Numerical investigation of 3D flow and thermal effects in a disc-type transformer winding

In this study, 3D Conjugate Heat Transfer simulations are performed to determine the flow and temperature distributions in a disc-type transformer winding. The results show that important three-dimensional phenomena exist due to the presence of the sticks and duct spacers and thus the flow in the cooling ducts cannot be considered axisymmetric. Moreover, the duct spacers prevent a portion of the disc surface from being in contact with the cooling fluid and consequently the insulation paper directly underneath them is at almost the same temperature as the copper conductor. Therefore, the results seem to support the common practice of placing sensors under a duct spacer to measure winding temperatures. Although 3D computations are very valuable, they are quite costly from a numerical perspective and for this reason a simulation strategy that improves the predictions of a 2D model is also presented and tested in the current paper.