of the fins, the plates and the sidewall materials are welded while applying a pressing force to the multiple plates, and then a powdered brazing material is applied from the outside to the joint between the plates and the sidewall materials, and the laminate of the plates, fins, and sidewall materials is heated and brazed in a vacuum atmosphere or an inert gas atmosphere, thereby manufacturing a core that is free from the risk of leakage. In addition, Patent Document 2 proposes a new manufacturing method for a composite material applicable to heat exchangers, etc., in which a brazing material is sintered on at least one surface of a substrate to form a clad brazing material, the clad brazing material is then plastically deformed into a shape in which recesses and protrusions are repeatedly arranged, a plurality of deformed clad brazing materials are stacked in a state in which the recesses or protrusions are in contact with each other, and the temperature of the brazing material is raised to the brazing temperature to braze the recesses or protrusions in contact with each other. Patent Document 3 proposes using a thin brazing foil that is an elastic bellows-folded body as a brazing material for joining the corrugated fin and the top plate in a structure in which a corrugated fin having a fin flow path through which a cooling medium flows is arranged in a box-shaped frame with an open top, and the opening of the frame is sealed and covered with a top plate, in order to prevent the shapes of the corrugated fin and the top plate from being deformed when the corrugated fin is joined to the frame and the top plate. Patent Document 4 proposes using a plate-shaped brazing material with protrusions to fix the corrugated fins on the air inlet side and the air outlet side at a predetermined distance from each other between flat heat transfer tubes bent in a serpentine shape, and by arranging the protrusions between the corrugated fins on the air inlet side and the air outlet side, the corrugated fins are positioned in their respective positions and then heated and brazed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 06-238432 [Patent Document 2] Patent Publication No. 2006-297450 [Patent Document 1] Patent Publication No. 2012-135773 [Patent Document 2] Japanese Patent Application Publication No. 02-89562 Summary of the Invention [Problem to be solved by the invention]

[0005] In the core part of the heat exchanger as described above, particularly when a fluid that may oxidize and corrode the surface of the corrugated fins, such as high-temperature exhaust gas from a combustor of a gas turbine, flows through the flow passage in which the corrugated fins are arranged, a coating is applied to protect the surface of the corrugated fins in order to prevent deterioration of the surface of the corrugated fins. Therefore, a process of coating the surface of the corrugated fins with a protective film is usually carried out before or after joining the corrugated fins to the inner wall of the flow passage.

[0006] In one embodiment of a method for manufacturing a core part of a heat exchanger, when the corrugated fin is brazed to the inner wall of the flow path, a sheet made of brazing material is placed between the inner wall of the flow path and the corrugated fin, and the brazing material sheet is melted and the corrugated fin is bonded to the inner wall of the flow path. In this method for bonding the corrugated fin, the brazing material spreads and adheres to the vicinity of the bonding part of the corrugated fin due to its wettability. According to research by the inventors of the present invention, it has been found that the part of the corrugated fin covered with the brazing material is less susceptible to oxidation corrosion caused by a fluid even without a protective film. For this reason, if the brazing material sheet is placed so that the entire surface of the corrugated fin is covered with the brazing material when the corrugated fin is brazed to the inner wall of the flow path, the brazing material functions as a protective film, and a separate process of coating the surface of the corrugated fin with a protective film is not required, which is advantageous in reducing the manufacturing process of the core part of the heat exchanger. This finding is utilized in the present invention.

[0007] Thus, one object of the present invention is to reduce the number of manufacturing steps in a method for manufacturing a core part of a heat exchanger having corrugated fins in a flow passage used for heat exchange between a high-temperature fluid and a low-temperature fluid in a gas turbine engine or the like, which requires treatment to protect the surface of the corrugated fins from oxidation corrosion caused by the fluid. [Means for solving the problem]

[0008] According to the present invention, the above problem is solved by a method for manufacturing a core part of a heat exchanger in which corrugated fins are disposed between a plurality of plates and the tops of the corrugated fins are joined to the plates, comprising: a step of laminating a brazing sheet made of a brazing material and shaped to conform to the wavy shape of the corrugated fin on the corrugated fin such that the wavy shape of the brazing sheet overlaps the wavy shape of the corrugated fin, and sandwiching the laminate between the plurality of plates; a step of heating the plurality of plates and the laminate sandwiched therebetween to melt the brazing material of the brazing sheet to braze the tops of the corrugated fins to the plates and coat the entire surfaces of the corrugated fins with the brazing material; Methods including This is achieved by:

[0009] In the above configuration, as already described, the "heat exchanger" may be a heat exchanger that typically performs heat exchange between combustion air (low temperature fluid) supplied to a combustor such as a gas turbine engine and exhaust gas (high temperature fluid) from the combustor, but is not limited thereto. In the "core portion", the "plurality of plates" may be metal plate-like members (partition plates) that are shaped and arranged to define a flow path for the fluid to be heat exchanged, and their surfaces become the inner walls of the flow path. The "corrugated fin" is a member formed by curving a thin metal plate into a number of wave-like shapes, and is arranged in a flow path defined by the plurality of plates, and the tops of the corrugated fins, i.e., the convexly curved portions of the wave-like shapes, are joined to the surfaces of the plates by brazing. Such brazing may be performed by any brazing method, but may typically be achieved by heating the corrugated fin sandwiched between the plurality of plates via a brazing sheet in a vacuum furnace to melt the brazing material.

[0010] In the manufacturing method of the core part of the heat exchanger as described above, the brazing sheet made of the brazing material is a sheet formed into a wavy shape to match the wavy shape of the corrugated fin, and the corrugated fin is sandwiched between a plurality of plates in a state where the brazing sheets are stacked so that the wavy shapes overlap, and is heated to perform the brazing process. In this way, not only are the tops of the corrugated fin brazed to the surfaces of the plates, but the entire surface of the corrugated fin is covered with the brazing material due to the wettability of the molten brazing material. As already mentioned, according to the knowledge of the inventors of the present invention, the corrugated fin is prevented from being corroded by oxidation in the areas of the corrugated fin covered with the brazing material even when high-temperature exhaust gas flows through the corrugated fin. Therefore, according to the configuration of the present invention, it is not necessary to apply a separate protective film for preventing oxidation corrosion to the corrugated fin, and the manufacturing process is reduced.

[0011] The brazing sheet formed into a wave shape can be formed using a mold for forming corrugated fins.

[0012] In the above configuration, the brazing sheet formed into a wave shape may be used only for joining the corrugated fins in a flow path through which an oxidizing and corrosive fluid flows. For example, in a flow path through which a fluid that does not have an oxidizing and corrosive effect flows, such as combustion air supplied to a combustor of a gas turbine engine, a flat, normal brazing sheet may be used between the corrugated fins and the plate for brazing. Effect of the Invention

[0013] According to the above-mentioned configuration of the present invention, in the manufacturing of the flow passage portion of the core part of the heat exchanger through which the oxidizing and corrosive fluid flows, the entire surface of the corrugated fin can be covered with the brazing material having the oxidizing and corrosive preventing effect at the same time as joining the corrugated fin to the plate, so that a separate step of covering the corrugated fin with a protective film for preventing oxidizing and corrosive is not required, and the cost for covering the protective film can be saved. The present invention may be adopted not only for the manufacturing of heat exchangers for gas turbine engines, but also for the manufacturing of any heat exchanger having a flow passage through which the oxidizing and corrosive fluid flows.

[0014] Other objects and advantages of the present invention will become apparent from the following description of preferred embodiments of the invention. [Brief description of the drawings]

[0015] [Figure 1] Fig. 1(A) is a schematic cross-sectional view of a corrugated fin and a brazing sheet laminated on the surface of the corrugated fin. Fig. 1(B) and (C) are schematic cross-sectional views of a core part of a heat exchanger according to this embodiment, where (B) shows the state before brazing and (C) shows the state after brazing. [Diagram 2] FIG. 2A is a flowchart of the manufacturing process of the core part of the heat exchanger according to this embodiment, and FIG. 2B is a flowchart of the manufacturing process of the core part of a conventional heat exchanger. [Diagram 3] Fig. 3(A) is a schematic diagram showing a schematic configuration of a gas turbine engine in which the heat exchanger according to the present embodiment can be used, and Fig. 3(B) is a schematic cross-sectional view of a core part of the heat exchanger. [Figure 4] 4(A) and (B) are schematic cross-sectional views of a core part of a conventional heat exchanger, where (A) shows the state before brazing treatment and (B) shows the state after brazing treatment. [Diagram 5] Figure 5(A) is an electron microscope photograph of the cross section of the joint between the corrugated fin and the plate in the core part of an actual heat exchanger, and Figure 5(B) is an electron microscope photograph of the cross section of a part of the corrugated fin with an oxide layer formed on the surface. [Explanation of symbols]

[0016] 1. Gas turbine engine 2. Combustor 3. Compressor 4...Rotation axis 5. Turbine 6...Heat exchanger 6a…Compressed air flow path of heat exchanger (low temperature flow path) 6b…Exhaust gas flow path of heat exchanger (high temperature flow path) 6c…Corrugated fin 6m…Brazing sheet 6t…Top of corrugated fin Ar…air pAr…Compressed air BG: Combustion gas WG…Exhaust gas BEST MODE FOR CARRYING OUT THEINVENTION

[0017] Gas turbine engine and equipment configuration With reference to FIG. 3(A), the manufacturing method of the core part of the heat exchanger of this embodiment may be used for manufacturing the core part of a heat exchanger 6 to be installed in a gas turbine engine 1, for example. The gas turbine engine 1 may be, for example, a normal gas turbine engine having a combustor 2, a compressor 3, and a turbine 5. The combustor 2 mixes and burns fuel FL supplied from a fuel supply line with compressed air parAr, which is compressed air Ar taken in from the atmosphere by the compressor 3 and passed through a heat exchanger 6, and delivers high-temperature and high-pressure combustion gas BG. The turbine 5 is rotated by the combustion gas BG from the combustor 2, and the compressor 3 is rotated by the rotation, compressing the air Ar taken in from the atmosphere as described above and delivering it to the combustor 2. In addition, an arbitrary machine such as a generator is connected to the rotating shaft 4 of the turbine 5, and the rotational energy of the turbine 5 is recovered by the machine such as the generator or used as energy for operating the machine. Furthermore, since the exhaust gas WG discharged from the turbine 5 has a high temperature, its thermal energy is utilized to raise the temperature of the compressed air parAr to be fed to the combustor 2, and in order to improve energy efficiency, the flow path 6b of the exhaust gas WG and the flow path 6a of the compressed air parAr pass through the heat exchanger 6 while being in thermal contact with each other, and the thermal energy of the exhaust gas WG is transferred to the compressed air parAr. More specifically, as shown in FIG. 3(B), the core portion in which the low-temperature fluid and the high-temperature fluid flow and are in thermal contact with each other is physically partitioned by thermally conductive partition walls 6w, and each flow path has a core portion in which corrugated fins 6c are arranged so that the flow paths are in thermal contact over as wide an area as possible. In such a configuration, in the compressed air flow path 6a, compressed air is pressure-fed from the compressor 3 toward the combustor 2, and in the exhaust gas flow path 6b, exhaust gas is pressure-fed from the combustor 2 through the turbine 5.

[0018] In the core of the heat exchanger, the thermally conductive partition (plate) 6w may be made of a commonly used metal material such as steel. The corrugated fin 6c may be formed by pressing or sheet metal processing using a die having a corrugated shape made of a commonly used metal plate material having high thermal conductivity such as an aluminum sheet. The corrugated fin 6c is brazed and joined to the partition 6w by a brazing material commonly used to join such metal materials.

[0019] Basic manufacturing method for the core part of a heat exchanger In a basic manufacturing method of the core part having the above-mentioned structure in which the corrugated fin 6c is sandwiched and joined between the partition walls 6w, first, as shown in Fig. 4(A), when the corrugated fin 6c is arranged between the partition walls 6w, a brazing sheet 6m made of a brazing material is sandwiched between the top 6t of the corrugated fin 6c and the surface of the partition wall 6w, and in this state, the brazing sheet 6m is heated in a vacuum furnace. The heating conditions in the vacuum furnace may be the same as those usually used for brazing metal materials. Then, as shown in Fig. 4(B), the brazing sheet 6m melts and bonds between the surface of the partition wall 6w and the top 6t of the corrugated fin 6c, and when the temperature drops, the brazing is completed.

[0020] The basic manufacturing method of the core part is as described above, but the corrugated fin 6c arranged in the flow path through which the combustion exhaust gas of the gas turbine engine flows is preferably covered on the surface with a protective film to prevent oxidation corrosion caused by the exhaust gas. In fact, in the corrugated fin arranged in the flow path through which the combustion exhaust gas of the gas turbine engine flows, an oxidation-corroded layer is formed on the surface as shown in Figures 5(A) and (B). Therefore, in order to prevent oxidation corrosion of the corrugated fin, it was previously necessary to coat the corrugated fin with a protective film before or after joining the corrugated fin to the partition wall 6w.

[0021] Brazing material prevents oxidation and corrosion However, according to research by the inventors of the present invention, it has been found that even when the corrugated fin is exposed to an oxidizing and corrosive gas, oxidation corrosion hardly occurs in the area covered with brazing material. In the micrograph of Fig. 5(A), it is observed that oxidation corrosion does not progress in the area near the top of the corrugated fin joined to the partition wall 6w where the brazing material spreads due to its wettability. Therefore, if the entire surface of the corrugated fin is covered with brazing material in the process of brazing the corrugated fin to the partition wall 6w, oxidation corrosion of the corrugated fin can be prevented without applying a separate protective film.

[0022] Improved manufacturing method for the core part of the heat exchanger according to the present embodiment Based on the above findings, in the present embodiment, in the process of brazing the corrugated fin to the partition wall 6w, a brazing sheet 6m is used that is formed into a wavy shape so as to follow the wavy shape of the corrugated fin 6c, as shown in FIG. 1(A), so that the entire surface of the corrugated fin is covered with the brazing material, and the brazing sheet 6m is laminated on both sides of the corrugated fin 6c as shown by the arrows. In the subsequent manufacturing process, the corrugated fin 6c on which the sheet 6m is laminated is sandwiched between the partition wall 6w as shown in FIG. 1(B) as in the conventional process, and is heated in a vacuum furnace for brazing. The wavy sheet 6m may be used only in the flow path 6b through which oxidative corrosive gas such as combustion exhaust gas of a gas turbine engine flows. In the flow path 6a through which gas that is not likely to be oxidative corrosive such as compressed air of a gas turbine engine flows, a flat brazing sheet 6m may be used as in the conventional process. When heated, the brazing material melts and spreads over the entire surface of the corrugated fin 6c due to its wettability. When the temperature drops, as shown in FIG. 1(C), the top 6t of the corrugated fin 6c is brazed to the partition wall 6w and the entire surface of the corrugated fin 6c is covered with the brazing material.

[0023] Thus, in the conventional core part manufacturing process, in order to prevent oxidation corrosion of the corrugated fins, a separate coating process for the corrugated fins was required, as shown in Figure 2(B). However, according to the above-described embodiment, as shown in Figure 2(A), the coating process for the corrugated fins is no longer necessary in the core part manufacturing process, thereby reducing the number of manufacturing processes.

[0024] The above description has been given in relation to the embodiment of the present invention, but it will be apparent to those skilled in the art that many modifications and changes can be easily made thereto, and that the present invention is not limited to the embodiment exemplified above, but can be applied to various devices without departing from the concept of the present invention.

Claims

[Claim 1] A method for manufacturing a core portion of a heat exchanger in which corrugated fins are disposed between a plurality of plates and tops of the corrugated fins are joined to the plates, comprising the steps of: a step of laminating a brazing sheet made of a brazing material and shaped to conform to the wavy shape of the corrugated fin on the corrugated fin such that the wavy shape of the brazing sheet overlaps the wavy shape of the corrugated fin, and sandwiching the laminate between the plurality of plates; a step of heating the plurality of plates and the laminate sandwiched therebetween to melt the brazing material of the brazing sheet to braze the tops of the corrugated fins to the plates and coat the entire surfaces of the corrugated fins with the brazing material; The method includes:

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