Thermophoresis of nanoparticles in liquids

Abstract

Thermophoresis is the movement of particles in a fluid subjected to a steady temperature gradient, where the fluid molecules at the hotter region possessing higher kinetic energy drive the particles towards the colder region. This paper presents a molecular dynamics simulation to obtain the effects of the particle shape, size and orientation on thermophoresis in nanofluids. Two allotropes of carbon, namely Carbon Nanotubes (CNT) and fullerene, and copper nanoparticles have been studied, with liquid argon and water as the base fluids. It was found that the thermophoretic force in fullerene particles of comparable size is more than that in CNT. It was also seen that the particle orientation and size have an effect on the thermophoretic force, and that the force decreases with an increase in the particle size. The effect of the base fluids, namely liquid argon and water, on the thermophoretic force was also studied, and a comparison was performed using the thermophoretic coefficient. The simulation results show that the thermophoretic force is proportional to the kinematic viscosity of the fluid and the imposed temperature gradient, and the increase is found to be linear. The results also indicate that the thermophoretic force depends on the particle orientation, and the analysis provides a starting point for further studies to explain the functional dependence of the particle orientation on the thermophoretic force.