Research on the thermal characteristics and structural optimization of oil-immersed transformer based on natural convection cooling in extreme environment

Effective thermal management is critical for oil-immersed transformers to mitigate insulation degradation and ensure reliability under extreme conditions. This study focuses on optimizing the raised structure parameters on the top and bottom inner walls of a 200 kVA transformer to enhance natural convection cooling. Employing the response surface methodology with the average Nusselt number as the objective function, we optimized key parameters—raised structure height, lateral spacing, longitudinal spacing, and oil flow attack angle. Detailed analysis of the conical raised structure highlights its ability to disrupt the boundary layer, strengthening the coupling between the internal flow and temperature fields of the insulating oil. The optimized design reduces the hot spot temperature by 8.17 K and increases the average Nusselt number by 14.3 %, significantly improving heat transfer efficiency. These findings offer valuable engineering insights for enhancing transformer performance and longevity in harsh environments.