Self-Propelled Droplet Removal from Hydrophobic Fiber-Based Coalescers

Zhang, Kungang; Liu, Fangjie; Williams, Andrew; Qu, Xiaoyan; Feng, James J.; Chen, Chuan‐Hua

doi:10.1103/physrevlett.115.074502

Cited by 82 publications

(111 citation statements)

References 27 publications

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“…[1][2][3][4][5] Extensive research efforts have been devoted to promote dropwise condensation of water by employing various surface chemistries and micro-/nano-textures. [2][3][4][5][6][7][8][9][10] While recent studies have shown that droplet growth on millimetric convex surfaces by condensation is facilitated, [11][12][13] a more detailed study on droplet growth on textured surfaces is required to systematically understand the impact of the sign and the magnitude of the radius of curvature of surface features. Here, we provide a quantitative analysis of droplet growth dynamics on hydrophobic surfaces with a wide range of millimeter-scale surface topographies ranging from convex textures (e.g., bumps) to concave textures (e.g., dimples).…”

Section: Main Textmentioning

confidence: 99%

Dropwise condensation on hydrophobic bumps and dimples

Yao

Aizenberg

Park

2018

Applied Physics Letters

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Surface topography plays an important role in promoting or suppressing localized condensation. In this work, we study the growth of water droplets on hydrophobic convex surface textures such as bumps and concave surface textures such as dimples with a millimeter scale radius of curvature. We analyze the spatio-temporal droplet size distribution under a supersaturation condition created by keeping the uniform surface temperature below the dew point and show its relationship with the sign and magnitude of the surface curvature. In particular, in contrast to the well-known capillary condensation effect, we report an unexpectedly less favorable condensation on smaller, millimeter-scale dimples where the capillary condensation effect is negligible. To explain these experimental results, we numerically calculated the diffusion flux of water vapor around the surface textures, showing that its magnitude is higher on bumps and lower on dimples compared to a flat surface. We envision that our understanding of millimetric surface topography can be applied to improve the energy efficiency of condensation in applications such as water harvesting, heating, ventilation, and air conditioning systems for buildings and transportation, heat exchangers, thermal desalination plants, and fuel processing systems.

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Section: Main Textmentioning

confidence: 99%

Dropwise condensation on hydrophobic bumps and dimples

Yao

Aizenberg

Park

2018

Applied Physics Letters

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“…Second, the energetic model typically calculates the launching speed by assuming a perfect capillary-inertial energy conversion, an assumption that does not hold for a related phenomenon of coalescence-induced jumping drops. When pure liquid drops jump upon coalescence, the released surface energy is converted into translational kinetic energy with wide-ranging efficiencies, from 4% to 40% [19][20][21]. Third, the two-stage launching process outlined above is essentially a rigid-body model and cannot represent the true launching mechanism induced by liquid drop coalescence.…”

Section: Energetic Modelmentioning

confidence: 99%

Asymmetric drop coalescence launches fungal ballistospores with directionality

Liu

Chavez

Patek

et al. 2017

J. R. Soc. Interface.

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Thousands of fungal species use surface energy to power the launch of their ballistospores. The surface energy is released when a spherical Buller's drop at the spore's hilar appendix merges with a flattened drop on the adaxial side of the spore. The launching mechanism is primarily understood in terms of energetic models, and crucial features such as launching directionality are unexplained. Integrating experiments and simulations, we advance a mechanistic model based on the capillary-inertial coalescence between the Buller's drop and the adaxial drop, a pair that is asymmetric in size, shape and relative position. The asymmetric coalescence is surprisingly effective and robust, producing a launching momentum governed by the Buller's drop and a launching direction along the adaxial plane of the spore. These key functions of momentum generation and directional control are elucidated by numerical simulations, demonstrated on spore-mimicking particles, and corroborated by published ballistospore kinematics. Our work places the morphological and kinematic diversity of ballistospores into a general mechanical framework, and points to a generic catapulting mechanism of colloidal particles with implications for both biology and engineering.

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“…Inspired by nature, [ 4–7 ] superhydrophobic surfaces with extreme repellency to water have attracted significant interest, owing to their potential applications in anti‐condensation, anti‐frosting, anti‐icing, anti‐fogging, and self‐cleaning activities. [ 8–20 ] Biomimetic superhydrophobic surfaces can be prepared via different approaches, including reactive ion etching, [ 21 ] chemical/physical processing, [ 22–25 ] lithographing, [ 26,27 ] and coating. [ 28–33 ] Among these approaches, the coating approach has been widely applied, owing to its simple preparation process, low equipment requirement, and wide application range.…”

Section: Introductionmentioning

confidence: 99%

Water‐Based Robust Transparent Superamphiphobic Coatings for Resistance to Condensation, Frosting, Icing, and Fouling

Song

Cheng

et al. 2020

Adv Materials Inter

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high fraction of the total energy consumption. For example, air-conditioners and refrigerators account for more than 10% and 32% of the total residential energy consumption in China, respectively. [2,3] Therefore, improvement of the energy efficiency characterizing heat exchangers plays a crucial role in reducing energy consumption. However, the occurrence of condensate films, frost layers, and fouling on the surfaces of conventional hydrophilic heat exchangers acts as a thermal barrier to significantly reduce in the heat transfer. One alternative, that is, a periodic heating process for complete melting of the frost, results in extra energy consumption. In addition, wet surfaces are prone to the dust deposition, breeding of bacteria, and corrosion acceleration.Inspired by nature, [4][5][6][7] superhydrophobic surfaces with extreme repellency to water have attracted significant interest, owing to their potential applications in anticondensation, anti-frosting, anti-icing, antifogging, and self-cleaning activities. [8][9][10][11][12][13][14][15][16][17][18][19][20] Biomimetic superhydrophobic surfaces can be prepared via different approaches, including reactive ion etching, [21] chemical/physical processing, [22][23][24][25] lithographing, [26,27] and coating. [28][29][30][31][32][33] Among these approaches, the coating approach has been widely applied, owing to its simple preparation process, low equipment requirement, and wide application range. However, organic solvents, such as ethanol, acetone, or butyl acetate, are frequently used to dissolve or disperse low surface energy substances during the preparation process. [34,35] Compared with organic solvents, water is a green, safe, and economical solvent. [36] A few strategies have been reported about preparing waterbased superhydrophobic coatings and even water-based superamphiphobic coatings. [37][38][39][40][41][42][43][44] The focus of the present studies is on the preparation of these coatings. However, high performances of water-based superhydrophobic coatings are neglected which are the key factors in wide, long-term, and efficient application, due to the difficulty in achieving them. For example, micro-sized or smaller condensate dewdrops on most water-based superhydrophobic coatings occur in the Wenzel state, although the contact angles (CAs) and sliding angles (SAs) of macro water droplets on these coatings are >150 and <10, respectively. [45] The Wenzel-state dewdrops may lead to Due to the considerable demand for improving energy conservation and emission reduction, superhydrophobic coatings mainly derived from organic solvents have attracted significant interest, based on their potential role in enhancing heat transfer. Although water-based coatings are relatively safe and economical, and contain low volatile organic compounds (VOCs), the realization of coatings with excellent anti-condensation, anti-frosting, antiicing, and passive self-cleaning properties remains challenging, owing to the Wenzel state of small-sized condensate microdrops. Herein, ...

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Self-Propelled Droplet Removal from Hydrophobic Fiber-Based Coalescers

Cited by 82 publications

References 27 publications

Dropwise condensation on hydrophobic bumps and dimples

Dropwise condensation on hydrophobic bumps and dimples

Asymmetric drop coalescence launches fungal ballistospores with directionality

Water‐Based Robust Transparent Superamphiphobic Coatings for Resistance to Condensation, Frosting, Icing, and Fouling

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