Molecular study on the role of solid/liquid interface in specific heat capacity of thin nanofluid film with different configurations

Abstract

Nanoconfined liquids may have significantly different properties from their bulks. This can be prominent for nanofluids due to the interaction between nanoparticles and solid/liquid interface, which is studied under different configurations (including confined, sessile, and freestanding forms) in the present work by calculating a typical thermophysical property (the specific heat capacity) using the molecular dynamics simulation method. It is found that the copper-water nanofluid film has a relatively higher specific heat capacity than the water film with the same thickness; and the specific heat capacity is closely related to the configuration: the confined nanofluid film has the highest value, followed by the sessile and freestanding nanofluid films. The reason behind this is explored in terms of interface effects: the influence of nanoparticles on the interface energy and hence specific heat capacity is weaker than the plate which has adjacent liquid molecules with highly impacted molecular structure; and compared to the symmetrical density distributions in confined and freestanding films, the asymmetry in the sessile film causes changes of the interfacial parameters including mean square displacement, radial distribution function, and vibration density of state of water molecules. Thus, this work provides insight into the variation of thermophysical properties for nanofluids with various forms of nanoconfinement or configurations in applications such as distillation, evaporation, and interface separation.