The experimental results of convective heat transfer in an annular gap flow, between a heated rotating inner cylinder and a cooled stationary outer cylinder with or without axial flow are presented. Two geometrical configurations are analysed : the surfaces of the cylinders are either smooth or the moving wall is smooth and the other is grooved axially. The results for rotational flow without axial flow reveal the interest of the presence of grooves and an important heat transfer as the velocity increase. In presence of axial flow, our investigations conducted in turbulent flow show that the situation of a smooth air gap is more favourable for heat transfer at the rotor.