A gradient structure for enhancing liquid reflux on the inner wall of a heat pipe

Abstract

The present invention discloses a gradient structure for strengthening the liquid reflux on the inner wall of a heat pipe, including semi-conical grooves arranged at equal intervals around the inner wall of the heat pipe, a raised inner wall formed between two adjacent semi-conical grooves; the notch of the semi-conical groove is a narrowing mouth from the condensation section to the evaporation section; the semi-conical groove and the raised inner wall share an edge line; at the condensation section, the semi-conical groove with a narrowing mouth serves as a droplet condensation reflux groove, and the corresponding heat pipe has a channel formed by the raised inner wall to the inside of the heat pipe as a steam rising channel. The present invention combines a conical condensation surface with a groove-shaped liquid guide structure, comprehensively considers the coupling of steam condensation, condensate movement, conical structure morphology, and internal heat transfer, realizes the rapid nucleation of steam on the heat exchange surface and the directional movement of condensate, does not rely on other external field effects, and only relies on the surface structure or surface chemical properties to achieve the directional movement of droplets, accelerates the efficiency of liquid condensation reflux, and strengthens the heat transfer capacity of the heat pipe.

Description

Technical Field

[0001] The invention belongs to the field of heat pipes, and in particular relates to a gradient structure for strengthening liquid reflux on the inner wall of a heat pipe. Background Art

[0002] The phenomenon of condensation heat transfer is widely present in nature and in industrial applications such as aviation, power generation, chemical industry, air conditioning and HVAC engineering. Heat pipes transfer heat by phase change of working fluids. Their working principle is: in the evaporation section of the heated heat pipe, the liquid working fluid in the tube core evaporates and takes away heat, which is the latent heat of evaporation of the working fluid. The steam flows from the central channel to the condensation section of the heat pipe, condenses to form liquid, and releases latent heat at the same time. Under the action of gravity, the liquid flows back to the evaporation section, and the cycle repeats to transfer heat from the evaporation section to the condensation section.

[0003] When hot steam contacts a wall with a temperature lower than its own saturation temperature, the steam will undergo a phase change to release latent heat and condense into liquid. When the condensed water covers the condensation surface, the steam will undergo a phase change to release latent heat and condense into liquid. The condensed water covers the condensation surface, which hinders the heat transfer between the steam and the condensation surface. Therefore, the condensed liquid needs to be quickly separated. The existing methods for directional movement of droplets are as follows: (1) Surface acoustic wave vibration drive. For surface acoustic wave induced droplet transport, its basic principle is that the high-frequency vibration generated by the transducer is transmitted along the surface in the form of surface waves. When the surface wave encounters the droplets on the surface, part of the energy of the surface acoustic wave will be transferred to the droplets, and the droplets will achieve directional transport in the continuous unidirectional vibration transmission. However, since the energy of the surface acoustic wave will decay with the increase of distance, it is not suitable for long-distance droplet transport. (2) Magnetic field drive based on magnetic field. The directional transport of droplets under the action of magnetic field can be divided into three categories according to the position of the magnetic field, namely, the magnetic field acts on the inside, surface and outside of the droplets. The magnetic field acts on the inside of the droplet mainly by means of ball traction, that is, a paramagnetic metal ball is placed inside the droplet, and the interaction between the droplet and the ball is used to pull the droplet to move with the ball. The magnetic field acts on the surface of the droplet through droplet marbles, which are droplets wrapped by hydrophobic particles. By adding magnetic particles to the hydrophobic particles, the magnetic field can control the liquid marbles. The magnetic field acts on the outside of the droplet mainly refers to the effect of the magnetic field on the wettable surface, that is, magnetic particles are added to the wettable surface, so that the surface morphology changes under the action of the magnetic field, thereby driving the droplet to move. (3) Droplet self-drive with wettability gradient on the component surface. The wettability gradient on the component surface is to adjust the chemical composition of the solid substrate or prepare microscale / nanoscale structures to change the equilibrium contact angle of the substrate. The difference in contact angle between the front and back surfaces of the droplet causes it to move.

[0004] In existing industrial sound field scenarios, there is a widespread demand for water vapor condensation heat transfer under low pressure or vacuum conditions. The condensation and separation of droplets on the inner wall of the heat pipe are more difficult than condensation at normal pressure. The condensate in the inner wall of the traditional heat pipe is easy to adhere to the inner wall to form a liquid film. At the same time, there will be a hysteresis phenomenon of condensation contact angle. The droplets are pinned on the surface and cannot slide off, resulting in deterioration of heat transfer on the condensation surface. In addition, the existing droplet-driven accelerated reflux methods are mainly divided into active droplet transport with external field application and droplet self-drive. The driving method through external energy input is often complex in equipment, and the external energy will inevitably cause pollution and damage to the liquid and surface. The preparation method for constructing a surface wettability gradient is relatively complex, and the surface durability is low. Currently, most related research can only be completed in laboratory scenarios. Summary of the invention

[0005] The present invention provides a gradient structure for enhancing liquid reflux on the inner wall of a heat pipe. Specifically, an array of semi-conical grooves is manufactured on the condensation reflux surface of the heat pipe. The condensation reflux is subjected to a radial pressure difference on the cross section, and the pressure difference increases as the radius decreases. Due to the vapor pressure on the outer side of the heat pipe, each liquid film cross section generates a pressure gradient pointing to the smaller radius end. The Laplace pressure difference formed by the curvature of the liquid film at different cross sections of the inner conical groove is utilized to realize self-driven transport of the liquid film, thereby enhancing the liquid reflux on the inner wall of the heat pipe and solving the above problems.

[0006] In order to solve the above technical problems, the present invention is achieved through the following technical solutions:

[0007] A gradient structure for enhancing liquid reflux on the inner wall of a heat pipe of the present invention is arranged on the inner wall of the heat pipe, one end of the heat pipe is a condensation section, and the other end is an evaporation section; the gradient structure comprises semi-conical grooves arranged at equal intervals around the inner wall of the heat pipe, and a convex inner wall is formed between two adjacent semi-conical grooves;

[0008] The notch of the semi-conical groove is a narrowing mouth from the condensation section to the evaporation section;

[0009] The semi-conical groove and the inner wall of the protrusion share a common edge line.

[0010] Furthermore, the groove center axis of the semi-conical groove is parallel to the center axis of the heat pipe.

[0011] Furthermore, the number of the semi-conical grooves is the same as the number of the protruding inner walls.

[0012] Furthermore, at the condensation section, the semi-conical groove with a narrowed mouth serves as a droplet condensation reflux groove, and the corresponding channel in the heat pipe formed by the raised inner wall to the inside of the heat pipe serves as a steam rising channel.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] (1) The present invention combines a conical condensation surface with a grooved liquid guide structure, comprehensively considers the coupling of steam condensation, condensate movement, conical structure morphology, and internal heat transfer, and realizes rapid nucleation of steam on the heat exchange surface and directional movement of condensate;

[0015] (2) The semi-conical groove designed in the heat pipe of the present invention makes the condensation reflux subject to radial pressure difference on the cross section, and the pressure difference increases as the radius decreases. Due to the vapor pressure on the outer side of the heat pipe, each liquid film cross section generates a pressure gradient pointing to the end with a smaller radius. The Laplace pressure difference formed by the curvature of the liquid film in different cross sections of the inner conical groove is used to realize the self-driven transportation of the liquid film, thereby strengthening the liquid reflux on the inner wall of the heat pipe and strengthening the heat exchange on the condensation surface.

[0016] (3) The present invention does not need to rely on other external fields, but only relies on the surface structure or surface chemical properties to achieve directional movement of droplets. The Laplace pressure difference formed by the curvature of the liquid film in different cross sections of the inner conical groove is used to form a self-driving liquid film, so that the liquid film can be efficiently collected under the dual effects of partial gravity and self-driving force, thereby accelerating the condensation reflux efficiency of the liquid and enhancing the heat transfer capacity of the heat pipe.

[0017] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0019] Figure 1 It is a schematic structural diagram of a combination of a gradient structure for enhancing liquid reflux on the inner wall of a heat pipe and a heat pipe according to the present invention;

[0020] Figure 2 for Figure 1 Section view in ;

[0021] Figure 3 for Figure 1 Structural perspective drawing of

[0022] Figure 4 The schematic diagram of the self-driving of the liquid film in the conical groove corresponding to the present invention;

[0023] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0024] 1-heat pipe, 2-condensation section, 3-semi-conical groove, 4-convex inner wall, 5-evaporation section, A-droplet condensation reflux groove, B-steam rising channel. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] In the description of the present invention, it is necessary to understand that the terms "one end", "the other end", "parallel", "inner wall", "center of a circle" and the like indicating orientation or positional relationship are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the components or elements referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0027] The present invention aims to strengthen the liquid reflux on the inner wall of the heat pipe, and focuses on manufacturing a semi-conical groove array on the condensation reflux surface of the heat pipe, and utilizing the Laplace pressure difference formed by the curvature of the liquid film of different cross sections of the inner conical groove to realize the self-driven transportation of the liquid film, thereby strengthening the liquid reflux on the inner wall of the heat pipe. The specific scheme of the present invention is:

[0028] See also Figure 1-4 As shown, a gradient structure for enhancing liquid reflux on the inner wall of a heat pipe of the present invention is arranged on the inner wall of a heat pipe 1, one end of the heat pipe 1 is a condensation section 2, and the other end is an evaporation section 5;

[0029] The gradient structure includes semi-conical grooves 3 arranged at equal intervals around the inner wall of the heat pipe 1, and a convex inner wall 4 is formed between two adjacent semi-conical grooves 3; Figure 2 As shown, in this specific embodiment, the diameter of the heat pipe 1 is 12 mm, the wall thickness of the heat pipe is 0.6 mm, the number of the semi-conical grooves 3 is eight, and the number of the semi-conical grooves 3 is the same as the number of the raised inner walls 4;

[0030] The notch of the semi-conical groove 3 is a narrowing opening from the condensation section 2 to the evaporation section 5;

[0031] The semi-conical groove 3 and the raised inner wall 4 share a common edge line.

[0032] The center axis of the semi-conical groove 3 is parallel to the center axis of the heat pipe 1 .

[0033] Among them, at the position of the condensation section 2, the semi-conical groove 3 with a narrowed mouth serves as a droplet condensation reflux groove A, and the corresponding channel in the heat pipe 1 formed by the raised inner wall 4 to the inside of the heat pipe serves as a steam rising channel B.

[0034] The principle diagram of the self-driving of the conical tank liquid film is as follows Figure 4 shown.

[0035] During specific operation: when the heat pipe 1 starts to work, the working fluid is heated and vaporized in the evaporation section 5, the steam rises in the heat pipe 1, passes through the insulation section, condenses and liquefies in the condensation section 2, and the droplets flow back to the evaporation section 5 along the semi-conical groove 3 on the inner wall; the discharge of the small end of the conical groove is ideal, and the liquid will not accumulate at the tip. At this time, there will be a uniform thin liquid film on the semi-conical groove 3. Since the liquid film is thin, the shape of its cross section can be considered to be similar to the shape of the wall of the semi-conical groove 3, that is, the surface of the liquid film is also a semi-conical surface, and the semi-conical groove structure has a gradient effect, and the radius of the liquid film is also smaller as the radius of the conical groove decreases. Since the generatrix of the conical groove is horizontal, the axial curvature hardly changes, and the Laplace force on the curved liquid surface on the cross section only has a radial component pointing to the center of the cross section. As the radius of the curved liquid surface on the cross section decreases, its radial Laplace pressure difference becomes larger and larger, so that a pressure gradient pointing to the direction of the smaller radius is generated in each liquid film cross section, forming a self-driven transport of the liquid film on a macro scale.

[0036] Compared with the existing technology, the inner wall structure of the semi-conical groove has a significantly reduced system complexity, does not need to rely on other external field effects, will not pollute the condensate, and has a stronger condensation heat exchange capacity.

[0037] The present invention does not need to rely on other external fields, and can achieve directional movement of droplets only by relying on surface structure or surface chemical properties; the Laplace pressure difference formed by the curvature of the liquid film in different cross sections of the inner conical groove is used to form liquid film self-drive, so that the liquid film can be efficiently collected under the dual effects of partial gravity and self-drive force, thereby accelerating the liquid condensation reflux efficiency and enhancing the heat transfer capacity of the heat pipe.

[0038] The present invention combines the semi-conical groove structure with the inner wall reflux of the heat pipe for the first time, realizes the accelerated dripping reflux of the droplets, and enhances the heat exchange capacity of the heat pipe. The key point of the present invention is to process the semi-conical groove array on the inner wall of the heat pipe, and use the Laplace pressure difference formed by the curvature of the liquid film of different sections of the inner conical groove to form a self-driven liquid film, strengthen the condensate reflux to the evaporation section, speed up the heat exchange process of the entire heat pipe, and thus improve the heat exchange efficiency. Compared with the prior art, the inner wall structure of the semi-conical groove has a significantly reduced complexity of the design system, does not need to rely on other external fields, will not pollute the condensate, and has a stronger condensation heat exchange capacity.

[0039] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A gradient structure for enhancing liquid reflux on the inner wall of a heat pipe, arranged on the inner wall of a heat pipe (1), wherein one end of the heat pipe (1) is a condensation section (2) and the other end is an evaporation section (5), characterized in that: The gradient structure comprises semi-conical grooves (3) arranged at equal intervals around the inner wall of the heat pipe (1), and a convex inner wall (4) is formed between two adjacent semi-conical grooves (3); The notch of the semi-conical groove (3) is a narrowing opening from the condensation section (2) to the evaporation section (5); The semi-conical groove (3) and the raised inner wall (4) share a common edge line.

2. A gradient structure for enhancing liquid reflux on the inner wall of a heat pipe according to claim 1, characterized in that: The groove center axis of the semi-conical groove (3) is parallel to the circle center axis of the heat pipe (1).

3. The gradient structure for enhancing liquid reflux on the inner wall of a heat pipe according to claim 1, characterized in that: The number of the semi-conical grooves (3) is the same as the number of the raised inner walls (4).

4. The gradient structure for enhancing liquid reflux on the inner wall of a heat pipe according to claim 1, characterized in that: At the position of the condensation section (2), the semi-conical groove (3) with a narrowed mouth serves as a droplet condensation reflux groove (A), and the corresponding channel in the heat pipe (1) formed by the raised inner wall (4) toward the inside of the heat pipe serves as a steam rising channel (B).

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