Assessment of a hydraulic network model for zig–zag cooled power transformer windings

•Assessment of a hydraulic network model of zig–zag cooled transformer windings.•Method: comparison of results with CFD simulations.•Current pressure drop correlations prove to be inadequate.•New correlations set up with CFD and built into network model.•Mass flow distribution and pressure drop over the pass qualitatively well predicted.

The prediction of mass flow distribution is a first, though crucial, step in the thermal design of zig–zag cooled power transformer windings. Typically this prediction is based on thermo-hydraulic network models, which critically depend on the applied correlations. In this paper new correlations for flow through elbows and for dividing/merging flow in T-junctions are numerically extracted from dedicated CFD studies and applied to a case study. It is shown that the new correlations are superior for the prediction of the mass flow distribution for this test case in comparison to correlations thus far available in literature.