The possibility for realizing dropwise condensation with small contact angle

2003 ◽  
Vol 52 (10) ◽  
pp. 2427
Author(s):  
Cao Zhi-Jue ◽  
Xia Bo-Li ◽  
Zhang Yun
Keyword(s):  
Contact Angle ◽  
Dropwise Condensation ◽  
Small Contact Angle

A Heat Transfer Model of Dropwise Condensation Underneath a Horizontal Substrate

2011 ◽  
Vol 199-200 ◽  
pp. 1604-1608
Author(s):  
Yun Fu Chen
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Contact Angle ◽  
Fractal Model ◽  
Condensation Heat Transfer ◽  
Droplet Growth ◽  
Transfer Model ◽  
Dropwise Condensation ◽  
Small Contact Angle ◽  
Horizontal Substrate

For finding influence of the condensing surface to dropwise condensation heat transfer, a fractal model for dropwise condensation heat transfer has been established based on the self-similarity characteristics of droplet growth at various magnifications on condensing surfaces with considering influence of contact angle to heat transfer. It has been shown based on the proposed fractal model that the area fraction of drops decreases with contact angle increase under the same sub-cooled temperature; Varying the contact angle changes the drop distribution; higher the contact angle, lower the departing droplet size and large number density of small droplets; dropwise condensation translates easily to the filmwise condensation at the small contact angle ;the heat flux increases with the sub-cooled temperature increases, and the greater of contact angle, the more heat flux increases slowly.

scholarly journals Dropwise condensation on bioinspired hydrophilic-slippery surface

RSC Advances ◽  
2018 ◽  
Vol 8 (69) ◽  
pp. 39341-39351 ◽  
Author(s):  
L. Guo ◽  
G. H. Tang
Keyword(s):  
Heat Transfer ◽  
Contact Angle ◽  
Water Transport ◽  
Nucleation Rate ◽  
Copper Surface ◽  
Dropwise Condensation ◽  
Sliding Angle ◽  
Small Contact Angle ◽  
Slippery Surface

A hydrophilic-slippery copper surface is fabricated, reconciling two required factors, enhanced condensation and efficient water transport. Nucleation rate, droplet mobility and heat transfer are enhanced by the small contact angle and sliding angle.

A Study of Effect of Wettability on Heterogeneous Condensation: Varied Substrates

2007 ◽  
Author(s):  
Sriharsha Pulipaka ◽  
Sang Young Son
Keyword(s):  
Contact Angle ◽  
Surface Temperature ◽  
Surface Property ◽  
Vital Role ◽  
Distilled Water ◽  
Dropwise Condensation ◽  
Hydrophobic Substrate ◽  
Heterogeneous Condensation ◽  
Visualization Experiments

Contact angle as a surface property of the substrate plays a vital role in the process of heterogeneous condensation. This paper deals with the visualization experiments that have been carried out to study the dropwise condensation of the vapor of degassed distilled water on hydrophobic substrate and the filmwise condensation on hydrophilic substrate. A study on effect of substrate wettability on the growth of the condensate drop on various surfaces is presented and compared. Also trend of the variation of the surface temperature for various substrates during condensation is presented.

Lattice Boltzmann simulation of immiscible displacement in the cavity with different channel configurations

2017 ◽  
Vol 28 (11) ◽  
pp. 1750136 ◽  
Author(s):  
Qin Lou ◽  
Chenqiang Zang ◽  
Mo Yang ◽  
Hongtao Xu
Keyword(s):  
Surface Roughness ◽  
Contact Angle ◽  
Lattice Boltzmann ◽  
Contact Angles ◽  
Surface Wettability ◽  
Immiscible Displacement ◽  
Displacement Efficiency ◽  
Small Contact Angle ◽  
Gas Cavity ◽  
Pseudo Potential

In this work, the immiscible displacement in a cavity with different channel configurations is studied using an improved pseudo-potential lattice Boltzmann equation (LBE) model. This model overcomes the drawback of the dependence of the fluid properties on the grid size, which exists in the original pseudo-potential LBE model. The approach is first validated by the Laplace law. Then, it is employed to study the immiscible displacement process. The influences of different factors, such as the surface wettability, the distance between the gas cavity and liquid cavity and the surface roughness of the channel are investigated. Numerical results show that the displacement efficiency increases and the displacement time decreases with the increase of the surface contact angle. On the other hand, the displacement efficiency increases with increasing distance between the gas cavity and the liquid cavity at first and finally reaches a constant value. As for the surface roughness, two structures (a semicircular cavity and a semicircular bulge) are studied. The comprehensive results show that although the displacement processes for both the structures depend on the surface wettability, they present quite different behaviors. Specially, for the roughness structure constituted by the semicircular cavity, the displacement efficiency decreases and displacement time increases evidently with the size of the semicircular cavity for the small contact angle. The trend slows down as the increase of the contact angle. Once the contact angle exceeds a certain value, the size of the semicircular cavity almost has no influence on the displacement process. While for the roughness structure of a semicircular bulge, the displacement efficiency increases with the size of bulge first and then it decreases for the small contact angle. The displacement efficiency increases first and finally reaches a constant for the large contact angle. The results also show that the displacement time has an extreme value in these cases for the small contact angles.

Photocatalytic and Self-Cleaning Properties of TiO2-Cu Thin Films on Glass Substrate

2012 ◽  
Vol 152-154 ◽  
pp. 409-413 ◽  
Author(s):  
Weerachai Sangchay ◽  
Lek Sikong ◽  
Kalayanee Kooptarnond
Keyword(s):  
Thin Films ◽  
Contact Angle ◽  
Uv Irradiation ◽  
Sol Gel ◽  
Dip Coating ◽  
Glass Slides ◽  
Coating Method ◽  
Small Contact Angle ◽  
Self Cleaning ◽  
Dip Coating Method

TiO2-Cu thin films containing 0 to 1%Cu coated on glass slides were prepared by sol gel-dip coating method. The prepared thin films were synthesized at the temperature of 400 ◦C for 2 h with a heating rate of 10◦C/min. The microstructures of synthesized TiO2-Cu thin films were characterized by XRD, FT-IR and SEM. The photocatalytic activities of TiO-2Cu thin films were tested using methylene blue (MB) solution under UV irradiation. Finally, the self-cleaning property was evaluated by means of contact angle of water droplet on the films. The results show all samples have the thickness in range of 1 um and surfaces are dense with a large surface area. It can be noted that TiO2-1.0Cu thin films were found to give the highest photocatalytic efficiency and exhibited self-cleaning effect (small contact angle, 17°) under UV irradiation.

Measurement of Liquid Film Thickness by a Fringe Method

2007 ◽  
Author(s):  
Akira Kariyasaki ◽  
Akiharu Ousaka ◽  
Yoshikazu Yamasaki ◽  
Masazumi Kagawa ◽  
Tohru Nagashima ◽  
...  
Keyword(s):  
Contact Angle ◽  
Liquid Film ◽  
Liquid Droplet ◽  
Estimation Error ◽  
Three Dimensional ◽  
Laser Speckle ◽  
Objective Lens ◽  
Laser Focus ◽  
Flow Phenomena ◽  
Small Contact Angle

A technique to measure the local thickness of a droplet or a liquid film by an interference fringe pattern that was formed by reflecting laser lights was developed and tested. Monochromatic epi-illumination through an objective lens of a microscope was provided by a 5mw-300mw laser and a filter to remove the noise caused by laser speckle. The incremental height difference of the liquid layer between neighboring maxima or minima of fringes was evaluated from the wavelength of the laser light and the refractive index of the liquid. Estimation error of a local inclination angle was discussed using ray tracing under parallel illumination approximation (Ku¨hner et al., 1996). Droplet profiles evaluated from the interferogram that were obtained by the present fringe method agreed well with those by Laser Focus Displacement Meter (LFD) (Fukamachi et al., 2003). Measurement was tried to make sure the usefulness of the present technique. It was made clear that a) contact angle of a liquid droplet could be obtained precisely and swiftly even in small size or small contact angle, and b) instantaneous three dimensional profile of a liquid film on a bubble moving in a micro-channel could be measured. The fringe method had sufficient potential to obtain more detailed information about three dimensional characteristics of liquid film in flow phenomena such as the generation, break down and growth of waves and the liquid film of a bubble at the beginning of movement.

Dropwise Condensation Underneath Chemically Textured Surfaces: Simulation and Experiments

2010 ◽  
Vol 133 (2) ◽  
Author(s):  
Basant Singh Sikarwar ◽  
Nirmal Kumar Battoo ◽  
Sameer Khandekar ◽  
K. Muralidhar
Keyword(s):  
Contact Angle ◽  
Model Simulation ◽  
Contact Angle Hysteresis ◽  
Saturation Temperature ◽  
Static Contact Angle ◽  
Order Effects ◽  
Textured Surface ◽  
Dropwise Condensation ◽  
Textured Surfaces ◽  
Static Contact

Experimental observations of dropwise condensation of water vapor on a chemically textured surface of glass and its detailed computer simulation are presented. Experiments are focused on the pendant mode of dropwise condensation on the underside of horizontal and inclined glass substrates. Chemical texturing of glass is achieved by silanation using octyl-decyl-tri-chloro-silane (C18H37C13Si) in a chemical vapor deposition process. The mathematical model is built in such a way that it captures all the major physical processes taking place during condensation. These include growth due to direct condensation, droplet coalescence, sliding, fall-off, and renucleation of droplets. The effects arising from lyophobicity, namely, the contact angle variation and its hysteresis, inclination of the substrate, and saturation temperature at which the condensation is carried out, have been incorporated. The importance of higher order effects neglected in the simulation is discussed. The results of model simulation are compared with the experimental data. After validation, a parametric study is carried out for cases not covered by the experimental regime, i.e., various fluids, substrate inclination angle, saturation temperature, and contact angle hysteresis. Major conclusions arrived at in the study are the following: The area of droplet coverage decreases with an increase in both static contact angle of the droplet and substrate inclination. As the substrate inclination increases, the time instant of commencement of sliding of the droplet is advanced. The critical angle of inclination required for the inception of droplet sliding varies inversely with the droplet volume. For a given static contact angle, the fall-off time of the droplet from the substrate is a linear function of the saturation temperature. For a given fluid, the drop size distribution is well represented by a power law. Average heat transfer coefficient is satisfactorily predicted by the developed model.

Effects of Interference Fit and Preload on the Performance of Low-Speed Angular Contact Ball Bearing

2010 ◽  
Vol 97-101 ◽  
pp. 3408-3412 ◽  
Author(s):  
Wei Hua Ni ◽  
Zheng Qiang Yao ◽  
Jun Tong Xi
Keyword(s):  
Contact Angle ◽  
Ball Bearing ◽  
Radial Clearance ◽  
Axial Stiffness ◽  
Angular Contact Ball Bearing ◽  
Element Analysis ◽  
Interference Fit ◽  
Low Speed ◽  
The Finite Element Analysis ◽  
Small Contact Angle

Based on static analysis, this paper investigates the effects of interference fit and axial preload on the performance of the low-speed angular contact ball bearing. The results show the bearing with heavy preload and large radial clearance has big contact angle and high axial stiffness. Besides, large interference could result in small contact angle but high axial stiffness. When the bearing has large interference the axial stiffness increases rapidly due to the effect of interference on the axial stiffness stronger than that of contact angle. And the stiffness formula in the paper could provide boundary conditions for the finite element analysis of spindle-bearing system.

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