Thermal Transport Dynamics in Active Heat Transfer Fluids

We present results of molecular dynamics (MD) calculations of the effective thermal conductivity of nanofluids containing self-propelled nanoparticles. The translational and rotational dynamics observed in the simulations follow the behavior expected from the standard theoretical analysis of Brownian and self-propelled nanoparticles. The superposition of self-propulsion and rotational Brownian motion causes the behavior of the self-propelled nanoparticles to resemble Brownian diffusion at long times, with an effective coefficient that is larger than the standard Brownian value by a factor of several thousand. As a result of the enhanced diffusion (and the enhanced convective mixing resulting from the motion), we observe a discriminable increase of the effective thermal conductivity of the solution. While the increases we observe are in the range of several percent, they are significant considering that, without propulsion, the nanofluid thermal conductivity is essentially the same as that of the base fluid. Our results constitute a proof of concept that self-propelled particles have the potential to enhance thermal conductivity of the liquid in which they are immersed, an idea that could ultimately be implemented in a broad variety of cooling applications.