Flow visualisations and heat transfer measurements on a rotating disk, with a relatively small centred jet perpendicularly impinging on it. are accomplished by means of infrared (IR) thermography associated with the heated-thin-foil thermal sensor. Flow visualisations show a strong interaction between the turbulent jet and the laminar boundary layer over the rotating disk. A new governing similitude parameter is introduced and a heat transfer correlation for the Nusselt number at the disk centre is proposed. In most cases, the Nusselt number radial profiles tend to overlap if they are normalised with the Nusselt number computed by means of this correlation. (C) 2007 Elsevier Ltd. All rights reserved.