Lightweight finned tube

Abstract

The utility model relates to the technical field of heat exchanger manufacturing, in particular to a light-weight finned tube which comprises a base tube, the base tube is a titanium alloy tube, a fin structure assembly is fixedly arranged on the outer wall of the base tube, and the fin structure assembly is a three-dimensional aluminum alloy structural part with turbulent flow micro-channels. The fin structure assembly is used for improving the heat exchange efficiency of the finned tube through the turbulence micro-channel and is fixed to the outer wall of the base tube through vacuum brazing; the light-weight finned tube is provided with the fin structure assembly and the base tube, the fin structure assembly is fixed on the outer wall of the base tube through vacuum brazing, and the light-weight finned tube structure is light in weight, high in strength and efficient in heat exchange performance, and is particularly suitable for compact heat exchange equipment such as an air cooler and a condenser. The fin structure assembly is a 3D printing integrally-formed aluminum alloy structural part, a mold is liberated, and a complex fin shape can be manufactured.

Description

Technical Field

[0001] This utility model relates to the field of heat exchanger manufacturing technology, specifically to a lightweight finned tube. Background Technology

[0002] Existing compact air cooler finned tubes generally use a single metal material, such as all-titanium finned tubes, all-aluminum finned tubes, or steel-aluminum composite finned tubes. However, using a single metal material has the following drawbacks:

[0003] While all-titanium finned tubes are corrosion-resistant and high-temperature resistant, their low thermal conductivity and high mass (typically ≥2.9 kg / m per unit length) make them unsuitable for lightweight applications. All-aluminum finned tubes offer excellent thermal conductivity and are lightweight, but their pressure resistance and high-temperature strength are insufficient (strength decreases significantly above 250℃), making them unsuitable for high-pressure conditions (such as a design pressure of 3 MPa). Steel-aluminum composite finned tubes, produced using high-frequency welding or mechanical expansion to form spiral fins from metal strips and coat the outer surface of the base tube, are limited by mold specifications, making it difficult to manufacture complex fin shapes. Furthermore, their heat exchange performance is limited, and their weight increases. Additionally, the poor wettability and formation of brittle Ti-Al intermetallic compounds during the welding of dissimilar metals like titanium and aluminum hinder mass production.

[0004] Therefore, a lightweight finned tube is needed to improve the above-mentioned problems. Summary of the Invention

[0005] To address the problems of existing technologies, this utility model provides a lightweight finned tube, including a base tube, which is a titanium alloy tube, and a finned structure assembly fixedly disposed on the outer wall of the base tube. The finned structure assembly is a three-dimensional aluminum alloy structure with turbulent microchannels, which is used to improve the heat exchange efficiency of the finned tube through the turbulent microchannels.

[0006] Furthermore, the fin structure component is integrally formed into a three-dimensional aluminum alloy structural part using 3D printing.

[0007] Furthermore, the fin structure assembly includes several parallel annular fins, and several tree-shaped support columns are connected between adjacent fins to form the turbulent microchannel.

[0008] Furthermore, the tree-like support column includes a main trunk and several branching branches connected to the main trunk.

[0009] Furthermore, the spacing between adjacent annular fins in the fin structure assembly is 6-10mm, the height of the annular fins is 8-20mm, and the thickness of the annular fins is 0.4-0.6mm.

[0010] Furthermore, the diameter of the support column is 0.4mm-0.8mm, and the angle between the branch of the support column and the main rod is 50°-80°.

[0011] Furthermore, the fin structure assembly is fixed to the outer wall of the base tube by vacuum brazing.

[0012] Furthermore, a barrier layer is provided on the outer surface of the base tube, and the barrier layer is located at least at the connection between the base tube and the fin structure assembly.

[0013] Furthermore, the barrier layer is a Ni-Cu-Ti alloy layer.

[0014] The beneficial effects of this utility model are:

[0015] This utility model relates to a lightweight finned tube, which consists of a finned structure assembly and a base tube. The finned structure assembly is fixed to the outer wall of the base tube by vacuum brazing. The finned tube structure is lightweight, high-strength, and has high heat exchange performance. It is especially suitable for compact heat exchange equipment such as air coolers and condensers. The finned structure assembly is a 3D printed one-piece aluminum alloy structural part, which eliminates the need for molds and allows for the manufacture of complex fin shapes. Attached Figure Description

[0016] Figure 1 This is a three-dimensional schematic diagram of the lightweight finned tube of this utility model;

[0017] Figure 2 Main view of the lightweight finned tube of this utility model;

[0018] Figure 3 This utility model provides a schematic diagram of its support structure.

[0019] Figure label:

[0020] In the diagram: 1-base tube, 2-finned structure assembly, 3-support column. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Please see Figure 1-3 This utility model provides a lightweight finned tube, including a base tube 1, which is a titanium alloy tube. A finned structure assembly 2 is fixedly disposed on the outer wall of the base tube 1. The finned structure assembly 2 is a three-dimensional aluminum alloy structure with turbulent microchannels, which is used to improve the heat exchange efficiency of the finned tube. The finned structure assembly 2 is fixed to the outer wall of the base tube 1 by vacuum brazing.

[0023] It should be noted that the fin structure component 2 is printed with a three-dimensional aluminum alloy fin structure of ring fins and tree-shaped support columns 3 using selective laser melting technology in 3D printing. The fin structure component 2 has a fin height of 16mm, a fin spacing of 6mm, a support diameter of 0.4mm, a branch angle of 50°, and a fin root brazing groove depth of 0.15mm.

[0024] 3D-printed tree-shaped fins eliminate the need for molds, allowing for flexible optimization of fin height, spacing, and support according to working conditions, avoiding the limitations of traditional mold specifications and liberating molds. Several tree-shaped support columns form turbulent microchannels, improving heat exchange by 30% compared to conventional annular fins. Enhanced heat exchange is achieved through a combination of high-thermal-conductivity aluminum alloy fins and high-strength titanium alloy base tubes, resulting in a 35-40% weight reduction compared to all-titanium finned tubes of the same specifications, while still meeting a 3MPa design pressure. The finned tubes are lightweight and possess high strength.

[0025] High strength: welded joint shear strength ≥60MPa, pressure resistance 3MPa×1.5; high heat transfer: fin ratio ≥22, pump power PEC ≥1.2; a 3-8μm thick Ni-Cu-Ti barrier layer is provided at the brazing interface, which is formed by physical vapor deposition or electroplating; AlSiZn-based brazing filler metal is used at a vacuum degree ≤5×10 -3 Brazing under conditions of Pa and temperature of 585-600℃, the resulting finned tube has a unit length mass ≤1.9kg / m and a brazed joint shear strength ≥60MPa;

[0026] The lightweight finned tube is provided with a finned structure component 2 and a base tube 1. The finned structure component 2 is fixed to the outer wall of the base tube 1 by vacuum brazing. The finned tube structure of this application has the characteristics of lightweight, high heat exchange efficiency and high strength. The finned structure component is a 3D printed one-piece aluminum alloy structural part, freeing up the mold; it can manufacture complex fin shapes.

[0027] Wherein, a barrier layer is provided on the outer surface of the base tube 1, and the barrier layer is located at least at the connection between the base tube and the fin structure assembly; the barrier layer is a Ni-Cu-Ti alloy layer;

[0028] Furthermore, the fin structure component 2 is integrally formed into a three-dimensional aluminum alloy structural part using 3D printing;

[0029] Furthermore, the fin structure assembly 2 includes several parallel annular fins, and several tree-shaped support columns 3 are connected between adjacent fins to form turbulent microchannels;

[0030] Furthermore, the tree-like support column 3 includes a main stem and several branching branches connected to the main stem.

[0031] It should be noted that turbulent microchannels improve the heat transfer efficiency of finned tubes through the following mechanisms, the specific principles and effects of which are as follows: First, the turbulence enhancement mechanism: On the surface of traditional smooth fins, the fluid tends to form a stable laminar boundary layer with high thermal resistance, which restricts heat transfer. The tree-like support columns 3 form dense microscale channels between the fins (such as branch diameters of 0.3-0.5 mm and included angles of 45-60°), which forces the fluid to generate high-frequency disturbances when it flows through, breaking the laminar boundary layer and causing the fluid to change from laminar to turbulent.

[0032] In turbulent flow, the convective heat transfer coefficient of a fluid can be 2-3 times higher than that of laminar flow.

[0033] The microchannel effect, where the narrow channels (6-10mm spacing) formed by adjacent fins and support columns 3 have a high aspect ratio, increases wall friction resistance as fluid flows within these microchannels, further intensifying turbulence and making heat transfer more efficient. Secondly, it expands the effective heat exchange area. The tree-like support columns 3 themselves have a three-dimensional branching structure (such as secondary or tertiary branches), and their surfaces can directly participate in heat exchange, effectively increasing the heat exchange area by approximately 20%-30% compared to traditional annular fins. Quantitative analysis shows that the heat exchange area per unit length of a conventional annular fin is approximately 1.1m². 2 / m, with fins containing tree-like supports, the height can be increased to 1.53m. 2 / m (Example 2), the total heat exchange area increases by 40%. A multi-directional heat conduction path is established; the support column 3, annular fins, and base tube form a three-dimensional heat conduction network. Heat is conducted radially from the base tube 1 through the fins and diffuses circumferentially through the support column 3, shortening the heat flow path and reducing contact thermal resistance. Third, induced vortices and secondary flows are achieved. When the fluid flows through the branch nodes of the tree-like support column 3, a sudden change in the cross-sectional area of ​​the flow channel creates a wake vortex on the back side of the branch. The vortex enhances internal mixing of the fluid, allowing the high-temperature fluid to fully contact the low-temperature wall surface, reducing the thermal boundary layer thickness.

[0034] Secondary flow enhancement: Asymmetric branches of a tree-like structure (such as asymmetric angle design) induce transverse secondary flow in the fluid, forcing the mainstream fluid to exchange momentum with the fluid near the wall, thereby further improving heat transfer efficiency.

[0035] Experimental data: Under the same operating conditions, the pump performance coefficient (PEC) of finned tubes with secondary flow effect can reach 1.33 (Example 2), which is 11% higher than that of conventional annular fins (PEC = 1.2).

[0036] Therefore, the turbulent microchannels formed by the tree-like support columns 3 significantly improve the heat transfer efficiency of finned tubes through a triple mechanism of enhancing turbulent disturbance, expanding heat transfer area, and inducing vortex mixing.

[0037] Furthermore, the outer diameter of the base tube 1 is 25-30 mm, and the wall thickness is 1.5-3 mm;

[0038] Furthermore, in the fin structure assembly 2, the spacing between adjacent annular fins is 6-10mm, the height of the annular fins is 8-20mm, and the thickness of the annular fins is 0.4-0.6mm;

[0039] Furthermore, the diameter of the support column 3 is 0.4mm-0.8mm, and the branch angle of the support column 3 is 50°-80°;

[0040] Furthermore, the finned structure assembly 2 and the base tube 1 are subjected to interference fit, with an initial interference fit amount of 0.05-0.10 mm;

[0041] It should be noted that "initial interference fit amount of 0.05-0.10mm" means that at the beginning of assembly, the size of the base tube is 0.05mm to 0.10mm larger than the size of the hole in the finned structure assembly. For example, if the diameter of the hole is 50mm, then the diameter of the base tube should be between 50.05mm and 50.10mm to achieve interference fit.

[0042] The finned structure assembly 2 is fixed to the outer wall of the base tube 1 by vacuum brazing. A 3-8 μm Ni-Cu-Ti barrier layer is provided at the brazing interface. Al-Si-Zn brazing filler metal is used for brazing under vacuum conditions ≤5×10-3 Pa and temperature conditions 585-600℃. The resulting finned tube has a unit length mass ≤1.9 kg / m and a brazed joint shear strength ≥60 MPa. The finned structure assembly 2 is connected to the base tube 1. Vacuum brazing and the Ni-Cu-Ti barrier layer suppress the Ti-Al brittle phase. The intermetallic compound in the weld is <5 μm, and no cracks appear after 500 thermal cycles. This ensures a reliable connection between the finned structure assembly 2 and the base tube 1.

[0043] Example 1, preparation of base tube: Take a TC4 titanium alloy seamless tube with an outer diameter of 25 mm and a wall thickness of 1.5 mm, sandblast the surface (Sa2.5) and then ultrasonically clean it, and vacuum degrease it at 250℃ for 30 min.

[0044] A 3D-printed tree-like fin structure is used, employing SLM technology to print AlSi10Mg ring fins and a tree-like support column structure. The fin height is 16mm, the fin spacing is 6mm, the support diameter is 0.4mm, the branch angle is 50°, and the fin root brazing groove depth is 0.15mm. The base tube has an outer diameter of 25mm, and the barrier layer is 5μm thick.

[0045] Fin assembly: The AlSi10Mg ring fins (12mm fin height, 0.5mm fin thickness, 8mm fin spacing) with an inner diameter of 24.94mm are fitted onto the base tube 1 with an interference of 0.06mm. A 0.1mm thick AlSiZn brazing foil is placed at the contact point. Vacuum brazing: The assembled parts are placed in a vacuum furnace and heated to 595℃ at a rate of 5℃ / min, held for 12min, and then cooled to below 150℃ before being removed from the furnace. The Ni-Cu-Ti barrier layer is made by electroplating. A 5μm thick Ni-Cu-Ti barrier layer is prepared on the outer surface of the base tube by electroplating.

[0046] Post-treatment: A 4-hour pressure holding test at 1.5 times the design pressure (4.5 MPa) was conducted, and no leakage was observed; subsequently, stress was relieved by annealing at 300℃ for 2 hours.

[0047] Performance testing: The shear strength of the randomly selected joint was tested and found to be 65 MPa.

[0048] The mass per unit length is 1.85 kg / m (compared to 2.9 kg / m for the all-titanium comparison), representing a 36.2% weight reduction compared to the all-titanium design; the heat exchange area per unit length is 1.53 m². 2 / m, PEC value 1.33, heat transfer coefficient reaches 84W / m 2 •K, 30% higher than conventional ring fins;

[0049] Simulation verification: Computational fluid dynamics (CFD) simulations show that the temperature gradient of the turbulent microchannel (vortex region) formed by the tree-like support column 3 in the finned tube with tree-like support is reduced by 15%-20% compared with the conventional structure, indicating that the heat distribution is more uniform.

[0050] It is worth noting that this utility model is applicable to the field of lightweight and high-efficiency heat exchange equipment. A lightweight finned tube utilizes a titanium alloy (Ti6Al4V) base tube for high-strength support, and AlSi-based aluminum alloy fins (optionally 3D-printed tree-like structures) to enhance thermal conductivity and heat exchange efficiency. A reliable metallurgical bond is achieved through a Ni-Cu-Ti barrier layer and vacuum brazing process. Under operating conditions of 3MPa pressure and 250℃, this structure exhibits a brazing shear strength ≥60MPa, and the heat exchange area per unit length of the fins is 1.53m². 2 / m; the unit length mass is ≤1.9kg / m, which is 35% lighter than traditional titanium finned tubes and 25% more efficient in heat exchange, making it suitable for lightweight and efficient heat exchange applications such as air coolers and process cooling.

[0051] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A lightweight finned tube, characterized in that, The device includes a base tube, which is a titanium alloy tube. A finned structure assembly is fixedly installed on the outer wall of the base tube. The finned structure assembly is a three-dimensional aluminum alloy structure with turbulent microchannels, which is used to improve the heat exchange efficiency of the finned tube through the turbulent microchannels.

2. The lightweight finned tube according to claim 1, characterized in that, The finned structure component is a three-dimensional aluminum alloy structural part formed by 3D printing.

3. The lightweight finned tube according to claim 1, characterized in that, The fin structure assembly includes several parallel annular fins, and several tree-shaped support columns are connected between adjacent fins to form the turbulent microchannel.

4. The lightweight finned tube according to claim 3, characterized in that, The tree-like support column includes a main trunk and several branching branches connected to the main trunk.

5. The lightweight finned tube according to claim 3, characterized in that, The spacing between adjacent annular fins in the fin structure assembly is 6-10mm, the height of the annular fin is 8-20mm, and the thickness of the annular fin is 0.4-0.6mm.

6. The lightweight finned tube according to claim 4, characterized in that, The diameter of the support column is 0.4mm-0.8mm, and the angle between the branch of the support column and the main rod is 50°-80°.

7. The lightweight finned tube according to claim 1, characterized in that, The finned structure assembly is fixed to the outer wall of the base tube by vacuum brazing.

8. The lightweight finned tube according to claim 1, characterized in that, A barrier layer is provided on the outer surface of the base tube, and the barrier layer is located at least at the connection between the base tube and the fin structure assembly.

9. The lightweight finned tube according to claim 8, characterized in that, The barrier layer is a Ni-Cu-Ti alloy layer.

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