Why can hybrid nanofluid improve thermal conductivity more? A molecular dynamics simulation

Abstract

It has been widely recognized that the addition of nanoparticles to a base fluid can significantly enhance the thermal conductivity of nanofluids. However, the underlying mechanism is unclear, especially for hybrid nanofluids with nanoparticles composed of two or more materials. This is the first exploration of the microscopic mechanism responsible for the enhancement in the thermal conductivity of hybrid nanofluids. Firstly, the thermal conductivity and diffusion coefficient of Cu-Ag/Ar hybrid nanofluid were estimated by molecular dynamics. The results indicate that the maximum improvement in thermal conductivity of 69.72% can be achieved for a hybrid nanofluid with Cu-Ag 50% /Ar compared to liquid Ar, which is much larger than the 47.95% and 26.4% achieved for Ag/Ar and Cu/Ar nanofluids. Then, the radial distribution function demonstrates that the Ar atoms on the nanoparticle surface are in dynamical equilibrium. Finally, the nanolayer densities and diffusion coefficients are calculated for various hybrid nanofluids to explain the underlying mechanism of the enhancement in the thermal conductivity. The consistency of the thermal conductivity with the nanolayer density and diffusion coefficient indicates that nanolayer structure and diffusion of Ar are the two underneath mechanisms.