Bubble swarm velocity in a column

✍ Scribed by G. Shen; J.A. Finch

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 711 KB
• Volume: 51
• Category: Article
• ISSN: 0009-2509
• DOI: 10.1016/0009-2509(95)00409-2

✦ Synopsis

In an air-water-only system under batch operation, a bubble interface was created in a laboratory column by introducing a step change in gas flow, and the rise velocity of this interface, u~n, was measured using a novel method based on electrical conductivity with a custom-designed fast-response conductivity meter. The u~, was plotted against J~2/Jot, where Jgl and Joz are the superficial gas velocities before and after the step change, respectively. The velocity of the undisturbed system was estimated by interpolation at Jo2/Jgl = 1. This velocity was referred to as the hindered velocity, u h. The local average gas velocity, Uo, lo c (=J0.aoJ%.loc) [corrected from the average gas velocity (=J0/%) to account for the local pressure], was different from u n. It is argued that u h is the real bubble swarm velocity and uo,~o c is the bubble swarm velocity for the ideal case of uniform bubble size. Unlike ug.~°c, the u h was constant along the column, a result supported by theoretical momentum analysis. The u h is proposed as the key characteristic swarm velocity of the system.