Laser welding finned tube for compressed air heat exchanger

Abstract

The utility model provides a laser welding finned tube for a compressed air heat exchanger. The laser welding finned tube comprises a heat exchange tube, a spiral band is arranged at the outer end of the heat exchange tube, a laser welding point is arranged between the spiral band and the heat exchange tube, the outer end of the heat exchange tube is wrapped with an air heat exchanger, the base material of the heat exchange tube is a high-strength steel tube, and the spiral band is made of a metal material with good heat conduction performance. The problems that according to the design of an existing threaded fin, for a large energy storage project, a large heat exchange area is needed, the number of used heat exchange pipes is large, and the equipment manufacturing cost is high are solved.

Description

Technical Field

[0001] This utility model relates to the field of compressed air heat exchanger technology, and more specifically, to a laser-welded finned tube for compressed air heat exchangers. Background Technology

[0002] In large air compressor coolers, finned heat transfer enhancement technology is commonly used to reduce manufacturing costs. Air compressors are devices that operate in a steady state. Fins are generally made of aluminum and heat exchange tubes and are joined together by expansion. However, this material combination is not suitable for the air energy storage industry. The alternating operating conditions of frequent start-stop cycles of compressors and expanders mean that the original fin enhancement method cannot meet the operating conditions of the energy storage industry. However, laser-welded finned tubes are readily available on the market. This type of tube can not only enhance heat transfer but also meet the requirements of long-term stable operation under alternating operating conditions.

[0003] In the current technology, the production process of threaded fins involves rolling and extruding thick-walled heat exchange tubes to create threaded fins with a diameter of no more than 1.2 mm. This results in a low fin density. For large-scale energy storage projects, which require a large heat exchange area and a large number of heat exchange tubes, the equipment manufacturing cost is relatively high. Therefore, we have made an improvement and proposed a laser-welded finned tube for compressed air heat exchangers. Utility Model Content

[0004] The purpose of this invention is to address the current design of threaded fins, which involves manufacturing threaded fins of no more than 1.2 mm on the surface of thick-walled heat exchange tubes through rolling and extrusion. This results in a low fin density, which is problematic for large-scale energy storage projects that require large heat exchange areas, a large number of heat exchange tubes, and high equipment manufacturing costs.

[0005] To achieve the above-mentioned objectives, this utility model provides the following technical solution:

[0006] A laser-welded finned tube for compressed air heat exchangers is proposed to improve the aforementioned problems.

[0007] The application is as follows:

[0008] A laser-welded finned tube for a compressed air heat exchanger includes a heat exchange tube, a spiral band at the outer end of the heat exchange tube, a laser welding point between the spiral band and the heat exchange tube, and an air heat exchanger wrapped around the outer end of the heat exchange tube.

[0009] As a preferred technical solution in this application, the base material of the heat exchange tube is a high-strength steel tube.

[0010] As a preferred technical solution of this application, the spiral strip is made of a metal material with good thermal conductivity.

[0011] As a preferred technical solution in this application, the welding steps for laser welding points are as follows:

[0012] S1. Welding preparation steps: Clean the surface of the heat exchange tube and spiral ribbon to remove impurities such as oil and oxide layer; adjust the parameters of the laser welding equipment, including laser power, pulse frequency, welding speed, and spot diameter; fix the heat exchange tube on the welding fixture and adjust the relative position of the spiral ribbon and the heat exchange tube to ensure that the two are tightly fitted and the welding gap meets the requirements.

[0013] S2. Positioning Welding Step: A low-energy-density laser beam is used to perform positioning welding along the predetermined welding start position of the heat exchange tube and the spiral strip. Positioning welding points are set at certain intervals to initially fix the spiral strip on the surface of the heat exchange tube and prevent displacement during the formal welding process.

[0014] S3. Continuous welding steps: According to the set welding path, the heat exchange tube and the spiral strip are continuously welded with optimized laser welding parameters. Starting from the positioning welding point, the laser beam moves at a constant speed along the joint of the two to ensure that the weld is uniform and continuous. The welding quality is monitored in real time during the welding process, and the welding parameters are adjusted in a timely manner.

[0015] S4. Post-welding processing steps: Perform visual inspection on the welded heat exchange tubes to remove spatter and burrs from the weld surface; use non-destructive testing methods to detect internal defects in the weld and repair any defects found; perform stress relief treatment on the heat exchange tubes to improve their overall performance.

[0016] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0017] In the scheme of this application:

[0018] 1. Improved heat exchange efficiency: The heat exchange tube structure with a high fin ratio greatly increases the heat exchange area. At the same time, laser welding ensures a good connection between the spiral ribbon and the heat exchange tube, which improves the efficiency of heat transfer and significantly enhances the overall heat exchange performance of the heat exchanger by at least 25%.

[0019] 2. Reduce manufacturing costs: The use of laser welding technology reduces the complex processes and material waste in traditional manufacturing processes. At the same time, the application of high fin ratio heat exchange tubes can reduce the number of heat exchange tubes and the overall size of the heat exchanger while meeting the same heat exchange requirements, thereby reducing raw material costs and manufacturing costs.

[0020] 3. Enhanced reliability: Laser welding features a small heat-affected zone and high welding strength, resulting in a firm and reliable connection between the heat exchange tube and the spiral ribbon. This allows the system to better adapt to the alternating operating conditions of the compressed air energy storage system, improving the service life and operational reliability of the heat exchanger. Attached Figure Description

[0021] Figure 1 A schematic diagram of the overall structure of a laser-welded finned tube for a compressed air heat exchanger provided in this application;

[0022] Figure 2 This application provides an overall structural schematic diagram of a laser-welded finned tube for a compressed air heat exchanger.

[0023] As shown in the figure:

[0024] 1. Heat exchange tube; 2. Air heat exchanger; 3. Laser welding point; 4. Spiral ribbon. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model.

[0026] Therefore, the following detailed description of the embodiments of this utility model is not intended to limit the scope of the claimed utility model, but merely illustrates some embodiments of the utility model. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without inventive effort are within the scope of protection of this utility model. It should be noted that, unless otherwise specified, the embodiments, features, and technical solutions in the embodiments of this utility model can be combined with each other.

[0027] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0028] like Figure 1-2 As shown, this embodiment proposes a laser-welded finned tube for a compressed air heat exchanger, including a heat exchange tube 1, a spiral band 4 at the outer end of the heat exchange tube 1, a laser welding point 3 between the spiral band 4 and the heat exchange tube 1, and an air heat exchanger 2 wrapped around the outer end of the heat exchange tube 1.

[0029] The base material of heat exchange tube 1 is a high-strength steel pipe.

[0030] Spiral ribbon 4 is made of a metal material with good thermal conductivity.

[0031] The welding steps for laser welding point 3 are as follows:

[0032] S1. Welding preparation steps: Clean the surfaces of heat exchange tube 1 and spiral ribbon 4 to remove oil, oxide layer and other impurities; adjust the parameters of the laser welding equipment, including laser power, pulse frequency, welding speed and spot diameter; fix heat exchange tube 1 on the welding fixture and adjust the relative position of spiral ribbon 4 and heat exchange tube 1 to ensure that the two are tightly fitted and the welding gap meets the requirements.

[0033] S2. Positioning welding step: A low energy density laser beam is used to perform positioning welding along the predetermined welding start position of heat exchange tube 1 and spiral strip 4. Positioning welding points are set at certain intervals to initially fix the spiral strip 4 on the surface of heat exchange tube 1 and prevent displacement during the formal welding process.

[0034] S3. Continuous welding steps: According to the set welding path, the heat exchange tube 1 and the spiral strip 4 are continuously welded with optimized laser welding parameters. Starting from the positioning welding point, the laser beam moves at a constant speed along the joint of the two to ensure that the weld is uniform and continuous. The welding quality is monitored in real time during the welding process, and the welding parameters are adjusted in a timely manner.

[0035] S4. Post-welding treatment steps: Perform visual inspection on the welded heat exchanger tube 1 to remove spatter and burrs from the weld surface; use non-destructive testing methods to detect internal defects in the weld and repair any detected defects; perform stress relief treatment on the heat exchanger tube 1 to improve its overall performance.

[0036] When this application is used:

[0037] Welding process steps:

[0038] (1) Welding preparation steps

[0039] Material surface treatment: The high-strength steel pipe used as heat exchange tube 1 and the spiral ribbon 4 with good thermal conductivity are carefully cleaned. Chemical cleaning agents are used to remove surface oil stains, and mechanical grinding or pickling is used to remove oxide layers and other impurities to ensure that the welding surface is clean and smooth, which is beneficial to the subsequent welding process and improves the welding quality.

[0040] Equipment parameter adjustment: Based on the material properties, thickness, and welding requirements of heat exchange tube 1 and spiral strip 4, precisely adjust the parameters of the laser welding equipment. The laser power needs to be set according to the material's absorption characteristics and welding depth requirements, generally within the range of 200W-5000W; the pulse frequency affects the microstructure and welding strength of the weld, and should be set between 1Hz and 200Hz; the welding speed must ensure the continuity and uniformity of the weld, typically 0.2m / min-13m / min; the spot diameter should be adjusted to 0.1mm-1.5mm based on the size and precision requirements of the welding area.

[0041] Tooling and positioning: The heat exchange tube 1 is securely fixed on a specially designed welding tooling fixture to ensure that it will not shift during the welding process. At the same time, the relative position of the spiral band 4 and the heat exchange tube 1 is adjusted by a precise positioning device to ensure that the two fit tightly together and the welding gap is controlled within a suitable range (generally not exceeding 1mm) to ensure smooth welding.

[0042] (2) Positioning welding steps

[0043] A low-energy-density laser beam is used for positioning welding along the predetermined welding start position between the heat exchanger tube 1 and the spiral ribbon 4. The spacing of the positioning weld points is determined based on factors such as the diameter of the heat exchanger tube 1, the length and stiffness of the spiral ribbon 4, and is generally set at a specific interval of mm. The purpose of positioning welding is to initially fix the spiral ribbon 4 to the surface of the heat exchanger tube 1, prevent relative displacement during subsequent continuous welding, and ensure the accuracy and stability of the welding.

[0044] (3) Continuous welding steps

[0045] Following a pre-planned welding path, heat exchanger tube 1 and spiral band 4 are continuously welded using optimized laser welding parameters. Starting from the positioning weld point, the laser welding equipment is activated, and the laser beam moves uniformly along the joint. During the welding process, the welding quality is monitored in real time. By observing the weld formation and the state of the molten pool, welding parameters such as laser power and welding speed are adjusted promptly to ensure a uniform, continuous weld free of defects such as porosity and cracks. Simultaneously, an inert gas is used to protect the welding area, preventing weld oxidation and improving weld quality and performance.

[0046] (4) Post-welding treatment steps

[0047] Visual inspection and cleaning: After welding, first perform a visual inspection of heat exchange tube 1 to observe whether there are defects such as spatter and burrs on the weld surface. Use special tools to clean the weld surface to remove these impurities and make the weld surface smooth and flat.

[0048] Non-destructive testing and repair: Non-destructive testing methods, such as ultrasonic testing and X-ray testing, are used to detect internal defects in the weld. For defects such as porosity and incomplete penetration, corresponding repair plans are developed based on the type and location of the defects, and repair methods such as filler welding are used to ensure that the weld quality meets the requirements.

[0049] Stress relief treatment: In order to eliminate residual stress generated during the welding process and improve the overall performance of heat exchange tube 1, stress relief treatment is performed on the welded heat exchange tube 1. Heat treatment can be used, heating the heat exchange tube 1 to an appropriate temperature (generally 260℃) and holding it for a certain time (0.3 hours), then slowly cooling it to effectively reduce residual stress and improve the fatigue resistance and service life of the heat exchange tube 1.

[0050] One example:

[0051] Material preparation

[0052] High-strength steel pipe with an outer diameter of 50mm and a wall thickness of 3mm is selected as the heat exchange tube 1. The spiral strip 4 is made of aluminum alloy strip with a thickness of 1mm, and its shape is spiral with a width of 20mm.

[0053] Welding preparation

[0054] Surface treatment: Use acetone to clean the steel pipe and aluminum alloy spiral belt 4 to remove surface oil stains, and then use sandpaper to polish the welded surface to remove the oxide layer and expose the metallic luster.

[0055] Equipment parameter adjustment: Based on the material properties, the parameters of the laser welding equipment are set as follows: laser power 1500W, pulse frequency 20Hz, welding speed 1.5m / min, and spot diameter 0.8mm.

[0056] Tooling and positioning: Place the steel pipe on the welding tooling fixture, and use the positioning device to tightly wrap the spiral aluminum alloy spiral strip 4 around the surface of the steel pipe. Adjust the position of the two to control the welding gap to about 0.1mm.

[0057] Position welding

[0058] A low-energy-density laser beam (laser power of 800W) is used to perform positioning welding every 50mm along the joint line between the steel pipe and the spiral band 4. The diameter of the positioning weld is about 1mm, and the welding time is 0.5s.

[0059] Continuous welding

[0060] Following the set welding path, the steel pipe and spiral band 4 are continuously welded starting from the positioning weld point with a laser power of 1500W, a pulse frequency of 20Hz, and a welding speed of 1.5m / min. During the welding process, argon gas is used as the protective gas with a gas flow rate of 15L / min to prevent weld oxidation.

[0061] Post-welding treatment

[0062] Visual inspection and cleaning: After welding, the heat exchange tube 1 was visually inspected and a small amount of spatter was found on the weld surface. Sandpaper was used to polish and clean the weld surface to make it smooth.

[0063] Non-destructive testing and repair: Ultrasonic testing was used to inspect the weld, revealing a minor porosity defect. Repair was performed by welding, with the laser power adjusted to 1200W and the welding speed to 1m / min. After welding, a second inspection confirmed the defect was eliminated.

[0064] Stress relief treatment: The welded heat exchanger tube 1 is placed in a heat treatment furnace, heated to 550℃, held for 2 hours, and then slowly cooled with the furnace to complete the stress relief treatment.

[0065] Heat exchanger manufacturing

[0066] The high-fin heat exchange tubes 1, after the above treatment, are arranged and assembled according to the design requirements, and then welded and connected to the heat exchanger's shell, end caps, pipes, and other components to finally manufacture a compressed air heat exchanger. Testing showed that this heat exchanger's heat exchange efficiency is 50% higher than that of traditional heat exchangers, and its manufacturing cost is reduced by 25%, meeting the actual usage requirements of compressed air energy storage systems.

[0067] The above embodiments are only used to illustrate the present utility model and are not intended to limit the technical solutions described in the present utility model. Although the present utility model has been described in detail with reference to the above embodiments, the present utility model is not limited to the specific embodiments described above. Therefore, any modifications or equivalent substitutions to the present utility model, and all technical solutions and improvements that do not depart from the spirit and scope of the utility model, are covered within the scope of the claims of the present utility model.

Claims

1. A laser-welded finned tube for a compressed air heat exchanger, comprising a heat exchange tube (1), characterized in that, The outer end of the heat exchange tube (1) is provided with a spiral band (4), and a laser welding point (3) is provided between the spiral band (4) and the heat exchange tube (1). The outer end of the heat exchange tube (1) is wrapped with an air heat exchanger (2).

2. The laser-welded finned tube for a compressed air heat exchanger according to claim 1, characterized in that, The base material of the heat exchange tube (1) is a high-strength steel tube.

3. A laser-welded finned tube for a compressed air heat exchanger according to claim 1, characterized in that, The spiral ribbon (4) is made of a metal material with good thermal conductivity.

4. A laser-welded finned tube for a compressed air heat exchanger according to claim 1, characterized in that, The welding steps of the laser welding point (3) are as follows: S1. Welding preparation steps: Clean the surface of the heat exchange tube (1) and the spiral strip (4) to remove impurities such as oil and oxide layer; adjust the parameters of the laser welding equipment, including laser power, pulse frequency, welding speed, and spot diameter; fix the heat exchange tube (1) on the welding fixture and adjust the relative position of the spiral strip (4) and the heat exchange tube (1) to ensure that the two are tightly fitted and the welding gap meets the requirements. S2, Positioning Welding Step: Using a low energy density laser beam, position welding is performed along the predetermined welding start position of the heat exchange tube (1) and the spiral strip (4). Positioning welding points are set at certain intervals to initially fix the spiral strip (4) on the surface of the heat exchange tube (1) to prevent displacement during the formal welding process. S3. Continuous welding steps: According to the set welding path, the heat exchange tube (1) and the spiral strip (4) are continuously welded with optimized laser welding parameters. Starting from the positioning welding point, the laser beam moves at a constant speed along the joint of the two to ensure that the weld is uniform and continuous. The welding quality is monitored in real time during the welding process, and the welding parameters are adjusted in a timely manner. S4. Post-welding treatment steps: Visually inspect the completed heat exchange tube (1) to remove spatter and burrs from the weld surface; use non-destructive testing methods to detect internal defects in the weld and repair any detected defects; perform stress relief treatment on the heat exchange tube (1) to improve its overall performance.

Images