CN111964503A - Three-dimensional patterned surface for enhancing dropwise condensation - Google Patents
Three-dimensional patterned surface for enhancing dropwise condensation Download PDFInfo
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Abstract
The invention provides a three-dimensional patterned surface for reinforcing dropwise condensation, which comprises a super-hydrophobic substrate and an upward convex super-hydrophilic three-dimensional pattern, wherein the upward convex super-hydrophilic three-dimensional pattern comprises a plurality of upward convex super-hydrophilic three-dimensional structures and a liquid drop collecting area, and the upward convex super-hydrophilic three-dimensional structures independently form array distribution or the end parts of the plurality of upward convex super-hydrophilic three-dimensional structures are connected to form cluster array distribution; the shape of the parallel surface section of the upper convex super-hydrophilic three-dimensional structure is wedge-shaped; the vertical surface cross-sectional shape of the convex-upper superhydrophilic three-dimensional structure includes, but is not limited to, a rectangle and an inverted cone. The invention can restrict the transverse growth space of the dropwise condensate, remarkably reduce the size of the dropwise condensate separated from the film area and promote the transmission and convergence of the condensate in the film area; the cluster-shaped combination of the three-dimensional patterns can reduce the integral separation resistance of surface condensate, improve the drop-shaped condensation efficiency and the long-acting property, and have important application values in the aspects of high-efficiency water collection, condensation heat transfer, manufacture of novel high-performance heat pipes and the like.
Description
The technical field is as follows:
the invention belongs to the technical field of condensation, heat transfer and mass transfer, and particularly relates to a three-dimensional patterned surface for enhancing dropwise condensation.
Background art:
condensation is a common phenomenon in nature and plays an important role in industrial production and life. The material has wide application in microelectronics (Nature Reviews Materials,2017,2(2): 16092), energy (National Science Review,2018,5(6): 878-. The condensation is divided into film-like condensation and drop-like condensation. Wherein the drop condensation Heat Transfer efficiency is several times of the film condensation [ Journal of Power and Energy,2002,21: 115-. Therefore, the primary goal of enhancing the droplet condensation process is to reduce the droplet condensate break-away size and to improve the droplet condensation longevity. These two goals are mainly achieved by three processes: (1) reducing the size of the drop-shaped condensate falling off to the film-shaped area; (2) promoting the collection of condensate separated to the film-shaped area; (3) the resultant detachment resistance of the film-like region condensate is reduced. At present, researchers at home and abroad mainly adopt a non-uniform wettability patterned surface of a desert beetle back structure to optimize the three processes [ Nature,2001,414: 33-34; ACS Nano,2015,9:71-81 ]. For example, Zhang et al processed a non-uniform wettability patterned surface having an array of square hydrophilic patterns by dopamine printing and polymerization on a superhydrophobic substrate, and the droplet condensate on the superhydrophobic substrate was continuously pumped to the hydrophilic pattern area, and the pumping action of this condensate could reduce the size of the droplet condensate escaping to the film area and accelerate the droplet area condensate renewal [ Journal of Materials Chemistry a.2015,3: 2844-. Pennly et al used a hydrophilic/hydrophobic stripe alternating patterned surface to reduce the droplet region condensate detachment size and reduce the film region condensate detachment resistance [ International Journal of Heat and Mass transfer.2015,83:27-38 ]. Ghosh, Hou and the like, which aim to improve the long-term effect of the drop-shaped area, and adopt a wedge-shaped hydrophilic pattern to strengthen the condensate converging capability of the membrane-shaped area [ Advanced Materials Interfaces,2020,7: 1901683; langmuir.2014,30:13103-13115 ]. However, the currently adopted non-uniform wettability patterned surface is of a two-dimensional structure, on the premise that the proportion of the surface droplet-shaped area and the film-shaped area is certain, the separation size of the condensate in the droplet-shaped area is difficult to further reduce through pattern design, and how to improve the long-term durability of droplet-shaped condensation by improving the gathering speed of the condensate in the film-shaped area and reducing the final separation resistance of the gathered condensate is also a key problem to be solved urgently while the separation size of the condensate in the droplet-shaped area is reduced. Based on the three-dimensional patterned surface for enhancing the dropwise condensation, the three processes of enhancing the dropwise condensation are optimized comprehensively, and the three-dimensional patterned surface has great potential application values in the aspects of efficient water collection, condensation heat transfer, novel high-performance heat pipe manufacturing and the like.
The invention content is as follows:
it is an object of the present invention to address the deficiencies of the prior art by providing a three-dimensional patterned surface that enhances droplet condensation.
The invention adopts the following technical scheme:
a three-dimensional patterned surface for intensifying dropwise condensation comprises a super-hydrophobic substrate and an upper convex super-hydrophilic three-dimensional pattern arranged on the super-hydrophobic substrate, wherein the upper convex super-hydrophilic three-dimensional pattern comprises a plurality of upper convex super-hydrophilic three-dimensional structures and a liquid drop gathering area, and each upper convex super-hydrophilic three-dimensional structure independently forms an array or the end parts of the plurality of upper convex super-hydrophilic three-dimensional structures are connected to form a cluster array; and the steam forms condensed liquid drops on the surface of the super-hydrophobic substrate, the condensed liquid drops gradually become larger until the condensed liquid drops contact with the side wall of the upper convex super-hydrophilic three-dimensional structure, are sucked into the surface of the upper convex super-hydrophilic three-dimensional structure under the action of capillary force, and are converged to a liquid drop collecting area and separated from the liquid drop collecting area.
Furthermore, the vertical height of the upper convex-shaped super-hydrophilic three-dimensional structure on the super-hydrophobic substrate is 10-5000 microns.
Further, the upper convex-shaped super-hydrophilic three-dimensional structures independently form an array or the end parts of a plurality of upper convex-shaped super-hydrophilic three-dimensional structures are connected to form a cluster array, and when the cluster array is formed, the included angle between adjacent upper convex-shaped super-hydrophilic three-dimensional structures in each cluster is 1-180 degrees.
Furthermore, the shape of the parallel surface section of the upper convex super-hydrophilic three-dimensional structure is wedge-shaped, and the opening angle of the wedge-shaped is 0.1-10 degrees.
Further, the vertical surface cross-sectional shape of the upper convex-shaped super-hydrophilic three-dimensional structure includes, but is not limited to, a rectangle and an inverted cone.
Furthermore, the vertical surface section of the upper convex-shaped super-hydrophilic three-dimensional structure is rectangular, and the height-width ratio is 0.1-50.
Further, the vertical surface section of the upper convex super-hydrophilic three-dimensional structure is in an inverted cone shape, and the opening angle of the inverted cone shape is 0.1-150 degrees.
The invention has the beneficial effects that:
(1) the invention provides an upper convex super-hydrophilic three-dimensional pattern designed on a super-hydrophobic substrate, which can restrict the transverse growth space of the super-hydrophobic substrate drop-shaped condensate, remarkably reduce the size of the super-hydrophobic substrate (drop-shaped area) condensate separated from the upper convex super-hydrophilic three-dimensional pattern (film-shaped area) on the premise of not changing the proportion of the drop-shaped area, improve the update frequency of the condensate in the drop-shaped area, and further improve the condensation efficiency;
(2) when the vertical surface section of the upper convex super-hydrophilic three-dimensional structure is in an inverted cone shape, the size of the drop-shaped condensate which is separated from a membrane area in the condensation process can be further reduced, wherein the larger the opening angle of the inverted cone is, the smaller the separation size of the drop-shaped condensate is;
(3) the section shape of the parallel surface of the upper convex super-hydrophilic three-dimensional structure adopted by the invention is wedge-shaped, the opening angle of the wedge is in the range of 0.1-10 degrees, the design can generate Laplace pressure gradient, and condensate in a film area is driven to be rapidly gathered;
(4) according to the invention, a plurality of upper convex-shaped super-hydrophilic three-dimensional structures independently form an array or the ends of a plurality of upper convex-shaped super-hydrophilic three-dimensional structures are connected to form a cluster array, so that the perimeter of the boundary of a film area can be increased, the transfer efficiency of condensate in a drop area to the film area is improved, and the integral surface separation resistance is reduced and the final separation of the condensate on the surface is promoted on the premise of the same drop film condensation ratio; the invention has reasonable design, simple structure and strong practicability, and has important application value in the aspects of high-efficiency water collection, condensation heat transfer, manufacture of novel high-performance heat pipes and the like.
Description of the drawings:
FIG. 1 is a schematic diagram of a three-dimensional patterned surface for enhanced droplet condensation in accordance with the present invention;
FIG. 2 is a schematic diagram of the detachment of droplets from a droplet region to a film region in a three-dimensional patterned surface of the present invention to enhance droplet condensation;
FIG. 3 is a schematic view of the upper convex superhydrophilic three-dimensional structure of the present invention;
FIG. 4 is a schematic diagram showing the influence of the height of the vertical surface of the upper convex super-hydrophilic three-dimensional structure on the size of the condensate separated from the drop-shaped area to the film-shaped area;
FIG. 5 is a schematic diagram showing the influence rule of the inverted cone angle on the size of the film-like region from which the condensate in the drop-like region breaks away when the cross-sectional shape of the vertical surface of the upper convex super-hydrophilic three-dimensional structure is inverted cone according to the present invention;
FIG. 6 is a schematic diagram showing the influence of the wedge opening angle on the driving force for liquid drop convergence when the cross-sectional shape of the parallel surface of the convex super-hydrophilic three-dimensional structure is wedge-shaped;
FIG. 7 is a schematic diagram illustrating condensate detachment resistance after convergence when a plurality of convex-shaped super-hydrophilic three-dimensional structures are combined in a cluster shape in the cross-sectional shape of a parallel surface according to the present invention;
FIG. 8 is a schematic diagram illustrating the effect of increasing the size of the convex superhydrophilic three-dimensional structure on the condensation velocity of the surface of the condensed liquid droplets according to the present invention;
the labels in the figures are: 1. a superhydrophobic substrate; 2. a convex super-hydrophilic three-dimensional pattern; 3. a convex super-hydrophilic three-dimensional structure; 4. a droplet collection zone; 5. a vertical surface cross-section; 6. a parallel surface cross section; 7. dropwise condensing liquid on the super-hydrophobic substrate; 8. the dropwise condensate liquid is in contact with the side wall of the upper convex-shaped super-hydrophilic three-dimensional structure on the super-hydrophobic substrate; 9. condensate transported in the upper convex super-hydrophilic three-dimensional pattern; 10. the condensate liquid is converged in the liquid drop convergence area; 11. the dropwise condensate liquid is sucked away by the side wall of the upper convex super-hydrophilic three-dimensional structure; 12. uncondensed water vapor; 13. a film-shaped condensation area on the surface of the upper convex super-hydrophilic three-dimensional structure.
The specific implementation mode is as follows:
in order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
Example 1
Referring to fig. 1-3, an embodiment of the present invention provides a three-dimensional patterned surface for enhancing dropwise condensation, including a superhydrophobic substrate 1 and an upper convex superhydrophilic three-dimensional pattern 2 disposed on the superhydrophobic substrate 1, where the upper convex superhydrophilic three-dimensional pattern 2 includes 7 upper convex superhydrophilic three-dimensional structures 3 and a droplet collection area 4, the upper convex superhydrophilic three-dimensional structures 3 are connected in sequence, and the droplet collection area 4 is located below the upper convex superhydrophilic three-dimensional structures 3; the vertical distance between the upper convex super-hydrophilic three-dimensional structure 3 and the super-hydrophobic substrate 1 is 500 micrometers, so that the size of a condensate liquid in a drop-shaped area separated to a membrane-shaped area is reduced, and the condensation efficiency is improved; the upper convex-shaped super-hydrophilic three-dimensional structures 3 are sequentially connected, 7 upper convex-shaped super-hydrophilic three-dimensional structures 3 form cluster combination, the integral separation resistance of surface condensate can be reduced on the premise of not changing the proportion of a drop-shaped area, the final separation of the surface condensate is promoted, and the included angle between every two adjacent upper convex-shaped super-hydrophilic three-dimensional structures 3 is 20 degrees; the parallel surface section 6 of the upper convex-shaped super-hydrophilic three-dimensional structure 3 is wedge-shaped, the opening angle of the wedge is 5 degrees, and condensate separated from the drop-shaped area can be rapidly converged to the end part of the wedge under the action of Laplace pressure gradient; the vertical surface section 5 of the upper convex super-hydrophilic three-dimensional structure 3 is in an inverted cone shape, the opening angle of the inverted cone shape is 30 degrees, and the size of the drop-shaped condensate separated from the film-shaped area in the condensation process can be further reduced.
Example 2
The embodiment of the invention provides a three-dimensional patterned surface for intensifying dropwise condensation, which comprises a super-hydrophobic substrate 1 and an upper convex super-hydrophilic three-dimensional pattern 2 arranged on the super-hydrophobic substrate 1, wherein the upper convex super-hydrophilic three-dimensional pattern 2 comprises 9 upper convex super-hydrophilic three-dimensional structures 3 and a liquid drop collecting area 4, the upper convex super-hydrophilic three-dimensional structures 3 are sequentially connected to form a cluster combination, and the liquid drop collecting area 4 is positioned below the cluster combination; the vertical distance between the upper convex-shaped super-hydrophilic three-dimensional structure 3 and the super-hydrophobic substrate 1 is 800 mu m; the upper convex-shaped super-hydrophilic three-dimensional structures 3 are sequentially connected, 9 upper convex-shaped super-hydrophilic three-dimensional structures 3 form 3 cluster combinations, and the included angle between every two adjacent upper convex-shaped super-hydrophilic three-dimensional structures 3 is 15 degrees; the parallel surface section 6 of the upper convex-shaped super-hydrophilic three-dimensional structure 3 is wedge-shaped, and the opening angle of the wedge is 7 degrees; the vertical surface section 5 of the upper convex-shaped super-hydrophilic three-dimensional structure 3 is rectangular, and the height-to-width ratio is 10.
Example 3
The embodiment of the invention provides a three-dimensional patterned surface for reinforcing dropwise condensation, which comprises a super-hydrophobic substrate 1 and an upper convex super-hydrophilic three-dimensional pattern 2 arranged on the super-hydrophobic substrate 1, wherein the upper convex super-hydrophilic three-dimensional pattern 2 comprises 9 upper convex super-hydrophilic three-dimensional structures 3 and a liquid drop collecting area 4, the upper convex super-hydrophilic three-dimensional structures 3 are sequentially connected, and the liquid drop collecting area 4 is positioned below the upper convex super-hydrophilic three-dimensional structures 3; the vertical distance between the upper convex-shaped super-hydrophilic three-dimensional structure 3 and the super-hydrophobic substrate 1 is 1000 mu m; the upper convex-shaped super-hydrophilic three-dimensional structures 3 are sequentially connected, a plurality of upper convex-shaped super-hydrophilic three-dimensional structures 3 form a cluster combination, and the included angle between every two adjacent upper convex-shaped super-hydrophilic three-dimensional structures 3 is 30 degrees; the parallel surface section 6 of the upper convex-shaped super-hydrophilic three-dimensional structure 3 is wedge-shaped, and the opening angle of the wedge is 10 degrees; the vertical surface section 5 of the upper convex-shaped super-hydrophilic three-dimensional structure 3 is in an inverted cone shape, and the opening angle of the inverted cone shape is 40 degrees.
Example 4
The embodiment of the invention provides a three-dimensional patterned surface for reinforcing dropwise condensation, which comprises a super-hydrophobic substrate 1 and an upper convex super-hydrophilic three-dimensional pattern 2 arranged on the super-hydrophobic substrate 1, wherein the upper convex super-hydrophilic three-dimensional pattern 2 comprises a plurality of upper convex super-hydrophilic three-dimensional structures 3 and a liquid drop collecting area 4, and the liquid drop collecting area 4 is positioned below the upper convex super-hydrophilic three-dimensional structures 3; the upper convex super-hydrophilic three-dimensional structure forms array distribution; the vertical distance between the upper convex-shaped super-hydrophilic three-dimensional structure 3 and the super-hydrophobic substrate 1 is 2000 mu m, and the size of the upper convex-shaped super-hydrophilic three-dimensional structure 3 is enlarged to increase the size of the condensate 10 converged in the liquid drop converging area, so that the saturated vapor pressure of the surface of the condensate 10 converged in the liquid drop converging area is reduced, and the condensation efficiency is improved; the parallel surface section 6 of the upper convex-shaped super-hydrophilic three-dimensional structure 3 is wedge-shaped, and the opening angle of the wedge is 4 degrees; the cross section 5 of the vertical surface of the hydrophilic three-dimensional structure 3 is in the shape of an inverted cone, and the opening angle of the inverted cone is 60 degrees.
The application process of the invention is as follows: the steam forms condensed liquid drops on the super-hydrophobic substrate 1, the condensed liquid drops gradually become larger until contacting the side wall of the upper convex-shaped super-hydrophilic three-dimensional structure 3, the condensed liquid drops are sucked into the surface of the upper convex-shaped super-hydrophilic three-dimensional structure 3 under the action of capillary force, the drop-shaped area is separated from the membrane-shaped area, and finally the condensed liquid drops are converged to the liquid drop collecting area 4 and separated.
The design principle of the invention is as follows: the convex super-hydrophilic three-dimensional pattern provided by the invention simultaneously optimizes four factors influencing the condensation efficiency: (1) the transverse growth space of the dropwise condensate is restrained, so that the size of the dropwise condensate separated from the film-shaped area is greatly reduced; (2) the cross section of the parallel surface of the upper convex super-hydrophilic three-dimensional structure is in a wedge shape, so that the transmission and the convergence of condensate separated to the membrane area can be promoted; (3) the plurality of upper convex-shaped super-hydrophilic three-dimensional structures independently form an array or the ends of the plurality of upper convex-shaped super-hydrophilic three-dimensional structures are connected to form a cluster array, so that the perimeter of the boundary of the membrane area can be increased, the separation efficiency of condensate in the membrane area to the drop area is improved, and the integral separation resistance of the condensate on the surface is reduced; (4) the size of the upper convex super-hydrophilic three-dimensional structure is increased, so that the curvature of the converged liquid drops can be reduced, and the saturated vapor pressure of the surface of the condensate liquid converged in the liquid drop converging area is further reduced. The design principle of the present invention is further explained according to the four aspects as follows:
firstly, the lateral growth space of the dropwise condensate is restrained, so that the size of the dropwise condensate separated to the film-shaped area is greatly reduced
Referring to fig. 4, a convex superhydrophilic three-dimensional pattern (a film-shaped region) is designed on a superhydrophobic substrate (a drop-shaped region), the vertical surface height of the convex superhydrophilic three-dimensional pattern is increased to restrict the lateral growth space of condensate in the drop-shaped region, and the size of the condensate in the drop-shaped region separating from the film-shaped region is reduced, and the specific principle is as follows:
designing three upper convex super-hydrophilic three-dimensional patterns with different heights, wherein the heights are respectively H0、H1、H2In which H is0＝0，H2＞H1Is greater than 0. When H is present0When the liquid drop is 0, the top of the super-hydrophilic three-dimensional pattern is flush with the super-hydrophobic substrate, the drop-shaped condensate on the super-hydrophobic substrate nucleates and grows up in the steam condensation process, and only when the solid-liquid-gas three-phase line at the bottom of the liquid drop is expanded to the boundary of the super-hydrophilic three-dimensional pattern, the drop-shaped condensate can be absorbed by the super-hydrophilic three-dimensional pattern so as to be separated from the film-shaped area, and the separation radius of the corresponding drop-shaped condensate is R0The condensate disengagement size is larger; when the height of the vertical surface of the convex-shaped super-hydrophilic three-dimensional pattern is increased to 50 μm, the height is H1＝50μm(H1Greater than 0), during the condensation process, the drop-shaped condensate on the super-hydrophobic substrate gradually grows up, at the moment, a gas-liquid interface at the side edge of the liquid drop contacts the upper convex super-hydrophilic three-dimensional pattern before a solid-liquid-gas three-phase line at the bottom of the liquid drop, then the condensed liquid is sucked away by the super-hydrophilic three-dimensional pattern in advance and is separated to a film-shaped area, at the moment, the separation radius of the corresponding drop-shaped condensate is R1Apparently, R1＜R0The drop break-off size at this time is smaller; continuously increasing the surface height H of the convex super-hydrophilic three-dimensional pattern2To 1000 μm, (H)2＝1000μm＞H1> 0), it is seen that the droplet condensate breaks off to a further reduced size of the film-like region, i.e. R2＜R1＜R0. Therefore, the height of the vertical surface of the convex super-hydrophilic three-dimensional pattern is increased, and the size of condensate in a drop-shaped area which is separated from a film-shaped area can be obviously reduced.
The surface of the super-hydrophobic substrate is designed with an upward convex super-hydrophilic three-dimensional pattern with a reverse conical vertical surface section, so that the separation size of the steam in the drop condensation process is further reduced, and the specific principle is as follows:
referring to fig. 5, when the cross-sectional shape of the vertical surface of the upper convex-shaped superhydrophilic three-dimensional pattern is rectangular, once the side end of the droplet contacts the side wall of the upper convex-shaped superhydrophilic three-dimensional pattern, the height of the upper convex-shaped superhydrophilic three-dimensional pattern is continuously increased, and the drop condensate detachment size (taper angle θ) cannot be further reduced00 degree is adopted; if the cross-sectional shape is designed to be an inverted cone, and the cone angle theta1At 20 deg., as can be seen from fig. 4, the droplets on the superhydrophobic substrate can beContacting the hydrophilic three-dimensional structure at a smaller size, thereby further reducing the size of the drop-like region where condensate breaks off to the membrane-like region; continuously increasing the opening angle theta of the reverse taper shape2At 60 deg., it can be seen from fig. 5 that the size of the region where the droplets of condensate break off into films is reduced again. Therefore, when the upper convex super-hydrophilic three-dimensional pattern with the inverted cone-shaped section is adopted, the opening angle of the inverted cone is increased, and the size of condensate in the drop-shaped area separating from the film-shaped area is reduced.
Secondly, the transmission and the convergence of condensate separated to a membrane area can be promoted by the design that the section shape of the parallel surface of the upper convex super-hydrophilic three-dimensional structure is wedge-shaped, and the specific principle is as follows:
referring to fig. 6, when the cross-sectional shape of the parallel surface of the upper convex-shaped super-hydrophilic three-dimensional structure is the parallel line stripe, the laplace pressure difference between the upper and lower ends is equal, that is, P, after the drop-shaped condensate is separated to the super-hydrophilic three-dimensional pattern1-P2When the liquid drops are 0, the liquid drops can only diffuse to the end part of the super-hydrophilic three-dimensional pattern under the action of capillary force and gravity; when the section shape of the parallel surface of the upper convex-shaped super-hydrophilic three-dimensional structure is designed to be wedge-shaped, the opening angle of the wedge is alpha (alpha is 2 degrees), and after the liquid drops enter the super-hydrophilic three-dimensional pattern, the Laplace pressure difference (P) between the upper end and the lower end is generatedα1-Pα2>0) Is driven to move to the end of the hydrophilic three-dimensional structure; the wedge opening angle is increased to be beta (beta is 4 degrees, beta)>α>0 degree, the Laplace pressure difference between the upper and lower ends increases (P) after the liquid drops enter the hydrophilic three-dimensional structureβ1-Pβ2>Pα1-Pα2>0) The pressure difference driving the droplets to converge towards the end of the hydrophilic three-dimensional structure is greater. Therefore, the design that the cross section of the parallel surface of the upper convex super-hydrophilic three-dimensional structure is in the shape of a wedge can promote the transmission and the convergence of condensate which is separated to the film area, the opening angle of the wedge is increased, and the transmission speed of liquid drops in the hydrophilic pattern can be improved.
And thirdly, a plurality of upper convex-shaped super-hydrophilic three-dimensional structures are sequentially connected to form a cluster wedge-shaped combination, so that the separation resistance of liquid drops after the liquid drops are gathered in the super-hydrophilic three-dimensional patterns can be reduced, and the specific principle is as follows:
referring to fig. 7, during the condensation of the steam,when a gas-liquid interface at the side end of the dropwise condensate liquid on the super-hydrophobic substrate (a dropwise region) contacts with the side wall of the hydrophilic three-dimensional structure, the dropwise condensate liquid is absorbed into the upper convex cluster wedge-shaped super-hydrophilic three-dimensional pattern (a film-shaped region) under the action of capillary force, and then is converged towards the end of the cluster wedge-shaped super-hydrophilic three-dimensional pattern under the Laplace pressure difference generated by the wedge-shaped structure and flows to the liquid drop converging region. Under the condition that the height of the cluster wedge-shaped super-hydrophilic three-dimensional pattern and the opening angle of a single wedge are not changed, the amount of condensate in the drop-shaped area separated to the film-shaped area in unit time is positively correlated with the perimeter of the pattern, however, the adhesion force of the liquid drop on the end part of the super-hydrophilic three-dimensional pattern is positively correlated with the width of the end part, and the adhesion force of the liquid drop on the end part is not changed when the width of the end part is not changed. Thus, if C is used1、C2···CNRespectively representing the perimeter of the convex-shaped cluster wedge-shaped super-hydrophilic three-dimensional pattern consisting of 1, 2 and 3 wedges and using F1、F2、F3···FNRespectively, represent the maximum adhesion of the drop off the surface, then
It can represent the release resistance per unit perimeter length of the droplets in the convex cluster wedge-shaped super-hydrophilic three-dimensional pattern consisting of 1, 2, N wedges. Within a certain range are:
that is, within a certain range, the disengagement resistance will gradually decrease to a minimum value as the number of wedges increases. Therefore, the adoption of the wedge-shaped super-hydrophilic three-dimensional pattern of the convex clusters is beneficial to reducing the final separation resistance of the surface condensate.
And fourthly, increasing the size of the upper convex super-hydrophilic three-dimensional structure can reduce the curvature of the converged liquid drops so as to reduce the saturated vapor pressure of the surface of the condensate liquid converged in the liquid drop converging region. The specific principle is as follows:
referring to fig. 8, during the condensation process of the steam, the convex-shaped super-hydrophilic three-dimensional pattern not only increases the mass of the condensate collected in the liquid drop collecting area by sucking the liquid drops in the hydrophobic area, but also allows the steam to pass through the super-hydrophilic three-dimensional patternThe manner in which the hydrophilic surface directly condenses increases the mass of condensate that collects in the droplet collection area. However, the saturated vapor pressure at the surface of the condensate during condensation is inversely related to the size of the condensate droplets, i.e.: the smaller the curvature of the condensed droplets, the lower the saturated vapor pressure at the surface of the condensed droplets, and the more likely the vapor will condense. Increasing the size of the convex super-hydrophilic three-dimensional structure to be L3(L3＞L2＞L1) The size of the condensate droplets that eventually converge at the end of the convex-above hydrophilic three-dimensional structure will also increase (D)3＞D2＞D1) The curvature is reduced, thereby reducing the saturated vapor pressure (P) of the surface of the condensed droplets after collectionr3＜Pr2＜Pr1) The condensing speed of the steam on the surface of the condensed liquid drops after the steam is converged is improved. Therefore, the size of the convex hydrophilic three-dimensional structure is increased, the saturated vapor pressure on the surface of the condensed liquid drops after gathering is reduced, and the steam condensation efficiency is improved.
The three-dimensional patterning surface for reinforcing the dropwise condensation has the upper convex super-hydrophilic three-dimensional pattern, the three-dimensional pattern can restrict the transverse growth space of the dropwise condensate, and the size of the dropwise condensate separated from the film area is greatly reduced on the premise of not changing the proportion of the dropwise area; the transmission and the convergence of the film-shaped region condensate can be promoted, and in addition, the integral separation resistance of the surface condensate can be reduced by the cluster-shaped combination of the three-dimensional patterns, so that the final separation of the surface condensate is promoted, and the dropwise condensation efficiency and the long-acting property are improved. The three-dimensional patterned surface provided by the invention optimizes four processes of strengthened drop-shaped condensation, and has great potential application value in the aspects of efficient water collection, condensation heat transfer, novel high-performance heat pipe manufacturing and the like.
The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention, it should be noted that, for those skilled in the art, several modifications and decorations without departing from the principle of the present invention should be regarded as the protection scope of the present invention.
Claims (7)
1. The three-dimensional patterned surface for intensifying dropwise condensation is characterized by comprising a super-hydrophobic substrate (1) and a convex-upper super-hydrophilic three-dimensional pattern (2) arranged on the super-hydrophobic substrate (1), wherein the convex-upper super-hydrophilic three-dimensional pattern (2) comprises a plurality of convex-upper super-hydrophilic three-dimensional structures (3) and a liquid drop gathering area (4), and each convex-upper super-hydrophilic three-dimensional structure (3) independently forms an array or the end parts of the plurality of convex-upper super-hydrophilic three-dimensional structures (3) are connected to form a cluster array; the steam forms condensed liquid drops on the surface of the super-hydrophobic substrate (1), the condensed liquid drops gradually grow until contacting the side wall of the upper convex-shaped super-hydrophilic three-dimensional structure (3), are sucked into the surface of the upper convex-shaped super-hydrophilic three-dimensional structure (3) under the action of capillary force, and are converged to the liquid drop collecting area (4) and separated.
2. Three-dimensional patterned surface with enhanced droplet condensation according to claim 1, wherein the vertical height of the convex-shaped superhydrophobic three-dimensional structures (3) on the superhydrophobic substrate (1) is 10-5000 μ ι η.
3. The three-dimensional patterned surface for enhancing dropwise condensation according to claim 1, wherein the upper convex-shaped super-hydrophilic three-dimensional structures (3) are independently formed into an array or a plurality of upper convex-shaped super-hydrophilic three-dimensional structures (3) are connected at their ends to form an array of clusters, and the included angle between adjacent upper convex-shaped super-hydrophilic three-dimensional structures (3) in each cluster is 1-180 degrees when forming the array of clusters.
4. Three-dimensional patterned surface for enhanced droplet condensation according to claim 1, wherein the parallel surface cross-section (6) of the convex-upper superhydrophilic three-dimensional structure (3) has a wedge shape with an opening angle of 0.1-10 °.
5. Three-dimensional patterned surface for enhanced droplet condensation according to claim 1, wherein the vertical surface cross-sectional (5) shape of the upper convex superhydrophilic three-dimensional structure (3) includes but is not limited to rectangular and inverted conical.
6. Three-dimensional patterned surface for enhanced droplet condensation according to claim 5, wherein the vertical surface cross-section (5) of the upwardly convex superhydrophilic three-dimensional structure (3) is rectangular in shape with an aspect ratio of 0.1-50.
7. The three-dimensional patterned surface for enhanced dropwise condensation according to claim 5, wherein the vertical surface cross-section (5) of the upper convex-shaped superhydrophilic three-dimensional structure (3) is in the shape of an inverted cone with an opening angle of 0.1-150 °.
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