Bubble size estimation in slurry bubble columns from pressure fluctuations

Detecting regime transitions in slurry bubble columns using pressure time series

“…The coherence is zero for completely uncorrelated pressure time series. The power in both time series can be expressed in terms of the coherent-output power spectral density (COP), and the incoherentoutput power spectral density (IOP), representing the PSDs due to global (correlated) pressure fluctuations, and due to local (uncorrelated) pressure fluctuations, respectively 35,36 …”

“…Similarly, the incoherent standard deviation of pressure time series can be used as a measure of the large bubble diameter. 35 The average frequency also appears to detect the first and second transition points. However, these transitions do not always correspond to changes in the physical phenomena observed by video imaging.…”

Unified study of flow regimes and gas holdup in the presence of positive and negative surfactants in a non-uniformly aerated bubble column

“…On the other hand, timeaveraged study, based on the evolution of e G with U G , although valuable, is a first approximation when quantitatively identifying the particular flow regime developed (Akita and Yoshida, 1973;Deckwer et al, 1980;Gourich et al, 2006;Hikita et al, 1980;Maruyama et al, 1981;Ruzicka et al, 2001a;Vial et al, 2000;Zahradnik et al, 1997) and the possible transition points. Finally, the spectral analysis (Buwa and Ranade, 2002;Chilekar et al, 2005;Díaz et al, 2006;Drahoš et al, 1991;Vial et al, 2000), based on the calculation of the frequency spectra and plume oscillation period (POP) values, provides very valuable information regarding the existence and characterization of nonstationary structures, such as bubble plumes (Becker et al, 1994;Buwa and Ranade, 2002;Delnoij et al, 1997;Díaz et al, 2006;Vial et al, 2000), that perfectly complements the U G vs. e G analysis.…”

Origin of pressure fluctuations in an internal-loop airlift reactor and its application in flow regime detection

“…bed surface, distributor and supply system). Pressure fluctuations are of multi-scale and complex in nature (Chilekar et al, 2005;Bi, 2007). Two types of pressure fluctuations were defined: global pressure fluctuations from bubble formation in the distributor, eruptions at surface of bed, etc.…”