Wetting transition of sessile and condensate droplets on copper-based superhydrophobic surfaces

Zhao, Yugang; Zhang, Hui; Wang, Wei; Yang, Chun

doi:10.1016/j.ijheatmasstransfer.2018.07.153

Cited by 17 publications

(10 citation statements)

References 57 publications

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“…However, icing in many industries is unwanted, leading to detrimental and occasionally catastrophic consequences [5,6]. In HVAC&R (heating, ventilating, air conditioning and refrigerating) systems, heat exchangers that operate in supercooled and humid environments are inevitably covered with a thick layer of frost, yielding a non-negligible thermal resistance [7][8][9]. Therefore, both the system integrity and the coefficient of performance are affected drastically.…”

Section: Introductionmentioning

confidence: 99%

Ice Coverage Induced by Depositing a Water Drop onto the Supercooled Substrate at Extreme Low Vapor Pressure

et al. 2021

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Icing/snowing/frosting is ubiquitous in nature and industrial processes, and the accretion of ice mostly leads to catastrophic consequences. The existing understanding of icing is still limited, particularly for aircraft icing, where direct observation of the freezing dynamics is inaccessible. In this work, we investigate experimentally the impact and freezing of a water drop onto the supercooled substrate at extremely low vapor pressure, to mimic an aircraft passing through clouds at a relatively high altitude, engendering icing upon collisions with pendant drops. Special attention is focused on the ice coverage induced by an impinging drop, from the perimeter pointing outward along the radial direction. We observed two freezing regimes: (I) spread-recoil-freeze at the substrate temperature of Ts = −15.4 ± 0.2 °C and (II) spread (incomplete)-freeze at the substrate temperature of Ts = −22.1 ± 0.2 °C. The ice coverage is approximately one order of magnitude larger than the frozen drop itself, and counterintuitively, larger supercooling yields smaller ice coverage in the range of interest. We attribute the variation of ice coverage to the kinetics of vapor diffusion in the two regimes. This fundamental understanding benefits the design of new anti-icing technologies for aircraft.

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Section: Introductionmentioning

confidence: 99%

Ice Coverage Induced by Depositing a Water Drop onto the Supercooled Substrate at Extreme Low Vapor Pressure

et al. 2021

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“…For the two different fabric substrates, the WCA of the fine fabric before immersing is 0°, but the WCA of the coarse fabric is 114°, which is maybe due to the surface of the fine fabric has regular small holes (Figure S2), and water droplets can penetrate quickly 68 . However, the surface of the coarse fabric has more asperities, 69 which form air pocket with water droplets, resulting in a certain degree of hydrophobicity before the stearic acid treatment (WCA = 114°) 70 . More interestingly, the stearic acid‐modified fine fabric is superhydrophobic with a WCA of 156°, while the WCA increment of stearic acid‐modified coarse fabric is only 32° (WCA = 146°), which can be attributed to stearic acid with low surface energy 71 .…”

Section: Resultsmentioning

confidence: 95%

“…In contrast, the fabric and wood chips still maintained super‐hydrophobicity at 200°C partly attributed to the numerous asperities one the fabrics and wood chips surface (Figure S2). 69 Additionally, the melting point of stearic acid is 56 to 69°C, and the boiling point is 232°C (2.0 KPa). Therefore, the stearic acid exists as a liquid on the surface of different substrates when the modified substrate is dried at 200°C 74 .…”

Section: Resultsmentioning

confidence: 99%

Fabrication of the superhydrophobic natural cellulosic paper with different wettability and oil/water separation application

Yun

Tong

Wang

et al. 2020

J of Applied Polymer Sci

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Renewable superhydrophobic materials have attracted great attention due to their extensive applications in the fields such as cost‐effective and biodegradable oil/water separation field. Herein, we reported an eco‐friendly and facile methodology to develop the superhydrophobic cellulosic paper by immersion method using the ethanol solution of stearic acid. Furthermore, the treated cellulosic papers showed super‐hydrophobicity with water contact angle (WCA) above 153°. Interestingly, this method can realize superhydrophobic‐hydrophilic conversion by simply adjusting the temperature and is amenable for different substrates and with the WCA of 114‐162°. More importantly, the utilization of fluorinated reagents has been avoided, thereby minimizing the production cost and improving safety and environmental aspects. Meanwhile, the modified natural cellulosic paper is applied for oil–water separation, and its separation efficiency was as high as 95% after 10 cycles, indicating the good reusability of stearic acid modified filter papers. Consequently, this simple strategy based on the stearic acid immersion method thus provided an easy conversion of superhydrophobic‐hydrophilic interface and provided facile strategies for conversion of commercial quantitative filter paper to functional materials for oil/water separation.

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“…observed the wetting and condensation phenomena on a copper‐based superhydrophobic surface. [ 52 ] In this case, CuCl 2 solution of 100 × 10 −3 m was used as an electrolyte to create nanoasperities on the substrate via electrochemical deposition. Subsequently, a self‐assembled monolayer of fluorinated silane was deposited onto the plate surface to promote hydrophobicity ( Figure ).…”

Section: Superhydrophobic Surfacesmentioning

confidence: 99%

Implementing Superhydrophobic Surfaces within Various Condensation Environments: A Review

Singh

Zhang

Stafford

et al. 2020

Adv Materials Inter

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Steam condensation is omnipresent, and inevitable in many industrial processes. A classic example is seen within condensers that are used to liquify various gasses. In consequence, water‐vapor is eventually deposited upon the exterior of heat pipes that passively cool the gas to form a thin film of liquid. This macroscopic film is responsible for the degradation of heat transfer efficiencies. Liquid repellent surfaces can microscopically manipulate the hydrodynamics of formulating condensate to transition toward dropwise/jumping‐droplet condensation. This effect will save operating and maintenance costs of steam condensers within power‐plants, subsequently reducing emissions, operating power, and fuel consumption. However, the challenges associated with the stabilization of dropwise/jumping‐droplet condensation, especially at large subcooling temperatures and high supersaturation ratios, have prohibited the use of liquid repellent surfaces. This review aims to discuss recent improvements and understanding of dropwise/jumping‐droplet condensation surfaces on superhydrophobic surfaces. Numerous examples shall be included, showing experimental and numerical studies of various innovative properties of superhydrophobic structures. In addition, various fabrication techniques of superhydrophobic surfaces that are applicable within industrial systems are discussed. These topics are consolidated to provide guidelines for future research into dropwise/jumping‐droplet condensation on liquid repellent surfaces.

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Wetting transition of sessile and condensate droplets on copper-based superhydrophobic surfaces

Cited by 17 publications

References 57 publications

Ice Coverage Induced by Depositing a Water Drop onto the Supercooled Substrate at Extreme Low Vapor Pressure

Ice Coverage Induced by Depositing a Water Drop onto the Supercooled Substrate at Extreme Low Vapor Pressure

Fabrication of the superhydrophobic natural cellulosic paper with different wettability and oil/water separation application

Implementing Superhydrophobic Surfaces within Various Condensation Environments: A Review

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