A laser surface texturing processing method for defrosting the surface of air cooler fins

Abstract

This invention relates to the field of air coolers, specifically disclosing a laser surface texture processing method for defrosting the surface of air cooler fins. The method involves sequentially grinding and mechanically polishing a 6061 aluminum alloy fin substrate to remove the surface oxide layer and metal debris, followed by ultrasonic cleaning with anhydrous ethanol for 20 minutes and cold air drying to obtain a pre-treated substrate. A nanosecond laser processing system is used to programmatically scan the surface of the pre-treated substrate to prepare a continuously and regularly arranged hexagonal honeycomb micron-level texture. This hexagonal honeycomb micron-level texture includes micron-level raised platforms and recessed grooves, which are interconnected to form a microchannel network. This method can construct specific multi-level micro-nano textures on the fin surface, effectively reducing the contact area between ice nuclei and the substrate, delaying frost formation, significantly extending the defrosting cycle of the air cooler, and reducing the frequency of defrosting operations to lower overall energy consumption. The microchannel network formed by the texture allows for rapid drainage of defrost water, avoiding secondary frost problems caused by residual defrost water.

Description

Technical Field

[0001] This invention relates to the field of air cooler technology, and in particular to a laser surface texture processing method for defrosting the surface of air cooler fins. Background Technology

[0002] Air coolers are the core heat exchange equipment at the end of refrigeration systems. Their operating efficiency determines the energy efficiency level of related systems such as cold chain logistics and industrial refrigeration. With the advancement of energy conservation and consumption reduction goals, the refrigeration industry has put forward higher requirements for the high efficiency and energy saving of heat exchangers.

[0003] Aluminum alloys have become the mainstream material for manufacturing fins of air coolers due to their excellent thermal conductivity, low density, and good machinability. When air coolers are running at low temperatures, frost easily forms on the surface of the fins, which restricts their energy efficiency. The frost layer will significantly reduce heat exchange efficiency and increase fan energy consumption. Existing defrosting solutions are prone to causing temperature fluctuations in the storage room and will also shorten the effective working time of the equipment.

[0004] Laser surface texturing, as a green precision processing method, has advantages such as controllable structure, integration with substrate, and environmental friendliness when constructing micro-nano morphologies on material surfaces. However, single nanosecond laser processing can only form micron-level rough structures, which are prone to forming ice nuclei due to capillary effects, and cannot achieve the ideal anti-frost effect. Therefore, a processing method that can prepare multi-level micro-nano textures on the fin surface is needed. Summary of the Invention

[0005] The purpose of this invention is to provide a laser surface texture processing method for defrosting the surface of air cooler fins, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a laser surface texture processing method for defrosting the surface of air cooler fins, wherein the specific steps of the laser surface texture processing method for defrosting the surface of air cooler fins are as follows: S1 substrate pretreatment: 6061 aluminum alloy fin substrate is ground and mechanically polished in sequence to remove surface oxide layer and metal debris, and then ultrasonically cleaned in anhydrous ethanol for 20 minutes and dried with cold air to obtain pretreated substrate. S2 primary texture preparation: A nanosecond laser processing system is used to programmatically scan the surface of a pretreated substrate to prepare a continuous and regularly arranged hexagonal honeycomb micron-level texture. The hexagonal honeycomb micron-level texture is provided with micron-level raised platforms and recessed grooves, and the grooves are interconnected to form a microchannel network. S3 secondary texture preparation involves immersing a substrate with primary texture in an etchant for 10-30 seconds to form a submicron-level secondary texture inside the trenches and on the surface of the raised platforms. The substrate is then cleaned with anhydrous ethanol and dried with cold air. S4 surface functionalization modification involves dispersing hydrophilic or hydrophobic nano-SiO2 in an alcohol-based organic solvent to form a dispersion, and then coating the dispersion onto the substrate surface using a coating process to obtain a functional heat dissipation surface for air cooler fins with controllable hydrophilicity and hydrophobicity.

[0007] Preferably, the laser used in the nanosecond laser processing system in step S2 is a fiber laser with a laser output wavelength of 1064nm, a laser beam spot diameter of 20μm, a laser scanning processing path filling spacing of 1μm and 0.5μm, a laser processing system on-time delay parameter of 50ms, an on-time delay parameter of 20ms, a corner delay parameter of 20ms, a laser pulse width of 100ns, and a single-beam laser output energy of 2 microjoules.

[0008] Preferably, the nanosecond laser processing parameters in step S2 are: laser scanning speed of 400-600 mm / s, laser processing pulse frequency of 20 kHz, and laser output power of 10-20 W. The prepared hexagonal honeycomb micron-scale textured unit has a side length of 50μm-200μm, a groove depth of 10μm-20μm, an inscribed circle diameter of 150μm-500μm, and a groove width of 30μm±5μm. The coverage of the microchannel network on the surface of the 6061 aluminum alloy fin substrate matches the laser scanning path.

[0009] Preferably, during the first-level textured laser processing in step S2, the 6061 aluminum alloy fin sample to be processed is horizontally fixed on the processing platform, the processing surface of the sample is positioned above the laser focal plane, and the vertical distance between the processing surface of the sample and the laser focal plane is 1.1 mm.

[0010] When the filling path spacing of the laser scanning process is 1 μm, the ratio of processing speed to pulse frequency is 0.5-1.25; when the filling path spacing is 0.5 μm, the ratio of processing speed to pulse frequency is 2.5-3.75.

[0011] Preferably, the corrosive agent used in step S3 is an alkaline corrosive solution or a mixed acid corrosive solution; The alkaline corrosion solution is a 4wt% NaOH aqueous solution, and the mixed acid corrosion solution is prepared by mixing 40% hydrofluoric acid, 65% nitric acid and deionized water in a volume ratio of 1:3:10. The secondary texture formed by the corrosion is an irregular cellular or pit-like micromorphology. The characteristic size of the secondary texture is 100nm-500nm. The secondary texture is uniformly distributed on the inner wall of the groove and the surface of the raised platform of the primary texture.

[0012] Preferably, in step S3, anhydrous ethanol is used to clean the corroded 6061 aluminum alloy fin substrate, and the cleaning method is ultrasonic cleaning or immersion cleaning. The cleaning time is no less than 3 minutes. The cleaning removes residual ionic impurities on the fin surface. The impurities removed by etching with a 4wt% NaOH aqueous solution include Na+, AlO2- and OH-. The impurities removed by etching with a mixed acid solution include fluoride ions, nitrate ions and other acid etching byproducts. After cleaning, the fins are dried quickly with cold air.

[0013] Preferably, the alcohol-based organic solvent used in step S4 is anhydrous ethanol or isopropanol. The nano-SiO2 is a hydrophilic nano-SiO2 or a hydrophobic nano-SiO2 that has undergone surface modification. The nano-SiO2 is dispersed in an alcohol-based organic solvent by ultrasonic dispersion for a period of not less than 10 minutes to form a uniform dispersion without agglomeration. The coating process is one of spraying, dipping, or spin coating, and the dispersion liquid uniformly covers the entire heat dissipation surface of the 6061 aluminum alloy fins and the inside of the grooves of the multi-level micro-nano texture.

[0014] Preferably, the hydrophobic nano-SiO2 is nano-SiO2 particles modified with perfluorooctyltriethoxysilane. The nano-SiO2 particles have a particle size of 30 nm, and the mass fraction of the dispersion formed by the hydrophobic nano-SiO2 in an alcohol-based organic solvent is 2%.

[0015] Preferably, the spraying pressure of the spraying method is 0.3-0.5MPa, the vertical distance between the spray gun and the processed surface of the 6061 aluminum alloy fin is 15-20cm, and a reciprocating spraying method is adopted. After the aluminum alloy fins are coated, the fin substrate is placed in a constant temperature oven for curing. The curing temperature is 80°C and the curing time is 1 hour. After curing, it is naturally cooled to room temperature. The static water contact angle of the modified fin heat dissipation surface is greater than 150°, which is a superhydrophobic state.

[0016] Preferably, in step S1, the surface of the 6061 aluminum alloy fin substrate is dry-ground sequentially with silicon carbide sandpaper of 400 grit, 800 grit and 1500 grit, until there are no obvious scratches on the substrate surface, and then mechanically polished until the substrate surface is mirror-like. In step S3, when a 4wt% NaOH aqueous solution is used for corrosion, the corrosion time is 10s; when a mixed acid solution is used for corrosion, the corrosion time is 12s.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention can construct specific multi-level micro-nano textures on the surface of fins, effectively reducing the contact area between ice nuclei and the substrate, delaying frost formation and significantly extending the defrosting cycle of the air cooler, reducing the frequency of defrosting operations to lower overall energy consumption; the microchannel network formed by the texture can realize the rapid flow and discharge of defrosting water, avoiding the problem of secondary frost caused by defrosting water residue, and improving the defrosting effect and operational stability of the air cooler.

[0018] 2. The multi-level micro-nano composite structure prepared by this invention significantly increases the effective heat exchange area of ​​the fins. At the same time, the micro-nano rough structure can induce local micro-eddies in the fluid, destroy the thermal boundary layer near the fin wall, enhance the convective heat transfer performance of the gas-solid interface, and significantly improve the overall heat exchange efficiency of the air cooler, which meets the needs of the refrigeration industry for high efficiency development.

[0019] 3. The multi-level micro-nano texture of the present invention is directly constructed on the surface of the fin substrate, forming an integrated structure with the substrate. It has extremely high mechanical strength, wear resistance and corrosion resistance. Compared with the traditional chemical coating treatment method, the structural stability and durability are greatly improved. Even if there is a small loss of the surface nano-modified particles, the bottom micro-nano skeleton can still maintain good physical anti-frost performance, significantly extending the service life of the fin and reducing the later maintenance and replacement costs of the equipment.

[0020] 4. This invention employs a process that couples nanosecond laser processing with chemical etching, combining the high efficiency and precision of laser processing with the batch processing advantages of chemical etching. It improves production efficiency while ensuring processing accuracy, and the processing flow is simple and controllable, making it suitable for large-scale industrial applications. Furthermore, the processing does not damage the overall mechanical strength of the fins and has good adaptability to complex-shaped heat dissipation surfaces, making it widely applicable and able to meet the processing needs of fins for air coolers with different structures. Attached Figure Description

[0021] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 This is a flowchart of the operation process of the present invention; Figure 2 This refers to the multi-level micro / nano textured surface prepared according to the present invention; Figure 3 This is an optical microscope image of the multi-level micro / nano textured surface prepared in this invention; Figure 4 This is a three-dimensional structure diagram of the multi-level micro / nano textured surface prepared in this invention; Figure 5 This is a scanning electron microscope image of the multi-level texture of the surface prepared in this invention. Detailed Implementation

[0023] 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.

[0024] Please see Figure 1 This invention provides a technical solution: Example 1: A laser surface texture processing method for defrosting the surface of air cooler fins, comprising the following steps: S1 substrate pretreatment: The 6061 aluminum alloy fin substrate is successively ground and mechanically polished to remove the surface oxide layer and metal debris. After that, it is ultrasonically cleaned with anhydrous ethanol for 20 minutes and dried with cold air to obtain the pretreated substrate. Grinding is carried out by dry grinding with silicon carbide sandpaper of 400 grit, 800 grit and 1500 grit in sequence until there are no obvious scratches on the surface of the substrate. Then, mechanical polishing is performed until the surface of the substrate is mirror-like to ensure uniform laser energy absorption.

[0025] The S2 primary texture preparation employs a nanosecond laser processing system to programmatically scan the surface of a pretreated substrate, preparing a continuous and regularly arranged hexagonal honeycomb micron-level texture. The hexagonal honeycomb micron-level texture features micron-level raised platforms and recessed grooves, which are interconnected to form a microchannel network. During processing, the 6061 aluminum alloy fin sample to be processed is horizontally fixed on the processing platform, with the processing surface of the sample positioned above the laser focal plane. The vertical distance between the processing surface of the sample and the laser focal plane is 1.1 mm.

[0026] S3 secondary texture preparation involves immersing the substrate with primary texture in an etchant for 10 seconds to form submicron-level secondary textures inside the grooves and on the surface of the raised platforms. The substrate is then cleaned with anhydrous ethanol and dried with cold air. Ultrasonic cleaning is used for 3 minutes to thoroughly remove residual ionic impurities from the fin surface.

[0027] S4 surface functionalization modification involves dispersing hydrophobic nano-SiO2 in an alcohol-based organic solvent to form a dispersion, and then coating the dispersion onto the substrate surface using a coating process to obtain a functional heat dissipation surface for air cooler fins with controllable hydrophilicity and hydrophobicity. The nano-SiO2 is dispersed in the alcohol-based organic solvent using ultrasonic dispersion to ensure the formation of a uniform dispersion without agglomeration.

[0028] The laser used in the nanosecond laser processing system in step S2 is a fiber laser with a laser output wavelength of 1064nm, a laser beam spot diameter of 20μm, a path filling spacing of 1μm and 0.5μm, an on-time delay parameter of 50ms, an off-time delay parameter of 20ms, a corner delay parameter of 20ms, a laser pulse width of 100ns, and a single-beam laser output energy of 2μm. During the laser scanning process, the path filling spacing is uniform to ensure consistent fabric formation.

[0029] In step S2, the nanosecond laser processing parameters are as follows: laser scanning speed of 400 mm / s, laser processing pulse frequency of 20 kHz, laser output power of 10 W, the side length of the prepared hexagonal honeycomb micron-scale textured unit is 50 μm, the depth of the recessed groove is 10 μm, the diameter of the inscribed circle of the hexagonal honeycomb texture is 150 μm, the width of the recessed groove is 25 μm, and the coverage of the microfluidic network on the surface of the 6061 aluminum alloy fin substrate matches the laser scanning path; the transition between the raised platforms and the recessed grooves of the texture is smooth, without sharp edges.

[0030] In step S2, when the filling path spacing of the laser scanning process is 1 μm, the ratio of processing speed to pulse frequency is 0.5. When the filling path spacing is 0.5 μm, the ratio of processing speed to pulse frequency is 2.5. By precisely controlling the ratio, the coverage density of the laser spot on the substrate surface is ensured to be uniform, avoiding situations where the local energy is too high or too low.

[0031] The etchant used in step S3 is an alkaline etching solution, which is a 4wt% NaOH aqueous solution. The secondary texture formed by etching is an irregular cellular micromorphology with a characteristic size of 100nm. The secondary texture is uniformly distributed on the inner wall of the groove and the surface of the raised platform of the primary texture. During the etching process, the substrate is completely immersed in the etchant, and no bubbles adhere to the surface.

[0032] In step S3, anhydrous ethanol is used to clean the corroded 6061 aluminum alloy fin substrate to remove residual Na from the fin surface. + AlO2 - and OH - After cleaning, the substrate is dried quickly with cold air, leaving no moisture residue on the surface and avoiding any impact on subsequent functional modification effects.

[0033] The alcohol-based organic solvent used in step S4 is anhydrous ethanol, and the nano-SiO2 is a surface-modified hydrophobic nano-SiO2. 2，The ultrasonic dispersion time is 10 minutes to form a uniform dispersion without agglomeration. The coating process is spraying. The dispersion evenly covers the entire heat dissipation surface of the 6061 aluminum alloy fins and the inside of the grooves of the multi-level micro-nano texture. During the spraying process, the spray gun is kept moving at a uniform speed to ensure that the coating thickness is consistent.

[0034] The hydrophobic nano-SiO2 is nano-SiO2 particles modified with perfluorooctyltriethoxysilane. The particle size of the nano-SiO2 particles is 30 nm. The mass fraction of the dispersion formed by the hydrophobic nano-SiO2 in an alcohol organic solvent is 2%. The modified nano-SiO2 particles are hydrophobic and stable and do not easily agglomerate.

[0035] The spraying pressure was 0.3 MPa, and the vertical distance between the spray gun and the 6061 aluminum alloy fin processing surface was 15 cm. A reciprocating spraying method was used. After the aluminum alloy fins were sprayed, the fin substrate was placed in a constant temperature oven for curing. The curing temperature was 80℃ and the curing time was 1 hour. After curing, the fins were allowed to cool naturally to room temperature. The static water contact angle of the modified fin heat dissipation surface was greater than 150°, indicating a superhydrophobic state. The temperature inside the oven was uniform during the curing process to avoid local overheating that could lead to coating failure.

[0036] In step S1, the surface of the 6061 aluminum alloy fin substrate is dry-ground sequentially using silicon carbide sandpaper with grits of 400 grit, 800 grit, and 1500 grit. After grinding until there are no obvious scratches on the substrate surface, mechanical polishing is performed until the substrate surface is mirror-like. In step S3, when etching is performed using a 4wt% NaOH aqueous solution, the etching time is 10s. The etching time is strictly controlled to avoid excessive etching that could damage the primary texture structure.

[0037] Example 2: A laser surface texture processing method for defrosting the surface of air cooler fins, comprising the following steps: S1 substrate pretreatment involves grinding and mechanically polishing the 6061 aluminum alloy fin substrate sequentially to remove the surface oxide layer and metal debris. After removal, the substrate is ultrasonically cleaned with anhydrous ethanol for 20 minutes and then dried with cold air to obtain the pretreated substrate. During the grinding process, uniform force is applied, and the surface is gradually refined using silicon carbide sandpaper with grits of 400, 800, and 1500. After mechanical polishing, the surface roughness of the substrate is extremely low, ensuring the precision of laser processing.

[0038] The S2 primary texture preparation uses a nanosecond laser processing system to programmatically scan the surface of a pretreated substrate to prepare a continuous and regularly arranged hexagonal honeycomb micron-level texture. The hexagonal honeycomb micron-level texture has micron-level raised platforms and recessed grooves, and the grooves are interconnected to form a microchannel network. The laser processing system is calibrated before processing to ensure that the scanning path is accurate.

[0039] S3 secondary texture preparation involves immersing a substrate with primary texture in an etchant for 20 seconds to form submicron-level secondary textures inside the grooves and on the surface of the raised platforms. The substrate is then cleaned with anhydrous ethanol and dried with cold air. The changes on the substrate surface are observed in real time during the etching process to ensure that the secondary texture forming effect meets expectations.

[0040] S4 surface functionalization modification involves dispersing hydrophobic nano-SiO2 in an alcohol-based organic solvent to form a dispersion, which is then coated onto the substrate surface to obtain a functional heat dissipation surface for air cooler fins with controllable hydrophilicity and hydrophobicity. The dispersion is thoroughly stirred during preparation to ensure uniform dispersion of nanoparticles.

[0041] The laser used in the nanosecond laser processing system in step S2 is a fiber laser with a laser output wavelength of 1064nm, a laser beam spot diameter of 20μm, a laser scanning processing path filling spacing of 1μm and 0.5μm, a laser processing system on-time delay parameter of 50ms, an off-time delay parameter of 20ms, a corner delay parameter of 20ms, a laser pulse width of 100ns, and a single laser beam output energy of 2μm; the laser output energy is stable with no obvious fluctuations.

[0042] In step S2, the nanosecond laser processing parameters are as follows: laser scanning speed of 500 mm / s, laser processing pulse frequency of 20 kHz, laser output power of 15 W, the side length of the prepared hexagonal honeycomb micron-scale textured unit is 125 μm, the depth of the recessed groove is 15 μm, the diameter of the inscribed circle of the hexagonal honeycomb texture is 325 μm, the width of the recessed groove is 30 μm, the coverage of the microchannel network on the surface of the 6061 aluminum alloy fin substrate matches the laser scanning path; the texture is neatly arranged without skewing or misalignment.

[0043] In step S2, during the first-level texture laser processing, the 6061 aluminum alloy fin sample to be processed is horizontally fixed on the processing platform, and the processing surface of the sample is positioned above the laser focal plane. The vertical distance between the processing surface of the sample and the laser focal plane is 1.1 mm. When the filling path spacing of the laser scanning processing is 1 μm, the ratio of processing speed to pulse frequency is 0.8. When the filling path spacing is 0.5 μm, the ratio of processing speed to pulse frequency is 3.0. The ratio setting makes the groove width and depth ratio of the texture coordinated, which is conducive to fluid flow.

[0044] The etchant used in step S3 is a mixed acid etching solution. The mixed acid etching solution is prepared by mixing 40% hydrofluoric acid, 65% nitric acid and deionized water in a volume ratio of 1:3:10. During preparation, the components are added in sequence and stirred at a uniform speed until they are mixed evenly. The secondary texture formed by etching is an irregular pit-shaped micromorphology. The characteristic size of the secondary texture is 300 nm. The secondary texture is evenly distributed on the inner wall of the groove and the surface of the raised platform of the primary texture.

[0045] In step S3, anhydrous ethanol is used to clean the corroded 6061 aluminum alloy fin substrate by immersion cleaning. The cleaning time is 4 minutes. The cleaning removes residual fluoride ions, nitrate ions and other acid etching reaction byproducts from the fin surface. After cleaning, cold air is used for rapid drying. During the immersion process, the substrate is turned over regularly to ensure that all surfaces are effectively cleaned.

[0046] The alcohol-based organic solvent used in step S4 is isopropanol, and the nano-SiO2 is a surface-modified hydrophobic nano-SiO2. 2， Nano-SiO2 was dispersed in an alcohol-based organic solvent using ultrasonic dispersion for 12 minutes to form a uniform dispersion without agglomeration. The coating process was an immersion method, in which the dispersion uniformly covered the entire heat dissipation surface of the 6061 aluminum alloy fins and the interior of the grooves of the multi-level micro-nano texture. The immersion time was reasonably controlled to ensure that the dispersion fully penetrated into the texture grooves.

[0047] The hydrophobic nano-SiO2 is nano-SiO2 particles modified with perfluorooctyltriethoxysilane. The particle size of the nano-SiO2 particles is 30 nm. The mass fraction of the dispersion formed by the hydrophobic nano-SiO2 in an alcohol organic solvent is 2%. The dispersion has good stability and no precipitation occurs after standing for a period of time.

[0048] After being coated by immersion, the aluminum alloy fins are placed in a constant temperature oven for curing at 80°C for 1 hour. After curing, they are naturally cooled to room temperature. The static water contact angle of the modified fin heat dissipation surface is greater than 150°, which is a superhydrophobic state. The cooling process is carried out slowly to avoid the coating cracking caused by sudden temperature changes.

[0049] In step S1, the surface of the 6061 aluminum alloy fin substrate is dry-ground sequentially using 400-grit, 800-grit, and 1500-grit silicon carbide sandpaper. After grinding until there are no obvious scratches on the substrate surface, mechanical polishing is performed until the substrate surface is mirror-like. In step S3, when using a mixed acid solution for etching, the etching time is 12 seconds. After etching, the substrate surface is free of defects such as corrosion pits and cracks.

[0050] Example 3: A laser surface texture processing method for defrosting the surface of air cooler fins, comprising the following steps: S1 substrate pretreatment involves grinding and mechanically polishing the 6061 aluminum alloy fin substrate sequentially to remove the surface oxide layer and metal debris. After removal, the substrate is ultrasonically cleaned with anhydrous ethanol for 20 minutes and then dried with cold air to obtain the pretreated substrate. The grinding and polishing processes are strictly controlled to ensure that the substrate surface is flat and smooth with no oxide layer residue, providing a good foundation for subsequent laser processing.

[0051] The S2 primary texture preparation uses a nanosecond laser processing system to programmatically scan the surface of a pretreated substrate to prepare a continuous and regularly arranged hexagonal honeycomb micron-level texture. The hexagonal honeycomb micron-level texture has micron-level raised platforms and recessed grooves. The grooves are interconnected to form a microchannel network. The substrate is positioned and fixed before laser processing to prevent the substrate from shifting during processing.

[0052] S3 secondary texture preparation involves immersing a substrate with primary texture in an etchant for 30 seconds to form a submicron-level secondary texture inside the trenches and on the surface of the raised platform. The substrate is then cleaned with anhydrous ethanol and dried with cold air. The etched secondary texture is tightly bonded to the primary texture, with no risk of detachment.

[0053] S4 surface functionalization modification involves dispersing hydrophilic nano-SiO2 in an alcohol-based organic solvent to form a dispersion, and then coating the dispersion onto the substrate surface to obtain a functional heat dissipation surface for air cooler fins with controllable hydrophilicity and hydrophobicity. The coated functional layer is firmly bonded to the substrate and is not easily worn.

[0054] The laser used in the nanosecond laser processing system in step S2 is a fiber laser with a laser output wavelength of 1064nm, a laser beam spot diameter of 20μm, a laser scanning processing path filling spacing of 1μm and 0.5μm, a laser processing system on-time delay parameter of 50ms, off-time delay parameter of 20ms, corner delay parameter of 20ms, laser pulse width of 100ns, single-beam laser output energy of 2μm, and precise laser beam focusing and good spot quality, ensuring the accuracy of texture processing.

[0055] In step S2, the nanosecond laser processing parameters are as follows: laser scanning speed of 600 mm / s, laser processing pulse frequency of 20 kHz, laser output power of 20 W, the side length of the prepared hexagonal honeycomb micron-scale textured unit is 200 μm, the depth of the recessed groove is 20 μm, the diameter of the inscribed circle of the hexagonal honeycomb texture is 500 μm, the width of the recessed groove is 35 μm, the coverage of the microfluidic network on the surface of the 6061 aluminum alloy fin substrate matches the laser scanning path, and the microfluidic network of the texture is unobstructed without blockage.

[0056] In step S2, during the first-level texture laser processing, the 6061 aluminum alloy fin sample to be processed is horizontally fixed on the processing platform. The processing surface of the sample is positioned above the laser focal plane, and the vertical distance between the processing surface of the sample and the laser focal plane is 1.1 mm. When the filling path spacing of the laser scanning processing is 1 μm, the ratio of processing speed to pulse frequency is 1.25. When the filling path spacing is 0.5 μm, the ratio of processing speed to pulse frequency is 3.75. By optimizing the ratio, efficient and precise processing of the texture is achieved.

[0057] The etchant used in step S3 is an alkaline etching solution, which is a 4wt% NaOH aqueous solution. The secondary texture formed by etching is an irregular cellular micromorphology with a characteristic size of 500 nm. The secondary texture is uniformly distributed on the inner wall of the groove and the surface of the raised platform of the primary texture. The morphology of the secondary texture after etching is regular and there is no obvious agglomeration.

[0058] In step S3, anhydrous ethanol is used to clean the corroded 6061 aluminum alloy fin substrate using ultrasonic cleaning for 5 minutes to remove residual Na from the fin surface. + AlO2 - and OH - After cleaning, use cold air for rapid drying. During the cleaning process, use moderate ultrasonic power to avoid damaging the texture structure.

[0059] The alcohol-based organic solvent used in step S4 is anhydrous ethanol, and the nano-SiO2 is hydrophilic nano-SiO2 that has undergone surface modification. The nano-SiO2 is dispersed in the alcohol-based organic solvent by ultrasonic dispersion for 15 minutes to form a uniform dispersion without agglomeration.

[0060] The coating process is spin coating. The dispersion evenly covers the entire heat dissipation surface of the 6061 aluminum alloy fins and the inside of the grooves of the multi-level micro-nano texture. The substrate rotation speed is stable during spin coating to ensure uniform coating thickness. The hydrophilic nano-SiO2 is nano-SiO2 particles with a particle size of 30nm after surface modification treatment. The amount of nano-SiO2 added is strictly controlled during the preparation of the dispersion to ensure uniform dispersion concentration.

[0061] After spin coating, the fin substrate is placed in a constant temperature oven for curing at 80°C for 1 hour. After curing, it is naturally cooled to room temperature. The modified fin heat dissipation surface has good hydrophilicity, and the cured functional layer has a uniform texture without defects such as bubbles or cracks.

[0062] In step S1, the surface of the 6061 aluminum alloy fin substrate is dry-ground sequentially using 400-grit, 800-grit, and 1500-grit silicon carbide sandpaper until there are no obvious scratches on the substrate surface. Then, it is mechanically polished until the substrate surface is mirror-like. In step S3, when 4wt% NaOH aqueous solution is used for etching, the etching time is 10s. During the entire processing, the substrate does not deform or break and maintains good mechanical properties.

[0063] Comparative Example 1 lacks the secondary texture preparation step.

[0064] S1 Substrate Pretreatment: The parameters are the same as in Example 2, and a pretreated substrate is obtained.

[0065] S2 Primary Texture Preparation: The parameters are the same as in Example 2, forming a hexagonal honeycomb micron-scale texture.

[0066] S3 Surface Functional Modification: The parameters are the same as in Example 2. The primary texture is directly modified with hydrophobicity, and there is no secondary texture.

[0067] Comparative Example 2: Missing surface functionalization modification steps.

[0068] S1 Substrate Pretreatment: Parameters are the same as in Example 2.

[0069] S2 primary texture preparation: parameters are the same as in Example 2.

[0070] S3 secondary texture preparation: The parameters are the same as in Example 2. After forming a multi-level texture, the finished product is directly produced without nano-SiO2 modification.

[0071] Comparative Example 3: Single micron-scale texture with traditional coating modification.

[0072] S1 Substrate Pretreatment: Parameters are the same as in Example 2.

[0073] S2 Single Texture Fabrication: Laser processing of a single micron-level groove texture without hexagonal honeycomb array, with a groove depth of 15μm and a width of 30μm.

[0074] S3 Traditional Coating Modification: Commercially available fluorocarbon coating is applied and cured at 80℃ for 1 hour, replacing nano-SiO2 functional modification.

[0075] The test data for Examples 1 to 3 and Comparative Examples 1 to 3 are shown in Tables 1 and 2.

[0076] Table 1 – Test data for Examples 1-3 and Comparative Examples 1-3

[0077] Table 2 – Test data for Examples 1-3 and Comparative Examples 1-3

[0078] From the data table above, we can conclude that: (1) The static water contact angle of Examples 1 and 2 both exceeded 150°, the initial frosting time was up to 48 min, and the frost layer thickness was only 72-85 μm after continuous operation for 2 hours. The defrosting water residue rate was as low as 5%-8%, which was far superior to the comparative examples.

[0079] In contrast, Comparative Example 1 lacked a secondary texture, and Comparative Example 2 was not functionalized. Both had an initial frosting time of less than 30 minutes, a frost layer thickness more than twice that of the examples, and a defrosting residue rate as high as 25%-32%. This fully demonstrates that the coupled design of primary honeycomb texture, secondary submicron texture, and nano-functional modification can effectively reduce ice core adhesion, delay frosting, and at the same time enable rapid discharge of defrosting water through honeycomb microchannels.

[0080] (2) After wear resistance test, the contact angle of the embodiment remained above 145° and the performance retention rate was 92%-97% after 30 days of continuous use. However, the conventional fluorocarbon coating of Comparative Example 3, although the initial contact angle was close to that of the embodiment, the contact angle dropped to 115° after wear resistance test and the long-term stability was only 85%. This shows the structural advantages of the laser texture and the substrate integration in this invention, as well as the stronger adhesion of the nano SiO2 modification layer. Example 3 achieved a contact angle of 65° through hydrophilic modification, which meets the requirements of specific working conditions and demonstrates the flexible control of surface hydrophilicity and hydrophobicity of this method.

[0081] (3) The comparison results clearly show that the construction of secondary texture, the functionalization of nano-SiO2 and the design of hexagonal honeycomb multi-level texture are all key to achieving excellent anti-frost and high stability.

[0082] The absence of any one of the processes, or its replacement with a single texture plus a traditional coating, will lead to a significant decline in performance, further verifying the rationality and innovation of the technical solution of this invention.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A laser surface texture processing method for defrosting the surface of air cooler fins, characterized in that: The specific steps of the laser surface texture processing method for defrosting the surface of air cooler fins are as follows: S1 substrate pretreatment: 6061 aluminum alloy fin substrate is ground and mechanically polished in sequence to remove surface oxide layer and metal debris, and then ultrasonically cleaned in anhydrous ethanol for 20 minutes and dried with cold air to obtain pretreated substrate. S2 primary texture preparation: A nanosecond laser processing system is used to programmatically scan the surface of a pretreated substrate to prepare a continuous and regularly arranged hexagonal honeycomb micron-level texture. The hexagonal honeycomb micron-level texture is provided with micron-level raised platforms and recessed grooves, and the grooves are interconnected to form a microchannel network. S3 secondary texture preparation involves immersing a substrate with primary texture in an etchant for 10-30 seconds to form a submicron-level secondary texture inside the trenches and on the surface of the raised platforms. The substrate is then cleaned with anhydrous ethanol and dried with cold air. S4 surface functionalization modification involves dispersing hydrophilic or hydrophobic nano-SiO2 in an alcohol-based organic solvent to form a dispersion, and then coating the dispersion onto the substrate surface using a coating process to obtain a functional heat dissipation surface for air cooler fins with controllable hydrophilicity and hydrophobicity.

2. The laser surface texture processing method for defrosting the surface of air cooler fins according to claim 1, characterized in that: The laser used in the nanosecond laser processing system in step S2 is a fiber laser with a laser output wavelength of 1064nm, a laser beam spot diameter of 20μm, a laser scanning processing path filling spacing of 1μm and 0.5μm, a laser processing system on-time delay parameter of 50ms, an on-time delay parameter of 20ms, a corner delay parameter of 20ms, a laser pulse width of 100ns, and a single-beam laser output energy of 2 microjoules.

3. The laser surface texture processing method for defrosting the surface of air cooler fins according to claim 1, characterized in that: The nanosecond laser processing parameters in step S2 are: laser scanning speed of 400-600 mm / s, laser processing pulse frequency of 20 kHz, and laser output power of 10-20 W. The prepared hexagonal honeycomb micron-scale textured unit has a side length of 50μm-200μm, a groove depth of 10μm-20μm, an inscribed circle diameter of 150μm-500μm, and a groove width of 30μm±5μm. The coverage of the microchannel network on the surface of the 6061 aluminum alloy fin substrate matches the laser scanning path.

4. The laser surface texture processing method for defrosting the surface of air cooler fins according to claim 1, characterized in that: In step S2, when performing primary textured laser processing, the 6061 aluminum alloy fin sample to be processed is horizontally fixed on the processing platform, the processing surface of the sample is positioned above the laser focal plane, and the vertical distance between the processing surface of the sample and the laser focal plane is 1.1 mm. When the filling path spacing of the laser scanning process is 1 μm, the ratio of processing speed to pulse frequency is 0.5-1.25; when the filling path spacing is 0.5 μm, the ratio of processing speed to pulse frequency is 2.5-3.

75.

5. The laser surface texture processing method for defrosting the surface of air cooler fins according to claim 1, characterized in that: The corrosive agent used in step S3 is an alkaline corrosive solution or a mixed acid corrosive solution; The alkaline corrosion solution is a 4wt% NaOH aqueous solution, and the mixed acid corrosion solution is prepared by mixing 40% hydrofluoric acid, 65% nitric acid and deionized water in a volume ratio of 1:3:

10. The secondary texture formed by the corrosion is an irregular cellular or pit-like micromorphology. The characteristic size of the secondary texture is 100nm-500nm. The secondary texture is uniformly distributed on the inner wall of the groove and the surface of the raised platform of the primary texture.

6. The laser surface texture processing method for defrosting the surface of air cooler fins according to claim 5, characterized in that: In step S3, anhydrous ethanol is used to clean the corroded 6061 aluminum alloy fin substrate. The cleaning method is ultrasonic cleaning or immersion cleaning. The cleaning time is no less than 3 minutes. The cleaning removes residual ionic impurities on the fin surface. The impurities removed by etching with a 4wt% NaOH aqueous solution include Na+, AlO2- and OH-. The impurities removed by etching with a mixed acid solution include fluoride ions, nitrate ions and other acid etching byproducts. After cleaning, the fins are dried quickly with cold air.

7. The laser surface texture processing method for defrosting the surface of air cooler fins according to claim 1, characterized in that: The alcoholic organic solvent used in step S4 is anhydrous ethanol or isopropanol. The nano-SiO2 is a hydrophilic nano-SiO2 or a hydrophobic nano-SiO2 that has undergone surface modification. The nano-SiO2 is dispersed in an alcohol-based organic solvent by ultrasonic dispersion for a period of not less than 10 minutes to form a uniform dispersion without agglomeration. The coating process is one of spraying, dipping, or spin coating, and the dispersion liquid uniformly covers the entire heat dissipation surface of the 6061 aluminum alloy fins and the inside of the grooves of the multi-level micro-nano texture.

8. The laser surface texture processing method for defrosting the surface of air cooler fins according to claim 1, characterized in that: The hydrophobic nano-SiO2 is nano-SiO2 particles modified with perfluorooctyltriethoxysilane. The nano-SiO2 particles have a particle size of 30 nm, and the mass fraction of the dispersion formed by the hydrophobic nano-SiO2 in an alcohol-based organic solvent is 2%.

9. A laser surface texture processing method for defrosting the surface of air cooler fins according to claim 1, characterized in that: The spraying pressure of the spraying method is 0.3-0.5MPa, the vertical distance between the spray gun and the machined surface of the 6061 aluminum alloy fin is 15-20cm, and a reciprocating spraying method is adopted. After the aluminum alloy fins are coated, the fin substrate is placed in a constant temperature oven for curing. The curing temperature is 80°C and the curing time is 1 hour. After curing, it is naturally cooled to room temperature. The static water contact angle of the modified fin heat dissipation surface is greater than 150°, which is a superhydrophobic state.

10. A laser surface texture processing method for defrosting the surface of air cooler fins according to claim 1, characterized in that: In step S1, the surface of the 6061 aluminum alloy fin substrate is dry-ground sequentially with silicon carbide sandpaper of 400 grit, 800 grit and 1500 grit. After grinding until there are no obvious scratches on the substrate surface, mechanical polishing is performed until the substrate surface is mirror-like. In step S3, when a 4wt% NaOH aqueous solution is used for corrosion, the corrosion time is 10s; when a mixed acid solution is used for corrosion, the corrosion time is 12s.

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