CN111548024B

CN111548024B - Method for splitting bubbles by monofilaments on in-plane superhydrophobic rail

Info

Publication number: CN111548024B
Application number: CN202010440367.0A
Authority: CN
Inventors: 叶煜航; 凃程旭; 包福兵; 汪钰琨; 尹招琴; 蒋仁杰; 杨蒙
Original assignee: China Jiliang University
Current assignee: China Jiliang University
Priority date: 2020-05-22
Filing date: 2020-05-22
Publication date: 2022-06-21
Anticipated expiration: 2040-05-22
Also published as: CN111548024A

Abstract

The invention discloses a method for splitting bubbles by monofilaments on an in-plane superhydrophobic rail. Firstly, manufacturing linear tracks with equal width and super-hydrophobic property on a planar substrate, so that other planar areas of the substrate except for the track area are non-hydrophobic surfaces; secondly, the monofilament is used as a substrate, and a super-hydrophobic solution is sprayed to form the monofilament with super-hydrophobicity, and the monofilament is fixed at a position away from the linear track by a set distance; then the linear track is placed in water in parallel to the gravity direction and is positioned in the same horizontal plane with the bubble production position; when the bubbles pass through the monofilaments, the bubbles are adhered, sheared and torn under the action of the capillary force and the wall adhesion force of the monofilaments to form new bubbles with smaller diameters, so that the bubbles are split and the aim of generating micro bubbles is fulfilled. The invention has simple preparation and low cost, and can quickly obtain micro bubbles on the open wall surface.

Description

Method for splitting bubbles by monofilaments on in-plane superhydrophobic rail

Technical Field

The invention belongs to the technical field of multiphase flow, and particularly relates to segmentation of moving bubbles on an open-wall super-hydrophobic track, which is used for regulating and splitting rising bubbles in liquid fluid to obtain more tiny bubbles.

Background

Bubbles are widely used in engineering equipment and technical fields of petrochemical industry, energy, ship manufacturing, sewage treatment and the like, and the volume of the rising bubbles in the liquid fluid plays an important role in the processes of mineral foam flotation, a bubbling reactor, sewage treatment, hydraulic resistance reduction, cell incubation and the like. During froth flotation, the longer the retention time and the movement process of bubbles in a liquid phase are, the more beneficial the mineral flotation is; in contrast, in microfluidic and heat exchange systems, faster gas bubble exit is required. By changing the size of the bubble, not only the moving speed of the bubble but also the size of the specific surface area can be changed. The reaction efficiency is greatly improved by increasing the specific surface area and thus increasing the contact area of the physical/chemical reaction.

Although micro bubbles can be generated by the microfluidic experimental device, the generated bubbles are limited to move in the micro channel by the method, and the microfluidic experimental device has the condition that the bubbles cannot be generated due to the blockage of a pipeline. Compared with bubbles in a limited space generated by microfluidics, the bubbles on the open wall surface have larger specific surface area and freedom of movement, and the characteristics are very critical to the performance of the bubbles in the aspects of chemical reaction, mass transfer and heat transfer, so that how to generate micro bubbles on the open wall surface is very important.

Disclosure of Invention

In order to solve the problems, the invention provides a method for cutting bubbles without energy input, wherein the bubbles move on a super-hydrophobic track under the action of buoyancy, and when passing through a super-hydrophobic monofilament which is away from the plane of the track by a certain distance, the bubbles are cut by the monofilament to realize the control of bubble division.

The technical scheme adopted by the invention for solving the technical problem is as follows:

the linear tracks with super-hydrophobic property are made in the same width on the plane substrate, so that the other substrate plane areas except the track area are non-hydrophobic surfaces.

The monofilament is used as a substrate, the super-hydrophobic solution is sprayed to form the monofilament with super-hydrophobicity, and the monofilament is fixed at a set distance from a linear track, is parallel to the plane of the track and is vertical to the track.

The linear track is placed in the water in parallel to the gravity direction, and the distance between the linear track and the nozzle at the bubble production position is smaller than the equivalent diameter of the bubble volume.

When the bubbles pass through the monofilaments, the bubbles are adhered, sheared and torn to form new bubbles with smaller diameter, so that the bubbles are split and the aim of generating micro bubbles is fulfilled.

The diameter of the monofilament is 0.01-0.3D, the track width is 0.1D-1.5D, the distance between the monofilament and the track is 0.1D-2D, and D is the equivalent diameter of the bubble volume.

Further, the bottom end position of the track is placed in a range of 0 to 3 times the characteristic length of the bubble from the bubble generation site in the horizontal direction.

Furthermore, the contact angle of the liquid drop of the straight-line orbit with the super-hydrophobic property is 150-180 degrees, and the minimum sliding angle is not more than 5 degrees.

Compared with the prior art, the invention has the beneficial effects that:

(1) the invention has simple preparation and low cost, and can quickly obtain micro bubbles on the open wall surface.

(2) The invention divides a large bubble into a plurality of small bubbles, and the specific surface area of the generated small bubbles is large.

(3) The present invention can change the size of the bubbles after splitting by changing the initial bubble diameter.

(4) The invention can change the size of the split air bubbles by changing the distance between the super-hydrophobic monofilaments and the super-hydrophobic tracks.

(5) The invention can generate micro-bubbles with the diameter less than 1mm on the open wall surface.

Drawings

FIG. 1 is a schematic view of a superhydrophobic rail wall;

FIG. 2 is a schematic representation of a superhydrophobic monofilament;

FIG. 3 is a schematic view of a monofilament split bubble apparatus;

FIG. 4 is a side view of a monofilament split bubble apparatus;

FIG. 5 is a front view of a monofilament split bubble apparatus;

FIG. 6 is a schematic view of a monofilament split bubble.

Detailed Description

The invention is further illustrated with reference to the following figures and examples.

The invention obtains the linear track with equal width and super-hydrophobic property by designing and manufacturing on a plane substrate, so that other substrate plane areas except the super-hydrophobic track area are non-hydrophobic surfaces, then, the monofilament with the diameter d is used as the substrate, and super-hydrophobic solution is sprayed to form the monofilament with super-hydrophobicity, and the monofilament is fixed at a certain distance L away from the track.

When the super-hydrophobic rail is touched, the bubbles quickly spread at the bottom end of the rail due to super-hydrophilicity of the super-hydrophobic rail, form a stable non-spherical shape under the action of surface tension, are finally stably adsorbed on the rail, and move linearly upwards along the rail under the action of buoyancy, capillary force and the like.

The bubbles float upwards along the track, and when passing through the monofilaments, the bubbles are adhered under the action of the capillary force and the wall adhesion force of the super-hydrophobic monofilaments, and because the moving speed of the bubbles on the track is higher, the bubbles are sheared and torn in the process to form new bubbles with smaller diameter, so that the bubbles are split, and the aim of generating micro bubbles is fulfilled. The preparation of the micro bubbles is finished, and the micro bubbles can be applied to and researched by subsequent engineering. Under the same bubble diameter D, the size of the split bubbles can be effectively adjusted by changing the width W of the track, the diameter D of the monofilament and the distance L between the monofilament and the track, and under the condition that other parameters are constant, the smaller the track width W is, the smaller the generated micro bubbles are; the smaller the monofilament diameter d is, the smaller the generated micro-bubbles are; the larger the distance L between the monofilament and the track is, the smaller the generated splitting micro-bubbles are; specifically, the size of the split bubbles can be adjusted by changing the diameter of the initial bubbles of the monofilament-type track with the same specification, and the generated bubbles are reduced along with the reduction of the initial diameter.

The air bubbles are any air bubbles, the diameter D of each monofilament is 0.01-0.3D, the width W of the super-hydrophobic track is 0.1-1.5D, the distance L between each monofilament and each track is 0.1-2D, the tracks and the monofilaments can be different super-hydrophobic surfaces, the contact angle of liquid drops of the super-hydrophobic tracks is 150-180 degrees, the wall surface of the super-hydrophobic substrate can be glass, metal, acrylic and other hydrophilic engineering materials, the super-hydrophobic monofilament substrate can be a nylon rope, glass and other hydrophilic engineering materials, and the thickness of the super-hydrophobic tracks is less than 0.1 mm; the fluid may be a Newtonian or non-Newtonian fluid.

Examples

As shown in fig. 1, 2 and 3, a planar substrate 1 is selected, the surface of the substrate is cleaned, a desired bubble movement track is reserved on the surface of the substrate, a monofilament substrate 2 is selected, the surface of the monofilament substrate is cleaned, the monofilament substrate and the monofilament substrate are respectively sprayed with a super-hydrophobic solution, a super-hydrophobic coating 3 with smooth surface and edge is obtained, and the hydrophobic property of the surface of the substrate is obviously improved.

In order to ensure that the bubbles have good adhesion on the substrate material, a super-hydrophobic surface layer with a thickness of about 0.1mm, smooth surface and two sides and good hydrophobic property is formed on the surface of the substrate material.

In this example, a glass plate is used as a substrate, a super-hydrophobic coating is sprayed on the substrate, the contact angle is 160 degrees, and the redundant part of the edge of the super-hydrophobic coating is removed by wiping. Let the characteristic length of the controlled bubble be D, the bubble rise track width W be plotted as 0.5D, the monofilament diameter D be plotted as 0.05D, and the track-to-monofilament spacing L = D. The super-hydrophobic rail is placed in water in parallel to the gravity direction and is located in the same horizontal plane with the bubble production position, the bottom end of the rail is placed in the range of 0 to 3 times of the characteristic length of the bubbles away from the bubble generation position in the horizontal direction, and the bubbles in the water can be conveniently captured, so that the bubble track in the water can be conveniently captured. Secondly, the superhydrophobic monofilaments are placed on a horizontal plane and are parallel to the superhydrophobic track plane, and the distance between the superhydrophobic monofilaments and the track plane is L = D, so that the movement direction of the bubbles is perpendicular to the superhydrophobic monofilaments as shown in figures 3, 4 and 5. The bubbles float upwards under the action of buoyancy, the bubbles adhere to the tracks and float upwards linearly along the tracks due to the super-hydrophilicity of the super-hydrophobic tracks, and when the bubbles move to the positions near the super-hydrophobic monofilaments, the bubbles are pulled and deformed under the action of monofilament adhesion force and the like. With the upward floating motion of the bubble, the monofilament cuts the large bubble into two individual small bubbles, as shown in fig. 6. The preparation of the micro bubbles on the open wall surface is completed, and the micro bubbles can be applied and researched in subsequent engineering.

In conclusion, the invention has the advantages of no need of energy input, simple preparation and low cost, can quickly obtain micro bubbles on the open wall surface, can adjust the size of the split bubbles by changing the width of the track and the distance between the track and the monofilament according to the requirements of different scenes, increases the contact area of physical/chemical reaction due to small volume and large specific surface area of the micro bubbles generated by splitting one bubble, greatly improves the reaction efficiency and enriches the generation method of the micro bubbles.

Claims

1. The method for splitting bubbles by monofilaments on an in-plane superhydrophobic rail is characterized by comprising the following steps of:

manufacturing linear tracks with equal width and super-hydrophobic property on a planar substrate, so that other planar regions of the substrate except for the track region are non-hydrophobic surfaces;

the method comprises the following steps of (1) spraying a super-hydrophobic solution by using a monofilament as a substrate to form a super-hydrophobic monofilament, fixing the super-hydrophobic monofilament at a position away from a linear track by a set distance, wherein the position is parallel to a plane of the linear track and is vertical to the linear track;

placing the linear track in water in parallel to the gravity direction, wherein the distance between the linear track and a nozzle at the bubble production position is smaller than the equivalent diameter of the bubble volume;

when the bubbles pass through the monofilaments, the bubbles are adhered, sheared and torn to form new bubbles with smaller diameter, so that the bubbles are split and the aim of generating micro bubbles is fulfilled;

2. The method for splitting bubbles by monofilaments on an in-plane superhydrophobic rail of claim 1, wherein: the bottom position of the track is placed in the range of 0 to 3 times the characteristic length of the bubble from the bubble generation place in the horizontal direction.

3. The method for splitting bubbles by monofilaments on an in-plane superhydrophobic rail of claim 1, wherein: the contact angle of the liquid drop of the straight-line track with the super-hydrophobic property is 150-180 degrees.