scholarly journals Study of droplet dynamics and condensation heat transfer on superhydrophobic copper surface

2020 ◽  
pp. 89-89
Author(s):  
R. Yuvaraj ◽  
Kumar Senthkil
Keyword(s):  
Heat Transfer ◽  
Contact Angle ◽  
Water Droplet ◽  
Copper Substrate ◽  
Copper Plate ◽  
Solution Temperature ◽  
Dropwise Condensation ◽  
Tetradecanoic Acid ◽  
Maximum Contact ◽  
Bare Copper

Superhydrohobic surface for dropwise condensation is prepared using hotplate solution immersion method on copper substrate. The preprocessed bare copper plate is immersed in a solution consist of 0.004 - 0.008M ethanol (CH3?CH2?OH) and tetradecanoic acid (CH3(CH2)12COOH) then heating the plates in the solution at 30 - 50?C for 1 - 6 hours. The contact angle of water droplet on the prepared surface is measured using Low Bond Axisymmetric Drop Shape Analysis (LBADSA), which gives the maximum contact angle of 168? and average value of 166? ? 2?. The maximum contact angle is obtained by adjusting the composition of the solution, temperature of the solution and immersion time to 0.006M, 45? and 4 hours respectively. The various superhydrophobic surfaces are prepared by changing constituents of solution, hotplate temperature and processing time respectively. Further dynamic behavior of water droplet on the prepared surfaces like jumping effect and rolling effect is presented in this work. In addition, experimental work is carried out on the prepared surface for dropwise condensation and the obtained results are compared with condensation on bare copper plate produces higher heat transfer coefficient.

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.

Protective properties of superhydrophobic coatings on copper and steel obtained by electrochemical method

2021 ◽  
Vol 26 (1) ◽  
Keyword(s):  
Contact Angle ◽  
Copper Substrate ◽  
Copper Plate ◽  
Ethanol Solution ◽  
Cathodic Deposition ◽  
Sem Images ◽  
Protective Properties ◽  
Superhydrophobic Coatings ◽  
Water Wetting ◽  
Contact Angle Of Wetting

Superhydrophobic coatings are obtained by cathodic deposition of copper or nickel on a copper plate with treatment with an ethanol solution of highest carboxylic acids with a long hydrocarbon radical simultaneously or sequentially. They are characterized by a contact angle of water wetting of the order of 155...160°.These coatings protect the copper substrate from corrosion in conditions of 100% humidity for 100...180 days, while maintaining the contact angle within 152…154°. There is no mass loss. The influence of the reversal of the current during electrolysis on the value of the contact angle of wetting is investigated. SEM images of superhydrophobic coatings are presented, indicating multilevel roughness. Superhydrophobic coating on carbon steel is obtained by cathodic deposition of nickel and subsequent surface treatment in an ethanol solution of myristic acid and annealing at 60° for two hours. The influence of the duration of electrolysis on the value of the contact angle of wetting is estimated. Its value is in the range of 151…154°. Exposure of a coated steel plate for 50 days in conditions of 100% humidity is characterized by the absence of weight loss and maintaining the contact angle up to 154°.

The Effect of Nanofiber Mats on Dropwise Condensation

2012 ◽  
Vol 5 (1) ◽  
Author(s):  
J. Kraus ◽  
S. Sinha-Ray ◽  
A.L. Yarin
Keyword(s):  
Theoretical Analysis ◽  
Time Scale ◽  
Water Droplet ◽  
Short Time Scale ◽  
Dropwise Condensation ◽  
Water Droplets ◽  
Kelvin Effect ◽  
Nanofiber Mats ◽  
Short Time ◽  
Bare Copper

In this work, condensation characteristics of water droplet on metallized nanofibers mat on short time scale has been studied. It has been shown that condensation of water droplet on copper nanofibers mat is delayed to a great extent in comparison to condensation on bare copper. It has been observed that on copper nanofibers mat the number of water droplets is much less than on bare copper and did not cause film as on bare coppers. At the end theoretical analysis showed that such behavior can be explained by Kelvin effect.

The Effect of Thermal Resistance for Dropwise Condensation on Hydrophobic Micro-Pillared Structures

2012 ◽  
Author(s):  
Sara S. Beaini ◽  
Hector Mendoza ◽  
Van P. Carey
Keyword(s):  
Heat Transfer ◽  
Contact Angle ◽  
Surface Energy ◽  
Thermal Resistance ◽  
Droplet Growth ◽  
Dropwise Condensation ◽  
Textured Surfaces ◽  
Critical Question ◽  
Low Surface Energy ◽  
The Continuum

Superhydrophobic/hydrophobic surfaces, developed to promote dropwise condensation, can be produced by modifying the surface chemically with low surface energy films, and/or structurally by fabricating micro-textured surfaces. Some research has reported the increased thermal resistance from the added chemical layer and its effect on condensation heat transfer. A critical question of interest is the thermal resistance due to micro-pillared structures and their influence on droplet growth during condensation as compared to smooth or non-textured surfaces. Though idealized, this paper presents a theoretical and computational model for evaluating and quantifying the effects of the pillared structures thermal resistance, as well as the continuum versus non-continuum mechanisms affecting droplet growth during dropwise condensation. The model is used to compare different micro-pillared surfaces, cited in the literature, and to predict which micro-pillar dimensions contribute to slower condensate growth despite the higher contact angle advantage during dropwise condensation.

Submicron Superhydrophobic Surface Treatment Suitable for High Performance Condensers: A Modeling

2009 ◽  
Author(s):  
Sunwoo Kim ◽  
Kwang J. Kim ◽  
John M. Kennedy ◽  
Jiong Liu ◽  
Ganesh Skandan
Keyword(s):  
Heat Transfer ◽  
Contact Angle ◽  
Theoretical Model ◽  
Size Distribution ◽  
Drop Size ◽  
Drop Size Distribution ◽  
Condensation Heat Transfer ◽  
Dropwise Condensation ◽  
Superhydrophobic Coating ◽  
Single Droplet

The effect of the drop-contact angle on dropwise condensation heat transfer of saturated steam on a single horizontal copper tube with the superhydrophobic coating was investigated theoretically. The theoretical model is established by combining heat transfer through a single droplet with a well-known drop size distribution theory. The analysis of single droplet heat transfer incorporates resistances due to vapor-liquid interface, drop curvature, conduction through the drop, and conduction through the superhydrophobic coating layer. Each resistance is expressed as a function of the contact angle. The total resistance for a drop with a fixed radius increases as the contact angle increases. A population balance model is used to develop a drop distribution function for the small drops that grow by direct condensation. Drop size distribution for large drops that grow mainly by coalescence is obtained from the empirical equation proposed by Le Fevre and Rose (1966). The results indicate that the contact angle has a strong correlation with the maximum drop radius, which plays a pivotal role in determining drop size distribution. A high contact angle leads to a significant reduction in the radius of the largest drop that is about to fall down due to gravity and sweep away drops in its path. Thus, there are more areas on the condensing surface for small drops, allowing for greater heat transfer. Also, it is shown that surface wettability affects the performance of dropwise condensation heat transfer and our theoretical model successfully predicts this phenomenon.

Dropwise Condensation Heat Transfer Model: Effect of the Liquid-Solid Surface Free Energy Difference

2006 ◽  
Author(s):  
Xue-Hu Ma ◽  
Zhong Lan ◽  
Yu Zhang ◽  
Xing-Dong Zhou ◽  
Tian-Yi Sun
Keyword(s):  
Heat Transfer ◽  
Contact Angle ◽  
Free Energy ◽  
Heat Transfer Coefficient ◽  
Energy Difference ◽  
Interfacial Interaction ◽  
Condensation Heat Transfer ◽  
Dropwise Condensation ◽  
Free Energy Difference ◽  
Simulation Results

Dropwise condensation heat transfer performance depends not only on the condensing conditions, but also on the interfacial interaction between condensate and condensing surface material. Based on the well-established Rose’s model, a modified model of dropwise condensation heat transfer is proposed by considering the interfacial interaction between liquid and solid, and established by rebuilding the space conformation of drop distributing into time conformation. The simulation results indicate that the heat transfer coefficient increases with the surface free energy difference increasing and the contact angle hysteresis decreasing. The larger contact angle and the smaller departure drop size result in the higher heat transfer coefficient. Different interfacial effect gives rise to the different heat transfer curves. For the identical solid-liquid-vapor system, the simulation results agree very well with the present experimental data and those reported in literature. The controversy among experimental results in literature might be well understood with the concept of the present paper.

scholarly journals Effect of Contact Angle on Steam Dropwise Condensation: A Simulation Approach

2012 ◽  
Vol 2012 ◽  
pp. 1-7
Author(s):  
Milad Nahavandi ◽  
Arjomand Mehrabani-Zeinabad
Keyword(s):  
Heat Transfer ◽  
Contact Angle ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Distribution Coefficient ◽  
Size Distribution ◽  
Atmospheric Pressure ◽  
Simulated Data ◽  
Condensation Process ◽  
Dropwise Condensation

Dropwise condensation process on surface of a vertical polytetrafluouroethylene (PTFE) plate at atmospheric pressure was simulated. Comparison of simulated data with experimental and theoretical results indicates that performed simulation results confirm experimental data, although they deviated from existing proposed correlations. For calculation of heat transfer coefficient and droplets size distribution, simulation of condensation process over vertical copper and PTFE surfaces at atmospheric pressure was performed. By considering the effect of contact angle on heat transfer resistances of droplets, the gained data were optimized in order to evaluate droplets size distribution coefficient. This distribution coefficient was used in a new correlation for prediction of heat transfer coefficient for dropwise condensation process. Comparison of experimental results with the correlation shows a good agreement, 11% relative error.

Dropwise Condensation Modeling Suitable for Superhydrophobic Surfaces

2011 ◽  
Vol 133 (8) ◽  
Author(s):  
Sunwoo Kim ◽  
Kwang J. Kim
Keyword(s):  
Heat Transfer ◽  
Contact Angle ◽  
Size Distribution ◽  
Drop Size ◽  
Contact Angles ◽  
Drop Size Distribution ◽  
Balance Model ◽  
Dropwise Condensation ◽  
Interfacial Resistance ◽  
Single Droplet

A mathematical model is developed to represent and predict the dropwise condensation phenomenon on nonwetting surfaces having hydrophobic or superhydrophobic (contact angle greater than 150 deg) features. The model is established by synthesizing the heat transfer through a single droplet with the drop size distribution. The single droplet heat transfer is analyzed as a combination of the vapor-liquid interfacial resistance, the resistance due to the conduction through the drop itself, the resistance from the coating layer, and the resistance due to the curvature of the drop. A population balance model is adapted to develop a drop distribution function for the small drops that grow by direct condensation. Drop size distribution for large drops that grow mainly by coalescence is obtained from a well-known empirical equation. The evidence obtained suggests that both the single droplet heat transfer and drop distribution are significantly affected by the contact angle. More specifically, the model results indicate that a high drop-contact angle leads to enhancing condensation heat transfer. Intense hydrophobicity, which produces high contact angles, causes a reduction in the size of drops on the verge of falling due to gravity, thus allowing space for more small drops. The simulation results are compared with experimental data, which were previously reported.

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