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Prediction of rolling bed motion in rotating cylinders



A mathematical model for the range of rolling bed motion has been developed to calculate the transverse solids motion in rotating cylinders. It is based on mass and momentum balances with physically specified and hence known initial conditions. The behavior of the bed material need only be described by two measurable parameters, the dynamic angle of repose and the angle of slope at the start of the boundary line (interface between the cascading layer and the plug flow region). The shape of the boundary line, the thickness of the cascading layer, the mass flow rate, and the velocity at the surface can be predicted as a function of rotation speed, filling degree, and cylinder diameter. No fitting parameter is needed for the calculation. To verify the model, experiments were carried out for many bed materials and rotating cylinder conditions. A correlation for the angle of slope at the start of the boundary line is given. The calculated results of the model are then compared to our own measurements and those reported in the literature. It is shown that the model agrees relatively well with the experiments. © 2004 American Institute of Chemical Engineers AIChE J, 50: 2783–2793, 2004

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