Simulation of the diffusion behavior of water molecules in palm oil and mineral oil at different temperatures

The presence of moisture accelerates the aging of oil-paper insulation systems and reduces the insulating performance. In this study, the molecular dynamics method was used to investigate the diffusion behavior of water molecules in palm oil and compared with the diffusion behavior of water molecules in mineral oil. The mineral oil-water mixture model and vegetable oil-water mixture model were established; then, molecular dynamics calculations were performed on the established models from 323 K to 363 K. The free volume, diffusion coefficient, number of hydrogen bonds and interaction energy were analyzed. The results showed that the diffusion of water molecules in the two oils was gradually increased with increasing temperature, but the diffusion capability of water molecules in mineral oil was about 1.5–2 times higher than that in palm oil. In addition, the effect of temperatures on water molecules diffusion was found to be greater in mineral oil. This occurs because hydrogen bonds can be formed between palm oil and water molecules, which enhances the binding energy between palm oil and water molecules; moreover, palm oil provides less free space for diffusion of water molecules compared with mineral oil. Thus limiting the diffusion of water molecules in palm oil. Furthermore, because palm oil has a strong adsorption capacity for water molecules, and the water solubility of palm oil is relatively large, therefore, it is beneficial to increase the breakdown voltage of palm oil.