A method for manufacturing microstructures on internal flow channel surfaces for enhanced overall heat transfer performance

Abstract

The application discloses a manufacturing method for enhancing the comprehensive heat exchange performance of an inner flow channel surface microstructure, and belongs to the fields of heat exchange enhancement and advanced manufacturing technology. First, the diameter and overhang angle of an inner flow channel of an active cooling component are extracted, a machining allowance and a residual height are determined, and the diameter of a tool is determined according to the diameter of the inner flow channel and the machining allowance. Second, based on the structural parameters of the inner flow channel, the characteristic parameters of the surface microstructure, the machining allowance, the diameter of the tool, the diameter of a blade circle, the avoidance diameter, the avoidance height and the collision clearance, additive and subtractive material alternating parameter calculation is carried out, additive and subtractive material composite manufacturing is realized, and the active cooling component with the target inner flow channel surface microstructure is obtained. Finally, heat exchange performance testing is carried out on the active cooling component, and comprehensive heat exchange performance evaluation is carried out according to a comprehensive cooling efficiency factor. The application can realize integrated manufacturing of the complex inner flow channel surface microstructure of the additive manufacturing active cooling component, improve the comprehensive cooling performance of the active cooling component, and has good popularization and application value.

Description

Technical Field

[0001] This invention belongs to the field of enhanced heat transfer and advanced manufacturing technology, and relates to a thermal manufacturing method for microstructures on the surface of internal flow channels to enhance overall heat transfer performance. Background Technology

[0002] Active cooling technology is a key technology for ensuring the safe operation of aircraft under high heat flux. With the continuous increase in aircraft speed, the thermal load on critical thermal protection components (such as the leading edge of the wing) is constantly increasing, placing higher demands on the overall cooling performance and reliability of active cooling components. Additive manufacturing technology has the ability to integrally form complex structures, overcoming the limitations of traditional processing methods in manufacturing complex internal flow channel structures, and providing a new technical approach to improve the heat transfer capacity of active cooling components. However, due to the influence of interlayer stacking methods and process parameters during additive manufacturing, the inner flow channel wall will form a rough surface with a certain degree of randomness. This type of surface morphology can increase the interaction between the fluid and the wall, promoting fluid turbulence in the near-wall region, thereby enhancing the heat transfer process; but at the same time, it will also change the flow state of the cooling medium, increasing flow resistance, leading to a contradiction between heat transfer enhancement and flow loss, thus limiting further improvement in the overall cooling performance of active cooling components. Therefore, regulating the surface of the additive manufacturing internal flow channel to form a surface microstructure that is conducive to fluid flow and heat transfer, thereby achieving synergistic optimization of coolant flow behavior and heat transfer behavior in the internal flow channel, is an effective way to improve the overall heat transfer performance of active cooling components.

[0003] The periodic surface microstructures in the processed internal flow channels can, on the one hand, increase the contact between the fluid and the solid wall, enhance wall disturbance, and disrupt the boundary layer, thereby strengthening heat transfer; on the other hand, the periodic surface microstructures can change the flow state of the coolant, achieving synergistic optimization between flow resistance and heat transfer performance. However, traditional processing methods are limited by the accessibility of the machining tools and the constraints of the machining path, making it difficult to process the surface morphology of the internal flow channels of additively manufactured active cooling components, which has become a key challenge restricting the performance improvement of additively manufactured active cooling components. Therefore, it is necessary to propose a method for manufacturing internal flow channel surface microstructures to enhance overall heat transfer performance. By adjusting the process parameters during the forming process, the surface microstructures of the internal flow channels can be controlled to form surface microstructures that are conducive to the flow of the cooling medium and heat transfer, thereby improving the overall heat transfer performance of the active cooling component.

[0004] Currently, some technologies have achieved enhanced heat transfer by altering the surface state and structure of the inner flow channel walls, but certain limitations remain. Chinese invention patent CN115164617B discloses a "multi-scale recessed channel heat exchanger and its manufacturing method." This technology uses multi-toothed flat-bottomed micro-milling cutters and multi-toothed ball-end micro-milling cutters to create recessed microchannels on a metal microchannel substrate, producing a rough textured structure on the microchannel walls. This enhances disturbance and disrupts the boundary layer, thereby improving the heat transfer performance of the heat exchanger. However, on the one hand, the rough texture formed by this processing method is mainly along the fluid flow direction, with limited effect on lateral fluid disturbance and boundary layer disruption; on the other hand, this patent uses traditional processing methods and completes the heat exchanger structure fabrication through cover plate welding, making it difficult to apply to additive manufacturing active cooling components with complex inner flow channels. Chinese invention patent CN111707116B discloses a "microchannel heat exchanger with multi-level microgrooves and its manufacturing method." This technology obtains metal microchannels with multi-level microgrooves by changing the axial translation and pressing depth of the working roller, thereby increasing the heat exchange area and enhancing fluid turbulence to achieve enhanced heat transfer. However, this method is mainly applicable to microchannel heat exchangers with relatively simple structures. The microgroove structure formed is limited by the processing method, and its ability to control the surface morphology of complex internal flow channels is limited.

[0005] In summary, existing technologies primarily enhance heat transfer by constructing specific microstructures on the surface of the internal flow channel using traditional processing methods, followed by welding to manufacture the heat exchanger. However, they lack a manufacturing method for controlling the microstructure of the internal flow channel surface through integrated additive manufacturing, making it difficult to achieve synergistic optimization of surface morphology and flow heat transfer performance in complex internal flow channel structures. Therefore, it is necessary to propose a method for manufacturing microstructures on the surface of the internal flow channel to enhance overall heat transfer performance. This method involves controlling the morphological characteristics of the internal flow channel surface by adjusting process parameters during manufacturing, thereby forming surface microstructures that facilitate coolant flow and heat transfer, ultimately improving the overall heat transfer performance of the active cooling component. Summary of the Invention

[0006] To overcome the difficulties in controlling the surface morphology of complex internal flow channels and the challenges in synergistically optimizing heat transfer enhancement and flow resistance in existing additive manufacturing technologies, this invention provides a method for manufacturing microstructures on the surface of internal flow channels to enhance overall heat transfer performance. This invention regulates the microstructure of the internal flow channel wall by adjusting the parameters of the additive and subtractive manufacturing process, enabling the formation of surface microstructures that facilitate coolant flow and heat transfer. This achieves synergistic optimization of heat transfer enhancement and flow resistance, thereby improving the overall cooling performance of active cooling components.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for manufacturing microstructures on the surface of internal flow channels to enhance overall heat transfer performance includes the following steps:

[0009] Step 1: Extract the diameter R and overhang angle α of the internal flow channel of the active cooling component, determine the machining allowance p and surface microstructure characteristic parameters h, and determine the tool diameter D based on the internal flow channel diameter and machining allowance; specifically:

[0010] Step 1.1: Obtain the three-dimensional model of the active cooling component to be processed, and extract the structural parameters of the internal flow channel of the active cooling component. The structural parameters include: the internal flow channel diameter R and the overhang angle α. Wherein, the overhang angle α is the angle between the local axial direction of the internal flow channel and the horizontal reference plane, α≤90°;

[0011] Step 1.2: Determine the surface microstructure characteristic parameter h of the target internal flow channel. The surface microstructure characteristic parameter h is the residual height formed during the subtractive processing, and the target microstructure characteristic parameter h ranges from 1 to 200 μm.

[0012] Step 1.3: Based on the surface microstructure characteristic parameter h in Step 1.2, further determine the machining allowance P in the subtractive processing. The machining allowance P and the surface microstructure characteristic parameter must satisfy: h≤P≤300μm;

[0013] Step 1.4: Select the subtractive cutting tool based on the inner flow channel diameter R, overhang angle α, and machining allowance p from Step 1.1. The subtractive cutting tool includes a ball end mill and a T-slot cutter with a circular cutting edge. For the inner flow channel area with an overhang angle α of 90°, a ball end mill or a T-slot cutter with a circular cutting edge is used for machining. For the inner flow channel area with an overhang angle α less than 90°, a T-slot cutter with a circular cutting edge is used for subtractive machining. The cutting edge diameter R of the T-slot cutter needs to be determined. T , , clearance diameter D b The clearance height L and the collision gap X between the tool clearance part and the inner flow channel wall are greater than 0, where the collision gap X is a safety distance set to prevent the additive model from colliding with the tool clearance part.

[0014] Furthermore, the diameter D of the ball end mill and the tool with a circular cutting edge must satisfy D < Rp;

[0015] Step 2, based on the internal flow channel structure parameters, surface microstructure characteristic parameters h, machining allowance P, tool diameter D, and cutting edge circle diameter R from Step 1. T , , clearance diameter D b By calculating the alternating parameters of material addition and subtraction, including the clearance height L and the collision gap X, an active cooling component with a target internal flow channel surface microstructure can be obtained through composite manufacturing of material addition and subtraction.

[0016] The additive-subtractive composite manufacturing process is as follows: first, additive manufacturing is performed to reach the maximum single-stage additive height, then subtractive manufacturing is carried out. After the subtractive manufacturing is completed, the next single-stage additive manufacturing with a maximum additive height H begins. This process of additive and subtractive manufacturing is repeated until the actively cooled component is printed. Therefore, it is necessary to calculate the maximum single-stage additive height H, the number of additive layers N at the maximum single-stage additive height H, the axial feed rate ΔZ for subtractive manufacturing, and the number of axial feeds S for subtractive manufacturing; specifically:

[0017] Step 2.1, based on the internal flow channel structure parameters, tool diameter D, and cutting edge circle diameter R from Step 1. T , , clearance diameter D b The maximum single-stage additive height H is calculated based on the clearance height L and the collision gap X. For the inner flow channel with a cantilever angle α = 90°, the maximum single-stage additive height H satisfies < clearance height L; for the region with a cantilever angle α < 90°, the formula for calculating the maximum single-stage additive height H is:

[0018] (1)

[0019] Step 2.2: Determine the number of additive layers N based on the maximum single additive height. Round the result to the nearest integer, discarding any fraction less than 1. The calculation formula is as follows:

[0020] (2)

[0021] Among them, H L This refers to the powder layer thickness during additive manufacturing. The maximum single-pass additive height H is calibrated based on the calculated number of additive layers N, where H = N × H. L ;

[0022] Step 2.3, based on the surface microstructure characteristic parameters h and overhang angle α from Step 1 and the cutting edge diameter R from Step 2.1. T The formula for calculating the axial feed rate ΔZ in subtractive machining is as follows:

[0023] (3)

[0024] Step 2.4: Based on the maximum single-cycle additive height H in Step 2.2 and the subtractive machining axial feed rate ΔZ in Step 2.3, calculate the number of subtractive machining axial feeds S required to achieve the maximum single-cycle additive height H. The result is rounded to the nearest integer, with any fraction less than 1 rounded up to 1. The calculation formula is as follows:

[0025] (4)

[0026] Step 2.5: Based on the maximum single additive height H, the number of additive layers N in Step 2.2, the subtractive machining axial feed amount ΔZ in Step 2.3, and the number of subtractive machining axial feeds S in Step 2.4, set the alternating parameters and process parameters for additive-subtractive composite manufacturing, generate the additive forming path and the subtractive machining tool path, and perform interference checks on the tool path. Import the interference-checked additive forming path and subtractive machining tool path into the additive-subtractive composite manufacturing equipment to perform additive-subtractive composite manufacturing on the active cooling component, and obtain an active cooling component with the target internal flow channel surface microstructure.

[0027] Furthermore, the additive and subtractive composite manufacturing process parameters also include laser power, scanning speed, powder layer thickness, machining allowance, rotation speed, and feed speed.

[0028] Step 3: Based on the active cooling component with target internal flow channel surface microstructure obtained in Step 2, conduct heat transfer performance testing to obtain its flow resistance and heat transfer performance parameters, and evaluate the comprehensive heat transfer performance of the active cooling component with target internal flow channel surface microstructure according to the comprehensive cooling efficiency factor PEC.

[0029] A PEC value greater than 1 indicates that the overall heat transfer performance of the active cooling component with the target internal flow channel surface microstructure has been improved, and the target has been achieved; a PEC value less than 1 indicates that the overall heat transfer performance of the active cooling component with the target internal flow channel surface microstructure has decreased, and it is necessary to return to step 1 to reset the characteristic parameter h of the target internal flow channel surface microstructure, and repeat the entire process of steps 1 to 2 until the overall heat transfer performance of the active cooling component with the target internal flow channel surface microstructure is greater than 1, then the target has been achieved.

[0030] The formula for calculating PEC is:

[0031] (5)

[0032] Among them, Nu s and f s Nusel number and friction factor, respectively, represent the active cooling component with target internal flow channel surface microstructure manufactured by additive and subtractive manufacturing processes. Nu0 and f0 represent the Nusel number and friction factor, respectively, for the same active cooling component manufactured by additive manufacturing processes.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) The present invention utilizes additive and subtractive composite manufacturing technology to control the characteristic parameters of the microstructure of the inner flow channel surface by adjusting the alternating additive and subtractive manufacturing parameters, thereby obtaining an active cooling component with the target inner flow channel surface microstructure.

[0035] (2) By manufacturing an active cooling component with a target internal flow channel surface microstructure, the present invention can adjust the flow state of the coolant, enhance the fluid disturbance on the internal flow channel wall and promote heat transfer, thereby achieving synergistic optimization of heat exchange performance and flow characteristics and improving the overall heat exchange performance of the active cooling component.

[0036] (3) By adjusting the alternating manufacturing parameters of additive and subtractive materials in the subtractive composite manufacturing process, the present invention achieves control over the characteristic parameters of the microstructure on the surface of the inner flow channel, forming a microstructure on the surface of the inner flow channel that can regulate the flow state of the coolant, thereby enhancing heat exchange while controlling flow resistance and improving the overall heat exchange performance of the active cooling component.

[0037] In summary, this invention enables the integrated manufacturing of complex internal flow channel surface microstructures in additively manufactured active cooling components, and improves the overall cooling performance of active cooling components, thus possessing significant potential for widespread application. Attached Figure Description

[0038] Figure 1 This is a streamline diagram of the method for manufacturing microstructures on the surface of the internal flow channel according to the present invention.

[0039] Figure 2 Schematic diagram of the active cooling internal flow channel;

[0040] Figure 3 This is a schematic diagram of the material addition and subtraction process;

[0041] Figure 4 The measurement results of the surface morphology of the internal flow channel of the additive or subtractive material;

[0042] Figure 5 This diagram shows the overall cooling performance of active cooling components with different internal flow channel surface microstructures. Detailed Implementation

[0043] The invention will be further described below with reference to the accompanying drawings.

[0044] This embodiment proposes a method for manufacturing microstructures on the surface of internal flow channels to enhance overall cooling performance. The flowchart is as follows: Figure 1 As shown, by utilizing the surface microstructure formed during milling and subtractive machining, and employing additive and subtractive composite manufacturing technology, an internal flow channel with the target surface microstructure is fabricated through the setting of additive and subtractive process parameters. This achieves synergistic optimization of heat transfer enhancement and flow resistance, thereby improving the overall cooling performance of the active cooling component. The process includes the following steps:

[0045] Step 1, the flow channels inside the active cooling component are as follows Figure 2 As shown, the diameter R and overhang angle α of the internal flow channel of the active cooling component are extracted to determine the machining allowance p and surface microstructure characteristic parameters h. The tool diameter D is then determined based on the internal flow channel diameter and machining allowance. Specifically:

[0046] Step 1.1: Obtain the three-dimensional model of the active cooling component to be processed, and extract the structural parameters of the internal flow channel of the active cooling component. The structural parameters include: internal flow channel diameter R=2mm and overhang angle α=70°.

[0047] Step 1.2, determine the surface microstructure characteristic parameter h = 100 μm of the target internal flow channel, where h is the residual height formed during the subtractive processing;

[0048] Step 1.3: Based on the surface microstructure characteristic parameter h in Step 1.2, further determine the machining allowance P = 150 μm in the subtractive processing;

[0049] Step 1.4: Based on the inner flow channel diameter R=2mm, overhang angle α=70° from Step 1.1, and machining allowance p=150μm from Step 1.3, select the subtractive cutting tool. The subtractive cutting tool includes a ball end mill and a T-end mill with a circular cutting edge. In this embodiment, the inner flow channel region has an overhang angle α less than 90°; therefore, a T-end mill with a circular cutting edge is used for subtractive machining. The cutting edge diameter R of the T-end mill needs to be determined. T =0.6mm, clearance diameter D b =0.9mm, clearance height L=6mm, and collision gap X=0.1mm between the tool clearance part and the inner flow channel wall, where the collision gap X is a safety distance set to prevent the additive model from colliding with the tool clearance part.

[0050] In this embodiment, the diameter of the T-shaped milling cutter with a circular cutting edge is D=1.5mm, which satisfies D=1.5<Rp=2-0.15=1.85;

[0051] Step 2, based on the internal flow channel structure parameters, surface microstructure characteristic parameters h, machining allowance P, tool diameter D, and cutting edge circle diameter R from Step 1. T , , clearance diameter D b The parameters for alternating addition and subtraction of materials are calculated based on the clearance height L and collision gap X, and then an active cooling component with a target internal flow channel surface microstructure is obtained through additive-subtractive composite manufacturing. The additive-subtractive composite manufacturing process is as follows: Figure 3 The process is as follows: First, additive manufacturing is performed to reach the maximum single-stage additive height H. Then, subtractive manufacturing is carried out. After subtractive manufacturing is completed, the next maximum single-stage additive manufacturing height begins. This process of additive and subtractive manufacturing is repeated until the actively cooled component is printed. Therefore, it is necessary to calculate the maximum single-stage additive height H, the number of additive layers N at the maximum single-stage additive height H, the axial feed rate ΔZ for subtractive manufacturing, and the number of axial feeds S for subtractive manufacturing. Specifically:

[0052] Step 2.1, based on the internal flow channel structure parameters, tool diameter D, and cutting edge circle diameter R from Step 1.T , , clearance diameter D b The maximum single additive height H is calculated based on the clearance height L and the collision gap X. For a suspension angle α = 70° < 90°, the formula for calculating the maximum single additive height H is:

[0053] (1)

[0054] The calculated maximum additive height in a single operation is H = 0.3 mm;

[0055] Step 2.2: Determine the number of additive layers N based on the maximum single additive height. The calculation formula is as follows:

[0056] (2)

[0057] Among them, H L =0.04mm is the powder layer thickness during additive manufacturing. The number of additive layers is calculated and rounded to the nearest integer N=7. The maximum additive height H is then calibrated, H=N×H. L =7 × 0.04 mm = 0.28 mm;

[0058] Step 2.3, based on the surface microstructure characteristic parameters h and overhang angle α from Step 1 and the cutting edge diameter R from Step 2.1. T The calculated axial feed rate for subtractive machining is ΔZ≈0.18mm, and its calculation formula is as follows:

[0059] (3)

[0060] Step 2.4: Based on the maximum single-cycle additive height H in Step 2.2 and the subtractive machining axial feed rate ΔZ in Step 2.3, calculate the number of subtractive machining axial feeds to achieve the maximum single-cycle additive height H: S≈1.56. Round the result to the nearest integer, rounding any fraction less than 1 to 1, resulting in S=2. The calculation formula is as follows:

[0061] (4)

[0062] Step 2.5: Based on the maximum single additive height H, the number of additive layers N, the subtractive machining axial feed ΔZ, and the number of subtractive machining axial feeds S in Step 2.2, the alternating parameters and process parameters for additive-subtractive composite manufacturing are set. This generates the additive forming path and the subtractive machining tool path, and interference checks are performed on the tool path. The interference-checked additive forming path and subtractive machining tool path are then imported into the additive-subtractive composite manufacturing equipment to perform additive-subtractive composite manufacturing on the active cooling component, obtaining an active cooling component with the target internal flow channel surface microstructure. The surface morphology of the machined internal flow channel is tested, and the results are as follows: Figure 4As shown, the residual height after processing is consistent with the expected result.

[0063] In this embodiment, the additive and subtractive composite manufacturing process parameters also include laser power, scanning speed, powder layer thickness, machining allowance, rotation speed, and feed speed, specifically: laser power 300W, scanning speed 1500mm / s, powder layer thickness 30μm, machining allowance 150μm, rotation speed 8000rpm, and feed speed 900mm / min.

[0064] Step 3: Based on the active cooling component with target internal flow channel surface microstructure obtained in Step 2, conduct heat transfer performance testing to obtain its flow resistance and heat transfer performance parameters, and evaluate the comprehensive heat transfer performance of the active cooling component with target internal flow channel surface microstructure according to the comprehensive cooling efficiency factor PEC.

[0065] A PEC value greater than 1 indicates that the overall heat transfer performance of the active cooling component with the target internal flow channel surface microstructure has been improved, and the target has been achieved; a PEC value less than 1 indicates that the overall heat transfer performance of the active cooling component with the target internal flow channel surface microstructure has been reduced.

[0066] The formula for calculating PEC is:

[0067] (5)

[0068] Among them, Nu s and f s Nusel number and friction factor, respectively, represent the active cooling component with target internal flow channel surface microstructure manufactured by additive and subtractive manufacturing processes. Nu0 and f0 represent the Nusel number and friction factor, respectively, for the same active cooling component manufactured by additive manufacturing processes.

[0069] The calculation results were plotted, as shown below. Figure 5 The curves shown indicate that the overall cooling efficiency factor (PEC) of the active cooling component with surface microstructure internal flow channels is greater than 1 at different Reynolds numbers, which means that the overall heat transfer performance is improved and the expected results are achieved, demonstrating the effectiveness of the method.

[0070] The above embodiments are merely illustrative of the implementation methods of the present invention, but should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.

Claims

1. A method for manufacturing microstructures on the surface of internal flow channels to enhance overall heat transfer performance, characterized in that, The method for manufacturing microstructures on the surface of internal flow channels includes the following steps: Step 1: Extract the diameter R and overhang angle α of the internal flow channel of the active cooling component, determine the machining allowance p and surface microstructure characteristic parameters h, and determine the tool diameter D based on the internal flow channel diameter and machining allowance; Step 2, based on the internal flow channel structure parameters, surface microstructure characteristic parameters h, machining allowance P, tool diameter D, and cutting edge circle diameter R from Step 1. T , clearance diameter D b The parameters of alternating addition and subtraction of materials are calculated to achieve composite manufacturing of materials to obtain an active cooling component with a target internal flow channel surface microstructure. The additive-subtractive composite manufacturing process is as follows: first, additive manufacturing is performed to reach the maximum single additive height, then subtractive manufacturing is performed. After the subtractive manufacturing is completed, the next single maximum additive height H is started. This process of additive and subtractive manufacturing is repeated until the actively cooled component is printed. Therefore, it is necessary to calculate the single maximum additive height H, the number of additive layers N at the single maximum additive height H, the axial feed amount ΔZ of subtractive manufacturing, and the number of axial feeds S of subtractive manufacturing. Step 3: Based on the active cooling component with target internal flow channel surface microstructure obtained in Step 2, conduct heat transfer performance tests to obtain its flow resistance and heat transfer performance parameters, and evaluate the comprehensive heat transfer performance of the active cooling component with target internal flow channel surface microstructure according to the comprehensive cooling efficiency factor PEC.

2. The method for manufacturing microstructures on the surface of internal flow channels to enhance overall heat transfer performance according to claim 1, characterized in that, Specifically, step 1 is as follows: Step 1.1: Obtain the three-dimensional model of the active cooling component to be processed, and extract the structural parameters of the internal flow channel of the active cooling component. The structural parameters include the internal flow channel diameter R and the overhang angle α; wherein, the overhang angle α is the angle between the local axis direction of the internal flow channel and the horizontal reference plane, and α≤90°. Step 1.2: Determine the surface microstructure characteristic parameter h of the target internal flow channel. The surface microstructure characteristic parameter h is the residual height formed during the subtractive processing, and the target microstructure characteristic parameter h ranges from 1 to 200 μm. Step 1.3: Based on the surface microstructure characteristic parameter h in Step 1.2, determine the machining allowance P in the subtractive processing. The machining allowance P and the surface microstructure characteristic parameter must satisfy: h≤P≤300μm; Step 1.4: Select the subtractive cutting tool based on the inner flow channel diameter R, overhang angle α, and machining allowance p from Step 1.

1. The subtractive cutting tool includes a ball end mill and a T-shaped end mill with a circular cutting edge. For the inner flow channel area with an overhang angle α of 90°, a ball end mill or a T-shaped end mill with a circular cutting edge is used for machining. For the inner flow channel area with an overhang angle α less than 90°, a T-shaped end mill with a circular cutting edge is used for subtractive machining. The cutting edge diameter R of the T-shaped end mill is then determined. T , clearance diameter D b The clearance height L and the collision gap X between the tool clearance part and the inner flow channel wall are greater than 0. The collision gap X is a safety distance set to prevent the additive model from colliding with the tool clearance part.

3. A method for manufacturing microstructures on the surface of internal flow channels to enhance overall heat transfer performance according to claim 2, characterized in that, In step 1.4, the diameter D of the ball end mill and the tool with a circular cutting edge must satisfy D < Rp.

4. A method for manufacturing microstructures on the surface of internal flow channels to enhance overall heat transfer performance according to claim 3, characterized in that, Step 2 specifically involves: Step 2.1, based on the internal flow channel structure parameters, tool diameter D, and cutting edge circle diameter R from Step 1. T , clearance diameter D b The maximum single-stage additive height H is calculated based on the clearance height L and the collision gap X. For the inner flow channel with an overhang angle α = 90°, the maximum single-stage additive height H satisfies < clearance height L. For the region with an overhang angle α < 90°, the formula for calculating the maximum single-stage additive height H is: (1) Step 2.2: Determine the number of additive layers N based on the maximum single additive height. Round the result to the nearest integer, discarding any fraction less than 1. The calculation formula is as follows: (2) Among them, H L The powder layer thickness during additive manufacturing; the maximum single additive height H is calibrated based on the calculated number of additive layers N, where H = N × H. L ; Step 2.3, based on the surface microstructure characteristic parameters h and overhang angle α from Step 1 and the cutting edge diameter R from Step 2.

1. T The formula for calculating the axial feed rate ΔZ in subtractive machining is as follows: (3) Step 2.4: Based on the maximum additive height H in Step 2.2 and the subtractive machining axial feed rate ΔZ in Step 2.3, calculate the number of subtractive machining axial feeds S required to achieve the maximum additive height H in a single operation. The result is rounded to the nearest integer, with any fraction less than 1 rounded up to 1. The calculation formula is as follows: (4) Step 2.5: Based on the maximum single additive height H, the number of additive layers N in Step 2.2, the subtractive machining axial feed amount ΔZ in Step 2.3, and the number of subtractive machining axial feeds S in Step 2.4, set the alternating parameters and process parameters for additive-subtractive composite manufacturing, generate the additive forming path and the subtractive machining tool path, and perform interference checks on the tool path. Import the interference-checked additive forming path and subtractive machining tool path into the additive-subtractive composite manufacturing equipment to perform additive-subtractive composite manufacturing on the active cooling component, and obtain an active cooling component with the target internal flow channel surface microstructure.

5. A method for manufacturing microstructures on the surface of internal flow channels to enhance overall heat transfer performance according to claim 4, characterized in that, In step 2, the process parameters for additive and subtractive composite manufacturing also include laser power, scanning speed, powder layer thickness, machining allowance, rotation speed, and feed speed.

6. A method for manufacturing microstructures on the surface of internal flow channels to enhance overall heat transfer performance according to claim 5, characterized in that, Step 3 specifically involves: A PEC value greater than 1 indicates that the overall heat transfer performance of the active cooling component with the target internal flow channel surface microstructure has been improved, and the target has been achieved; a PEC value less than 1 indicates that the overall heat transfer performance of the active cooling component with the target internal flow channel surface microstructure has decreased, and it is necessary to return to step 1 to reset the characteristic parameter h of the target internal flow channel surface microstructure, and repeat the entire process of steps 1 to 2 until the overall heat transfer performance of the active cooling component with the target internal flow channel surface microstructure is greater than 1, then the target has been achieved.

7. A method for manufacturing microstructures on the surface of internal flow channels to enhance overall heat transfer performance according to claim 6, characterized in that, The formula for calculating PEC is: (5) Among them, Nu s and f s Nusel number and friction factor, respectively, represent the active cooling component with target internal flow channel surface microstructure manufactured by additive and subtractive manufacturing processes. Nu0 and f0 represent the Nusel number and friction factor, respectively, for the same active cooling component manufactured by additive manufacturing.

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