A bionic heat pipe for enhanced heat transfer

Abstract

The present invention discloses a bionic heat transfer enhanced heat pipe, which comprises a pipe wall, a wick and a working medium filled in the pipe body and circulating in the pipe body. The wick is arranged on the inner side of the pipe wall. The heat pipe includes a condensation section, an evaporation section and an adiabatic section located between the condensation section and the evaporation section. Thread-shaped or annularly distributed protrusions are arranged on the outer wall surfaces of the condensation section and the evaporation section. The surface of the protrusion is a bionic surface, and the bionic surface is wavy. Bionic micropores extending inward from the top of the protrusion are arranged along the circumferential direction of the heat pipe on the bionic surface, and the bionic micropores are gradient holes with the pore diameter gradually decreasing from top to bottom. The present invention solves the problems of uneven heat conduction and low heat transfer efficiency existing when the heat pipe adopts a "Ω"-shaped wick, and enhances the heat transfer function of the heat pipe. This application is applicable to heat pipe systems related to energy including mobile small reactors, and can be widely applied to fields such as space, deep sea, medical emergency energy, etc., and has broad application prospects.

Description

Technical Field

[0001] The invention belongs to the field of energy including nuclear energy and the field of mechanical equipment, and specifically relates to a heat pipe with a bionic structure capable of enhancing heat transfer. Background Art

[0002] The heat pipe is a two-phase heat transfer device invented by the Los Alamos National Laboratory in the United States in the 1960s. It transfers heat through latent heat of vaporization and relies on capillary force, gravity, centripetal force and other effects to maintain the circulation of working fluids. It has a high heat transfer efficiency. It can be embedded in a metal plate for heat exchange, or fins can be added inside and outside the heat pipe for fluid heat exchange. Compared with traditional heat exchange forms, the use of heat pipe heat exchangers can achieve heat transfer through a small cross-sectional area over a long distance, and during the operation of the heat pipe, no external power or energy is required to drive it. In addition, the heat pipe also has the advantages of simple design and easy manufacturing. Based on the many advantages of heat pipe heat exchangers, the research and application scope of heat pipes is also expanding.

[0003] As early as the beginning of the 21st century, the University of New Mexico in the United States proposed the application of heat pipes to space reactor power systems. In recent years, countries around the world have carried out numerous studies on heat pipe cooling reactor solutions and key technologies, going through three historical stages: concept creation (1960-2000), active exploration (2000-2012), and major breakthroughs (2012 to present). A relatively complete spectrum of heat pipe cooling reactor design solutions in the power range of 1kW-10MW has been formed. In recent years, with the introduction of the concepts of "carbon peak and carbon neutrality" and the policy of "actively, safely and orderly developing nuclear power", heat pipe small reactors have gradually become a research hotspot at home and abroad. At present, most heat pipe cooling reactor designs are less than 200kW of electrical power. To some extent, this is related to the application history of heat pipe cooling reactor space nuclear energy. The typical power demand of early space nuclear power sources was 10-100kW. At present, more and more demands and application scenarios of nearly megawatts or above 1MW are emerging. In order to make the power of heat pipe cooled reactors reach near megawatt or megawatt level and be suitable for various applications, current research work mainly focuses on improving inherent safety and heat transfer efficiency. For small heat pipe reactors, improving their heat transfer performance can not only enhance economic benefits, but also provide protection for their inherent safety.

[0004] At present, the wick structures inside heat pipes have various forms, generally divided into two categories: single-structure wicks and composite-structure wicks. Among them, single-structure wicks include wound wire mesh wicks, metal sintered wicks, axial groove wicks, annular wicks, crescent wicks, main channel wicks, etc.; composite-structure wicks include wire mesh composite wicks, wire mesh covered groove wicks, plate-shaped main channel wicks, tunnel wicks, etc. A good wick requires high capillary pressure, low liquid flow resistance (i.e., high permeability), and large cross-sectional area. However, a large cross-sectional area of the wick increases the radial thermal resistance, which is not conducive to heat transfer. Taking the "Ω"-shaped wick in the axial groove wick as an example, the groove design makes its cross-section uneven in thickness. The groove part sunken towards the pipe wall is thinner, with a small thermal conduction resistance between it and the heat pipe wall, and good thermal conductivity. While the rest part is thicker, with poor thermal conductivity, resulting in low and uneven thermal conduction efficiency between the wick and the heat pipe, and poor economy and safety.

[0005] Therefore, in view of the above problems, by adopting bionic means, imitating the "sphenoparietal emissary foramen" structure for heat dissipation on the human skull and the folded structure of the African elephant ear, the structural optimization design of the heat pipe can be carried out to strengthen heat transfer and improve the economy and safety of the heat pipe heat exchanger. Summary of the Invention

[0006] The present invention provides a bionic enhanced heat transfer heat pipe, and its technical purpose is to solve the problems of uneven heat conduction and low heat transfer efficiency caused by the uneven thickness and large cross-sectional area unique to the groove structure when the heat pipe adopts a groove-type wick, and to strengthen the heat transfer function of the heat pipe.

[0007] The above technical purpose of the present invention is achieved through the following technical solutions:

[0008] A bionic enhanced heat transfer heat pipe, comprising a pipe wall, a wick, and a working fluid filled in the pipe body and circulating in the pipe body. The wick is arranged on the inner side of the pipe wall. The heat pipe includes a condensation section, an evaporation section, and an adiabatic section located between the condensation section and the evaporation section. It is characterized in that: there are raised portions distributed in a spiral or annular shape on the outer wall surfaces of the condensation section and the evaporation section; the surface of the raised portion is a bionic surface, and the bionic surface is wavy; there are bionic fine holes extending inward from the top of the raised portion along the circumferential direction of the heat pipe on the bionic surface, and the bionic fine holes are gradually changing holes with the aperture gradually decreasing from top to bottom.

[0009] Furthermore, the outer surfaces of the condensation section and the evaporation section are set as superhydrophobic surfaces, which are composed of a nano-coating. The nano-coating material is SiO2 or Al or Ti or V, and the contact angle θ of the superhydrophobic surface > 150°.

[0010] Furthermore, the wick is a "Ω"-shaped wick, and its structural design imitates the shape of a ruffled hem, that is, the convex part inside the heat pipe is arc-shaped, with the thinnest part having a thickness of 2 mm to 4 mm, the thickest part having a thickness of 7 mm to 10 mm, the radius of curvature of the convex part ranging from 2.5 mm to 3.5 mm, the radius of curvature of the groove part ranging from 1.5 mm to 2 mm, and the distance between two adjacent convex parts being 7 mm to 9 mm.

[0011] Furthermore, the fine hole extends inward to the inside of the convex part of the wick. Its shape imitates the "sphenoparietal emissary foramen" on the human skull and is conical, with a length of 7 mm to 10 mm, the tip diameter ranging from 0.5 mm to 1 mm, the root diameter ranging from 2 mm to 3 mm. At the same time, the tube wall part around the fine hole is recessed inward, with a diameter of 0.6 mm to 1 mm.

[0012] Furthermore, the folds are evenly distributed in a spiral shape, with a height of 3 mm to 4 mm and a bottom width of 4 mm to 6 mm. The fold shape imitates the ear of an African elephant and is an irregular wavy shape, composed of multiple arc-shaped protrusions with different radii of curvature and multiple arc-shaped grooves with different radii of curvature connected to each other. The radius of curvature of the largest arc-shaped protrusion ranges from 0.35 mm to 0.5 mm, the radius of curvature of the smallest arc-shaped protrusion ranges from 0.25 mm to 0.4 mm, the radius of curvature of the largest arc-shaped groove ranges from 0.3 mm to 0.4 mm, and the radius of curvature of the smallest arc-shaped groove ranges from 0.2 mm to 0.3 mm.

[0013] Furthermore, the thickness of the heat insulation sleeve is 3 mm to 7 mm; the wall thickness is 4 mm to 8 mm; the length of the heat insulation section is 200 mm to 400 mm; the length of the evaporation section is 300 mm to 600 mm; the length of the condensation section is 200 mm to 400 mm.

[0014] Furthermore, the material of the outer surface of the tube wall is 5A06 aluminum-magnesium alloy or graphene oxide.

[0015] Furthermore, the fine hole is located at the top of the triangular spiral fold. The position of the fine hole corresponds to each protrusion on the wick. The inwardly recessed tube wall part wraps the fine hole in a water droplet shape, with the minimum radius of curvature of the recessed part being 0.6 mm to 1.5 mm and the maximum radius of curvature being 1 mm to 2 mm.

[0016] The beneficial effects of the present invention are as follows: The heat pipe described in this application adopts a bionic means in its structural design, imitating the "sphenoparietal emissary foramen" structure on the human skull for connecting veins and the scalp for heat dissipation and the wrinkled structure of the African elephant ear for heat dissipation. The structures of the outer wall and the wick of the heat pipe are optimized. Fine pores are evenly distributed on its wall surface and extend inward to the inside of the protruding part of the wick. At the same time, the pipe wall part around the fine pores is recessed inward, and the wick and the pipe wall are locally thinned, making the radial heat transfer between the "Ω"-shaped wick and the pipe wall more uniform. At the same time, the heat transfer area between the pipe wall and the external flowing working medium is increased, enhancing the heat conduction between the wick and the heat pipe wall and the convective heat transfer between the heat pipe wall and the external working medium. At the same time, threaded and evenly distributed wrinkles are designed on the outer wall of the heat pipe to enhance convective heat transfer. At the sunken part of the wrinkled pipe wall surface, the heat conduction between the wick and the pipe wall is uneven, but compared with the protruding part of the wrinkles, the pipe wall is thinner and the heat loss is small during the heat conduction process, making the heat conduction in the axial direction of the pipe wall relatively uniform. This structure solves the problems of uneven heat conduction and low heat transfer efficiency existing when the heat pipe adopts the "Ω"-shaped wick, and strengthens the heat transfer function of the heat pipe. It has been proved that this structure can increase the heat transfer efficiency of the heat pipe by about 30%, and can further improve the economy and safety of the heat pipe heat exchanger. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic structural diagram of the bionic enhanced heat transfer heat pipe described in this application;

[0018] Figure 2 is Figure 1 the A-A sectional view of;

[0019] Figure 3 is Figure 1 the B-B sectional view of;

[0020] Figure 4 is Figure 1 the C-C sectional view of;

[0021] Figure 5 is Figure 2 the enlarged view of part A of;

[0022] Figure 6 is the schematic structural diagram of the wrinkles.

[0023] In the figure: 1 - pipe body; 2 - condensation section; 3 - adiabatic section; 4 - evaporation section; 5 - fine pores; 6 - wrinkles; 7 - liquid flow direction near the wick; 8 - gas flow direction inside the heat pipe; 9 - adiabatic sleeve; 10 - wick; 11 - condensation section pipe wall; 12 - adiabatic section pipe wall; 13 - evaporation section pipe wall; 14 - sunken part of the pipe wall around the fine pores; 15 - internal working medium of the heat pipe; H - height of the wrinkled structure; L - width of the wrinkled structure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] The technical solution of the present application will be described in detail below with reference to the accompanying drawings.

[0025] Figure 1 is a schematic structural diagram of the bionic enhanced heat transfer heat pipe described in the present application. In combination with Figure 2 , the heat pipe includes a pipe body 1. Inside the pipe body 1, a condensation section 2, an adiabatic section 3, and an evaporation section 4 are provided from left to right. The outer layers of the condensation section 2, the adiabatic section 3, and the evaporation section 4 are the condensation section pipe wall 11, the adiabatic section pipe wall 12, and the evaporation section pipe wall 13, with a thickness of 4 mm to 8 mm. The inner surface thereof is connected to a wick 10. An adiabatic sleeve 9 is provided outside the adiabatic section pipe wall 12, with a thickness of 3 mm to 7 mm. The length of the adiabatic section is 200 mm to 400 mm; the length of the evaporation section is 300 mm to 600 mm; the length of the condensation section is 200 mm to 400 mm

[0026] One end of the heat pipe pipe body 1 of the present application is the condensation section 2, and the other end of the pipe body 1 is the evaporation section 4. Between the condensation section 2 and the evaporation section 4 is the adiabatic section 3. The inner diameters of the three sections of the pipe are the same, and they are straight pipes. The pipe body 1 is filled with a circulating working fluid 15, and the type of the working fluid 15 in the heat pipe is determined according to the actual temperature requirements.

[0027] The present application involves the flow of external circulating media such as water, air, liquid metal, supercritical CO2, etc. outside the heat pipe.

[0028] The flow inside and outside the heat pipe of the present application can be in the same direction of co-current flow, or in the opposite direction of counter-current flow, or cross-flow. It can be forced circulation or natural circulation.

[0029] The materials of the condensation section pipe wall 11, the adiabatic section pipe wall 12, and the evaporation section pipe wall 13 of the heat pipe of the present application are Inconel-690 alloy or C71500 alloy. The Inconel-690 alloy has excellent intergranular corrosion resistance and intergranular stress corrosion cracking resistance. The high-purity C71500 alloy can resist cold deformation, hot deformation, and corrosion, and is more suitable for marine small reactor heat exchangers.

[0030] The outer surfaces of the condensation section pipe wall 11, the evaporation section pipe wall 13, and the adiabatic sleeve 9 of the heat pipe of the present application are coated with a nano-coating. The material of the nano-coating is SiO2, Al, Ti, or V. The nano-coating forms a superhydrophobic surface, and the contact angle θ of the superhydrophobic surface > 150°, having the function of preventing particle deposition.

[0031] The wick 10 of the heat pipe of the present application is a "Ω"-shaped wick, and its structural design imitates the shape of a lotus leaf edge, that is, the convex part towards the inside of the heat pipe is arc-shaped, with the thinnest part having a thickness of 2 mm to 4 mm and the thickest part having a thickness of 7 mm to 10 mm. The radius of curvature of the convex part ranges from 2.5 mm to 3.5 mm, and the radius of curvature of the groove part ranges from 1.5 mm to 2 mm. The distance between two adjacent convex parts is 7 mm to 9 mm. See Figure 4as shown

[0032] On the outer surfaces of the tube wall 11 of the condensation section and the tube wall 13 of the evaporation section of the present application, there are uniformly arranged wrinkles 6 in a threaded shape. The shape of the wrinkles 6 is designed by imitating the wrinkled structure of the African elephant ear, and is an irregular wave shape. Refer to Figure 5 , the height H of the wrinkles 6 is 3 mm to 4 mm, and the bottom width L is 4 mm to 6 mm. Its height is 3 mm to 4 mm, and the bottom width is 4 mm to 6 mm. The wrinkles 6 are formed by connecting a plurality of arc-shaped protrusions with different radii of curvature and a plurality of arc-shaped grooves with different radii of curvature. The range of the radius of curvature of the largest arc-shaped protrusion is 0.35 mm to 0.5 mm, the range of the radius of curvature of the smallest arc-shaped protrusion is 0.25 mm to 0.4 mm, the range of the radius of curvature of the largest arc-shaped groove is 0.3 mm to 0.4 mm, and the range of the radius of curvature of the smallest arc-shaped groove is 0.2 mm to 0.3 mm.

[0033] In one embodiment, the wrinkles 6 are of a symmetric structure, and the top of the wrinkles 6 is an arc-shaped protrusion. The protrusions and grooves of the wrinkles 6 are both circular arcs, and the circular arcs of the protrusions and grooves are smoothly transitioned. The radii of the circular arcs of the protrusions and grooves on one side of the wrinkles 6 are respectively: R1, R2, R3, R4, R5, R6, R7, R8, and the sizes of R1 to R8 are respectively: 0.2 mm to 0.3 mm, 0.15 mm to 0.25 mm, 0.12 mm to 0.2 mm, 0.1 mm to 0.15 mm, 0.3 mm to 0.6 mm, 0.25 mm to 0.5 mm, 0.15 mm to 0.2 mm, 0.2 mm to 0.3 mm. Refer to Figure 6 .

[0034] At the tip of the wrinkles 6, there are bionic fine holes 5 corresponding to each protrusion on the wick 10. The shape of the bionic fine holes 5 is designed by imitating the structure of the "sphenoparietal emissary foramen" on the human skull. The length of the bionic fine holes 5 is 7 mm to 10 mm, the diameter of the tip part is 0.5 mm to 1 mm, and the range of the root diameter is 2 mm to 3 mm. At the same time, on the inner surface part of the condensation section tube wall 11 and the evaporation section tube wall 13 around the bionic fine holes 5, there are water droplet-shaped protrusions, and the water droplet-shaped protrusions extend into the wick 10, and the water droplet-shaped protrusions wrap the lower end of the bionic fine holes 5.

[0035] In one embodiment, the minimum radius of curvature of the water droplet-shaped protrusion is 0.6 mm to 1.5 mm, and the maximum radius of curvature is 1 mm to 2 mm. See specifically Figure 5 as shown

[0036] At the wrinkled and sunken part of the heat pipe wall surface of the present application, such as Figure 4 as shown, the heat conduction between the wick 10 and the tube wall 11 is uneven, but relative to Figure 3 the wrinkled and protruding part shown, the tube wall is thinner, and the heat loss is small during the heat conduction process, so that the heat conduction in the axial direction of the tube wall is relatively uniform.

[0037] For the bionic enhanced heat transfer heat pipe described in this application, its working principle is as follows: After the vapor runs to the condensation section 2 and releases heat, it condenses into a liquid working medium. The liquid working medium in the condensation section 2 flows back to the evaporation section 4 under the action of the capillary driving force generated by the wick 10, and a new cycle begins. Such continuous cycling efficiently transfers heat from the evaporation section 4 to the condensation section 2. External heat is absorbed by the low-temperature evaporation section 4, and internal heat is discharged from the condensation section 2 to the outside of the pipe.

[0038] The above is a demonstration embodiment of this application, and the protection scope of this application is defined by the claims and their equivalents.

Claims

1. A bionic enhanced heat transfer heat pipe, comprising a pipe wall, a wick, and a working fluid filled in the pipe body and circulating in the pipe body. The wick is arranged on the inner side of the pipe wall. The heat pipe includes a condensation section, an evaporation section, and an adiabatic section located between the condensation section and the evaporation section. It is characterized in that: There are raised portions distributed in a spiral or annular shape on the outer wall surfaces of the condensation section and the evaporation section; the surface of the raised portion is a biomimetic surface, and the biomimetic surface is wavy; along the circumferential direction of the heat pipe, biomimetic micropores extending inward from the top of the raised portion are arranged on the biomimetic surface, and the biomimetic micropores are tapered holes with a gradually decreasing aperture from top to bottom; The biomimetic surface is composed of a plurality of arc-shaped raised portions with different curvature radii and a plurality of arc-shaped grooves with different curvature radii connected to each other. The curvature radius range of the largest arc-shaped raised portion is 0.35 mm to 0.5 mm, the curvature radius range of the smallest arc-shaped raised portion is 0.25 mm to 0.4 mm, the curvature radius range of the largest arc-shaped groove is 0.3 mm to 0.4 mm, and the curvature radius range of the smallest arc-shaped groove is 0.2 mm to 0.3 mm; The outer surfaces of the condensation section and the evaporation section are superhydrophobic surfaces.

2. The bionic enhanced heat transfer heat pipe according to claim 1, characterized in that: The height of the biomimetic surface is 3 mm to 4 mm, and the bottom width of the raised portion is 4 mm to 6 mm.

3. The bionic enhanced heat transfer heat pipe according to claim 1, wherein: The wick is a "Ω"-shaped wick, and the convex portion of the "Ω"-shaped wick facing the inside of the heat pipe is arc-shaped.

4. The bionic enhanced heat transfer heat pipe according to claim 3, characterized in that: The thickness of the thinnest part of the "Ω"-shaped wick is 2 mm to 4 mm, the thickness of the thickest part is 7 mm to 10 mm, the curvature radius range of the raised portion is 2.5 mm to 3.5 mm, the curvature radius range of the groove portion is 1.5 mm to 2 mm, and the distance between adjacent raised portions is 7 mm to 9 mm.

5. The bionic enhanced heat transfer heat pipe according to claim 1, characterized in that: The biomimetic micropores extend inward to the inside of the convex portion of the wick; the shape of the biomimetic micropores is conical, the length of the biomimetic micropores is 7 mm to 10 mm, the tip diameter range of the biomimetic micropores is 0.5 mm to 1 mm, and the root diameter range is 2 mm to 3 mm.

6. The bionic enhanced heat transfer heat pipe according to claim 5, characterized in that: There are water droplet-shaped raised portions on the inner surface parts of the condensation section pipe wall and the evaporation section pipe wall around the biomimetic micropores, and the water droplet-shaped raised portions extend into the wick; the minimum curvature radius of the concave portion is 0.6 mm to 1.5 mm, and the maximum curvature radius is 1 mm to 2 mm.

7. The bionic enhanced heat transfer heat pipe according to claim 1, wherein: An adiabatic sleeve is arranged on the adiabatic section of the heat pipe.

8. The bionic enhanced heat transfer heat pipe according to claim 7, wherein: The thickness of the adiabatic sleeve is 3 mm to 7 mm; the wall thickness is 4 mm to 8 mm; the length of the adiabatic section is 200 mm to 400 mm; the length of the evaporation section is 300 mm to 600 mm; the length of the condensation section is 200 mm to 400 mm.

9. The bionic enhanced heat transfer heat pipe according to claim 1, wherein: The material of the outer surface of the pipe wall is 5A06 aluminum-magnesium alloy or graphene oxide.

10. The bionic enhanced heat transfer heat pipe according to claim 1, wherein: The superhydrophobic surface is composed of a nano-coating, the contact angle θ > 150°, and the nano-coating material is SiO2 or Al or Ti or V.

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