Prediction of Pressure Drop and Flow Distribution in Disc-Type Transformer Windings in an OD Cooling Mode

In this paper, a method for predicting pressure drop and flow distribution in disc-type transformer windings in an oil-forced and directed cooling mode is proposed. First, dimensional analyses are conducted to identify the independent dimensionless variables that affect pressure drop over and flow distribution in the winding. Next, parametric sweeps are performed with computational fluid dynamics simulations under isothermal flow conditions. Finally, pressure drop and flow distribution results obtained from the simulations are correlated with the previously identified dimensionless variables to derive correlation equations. These equations have been verified over a range of different isothermal and non-isothermal flow cases and applied to identify the criteria for the occurrence of reverse flow resulting from a combination of pass inlet flow rate and winding geometry. In addition, the method provides an insight into the controlling parameters to determine the minimum oil velocity in horizontal cooling ducts.