Bubble properties measurement in bubble columns: From homogeneous to heterogeneous regime

Bubble properties, such as local gas holdup, bubble frequency, bubble velocity, bubble size, and interfacial area concentration, are of great significance for the design and scale-up of bubble columns. In the present study, bubble properties in a 0.15 m in diameter bubble column were measured by a dual-tip conductivity probe. A new method was proposed to establish the relationship between chord length distribution (CLD) and bubble size distribution (BSD) without the assumption of fixed bubble aspect ratio. The bubble velocity and BSD measured by the probe were validated by a high speed camera in a square column. The results indicate that considering the decreasing of bubble aspect ratio with bubble diameter is required to obtain accurate BSD from measured CLD. Furthermore, the measured bubble properties at different axial positions show that the flow development is much more rapid in the churn-turbulent regime than that in the homogeneous regime. It is also found that the bubble breakage is dominant over the bubble coalescence in the homogeneous regime due to the large bubbles generated at the perforated distributor. The measured results provide a benchmark data for validation of CFD simulation. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.