Heat transfer coefficient distribution on the pole face of a hydrogenerator scale model

Abstract

This paper focuses on the effect of rotation on heat transfer mechanisms in rotating machines with the purpose to improve the understanding of thermal phenomena and cooling of hydrogenerators. Using a simplified scale model equipped with a heated pole, it was possible to measure the temperature distribution on the pole surface and to deduce, through numerical simulations, the heat transfer coefficients. The results show an asymmetric profile in the tangential direction since lower h values are found closer to the trailing edge due to the presence of a flow recirculation zone. Furthermore, the heat transfer profiles indicate that, although fans improve cooling at the top and bottom ends of the pole, the highest h values are found in an intermediate region. This is due to the flow from the fans that enters the interpole space and only after penetrating a certain distance in the axial direction it exits through the air gap and goes around the pole face. The study also shows that the heat transfer coefficients along the pole face at 300 rpm average about four times those at 50 rpm.