Numerical And Theoretical Investigations On Effects Of Nanolayer On Solid-liquid Interfacial Thermal Resistance

With rapid advances in nanotechnology,the size of Micro-Electro-Mechanical Systems becomes smaller and smaller.In such microsystems,the surface effects cannot be ignored and solid-liquid thermal boundary resistance plays an important role on heat transfer process across solid-liquid interface.In the previous study,however,the link role of liquid adsorption layer between solid and liquid have been ignored.In this paper,the critical role of liquid adsorption layer on solid-liquid interface thermal resistance is studied by molecular dynamics simulation and theoretical method.The MD simulation results showed that:(i)A nanolayer of liquid atom forms on the surface of solid wall spontaneously.The nanolayer can exchange heat and atoms with bulk liquid,but can only exchange heat with solid wall.In consequence,solid-liquid interface thermal resistance consists of two parts:(?)thermal resistance between solid wall and nanolayer and(?)the thermal resistance between nanolayer and bulk liquid.As the solid surface becomes more hydrophilic,the former part reduces,while the second part increases and leads a minimum value of thermal boundary resistance.The longitudinal mode of vibrational density of states(VDOS)of nanolayer moves to higher frequency area with the surface hydrophilicity enhancing,which is one of the causes of this phenomenon.(ii)With the separation distance of two solid walls becoming larger,the thermal boundary resistance increases at first and then approach a constant value asymptotically.The change of heat flux has little effect on solid liquid interface thermal resistance.Nanolayer atomic vibration frequency model and atomic number model are established theoretically,based on which,the atom exchange model of nanolayer and the bulk liquid are built then.The predicted values and the simulation results fit well.The reason why atomic exchange heat transfer process is limited is explained quantitatively.And this model predicted the different behavior of the two nanolayers close to heat source and heat sink separately successfully.