Bio‐Inspired Superhydrophobic Closely Packed Aligned Nanoneedle Architectures for Enhancing Condensation Heat Transfer

Wang, Rui; Zhu, Jie; Meng, Kaixin; Wang, Hao; Deng, Tao; Gao, Xuefeng; Jiang, Lei

doi:10.1002/adfm.201800634

Cited by 71 publications

(79 citation statements)

References 37 publications

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“…Both the number and the distribution of combined droplets are important factors affecting the self-jumping speed [45,46] (Figure 3(c1-c3)). By adjusting the height, tip size and interspace of conical column structures (Figure 3(d1-d4)), Wang et al [47] obtained 320% enhancement on the condensation heat transfer coefficient compared with the smooth hydrophobic surface. [29], (a3) The sponge-like microfibrillar texture within the hair [29], (a4-a6) Hair deformation by water droplets [29]; (b1) The image of Cactus, (b2) SEM image of cactus spiny surface [32], (b3) The mechanism model of water droplet movement on cactus spiny surface [34], (b4) The image of superhydrophilic mastoids [38]; (c1) The image of Ruellia devosiana, (c2) The SEM image of Ruellia devosiana leaf [37], (c3) The image of the flat heat pipe with convex structure [39], (c4) Structure and working principle of the flat heat pipe with convex structure [39].…”

Section: Figure 2 (A1)mentioning

confidence: 99%

Nature-Inspired Structures Applied in Heat Transfer Enhancement and Drag Reduction

Zhu

Peng

et al. 2021

Micromachines

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Heat exchangers are general equipment for energy exchange in the industrial field. Enhancing the heat transfer of a heat exchanger with low pump energy consumption is beneficial to the maximum utilization of energy. The optimization design for enhanced heat transfer structure is an effective method to improve the heat transfer coefficient. Present research shows that the biomimetic structures applied in different equipment could enhance heat transfer and reduce flow resistance significantly. Firstly, six biomimetic structures including the fractal-tree-like structure, conical column structure, hybrid wetting structure, scale structure, concave-convex structure and superhydrophobic micro-nano structure were summarized in this paper. The biomimetic structure characteristics and heat transfer enhancement and drag reduction mechanisms were analyzed. Secondly, four processing methods including photolithography, nanoimprinting, femtosecond laser processing and 3D printing were introduced as the reference of biomimetic structure machining. Finally, according to the systemic summary of the research review, the prospect of biomimetic heat transfer structure optimization was proposed.

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Section: Figure 2 (A1)mentioning

confidence: 99%

Nature-Inspired Structures Applied in Heat Transfer Enhancement and Drag Reduction

Zhu

Peng

et al. 2021

Micromachines

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“…In previous studies, [ 48,57 ] continuous self‐jumping behaviors were neglected although they were conducive to the departure of condensate dewdrops. As Figure 4d and Movie S1, Supporting Information, show, the continuous self‐jumping behaviors occur three times in a 210‐ms period.…”

Section: Resultsmentioning

confidence: 99%

“…The self‐jumping behaviors can be also negatively affected. In contrast, nanoarray/nanopore structures are favorable to self‐jumping, [ 48,49 ] owing to the excellent resistance to moisture penetration and dewdrop adhesion. [ 50,51 ] However, for water‐based coatings, considering only the nanostructure (nanopores) is inadequate and the microstructure (micropores) could have a serious effect on the repellency to condensate microdrops.…”

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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“…Superhydrophobic surfaces that have a water contact angle (WCA) greater than 150° and contact angle hysteresis (CAH) less than 10° have shown great promises for potential applications, including self‐cleaning, anti‐(bio)fouling, anti‐corrosion, anti‐icing and anti‐frosting, drag reduction, and enhanced heat transfer. [ 1–6 ] The non‐wettability and large water droplet mobility are attributed to hydrophobic surface chemistry together with large surface asperity, where air can be trapped between textured grooves, thus, dramatically decreasing the fraction of liquid‐solid contact. [ 7 ] However, when the pressure applied to water is greater than the critical pressure at the gas‐liquid interface, transition from the Cassie‐Baxter non‐wetting state to the Wenzel wetting state occurs, where water is impregnated into the surface textures and will not be able to overcome the energy barrier to return to the non‐wetting state without external simulate.…”

Section: Introductionmentioning

confidence: 99%

Highly Robust, Pressure‐Resistant Superhydrophobic Coatings from Monolayer Assemblies of Chained Nanoparticles

Zhao

et al. 2020

Adv Materials Inter

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Despite significant progresses in development of superhydrohpobic coatings, their ability to resist small water droplets, which can exert large Laplace pressure on surface, remain limited. Here, a new strategy by self‐assembly of a monolayer of chained silica nanoparticles, forming an ultrathin film (<100 nm) with two‐tiered nanoasperity is presented. The resulting coating shows ultrahigh water repellency and high visible transparency. It can also repel low surface energy liquids, such as alcohol/water mixtures (surface tension ≥42 mN m−1). Importantly, the superhydrophobic coating demonstrates high resistance to impact pressure (at least 250 Pa) from water droplets dropped from 3.3 m height and internal Laplace pressure of 15 kPa from evaporated water droplets. Furthermore, the CNP coating remains to be superhydrophobic with condensed water droplets radius as small as 0.3 mm even after condensation for 6 h. In comparison, all of these properties are not possible from the assembly of spherical nanoparticles.

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Bio‐Inspired Superhydrophobic Closely Packed Aligned Nanoneedle Architectures for Enhancing Condensation Heat Transfer

Cited by 71 publications

References 37 publications

Nature-Inspired Structures Applied in Heat Transfer Enhancement and Drag Reduction

Nature-Inspired Structures Applied in Heat Transfer Enhancement and Drag Reduction

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

Highly Robust, Pressure‐Resistant Superhydrophobic Coatings from Monolayer Assemblies of Chained Nanoparticles

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