A curved surface topological microstructure surface microchannel heat exchanger and a laser processing method thereof

Abstract

The application discloses a curved surface topological microstructure surface micro-channel heat exchanger and a laser processing method thereof, and relates to the field of laser processing.The application provides a bottom plate and a cover plate;designs a micro-channel laser processing path, a curved surface topological microstructure laser processing path and laser processing parameters;utilizes a nanosecond pulse laser to perform laser etching on the bottom plate according to the micro-channel laser processing path and the laser processing parameters, and etches a plurality of microgrooves which are uniformly arranged along the length direction of the bottom plate on the surface of the bottom plate;utilizes a fiber laser to process curved surface topological microstructures on the bottom wall of each microgroove according to the curved surface topological microstructure laser processing path and the laser processing parameters;and the bottom plate and the cover plate are fixed to obtain the curved surface topological microstructure surface micro-channel heat exchanger.The curved surface topological microstructure surface micro-channel heat exchanger processed by the application has good heat exchange effect and low flow resistance, and has high comprehensive heat exchange performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of laser processing technology, in particular to a surface micro-channel heat exchanger with curved topological micro-structure and a laser processing method thereof. BACKGROUND

[0002] With the increasing integration of electronic chips, the heat dissipation problem of electronic equipment is becoming increasingly serious. Micro-channel heat exchanger has become a key technology to solve the heat dissipation problem of high-power density equipment due to its small size and high heat dissipation efficiency. In order to further improve the heat exchange performance, current research mainly adds conventional micro-structures such as rectangles and cylinders to the surface of micro-channels. Such micro-structures increase the heat exchange effect of micro-channels while also produce high flow resistance, resulting in a corresponding increase in the required pump power of micro-channels. SUMMARY

[0003] To solve the technical problems in the background art, the present application provides a surface micro-channel heat exchanger with curved topological micro-structure and a laser processing method thereof.

[0004] In a first aspect, the present application provides a processing method of a surface micro-channel heat exchanger with curved topological micro-structure, comprising:

[0005] providing a bottom plate and a cover plate;

[0006] designing a micro-channel laser processing path, a curved topological micro-structure laser processing path and laser processing parameters;

[0007] using a nanosecond pulse laser to perform laser etching on the bottom plate according to the micro-channel laser processing path and the laser processing parameters, etching a plurality of micro-slots on the surface of the bottom plate, the micro-slots being uniformly arranged along the length direction of the bottom plate, each micro-slot extending along the width direction of the bottom plate and having its two ends extending to the surface of the bottom plate to form an inlet and an outlet;

[0008] using a fiber laser to process curved topological micro-structures on the bottom wall of each micro-slot according to the curved topological micro-structure laser processing path and the laser parameters; wherein the curved topological micro-structures include a plurality of curved micro-structures arranged at equal intervals along the length direction of the micro-channel;

[0009] covering and fixing the processed bottom plate and the cover plate to obtain the surface micro-channel heat exchanger with curved topological micro-structure.

[0010] Preferably, the curved micro-structure is a cylinder or a groove, and the curved micro-structure includes an incident flow surface and a backflow surface, the incident flow surface faces the inlet of the micro-channel, the backflow surface faces the outlet of the micro-channel, and the projection of the incident flow surface at the bottom of the micro-slot is an arc protruding towards the inlet of the micro-channel.

[0011] Preferably, the cross section of the curved micro-structure is crescent-shaped.

[0012] Preferably, the total length of the bottom plate is 10 mm, the total height is 1 mm; the length of the single micro groove is 10 mm, the width is 0.5 mm, the height is 0.7 mm, the spacing between the micro grooves is 0.4 mm; the transverse length of the curved micro structure is 0.1 mm-0.3 mm, the longitudinal length of the curved micro structure is 0.1 mm-0.3 mm, and the height of the curved micro structure is-0.25 mm-0.3 mm.

[0013] Preferably, the longitudinal length of the curved micro structure is 0.25 mm, the transverse length is 0.2 mm, and the height is 0.15 mm.

[0014] Preferably, the bottom plate is made of aluminum alloy, and the cover plate is made of acrylic.

[0015] Preferably, the laser processing parameters include: the laser spot diameter is 50 μm, the pulse frequency parameter is 20 kHz, the scanning speed is 200 mm / s, the power is 20 W, the scanning interval is 5 μm, the scanning number of the micro channel laser processing path is 17 times, and the scanning number of the curved topological micro structure laser processing path is 7 times.

[0016] Preferably, in the micro channel laser processing path, the laser first performs multiple first longitudinal scans in the width direction of the micro groove, then performs multiple transverse scans in the length direction of the micro groove, and then performs multiple second longitudinal scans in the width direction of the micro groove on the preset regions at both ends of the micro groove in the width direction of the micro groove.

[0017] Preferably, the first longitudinal scan is drawn 1 time, the transverse scan is drawn 3 times, and the second longitudinal scan is drawn 3 times.

[0018] Preferably, the curved topological micro structure laser processing path includes a plurality of scanning path diagrams of the curved micro structure arranged in the length direction of the micro groove on the bottom wall of the micro groove.

[0019] In a second aspect, the present application further provides a curved topological micro structure surface micro channel heat exchanger prepared by the laser processing method of any one of the first aspect.

[0020] In the present application, the curved surface topological microstructure surface microchannel heat exchanger and the laser processing method thereof are proposed, the microgrooves and the curved surface topological microstructure on the surface of the microgrooves are precisely processed on the bottom plate through laser technology, and the microchannels in the prepared curved surface topological microstructure surface microchannel heat exchanger have good surface morphology; moreover, the introduction of the curved surface topological microstructure can generate larger vortex flow in the microchannels, and the vortex flow is periodically distributed left and right; the distributed vortex flow can enhance the mixing of the liquid in the microchannels and enhance the heat exchange, so that the heat dissipation efficiency of the rectangular microchannel heat spreader can be greatly improved, and the flow resistance is lower and the comprehensive heat exchange performance is higher. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The flowchart of the laser processing method of the curved surface topological microstructure surface microchannel heat exchanger in an embodiment of the present application is shown.

[0022] Figure 2 The structure diagram of the curved surface topological microstructure surface microchannel in an embodiment of the present application is shown.

[0023] Figure 3 The structure diagrams of MC-NW and MC-CW, MC-RW and MC-TW are shown; wherein (a) is MC-NW, (b) is MC-CW, (c) is MC-RW, and (d) is MC-TW.

[0024] Figure 4 The bottom surface temperature cloud diagram and the Nusselt number diagram of MC-NW and MC-CW, MC-RW and MC-TW are shown; wherein (a) is the bottom surface temperature cloud diagram, and (b) is the Nusselt number diagram.

[0025] Figure 5 The cross-sectional pressure cloud diagram and the friction factor diagram of MC-NW and MC-CW, MC-RW and MC-TW are shown; wherein (a) is the cross-sectional pressure cloud diagram, and (b) is the friction factor diagram.

[0026] Figure 6 The comprehensive heat exchange performance diagram of MC-NW and MC-CW, MC-RW and MC-TW is shown.

[0027] Figure 7 The streamline diagram and the velocity cloud diagram of MC-NW and MC-CW, MC-RW and MC-TW are shown; wherein (a) is the streamline diagram, and (b) is the velocity cloud diagram.

[0028] Figure 8 The laser processing path in an embodiment of the present application is shown; wherein (a) is the microchannel laser processing path, and (b) is the curved surface topological microstructure laser processing path.

[0029] Figure 9 The three-dimensional topography of the microchannels under different laser processing paths; wherein (a) is a laser longitudinal scanning, (b) is under laser transverse scanning, (c) is laser transverse scanning combined with longitudinal scanning, and (d) is the microchannel laser processing path in the embodiment.

[0030] Figure 10 The three-dimensional topography of the rectangular microchannels after laser processing in an embodiment of the present application. DETAILED DESCRIPTION

[0031] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0032] In a first aspect, with reference to Figure 1 and Figure 2 The present application provides a curved surface topological microstructure surface microchannel heat exchanger (MC-NW), comprising: a heat exchange substrate, a plurality of rectangular microchannels are uniformly arranged in the heat exchange substrate along the length direction of the heat exchange substrate, each microchannel extends along the width direction of the heat exchange substrate, and both ends of each microchannel extend to the outer surface of the heat exchange substrate to form an inlet and an outlet; a curved surface topological microstructure is arranged on the bottom wall of each microchannel; wherein the curved surface topological microstructure comprises a plurality of curved surface microstructures arranged at equal intervals along the length direction of the microchannel.

[0033] In the present application, the curved surface topological microstructure exists in the microchannel. According to Bernoulli's principle, the flow rate is accelerated in the area with smaller curvature radius, resulting in a local pressure drop and forming a transverse pressure gradient. This gradient forces the fluid to produce a secondary flow perpendicular to the main flow direction, thereby increasing the heat exchange efficiency of the rectangular microchannel. Moreover, the fluid will generate a large vortex between the two curved surface microstructures in the channel, and the vortex is periodically distributed left and right. This distributed vortex can enhance the mixing of the liquid in the microchannel and enhance the heat exchange, which can greatly improve the heat dissipation efficiency of the rectangular microchannel heat sink. The heat exchanger in the embodiment has good heat exchange effect and low flow resistance, and the comprehensive heat exchange performance is the highest.

[0034] In a further embodiment, the curved surface microstructure is a cylinder or a groove, and the cross section of the curved surface microstructure is a crescent shape, the convex surface of the crescent shape faces the inlet of the microchannel, and the concave surface of the crescent shape faces the outlet of the microchannel, so as to form a transverse pressure gradient, thereby forcing the fluid to produce a secondary flow perpendicular to the main flow direction, thereby increasing the heat exchange efficiency of the rectangular microchannel.

[0035] In order to facilitate processing, in one specific embodiment, the heat exchange substrate includes a bottom plate and a cover plate, the top surface of the bottom plate is provided with a plurality of top-surface-open microgrooves along the length direction, each microgroove extends along the width direction of the heat exchange substrate, and both ends of each microchannel extend to the outer surface of the heat exchange substrate to form an inlet and an outlet; the cover plate covers the substrate so that the microgrooves between the cover plate and the substrate form microchannels; the curved-topology microstructure is arranged on the bottom wall of the microgroove.

[0036] In a further specific embodiment, the bottom plate is made of aluminum alloy, and the cover plate is made of acrylic.

[0037] In one specific embodiment, the total length of the bottom plate is 10 mm, the total height is 1 mm, the length of a single microgroove is 10 mm, the width is 0.4 mm, the height is 0.15 mm, and the spacing between the microgrooves is 0.4 mm. In one specific embodiment, the total length of the bottom plate is 10 mm, the total height is 1 mm, the length of a single microgroove is 10 mm, the width is 0.4 mm, the height is 0.15 mm, and the spacing between the microgrooves is 0.4 mm. In one specific embodiment, the total length of the bottom plate is 10 mm, the total height is 1 mm, the length of a single microgroove is 10 mm, the width is 0.4 mm, the height is 0.15 mm, and the spacing between the microgrooves is 0.4 mm. In one specific embodiment, the total length of the bottom plate is 10 mm, the total height is 1 mm, the length of a single microgroove is 10 mm, the width is 0.4 mm, the height is 0.15 mm, and the spacing between the microgrooves is 0.4 mm. In one specific embodiment, the total length of the bottom plate is 10 mm, the total height is 1 mm, the length of a single microgroove is 10 mm, the width is 0.4 mm, the height is 0.15 mm, and the spacing between the microgrooves is 0.4 mm.

[0038] It is found through experiments that, for the best overall heat exchange performance, the microstructure longitudinal length decreases first and then increases, the best overall heat exchange performance is at a longitudinal length of 0.2 mm; the microstructure transverse length continuously increases, the best overall heat exchange performance is at a transverse length of 0.25 mm; the greater the height of the microstructure in the microchannel, the worse the overall heat exchange performance of the microchannel, the best overall heat exchange performance is at a microstructure height of 0.15 mm.

[0039] Therefore, in this embodiment, the longitudinal length is 0.25 mm, the transverse length is 0.2 mm, and the height is 0.15 mm.

[0040] In order to verify that the curved-topology microstructure surface microchannel heat exchanger proposed in this embodiment has high overall heat exchange performance, this embodiment analyzes the temperature, pressure drop, velocity cloud map, and flow line map of surfaces with four kinds of microstructure microchannels, i.e., an elliptical microstructure microchannel (MC-CW), a rectangular microstructure microchannel (MC-RW), a triangular microstructure microchannel (MC-TW), and a curved-topology microstructure microchannel (MC-NW) designed in this embodiment, and analyzes the overall heat exchange performance. The four kinds of microstructure microchannels are shown in Figure 3 , and the analysis results are shown in Figures 4-7 .​​​​​​​

[0041] From Figures 4-7 It can be found that the curved surface topological microstructure has better heat exchange effect and lower flow resistance, and the comprehensive heat exchange performance is the highest, which is improved by 9.8%.

[0042] In a second aspect, the application further provides a processing method of the curved surface topological microstructure surface micro-channel heat exchanger, comprising:

[0043] providing a bottom plate and a cover plate;

[0044] designing a micro-channel laser processing path, a curved surface topological microstructure laser processing path and laser processing parameters;

[0045] laser etching on the bottom plate according to the micro-channel laser processing path and the laser processing parameters by using a nanosecond pulse laser, and etching a plurality of rectangular microgrooves on the surface of the bottom plate, the microgrooves are uniformly arranged along the length direction of the bottom plate, each microgroove extends along the width direction of the bottom plate, and the two ends of the microgroove extend to the surface of the bottom plate to form an inlet and an outlet;

[0046] processing a curved surface topological microstructure on the bottom wall of each microgroove according to the curved surface topological microstructure laser processing path and the laser parameters by using a fiber laser; wherein the curved surface topological microstructure comprises a plurality of curved surface microstructures arranged at equal intervals along the length direction of the micro-channel;

[0047] fixing the processed bottom and the cover plate to obtain the curved surface topological microstructure surface micro-channel heat exchanger.

[0048] The micro-channel and the surface curved surface microstructure of the micro-channel are accurately processed on the bottom plate by laser technology, and the micro-channel in the curved surface topological microstructure surface micro-channel heat exchanger prepared has a good surface morphology.

[0049] In this embodiment, after the microgroove is processed, the curved surface topological microstructure in each microgroove is processed in the original position after cooling.

[0050] The curved surface microstructure in this embodiment is a cylinder or a groove, the curved surface microstructure comprises a flow-facing surface and a back-flow surface, the flow-facing surface faces the inlet of the micro-channel, the back-flow surface faces the outlet of the micro-channel, and the projection of the flow-facing surface on the bottom of the microgroove is an arc protruding to the inlet of the micro-channel.

[0051] In one specific embodiment, the cross section of the curved surface microstructure is crescent-shaped.

[0052] In the embodiment, the total length of the bottom plate is 10 mm, and the total height is 1 mm; the length of the micro groove is 10 mm, the width of the micro groove is 0.5 mm, the height of the micro groove is 0.7 mm, and the spacing between the micro grooves is 0.4 mm; the transverse length of the curved micro structure is 0.1 mm-0.3 mm, the longitudinal length of the curved micro structure is 0.1 mm-0.3 mm, and the height of the curved micro structure is -0.25 mm-0.3 mm.

[0053] In a further embodiment, the longitudinal length of the curved micro structure is 0.25 mm, the transverse length is 0.2 mm, and the height is 0.15 mm.

[0054] The bottom plate in the embodiment is made of aluminum alloy, and the cover plate is made of acrylic.

[0055] In order to improve the quality of laser processing, in the embodiment, the laser processing parameters include: the laser spot diameter is 50 μm, the focal length is 370 mm, the pulse frequency parameter is 20 kHz, the scanning speed is 200 mm / s, the power is 20 W, the scanning interval is 5 um, the scanning number of the micro channel laser processing path is 17 times, and the scanning number of the curved topological micro structure laser processing path is 7 times.

[0056] As shown in Figure 8 In the embodiment, in the micro channel laser processing path, the laser first performs a plurality of first longitudinal scans in the width direction of the micro groove (i.e., first performs a transverse scan), then performs a plurality of transverse scans in the length direction of the micro groove (i.e., then performs a longitudinal scan), and then performs a plurality of second longitudinal scans in the width direction of the micro groove on the preset regions at both ends of the micro groove in the width direction of the micro groove.

[0057] The number of lines drawn by the first longitudinal scan is 1, the number of lines drawn by the transverse scan is 3, and the number of lines drawn by the second longitudinal scan is 3.

[0058] The embodiment adopts a combination of transverse scanning and longitudinal scanning to process a rectangular micro channel, realizes rapid and accurate processing of the micro channel, and eliminates the influence of focal length change during laser processing by performing a plurality of second longitudinal scans in the width direction of the micro groove on the preset regions at both ends of the micro groove in the width direction of the micro groove.

[0059] In order to analyze the influence of the scanning method on the micro groove processing, under the same scanning number, four bottom plates are respectively subjected to laser transverse scanning, longitudinal laser scanning, a combination of transverse scanning and longitudinal scanning, and the micro channel laser processing path in the embodiment, and the three-dimensional topography of the micro groove obtained is shown in Figure 9 .

[0060] According to Figure 9It can be found that the microchannel obtained by laser transverse scanning has a good channel morphology, but the depth is low and the time required for processing the same depth is long. The microchannel obtained by laser longitudinal scanning has a larger depth, and the time required for processing the same depth is short, but the surface morphology is poor. The combination of transverse scanning and longitudinal scanning can achieve simple and rapid processing of the microchannel. However, the microchannel morphology processed by the combination of transverse scanning and longitudinal scanning is not rectangular but trapezoidal due to the change of laser processing focal length. The microchannel laser processing path of the embodiment obtains a rectangular microchannel with a good surface morphology, and eliminates the influence of the change of laser processing focal length.

[0061] As shown in Figure 8 In the embodiment, the curved surface topological microstructure laser processing path includes a scanning path diagram of the curved surface microstructure; during the processing of the curved surface topological microstructure of each microchannel, the scanning path diagram of the curved surface microstructure is sequentially arranged on the bottom wall of the microchannel in the length direction of the microchannel, and the laser is sequentially processed according to the scanning path diagram of the curved surface microstructure.

[0062] In order to ensure accurate positioning during processing, after the rectangular microchannel is processed, the position of the bottom plate is kept unchanged, and the laser processing path is adjusted to continue processing after cooling. Figure 10 The three-dimensional morphology of the rectangular microchannel after processing is shown. As can be seen from Figure 10 , the microstructure is accurately located at the center position of the microchannel, which shows that the processing method proposed in the embodiment can realize accurate positioning, and successfully prepare a rectangular microchannel with a microstructure on the surface.

[0063] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can make equivalent replacements or changes to the technical solution and the inventive concept of the present application within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A laser processing method for a surface microchannel heat exchanger with a curved topological microstructure, characterized in that, include: Provide base plate and cover plate; Design microchannel laser processing paths, curved surface topology microstructure laser processing paths, and laser processing parameters; among which, the laser processing parameters include: laser spot diameter of 50 μm, pulse frequency of 20 kHz, scanning speed of 200 mm / s, power of 20 W, scanning spacing of 5 μm, scanning number of 17 times for the microchannel laser processing path, and scanning number of 7 times for the curved surface topology microstructure laser processing path; A nanosecond pulsed laser is used to perform laser etching on a substrate according to the microchannel laser processing path and laser processing parameters. Multiple rectangular microchannels, evenly arranged along the length of the substrate, are etched onto the substrate surface. Each microchannel extends along the width of the substrate, with its two ends extending to the substrate surface to form an inlet and an outlet. In the microchannel laser processing path, the laser first performs multiple longitudinal scans along the width of the microchannel, then multiple transverse scans along the length of the microchannel, and finally multiple second longitudinal scans along the width of the microchannel on preset areas at both ends. The first longitudinal scan has 1 scan count, the transverse scan has 3 scan counts, and the second longitudinal scan has 3 scan counts. Using a fiber laser, after processing each microchannel according to the laser processing path and laser parameters for the curved topological microstructure, the base plate position remains unchanged. After cooling, a curved topological microstructure is processed on the bottom wall of each microchannel. The laser processing path for the curved topological microstructure includes a scanning path diagram of multiple curved microstructures arranged sequentially on the bottom wall of the microchannel along its length. Each curved topological microstructure comprises multiple curved microstructures evenly spaced along the length of the microchannel. These microstructures are cylindrical and include an incoming flow surface and a outgoing flow surface. The incoming flow surface faces the inlet of the microchannel, and the outgoing flow surface faces the outlet. The projection of the incoming flow surface onto the bottom of the microchannel is an arc protruding towards the inlet. The cross-section of each curved microstructure is crescent-shaped. The total length of the base plate is 10 mm, and the total height is 1 mm. The length of the microchannel is 10 mm, the width is 0.5 mm, the height is 0.7 mm, and the spacing between microchannels is 0.4 mm. The lateral length of the curved microstructure is 0.2 mm. The longitudinal length of the curved microstructure is 0.25 mm, and the height of the curved microstructure is 0.15 mm. The processed base plate and cover plate are combined and fixed to obtain a surface microchannel heat exchanger with curved topology microstructure.

2. The laser processing method for a curved surface microchannel heat exchanger according to claim 1, characterized in that, The base plate is made of aluminum alloy, and the cover plate is made of acrylic.

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