CN111174615A

CN111174615A - Surface energy gradient bionic liquid suction core and application

Info

Publication number: CN111174615A
Application number: CN202010017558.6A
Authority: CN
Inventors: 周伟; 凌伟淞; 刘成忠; 黄家乐; 刘瑞亮
Original assignee: Xiamen University
Current assignee: Xiamen University
Priority date: 2020-01-08
Filing date: 2020-01-08
Publication date: 2020-05-19
Anticipated expiration: 2040-01-08
Also published as: CN111174615B

Abstract

The invention discloses a surface energy gradient bionic liquid suction core and application, wherein the surface energy gradient bionic liquid suction core comprises a plurality of bionic units which are arranged in a three-dimensional array, guide grooves are formed in the bionic units, the projection of each guide groove is a half ellipse and comprises an inclined surface, a curved surface and a flange, the inclined surface is provided with a structure with gradually increased groove body depth along the liquid flow direction, the tail end of the inclined surface is connected with the curved surface, the curved surface is a concave surface at one side close to the inclined surface, the upper end of the curved surface extends back to the inclined surface direction to form the flange, and the flange is smoothly connected with the inclined surface of the next bionic unit; the bionic unit simulates the microstructure characteristics of the surface of pitcher plant, and the surface energy gradient bionic wick is applied to a loop heat pipe and other phase change heat dissipation devices, so that the capillary suction force of the wick can be improved, the directional transmission of liquid can be ensured, the problems of insufficient capillary suction force and back heat conduction of the loop heat pipe are effectively solved, and the bionic unit has good engineering application significance.

Description

Surface energy gradient bionic liquid suction core and application

Technical Field

The invention relates to a surface energy gradient bionic liquid suction core and application thereof.

Background

With the development of microelectronic technology, the dominant frequency and integration of electronic chips are higher and higher, and the power consumption per unit area is increased sharply, resulting in an increase in heat flux density. For example, the heat flow density of the LED lamp bead reaches 100W/cm²(ii) a The heat flux density of the CPU is generally 60-100W/cm²Even up to 200W/cm². When the heat flux density of the electronic chip exceeds 0.08W/cm²In time, natural heat dissipation cannot meet the heat dissipation requirements; the heat flow density exceeds 0.3W/cm²At the same time, forced convection heat dissipation has reached its limit. The thermal control problem of high heat flux density chips has become a bottleneck limiting the development of microelectronic chip technology, and the improvement of the reliability of electronic components, the increase of power capacity, the improvement of integration level and the miniaturization of structures directly depend on the solution of the thermal control problem of chips.

In order to solve the heat dissipation problem of the electronic chip with high heat flux density, the phase change heat dissipation is widely applied. The loop heat pipe is a typical phase change heat dissipation device and consists of an evaporator, a condenser, a steam connecting pipe, a liquid connecting pipe and the like. The evaporator is in direct contact with the electronic chip, the liquid in the evaporator absorbs latent heat of vaporization, the steam carries heat to reach the condenser along the steam connecting pipe under the action of steam pressure, the heat is released in a liquefaction mode under the action of the reinforced condensation structure, and the liquefied working medium returns to the evaporator through the liquid connecting pipe. Because the loop heat pipe adopts a phase change heat transfer mechanism, the heat dissipation capacity of the loop heat pipe is higher than that of the current main heat dissipation mode by more than 2 orders of magnitude. The capillary force, the vapor phase change pressure and the gravity of the liquid absorption core are used for assisting in operation, external energy input is not needed, the energy-saving and emission-reducing advantages are achieved, and meanwhile vibration is small and noise is avoided during working. The vapor and the liquid are separated, and the liquid absorption core only exists in the evaporator, so that the carrying limit of the heat pipe is avoided, and the heat dissipation capacity of the loop heat pipe is further improved.

The wick is the most central component of the loop heat pipe and provides both capillary suction to drive the circulation of the liquid and liquid flow channels while preventing the vapor and heat generated from reaching the liquid compensation chamber in reverse. In order to increase the capillary suction force, the pore size of the wick needs to be reduced, but the liquid flow resistance and heat leakage to the liquid compensation chamber are increased; to reduce liquid flow resistance, the wick pore size needs to be increased, but capillary suction is reduced, increasing vapor reverse flow. Although a great deal of research is being conducted on liquid absorbent cores at present, the results are very poor, and the technical problems are difficult to effectively solve. The nepenthes surface microstructure can enable liquid to be rapidly transmitted towards a specific direction, and the special function has good application in the liquid absorption core. How to extract the surface microstructure of the pitcher plant, perform spatial transformation on the surface microstructure of the pitcher plant and integrate the liquid directional and rapid transmission function into the liquid absorption core has important significance on the efficient operation and heat transmission of the loop heat pipe.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, provides a bionic liquid suction core with surface energy gradient and application thereof, and solves the problems of insufficient capillary suction force and back heat conduction in the background technology.

The technical scheme adopted by the invention for solving the technical problems is as follows: the utility model provides a bionical imbibition core of surface energy gradient, includes a plurality of bionical units that three-dimensional array arranged, set up the guiding gutter on the bionical unit, the projection of guiding gutter is half ellipse, including inclined plane, curved surface and flange, the inclined plane just has the structure that the cell body degree of depth increases gradually along the liquid flow direction, the end-to-end connection on inclined plane has the curved surface, the curved surface is the concave surface in one side that is close to the inclined plane, and the upper end of curved surface is stretched back to the inclined plane direction and is formed the flange, the flange links up with the inclined plane level and smooth.

In a preferred embodiment of the present invention, the joint between the curved surface and the inclined surface is a fillet, and the radius of the fillet is 50 to 80 μm.

In a preferred embodiment of the present invention, an angle between the inclined plane and the horizontal plane is 5 to 15 °, and an angle between a tangent of the curved surface of the flange and the inclined plane of the next bionic unit is 30 to 45 °.

In a preferred embodiment of the present invention, the bionic unit further comprises an aperture control block, and the aperture control block is used for forming an aperture between vertically adjacent bionic units.

In a preferred embodiment of the present invention, the aperture control block includes a convex pillar disposed beside the guiding trench, and the width and height of the convex pillar are 50-100 μm.

In a preferred embodiment of the present invention, the bionic unit is mirror-symmetrical along the thickness direction.

In a preferred embodiment of the present invention, the surface of the bionic unit is recessed from both sides toward the axial direction of the guiding groove to form a certain curvature.

In a preferred embodiment of the invention, the bionic units are arranged in parallel along the direction of the flow guide grooves in the transverse direction and are aligned and stacked in the longitudinal direction through the pore control blocks.

The invention also provides application of the surface energy gradient bionic liquid suction core in a phase change heat dissipation device.

In a preferred embodiment of the present invention, the phase change heat dissipation device includes a loop heat pipe.

Compared with the background technology, the technical scheme has the following advantages:

1. the invention imitates the microstructure characteristics of the nepenthes surface to form a surface energy gradient bionic unit, so that liquid can be directionally transmitted along a specific direction, the contact angles of the liquid in the flowing direction are different, and the front end of the liquid drop forms a super-hydrophilic state with the contact angle far smaller than 90 degrees; the rear end of the liquid drop forms an included angle theta with the liquid drop₂Is tangent to form a super-hydrophobic state with a contact angle larger than 150 degrees. The difference of the hydrophilicity and the hydrophobicity of the liquid drops before and after forming the surface energy gradient difference, so that the liquid is ensured to flow along the super-hydrophilic end, and the liquid is inhibited from flowing to the super-hydrophobic end;

2. the pore control block is arranged, so that micro pores are formed among the bionic structure units, capillary suction force is provided, and meanwhile, liquid can be ensured to permeate in the width direction and the height direction, so that the liquid can uniformly fill the whole liquid suction core;

3. the invention is applied to the loop heat pipe, because the surface energy gradient from super-hydrophobic to super-hydrophilic is arranged in the liquid absorption core, the capillary suction force generated by the liquid absorption core is larger than that of the common liquid absorption core with the same aperture, the liquid can be rapidly transmitted in the specific direction in the liquid absorption core, and the generated vapor can be prevented from reversely flowing to the liquid compensation chamber; under the condition of meeting the capillary suction force, the pore diameter of the liquid absorption core can be properly improved, and the flow resistance of the liquid working medium is reduced; the problems of insufficient capillary suction force and back heat conduction of the loop heat pipe are effectively solved, and the method has good engineering application significance.

Drawings

FIG. 1 is a perspective view of a surface energy gradient biomimetic wick;

FIG. 2 is a layout diagram of a three-dimensional array of bionic cells;

FIG. 3 is a perspective view of a biomimetic unit;

3 FIG. 3 4 3 is 3 a 3 cross 3- 3 sectional 3 view 3 of 3 the 3 biomimetic 3 unit 3 of 3 FIG. 3 3 3 taken 3 along 3 line 3 A 3- 3 A 3; 3

FIG. 5 is a schematic view;

FIG. 6 is an enlarged schematic view of the front end of the droplet of FIG. 5;

FIG. 7 is a schematic diagram of a loop heat pipe evaporator configuration;

wherein, 1, absorbing the liquid core; 2. a bionic unit; 2-1. (biomimetic unit) upper part; 2-2. (biomimetic unit) lower part; 3-1. lateral (liquid flow direction); 3-2. longitudinal (thickness direction); 4. a bevel; 5. a curved surface; 6. a flange; 7. an aperture control block; 9. round corners; 11. a droplet; 12. an evaporator housing; 13. a liquid compensation chamber; 14. a liquid inlet; 15. a heating rod; 16. a steam tank; 17. and (4) a steam outlet.

Detailed Description

The content of the present invention will be specifically described below with reference to examples, and for convenience of description, the flow direction of the liquid droplet 11 on the surface of the biomimetic unit 2 is defined as the transverse direction 3-1, and the thickness direction of the biomimetic unit 2 is defined as the longitudinal direction 3-2.

Example 1

A bionic wick 1 with a surface energy gradient according to the present embodiment, as shown in fig. 1 and 2, includes a plurality of bionic units 2 arranged in a three-dimensional array.

Offer the guiding gutter on the bionical unit 2, as fig. 3, the projection of guiding gutter is half ellipse, as fig. 4, the guiding gutter includes inclined plane 4, curved surface 5 and flange 6, inclined plane 4 just has the structure that the cell body degree of depth increases gradually along liquid flow direction 3-1, the end-to-end connection on inclined plane 4 has curved surface 5, curved surface 5 is the concave surface in the one side that is close to inclined plane 4, and the upper end of curved surface 5 is stretched back to inclined plane 4 direction and is formed flange 6, flange 6 links up with the inclined plane 4 level and smooth of next bionical unit 2, forms a closed angle.

In this embodiment, the joint of the curved surface 5 and the inclined surface 4 is a fillet 9, and the radius R of the fillet 9 is 50 to 80 μm.

The included angle theta between the inclined plane 4 and the horizontal plane₁Is 5-15 degrees, and the included angle theta between the tangent of the curved surface 5 of the flange 6 and the inclined surface 4 of the next bionic unit 2₂Is 30 to 45 degrees. During transmission, the included angle theta₁A super-hydrophilic state with a contact angle far less than 90 degrees with the front end of the liquid drop 11 and an included angle theta₂And a super-hydrophobic state with a contact angle larger than 150 degrees is formed at the rear end of the liquid drop 11, and the super-hydrophilic state and the super-hydrophobic state form a bionic surface with surface energy gradient, so that the bionic liquid suction core 1 can promote the transmission of liquid along one super-hydrophilic end and inhibit the transmission of liquid along one super-hydrophobic end.

The bionic unit 2 further comprises an aperture control block 7, and the aperture control block 7 is used for forming an aperture between the vertically adjacent bionic units 2. In this embodiment, the aperture control block 7 includes four protruding columns arranged along the vertical direction, the four protruding columns are respectively arranged at four corners of the bionic unit 2 to surround the flow guide grooves therein, and the width W and the height H of the protruding columns are 50-100 μm.

3 in 3 this 3 embodiment 3, 3 the 3 bionic 3 unit 3 2 3 is 3 mirror 3- 3 symmetrical 3 along 3 the 3 thickness 3 direction 3, 3 and 3 the 3 surface 3 of 3 the 3 bionic 3 unit 3 2 3 is 3 recessed 3 from 3 both 3 sides 3 toward 3 the 3 axial 3 direction 3 of 3 the 3 flow 3 guide 3 groove 3 to 3 form 3 a 3 certain 3 curvature 3, 3 as 3 shown 3 in 3 fig. 3 3 3, 3 the 3 upper 3 surface 3 of 3 the 3 bionic 3 unit 3 2 3 is 3 the 3 lowest 3 at 3 the 3 line 3 a 3- 3 a 3. 3

The bionic units 2 are arranged in parallel along the direction of the diversion trench in the transverse direction and are mirrored into an upper part 2-1 and a lower part 2-2, so that the three-dimensional array is facilitated, and the directional transmission and capillary suction performance can be improved. The capillary wick is longitudinally arranged in an aligned and overlapped mode through the pore control blocks 7, and the porosity and the effective pore size of the wick 1 can be adjusted by controlling the sizes of the pore control blocks 7, so that capillary suction force is provided. In addition, due to the existence of the pore control block 7, the upper part, the lower part, the left part and the right part of the liquid absorbing core 1 are communicated, so that liquid can permeate along the transverse direction and the longitudinal direction and uniformly fill the whole liquid absorbing core 1.

The principle of liquid directional transmission of the surface energy gradient bionic liquid absorption core 1 is shown in figures 5 and 6, and the included angle between the front end of the liquid drop 11 and the liquid drop is theta₁Is tangent to the downward slope 4 to form a contact angle theta_1-1A superhydrophilic state substantially less than 90 °; the rear end of the droplet 11 makes an angle theta with the liquid₂Is tangent to the flange 6 (sharp angle) to form a contact angle theta_2-1A superhydrophobic state greater than 150 °. The surface energy of the liquid drop 11 at the super-hydrophilic end is larger and has an attraction effect on the liquid drop 11, and the surface energy of the liquid drop 11 at the super-hydrophobic end is smaller and has a repulsion effect on the liquid drop 11. Due to the existence of the downward inclined surface 4, the curved surface 5 and the flange 6 (sharp angle), a surface energy gradient difference is formed, the driving liquid drop 11 is rapidly transmitted along the liquid flowing direction and cannot be transmitted in the opposite direction, and the function of a liquid diode is realized.

Example 2

This example applies the surface energy gradient biomimetic wick 1 of example 1 to a loop heat pipe evaporator comprising an evaporator housing 12, a liquid compensation chamber 13, a liquid inlet 14, a heating rod 15, a vapor tank 16 and a vapor outlet 17, as shown in fig. 7. In operation, the liquid in the wick 1 on the side close to the steam groove 16 absorbs the latent heat of vaporization of the heating rod, and the generated steam carries a large amount of heat through the steam groove 16, flows out from the steam outlet 17, and reaches the condenser through the steam connecting pipe. The vapor is liquefied after releasing latent heat of vaporization in the condenser, and is stored in the liquid compensation chamber 13 after reaching the liquid inlet 14 through the liquid connecting pipe. Under the action of the capillary suction force of the wick 1, the liquid reaches the vapor groove 16 side from the liquid compensation chamber 13 in the liquid flow direction, replenishing the consumed liquid. Since the temperature and pressure on the vapor tank 16 side are much higher than on the liquid compensation chamber 13 side, heat and generated vapor easily pass back through the wick 1 to the liquid compensation chamber 13, causing the loop heat pipe to fail to operate. When the bionic liquid absorption core 1 with the surface energy gradient is applied to an evaporator in a loop heat pipe, the bionic unit 2 close to one side of the steam groove 16 is a contact angle theta_1-1Far below 90 degrees of super-hydrophilic state, and the bionic unit 2 close to one side of the liquid compensation chamber has a contact angleθ_2-1A superhydrophobic state greater than 150 °. Liquid transport towards the superhydrophilic side is inhibited at the superhydrophobic side. Under the driving of the surface energy difference, the liquid in each stage of bionic unit 2 is quickly transmitted to one side of the steam tank 16 from one side of the liquid compensation chamber 13, and finally reaches the steam tank 16 under the relay of each stage of bionic unit 2. Due to the existence of the surface energy gradient, liquid and generated steam are difficult to reversely flow from the steam grooves 16 to the liquid compensation chamber 13, the bionic liquid suction core 1 has the function of a liquid diode, and the liquid-proof and steam-proof effects are more obvious. The existence of the surface energy gradient enables the capillary wick to have larger capillary suction force under the same pore condition, and under the condition of sufficient capillary suction force, the size of the unit pore control block 7 of the bionic wick 1 can be increased, the pore diameter of the wick 1 can be increased, and the liquid flow resistance can be reduced.

The above description is only a preferred embodiment of the present invention, and therefore should not be taken as limiting the scope of the invention, which is defined by the appended claims and their equivalents.

Claims

1. The utility model provides a bionic imbibition core of surface energy gradient which characterized in that: including a plurality of bionical units that three-dimensional array arranged, set up the guiding gutter on the bionical unit, the projection of guiding gutter is half ellipse, including inclined plane, curved surface and flange, the inclined plane just has the structure that the cell body degree of depth increases gradually along the liquid flow direction, the end-to-end connection on inclined plane has the curved surface, the curved surface is the concave surface in one side that is close to the inclined plane, and the upper end of curved surface is stretched back to the inclined plane direction and is formed the flange, the flange links up with the inclined plane level and smooth of next bionical unit.

2. A surface energy gradient biomimetic wick according to claim 1, wherein: the connecting part of the curved surface and the inclined surface is a fillet, and the radius of the fillet is 50-80 mu m.

3. A surface energy gradient biomimetic wick according to claim 2, wherein: the included angle between the inclined plane and the horizontal plane is 5-15 degrees, and the included angle between the curved surface tangent line of the flange and the inclined plane of the next bionic unit is 30-45 degrees.

4. A surface energy gradient biomimetic wick according to claim 1, wherein: the bionic unit further comprises an aperture control block, and the aperture control block is used for forming an aperture between the vertically adjacent bionic units.

5. A surface energy gradient biomimetic wick according to claim 4, wherein: the pore control block comprises a convex column which is arranged beside the diversion trench, and the width and the height of the convex column are 50-100 μm.

6. A surface energy gradient biomimetic wick according to claim 1 or 4, wherein: the bionic unit is mirror-symmetrical along the thickness direction.

7. A surface energy gradient biomimetic wick according to claim 1 or 4, wherein: the surface of the bionic unit is sunken in the axial direction of the guide groove from two sides to form a certain curvature.

8. A surface energy gradient biomimetic wick according to claim 4, wherein: the bionic units are arranged in parallel along the direction of the diversion trench in the transverse direction and are arranged in an aligned and stacked mode through the pore control blocks in the longitudinal direction.

9. Use of a surface energy gradient biomimetic wick according to any of claims 1-8 in a phase change heat dissipation device.

10. Use according to claim 9, characterized in that: the phase change heat dissipation device comprises a loop heat pipe.