Thermal analysis of disk-type transformer winding immersed in nanofluids using mixture and Eulerian–Lagrangian approach

A transformer plays a key role in the distribution network, and its overall performance is significantly affected by windings cooling. This paper presents a numerical study regarding the cooling of a disk-type winding in the presence of nanoparticles using single and mixture models to improve the thermal behavior of the transformer oil. Nanofluids are selected in two volumetric concentrations for multi-walled carbon nanotubes (MWCNT) and three volumetric concentrations of diamond nanoparticles. Results demonstrate that the nanofluids decrease the temperature of the disks so that the diamond nanoparticles with a volumetric concentration of 0.05% reduce the average disk temperature by about 2 °C. The Lagrangian particle tracking method is also used to study particle sediments, which shows that about 7% of nanoparticles are deposited. Finally, it is shown that the thermal performance of nanofluids in overload improves with increasing load.