^{1,a}, Jochen Mellmann

^{2}, Fabian Herz

^{1}and Eckehard Specht

^{1}

^{1}Institute of Fluid Dynamics and Thermodynamics, Otto von Guericke University Magdeburg, Universitätsplatz 2, Magdeburg 39106, Germany.

^{a}koteswara.sunkara@st.ovgu.de

^{2}Leibniz Institute for Agricultural Engineering Potsdam-Bornim (ATB),

Department of Postharvest Technology, Max-Eyth-Allee 100, Potsdam 14469, Germany

Rotary drums, installed with longitudinal flights are often used to dry/cool granular materials in large quantities. Performance of such drums greatly depend on the uniform distribution of the particles over the drum cross section, which is attained by an optimal design and allocation of the flights. In this study, a mathematical model has been developed for the rectangular flight to optimize the total particle surface area which is a function of the cascading rate and falling time of the particles. The falling time in turn is a function of curtain height and can be estimated by geometrical analysis. Influence of the number of flights and the flight length ratios has been studied. It was observed that, as the flight length ratio increases the cascading rate decreases during the initial discharge, but increases rapidly at higher discharge points resulting the bulk movement of the solids, which also determines the density of the curtains. Experiments were carried out to validate the developed model with a drum of 500 mm in diameter and 150 mm in length. The experiments were performed with different flight profiles and flight numbers (12 and 18). Good agreement was found between the experiments and the model predictions.