Flow Regime Identification in a Bubble Column Based on Both Statistical and Chaotic Parameters Applied to Computed Tomography Data

Abstract

The Kolmogorov entropy (KE) algorithm was applied successfully to single source c-ray Computed Tomography (CT) data measured in a 0.162 m ID bubble column equipped with a perforated plate distributor (163 holes ·˘1.32 mm). Dried air was used as the gas phase and Therminol LT (q L = 886 kg m -3 , l L = 0.88 · 10 -3 Pa s, r = 17 · 10 -3 N m -1 ) was used as a liquid phase. Three different pressures, P, of 0.1, 0.4, and 1.0 MPa were examined. At each pressure the superficial gas velocity, u G , was increased stepwise by steps of 0.01 m s -1 up to 0.2 m s -1 . The average absolute deviation (AAD) was also used as a robust statistical criterion for regime transition. At all three pressures, based on the sudden changes in both the AAD and KE values, the boundaries of the following five regimes were identified: dispersed bubble regime, first and second transition regimes, coalesced bubble regime consisting of four regions (called 4-region flow), and coalesced bubble regime consisting of three regions (called 3-region flow). The existence of these regimes has already been documented. As the pressure increases, the transition velocity between the dispersed bubble and first transition regimes and the transition velocity between coalesced bubble (4-region flow) and coalesced bubble (3-region flow) regimes shift to higher u G values. On the other hand, at P = 0.4 MPa the second transition regime starts earlier. In addition, at P = 1 MPa the transition to coalesced bubble (4-region flow) is delayed.

Two-Phase Bubble Columns: A Comprehensive Review

“…These methods are based on the analysis of ε G data. Other flow regime identification methods are the fractal [319], wavelet [320,321], Hurst's [322,323], spectral and nonlinear chaos [93,320,[324][325][326][327][328][329][330][331][332][333] and Kolmogorov entropy [332][333][334] approaches. Some authors have used methods based on the Shannon entropy, which measures the degree of indeterminacy in a system [335,336].…”

Flow Regime Transitions in an Internal‐Loop Airlift Reactor

“…PFS is viewed as a chaotic time series and is successfully applied in multiphase contactors. Several literature reports of the successful use of chaotic invariants in the determination of regime transitions can be found [3][4][5][6][7][8]. The correlation dimension and the largest Lyapunov exponent are used to predict the regime transitions, since the classical static measurement fails in this manner.…”

Commercial scale slurry bubble column reactor optimization

“…At this high of a superficial velocity, Nedeltchev et al [21] proposes a "coalesced bubble regime (3-region flow)". These 3 regions are central plume, vortical region, and descending region.…”