Molecular Dynamics Study Of Fluid Flow And Nucleation Heat Transfer In Microchannels

In recent years,the development of science and technology has made micro-nano science and technology more and more widely used in various research fields such as micro-electromechanical systems,biopharmaceuticals,and industrial engineering.However,because micro-nano science and technology are at the nanometer and micrometer scale,There are some difficulties in experimental research and numerical simulation.So the research on micro-nano scale is still in the development stage.In this paper,molecular dynamics simulation software LAMMPS was used to study the fluid flow characteristics and fluid nucleation heat transfer in micro and nano channels.In this paper,the influence of nanoparticles in micro-nano channels on the flow characteristics of fluid Couette is firstly studied,and the velocity,density and interface slip of the fluid are analyzed after adding nanoparticles.The results showed that: with the increase of the volume fraction of nanoparticles,the fluid number density in the near wall area presented a attenuation oscillation distribution,and the amplitude from the near wall area to the main flow area gradually decreased.The fluid shear strain rate gradually decreased with the increase of the volume fraction of nanoparticles,and the slip velocity and slip length gradually increased.When different numbers of nanoparticles with the same volume fraction are added,there is no corresponding change in the fluid flow in the channel,but when the number of nanoparticles is 3,the fluid shear strain rate is maximum,and the slip velocity and slip length are the minimum.When the shear velocity of the solid wall is changed,the slip velocity and slip length of the fluid increase gradually with the increase of the shear velocity of the wall,but the increase of slip length is relatively small.Secondly,the effect of wall wettability on fluid nucleation and nucleation mechanism was studied.The results show that: when the wettability of the wall surface is strong,the interaction force between the wall surface and the fluid particles is large,the fluid will form a "quasi-solid" layer near the wall surface,and the heat will be transferred to the fluid in the channel through the "quasi-solid" layer.When the wall wettability is relatively weak,the interaction force between the fluid and the wall particles is relatively small,and no "solid-like" layer is formed near the wall surface.The heat is directly transferred from the solid wall surface to the fluid in the channel.The heat transfer effect is normal,and the liquid will Heterogeneous nucleation occurs at the wall surface,and the growth rate of bubble nucleation is slow.When the wall wettability is the weakest,there is a large repulsive force between the solid wall surface and the fluid particles.A gas film layer will be formed near the wall surface,and the heat is transferred to the fluid through the gas film layer.The heat transfer effect is poor,and the fluid in the channel Nucleation is difficult to occur.In addition,the initial density of the fluid in the channel has a certain influence on the growth of nucleation bubbles.The higher the initial density of the fluid is,the better the heat transfer will be,but the larger the initial density of the liquid is,the smaller the bubble area generated by nucleation in the channel will be.