Flow Regime Identification in a Bubble Column via Nuclear Gauge Densitometry and Chaos Analysis

Abstract

The bubble column performance can change significantly as a result of flow regime change. Since reactor volume productivity, mass and heat transfer as well as mixing are affected by the prevailing flow regime, it is very important to know how to identify it. In this work, flow regime identification was performed on the basis of the Kolmogorov entropy (KE) algorithm applied to nuclear gauge densitometry data. In addition, the average cycle time was used for validation of the results. Three transition velocities were identified that delineated the boundaries of the three main hydrodynamic regimes. The first two transition points were also confirmed by the information entropy concept. The increasing KE trend in the bubbly flow regime and the decreasing KE trend in the churn-turbulent regime were predicted successfully by means of new semi-theoretical models.

New methods for flow regime identification in bubble columns and fluidized beds

“…Ruthiya et al (2005) detected the flow regime transitions in slurry bubble columns based on pressure fluctuations. In the past five years, in the field of bubble columns many new papers (Hur et al, 2013;Mota et al, 2011;Nedeltchev et al, 2011;Nedeltchev and Shaikh, 2013;Shaikh and Al-Dahhan, 2013;Şal et al, 2013;Shiea et al, 2013) have been published.…”

Análise Da Entropia De Kolmogorov a Partir De Medições Piv No Escoamento Da Fase Líquida De Uma Coluna De Bolhas

“…De fato, essa observação corrobora com os resultados obtidos por Nedeltchev et al (2007Nedeltchev et al ( , 2011. Em ambos os trabalhos, observaram-se regiões de máximos e mínimos da entropia de Kolmogorov a partir da variação da velocidade superficial do gás.…”

“…A entropia de Kolmogorov indica a taxa de perda de informação ao longo do atrator ou o grau de previsibilidade de pontos ao longo do atrator com evolução do tempo no sistema (GRASSBERGER e PROCACCIA, 1983). Foi verificado que a entropia de Kolmogorov é um parâmetro extremamente útil para quantificar o grau de caos que as colunas de bolhas aparentemente exibem (LETZEL, et al, 1997;VIAL et al, 2000;LIN et al, 2001;GOURICH et al, 2006;NEDELTCHEV et al, 2007;AJBAR et al, 2009;NEDELTCHEV et al, 2011). Grassberger e Procaccia (1983) relatam que a entropia de Kolmogorov maior que zero é uma condição suficiente para o caos, em que o sistema caótico é apenas previsível em um intervalo de tempo limitado.…”

Modeling of Multistage Bubble Column Reactors for Oxidation Reaction

“…The most important advantages of BCRs are their simple construction, isothermal operation, good interface contact, excellent heat-and mass transfer properties, low pressure drop, and low energy consumption [2,9,10]. Despite their simple construction, the reactor design and scale-up are still very difficult because of their complex hydrodynamics and mass transfer phenomena [4,11]. The two ideal flow regime models, i.e., completely stirred tank and plug flow, are not convenient for the prediction of phenomena occurring in BCRs.…”