The heat transfer coefficient between a rotating cylinder wall and the spherical particles bed contacting with it was experimentally and theoretically studied. Two experiments were done: one in the steady condition with a constant feed of solid particles and the other in the transient condition with initially charged burdens. In the both experiments the steel cylinder assumed to be a rotating kiln was externally heated by means of Kanthal wire, which had been wound on the cylinder wall. The temperature was limited to a lower range in which radiation could be neglected. Wall, particles bed and free board temperatures were continuously measured by means of CA-thermocouples. Steel, glass, copper and alumina balls, 0.03 cm to 0.4 cm in size, were used as the solid burden.
Heat transfer coefficients between the wall and the particle bed which have been estimated in analyzing the measured temperatures can be explained by the thermal penetration model
