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• Influence mechanism of solid–liquid interaction is revealed via molecular dynamics. • The relationship between Nusselt number and temperature jump length is determined. • The relationship between fRe and normalized slip length is proposed. • Solid-liquid interaction improves overall heat transfer within a certain range. • The present work provides a new insight for the effect of solid–liquid interaction. Nanochannel cooling technology is widely used in the heat dissipation systems of various micro/nanoscale electronic devices or components. The consideration of resistance loss and the optimization of heat dissipation are of great significance for the widespread application of nanochannel cooling technology. A model of convective heat transfer in nanochannel with constant wall temperature is established with molecular dynamics method. The effects of solid–liquid interaction on flow and heat transfer characteristics are investigated. The microscopic mechanisms of the solid–liquid interaction influencing heat transfer performance and flow resistance of nanochannel are explored from the atomic level. The results show that the enhancement of the solid–liquid interaction leads to the increases of the coupling degree of vibration frequency between wall and liquid atoms and the orderliness of microstructure of first fluid layer, and finally facilitates heat transfer between nanochannel wall and liquid. The Nusselt number in nanochannel is not a constant and decays exponentially with the increase of temperature jump length. Meanwhile, as the solid–liquid interaction increases, the slip length decreases and the friction factor increases, which are attributed to the augment of the static structure factor, resulting in more fluid atoms in near-wall region are firmly locked by the wall. The friction factor in nanochannel not only depends on the Reynolds number, but also is closely related to the slip length. To further evaluate overall heat transfer performance of the nanochannel that considers flow resistance, the comprehensive performance coefficient is discussed. It's found that the solid–liquid interaction is effective in improving the overall heat transfer performance of the nanochannel within a certain range. [ABSTRACT FROM AUTHOR]

The effect of solid wall properties on the convective heat transfer characteristic in a three-dimensional nanochannel is probed with molecular dynamics simulation. The interfacial velocity slip and temperature jump are treated as the function of the interatomic interaction, the atomic mass and thickness, respectively. The result shows that the wall properties, including interatomic interaction among wall atoms, atomic mass, as well as coating thickness based on certain interatomic interaction and atomic mass, will lead to significant changes in the temperature jump. These effects are caused by the variations of coupling degree of solid-liquid vibration frequency induced by the mismatch between solid wall and fluid atoms. Furthermore, temperature jump is also related to the solid-liquid interaction while the velocity slip is only related to the solid-liquid interaction. It's found that both the decrease of interatomic interaction and the increase of atomic mass can further enhance the heat transfer. That is, the interatomic interaction among wall atoms is closer to that among fluid atoms, the atomic mass of wall atoms is much greater than that of the fluid atoms, and the convective heat transfer in the channel is better. However, the variation of Nusselt number with coating thickness is notably, which exhibits a peak value in the hydrophilic and hydrophobic cases. It's indicated that vibrational density of states (VDOS) corresponding to a selected coating wall properties (including interatomic interaction, atomic mass and thickness) lies in between the VDOS of the channel wall atoms and that of fluid atoms, can play a role of thermal bridge between wall and fluid atoms and lead to a remarkable increase of heat transfer. Based on the selected solid wall properties, a reasonable selection of wall-fluid interaction can effectively increase velocity slip and achieve drag reduction. • The variations of wall properties lead to significant changes in temperature jump. • Temperature jump is affected by coupling degree of wall-fluid vibration frequency. • Convective heat transfer varies notably with interatomic interaction and thickness. • A selected coating wall will enhance the heat transfer performance. • Wall properties and wall-fluid interaction are important for heat transfer. [ABSTRACT FROM AUTHOR]

The flow of argon liquid in an asymmetric nanochannel with smooth and rough wall is investigated by molecular dynamics method. Considering the relationships of related factors which include characteristic dimensions, the number and the dense arrangement pattern of nanostructure, the effects of surface topography on fluid flow and interface slip are probed. The results show that the variation of the surface topography height has a significant influence on the fluid flow and interface slip. However, the effect of the variation of topography width is greatly related to the number and dense arrangement pattern of nanostructure. Surface topography causes an increase in interfacial resistance and more reduction in velocity slip at the rough wall, which even results in the forming of sticky boundary condition. The effect of non-uniform interface wettability of rough wall on the flow behavior and slip at the solid–liquid interface is investigated as well. The results show that the influence of non-uniform interface wettability on the flow in the hydrophobic channel is more obvious than that in the hydrophilic channel. Hydrophobic substrate with hydrophobic nanostructures has a smaller interfacial hydrodynamic resistance than that with hydrophilic nanostructures, which makes the average velocity and velocity slip become greater. Obviously, non-uniform interfacial wettability strengthens the effect of surface topography on the fluid flow and interface slip. It is possible to achieve effective velocity slip and obtain drag reduction by applying the non-uniform wettability of nanostructures under the same surface topography. • The characteristic dimensions of nanostructure are normalized. • The effect of surface topography on fluid flow and slip is obtained. • The impact of non-uniform interface wettability on the slip is probed. • Non-uniform interface wettability strengthens the effect of surface topography. [ABSTRACT FROM AUTHOR]