Molecular dynamics and Brownian dynamics-based studies on interfacial heat conduction from a heat source to a nanofluid for estimating the enhancement in thermal conductivity of the nanofluid

Abstract

This work reports estimation of conductive heat transfer through the interfacial layer of water-based Ag nanofluid in contact with a heat source. The presence of nanoparticles in the nanofluid leads to Brownian motion and eventual collision of the nanoparticles with the heat source. The colliding nanoparticles extract some heat from the heat source during the period of collision in conduction mode. This heat transfer is an addition to the usual temperature gradient-induced conductive heat transfer through the thermal boundary layer of the base fluid itself. This gives rise to enhancement in thermal conductivity of the nanofluid. Considering this mechanism of heat transfer at the interfacial layer of the nanofluid in contact with a heat source, a multiscale model has been developed here looking at two parallel ways of heat conduction at the interfacial layer. The collision of nanoparticles with the heat source and the associated conductive heat transfer have been investigated by means of MD simulations. On the other hand, the Brownian motion of nanoparticles within the base fluid and heat exchange between the nanoparticles and adjacent base fluid in micro-convection mode have been studied by Brownian dynamics and associated micro-convection model. The resultant enhancement in thermal conductivity of the nanofluids has been estimated by the multiscale model as formulated here. The predicted enhancement in thermal conductivity and its variation with Ag nanoparticles loading in water are in well agreement with experimental data, and hence, the present multiscale model can be used for designing nanofluids for targeted applications.