heat exchanger

Abstract

To suppress the deterioration of heat exchanger performance. [Solution] The economizer 10, which is a heat exchanger, has a three-dimensional shape formed by heat transfer walls 23 whose outer shape is defined by at least one of a pair of parallel curved surfaces and planes, with the unit structure 24 being a unit structure 24 comprising a three-dimensional structure 20 arranged regularly and continuously in the XYZ directions, and heat transfer tubes 25 embedded in the three-dimensional structure 20. The three-dimensional structure 20 and the heat transfer tubes 25 are integrally and inseparably formed with the heat transfer walls 23 fused to the outer surface of the heat transfer tubes 25. Combustion gas G2, which is a first fluid, is brought into contact with both sides of the heat transfer walls 23, and water W, which is a second fluid, is circulated through the heat transfer tubes 25.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a heat exchanger.

Background Art

[0002] In the technical field related to heat exchangers, a gas liquefaction device as disclosed in Patent Document 1 is known. In Patent Document 1, the gas liquefaction device includes a spiral pipe-shaped refrigerant flow path in which a refrigerant flows and a heat-conductive partition wall is provided, and a heat-conductive porous body joined to the partition wall so as to be heat-exchangeable.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When foreign matter accumulates in the flow path of a heat exchanger through which a fluid flows, it may become difficult for the fluid to flow or the heat exchange efficiency may decrease, resulting in a possible decrease in the performance of the heat exchanger.

[0005] The technology disclosed in this specification aims to suppress a decrease in the performance of a heat exchanger.

Means for Solving the Problems

[0006] This specification discloses a heat exchanger. The heat exchanger has a three-dimensional structure formed by a heat transfer wall whose outer shape is defined by at least one of a pair of parallel curved surfaces and flat surfaces as a unit structure body, and the unit structure body includes a three-dimensional structure regularly and continuously repeatedly arranged in the XYZ directions and a heat transfer tube embedded in the three-dimensional structure. The three-dimensional structure and the heat transfer tube are integrally and inseparably shaped in a state where the heat transfer wall is fused to the outer peripheral surface of the heat transfer tube. The first fluid is brought into contact with both surfaces of the heat transfer wall, and the second fluid is allowed to flow through the heat transfer tube. [Effects of the Invention]

[0007] The technology disclosed herein suppresses the degradation of heat exchanger performance. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram showing a boiler according to the first embodiment. [Figure 2] Figure 2 is a schematic diagram showing the economizer according to the first embodiment. [Figure 3] Figure 3 is a schematic perspective view showing a part of the three-dimensional structure according to the first embodiment. [Figure 4] Figure 4 is a schematic cross-sectional view showing the economizer according to the first embodiment. [Figure 5] Figure 5 is a schematic cross-sectional view showing an economizer according to the second embodiment. [Figure 6] Figure 6 is a schematic cross-sectional view showing the relationship between the economizer and the exhaust pipe according to the second embodiment. [Figure 7] Figure 7 is a cross-sectional view showing the exhaust pipe and economizer according to the second embodiment. [Modes for carrying out the invention]

[0009] The embodiments will be described below with reference to the drawings. The components of the embodiments described below can be combined as appropriate. In addition, some components may be omitted.

[0010] [First Embodiment] The first embodiment will be described.

[0011] <Boiler> Figure 1 is a schematic diagram showing a boiler 1 according to the first embodiment. As shown in Figure 1, the boiler 1 comprises a boiler body 4, an air intake pipe 5, a blower 6, a fuel supply device 7, an exhaust pipe 8, a feedwater device 9, and an economizer 10.

[0012] The boiler body 4 generates steam by heating water W. The boiler body 4 has a boiler 2 to which water W is supplied, and a burner 3 that burns fuel to heat the water W in the boiler 2. The boiler 2 has water tubes 2A, a lower header 2B, and an upper header 2C. The water tubes 2A are cylindrical members through which water W flows. The water tubes 2A are long in the vertical direction. Multiple water tubes 2A are provided. The lower end of the water tubes 2A is connected to the lower header 2B. The upper end of the water tubes 2A is connected to the upper header 2C. The lower header 2B contains water W. The water W contained in the lower header 2B is supplied to each of the multiple water tubes 2A. The water tubes 2A allow water W from the lower header 2B to flow through them. The water tubes 2A are heated by the combustion gas G2 generated in the burner 3. When the water tubes 2A are heated, the water W flowing through the water tubes 2A is heated and steam is generated. The steam generated in water pipe 2A is supplied to the upper header 2C. The upper header 2C contains the steam supplied from water pipe 2A.

[0013] The air intake pipe 5 is connected to the blower 6 and the boiler 2, respectively. The blower 6 supplies combustion air A1 to the air intake pipe 5. The combustion air A1 supplied from the blower 6 flows through the air intake passage 5A inside the air intake pipe 5. The fuel supply device 7 supplies fuel gas G0 as fuel to the air intake passage 5A. The fuel supply device 7 includes a fuel supply pipe 7A having a supply port for supplying fuel gas G0 to the air intake passage 5A, and a flow control valve 7B that adjusts the flow rate of fuel gas G0 supplied from the fuel supply pipe 7A to the air intake passage 5A. In the air intake passage 5A, the combustion air A1 and fuel gas G0 are mixed to generate premixed gas G1. The premixed gas G1 is supplied to the burner 3.

[0014] Burner 3 burns premixed gas G1 to produce combustion gas G2. Burner 3 heats the water tube 2A with the combustion gas G2. When the water tube 2A is heated, the water W flowing through the water tube 2A is heated and steam is generated. The generated steam is collected by the upper header 2C and then discharged through a steam pipe (not shown).

[0015] The exhaust pipe 8 is connected to the can body 2. The combustion gas G2 discharged from the can body 2 flows through the flue 8A inside the exhaust pipe 8. After the combustion gas G2 flows through the flue 8A, it is discharged to the outside of the boiler 1.

[0016] The water supply device 9 supplies water W to the can body 2 via the economizer 10. The water supply device 9 includes a water supply line 9B connecting the water supply source 9A and the economizer 10, a water supply pump 9C that drives to supply water W to the economizer 10, and a flow rate adjustment valve 9D that adjusts the flow rate of the water W supplied to the economizer 10.

[0017] The economizer 10 is disposed in the flue 8A through which the combustion gas G2 flows. The economizer 10 exchanges heat between the combustion gas G2 discharged from the can body 2 and the water W supplied from the water supply device 9. The water W heated by the combustion gas G2 in the economizer 10 is supplied to the lower pipe side 2B of the can body 2 via the water supply line 9E. The lower pipe side 2B stores the water W supplied from the water supply device 9 via the economizer 10.

[0018] <Economizer> FIG. 2 is a diagram schematically showing the economizer 10 according to the first embodiment. In the following description, a three-dimensional orthogonal coordinate system is set for the economizer 10, and the positional relationship of each part will be described while referring to this three-dimensional orthogonal coordinate system. The direction parallel to the X-axis in the horizontal plane is defined as the X-axis direction. The direction parallel to the Y-axis orthogonal to the X-axis in the horizontal plane is defined as the Y-axis direction. The direction parallel to the Z-axis orthogonal to each of the X-axis and the Y-axis is defined as the Z-axis direction. The X-axis direction is the front-rear direction. The Y-axis direction is the left-right direction. The Z-axis direction is the up-down direction. The +X direction is the front. The -X direction is the rear. The +Y direction is the left. The -Y direction is the right. The +Z direction is the up. The -Z direction is the down.

[0019] The economizer 10 is a heat exchanger that exchanges heat between the combustion gas G2 and water W. The economizer 10 exchanges heat between the combustion gas G2, which is the first fluid, and water W, which is the second fluid. The heat transfer rate of the combustion gas G2 (gas) is different from that of water W (liquid). The heat transfer rate of the combustion gas G2 is lower than that of water W. The temperature of the combustion gas G2 before flowing into the economizer 10 is higher than the temperature of water W before flowing into the economizer 10. When the combustion gas G2 and water W exchange heat, the temperature of the combustion gas G2 decreases and the temperature of water W increases.

[0020] As shown in FIG. 2, the economizer 10 includes a three-dimensional structure 20 through which the combustion gas G2 and water W respectively flow, a right header 11, and a left header 12. The three-dimensional structure 20 is disposed in a flue 8A through which the combustion gas G2 flows. FIG. 2 shows a schematic external view of the three-dimensional structure 20.

[0021] The three-dimensional structure 20 has a first flow path 21 and a second flow path 22 separated by a heat transfer wall 23. The first flow path 21 and the second flow path 22 are alternately arranged in each of the X-axis direction, Y-axis direction, and Z-axis direction. The heat transfer wall 23 is formed along a triply periodic surface (triply periodic minimal surface). The first flow path 21 and the second flow path 22 are separated by the heat transfer wall 23 along the triply periodic surface.

[0022] The right header 11 is disposed on the right part of the three-dimensional structure 20. The left header 12 is disposed on the left part of the three-dimensional structure 20. Inlets 21A of the first flow path 21 and inlets 22A of the second flow path 22, each corresponding to an inlet of the combustion gas G2, are provided at the lower part of the three-dimensional structure 20. Outlets 21B of the first flow path 21 and outlets 22B of the second flow path 22, each corresponding to an outlet of the combustion gas G2, are provided at the upper part of the three-dimensional structure 20. In the right and left parts of the three-dimensional structure 20, the openings of the first flow path 21 and the second flow path 22 are sealed.

[0023] The combustion gas G2 discharged from the boiler body 2 flows into the inlet 21A of the first flow path 21 and the inlet 22A of the second flow path 22. The combustion gas G2 discharged from the three-dimensional structure 20 is discharged from the outlet 21B of the first flow path 21 and the outlet 22B of the second flow path 22. A water supply line 9B is connected to the right header 11. A water supply line 9E is connected to the left header 12.

[0024] <3D structure> Figure 3 is a schematic perspective view showing a part of the three-dimensional structure 20 according to the first embodiment. Figure 3 shows the appearance of a unit structure 24, which is part of the three-dimensional structure 20. The skeleton of the three-dimensional structure 20 is formed by arranging a plurality of unit structures 24 as shown in Figure 3. The unit structures 24 are arranged regularly and continuously in the XYZ directions. The three-dimensional structure 20 includes a plurality of unit structures 24 arranged regularly and continuously in the XYZ directions.

[0025] The unit structure 24 has a three-dimensional shape formed by the heat transfer wall 23. The heat transfer wall 23's external shape is defined by at least one of a pair of parallel curved surfaces and a plane. In this embodiment, the external shape of the heat transfer wall 23 is defined by a pair of mutually parallel curved surfaces. Alternatively, the external shape of the heat transfer wall 23 may be defined by a pair of mutually parallel planes. The external shape of the heat transfer wall 23 may be defined by a pair of mutually parallel curved surfaces and a pair of mutually parallel planes. The first flow path 21 and the second flow path 22 are separated by the heat transfer wall 23.

[0026] The three-dimensional structure 20 is constructed by applying a required thickness to a triple-periodic surface, based on the triple-periodic surface. The thickness of the heat transfer wall 23 is, for example, 0.4 mm. The heat transfer wall 23 is formed to follow the triple-periodic surface. A triple-periodic surface (triple-periodic minimum surface) is a surface with a minimum area among surfaces bounded by a closed curve given in three-dimensional space. Examples of triple-periodic surfaces include Schoen's gyroid surface (G surface), Schwarz's D surface, or Schoen's I-WP surface. In this embodiment, the three-dimensional structure 20 has a gyroid structure. The heat transfer wall 23 is formed to follow the gyroid surface.

[0027] A gyroid surface is a minimal surface that can be infinitely connected in three different directions and divides space into two regions. In an embodiment, gyroid surfaces can be infinitely connected in the X-axis, Y-axis, and Z-axis directions, respectively.

[0028] A gyroid surface is a surface whose area is minimized under given boundary conditions, and whose curvature becomes zero upon integration. A gyroid surface can be represented by the following approximation using trigonometric functions, shown in equation (1).

[0029] sinx·cosy+siny·cosz+sinz·cosx=0 …(1)

[0030] The heat transfer wall 23 is a wall centered on a hypothetical curved surface represented by equation (1), with a substantially uniform thickness in the direction normal to that curved surface.

[0031] <Heat transfer tube> Figure 4 is a schematic cross-sectional view showing an economizer 10 according to the first embodiment. As shown in Figure 4, the economizer 10 comprises a three-dimensional structure 20 having a gyroid structure and heat transfer tubes 25 embedded in the three-dimensional structure 20. In this embodiment, the heat transfer tubes 25 are straight tubes. The heat transfer tubes 25 are long in the Y-axis direction. Multiple heat transfer tubes 25 are provided. Multiple heat transfer tubes 25 are provided parallel to each other. Multiple heat transfer tubes 25 are provided in the Z-axis direction. For example, three heat transfer tubes 25 may be provided in the Z-axis direction. Multiple heat transfer tubes 25 may also be provided in the X-axis direction. For example, two heat transfer tubes 25 may be provided in the X-axis direction.

[0032] The three-dimensional structure 20 and the heat transfer tube 25 are formed integrally and inseparably, with the heat transfer wall 23 fused to the outer surface of the heat transfer tube 25.

[0033] The combustion gas G2 discharged from the boiler body 2 flows into the inlet 21A of the first flow path 21 and the inlet 22A of the second flow path 22, respectively. The combustion gas G2 that flows into the inlet 21A of the first flow path 21 flows through the first flow path 21 and then flows out from the outlet 21B of the first flow path 21. The combustion gas G2 that flows into the inlet 22A of the second flow path 22 flows through the second flow path 22 and then flows out from the outlet 22B of the second flow path 22. As the combustion gas G2 flows through the first flow path 21 and the second flow path 22, the combustion gas G2 comes into contact with both sides of the heat transfer wall 23. The combustion gas G2 that flows out from the outlet 21B of the first flow path 21 and the outlet 22B of the second flow path 22 are discharged to the outside of the boiler 1.

[0034] The inlet 25A of the heat transfer tube 25 is connected to the right header 11. The outlet 25B of the heat transfer tube 25 is connected to the left header 12. Water W supplied from the water supply line 9B to the right header 11 flows into the inlet 25A of the heat transfer tube 25. After flowing through the heat transfer tube 25, the water W flows out from the outlet 25B of the heat transfer tube 25. The water W that flows out from the outlet 25B of the heat transfer tube 25 is discharged to the left header 12. The water W discharged to the left header 12 is supplied to the lower header 2B of the boiler body 2 via the water supply line 9E.

[0035] In this embodiment, the right end face of the three-dimensional structure 20 is covered by a cover member 26A. The cover member 26A prevents water W from flowing into the first channel 21 and the second channel 22 from the right end face of the three-dimensional structure 20. The left end face of the three-dimensional structure 20 is covered by a cover member 26B. The cover member 26B prevents combustion gas G2 flowing through the first channel 21 and the second channel 22 from flowing out from the left end face of the three-dimensional structure 20.

[0036] As the combustion gas G2 comes into contact with both sides of the heat transfer wall 23 and the coolant water W flows through the heat transfer tube 25, heat exchange occurs between the combustion gas G2 and the water W.

[0037] In this embodiment, the three-dimensional structure 20 and the heat transfer tubes 25 are integrally formed by three-dimensional additive manufacturing. The three-dimensional structure 20 and the heat transfer tubes 25 are integrally formed by a 3D printer. The material used to form the three-dimensional structure 20 and the material used to form the heat transfer tubes 25 are the same.

[0038] <Effects> As described above, the economizer 10, a type of heat exchanger, has a three-dimensional shape formed by heat transfer walls 23 whose outer shape is defined by at least one of a pair of parallel curved surfaces and planes, which serves as the unit structure 24. This unit structure 24 comprises three-dimensional structures 20 arranged regularly and continuously in the XYZ directions, and heat transfer tubes 25 embedded in the three-dimensional structures 20. The three-dimensional structures 20 and the heat transfer tubes 25 are integrally and inseparably formed with the heat transfer walls 23 fused to the outer surface of the heat transfer tubes 25. The first fluid, combustion gas G2, is brought into contact with both sides of the heat transfer walls 23, and the second fluid, water W, is circulated through the heat transfer tubes 25.

[0039] According to this embodiment, since the heat transfer tubes 25 are embedded in the three-dimensional structure 20, the combustion gas G2 flowing through the first channel 21 and the second channel 22 of the three-dimensional structure 20 and the water W flowing through the heat transfer tubes 25 are efficiently heat-exchanged. Since the heat transfer tubes 25 are straight, the accumulation of foreign matter in the flow path of the heat transfer tubes 25 is suppressed. Therefore, the deterioration of the performance of the economizer 10 is suppressed.

[0040] In this embodiment, water W flows through the heat transfer tubes 25. Contact with water W may cause corrosion of the inner surface of the heat transfer tubes 25, or deposits (scale) from water W may adhere to the inner surface of the heat transfer tubes 25. Because the heat transfer tubes 25 are straight, the force of the water flow suppresses the accumulation of foreign matter (rust, scale) on the inner surface of the heat transfer tubes 25. Furthermore, even if foreign matter adheres to the inner surface of the heat transfer tubes 25, because the heat transfer tubes 25 are straight, maintenance workers of the boiler 1 can easily remove the foreign matter from the inner surface of the heat transfer tubes 25. In other words, because the heat transfer tubes 25 are straight, maintenance workers of the boiler 1 can easily maintain the economizer 10. Combustion gas G2 flows through the first flow path 21 and the second flow path 22 of the three-dimensional structure 20, so the accumulation of foreign matter in the first flow path 21 and the second flow path 22 is suppressed.

[0041] [Second Embodiment] A second embodiment will now be described. In the following description, components that are the same as or equivalent to those in the first embodiment described above will be denoted by the same reference numerals, and the descriptions of those components will be simplified or omitted.

[0042] <Economizer> Figure 5 is a schematic cross-sectional view of the economizer 110 according to the second embodiment. Figure 5 is a cross-sectional view of the economizer 110 parallel to the XY plane. The economizer 110 is positioned in the flue inside the exhaust pipe 108. As shown in Figure 5, the economizer 110 has a three-dimensional structure 20 and heat transfer tubes 125 embedded in the three-dimensional structure 20. The three-dimensional structure 20 and the heat transfer tubes 125 are integrally and inseparably formed with the heat transfer walls 23 fused to the outer circumferential surface of the heat transfer tubes 125.

[0043] Similar to the first embodiment described above, the combustion gas G2 discharged from the boiler 2 flows through the first flow path 21 and the second flow path 22 of the three-dimensional structure 20, respectively. Water W from the water supply line 9B flows into the inlet 125A of the heat transfer tube 125 and then flows through the heat transfer tube 125. After flowing through the heat transfer tube 125, the water W flows out from the outlet 125B of the heat transfer tube 125 and is then supplied to the lower header 2B of the boiler 2 via the water supply line 9E.

[0044] In this embodiment, the heat transfer tube 125 has a plurality of straight sections 125C and bent sections 125D that connect adjacent straight sections 125C. The straight sections 125C are elongated in the Y-axis direction. The plurality of straight sections 125C are arranged parallel to each other. Multiple straight sections 125C are provided in the X-axis direction. Multiple bent sections 125D are provided. The first bent section 125D connects the left end of the first straight section 125C having an inlet 125A to the left end of the second straight section 125C located next to the rear of the first straight section 125C. The second bent section 125D connects the right end of the second straight section 125C to the right end of the third straight section 125C located next to the rear of the second straight section 125C. The third bend 125D connects the left end of the third straight pipe section 125C to the left end of the fourth straight pipe section 125C, which is located next to the rear of the third straight pipe section 125C. The fourth bend 125D connects the right end of the fourth straight pipe section 125C to the right end of the fifth straight pipe section 125C, which is located next to the rear of the fourth straight pipe section 125C. The fifth bend 125D connects the left end of the fifth straight pipe section 125C to the left end of the sixth straight pipe section 125C, which has an outlet 125B and is located next to the rear of the fifth straight pipe section 125C.

[0045] The inlet 125A and outlet 125B are located to the right of the exhaust pipe 108. In this embodiment, an opening 108B is provided on the right side of the exhaust pipe 108. The opening 108B of the exhaust pipe 108 is closed by a flange 30. The flange 30 is joined to the outer surface of the heat transfer tube 125 so as to support the right side of the first straight pipe section 125C having the inlet 125A and the right side of the sixth straight pipe section 125C having the outlet 125B. The flange 30 may be fixed to the first straight pipe section 125C and the sixth straight pipe section 125C. The flange 30 may be detachable from the first straight pipe section 125C and the sixth straight pipe section 125C. The second straight pipe section 125C, the third straight pipe section 125C, the fourth straight pipe section 125C, and the fifth straight pipe section 125C are embedded in the three-dimensional structure 20. Each of the multiple bent sections 125D is embedded in the three-dimensional structure 20.

[0046] Figure 6 is a schematic cross-sectional view showing the relationship between the economizer 110 and the exhaust pipe 108 according to the second embodiment. As shown in Figure 6, the exhaust pipe 108 and the economizer 110 are separable. The economizer 110 can pass through the opening 108B of the exhaust pipe 108. The exhaust pipe 108 and the flange 30 are separable. Maintenance workers of the boiler 1 can pull the economizer 110 out of the exhaust pipe 108 together with the flange 30. The direction in which the economizer 110 is pulled out may be left-right or front-back. The positions of the inlet 125A and outlet 125B are set to match the direction in which the economizer 110 is pulled out.

[0047] Figure 7 is a cross-sectional view showing the exhaust pipe 108 and economizer 110 according to the second embodiment. Figure 7 corresponds to a view from the right side of a cross-section of the economizer 110 attached to the exhaust pipe 108. As shown in Figure 7, two heat transfer tubes 125 are embedded in the three-dimensional structure 20. The two heat transfer tubes 125 are arranged in the vertical direction. Since the flange 30 is detachable from the opening 108B of the exhaust pipe 108, maintenance workers of the boiler 1 can pull out the economizer 110 from the exhaust pipe 108. Therefore, the economizer 110 removed from the exhaust pipe 108 can be maintained with ease. Specifically, the inside of the heat transfer tubes 125 can be cleaned, and the flow path portion and heat transfer surface of the three-dimensional structure 20 can be cleaned.

[0048] [Other embodiments] In the above-described embodiment, the heat exchanger is assumed to be the economizer 10. The heat exchanger may also be the heat exchanger of a heat device such as a latent heat recovery type gas water heater. [Explanation of symbols]

[0049] 1... Boiler, 2... Boiler body, 2A... Water pipe, 2B... Lower header, 2C... Upper header, 3... Burner, 4... Boiler body, 5... Air intake pipe, 5A... Air intake passage, 6... Blower, 7... Fuel supply device, 7A... Fuel supply pipe, 7B... Flow control valve, 8... Exhaust pipe, 8A... Flue, 9... Feedwater device, 9A... Feedwater source, 9B... Feedwater line, 9C... Feedwater pump, 9D... Flow control valve, 9E... Feedwater line, 10... Economizer, 11... Right header, 12... Left header, 20... Vertical Body structure, 21...First flow path, 21A...Inlet, 21B...Outlet, 22...Second flow path, 22A...Inlet, 22B...Outlet, 23...Heat transfer wall, 24...Unit structure, 25...Heat transfer tube, 25A...Inlet, 25B...Outlet, 26A...Cover member, 26B...Cover member, 30...Flange, 108...Exhaust pipe, 108B...Opening, 110...Economizer, 125...Heat transfer tube, 125A...Inlet, 125B...Outlet, 125C...Straight pipe section, 125D...Bent section.

Claims

1. A three-dimensional structure is formed by a heat transfer wall whose outer shape is defined by at least one of a pair of parallel curved surfaces and planes, and the three-dimensional structure is formed by the regular and continuous repeated arrangement of these unit structures in the XYZ directions. The three-dimensional structure includes a heat transfer tube embedded in it, The three-dimensional structure and the heat transfer tube are formed integrally and inseparably, with the heat transfer wall fused to the outer surface of the heat transfer tube. The first fluid is brought into contact with both sides of the heat transfer wall, and the second fluid is circulated through the heat transfer tube. heat exchanger.

2. The combustion gas is brought into contact with both sides of the heat transfer wall, and a coolant is circulated through the heat transfer tube. The heat exchanger according to claim 1.

3. The aforementioned three-dimensional structure is placed in the flue through which the combustion gas flows. The heat exchanger according to claim 2.

4. The aforementioned three-dimensional structure is formed by using a triple-periodic curved surface as a reference and applying the required thickness to this curved surface to create a heat transfer wall. The heat exchanger according to claim 1.

5. The aforementioned three-dimensional structure has a gyroid structure. The heat exchanger according to claim 4.

6. The three-dimensional structure and the heat transfer tube are integrally formed by three-dimensional additive manufacturing. The heat exchanger according to claim 1.

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