Measuring the heat transfer coefficient in a direct oil-cooled electrical machine using thin film heat flux gauges

Abstract

This paper presents the measurement of the heat transfer coefficient (HTC) in an oil-cooled electrical machine with a segmented stator using double layered heat flux gauges. While heat flux gauges have been used for HTC measurements in applied to aerospace components such a gas turbine blades, to the authors knowledge the technique has never been applied to directly oil-cooled electrical machines. Therefore the paper explores the challenges linked with this technique when applied to this setting. The paper develops a correlation for the HTC on the sides of the pole pieces and compares the non-dimensional Nusselt number with existing correlations for laminar flow in pipes.