Dynamics of gas-liquid flow in a cylindrical bubble column: Comparison of electrical resistance tomography and voidage probe measurements

- Ability of ERT to measure time-resolved local gas volume fraction verified by voidage probes.
- Verification of time-averaged gas volume fraction distribution.
- Characterization of low- and high-frequency oscillations generated by meandering bubble plume and bubble scale processes.
- Effects of superficial gas velocity and sparger configuration on dynamics and time-averaged gas volume fraction.

Gas-liquid flow in bubble columns is inherently unsteady, and dynamics of such flow is known to influence local mixing, mass and heat transport and therefore, the performance of bubble column reactors. The present work is carried out to verify dynamics of gas-liquid flow measured using time-resolved Electrical Resistance Tomography (ERT) with the measurements performed using in-house developed voidage probes. Experiments were performed in a cylindrical bubble column under dilute to dense conditions (superficial gas velocity (UG) in the range of 1-40 cm/s). The instantaneous and time-averaged gas volume fraction distribution was measured using the ERT and voidage probes for uniform and local spargers. The time-averaged gas volume fraction measured using both the techniques was found in a quantitative agreement for all UG and sparger configurations considered in the present work. The low-frequency oscillations (<1 Hz) generated by meandering motion of bubble plume and high-frequency oscillations (1-10 Hz) generated by bubble-scale processes, measured using the ERT and voidage probes were in a satisfactory agreement. The results reported in the present work will help to benchmark the ERT to infer the dynamics of gas-liquid flow and to validate the dynamic characteristics predicted using CFD models under dense flow conditions.

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