Experimental study of the contact heat transfer coefficient between the covered wall and solid bed in rotary drums

The heattransfer by contact between the covered inner wall surface and the solidbed in a rotary kiln was experimentally investigated. An indirect heated batch rotarydrum with a diameter of D = 600 mm and a length of L = 450 mm has been used. Inside the drum, a rotating and stationary measuring rod was installed, each assembled with 16 k-type thermocouples to measure the temperatures. Thus, the radial and circumferential temperature gradients within the solidbed were measured, and the contactheattransfer was determined from the heating of the bed. The effect on the contactheattransfercoefficient was estimated for the operational parameters of the drum, rotational speed (1, 3, 6 rpm) and filling degree (10%, 15%, 20%); the solidbed parameters, particle diameter (0.7, 1.3, 2.0 mm) and thermo physical properties (conductivity, heat capacity, density). As test material, quartz sand, glass beads and copper beads were used. The measured heattransfercoefficients were compared with theoretical calculations of four model approaches from the recent literature. A good agreement with just one of these model approaches could be achieved. (C) 2012 Elsevier Ltd. All rights reserved.