Air-cooled heat exchanger applied to external rotary kiln wall in forced and natural draft

The present paper deals with experimental measurements performed within a heat exchanger devoted to the thermal rotating machineries. The device is based on a rotor-stator system scaled from an industrial rotary kiln. The thermal recovery system is able to capture the heat losses while the kiln wall is cooled. The inner moving wall-to-air heat exchanges measured through the insulated external shell are compared to the values established in various flow conditions similar to the present geometry. The thermal convection regimes are distinguished according to the different forces exerted on the fluid air motion: the buoyancy forces being compared to the inertial effects combining the centrifugal and the axial motions. General scaling relationships devoted to the natural, mixed and forced convection regimes are proposed in an extended range of the Richardson numbers.