Prediction of The Kolmogorov Entropy Derived from CT Data in a Bubble Column Operated under The Transition Regime and Ambient Pressure

Abstract

The Kolmogorov entropy (KE) algorithm was successfully applied to single source γ‐ray Computed Tomography (CT) data measured by three scintillation detectors in a 0.162 m‐ID bubble column equipped with a perforated plate distributor (163 holes × ∅︁ 1.32 · 10–3 m). The aerated liquid height was set at 1.8 m. Dried air was used as a gas phase, while Therminol LT (ρL = 886 kg m–3, μL = 0.88 · 10–3 Pa s, σ = 17 · 10–3 N m–1) was used as a liquid phase. At ambient pressure, the superficial gas velocity, uG, was increased stepwise with an increment of 0.01 m s–1 up to 0.2 m s–1. Based on the sudden changes in the KE values, the boundaries of the following five regimes were successfully identified: dispersed bubble regime (uG < 0.02 m s–1), first transition regime (0.02 ≤ uG < 0.08 m s–1), second transition regime (0.08 ≤ uG < 0.1 m s–1), coalesced bubble regime consisting of four regions (called 4‐region flow; 0.1 ≤ uG < 0.12 m s–1), and coalesced bubble regime consisting of three regions (called 3‐region flow; uG > 0.12 m s–1). The KE values derived from three scintillation detectors in the first transition regime were successfully correlated to both bubble frequency and bubble impact. The latter was found to be inversely proportional to the bubble Froude number. The KE model implies that the bubble size in this particular flow regime is a weak function of the orifice Reynolds number (db = 7.1 · 10–3Re0–0.05).

Applications of tomography in bubble column and trickle bed reactors

“…CT techniques have been used to characterize changes in the flow structure from different sparger designs (Ong et al, 2009;Varma & Al-dahhan, 2007), internals (Chen, Kemoun, et al, 1999;Chen, Li, et al, 1999) and composition (Hubers et al, 2005;Patel & Thorat, 2008) and have also been explored as a means to characterize the flow regime using ideas from chaos analysis (Nedeltchev, 2009;Nedeltchev et al, 2006Nedeltchev et al, , 2007. However, these studies have been limited to time-averaged measurements owing to the long time taken to acquire conventional CT measurements.…”

Application of Chaos Analysis for the Investigation of Turbulence in Heterogeneous Bubble Columns

“…Since pressure fluctuations in multiphase flows can contain important dynamic information, BC hydrodynamics have been widely studied using chaos analysis of the pressure fluctuation time series [8][9][10][16][17][18][19][20], gas holdup fluctuations [13], Computer-Automated Radioactive Particle Tracking (CARPT) data [11,21], Computed Tomography (CT) [12,22], bubbling frequency [23], etc. All of these studies demonstrated that the methodology of time-series analysis based on chaos theory can provide us with important insights into the complex hydrodynamics of gas-liquid BCs.…”