Discoidal rotor–stator systems are especially used in rotating machines and in numerous industrial applications. The design of high-power machine requires compliance with certain cooling-related stresses. Using an air jet impinging on a rotating disk is one way to increase the global heat exchange. This work focuses on the numerical and experimental study of convective heat transfer in a rotor of a discoidal machine with an eccentric impinging jet. Convective heat transfers are determined experimentally in steady state on the surface of a single rotating disk. The experimental technique is based on the use of infrared thermography to access surface temperature measurement and on the numerical resolution of the energy equation in steady state to evaluate local convective coefficients. The results from the numerical simulation are compared with heat transfer experiments for rotational Reynolds numbers between 2.38 × 105 and 5.44 × 105 and for the jet's Reynolds numbers ranging from 16.5 × 103 to 49.6 × 103. A good agreement between the two approaches was obtained in the case of a single rotating disk, which confirms us in the choice of our numerical model. On the other hand, a numerical study of the flow and convective heat transfer in the case of an unconfined rotor–stator system with an eccentric air jet impinging and for a dimensionless spacing G = 0.02 was carried out. The results obtained revealed the presence of different heat transfer zones dominated either by rotation only, by the air flow only, or by the dynamics of the rotation flow superimposed on that of the air flow. Critical radii on the rotor surface have been identified.