CN110849167A - Preparation method of carbon nanotube film net structure for enhancing water vapor condensation - Google Patents
Preparation method of carbon nanotube film net structure for enhancing water vapor condensation Download PDFInfo
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- CN110849167A CN110849167A CN201911002477.2A CN201911002477A CN110849167A CN 110849167 A CN110849167 A CN 110849167A CN 201911002477 A CN201911002477 A CN 201911002477A CN 110849167 A CN110849167 A CN 110849167A
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28B—STEAM OR VAPOUR CONDENSERS
- F28B3/00—Condensers in which the steam or vapour comes into direct contact with the cooling medium
Abstract
A preparation method of a three-dimensional carbon nanotube film network structure for reinforcing water vapor condensation belongs to the technical field of water vapor condensation heat transfer reinforcement. The method specifically comprises the following steps: s1, preparing a carbon nano tube vertical array 2 on the silicon substrate 1; s2, drawing the carbon nano tube vertical array 2 to form a single-layer carbon nano tube film 3; s3, crosswise spreading the single-layer carbon nanotube film 3 on the substrate 4 to prepare a multi-layer carbon nanotube film net structure 5; and S4, carrying out water atomization, shrinkage, reinforcement and bonding on the multi-layer carbon nanotube film net structure 5. The surface of the three-dimensional carbon nanotube film network structure prepared by the invention has the advantages of stable chemical property, small additional thermal resistance and the like.
Description
Technical Field
The invention relates to a three-dimensional carbon nanotube film network structure for reinforcing water vapor condensation and a preparation method thereof, belonging to the technical field of water vapor condensation heat transfer reinforcement.
Background
The water vapor condensation is widely existed in each key link in industrial production and life. The water vapor condensation heat transfer is an important heat exchange mode in the fields of nuclear energy power, air conditioning refrigeration and the like. The strengthening of the condensation heat transfer of the water vapor is beneficial to improving the working efficiency of related equipment and saving the energy consumption and the cost of industrial production. At present, it has been confirmed that the water vapor drop-shaped condensing mode has a 5-7 times higher heat transfer coefficient than the water vapor film-shaped condensing mode. Therefore, a condensation surface capable of realizing a water vapor droplet condensation mode is a preferable condensation heat exchange surface.
In recent years, various technical solutions have been developed for processing and treating water vapor condensation surfaces and achieving different degrees of water vapor condensation heat transfer enhancement. These solutions can be mainly divided into two categories: firstly, the traditional metal surface is treated to form a low surface energy condensation coating. Secondly, designing and processing a super-hydrophobic condensation surface with a specific micro-nano structure. However, the above-mentioned condensation surfaces have the disadvantages of poor stability, complex processing technique, small supercooling range for enhancing heat transfer, etc., and most of the technical solutions can only process the condensation surfaces with smoothness or small curvature, which limits the practical application in industrial production.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the method for preparing the three-dimensional carbon nanotube film network structure for strengthening water vapor condensation overcomes the defects of the prior art, and specifically comprises the following steps: s1, preparing a carbon nano tube vertical array on the silicon substrate; s2, drawing the carbon nano tube vertical array to form a single-layer carbon nano tube film; s3, crosswise spreading the single-layer carbon nanotube film on the substrate to form a multi-layer carbon nanotube film net structure; and S4, carrying out water atomization, shrinkage, reinforcement and bonding on the multi-layer carbon nanotube film net structure.
The purpose of the invention is realized by the following technical scheme:
a method for preparing a carbon nanotube film network structure for strengthening water vapor condensation comprises the following steps:
s1, preparing a carbon nano tube vertical array on the silicon substrate;
s2, drawing the carbon nano tube vertical array to form a single-layer carbon nano tube film;
s3, crosswise spreading the single-layer carbon nanotube film on the substrate to form a multi-layer carbon nanotube film net structure;
and S4, carrying out water atomization, shrinkage, reinforcement and bonding on the multi-layer carbon nanotube film net structure.
Preferably, the number of spreading layers of the single-layer carbon nanotube film in the multi-layer carbon nanotube film net structure is 1-5.
Preferably, two adjacent single-layer carbon nanotube films in S3 are spread on the substrate by crossing at 90 degrees.
Preferably, the direction of the single-layer carbon nanotube film spread on the outermost layer in the multi-layer carbon nanotube film network structure is parallel to the gravity direction.
Preferably, the substrate is made of, but not limited to, copper or silver or stainless steel material.
Preferably, the carbon nanotube vertical array is prepared by a chemical vapor deposition method.
Preferably, the method for carrying out water atomization shrinkage reinforcement on the multi-layer carbon nanotube film net structure comprises the following steps:
s41, uniformly spraying trace atomized water on the surface of the multi-layer carbon nanotube film net structure until the multi-layer carbon nanotube film net structure is completely wetted;
s42, evaporating the water in the multi-layer carbon nanotube film net structure to dryness, so that the single carbon nanotubes are mutually attached, and the single-layer carbon nanotube film and the substrate are mutually attached.
Preferably, the atomized water is made using, but not limited to, a steam heater or an ultrasonic atomizer or nebulizer.
Preferably, the atomized water is deionized water.
Preferably, the method for evaporating moisture in S42 includes, but is not limited to, natural evaporation, and surface heating to promote moisture evaporation.
Compared with the prior art, the invention has the following beneficial effects: the invention develops the three-dimensional carbon nanotube film network structure surface based on water vapor condensation reinforcement by utilizing a simple and low-cost process, only a plurality of layers of oriented carbon nanotube films are covered on a substrate, and then water atomization is adopted for carrying out shrinkage treatment, thus the three-dimensional carbon nanotube film network structure surface based on water vapor condensation reinforcement can be prepared. The surface of the three-dimensional carbon nanotube film network structure prepared by the method has the advantages of stable chemical property, small additional thermal resistance and the like. The surface of the three-dimensional carbon nanotube film network structure can reduce the separation diameter of water vapor condensate droplets, improve the separation speed of the condensate droplets, obtain higher condensation heat transfer heat flux density and have better water vapor condensation strengthening effect.
Drawings
FIG. 1 illustrates a method for fabricating a vertical array and a thin film of carbon nanotubes;
FIG. 2 is a method for spreading a network structure of a multi-layered carbon nanotube film;
FIG. 3 is a schematic diagram of an atomization process for forming a network of carbon nanotubes;
FIG. 4 is a scanning electron microscope photograph of a three-dimensional carbon nanotube film network;
FIG. 5 is a diagram illustrating the condensation of water vapor on the three-dimensional carbon nanotube film network according to an embodiment of the present invention;
FIG. 6 shows the water vapor condensation on the surface of pure copper according to an embodiment of the present invention;
FIG. 7 is a comparison of the water vapor condensation enhancement efficiency in the embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
A three-dimensional carbon nanotube film network structure for reinforcing water vapor condensation and a preparation method thereof. The purpose of enhancing the condensation of water vapor is achieved by constructing a three-dimensional carbon nanotube film network structure 5 on the surface of the substrate 4. The carbon nanotube film net structure 5 material can cover various types of material substrates 4, and can play a role in strengthening the condensation heat transfer of water vapor after simple treatment. The preparation steps of the three-dimensional carbon nanotube film reticular structure 5 are as follows:
(1) preparing a single-layer carbon nanotube film 3;
(2) sequentially spreading a plurality of single-layer carbon nanotube films 3 on a substrate 4 to prepare a multi-layer carbon nanotube film network structure (5);
(3) the multi-layered carbon nanotube film network 5 is subjected to a shrink-fitting process using a minute amount of water vapor.
Wherein, the preparation raw material of the single-layer carbon nanotube film 3 is the carbon nanotube vertical array 2. And drawing the carbon nanotube vertical array 2 by using a set of electric platform to form a single-layer carbon nanotube film 3. The carbon nano tube vertical array 2 is prepared by adopting a chemical vapor deposition method, and the diameter of the prepared single carbon nano tube is 10-20 nm. The single-layer carbon nanotube film 3 is spread on the surface of the substrate 4, and the excess carbon nanotube film is cut along the edge of the substrate by high-energy laser, as shown in fig. 1. By repeating the spreading process of the single-walled carbon nanotube film 3, a plurality of single-walled carbon nanotube films 3 can be sequentially spread on the surface of the substrate 4, as shown in fig. 2.
All the single carbon nanotubes in the single-layer carbon nanotube film 3 obtained by the drawing method are arranged along the orientation, and the carbon nanotube films with different layers and different directions are spread on the substrate 4 to form the carbon nanotube film surfaces with different structures. When the spreading directions of the carbon nanotubes in two adjacent layers of carbon nanotube films are perpendicular to each other, the surface structure 5 of the obtained multi-layer carbon nanotube film is a three-dimensional network structure, as shown in fig. 2.
In the invention, the spreading layer number and the spreading direction of the surface of the multilayer carbon nanotube film are not limited, and the three-dimensional net structure surface formed by three layers of carbon nanotube films which are mutually vertically and crossly spread has the most obvious water vapor condensation strengthening effect. The multi-layer carbon nano-tube film is subjected to water atomization treatment by utilizing the water-shrinkage effect of the carbon nano-tube film, so that the multi-layer carbon nano-tube film is tightly attached to the surface of the substrate, the aim of strengthening the attaching force of the multi-layer carbon nano-tube film is fulfilled, and the surface of the multi-layer carbon nano-tube film net-shaped structure 5 is finally formed after water is completely evaporated. Preferably, the multilayer carbon nanotube film is sprayed by using an ultrasonic atomizer and naturally evaporated to dryness at room temperature.
The specific implementation case is as follows:
1. method for preparing three-dimensional carbon nanotube film net structure surface by using red copper flat plate as substrate
As shown in fig. 1, a carbon nanotube vertical array 2 is prepared on a silicon substrate 1 by a chemical vapor deposition method, and a single-layer carbon nanotube film 3 is formed by pulling the carbon nanotube vertical array 2 by an electric platform. And spreading the three-layer carbon nanotube film 3 on a red copper substrate of 2.5cm multiplied by 2.5 cm. Firstly, the single-layer carbon nanotube film 3 is covered on the red copper substrate, and then the redundant carbon nanotube film is cut along the edge of the red copper substrate by high-energy laser. And then, spreading the second layer of carbon nanotube film, wherein the spreading direction of the carbon nanotube film is vertical to that of the first layer of carbon nanotube film. And finally, spreading the third layer of carbon nanotube film in a direction perpendicular to the spreading direction of the second layer of carbon nanotube film and consistent with the spreading direction of the first layer of carbon nanotube film. Thereby completing the spreading process of the multi-layered carbon nanotube film network 5. The multi-layer carbon nanotube film network structure 5 is wetted by atomized water 7 generated by an ultrasonic atomizer 6 until the multi-layer carbon nanotube film network structure is fully wetted. After being placed under indoor drying conditions and naturally evaporated to dryness, the three-dimensional carbon nanotube network structure surface 8 can be prepared on the red copper substrate, as shown in fig. 3 and 4.
2. Three-dimensional carbon nanotube film network structure reinforced water vapor condensation performance test
The condensation performance of the untreated red copper surface and the surface of the three-dimensional carbon nanotube film network structure 8 with the red copper as the substrate in example 1 were respectively tested by a vertical surface water vapor condensation heat transfer testing device. The experimental test device consists of: the steam cavity, the square copper billet that has the thermocouple jack, polyvinyl chloride heat insulating block, steam generator, cooling water circulation system, temperature measurement system. The working principle of the device is that the steam generator heats steam and leads the steam into the steam chamber, and the temperature of the condensation surface is reduced by cooling water. The experiment was carried out at atmospheric pressure with a degree of supercooling of the condensation surface with the vapour of 25 ℃. + -. 3 ℃. As shown in fig. 5, the water vapor condensation on the surface of the three-dimensional carbon nanotube film network structure is obviously drop-shaped condensation, and the condensed liquid drops are small and dense. While the copper surface exhibits a large water film, the large amount of water "resides" on the surface showing poor condensation on the copper surface, as shown in fig. 6. FIG. 7 shows the result of comparing the condensation heat transfer efficiency of the surface of the three-dimensional carbon nanotube film network structure with that of the copper surface under the condition that the supercooling degree is 25 ℃. The surface condensation heat transfer efficiency of the three-dimensional carbon nanotube film network structure is remarkably improved by 36 percent.
According to the condensation performance test result, the surface of the three-dimensional carbon nanotube film network structure is provided with the honeycomb-shaped micro-nano structure, so that the distribution density of water vapor condensation liquid drops can be effectively increased, the merging and separation process of the condensation liquid drops is promoted, more water vapor is condensed continuously in time, and the condensation heat transfer process of the water vapor is strengthened.
Those skilled in the art will appreciate that those matters not described in detail in the present specification are well known in the art.
Although the present invention has been described with reference to the preferred embodiments, it is not intended to limit the present invention, and those skilled in the art can make variations and modifications of the present invention without departing from the spirit and scope of the present invention by using the methods and technical contents disclosed above.
Claims (10)
1. A method for preparing a carbon nanotube film network structure for strengthening water vapor condensation is characterized by comprising the following steps:
s1, preparing a carbon nano tube vertical array (2) on a silicon substrate (1);
s2, drawing the carbon nano tube vertical array (2) to form a single-layer carbon nano tube film (3);
s3, crosswise spreading the single-layer carbon nanotube film (3) on the substrate (4) to prepare a multi-layer carbon nanotube film net structure (5);
and S4, carrying out water atomization, shrinkage, reinforcement and bonding on the multi-layer carbon nanotube film net structure (5).
2. The method for preparing the carbon nanotube film network structure for enhancing water vapor condensation as claimed in claim 1, wherein the number of the spreading layers of the single-layer carbon nanotube film (3) in the multi-layer carbon nanotube film network structure (5) is 1-5.
3. The method for preparing the carbon nanotube film network structure for enhancing water vapor condensation as claimed in claim 1, wherein two adjacent single-walled carbon nanotube films (3) in S3 are spread on the substrate (4) at an angle of 90 ° across.
4. The method for preparing carbon nanotube film network structure for enhancing water vapor condensation as claimed in claim 1, wherein the direction of the single-layered carbon nanotube film (3) spread on the outermost layer of the multi-layered carbon nanotube film network structure (5) is parallel to the gravity direction.
5. The method for preparing carbon nanotube film network structure for enhancing water vapor condensation as claimed in claim 1, wherein the substrate (4) is made of copper or silver or stainless steel material.
6. The method for preparing carbon nanotube film network structure for enhancing water vapor condensation as claimed in claim 1, wherein the vertical array of carbon nanotubes (2) is prepared by chemical vapor deposition.
7. The method for preparing the carbon nanotube film network structure for enhancing water vapor condensation according to any one of claims 1 to 6, wherein the method for performing water atomization shrinkage reinforcement on the multi-layer carbon nanotube film network structure (5) comprises the following steps:
s41, uniformly spraying trace atomized water on the surface of the multi-layer carbon nanotube film net structure (5) until the multi-layer carbon nanotube film net structure is completely wetted;
s42, evaporating the water in the multi-layer carbon nanotube film net structure (5) to dryness, so that the single carbon nanotubes are mutually attached, and the single-layer carbon nanotube film (3) and the substrate (4) are mutually attached.
8. The method as claimed in claim 7, wherein the atomized water is produced by using but not limited to steam heater or ultrasonic atomizer or sprayer.
9. The method as claimed in claim 7, wherein the atomized water is deionized water.
10. The method as claimed in claim 7, wherein the step of evaporating water in S42 includes but is not limited to natural evaporation, surface heating to promote evaporation of water.
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Cited By (3)
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| CN112174115A (en) * | 2020-09-16 | 2021-01-05 | 华中科技大学 | Hierarchical carbon nanotube dry glue, preparation and application as adhesive |
| CN112857118A (en) * | 2021-01-08 | 2021-05-28 | 厦门大学 | Method and device for regulating and controlling hydrophilicity and hydrophobicity of surface of carbon nanotube array based on external electric field/plasma for enhancing phase change heat exchange |
| US20220397498A1 (en) * | 2021-06-09 | 2022-12-15 | Tsinghua University | Method for processing scanning electron microscope specimen |
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