Experimental study of liquid velocity profiles in large-scale bubble columns with particle tracking velocimetry

Abstract

A complete knowledge of the bubble column fluid dynamics relies on understanding the global and the local fluid dynamic properties. Unfortunately, most of the previous literature focused on the "global-scale" fluid dynamics, whereas a limited attention was devoted to the "local-scale". We contribute to present-day discussion by proposing an experimental study concerning the local liquid velocity profiles within the pseudo-homogeneous flow regime. The experimental study, based on a particle-identification and particle-tracking algorithm, was conducted in a large-diameter and large-scale bubble column (height equal to 5.3 m; inner diameter equal to 0.24 m) operated in the counter-current mode. We considered gas superficial velocities in the range of 0.37-1.88 cm/s and liquid superficial velocities up to -9 cm/s. Time-averaged and transient liquid velocity fields were obtained for five superficial gas velocities and four superficial liquid velocities at two measuring heights. Subsequently, the liquid velocity observations were coupled with previously measured bubble size distributions and local void fractions, to provide a complete description of the "local-scale" fluid dynamics. These data would help in the validation procedure of numerical codes, to support the prediction of industrial-scale relevant conditions.