Abstract
Spatiotemporal measurements of bubble properties in a three-dimensional free-bubbling fluidized bed were done by using double-line arrays of reflective optical fiber probes and a microcomputer-aided data processing system. The measuring system could get real bubble shapes and the bimodal lateral distribution of the bubble frequency and holdup.
The aspect ratio D''B/DB to express the extent of bubble deformation was correlated with the coalescence index defined by (Uo-Umf)/UB. In the case of two vertically aligned bubbles which were going to coalesce, the average aspect ratio of the leading bubble was almost constant, while that of the following bubble increased sharply with coalescence index.
By plotting the bubble rising velocity UB against the real bubble diameter DB, three kinds of bubbles, viz., spherical cap, elongated and slug, could be distinguished. On the other hand, by plotting it against the bubble height D''B, the data for these three kinds of bubbles crowded around a line of KB = 0.9, showing that the three kinds of bubbles in real situations cannot be distinguished by such plot.
