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An experimental investigation into the icing and melting process of a water droplet impinging onto a superhydrophobic surface

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Science China(Physics,Mechanics & Astronomy) 2013年第11期56卷 2047-2053页

作者： JIN ZheYan JIN SongYue YANG ZhiGang School of Aerospace Engineering and Applied Mechanics Tongji University School of Automotive Studies Tongji University Shanghai Automotive Wind Tunnel Center

The freezing and melting process of a small water droplet on a superhydrophobic cold surface was investigated using the Laser Induced Fluorescence(LIF)*** superhydrophobic surface was prepared using a sol-gel method on a red copper test *** the obtained fluorescence images,the phase transition characteristics during the freezing and melting process of a water droplet were clearly *** was found that,at the beginning of the droplet freezing process,liquid water turned into ice at a very fast *** phase transition process decreased gradually with time and the volume of frozen ice approached a constant value at the end of the icing *** addition,the freezing time was found to reduce with the decrease of the test plate ***,when the test plate temperature is relatively high,the effect of droplet volume on the freezing time is very *** all,we provide some tentative insights into the microphysical process related to the icing and melting process of water droplets.

关键词： sol-gel icing melting superhydrophobic surface water droplet

SLIPS-TENG: robust triboelectric nanogenerator with optical and charge transparency using a slippery interface

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National Science Review 2019年第3期6卷 540-550页

作者： Wanghuai Xu Xiaofeng Zhou Chonglei Hao Huanxi Zheng Yuan Liu Xiantong Yan Zhengbao Yang Michael Leung Xiao Cheng Zeng Ronald X.Xu Zuankai Wang Department of Mechanical Engineering City University of Hong Kong Department of Precision Machinery and Precision Instrumentation University of Science and Technology of China Shanghai Key Laboratory of Multidimensional Information Processing Department of Electronic Engineering East China Normal University Department of Chemistry University of Nebraska-Lincoln School of Energy and Environment City University of Hong Kong Department of Materials Science and Engineering City University of Hong Kong

Energy harvesting devices that prosper in harsh environments are highly demanded in a wide range of applications ranging from wearable and biomedical devices to self-powered and intelligent ***, over the past several years, the innovation of triboelectric nanogenerators(TENGs) that efficiently convert ambient kinetic energy of water droplets or wave power to electricity has received growing attention. One of the main bottlenecks for the practical implications of such devices originates from the fast degradation of the physiochemical properties of interfacial materials under harsh environments. To overcome these challenges, here we report the design of a novel slippery lubricant-impregnated porous surface(SLIPS) based TENG, referred to as SLIPS-TENG, which exhibits many distinctive advantages over conventional design including optical transparency, configurability, self-cleaning, flexibility, and power generation stability, in a wide range of working environments. Unexpectedly, the slippery and configurable lubricant layer not only serves as a unique substrate for liquid/droplet transport and optical transmission,but also for efficient charge transfer. Moreover, we show that there exists a critical thickness in the liquid layer, below which the triboelectric effect is almost identical to that without the presence of such a liquid film. Such an intriguing charge transparency behavior is reminiscent of the wetting transparency and van der Waals potential transparency of graphene previously reported, though the fundamental mechanism remains to be elucidated. We envision that the marriage of these two seemingly totally different arenas(SLIPS and TENG) provides a paradigm shift in the design of robust and versatile energy devices that can be used as a clean and longer-lifetime alternative in various working environments.

关键词： slippery surface triboelectricity power generation water droplet interfaces

Non-negligible factors in low-pressure sprinkler irrigation:droplet impact angle and shear stress

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Journal of Arid Land 2022年第11期14卷 1293-1316页

作者： HUI Xin ZHENG Yudong MUHAMMAD Rizwan Shoukat TAN Haibin YAN Haijun College of water Resources and Civil Engineering China Agricultural UniversityBeijing 100083China Engineering Research Center of Agricultural water-Saving and water Resources Ministry of EducationBeijing 100083China Semi-arid Agriculture Engineering&Technology Research Center of China Shijiazhuang 050051China

droplet shear stress is considered as an important indicator that reflects soil erosion in sprinkler irrigation more accurately than kinetic energy,and the effect of droplet impact angle on the shear stress cannot be *** this study,radial distribution of droplet impact angles,velocities,and shear stresses were investigated using a two-dimensional video disdrometer with three types of low-pressure sprinkler(Nelson D3000,R3000,and Komet KPT)under two operating pressures(103 and 138 kPa)and three nozzle diameters(3.97,5.95,and 7.94 mm).Furthermore,the relationships among these characteristical parameters of droplet were analyzed,and their influencing factors were comprehensively *** various types of sprinkler,operating pressures,and nozzle diameters,the smaller impact angles and larger velocities of droplets were found to occur closer to the sprinkler,resulting in relatively low droplet shear *** increase in distance from the sprinkler caused the droplet impact angle to decrease and velocity to increase,which contributed to a significant increase in the shear stress that reached the peak value at the end of the ***,the end of the jet was the most prone to soil erosion in the radial direction,and the soil erosion in sprinkler irrigation could not only be attributed to the droplet kinetic energy,but also needed to be combined with the analysis of its shear *** comparing the radial distributions of average droplet shear stresses among the three types of sprinklers,D3000 exhibited the largest value(26.94-3313.51 N/m^(2)),followed by R3000(33.34-2650.80 N/m^(2)),and KPT(16.15-2485.69 N/m^(2)).From the perspective of minimizing the risk of soil erosion,KPT sprinkler was more suitable for low-pressure sprinkler irrigation than D3000 and R3000 *** addition to selecting the appropriate sprinkler type to reduce the droplet shear stress,a suitable sprinkler spacing could also provide acceptable results,because the distance

关键词： center pivot irrigation system water droplet universal model soil erosion water-saving irrigation

droplet Breakup Regime in a Cross-Junction Device with Lateral Obstacles

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Fluid Dynamics & Materials Processing 2019年第5期15卷 545-555页

作者： Tawfiq Chekifi Research Center in Industrial Technologies CRTI P.O.Box 64Cheraga AlgiersAlgeria

Numerical simulation using Ansys Fluent code is performed,to investigate droplet generation in cross-junction based VOF *** of water are generated by the shear stress applied by continuous phase(oil),two configurations of cross-junction are suggested;the first is a simple model no modification is performed at the outer channel,while the second model is characterized by a lateral *** study the effect of velocity ratio,viscous parameter,interfacial tension,flow condition on droplet size and frequency,the effect of lateral obstacles on droplets generation is also focused and *** numerical simulations showed that the velocity ratio and interfacial tension play a significant role in determining the droplet breakup and *** the other side,the increase of flow rate ratio can be effectively used to decrease the droplet *** addition,droplets produced in cross-junction with lateral obstacles are generally found to be larger than that produced with the first ***,the frequency of droplet production was increasing by increasing of flow rate *** numerical results show very good agreements with previous numerical and experimental works for the growth of droplet breakup,size and frequency.

关键词： water droplet cross-junction CFD VOF microchannel

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人工覆冰与自然覆冰等效性研究(英文)

高电压技术 2011年第11期37卷 2843-2848页

作者：韦晓星许志海李志宁苏华锋贾志东关志成 Graduate School at Shenzhen Tsinghua University

Climate room is an important instrument to study the icing problems in power networks,and the accuracy of the data from the climate room is under *** are many climate rooms in the world,but no standards about the parameters of the climate room such as the room's temperature,the velocity of the wind,and the particle diameters of the water droplets *** parameters will influence the icing processes on the lines and *** paper gave a summary of the process and the feature of atmospheric icing of power *** speed of the icing on a cylinder rod as a new characteristic quantity was proposed to study the de-icing problems in this *** the purpose to analyze the equivalence between atmospheric icing and icing in climate room,a finite element model was made based on a small climate room located in the Graduate School at Shenzhen,Tsinghua *** the simulation analysis for the heat transfer and flow issues,the result showed that precooling droplets were cooled into supercooled ones soon after they came into the climate *** on the most serious icing-speed in Hengshan,Hunan and a series of experiments,the values of some parameters in studying icing problems were proposed to better simulate the atmospheric icing in climate room.

关键词： icing icing speed icing parameter climate room finite element method water droplet

Measurement of Concentration of Sorbent Particles and water droplets in Hydration Desulfurization Reactor with PIV

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Journal of Southeast University(English Edition) 2002年第1期18卷 88-91页

作者：赵长遂吴树志刘现卓肖军陆勇王式民东南大学热能工程研究所洁净煤发电及燃烧技术教育部重点实验室南京210096

Vortexing limestone injection into furnace combined with calcium lime hydration in the downstream is the most promising technology for controlling SO 2 emission. Particle imaging velocimetry (PIV) is used to measure the gas liquid solid three phase flow field in a reactor. By image processing based on newly developed software, the number concentrations of sorbent particles and water droplets are presented. The measuring results are very helpful for better understanding the desulfurization mechanism and optimizing configurational and operational parameters in the hydration reactor. 

关键词： particle image velocimetry desulfurization particle water droplet concentration