The evaluation of the heat transfer coefficient in the air is made on rotating circular fins and submitted to an air stream parallel to the fins. A test bench was designed to measure, by infrared thermography, a fin cooling. The thermal balance in a fin during its cooling allows to obtain the expression of the heat transfer coefficient from the temperature time evolution of the fin. The tests were carried out for air stream Reynolds numbers (based on the shaft diameter and on the air stream velocity) until 40 000 and rotational Reynolds numbers (based on the shaft diameter and the peripheral speed) between 400 and 27 500. The relative influences of the Reynolds numbers and of the Grashof number representing the natural convection due to gravity on the heat transfer on the fin surface were analysed.