Diffusion behavior of water molecules in binary mixed vegetable oils under the synergistic effect of temperature and nano-TiO2

Abstract

Temperature and water are two important factors affecting the insulating properties of power insulating oil. Meanwhile, nanoparticles have received attention from researchers as the latest improvement method for the electrical performance and insulation properties of insulating oil. Therefore, in this study, we constructed models of pure binary mixed vegetable insulating oils and mixed insulating oils modified with nano-TiO2. The diffusion behaviour of water in the binary mixed vegetable insulating oil under the synergistic effect of temperature and nanoparticles was investigated. Results indicate that the diffusion coefficient of water molecules in the nano-TiO2 modified vegetable insulating oil decreased up to 30.7 % compared to the unmodified vegetable insulating oil. With the introduction of nanoparticles, the free volume of the oil model is reduced by 18.23 % on average, and the space for water molecules to move is greatly reduced. The average interaction energy of oil and water molecules decreased by 9.53 %, and a large number of water molecules formed hydrogen bonds with O atoms on the nanoparticles. The nano-TiO2 particles have a negative electrostatic potential distributed on the surface and have a strong electrostatic attraction to the free H3O+ in the oil. Compared with pure oil, water molecules in modified oil need higher temperature and higher kinetic energy to get rid of hydrogen bond with nanoparticles. Therefore, the introduction of nanoparticles has largely reduced the influence of temperature on the diffusion of water molecules.