The Study Of Nanochannel On Water Transport Performance

China is the world’s third-largest frozen soil country.The frozen soil area accounts for about 21.5%of the country’s land area,reaching 1.4 million km~2.The production of frozen soil is mainly due to the hydrogen bond interaction between water molecules,which causes the water to expand and contract during solidification,causing serious harm to the safety of various buildings on the soil.Traditional models cannot accurately describe the process of water migration,and the research on its microscopic interpretation is still very limited.Nanoconfined fluids compares with bulk water,exhibiting distinctive nanoscale effects and having many important characteristics in material and energy transportation.It has broad application prospects in Energy storage,material transportation,desalination,filtration,etc.Molecular dynamics is widely used to study nanoconfined fluids in low-dimensional materials such as graphene and carbon nanotubes.In this paper,molecular dynamics are used to study the transport laws and properties of water in carbon nanotubes of different shapes.The main results are as follows:(1)The friction coefficient of water transport in circular carbon nanotubes with radius of0.5 nm,0.7 nm,1.0 nm,and 1.5 nm is studied.Compared with the previous literature,the friction coefficient of carbon nanotubes increases with the radius increases.There is layered water in the carbon nanotubes with a radius of 0.5 nm,which is one of the reasons for the small friction coefficient of the carbon nanotubes under this radius.Through the study of the two-dimensional density distribution,the axial distribution function and the dipole distribution of the first layer of water molecules,it is found that In the process of water transport,the change of water clusters structure is the main reason to affect the efficiency of transportation,and its structural characteristics will change significantly with the increase of the radius.After analyzing the influence of the compression deformation of the circular carbon nanotubes on the water transport,the linear relationship between the compression deformation and the solid-liquid friction is summarized.(2)Carbon nanotubes whose shape are triangles,squares,hexagons,octagon and graphene layers were constructed with radius of 0.5 nm,0.7 nm,1.0 nm,and 1.5 nm.The results indicate that the solid-liquid interface friction of carbon nanotubes increases with the radius.Polygonal carbon nanotube friction coefficient combined the properties between the circular carbon nanotubes and the graphene layers:when radius less than 1.0 nm,the friction coefficient with the radius.Under the same radius,the closer to the circle,the smaller the friction coefficient.However,when radius is greater than 1.0 nm,the friction coefficient does not change with the radius.By analyzing the physical mechanisms of the two-dimensional density distribution,the potential energy distribution on the wall,the axial distribution function and the dipole distribution of the first layer of water molecules,it is found that the changes in the potential energy distribution and the changes in the water structure are the main factors affecting the friction at the solid-liquid interface.