Transient Simulation and Characterization of Conjugate Heat Transfer at Hydro Generator Polewindings

The analysis and the design of effective cooling schemes is essential for the integrity of turbomachinery components. Therefore, an accurate prediction of temperatures in critical devices is a necessity. This also applies to electrical turbomachinery such as hydropower generators. Focus of the current paper is on the prediction of the heat and fluid flow at the polewindings of such a machine. Three different numerical setups enabling the computation of winding temperatures are presented and benchmarked to each other. One of the approaches is the Bi-Fo scaling methodology, which demonstrates to perform best in terms of accuracy and computational effort. Finally, the impact of unsteadiness and turbulence modeling on the accuracy of the prediction is presented. In contrast to previous studies, the local distribution of fluctuations and its impact on the thermal boundary layers at the windings is highlighted yielding new fundamental insights into the local heat transfer mechanisms in hydro generators.