Research On Affected Mechanism Of Surface Characteristics To Convective Heat Transfer In Nanoconfined Spaces

The increasing energy demand has brought huge environmental challenges to the world,and sustainable development strategies for efficient energy utilization have become a hot issue in recent years.Due to the booming development of micro/nano electronics,the integration of electronic components has been increasing,the characteristic scale is dramatically reduced,and the requirements for thermal environments are more demanding.The heat dissipation problem of micro/nano electronic components has become an important factor limiting its development,and a variety of heat dissipation strategies proposed subsequently have attracted much attention,and the micro/nano channel cooling technology with high performance and economic applicability shows advantages from a variety of heat dissipation strategies.However,the Knudsen number of the flow heat transfer system at the micro/nano scale is so large,the continuous medium assumption cannot be applied,but the scale effect and interfacial heat transfer mechanism still need to be studied in depth,therefore,it is important to investigate the flow characteristics and heat transfer mechanism at the nanoscale the development of micro/nano channel cooling technology.The flow heat transfer process in the confined nanoscale space is a non-equilibrium kinetic process influenced by multiple factors.In this paper,based on the molecular dynamics simulation method,the corresponding study is carried out for the mechanism of the influence of surface properties such as interfacial wettability,rough nanostructure,and the coupling effect of interfacial wettability and rough nanostructure on the flow heat transfer in the confined nanoscale space.First,the affected mechanism of different interfacial wettability on convective heat transfer in the nanochannels was investigated.A model of nanochannels with different hydrophilic surfaces was constructed and the affected mechanism of the change of interfacial wettability on the flow heat transfer in the nanochannels was investigated.The results show that the temperature field development improved significantly with the increase of the interfacial hydrophilicity of the nanochannels,and the temperature jump phenomenon and velocity slip phenomenon were observed at the solid-liquid interface,both of them were also influenced by the interfacial wettability,and the temperature jump length and velocity slip length were smaller in the nanochannels with better interfacial hydrophilicity.Microscopically,the distribution of mass density and potential energy in the nanochannels with different interfacial wettability were analyzed,and it was found that the nanochannels with better hydrophilicity have larger mass density areas and lower potential energy areas at the interface.Secondly,the mechanism of the effect of sinusoidal ordered surface rough structure on convective heat transfer in the nanochannel was investigated.Sinusoidal ordered rough structure nanochannels with different surface characteristic parameters were constructed,and the mechanism of the effect of period and amplitude on convective heat transfer in the nanochannels was investigated.The results show that with the increase of amplitude and decrease of the period,the temperature field develops better,the mainstream velocity is suppressed,and there are obvious temperature jump phenomenon and velocity slip phenomenon at the interface of the nanochannel,the slip length in the entrance stage of the channel is generally larger than the fully developed section,the slip length is affected by the rough structure of the surface,and the slip length at the depression of the rough structure is significantly larger than that at the projection.By analyzing the mass density distribution and potential energy distribution of the nanochannel and their quantitative statistics,it is found that the expansion of the area of the high mass density region and low potential energyregion at the nanochannel interface is the microscopic mechanism of heat transfer enhancement,and by analyzing the Nusselt number,it is found that the convective heat transfer in the nanochannel is enhanced with the increase of the amplitude and decrease of the period of the surface rough structure.Thirdly,to reconstruct the surface topological morphological features more closely to the actual,a more realistic complex rough surface topology is constructed,and the mechanism of the disturbance effect of the complex surface rough structure on the flow and heat transfer in the nanochannel was also investigated.The results show that with the increase of the functionally regulated parameters,the roughness of the surface structure increases,fluid perturbation,as well as secondary delamination phenomena,can be observed,the temperature field develops more fully,the temperature of the mainstream region increases,and the temperature step length and velocity slip length is smaller.Microscopically,the heat transfer rate of argon atoms increases,the atomic velocity of argon atoms decreases,and the drag coefficient increases.By counting the number of atoms in the mass density region and the potential energy sum in the potential energy region,it is found that more atoms involved in heat transfer are gathered at the interface,a secondary stratification phenomenon occurs,the interaction energy at the interface also increases significantly,the Nusselt number increases with the increase of the function modulation parameter,and the convective heat transfer in the nanochannel is enhanced.Finally,based on the above study of the influence mechanism of rough structure and wettability,progressively hydrophilic wetting surfaces and progressively subdivided rough structures are constructed and modeled synthetically to investigate the influence mechanism of their coupling effects on heat transfer and flow in the nanochannel.The results show that both the progressively hydrophilic wetting surface and the progressively subdivided rough structure significantly promote the full development of the temperature field,and correspondingly the temperature jump length is significantly reduced and the Nusselt number is significantly increased.The nonsynergistic effect of both on the hindrance of velocity field development is analyzed.When the wettability ratio parameter exceeds 1.0,the hindrance of the wettable surface on the velocity field becomes small,but its promotion of the temperature field is still significant,and the velocity slip length and flow resistance coefficient show consistent changes with it.By analyzing the mass density distribution and potential energy distribution at the interface,it is found that the area in the nanochannel with better heat transfer has a more significant expansion,and the interaction energy between the wall atoms and the fluid atoms increases significantly.