Na. Tsochatzidis et Aj. Karabelas, EXPERIMENTS IN TRICKLE BEDS AT THE MICROSCALE AND MACROSCALE - FLOW CHARACTERIZATION AND ONSET OF PULSING, Industrial & engineering chemistry research, 33(5), 1994, pp. 1299-1309
A randomly packed bed of nearly uniform spherical particles is employe
d to study cocurrent air/water downflow. Using a high-speed video came
ra, observations are made in the interstices close to the bed wall. Pa
tterns in the microscale (in constrictions and pores), similar to thos
e recently reported for a two-dimensional test section, combine to yie
ld macroscopically observed flow regimes. A gas penetration mechanism
is identified as a dominant feature at incipient as well as in well de
veloped pulsing flow. Special attention is paid to pulse formation and
growth. A new, nonintrusive conductance technique appears to hold dis
tinct advantages, over other methods, for on-line detecting the onset
of the pulsing regime. Time records obtained with this technique compl
ement information from flow visualization, shedding light on the mecha
nism of transition. Measurements of the trickling/pulsing transition b
oundary are in fair agreement with other data and model predictions fr
om the literature.