Droplets Jumping from a Hybrid Superhydrophilic and Superhydrophobic Surface

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
Hai Wang ◽  
Quang Nguyen ◽  
Jae W. Kwon ◽  
Jing Wang ◽  
Hongbin Ma
Keyword(s):  
Contact Angle ◽  
Copper Substrate ◽  
Copper Surface ◽  
Film Condensation ◽  
Condensation Process ◽  
Nanostructured Surface ◽  
Additional Energy ◽  
Ammonium Persulphate ◽  
Condition Effect ◽  
Superhydrophilic Surface

The wetting condition effect of the condensation process on a hybrid superhydrophobic and superhydrophilic copper surface as shown in Fig. 1a was experimentally investigated. The superhydrophilic surface (Fig. 1b) consists of micro-flowers (CuO) and nanorods (Cu(OH)2) obtained by immersing the copper substrate into alkaline solution of 2.5 M sodium hydroxide and 0.1 M ammonium persulphate, and the superhydrophobic nanostructured surface (Fig. 1c) was formed by spin coating the Cytop on the hierarchically structured CuO / Cu(OH)2 surface. Experimental results show that the film condensation started on the superhydrophilic region while the dropwise condensation of tiny droplets with an average contact angle of 160° were formed on the superhydrophobic region. Because the film condensation was confined within the superhydrophilic region of 1 mm x 1 mm, the contact angle of this droplet became larger and larger. When a tiny droplet developed on the superhydrophobic area joins with the big droplet formed on the superhydrophilic surface (square region), the coalesced droplet obtains additional energy and jumps off from the condensing surface.

Effect of Polymer Coating on Vapor Condensation Heat Transfer

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Mete Budakli ◽  
Thamer Khalif Salem ◽  
Mehmet Arik ◽  
Barca Donmez ◽  
Yusuf Menceloglu
Keyword(s):  
Heat Transfer ◽  
Saturation Pressure ◽  
Copper Substrate ◽  
Copper Surface ◽  
Vapor Condensation ◽  
Condensation Heat Transfer ◽  
Condensation Process ◽  
Limiting Factor ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

Abstract Condensation heat transfer coefficients (HTCs) are rather low compared to thin film evaporation. Therefore, it can be a limiting factor for designing heat transfer equipment. In this work, heat transfer characteristics of water vapor condensation phenomena were experimentally studied on a vertically aligned smooth copper substrate for a range of pressures and temperatures for two different liquid wettability conditions. The heat transfer performance is dominated by the phase change process at the solid–vapor interface along with the liquid formation mechanism. Compared to heat transfer results measured at an untreated copper surface, heat transport is augmented with a thin layer of perfluoro-silane coating over the same substrate. In this work, the effect of saturation pressure on the condensation process at both surfaces has been investigated by analyzing heat transfer coefficients. The results obtained experimentally show an increase in contact angle (CA) with the surface coating. A heat transfer augmentation of about 26% over uncoated surfaces was obtained and surfaces did not show any degradation after 40 h of operation. Finally, current results are compared with heat transfer values reported in open literature.

Frosting Characteristics on Hydrophilic and Superhydrophobic Copper Surfaces

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
Chan Ho Jeong ◽  
Jae Bin Lee ◽  
Seong Hyuk Lee ◽  
Jungho Lee ◽  
Seung Mun You ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Copper Substrate ◽  
Copper Surface ◽  
Contact Angles ◽  
Film Condensation ◽  
Time Interval ◽  
Copper Surfaces ◽  
Static Contact ◽  
Temperature Detector ◽  
Bare Copper

The main objective of this study is to examine the frosting characteristics affected by the surface wettability. Two different copper surfaces – bare and nano structured - were prepared for the experiments. Their static contact angles are 74° (bare: without surface treatment) and 154° (nano-structured), respectively. The temperature of the copper substrate was measured by using resistance temperature detector (RTD) sensors embedded inside small holes drilled at 1 mm underneath the surface. During the phase change, the temperature of the copper substrates remained -7.8±0.6°C and the ambient temperature was set as 24±0.5°C with the relative humidity of 45%. Images were captured by using the CMOS camera with the 5 second time interval. Film condensation occurred because of higher wettability of the bare copper surface. Film condensates were frozen at the early stage and frost crystal grew in the vertical direction. On the other hand, dropwise condensates formed on the nano-structured copper surface remained as the supercooled liquid phase for 44 minutes owing to its low wettability. After 4 minutes, frosting on the bare copper substrate was triggered and propagated until it covered the whole surface. The frosting was significantly delayed on the superhydrophobic copper surface due to the lower surface free energy. The different porous media composed of frost which directly influence the heat transfer characteristics was formed on each surfaces. Therefore, additional investigation for heat transfer phenomenon on superhydrophobic surface should be conducted.

Contact Angle Variation on a Copper Surface Treated With Self-Assembled Monolayer (SAM) of N-octadecyl Mercaptan

2011 ◽  
Vol 133 (8) ◽  
Author(s):  
Yulong Ji ◽  
Hsiu-hung Chen ◽  
Qingsong Yu ◽  
Xuehu Ma ◽  
H. B. Ma
Keyword(s):  
Contact Angle ◽  
Copper Surface ◽  
Self Assembled Monolayer ◽  
Angle Variation ◽  
Self Assembled

scholarly journals Corrosion prevention of commercial alloys by air-water interface grown, edge on oriented, ultrathin squaraine film

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Rajiv Kumar Pandey ◽  
Richa Mishra ◽  
Gopal Ji ◽  
Rajiv Prakash
Keyword(s):  
Corrosion Protection ◽  
Surface Characterization ◽  
Electrochemical Techniques ◽  
Copper Substrate ◽  
Chemical Properties ◽  
Copper Surface ◽  
Ultrathin Film ◽  
Water Interface ◽  
Acid Media ◽  
Air Water Interface

Abstract Copper is one of the most demanded commercial metal/alloys in world market. The demand for copper in industries such as electrical, electronics, automobile, telecommunications, defence, etc. as well as in daily life has escalated in the recent years due to its versatile physical and chemical properties. However destruction of copper surface by any means, preferably corrosion, can limit its vast application. For protection from corrosion, various techniques are used to coat metal substrates with passivating materials. These techniques are either complex as well as expensive, or provide incomplete protection in acid media. To address these issues, floating film transfer method (FFTM) is utilized in this work for obtaining ultrathin film of squaraine (passivating molecule) as well as their easy and fast transfer over copper substrate. The squaraine film is deposited on copper substrate in layers, viz., 1 to 4 layers. The corrosion behavior is examined in 0.1 M HCl using electrochemical techniques as well as surface characterization techniques, which portray that copper corrosion is hampered in harmony with the layers deposited. Nearly 40% corrosion protection is reached for copper coated with 1 layer of squaraine. However, the protection is amplified up to 98% with 4 layers of squaraine, which clearly substantiates the supremacy of this coating method over reported methods of protection. This technique and the material (squaraine) are both for the first time being used in the field of corrosion protection. The easy growth of ultrathin film at air-water interface as well as its rapid transfer over substrate promotes use of FFTM for efficient corrosion protection on industrial scale.

Effect of SiC Particles Addition on the Wettability and Intermetallic Compound Layer Formation of Sn-Cu-Ni (SN100C) Solder Paste

2015 ◽  
Vol 754-755 ◽  
pp. 546-550 ◽  
Author(s):  
Rita Mohd Said ◽  
Norainiza Saud ◽  
Mohd Arif Anuar Mohd Salleh ◽  
Mohd Nazree Derman ◽  
Mohd Izrul Izwan Ramli ◽  
...  
Keyword(s):  
Contact Angle ◽  
Intermetallic Compound ◽  
Composite Solder ◽  
Copper Substrate ◽  
Compound Layer ◽  
Intermetallic Compound Layer ◽  
Solder Paste ◽  
X Ray Diffraction ◽  
Free Solder ◽  
Sic Particle

The effects of SiC on wettability and intermetallic compound (IMC) formation of Sn-Cu-Ni solder paste composite were systematically investigated. Lead-free solder paste composite was produced by mixing silicon carbide (SiC) particle with Sn-Cu-Ni (SN100C) solder paste. The wettability of composite solder was studied by observing the contact angle between solder and copper substrate. The IMC phase formation on copper substrate interface was identified using X-ray diffraction (XRD). The phase as detected in the composite solder is Cu6Sn5.The wettability of composite solder was observed through contact angle between solder and copper substrate and Sn-Cu-Ni + 1.0 wt.% SiC shows improvements in wetting angle and suppresses the IMCs formation.

Molecular Dynamics Simulation of Explosive Boiling on Concave Nanostructured Surface

2018 ◽  
Author(s):  
Pengfei Ji ◽  
Mengzhe He ◽  
Yiming Rong ◽  
Yuwen Zhang ◽  
Yong Tang
Keyword(s):  
Surface Area ◽  
Flat Surface ◽  
Liquid Argon ◽  
Copper Surface ◽  
Heat Transfer Process ◽  
Dynamics Simulation ◽  
Nanostructured Surface ◽  
Explosive Boiling ◽  
Nanostructured Surfaces ◽  
Set Up

Explosive boiling occurs when a liquid film contacts with the wall at extremely high temperature, which is detrimental to continuous heat transfer process. In this paper, five kinds of nanostructured surfaces with equal distance between neighboring nano-concaves and flat surface are set up to study the explosive boiling of liquid argon on copper surface. For all the five cases with concave nanostructured surface, the ratio of concave nanostructured surface area to flat surface area is kept as a constant. The temporal and spatial distributions of temperature, atomic motion and number density are recorded to study the effects of different nanostructured surface designs on explosive boiling. From the perspective of reducing explosive boiling, the most favorable nanostructured surface is determined.

Two-Phase Heat Transfer in Thermosyphon Evacuated-Tube Solar Collectors

1989 ◽  
Vol 111 (4) ◽  
pp. 292-297 ◽  
Author(s):  
Karen R. Den Braven
Keyword(s):  
Heat Transfer ◽  
Surface Waves ◽  
Film Surface ◽  
Detailed Examination ◽  
Film Condensation ◽  
Condensation Process ◽  
Two Phase ◽  
Number Range ◽  
Laminar Film Condensation ◽  
Evacuated Tube

This work analyzes the heat transfer within a tilted thermosyphon and its use in a heat pipe evacuated-tube solar collector. A detailed examination is made of the laminar film condensation process, including the effects of interfacial shear due to the moving vapor. Effects of film surface waves are later included. Including the shear term in the constitutive equations changes the predicted film thickness in the condenser portion of the device by less than one percent, depending on location along the surface. This change causes only a slight increase in the predicted heat transfer. Accounting for surface waves increases the heat transfer rate 10 percent to 50 percent in the Reynolds number range studied. The condenser results are combined with a simple trough model for the evaporator portion of the thermosyphon to give the effective heat-transfer coefficient for the entire tube. Predicted performances of the condenser, the evaporator, and the entire tube compare favorably with available data.

Theoretical Study of Wetting Transformation on Regularly Hexagonal Array of Copper Surface

2014 ◽  
Vol 621 ◽  
pp. 56-60
Author(s):  
Guang Rui Shang ◽  
Qing Cheng Wang ◽  
Xiao Dong Yang
Keyword(s):  
Contact Angle ◽  
Theoretical Study ◽  
Hydrophobic Surface ◽  
Copper Surface ◽  
Apparent Contact Angle ◽  
Hexagonal Array

In this thesis we provide the electrodeposition technology by means of monolayer templates for fabricating regularly hexagonal array of copper surface, predict the wetting transformation in theory. We report the result that original hydrophilic copper surface may turn to be hydrophobic surface by this kind of structurization. The apparent contact angle would convert from less thanto more than.

Sign in / Sign up

Export Citation Format

Share Document