Molecular Dynamics Study of the Viscosity Characteristics of Soybean Oil-Based Natural Ester Insulating Oil

Many studies have shown that natural ester insulating oil is an excellent transformer oil with a superior flash point, fire resistance, and renewability compared to mineral insulating oil. However, due to their molecular properties, the high viscosity of natural ester insulating oils results in poor heat transfer, limiting their safe application in transformers. In this paper, the viscosity values of the soybean oil-based natural ester insulating oil are measured experimentally in the temperature range of 293 K to 433 K. The micro-mechanisms affecting the viscosity of natural ester insulating oil are investigated in conjunction with molecular dynamics simulations. We also conducted a correlation analysis between specific heat and viscosity and the simulation results. In addition, the kinematic viscosity of natural ester insulating oils as a function of temperature is also obtained in this paper by the free volume theory. The temperature ranges from 293 K to 433 K, and the functional model closely agrees with the experimental measurements. The research in this paper can be informative for the study and prediction of the viscosity of natural ester insulating oils as well as for the study of thermal conductivity.