Molecular Dynamics Simulations on Heat Transport of Nanoconfined Water under Electric Fields: Effect of Nanochannel Size.

Abstract

When water is confined in a nanochannel, its thermodynamic and kinetic properties change dramatically compared to the macroscale. To investigate these phenomena, we conducted nonequilibrium molecular dynamics simulations on the heat transfer in copper-water nanochannels with lengths ranging from 12 to 20 nm in the absence and presence of an electric field. The results indicate that in the absence of an electric field (L_z = 12-20 nm), the binding force between water molecules in the 20 nm nanochannel is the weakest, facilitating thermal motion in the liquid phase. When compared to the 12 nm nanochannel, the enhancement rate of the thermal conductivity is 19.53%. In the presence of a uniform electric field in the positive z-direction (L_z = 12-16 nm), water molecules in the 16 nm nanochannel are more readily frozen into ice crystal structures. This change in the mode of heat transfer shifts from the thermal diffusion of water molecules to the vibrations between copper atoms and the ice crystal, resulting in a significant increase in the thermal conductivity of water.