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

The heat transfer by contact between the covered inner wall surface and the solid bed in a rotary drum was experimentally investigated. An indirectly heated batch rotary drum 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 solid bed were measured, and the contact heat transfer was determined from the heating of the bed. The operating parameters, rotational speed and filling degree of the drum were varied in the range of n=1, 3, 6 rpm and F=10, 15, 20% and the effect on the contact heat transfer coefficient was estimated. Quartz sand with a mean particle diameter of dP=0.2 mm was used as the testing material. The measured heat transfer coefficients were compared with theoretical calculations of four model approaches from the recent literature. A good agreement between the measurements and three model approaches could be achieved.

► Model approaches for the contact heat transfer in rotary kilns were analyzed.
► Contact heat transfer was experimentally investigated in a batch rotary drum.
► Influence of the operational parameters on the contact heat transfer was determined.
► Measurements show reasonable agreement with three of the model approaches.