Heat exchanger and method of manufacturing the same

Abstract

In the manufacturing method of a heat exchanger of the present invention, a plate fin includes a brazing material layer on the surface, and is formed by overlapping and brazing brazing sheets having flow path forming areas, so that a refrigerant flow path is formed by the opposing flow path forming areas. In the overlapping brazing sheets, a flow path cross-sectional ratio, which represents the ratio of the flow path cross-sectional area in the joined state after brazing to the unjoined flow path cross-sectional area formed by the flow path forming areas in the unjoined state before brazing, is within a prescribed range, thereby manufacturing a heat exchanger.

Description

Technical Field

[0001] The present invention relates to a heat exchanger, and more particularly to a stacked plate-fin heat exchanger constructed by stacking plate-shaped plate fins having flow paths through which a refrigerant flows, and a method for manufacturing the same. Background Art

[0002] Heat exchangers for exchanging heat energy between fluids having different thermal energies are used in many products. In particular, laminated plate-fin heat exchangers are used in, for example, air conditioners for homes and vehicles, computers, and various electrical devices.

[0003] The stacked plate fin heat exchanger adopts a method of exchanging heat between a fluid (refrigerant) flowing through flow paths formed in plate-shaped plate fins and a fluid (air) flowing between the stacked plate fins.

[0004] In the field of the above-mentioned laminated plate-fin heat exchanger, various structures have been proposed for the purpose of achieving miniaturization and weight reduction and providing a highly reliable product (for example, see Patent Documents 1 to 4).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2012-112562

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 09-001385

[0009] Patent Document 3: Japanese Patent No. 3283471

[0010] Patent Document 4: Japanese Patent No. 5714387 Summary of the Invention

[0011] Problems to be solved by the invention

[0012] In the field of stacked plate-fin heat exchangers, the following research has been conducted. With the goal of achieving lightweighting, miniaturization, and increased efficiency in heat exchange, the plate fins are made thinner using a material with high thermal conductivity, and a fluid (refrigerant) having a higher pressure than that of existing heat exchangers flows through the flow paths formed in the plate fins.

[0013] In order to ensure that high-pressure refrigerant flows through the flow path in a heat exchanger, a structure with a desired flow path cross-section is required to ensure stable refrigerant flow, without causing variations in the refrigerant flow rate and flow velocity. In particular, in stacked plate-fin heat exchangers, which are constructed by brazing multiple plate fins together to form the stacked plate fin structure, ensuring that the refrigerant flow path formed in the plate fins has a desired cross-sectional shape and is stably and reliably formed is a critical issue.

[0014] An object of the present invention is to provide a heat exchanger that is lightweight, compact, and efficient while ensuring that a refrigerant flow path in the heat exchanger has a desired cross-sectional shape and desired pressure resistance and has high reliability.

[0015] The present invention is used to solve the above-mentioned problems, and its purpose is to provide a device with high reliability including a refrigerant flow path and a manufacturing method thereof, in which miniaturization and efficiency are achieved in a stacked plate-fin heat exchanger composed of multiple plate fins joined by brazing, and the refrigerant flow path has a desired cross-sectional shape and desired pressure resistance.

[0016] Methods for solving problems

[0017] In order to achieve the above-mentioned object, a method for manufacturing a heat exchanger according to one embodiment of the present invention is as follows:

[0018] A method for manufacturing a heat exchanger including a plate-fin stack formed by stacking plate fins having refrigerant flow paths with gaps therebetween, wherein

[0019] The plate fins include a brazing material layer on the surface, and brazing sheets having flow path forming areas are overlapped and brazed, so that refrigerant flow paths are formed by the opposing flow path forming areas.

[0020] The heat exchanger is manufactured by ensuring that the flow path cross-sectional area ratio, which represents the ratio of the flow path cross-sectional area in the joined state after brazing to the unjoined flow path cross-sectional area formed by the flow path forming region in the unjoined state before brazing, falls within a predetermined range in the stacked brazing sheets.

[0021] Furthermore, a heat exchanger according to one embodiment of the present invention is a heat exchanger including a plate fin stack in which plate fins having refrigerant flow paths are stacked with gaps therebetween, wherein:

[0022] The plate fin includes a brazing material layer on the surface and includes a refrigerant flow path formed by overlapping and brazing brazing sheets having flow path forming areas.

[0023] In the stacked brazing sheets, a flow path cross-sectional ratio indicating a ratio of a flow path cross-sectional area in a joined state after brazing to an unjoined flow path cross-sectional area formed by a flow path forming region in an unjoined state before brazing has a predetermined range.

[0024] Effects of the Invention

[0025] As described above, the heat exchanger and the manufacturing method thereof according to the present invention can achieve weight reduction, miniaturization and efficiency improvement, while ensuring that the refrigerant flow path in the heat exchanger has the desired cross-sectional shape and the desired pressure resistance, thereby providing a heat exchanger with high reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a perspective view showing the appearance of the stacked plate fin heat exchanger according to the first embodiment of the present invention.

[0027] Figure 2 This is a plan view showing an example of a brazing sheet constituting a plate fin in the heat exchanger according to the first embodiment.

[0028] Figure 3 This is a cross-sectional view of the plate fin stack according to the first embodiment cut along a plane perpendicular to the longitudinal direction thereof.

[0029] Figure 4 This is an enlarged cross-sectional view schematically showing a state before brazing sheets are joined (brazed) in the first embodiment.

[0030] Figure 5 This is a cross-sectional view schematically showing a stacked structure of brazing sheets used in the heat exchanger according to the first embodiment.

[0031] Figure 6 This is a cross-sectional photograph showing a state in which a refrigerant flow path is formed by brazing a brazing sheet.

[0032] Figure 7 It is the Al-Si (aluminum silicon) binary phase diagram.

[0033] Figure 8 This is a cross-sectional photograph showing a state in which molten brazing material penetrates into the core material during brazing.

[0034] Figure 9 This is a cross-sectional photograph showing a specific example of the cross-sectional shape of a refrigerant flow path formed by brazing opposing brazing sheets.

[0035] Figure 10 This is a graph showing calculation results for the refrigerant flow paths formed in the experiment.

[0036] Figure 11This is a graph showing calculation results for the refrigerant flow paths formed in the experiment.

[0037] Figure 12 This is an enlarged cross-sectional view schematically showing a state in which the brazing sheet according to the first embodiment is brazed.

[0038] Figure 13 This is a graph showing the relationship between the "brazing material layer thickness" and the "corrected flow index" in the experimental results.

[0039] Figure 14 This is a graph showing the relationship between the "silicon concentration in the brazing material layer" and the "corrected flow index" in the experimental results.

[0040] Figure 15 This is a graph showing the ranges of "brazing material layer thickness" and "silicon concentration (Si concentration) in the brazing material layer," which are material factors for forming a preferred refrigerant flow path in a heat exchanger according to experimental results. DETAILED DESCRIPTION

[0041] Below, a stacked plate-fin heat exchanger is described with reference to the accompanying drawings as a specific embodiment of the heat exchanger of the present invention. The heat exchanger of the present invention is not limited to the specific stacked plate-fin heat exchanger structure described in the following embodiments, but also includes heat exchangers based on technologies equivalent to those having the technical features described in the following embodiments.

[0042] In addition, the shapes, structures, methods (processes, order of processes), etc. shown in the following embodiments are examples and do not limit the invention to the contents of this disclosure. For the elements in the following embodiments that are not recorded in the independent claims representing the highest concept, they are described as arbitrary elements. In addition, in the drawings, for ease of understanding, each element is schematically depicted as the main body.

[0043] First, various aspects of the heat exchanger and the method for manufacturing the same according to the present invention will be described by way of example.

[0044] A first aspect of the present invention is a method for manufacturing a heat exchanger including a plate-fin stack formed by stacking plate fins having refrigerant flow paths with gaps therebetween, wherein:

[0045] The plate fins include a brazing material layer on the surface, and brazing sheets having flow path forming areas are overlapped and brazed, so that refrigerant flow paths are formed by the opposing flow path forming areas.

[0046] The heat exchanger is manufactured so that the flow path cross-sectional ratio, which represents the ratio of the flow path cross-sectional area in the joined state after brazing to the unjoined flow path cross-sectional area formed by the flow path forming region in the unjoined state before brazing, falls within a predetermined range in the overlapped brazing sheets.

[0047] In the heat exchanger manufacturing method according to a second aspect of the present invention, the flow path cross-sectional ratio in the first aspect may be within a range of 31.0% ≤ R ≤ 81.8%.

[0048] In a third aspect of the heat exchanger manufacturing method of the present invention, the flow path cross-sectional ratio (R) in the first aspect may be within a range of 45.3% ≤ R ≤ 81.8%.

[0049] The fourth aspect of the method for manufacturing a heat exchanger of the present invention is that, in any one of the first to third aspects, the relationship between the thickness of the brazing material layer in the brazing sheet and the silicon concentration of the brazing material layer may have a relationship within a specified selected area, thereby manufacturing a heat exchanger.

[0050] The manufacturing method of the heat exchanger of the fifth embodiment of the present invention is that in any one of the first to third embodiments, it can also be manufactured using a material that represents the thickness of the brazing material layer and the silicon concentration of the brazing material layer selected from a range within a selection area (M) represented by a rough parallelogram in a scatter diagram of a material representing the correlation between the thickness of the brazing material layer in the brazing sheet and the silicon concentration of the brazing material layer.

[0051] A heat exchanger according to a sixth aspect of the present invention is a heat exchanger including a plate-fin stack in which plate fins having refrigerant flow paths are stacked with gaps therebetween.

[0052] The plate fin includes a brazing material layer on the surface and includes a refrigerant flow path formed by overlapping and brazing brazing sheets having flow path forming areas.

[0053] In the stacked brazing sheets, a flow path cross-sectional ratio indicating a ratio of a flow path cross-sectional area in a joined state after brazing to an unjoined flow path cross-sectional area formed by a flow path forming region in an unjoined state before brazing has a predetermined range.

[0054] A heat exchanger according to a seventh aspect of the present invention is characterized in that, in the sixth aspect, the flow path cross-sectional ratio may be within a range of 31.0% ≤ R ≤ 81.8%.

[0055] In the heat exchanger according to an eighth aspect of the present invention, in the sixth aspect, the flow path cross-sectional ratio may be within a range of 45.3% ≤ R ≤ 81.8%.

[0056] A ninth aspect of the present invention is a method for manufacturing a heat exchanger according to any one of the sixth to eighth aspects, wherein the brazing sheet may include a brazing material layer on at least one surface of the core material.

[0057] The core material and the brazing material layer are made of an aluminum alloy, and the brazing material layer is made of an aluminum alloy containing at least silicon.

[0058] A heat exchanger according to a tenth aspect of the present invention is characterized in that, in the ninth aspect, the brazing sheet may include the brazing material layers on both sides of the core material.

[0059] (Implementation 1)

[0060] Hereinafter, a heat exchanger and a method for manufacturing the same according to Embodiment 1 of the present invention will be described with reference to the drawings. Figure 1 1 is a perspective view showing the appearance of a stacked plate fin heat exchanger (hereinafter referred to as a heat exchanger) 1 according to Embodiment 1. Figure 1 As shown, the heat exchanger 1 of embodiment 1 includes: a feed pipe 4 for supplying a refrigerant as a first fluid A; a plate fin stack 2 formed by stacking a plurality of rectangular plate fins 2a with gaps therebetween; and a discharge pipe 5 for discharging the refrigerant flowing in the refrigerant flow path formed on the plate fins 2a.

[0061] In the heat exchanger 1 of embodiment 1, the feed pipe 4 and the discharge pipe 5 have substantially the same structure, and the functions corresponding to the operation at this time are used as names. In addition, in the present invention, the feed pipe 4 and the discharge pipe 5 are collectively referred to as a sleeve (4, 5).

[0062] In the stacking direction of the plate fin stack 2 ( Figure 1 The heat exchanger 1 shown in the figure is provided with end plates 3 at both ends thereof. The end plates 3 are Figure 1 The heat exchanger 1 shown in FIG. 1 has a substantially rectangular plate fin 2a (as viewed from above). A feed pipe 4 or a discharge pipe 5 is joined to both ends of one end plate 3 in the longitudinal direction. While the first embodiment describes a configuration in which the feed pipe 4 or the discharge pipe 5 is joined to each end of one end plate 3, a configuration in which the feed pipe 4 is joined to one end plate 3 and the discharge pipe 5 is joined to the other end plate 3 may also be employed, depending on the specifications of the device in which the heat exchanger 1 is used.

[0063] In addition, in the following embodiment 1, Figure 1The stacking direction of the plate-fin stack 2 in the heat exchanger 1 shown is described as the vertical direction, with the position of one end plate 3 provided on the plate-fin stack 2 being the upper side and the position of the other end plate 3 being the lower side. However, when the heat exchanger 1 is installed in a device (e.g., an air conditioner), the stacking direction is not specifically the vertical direction (the vertical direction).

[0064] End plates 3, located at both ends of the plate-fin stack 2 in the stacking direction, are secured to each other at a predetermined distance using a positioning mechanism (e.g., positioning bolts) and sandwich the plate-fin stack 2. The positioning mechanism, which secures the end plates 3 at the predetermined distance, functions to position the stacked plate fins 2a. The end plates 3 can be formed of sheet metal made of a metal material such as aluminum, an aluminum alloy, or stainless steel, or they can be formed by stacking brazing sheets (described later).

[0065] In the heat exchanger 1 of the first embodiment, the refrigerant as the first fluid A flows through the refrigerant flow path 60 (see FIG. 1 ) formed by the flow path forming area 13 formed on each plate fin 2a of the plate fin stack 2. Figure 3 ). Meanwhile, a structure is adopted in which air, which is the second fluid B, passes through gaps formed between the stacked plate fins 2a in the plate fin stack 2. In the heat exchanger 1 thus constructed, heat exchange occurs between the first fluid A and the second fluid B in the plate fin stack 2.

[0066] The plurality of plate fins 2a constituting the plate-fin stack 2 in the heat exchanger 1 of Embodiment 1 are each formed by closely adhering and joining (brazing) two brazing sheets (first fin member 10 and second fin member 20) in an opposing manner to form a refrigerant flow path 60. The plate fins 2a thus constructed are stacked, pressurized, heated, and then joined (brazed) to form the plate-fin stack 2. Alternatively, the heat exchanger may be manufactured by simultaneously heating and joining (brazing) the end plates 3 and sleeves 4 and 5 while the plate-fin stack 2 is being heated and joined.

[0067] Figure 2 The brazing sheet 50 constituting the plate fin 2a (see Figure 4 ) is a plan view of an example of the first fin member 10 and the second fin member 20. Figure 2In the figure, (a) is a plan view of the first fin member 10, and (b) is a plan view of the second fin member 20. The first fin member 10 and the second fin member 20 are thin plates made of aluminum alloy, and their detailed structures will be described later. The first fin member 10 and the second fin member 20 are processed into a predetermined shape using a thin plate of a brazing sheet 50. The first fin member 10 and the second fin member 20 processed into the predetermined shape are arranged relative to each other at a predetermined position and pressurized and heated in a manner that they are in close contact with each other, thereby reliably joining (brazing) the relative flat predetermined areas to each other.

[0068] exist Figure 2 In the first fin member 10 shown in (a), recessed portions of an annular header flow path 11 for supplying refrigerant from the feed pipe 4 or discharging refrigerant to the discharge pipe 5 are formed at both ends in the longitudinal direction. A header communication flow path 12 extending from one point on the outer periphery of the header flow path 11 by a predetermined distance is formed. The end of a flow path forming region 13 formed in the heat exchange region of the plate fin 2a is arranged on an extension of the header communication flow path 12 in the direction of its extension.

[0069] The flow path forming region 13 in the first fin member 10 is formed by a recessed portion, similar to the header communication flow path 12. The flow path forming region 13 is formed so as to meander throughout the entire heat exchange region of the plate fin 2a. The configurations of the header flow path 11, header communication flow path 12, and flow path forming region 13 in the first embodiment are merely examples, and the present invention is not particularly limited to these examples.

[0070] In the structure of the first embodiment, the second fin member 20 joined (brazed) to the first fin member 10 is formed as follows. Figure 2 As shown in (b), flow path forming regions 21 and 22 are formed. In the first embodiment, by joining (brazing) the first fin member 10 and the second fin member 20, the flow path forming region 13 forms a refrigerant flow path 60 that communicates from the header flow path 11 via the communication flow path 12. As a result, in the heat exchanger 1 of the first embodiment, the refrigerant supplied from the feed pipe 4 flows through the header flow path 11, the header communication flow path 12, the flow path forming region 21, the flow path forming region 13 (the flow path forming region 22), the flow path forming region 21, the header communication flow path 12, and the header flow path 11, and is discharged from the discharge pipe 5.

[0071] like Figure 2As shown in (b), in the second fin member 20, a flow path forming area 22 is formed in an area opposite to the linear flow path forming area 13 in the first fin member 10. The flow path forming area 22 is a convex area that protrudes in the same direction as the flow path forming area 13, and its protruding height is lower than that of the flow path forming area 13. By arranging the flow path forming area 22 opposite to the linear flow path forming area 13 of the first fin member 10, the refrigerant flow path 60 is ensured in the linear portion of the flow path forming area 13, and deformation of the cross-sectional shape perpendicular to the flow direction of the refrigerant is suppressed.

[0072] Furthermore, the heat transfer blocking slits 6 are formed in the first fin member 10 and the second fin member 20 to suppress heat transfer between the adjacent flow path forming regions 13 and improve heat exchange efficiency.

[0073] Figure 3 This is a cross-sectional view of the plate fin stack 2 in the first embodiment cut along a plane perpendicular to its longitudinal direction. Figure 3 Schematically shows a state in which the first fin member 10 and the second fin member 20 are joined (brazed) and the refrigerant flow path 60 is formed by the flow path forming region 13 of the first fin member 10 and the flow path forming region 22 of the second fin member 20 . Figure 4 1 is an enlarged cross-sectional view schematically showing a state before the first fin member 10 and the second fin member 20 are joined (brazed). Figure 4 As shown, a three-layer brazing sheet 50 having brazing material layers (52, 53) formed on both sides of a core material 51 is used as the first fin member 10 and the second fin member 20 in Embodiment 1. Alternatively, as described later, a four-layer brazing sheet 50 having a sacrificial material layer formed on one side of the core material 51 may be used in the plate fin stack 2.

[0074] Brazing Sheet

[0075] Figure 5 This is a cross-sectional view schematically showing a stacked structure of brazing sheets 50 used as the first fin members 10 and the second fin members 20 in the heat exchanger 1 according to the first embodiment. Figure 5 (a) shows a brazing sheet 50a having a three-layer structure, and (b) shows a brazing sheet 50b having a four-layer structure.

[0076] Figure 5 The three-layer brazing sheet 50a shown in (a) has a structure in which aluminum alloy layers are laminated, and adopts a three-layer structure in which a first brazing material layer 52 and a second brazing material layer 53 are laminated on both sides of a core material 51. As a specific example of the three-layer brazing sheet 50a, for example, the core material 51 is an aluminum alloy containing manganese (Mn), and the first brazing material layer 52 and the second brazing material layer 53 are aluminum alloys containing silicon (Si).

[0077] Representative materials for the core material 51 include, but are not limited to, 3000 series (aluminum-manganese (Al-Mn) alloys), 5000 series (aluminum-magnesium (Al-Mg) alloys), and 6000 series (aluminum-magnesium-silicon (Al-Mg-Si) alloys). The core material 51 of the brazing sheet 50 (50a, 50b) of the present invention may be any aluminum alloy capable of achieving the physical properties determined according to various conditions, such as the type and structure of the heat exchanger.

[0078] The first brazing material layer 52 and the second brazing material layer 53 may be an aluminum alloy containing silicon (Si) used as a brazing material, that is, any aluminum-silicon (Al-Si) alloy. Furthermore, Al-Si alloys used as brazing materials may contain elements other than Si, as long as they do not affect the brazing material's function. Furthermore, Al-Si alloys used as brazing materials may contain various elements as unavoidable impurities.

[0079] in addition, Figure 5 The four-layer brazing sheet 50b shown in (b) has a structure in which aluminum alloy layers are laminated, similar to the three-layer brazing sheet 50a, but a sacrificial material layer 54 is formed on one surface of the core material 51 between the first brazing material layer 52. The sacrificial material layer 54 covers one surface of the core material 51, and the second brazing material layer 53 covers the other surface of the core material 51, that is, the surface opposite to the surface covered by the sacrificial material layer 54. The material of the sacrificial material layer 54 is the same aluminum alloy as the core material 51, the first brazing material layer 52, and the second brazing material layer 53, which is an aluminum alloy containing zinc (Zn).

[0080] To achieve a sacrificial corrosion protection effect, the aluminum alloy used as the material for the sacrificial material layer 54 contains zinc (Zn). Furthermore, the material for the sacrificial material layer 54 may contain elements other than Zn, as long as the sacrificial corrosion protection effect is not affected. Furthermore, the Al-Zn alloy used as the material for the sacrificial material layer 54 may contain various elements as unavoidable impurities.

[0081] In manufacturing the heat exchanger of Embodiment 1, the first fin member 10 and the second fin member 20, each formed using brazing sheets 50 made of the above-mentioned material, are stacked and brazed in a high-temperature furnace (580°C or higher) to form a refrigerant flow path. The plate-fin stack 2 thus manufactured is used in the heat exchanger 1 of Embodiment 1.

[0082] Figure 6 1 is a cross-sectional photograph showing a state in which the first fin member 10 and the second fin member 20 are brazed to form the refrigerant flow path 60. Figure 6 The cross-sectional photograph shows the above Figure 4 The illustrated embodiment shows a specific example of a state in which the first fin member 10 and the second fin member 20 stacked together are brazed at a high temperature. Figure 6 The refrigerant flow path 60 shown in the cross-sectional photograph has a desired flow path cross section. The second brazing material layer 53 of the first fin member 10 and the first brazing material layer 52 of the second fin member 20 arranged opposite to each other are melted and joined to form the desired refrigerant flow path 60.

[0083] like Figure 6 As shown in the cross-sectional photograph of , in the region between the core material 51 of the first fin member 10 and the core material 51 of the second fin member 20, the brazing material layers (53, 52) melt to form a fillet (joint portion) 61. The fillet (joint portion 61) is formed by the second brazing material layer 53 of the first fin member 10 and the first brazing material layer 52 of the second fin member 20 being melted by heating to a predetermined high temperature before brazing, and condensing in the joining region 61a of the first fin member 10 and the second fin member 20 and the flow path forming region 61b on both sides of the refrigerant flow path 60, thereby brazing and joining the first fin member 10 and the second fin member 20. Regarding the melting amount of the brazing material layer (53, 52) during brazing at this time, the amount (shape and size) of the fillet (joint portion) 61, that is, the joining amount (shape and size) of the joining area 61a and the flow path forming area 61b, is determined based on the melting amount (actual melting amount) reduced by the immersion amount (thinning amount) of each core material 51.

[0084] The joint strength (pressure resistance) of the brazed first fin member 10 and second fin member 20 is affected by the amount (shape and size) of the fillet (joint portion) 61. Failure to ensure a certain amount of fillet 61 may lead to damage during use of the plate-fin stack 2, refrigerant leakage, etc. Furthermore, if the flow path forming region 61b forming the refrigerant flow path 60 does not have the desired flow path cross-sectional shape, there is a problem in that the specified heat exchange capacity cannot be maintained.

[0085] As described above, by brazing the first fin member 10 and the second fin member 20, the first fin member 10 and the second fin member 20 have the expected bonding strength (pressure resistance), and there are at least the following factors as factors affecting the refrigerant flow path to be formed into the desired flow path cross-sectional shape.

[0086] (1) The thickness of the brazing material layer as a material factor;

[0087] (2) Silicon concentration (Si concentration) in the brazing material layer as a material factor;

[0088] (3) Brazing temperature as a conditioning factor; and

[0089] (4) Brazing time as a conditional factor.

[0090] Among the above-mentioned influencing factors, (1) to (3) determine the melting amount of the brazing material layer, and (4) determines the penetration amount (thinning amount) into the core material 51 .

[0091] <Si Diffusion During Brazing>

[0092] Figure 7 This is the Al-Si (aluminum silicon) binary phase diagram, where the vertical axis represents temperature T [°C] and the horizontal axis represents Si concentration [%. Figure 7 In the binary phase diagram shown, the eutectic temperature, which represents the eutectic isotherm, is 577°C, and the two-phase coexistence region indicates a Si concentration of 1.6 to 12.1%. Furthermore, the Al liquidus temperature when the Si concentration is 0% is 660°C.

[0093] like Figure 7 As shown in the phase diagram, the liquid phase ratio σ at a specific temperature T is basically determined by the Si concentration [Si] in the aluminum alloy. Therefore, the amount of brazing material layer (53, 52) melted during brazing can be determined by the "thickness of the brazing material layer," "the Si concentration in the brazing material layer," and "the brazing temperature." However, during brazing, since some of the Si atoms in the brazing material layer diffuse into the core material 51, the entire amount of brazing material in the brazing material layer is not formed in the fillet (joint) 61.

[0094] As described above, during brazing, Si atoms in the brazing material layer diffuse into the core material 51. Therefore, the amount of Si in the brazing material layer used to form the fillet (joint portion) 61 is reduced compared to the calculated value based on the Si concentration specified in the alloy material manufacturing process specifications. In other words, the liquid phase ratio σ, which determines the amount of melt in the brazing material layer during brazing, is smaller than the calculated liquid phase ratio based on the Si concentration specified in the manufacturing process specifications.

[0095] Therefore, if the Si diffusion amount during brazing can be quantified, the actual liquid phase ratio σ can be accurately calculated. However, the Si diffusion amount has large variations in practice, making quantification difficult based on experimental values.

[0096] Therefore, in the present invention, the Si diffusion amount is simplified and modeled based on the diffusion theory, thereby being able to calculate the melting amount of the brazing material layer by brazing using the actual liquid phase ratio (corrected liquid phase ratio) σ2 taking into account the influence of Si diffusion during brazing.

[0097] Simplified Modeling of Si Diffusion Amount

[0098] Next, the idea of ​​simplifying the modeling of the change in the liquid phase ratio σ due to Si diffusion during brazing will be described.

[0099] according to Figure 7 In the binary phase diagram shown, the change in the liquid phase ratio σ based on the Si concentration [Si] is expressed by a linear equation of the Si concentration [Si] shown in the following formula [1].

[0100]

[0101] As shown in the above formula [1], since the change in the liquid phase ratio σ is expressed by the linear equation of the Si concentration [Si], it is considered that the change in the liquid phase ratio σ due to Si diffusion during brazing can also be expressed by the linear equation of the Si concentration [Si].

[0102] The inventors' experiments confirmed that the Si diffusion amount during brazing is related to the "square root of the brazing time (√t1)", "diffusion coefficient (D)" and "Si concentration gradient between the core material and the brazing material layer (C b -C c )”. Therefore, the actual liquid phase ratio (corrected liquid phase ratio) σ2 during brazing taking into account Si diffusion can be expressed by the following formula [2].

[0103]

[0104] In the above formula [2], “K1” is the coefficient used for fitting, “D” represents the diffusion coefficient, and “C b ” represents the Si concentration in the brazing material layer, “C c " represents the Si concentration in the core material, and "t1" represents the brazing time.

[0105] Based on the above research results, the inventors found that the actual amount of melt formed during brazing (actual melt amount) can be calculated by multiplying the "thickness of the brazing material layer" by the "corrected liquid phase ratio σ2" (see the following formula [3]).

[0106] “Actual melting amount” = “Thickness of brazing material layer” × “Corrected liquid phase ratio σ2”

[0107] ———[3]

[0108] 〈Thinning reduction during brazing〉

[0109] As described above, during brazing, the brazing material layer melts to form the fillet (joint) 61. The amount of brazing material used to form this fillet (joint) 61 is the amount of brazing material melted, minus the amount of penetration (thinning) into the core material 51 from the amount of brazing material melted. This amount of brazing material determines the amount (shape and size) of fillet (joint) 61, specifically the amount (shape and size) of the joining region 61a and the flow path forming region 61b.

[0110] Figure 8 This is a cross-sectional photograph showing the state in which the molten brazing material penetrates into the interior of the core material 51 during brazing. Figure 6 The cross-sectional photograph shown in FIG. 1 shows a state in which fillets (joint portions) are formed between the core materials 51 by the molten brazing material and the brazing sheets 50 are reliably joined to each other. Figure 8 As can be seen from the cross-sectional photograph, the molten brazing material penetrates into the interior of each core material 51 , thereby reducing the bonding strength between the brazing sheets 50 .

[0111] Figure 8 The state shown in the cross-sectional photograph of shows a state in which the brazing time exceeds the prescribed time and becomes longer. In this state, the molten brazing material gradually penetrates into the interior of the core material 51. In this way, if the brazing material penetrates the core material 51, the bonding strength decreases accordingly depending on the portion of the brazing material that has penetrated (the amount of thinning), that is, the portion that has been reduced.

[0112] It can be seen that the amount of thinning caused by the brazing material invading the core material 51 during brazing is closely related to the "brazing time". The "thinning amount" is proportional to the square root of the "brazing time". Therefore, the relationship between "thinning amount" and "brazing time" can be expressed by the following formula [4].

[0113] “Thinning amount” ∝ “square root of brazing time” — [4]

[0114] Modified flow index F2

[0115] Next, the "corrected flow index F2," defined by taking into account the "actual amount of melt" from the brazing material layer during brazing and the aforementioned "thinning amount," will be explained. The "corrected flow index F2" is a numerical value that indicates the ability to form a refrigerant flow path 60 with a desired flow path cross-section and to ensure a predetermined joint strength (pressure resistance) between the opposing brazing sheets 50 to be joined. The "corrected flow index F2" is defined as shown in the following formula [5].

[0116] "Corrected flow index F2" = "actual melting amount" × "thinning amount"

[0117] = "Thickness of brazing material layer" × "corrected liquid phase ratio σ2"

[0118] × “Square root of brazing time” — [5]

[0119] As described above, the "corrected flow index F2" is an indicator of the influencing factors added to brazing, such as the above-mentioned (1) "thickness of the brazing material layer" as a material factor, (2) "silicon concentration (Si concentration) in the brazing material layer" as a material factor, (3) "brazing temperature" as a conditional factor, and (4) "brazing time" as a conditional factor.

[0120] Therefore, by determining the "corrected flow index F2" when the specified bonding strength (pressure resistance) is ensured between the relative brazing sheets 50 to be joined and the refrigerant flow path 60 with the desired flow path cross-section is formed, the range of the "thickness of the brazing material layer" and the "silicon concentration (Si concentration) in the brazing material layer" as the desired material factors during brazing can be determined.

[0121] Figure 9 This is a cross-sectional photograph showing the specific shape of the flow path cross section of the refrigerant flow path 60 formed by brazing opposing brazing sheets 50. The flow path cross section refers to a cross section taken in a direction perpendicular to the direction of refrigerant flow in the refrigerant flow path 60.

[0122] Figure 9 (a) shows a case where the flow path cross section of the refrigerant flow path 60 has a desired shape, and is a cross-sectional photograph showing a shape similar to a substantially mountain-shaped shape which is an ideal shape in design. Figure 9 (b) shows that the flow path cross section is substantially elliptical, the actual melting amount is large, and the area occupied by the rounded corners (joint portion) is increased, the joint strength (pressure resistance) is increased, but the flow path cross section of the refrigerant flow path 60 becomes smaller. Figure 9 (c) shows that the actual melting amount is further increased, the area occupied by the fillet (joint portion) is further increased, and the flow path cross section of the refrigerant flow path 60 becomes a small circular shape. Figure 9 (d) shows that the refrigerant flow path 60 between the brazing sheets 50 is clogged, and is in a flow path blocked state.

[0123] The inventors conducted various brazing experiments under varying conditions during the manufacture of the plate-fin stack 2 of the heat exchanger 1 and obtained the following experimental results.

[0124] <Relationship between the cross-sectional shape and cross-sectional area of ​​the refrigerant flow path>

[0125] In various brazing experiments, the flow path cross-sectional area S of the refrigerant flow path 60 formed was measured as a specific experimental result. Figure 4 As shown in FIG. 1 , the designed unbonded cross-sectional area Sa of the brazing sheets 50 disposed opposite to each other in the unbonded state is 203000 μm2 .

[0126] exist Figure 9 In the case of the substantially mountain-shaped shape shown in (a), which is an ideal shape in design, the flow path cross-sectional area S is 92000 μm 2 ≤S≤166000μm 2 range.

[0127] exist Figure 9 In the case of the substantially elliptical shape shown in (b), the flow path cross-sectional area S is 63000 μm 2 ≤S≤92000μm 2 range.

[0128] exist Figure 9 In the case of the small circular shape shown in (c), the flow path cross-sectional area S is S<63000 μm 2 .

[0129] According to the above experimental results, in order to ensure the specified refrigerant flow rate and refrigerant flow rate in the refrigerant flow path 60 formed by brazing, the preferred flow path cross-sectional shape is Figure 9 The shape shown in (a) is shown in FIG. In addition, the range of the flow path cross-sectional area S allowed as the flow path cross-sectional shape is 63000 μm 2 ≤S≤166000μm 2 range.

[0130] In the present invention, in order to standardize the refrigerant flow path formation, the flow path cross-sectional area S and the unjoined cross-sectional area Sa formed by the flow path forming regions (13, 21, 22) in the unjoined state before brazing are used (see Figure 4 ), namely, the flow path cross-sectional area ratio R. Specifically, the refrigerant flow path 60 is brazed so that the flow path cross-sectional area ratio (R), which represents the ratio of the flow path cross-sectional area (S) in the brazed state to the unbrazed flow path cross-sectional area (Sa), falls within a specified range. A preferred flow path cross-sectional shape can have a flow path cross-sectional area ratio R in the range of 45.3% ≤ R ≤ 81.8%. Alternatively, an acceptable flow path cross-sectional shape can have a flow path cross-sectional area ratio R in the range of 31.0% ≤ R ≤ 81.8%.

[0131] Figure 10 and Figure 11 Graph showing the calculation results of the refrigerant flow path 60 formed in the above-mentioned "corrected flow index F2" experiment. Figure 10 In the figure, the horizontal axis represents the "corrected flow index F2" and the vertical axis represents the "flow path cross-sectional area S [μm 2 ]".exist Figure 11 In the figure, the horizontal axis represents the "corrected flow index F2" and the vertical axis represents the "joint cross-sectional area J [μm2 ]”. Figure 12 : is an enlarged cross-sectional view schematically showing a state where the first fin member 10 and the second fin member 20 are joined (brazed). Figure 12 In the cross-sectional view shown in FIG. 1 , “S” represents the cross-sectional area of ​​the refrigerant flow path 60, i.e., the flow path cross-sectional area. Figure 4 In the cross-sectional view of the state before joining (brazing) shown in FIG, the unjoined cross-sectional area Sa of the refrigerant flow path is subtracted from the Figure 12 1 / 2 of the value obtained by taking the flow path cross-sectional area S shown. That is, it can be expressed as [joined cross-sectional area J = (unjoined cross-sectional area Sa - flow path cross-sectional area S) / 2]. This is because after brazing (joining), a joint area (rounded corners) with a roughly triangular cross-section is formed on both sides of the refrigerant flow path 60. Figure 12 In the cross-sectional view, the joint cross-sectional area J is indicated by cross-hatching.

[0132] exist Figure 10 In the graph of , when the flow path cross-sectional area S is within the allowed range and the refrigerant flow path 60 formed shows a preferred bonding strength (pressure resistance), it is indicated by "○". Figure 10 In the figure, a case where the flow cross-sectional area S of the formed refrigerant flow path 60 exceeds the allowable range is indicated by a thin × symbol, and a case where the bonding strength (pressure resistance) of the formed refrigerant flow path 60 is below the specified value is indicated by a thick × symbol. Figure 10 The dashed curve in is the approximation curve.

[0133] In order to ensure the required heat exchange capacity in the refrigerant flow path 60 of the heat exchanger, as described above, the flow path cross-sectional ratio R, which is the allowable flow path cross-sectional shape, must be within the range of 31.0% ≤ R ≤ 81.8%. Therefore, according to the experimental results of the inventors, the preferred range of the modified flow index F2 is "366" or less. Figure 10 In the graph shown, the arrows below the dot-dash line indicate the region (F2≤366).

[0134] In addition, Figure 11 In the graph, when the formed refrigerant flow path 60 has a preferred bonding strength (pressure resistance) and has a flow path cross-sectional area S within the allowed range, it is represented by "○". Figure 11 In the figure, when the bonding strength (pressure resistance) of the formed refrigerant flow path 60 is below the specified value, it is indicated by a thick × mark, and when the flow path cross-sectional area S of the formed refrigerant flow path 60 exceeds the allowable range, it is indicated by a thin × symbol. Figure 11 The middle dashed curve is the approximation curve.

[0135] like Figure 11 As shown in the curve diagram, if calculated based on the experimental results of the inventor, the preferred range of the modified flow index F2 is "130" or above. Figure 11 In the graph shown, the arrows indicate the region above the dot-dash line (130 ≤ F2).

[0136] Therefore, regarding the flow path cross-sectional area S and the joint area J of the refrigerant flow path 60 , if the modified flow index F2 is used as an index, the range of the following inequality is achieved.

[0137] 130≤F2≤366———[6]

[0138] The inventors found that by deriving the above-mentioned inequality [6], it is possible to specify the ranges of the material factors "brazing material layer thickness" and "silicon concentration (Si concentration) in the brazing material layer" that satisfy inequality [6].

[0139] Figure 13 The vertical axis represents the "thickness of the brazing material layer [mm]", and the horizontal axis represents the "corrected flow index F2". Figure 14 The vertical axis represents "Si concentration [%]", and the horizontal axis represents "corrected flow index F2". Figure 13 and Figure 14 In the curve diagram, the above Figure 10 and Figure 11 Similarly, "○" is used to indicate that the flow path cross-sectional area S is within the allowable range and the formed refrigerant flow path 60 has a preferred bonding strength (pressure resistance performance). A thin × symbol is used to indicate that the flow path cross-sectional area S exceeds the allowable range, and a thick × symbol is used to indicate that the bonding strength (pressure resistance performance) is below the specified value. Figure 13 and Figure 14 In the curve diagram, the area between the two dot-dashed lines becomes the preferred area in the modified flow index F2.

[0140] Figure 15 This is a graph showing the areas of "thickness of the brazing material layer" and "silicon concentration (Si concentration) in the brazing material layer", which are material factors for forming a preferred refrigerant flow path 60 in the manufacture of the heat exchanger 1. Figure 15 In the figure, the vertical axis represents the thickness of the solder material layer [mm], and the horizontal axis represents the silicon concentration (Si concentration) in the solder material layer. Figure 15 In the graph, the area surrounded by a substantially parallelogram represents a selection area M of material factors ("brazing material layer thickness" and "silicon concentration (Si concentration) in the brazing material layer") for forming a preferred refrigerant flow path 60. If within this selection area M, Figure 15As shown in the cross-sectional photograph (a) of FIG, the refrigerant flow path 60 becomes the desired flow path cross-sectional shape. Figure 15 In the case of a selection area M outside the substantially parallelogram shown in the graph, as shown in FIG. Figure 15 As shown in the cross-sectional photograph (b) of FIG, the refrigerant flow path 60 is in a closed shape that does not satisfy the prescribed flow path cross-sectional area, or as shown in FIG. Figure 15 As shown in the cross-sectional photograph (c), the joint surface is small and the joint strength (pressure resistance) does not meet the prescribed strength.

[0141] Then, in Figure 15 In the graph of , the reason why the selection area M is in the shape of a roughly parallelogram descending toward the lower right direction is explained.

[0142] First, the reason why the lower two sides (the first boundary line L1 and the second boundary line L2 ) of the substantially parallelogram representing the selected area M fall downward to the right is based on the following reason.

[0143] The first boundary line L1 and the second boundary line L2 in the selected area M are the lower limit lines for the bonding strength (pressure resistance). In order to ensure the specified bonding strength, it is necessary to ensure that a certain amount of brazing material is melted. As mentioned above, if the thickness of the brazing material is thick and the Si concentration in the brazing material layer is high, the melting amount of the brazing material increases. That is, in order to ensure that a certain amount of brazing material is melted, the Si concentration in the brazing material layer needs to be increased when the brazing material layer is thin, and conversely, when the brazing material layer is thick, the Si concentration in the brazing material layer needs to be reduced. As a result, Figure 15 In the graph shown, the first boundary line L1 and the second boundary line L2 , which are the lower sides of the selected area M, are lines that descend toward the lower right direction.

[0144] Next, the reason why the upper two sides (the third boundary line L3 and the fourth boundary line L4 ) of the substantially parallelogram representing the selected area M fall downward to the right is based on the following reason.

[0145] The third boundary line L3 and the fourth boundary line L4 in the selected area M are the lower limit lines of the flow path cross section of the refrigerant flow path 60. In order to ensure the specified flow path cross section, the melting amount of the brazing material is required to be less than a certain amount. As mentioned above, if the thickness of the brazing material layer is thick and the Si concentration in the brazing material layer is high, the melting amount of the brazing material increases. That is, in order to ensure the melting amount of the brazing material is more than a certain amount, when the thickness of the brazing material layer is thin, the Si concentration in the brazing material layer needs to be increased, and conversely, when the thickness of the brazing material layer is thick, the Si concentration in the brazing material layer needs to be reduced. As a result, Figure 15In the graph shown, the third boundary line L3 and the fourth boundary line L4 , which are both upper sides of the selected area M, are lines descending toward the lower right direction.

[0146] As described above, it can be understood that in the manufacture of the heat exchanger of the first embodiment, in order to form the desired refrigerant flow path 60 by overlapping and brazing the specific brazing sheets 50, Figure 15 By selecting the “solder material layer thickness” and / or the “silicon concentration (Si concentration) in the solder material layer” as material factors within the selected region M in the graph of , manufacturing can be performed.

[0147] In the structure described in the first embodiment, the range enclosed by the first boundary line L1, the second boundary line L2, the third boundary line L3, and the fourth boundary line L4 defining the selected region M can be expressed by the following inequalities [7], [8], [9], and

[10] . In inequalities [7], [8], [9], and

[10] , it is assumed that the thickness of the brazing material layer is "y" and the Si concentration in the brazing material layer is "x."

[0148]

[0149]

[0150]

[0151]

[0152] In the first embodiment, the interior of the parallelogram of the selected region M is determined to be within a range that satisfies all of the above-mentioned inequalities [7], [8], [9], and

[10] . Within the range of the selected region M, the refrigerant flow path 60 formed in the plate fin 2a has a desired cross-sectional shape, and a highly reliable heat exchanger can be constructed in which the plate fin 2a is brazed with a desired bonding strength (pressure resistance).

[0153] In addition, in the first embodiment, the brazing sheet 50 is described as including brazing material layers 52 and 53 on both sides of the core material 51. However, the brazing material layer may also function as a sacrificial anti-corrosion layer, and an aluminum alloy layer containing silicon (Si) and zinc (Zn) may be formed on one side of the core material 51. In addition, the sacrificial anti-corrosion layer may contain elements other than Zn within a range that does not affect the sacrificial anti-corrosion function. In addition, various elements may be contained as unavoidable impurities.

[0154] As described above, as detailed in Embodiment 1, the heat exchanger of the present invention utilizes a plate-fin stack formed by stacking brazing sheets. This structured heat exchanger can provide a heat exchanger in which the refrigerant flow path formed in the plate-fin stack has a desired cross-sectional shape, and the individual plate fins are brazed with a desired joint strength (pressure resistance), thereby preventing refrigerant leakage at the joints. As a result, the heat exchanger and its manufacturing method of the present invention achieve lightweighting, miniaturization, and improved efficiency while ensuring the refrigerant flow path in the heat exchanger has the desired cross-sectional shape and desired pressure resistance, thereby providing a highly reliable heat exchanger.

[0155] While the present invention has been described in detail in the embodiments, these structures are examples and the disclosure of the embodiments may vary in structural details. The present invention may incorporate substitutions, combinations, and changes in order of elements in the embodiments without departing from the scope of the claims and the spirit of the present invention.

[0156] Industrial applicability

[0157] The heat exchanger of the present invention can be made compact and lightweight, and can reliably have a desired cross-sectional shape and desired pressure resistance. Therefore, the heat exchanger can be used in various products, and can provide products with high market value.

[0158] Description of Reference Numerals

[0159] 1 Heat exchanger

[0160] 2 Plate fin stack

[0161] 2a Plate fin

[0162] 3 End plates

[0163] 4 Feed pipe

[0164] 5 Discharge pipe

[0165] 6 Heat transfer blocking slits

[0166] 12 Manifold connecting flow path

[0167] 13 Flow path formation area

[0168] 21, 22 Flow path formation area

[0169] 50 brazing sheet

[0170] 51 core material

[0171] 52 1st brazing material layer

[0172] 53 second brazing material layer

[0173] 54 sacrificial material layer

[0174] 60 Refrigerant flow path

[0175] 61 fillet (joint)

[0176] 61a Junction area

[0177] 61b Flow path formation area.

Claims

1. A method for manufacturing a heat exchanger comprising a plate-fin stack formed by stacking plate fins having refrigerant flow paths with gaps therebetween, the method comprising: A plurality of brazing sheets including a brazing material layer on the surface and having a flow path forming area are selected. The plate fin is formed by overlapping and brazing a plurality of selected brazing sheets, so that a refrigerant flow path is formed in the opposing flow path forming areas. The overlapping brazing sheets are arranged such that a flow path cross-sectional ratio, which represents a ratio of a flow path cross-sectional area in a joined state after brazing to an unjoined flow path cross-sectional area formed by a flow path forming region in an unjoined state before brazing, is within a range of 45.3% ≤ R ≤ 81.8%. The brazing sheet is selected by selecting a brazing sheet that satisfies the relationship between the thickness of the brazing material layer and the silicon concentration of the brazing material layer within a selection area indicated by a substantially parallelogram, from a scatter diagram of a material showing the correlation between the thickness of the brazing material layer and the silicon concentration of the brazing material layer. in, The selected region is the region enclosed by the inequalities of Formulas 1, 2, 3, and 4 when the silicon concentration (wt%) of the brazing material layer is x and the thickness (mm) of the brazing material layer is y.

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