Molecular dynamics simulations of the thermal conductivity enhancement of a propylene glycol nanofluid coolant

In this paper, the effects of adding nanoparticles on the heat transfer and microstructure of propylene glycol coolant were simulated by molecular dynamics method. The findings indicate a positive correlation between the water content of the system and the thermal conductivity of the propylene glycol–water coolant. After adding Au nanoparticles, the thermal conductivity of the coolant increased at all concentrations, with the maximum increase of 15.1 %. The adsorption layer on the surface of nanoparticles is the internal factor for improving the heat transfer performance of nanofluids. The adsorption layer on the surface of nanoparticles with different concentrations is layered, with the inner layer consisting of propylene glycol molecules and the outer layer consisting of a mixture of propylene glycol and water molecules. The maximum molecular water density is near r = 1.8 nm. The thermal conductivity of this nanofluid was positively correlated with the thermal conductivity of nanomaterial in the order of Cu > Au > Fe. Nanoparticles mainly affect the molecular number density distribution of the base liquid in the adsorption layer near the surface of particles. The higher the molecular number density of the base liquid in the adsorption layer, the higher the thermal conductivity of the nanofluid.