Effect of temperature and nanoparticle size on the interfacial layer thickness of TiO2–water nanofluids using molecular dynamics

In the design and optimization of nanofluids, it is crucial to investigate and characterize the thermal conductivity enhancement mechanisms and their influencing factors. Although the effect of the “liquid film” on the thermal conductivity of the solid–liquid interface in nanofluids has been extensively studied, most of the research in this area has examined metal–water nanofluids or Ar-based nanofluids. In this work, non-equilibrium molecular dynamics is utilized to explore the mechanism of thermal conductivity enhancement in TiO2–water nanofluids. It is noted that a distinct interfacial layer is formed within 5 Å from the nanoparticle surface. As the nanoparticle size increases, the number density also increases, resulting in a corresponding increase in the thermal conductivity. Moreover, adding 1% TiO2 nanoparticles to water leads to an increase in thermal conductivity of 1.5–3%. Notably, the interfacial layer thickness remains relatively constant with the change in temperature. The Materials Studio analysis results indicated that the water molecule will have stable chemisorption on the titanium dioxide surface with an adsorption energy of approximately −0.96 eV. The findings of this study offer new insights and useful information to support the selection of nanomaterials for the preparation of convective systems.