It is reported a three-dimensional numerical study for the air-gap heat transfer of a permanent magnet synchronous machine. The objective is to evaluate the air-gap convective heat transfer coefficient. The models and the procedures presented are able to manage annulus flows with uneven surfaces geometries. In such situations applying analytical expressions is not always the most effective approach. The thermal properties of the gap fluid are non-linear, that is, temperature dependent.

Keywords: Electrical machine, Conjugated heat transfer, Thermal analysis, Computation fluid dynamic (CFD)