The contact heat transfer in rotary kilns and the effect of material properties

Abstract

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.

This experimental work was conducted with different materials to study the influence of material properties on the contact heat transfer. The experimental study of conductive heat transfer between the covered wall surface and the solid bed has been investigated in an indirectly heated rotary drum with a diameter of D=0.6 m and a length of L=0.45 m. Temperature profiles of the gas, drum wall and solid bed were measured using 16 Type K thermocouples assembled on both a rotating and a fixed rod that attached inside the drum. Hence, the radial and circumferential temperature profiles were measured, and the contact heat transfer coefficients were calculated. Experiments have been carried out with six different materials including steel spheres, animal powder, cement clinker, quartz sand, glass beads and expanded clay. These materials have significantly different thermo physical properties (density, heat capacity and thermal conductivity) and particle diameters. The operating parameter, rotational speed, is varied by 1 and 6 rpm to evaluate the influence of rotational speed on the contact heat transfer coefficient in addition to the thermo physical properties and particle diameter. The measured contact heat transfer coefficients were compared with four model approaches from the literature. Good agreement between the experimental measurements and two model approaches were achieved.