A numerical study of the effect of a hybrid cooling system on the cooling performance of a large power transformer

This study analyzed the conjugate heat transfer and fluid flow of radiators used in a power transformer to investigate the cooling performance. The flow and temperature distributions around the radiators were analyzed to investigate the fundamental mechanisms of radiator cooling in the hybrid cooling system. The oil flow rate in the radiators was varied in the range of 44.4 LPM  ∼  309.6 LPM. The cooling fan location was also varied along the bottom and right surfaces of the radiators, and their effects on the cooling performance were evaluated. The computational results using the standard k-ε turbulence model were compared with the measured data, showing the good agreement between them with the difference which is less than 5%. The cooling fans located at the center of the bottom surface and the bottom of the right surface resulted in the best cooling performance regardless of the insulating oil flow rate due to the positive interaction between the vertical and horizontal air flows induced by fans, giving about 22% higher cooling performance than the worst cooling performance at all flow rate.