Bubble characteristics in a developing vertical gas-liquid upflow using a conductivity probe

Experiments were carried out in an 82.6-mm-dia column with a perforated dis tributor plate. Conductivity probes on the axis of the column were used to measure local bubble properties in the del eloping flow region for superfic ial air relocities from 0.0018 to 6.8 m/s and superficial water velocities from 0 to 0.4 m/s, corresponding to the discrete bubble, dispersed bubble, coalesced bubble, slug, churn, bridging, and annular flow regimes. Bubble f requency increased linearly with gas velocity in the discrete and dispersed bubble regimes. Bubble frequency also increased with gas velocity in the s lug flow regime, but decreased in the churn and bridging regimes. Bubble ch ord length and its distribution were smaller and narrower in the dispersed than in the discrete bubble regime. Both the average and standard deviation of the bubble chord length increased with gas velocity in the discrete, di spersed, and churn flow regimes. However, the average bubble chord length d id not change significantly in the slug flow regime die to the high populat ion of small bubbles in the liquid plugs separating Taylor bubbles. The bub ble travel length. defined as the product of local gas holdup and local bub ble velocity divided by local bubble/void frequency, is used to correlate b ubble characteristics and to characterize the flow regimes. [S0098-2202(00) 00101-2].