The liquid velocity profile induced by a chain of bubbles is studied theoretically and a comparison with measurements is made. The wake velocity and the bubble shape involved in the theoretical development are considered based on the wake theory and the previous empirical relation for single bubbles, respectively.
The shape and wake volume of chain bubbles can be treated in the same manner as those of single bubbles by using relative velocity. As a result, using the previous results of the drag coefficient and shape of single bubbles enables the prediction of the rising velocity of chain bubbles.
It is found that both probes gave an intense signal for air bubbles but that only probe D gave particle signals, although the latter were weakin the dispersed zone. This fact is more clearly seen in Fig. 4 (b) for a dense bubbling zone. Since the highest voltage of the A/D converter was set at 2.5 V, the higher part of the signal for the bubble phase, which reached about 4V, was cut. However, one may readily distinguish the characteristic signals for bubbles from those for particles.
The lateral mixing of solid particles in a centrifugal fluidized bed in which the rotation axis is horizontal was investigated from the unsteady-state behavior of tracer particles. The lateral mixing characteristics were analyzed by a diffusion model identical to that for a conventional fluidized bed. The lateral dispersion coefficient of particles was affected by variables such as gas velocity, rotational speed of the rotor, particle diameter, bed height and minimumfluidized velocity. From the experimental results an empirical equation for the coefficient was obtained. Its value for a centrifugal fluidized bed wassmaller than that calculated from empirical equations for a conventional fluidized bed, because of smaller bubble diameter and bed height, centrifugal force, and the like.
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