TRANSVERSE BED MOTION AND CONVECTIVE MASS -TRANSFER IN ROTARY CYLINDERS .1. WITHOUT LIFTING FLIGHTS

The type of transverse bed motion in rotary cylinders depends on the F roude number and the ratio of the cylinder to particle diameter. In th e case of the ''rolling bed'', the radial velocity profile can be obta ined by modelling the bed as a viscous-inelastic, dilatant fluid. In c omparison with experimental data on the thickness of the so-called act ive layer, this model shows good agreement. The convective mass transf er coefficient at the surface of the bed generally depends on the axia l gas velocity, particle size, rotational speed and cylinder geometry. However, the influence of the rotational speed can be reduced to the transverse particle velocity at the surface. Experimental data obtaine d from drying experiments allow a general correlation to be fitted for the heat and mass transfer at the surface of the bed.