Fractal tree structure micro-channel heat exchanger with rectangular grooves

Abstract

The invention discloses a fractal tree structure microchannel heat exchanger with rectangular grooves, which is characterized in that the fractal tree structure microchannel heat exchanger with rectangular grooves comprises a top cover and a bottom plate, and the top cover is fixedly connected to the top of the bottom plate; the bottom plate comprises a water inlet groove and a multi-stage flow channel which is distributed along the circumference of the water inlet groove and is of a fractal two-branch tree structure, a water outlet is formed in the side face of the bottom plate, and the water inlet groove is communicated with the water outlet through the multi-stage flow channel; a plurality of grooves are formed in the side wall of the flow channel; heat exchange in the heat exchanger is achieved; a plurality of grooves are distributed in the side wall face of each level of flat straight flow channel of the two-branch tree structure at equal intervals, continuous regrowth of a thermal boundary layer in the flow channel is promoted, heat transfer in the heat exchanger is enhanced, and meanwhile the effect of reducing the overall pressure drop of the micro-channel is achieved.

Description

Technical Field

[0001] The present invention relates to the field of heat exchange, and in particular to a fractal tree-structured microchannel heat exchanger with rectangular grooves. Background Art

[0002] With the rapid development of the microelectronics industry, the integration of electronic chips and microelectronic devices continues to improve. The increase in integration and the reduction in device size have led to a sharp increase in the heat flux density per unit area. The continuous rise in surface temperature will seriously affect the stability and reliability of the chip's operation and shorten the chip's service life. Therefore, the heat dissipation problem of electronic chips and microelectronic devices has attracted more and more attention.

[0003] Microchannel heat exchangers, with their small size, compact structure, large specific surface area, and high heat transfer efficiency, can meet higher energy efficiency standards and demonstrate superior performance in small areas with high heat flux densities. They are considered an effective solution to the heat dissipation problems of electronic chips and microelectronic devices and are widely used in new energy vehicles, petrochemicals, aerospace, biomedicine, and other fields. As heat transfer requirements continue to increase, research on microchannel heat exchangers is also expanding and deepening. The development of microchannel heat exchangers with smaller size and higher heat transfer capacity is currently a hot topic.

[0004] With the continuous development of micromachining technology, various surface-enhanced heat transfer structures have begun to appear in microchannel heat exchangers. Surface-enhanced heat transfer structures such as curved channels, fins, ribs, and grooves have been widely used in microchannel heat exchangers and have achieved many important advances. However, the application of surface-enhanced heat transfer structures in microchannel heat exchangers also faces many key technical challenges, such as excessive pressure drop and power consumption of surface structures such as curved channels, fins, and ribs, and relatively weak heat transfer enhancement effects of structures such as recesses and grooves. At the same time, fractal structures widely found in nature, such as tree-shaped, honeycomb-shaped, and blood vessel-shaped, are being utilized to arrange the flow channel network in microchannel heat exchangers, fully utilizing their excellent properties in heat and mass transfer. However, the impact of different surface-enhanced heat transfer structures on the flow and heat transfer characteristics of fractal microchannel heat exchangers is still relatively limited, and no unified conclusion has been reached. Not all surface structures added to fractal microchannels can enhance heat transfer, and some structures can even cause pressure increase within the microchannel, resulting in a decrease in the overall performance of the heat exchanger and adverse consequences. Summary of the Invention

[0005] The purpose of the present invention is to provide a fractal tree-structured microchannel heat exchanger with rectangular grooves in order to solve the above problems.

[0006] To achieve the above objectives, the present invention provides the following technical solutions: A fractal tree-like microchannel heat exchanger with rectangular grooves comprises a top cover and a bottom plate, wherein the top cover is fixedly connected to the top of the bottom plate; the bottom plate comprises a water inlet groove and a multi-stage flow channel with a fractal two-branch tree structure distributed along the circumference of the water inlet groove; a water outlet is provided on the side of the bottom plate, and the water inlet groove is connected to the water outlet through the multi-stage flow channel; a plurality of grooves are provided on the side wall of the flow channel; the height of each stage of the flow channel is equal, and the height of the flow channel is H; the relationship between the lengths of adjacent flow channels is: L i+1 / L i =2 -1 / 2 ; The relationship between the widths of adjacent flow channels is W i+1 / W i =2 -1 / 2 ; Wherein, the length is L and the width is W.

[0007] Furthermore, the cross section of the groove is one or more of an arc shape and a polygon shape.

[0008] Furthermore, the bottom plate is a hollow structure with an open top surface, the water inlet trough is opened at the center of the bottom plate, and the flow channel is opened on the bottom surface of the bottom plate.

[0009] Furthermore, the flow channel is one or more of a linear type and a curved type.

[0010] Furthermore, the cover plate and the bottom plate are both circular, and a water inlet hole is provided on the cover plate, and the water inlet hole is directly opposite to the water inlet trough, Furthermore, the diameter of the water inlet hole is 7%-10% of the diameter of the cover plate, the diameter of the water inlet groove is equal to the diameter of the water inlet hole, the length of the first-level flow channel in the flow channel is 15%-20% of the diameter of the bottom plate, and the width of the first-level flow channel is 6%-10% of the length of the first-level flow channel.

[0011] Furthermore, the groove is a rectangular groove, the length of the groove is 1%-3% of the primary flow channel, and the depth of the groove is 0.5%-2% of the primary flow channel.

[0012] Furthermore, the grooves on each stage of the flow channel are distributed at equal intervals on the inner side wall of the flow channel.

[0013] The beneficial effects are: The cooling fluid of the present invention flows in from the central water inlet of the top cover, flows through the inlet flow channel of the bottom plate, and then flows from the center of the disk to the outside step by step through the fractal two-branch tree-shaped flow channels evenly arranged along the circumference of the disk, and finally flows out from the water outlet on the side wall of the bottom plate; after a complete flow process from the inlet to the outlet, heat exchange is achieved inside the heat exchanger, and the heat exchange efficiency is improved; and a number of grooves are evenly distributed on the side wall surfaces of the straight flow channels at each level of the two-branch tree structure, which promotes the continuous re-growth of the thermal boundary layer in the flow channel, strengthens the heat transfer inside the heat exchanger, and at the same time achieves the effect of reducing the overall pressure drop of the microchannel. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0015] Figure 1 It is a schematic diagram of the overall assembly of the present invention.

[0016] Figure 2 It is an overall exploded view of the present invention.

[0017] Figure 3 It is a structural schematic diagram of the top cover in the present invention.

[0018] Figure 4 It is a structural schematic diagram of the bottom plate flow channel of the present invention.

[0019] Figure 5 It is a top view of the bottom plate flow channel of the present invention.

[0020] Figure 6 is the average value of the present invention (TMHS-R) and the traditional fractal tree structure microchannel (TMHS) under different Reynolds number conditions. Nu Number data graph.

[0021] Figure 7 Graph showing pressure drop data of the present invention (TMHS-R) and the fractal tree-structured microchannel (TMHS) under different Reynolds number conditions.

[0022] The description of the accompanying drawings is as follows: 1. Top cover; 11. Water inlet hole; 2. Bottom plate; 21. Flow channel area; 211. Flow channel; 2111. Groove; 22. Water inlet trough; 23. Water outlet. DETAILED DESCRIPTION

[0023] To make the objectives, technical solutions, and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other implementations obtained by those of ordinary skill in the art without inventive effort are within the scope of protection of the present invention.

[0024] Figure 1 and Figure 2 This is a schematic diagram of the overall structure of the present invention. The present invention provides a fractal tree-like structure microchannel heat exchanger with rectangular grooves, which is mainly composed of a top cover 1 and a bottom plate 2. In terms of material, the top cover 1 and the bottom plate 2 are made of copper. In some other embodiments, aluminum alloy or other metals can also be selected to improve the thermal conductivity of the material itself by utilizing its high thermal conductivity. In addition, the surface is highly plastic and easy to process and manufacture, making it suitable for adding surface-enhanced heat transfer structures. In terms of processing methods, the top cover 1, the bottom plate 2 and the various levels of flow channels 211 inside the bottom plate 2 are all processed and manufactured using a milling machine.

[0025] like Figure 3 As shown, in this example, the overall size of the top cover 1 is Φ23×0.25mm. The processing method is to use a milling machine to mill out the overall outline, and then mill a circular hole with a diameter of 2mm in the center of the top cover 1 as the water inlet 11 on the top cover of the heat exchanger.

[0026] like Figure 4 、 Figure 5 As shown, in this example, the overall size of the base plate 2 is Φ 24×0.75mm, the processing method is to first use a milling machine to mill out the overall outline of the bottom plate, and then mill out the water inlet groove 22 and the various levels of flow channels 211 with a fractal two-branch tree structure on the bottom plate 2. The 15 two-branch tree flow channels 211 are evenly distributed along the circumference of the disc to form a branch flow channel area 21. The flow channels 211 in this embodiment are all straight flow channels 211. In some other embodiments, the flow channels 211 can be arc-shaped. The size of the water inlet groove 22 on the bottom plate 2 is Φ 2×0.5mm, height of each level of flow channel 211 H Both are 0.5mm.

[0027] In this embodiment, each single two-branch tree flow channel 211 has four levels and three bifurcation points; the length of the first level flow channel is 211 degrees. L 1=4.4mm, width W 1=0.35mm; the relationship between the length and width of the two adjacent flow channels 211 is L i+1 / L i =2 -1 / 2 、 Wi+1 / W i =2 -1 / 2 .

[0028] like Figure 4 、 Figure 5 As shown, in this example, four rectangular grooves 2111 are evenly spaced on the sidewalls of the flow channels 211 at each level of the single fractal binary tree. In some other embodiments, the grooves 2111 may be arc-shaped, and the height of the grooves 2111 is the same as the height of the flow channels 211. The length of the grooves 2111 is L R =0.1mm, groove depth W R =0.05mm.

[0029] During use, a cooling medium is introduced into the water inlet 11 at the center of the top cover 1. Deionized water is selected as the cooling medium. In some other embodiments, air or other media can be used as the cooling medium, flowing through the water inlet groove 22 of the bottom plate 2, and then entering the flow channels 211 of the fractal two-branch tree structure and the rectangular grooves 2111 distributed along the circumference of the disk. After passing through the flow channels 211 at each level, the cooling medium finally flows out of the heat exchanger from the water outlet 23 located on the side wall of the bottom plate 2, completing the entire cooling path.

[0030] According to the above heat exchange method, Figure 6-Figure 7 As shown, a 5×10 5 w / m 2 The heat flux density is used to simulate the heat dissipation process of electronic chips and microelectronic devices. When deionized water is used as the cooling medium, the simulation results of the simulation software show that with the increase of Reynolds number, the average Nusselt value of the fractal two-branch tree structure microchannel continues to rise; and under the same Reynolds number condition, the average Nusselt number of the microchannel heat exchanger of the present invention is greater than that of the traditional fractal two-branch tree structure microchannel, and the average Nusselt number is greater than that of the traditional fractal two-branch tree structure microchannel. Nu ave = h ave D ave / λ f ,in: h ave is the average convective heat transfer coefficient, D ave is the average hydraulic diameter, λ fis the thermal conductivity of the fluid. It can be seen that the larger the average Nusselt number, the stronger the heat exchange capacity of the heat exchanger. Compared with the traditional fractal tree-shaped microchannel, the average Nusselt number of the present invention is increased by 8.5% at the maximum and 6.2% at the minimum. At the same time, the increase of the rectangular grooves 2111 also reduces the pressure drop of the present invention to a certain extent. The maximum pressure drop reduction is 1.7%, which improves the comprehensive performance of the heat exchanger.

[0031] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A fractal tree-like microchannel heat exchanger with rectangular grooves, characterized by: The device comprises a top cover and a bottom plate, wherein the top cover is fixedly connected to the top of the bottom plate; the bottom plate comprises a water inlet trough and a multi-stage flow channel with a fractal two-branch tree structure distributed along the circumference of the water inlet trough; a water outlet is opened on the side of the bottom plate, and the water inlet trough is connected to the water outlet through the multi-stage flow channel; A plurality of grooves are provided on the side wall of the flow channel; The heights of the flow channels at all levels are equal, and the height of the flow channel is H; The relationship between the lengths of adjacent flow channels is L i+1 / L i =2 -1 / 2 ; The relationship between the widths of adjacent flow channels is W i+1 / W i =2 -1 / 2 ; Among them, the length is L and the width is W.

2. The fractal tree-structured microchannel heat exchanger with rectangular grooves according to claim 1, characterized in that: The cross section of the groove is rectangular.

3. The fractal tree-structured microchannel heat exchanger with rectangular grooves according to claim 1, characterized in that: The bottom plate is a hollow structure with an open top surface. The water inlet trough is arranged at the center of the bottom plate, and the flow channel is arranged on the bottom surface of the bottom plate.

4. The fractal tree-structured microchannel heat exchanger with rectangular grooves according to claim 3, characterized in that: The flow channel is linear, curved, or one or more types.

5. The fractal tree-structured microchannel heat exchanger with rectangular grooves according to claim 4, characterized in that: The cover plate and the bottom plate are both circular, and a water inlet hole is provided on the cover plate, and the water inlet hole is directly opposite to the water inlet trough.

6. The fractal tree-structured microchannel heat exchanger with rectangular grooves according to claim 5, characterized in that: The diameter of the water inlet hole is 7%-10% of the diameter of the cover plate, the diameter of the water inlet groove is equal to the diameter of the water inlet hole, the length of the first-level flow channel in the flow channel is 15%-20% of the diameter of the bottom plate, and the width of the first-level flow channel is 6%-10% of the length of the first-level flow channel.

7. The fractal tree-structured microchannel heat exchanger with rectangular grooves according to claim 6, characterized in that: The groove is a rectangular groove, the length of the groove is 1%-3% of the primary flow channel, and the depth of the groove is 0.5%-2% of the primary flow channel.

8. The fractal tree-structured microchannel heat exchanger with rectangular grooves according to claim 7, characterized in that: The grooves on each stage of the flow channel are evenly spaced on the inner wall of the flow channel.

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