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n-Octadecanethiol Self-Assembled Monolayer Coating with Microscopic Roughness for dropwise condensation of Steam

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Journal of Thermal Science 2009年第2期18卷 160-165页

作者： Liang CHEN Shiqiang LIANG Runsheng YAN Yanjun CHENG Xiulan HUA Shuling CHEN Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing 100190 China College of Mechanical and Electronic Control Engineering Beijing Jiaotong University Beijing 100044 China Institute of Light Industry Environment Protect Beijing 100089 China

Here we presented a novel technology to achieve a Super-hydrophobic coating with microscopic roughness on copper surface. First, make a layer of verdigris grow on the fresh pure copper surface. Gain it by exposing the copper to air and the mist of acetic acid solution. The green coating is a mixture of basic copper（II） carbonate and copper（II） acetate. Second heat the coating and make it decompose to CuO. Lastly, form an n-octadecanethiol self-assembled monolayers coating on the outermost surface. Contact angle test, scanning electron microscope analysis and electrochemical testing were carded out to characterize the surface, and a heat transfer experiment for dropwise condensation of steam was performed also. Results show that the modified surface bears a few Super-hydrophobic features, the static contact angle is higher than that in literatures, reaching 153.1±1.7°. The microscopic roughness can be seen in SEM images, differing much from H2O2 etched surface and bare copper surface. The condensation of steam on the surface is a typical form of dropwise condensation, in the measured range of temperature difference, under 0.1 MPa, the average convection heat transfer coefficients of the vertical surface are 1.7-2.1 times for those of film condensation. At the same time, the inhibition efficiency of surface is improved to some extent comparing with the same kind of SAMs, which suggests that the lifetime of maintenance dropwise condensation would have the possibility to surpass the existing record.

关键词： dropwise condensation Self-assembled monolayers Microscopic roughness Super-hydrophobic surface Heat transfer coefficient

dropwise condensation heat transfer enhancement on surfaces micro/nano structured by a two-step electrodeposition process

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Journal of Central South University 2019年第5期26卷 1065-1076页

作者： Hamid Reza TALESH BAHRAMI Alireza AZIZI Hamid SAFFARI School of Mechanical Engineering Iran University of Science and Technology

condensation is an important regime of heat transfer which has wide applications in different industries such as power plants,heating,ventilating and air conditioning,and *** occurs in two different modes including filmwise (FWC) and dropwise (DWC) *** occurring on hydrophobic and superhydrophobic surfaces has a much higher heat transfer capacity than ***,wide investigations have been done to produce DWC in recent *** surfaces have micro/nano structures with low surface *** this study,a two-step electrodeposition process is used to produce micro/nano structures on copper *** surface energy of specimens is reduced by a self-assembled monolayer using ethanol and 1-octadecanethiol *** results show that there is an optimum condition for electrodeposition *** example,a surface prepared by 2000 s step time has 5 times greater heat transfer than FWC while a surface with 4000 s step time has nearly the same heat transfer as *** surfaces of the fabricated specimens are examined using XRD and SEM *** SEM analyses of the surfaces show that there are some micro-structures on the surfaces and the surface porosities are reduced by increasing the second step electrodeposition time.

关键词： dropwise condensation heat transfer electrodeposition micro/nano structure porosity

Dip-coating of Superhydrophobic Surface on Irregular Substrates for dropwise condensation

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Journal of Bionic Engineering 2021年第2期18卷 387-397页

作者： Zhen Xiao Da Xu Wenwen Zhang Xinquan Yu Youfa Zhang Jiangsu Key Laboratory of Advanced Metallic Materials School of Materials Science and EngineeringSoutheast UniversityNanjing 211189China

Herein,self-assembled superhydrophobic composite coatings were successfully prepared using a one-step dip-coating method on different irregular *** fluorinated nano-SiO_(2) particles spread into a uniform layer owing to the viscosity of the composite *** the optimization of the process,the fabricated nanoporous-structured coating has low adhesion properties with chemical and high thermal *** baking at 250℃ for 2 h or soaking in a solution of pH=1 or pH=13 for 10 days,the coating could maintain its good *** self-ejecting effects of the condensed dewdrops and droplet bounce phenomenon indicate that the coatings can be well-distributed on components of different structures,and they have significant application prospects in irregular parts and industrial production in the near future.

关键词： superhydrophobic dip-coating self-assembled dropwise condensation irregular parts

dropwise condensation on a Rotating Condenser in Relation to Heat Transfer Intensification

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Journal of Environmental Science and Engineering 2010年第6期4卷 50-54页

作者： M.K. El-Adawi T.H. Felemban Physics Department Faculty of Science for Girls King Faisal University Dammam 31113 Saudi Arabic

A design of a rotating condenser is suggested. The maximum radius under the effect of rotation is estimated analytically .It is found that it decreases with the angular velocity. This in turn increases the rate of sweeping the surface by departing droplets. The appearance of droplets with smaller radii will be predominant. These small droplets offer small thermal resistances, thus enhancing heat transfer through the condenser surface. It is found also that the maximum radius is a function of the distance from the axis of the rotating condenser. Thus the value of the maximum radius under rotation is not unique. This in turn makes the heat flux through the condenser surface not to be uniform.

关键词： dropwise condensation dropwise rotating condenser heat transfer

EXPERIMENTAL STUDY OF condensation HEAT TRANSFER CHA- RACTERISTICS OF HORIZONTAL TUBE BUNDLES IN VACUUM STATES

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Journal of Hydrodynamics 2012年第4期24卷 628-634页

作者： CHENG Shen SUN Feng-zhong SHI Yue-tao School of Energy Source and Power Engineering Shandong UniversityJinan 250061China

TO develop an excellent heat transfer element under the vacuum condition, experiments about the heat transfer performance of horizontal tube bundles of different materials under various vacuum conditions were carried out, including the stainless steel tube, the brass tube, the Ni-based implanted steel tube and the ion implanted brass tube. The relative trends show that the condensation heat transfer coefficient and the overall heat transfer coefficient of bundles of four materials all increase with the vacuum degree, especially, those of the Ni-based implanted steel tube and the ion implanted brass tube. Under a high vacuum condition （0.07 MPa）, the condensation heat transfer coefficient of the Ni-based implanted steel tube bundle is about 1.4 times of that of the stainless steel tube bundle, the condensation heat transfer coefficient of the ion implanted brass tube bundle is found to be about 1.3 times of that of the common brass tube bundle. Therefore, according to the condensation heat transfer characteristics studied under high vacuum conditions, it is believed that a dropwise condensation is partly achieved on the surface of these two implanted tube bundles, and the ion implantation is shown to be an effective method to achieve the dropwise condensation. Based on this study, it is believed that the Ni-based steel tube may replace the brass tube, which is more expensive as a heat transfer component.

关键词： vacuum heat transfer characteristics condensation heat transfer coefficient dropwise condensation