| Micro/nano scale structure on metal solid surface is widely used in improving wettability of solid surface, drag reduction for flow, billing heat transfer rate in microscale and slip flow et, which shows a good development. The development of the mechanism, which is about the effect of micro/nano scale structure on heat and mass transfer, will be able to solve the problems which includes excessive flow resistance and high heat flux cooling in such small space. The superhydrophobic surface, which is composed with micro/nano structures shows unique hydrophobic and flow drag reduction performance, is widely used in engineering. At the same time, the abnormal physical phenomena on fluid flow and heat mass transfer due to size effect is also being paid attention with the development of MEMS/NEMS. In addition, the effect of micro/nano structure on heat mass transfer is investigated by molecular dynamics simulation from the perspective of molecular; this will explain its mechanism in nature. In this paper, we propose a method to obtain superhydrophobic surface for copper material. Then this superhydrophobic surface is used in microchannel to study the effect of superhydrophobic surface on flow drag reduction. Furthermore, we experimentally study the effect of nanostructure on heat transfer. Final, the mechanism of nanostructure on heat and mass transfer is explained by molecule dynamic simulation. The main contents of this thesis include:(1) Fabrication of superhydrophobic on metal surfaceWe propose a nove processing method, which aims to form a dual rough microstructure on a copper plate. The surface is fabricate using a laser electrodeposited composite method. The structure and chemical component on solid surface is characterization by SEM and EDS. At the same time, the wettability is measured by static contact angle and rolling angle.In addition, the forming mechanism of structure parameters on superhydrophobic surface is analyzed.(2) The effect of superhydrophobic on friction reductionBy following this fabrication method, microchannels with superhydrophobic surface is obtained. And the characteristics of friction reduction on these microchannels is investigated. The pressure drop values on these microchannels is recorded; this provide detail information to investigate the effect of microstructure parameters on friction reduction.(3) The effect of nanostructure and interface on wettability by molecular dynamic simulationBased on the MD simulation method, the smooth and rough surface for metal material is created by the software named Simulation Box. The distribution of water molecules on different solid surfaces is obtained by LAMMPS. And these solid surface with different surface energy are formed by changing the parameters of solid-liquid potential function.(4) The effect of nanostructure on rapid boiling of water on a hot metal plateBased on open source LAMMPS with certain extension, square and cone shaped nanostructures are created on copper and aluminum surfaces, respectively. The simulation results show the dynamic behavior of water film during rapid boiling. And calculate the liquid boiling rate on different size structure surface. In addition, experimentally analyze the effect of nanostructure on boiling.(5) The effect of nanostructure on fluid flow and heat and mass transferBased on Couette type flow, a more physically-sound method which intent to control temperature and velocity simultaneously is applied to the same atoms through the entire MD simulation. And the implemented schemes is validated by velocity and temperature profile of the flow along the vertical direction. And the convective heat transfer coefficient between fluid flow and two parallel copper plated is estimated. In addition, according the previous work, the effect of nanostructure on fluid flow is also studied. |
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