P. Gupta et al., A novel signal filtering methodology for obtaining liquid phase tracer responses from conductivity probes, FLOW MEAS I, 11(2), 2000, pp. 123-131
Local conductance measurements using a conductivity cell, consisting of ele
ctrode plates encased in plastic tubing, have been employed for point condu
ctance measurements in two-phase gas-liquid flows. It is shown that such me
asurements can provide local liquid mixing information in gas-liquid flows
such as those encountered in bubble and staged bubble columns either with a
n upward flow of gas in a batch liquid, or with co-current or counter-curre
nt flow of gas and liquid. This requires the characterization of the liquid
phase conductance from the electrical signals acquired by such a conductiv
ity probe (cell) in the presence of bubbles, which is non-trivial clue to t
he systematic lowering of the conductance of the probe measurement volume w
hen a bubble contacts or pierces the probe tip. Thus, application of standa
rd digital filtering techniques to signals masked by frequent bubble passag
e results in an inaccurate representation of liquid conductance by filtered
signals. A special purpose software filtering technique has been developed
in this work to address this issue and to cleanly extract the actual liqui
d phase conductance from response signals representing the instantaneous po
int conductance of a bubbling two-phase gas-liquid mixture. The implementat
ion of the new filtering algorithm has been achieved through coupling with
standard Butterworth filters in MATLAB(TM), version 5. (C) 2000 Elsevier Sc
ience Ltd. All rights reserved.