A Molecular Analysis of Critical Factors for Interface and Size Effects on Heat Conduction in Nanoconfined Water Film

Heat conduction of nanoconfined liquid may differ from its bulk because of the effects of size,geometry,interface,temperature,etc.In this study,the roles of some critical factors for the heat conduction of nanoconfined water film are systematically analyzed by using the molecular dynamics method.With decreasing thickness,the normal thermal conductivity of nanoconfined water film between two copper plates decreases exponentially,while the thermal resistance,peak of the radial distribution function,and atomistic heat path increase exponentially.The average bond order,radial distribution function,mean squared displacement,and vibrational density of states are calculated to analyze the effects of structure,distribution,molecular diffusion,and vibration of water molecules on heat conduction especially in a region having no oxygen atoms(which is observed by the near-wall density profile).The results show that phonon scattering is dominant for determining the reduced thermal conductivity in this near-wall region.The thermal conductivity ratio of confined water film to bulk water has a roughly linear relationship with the logarithm of the proportion of the near-wall region.Moreover,the high interfacial thermal resistance is positively correlated to the film thickness,but it has a negligible impact on heat conduction.This work provides insights into the contribution of water molecules near the solid/liquid interface to the heat conduction of nanoconfined liquid for process intensification.