A simple method for regime identification and flow characterisation in bubble columns and airlift reactors

A new diagnosis method for regime identification in bubble columns and airl ift reactors based on a theoretical analysis of the auto-correlation functi on (ACF) of wall pressure fluctuations is proposed. It yields quantitative information, such as a characteristic time and a characteristic frequency o f the two-phase flow, which are closely related to the flow structure in th e prevailing regime. This method is shown to be simple, low-cost, reliable and efficient and has been applied successfully to a bubble column and an e xternal loop airlift reactor. Experimental data on both reactors are shown to be in good agreement with theoretically predicted values. The order of m agnitude of the characteristic time can be used for regime identification. Combined with an analysis of the cross-correlation Function (CCF) of two si gnals recorded simultaneously, the method is also able to yield an estimate of the axial dimension of the flow structures. This analysis is, therefore , promising for regime identification and how structure characterisation in industrial equipment. (C) 2001 Elsevier Science B.V. All rights reserved.