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Liquid backmixing in bubble columns via computer-automated radioactive particle tracking (CARPT)

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Abstract

A single, fully wettable, neutrally buoyant, small radioactive particle and 16 scintillation detectors are utilized to monitor particle motion in gas-liquid bubble columns of different heights and diameters and at different gas superficial velocities. Instantaneous velocities, time-averaged velocities, Reynolds stresses and eddy diffusivities are computed from the particle position versus time data. Anisotropy, indicated by the data, was confirmed by Hurst's rescaled R/S analysis of the fluctuating velocities. For the radial direction, Hurst's exponent is about 0.5 in agreement with a random walk (diffusion)-type mechanism, while in the axial direction, Hurst's exponent of about 0.7 indicates the persistence of long-range effects.

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Abbreviations

\(\vec a\) :

position vector

D :

eddy dispersion coefficient, (cm2/s); also column diameter, (m)

H :

Hurst's exponent

N exp :

number of independent experiments

R L :

autocorrelation coefficient

R(t, s) :

accumulated range of fluctuation velocities, (m/s)

rms:

root mean square

S(t, s) :

sample normalized standard deviation

s :

number of recorded (sampled) fluctuating velocities

t :

time, (s); also number of sampled fluctuating velocities

T L :

integral time scale of turbulence, (s)

v∼ :

Lagrangian fluctuating velocity, (m/s)

U G :

superficial gas velocity, (m/s)

u :

index of summation

X(t) :

random variable, i.e. fluctuating velocity component, (m/s)

X * (t) :

record of random variables (i.e. fluctuating velocities) de fined by Eq. (5)

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Authors and Affiliations

  1. Chemical Reaction Engineering Laboratory, Washington University, 63130, St. Louis, MO, USA

    Y. B. Yang, N. Devanathan & M. P. Duduković

Authors
  1. Y. B. Yang
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  2. N. Devanathan
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  3. M. P. Duduković
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Currently with Abbott Laboratories, Abbott Park, IL 60064

Currently with Amoco Oil Research Center, Naperville, IL 60566

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Yang, Y.B., Devanathan, N. & Duduković, M.P. Liquid backmixing in bubble columns via computer-automated radioactive particle tracking (CARPT). Experiments in Fluids 16, 1–9 (1993). https://doi.org/10.1007/BF00188499

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