Revealing the thermal conductivity and viscosity mechanism of lubricating oil enhanced with nano-silicon carbide using molecular dynamics simulation

Abstract

Enhancing the heat transfer capability and understanding the rheological properties of automotive lubricants are essential for improving engine performance and durability. This study investigated the important parameters influencing the above-mentioned performance, namely the thermal conductivity and dynamic viscosity of the nanofluid (NF) based on poly-α-olefin (PAO6) and nano-silicon carbide (SiC) via experiments and molecular dynamics (MD) simulations. The fascinating novelty of this approach lies in exploring the effects of the coating layer formed on nano-SiC within the lubricant interface, as well as its influence on viscosity and the mechanisms that facilitate enhanced heat conduction between lubricant layers. The experiment and MD simulation revealed that NF exhibited shear thinning behavior and the dynamic viscosity values of SiC NF from 20 °C to 60 °C were exponentially reduced. Moreover, the thermal conductivity of NF is improved by 4.7 % and 10.5 % than that of base oils for experiemnt and simulation outcomes, which were influenced by temperatures and nano-SiC concentrations. The distribution diagram of the atom radial distribution function (RDF), based on the structural and interactional data at the molecular level, indicates that the presence of nano-SiC transforms the microstructure from a liquid phase to a nanolaminar solid state. This alteration increases the orderliness of the NF molecules and facilitates more efficient energy exchange, thereby improving their thermal conductivity and viscosity. Finally, this study assists the design of NF in accordance with specified operating requirements.