Atsushi Tsutsumi

In this present work, nonlinear dynamic analysis was performed to the fluctuation signals of the local heat transfer rate measured in three-phase reactors of different scales to characterize the dynamics of three-phase reactors. The results of nonlinear test with surrogate data give evidence of nonlinear determinism in heat transfer rates series. The chaotic nature of the local heat transfer rate was further characterized in terms of the correlation dimension and Kolmogorov entropy. It was found that the correlation dimensions were in the range between 2.0 and 4.0 and Kolmogorov entropies were varied with the change of measurement positions and the operating conditions. With the increase of column scale or the addition of solids, Kolmogorov entropies decrease significantly. The dependence of chaotic parameters on the column scale is considered to be closely related to the different macroscopic flow structures observed in three-phase reactors of different scales.

Local bubble behaviours were investigated in three bubble columns with different diameters of 200, 400 and 800 mm. By means of a novel single‐tip optical fibre probe employing laser Doppler technique, the local gas holdup, bubble frequency, bubble size and velocity were measured simultaneously at different locations of the columns. Measurements were performed in air‐water system at superficial gas velocities up to 90 mm/s. The averaged profiles and instantaneous measurements were analyzed and compared for different columns. The presence of a coherent gross circulation structure spanning the entire column diameter in the larger column rather than a pair of symmetrical circulation cells observed in the smaller columns has been confirmed.