AN EXPERIMENTAL STUDY OF BUBBLE FORMATION TRANSITIONS AT SIEVE PLATE SPARGERS

• Published in: Chemical engineering communications 1993-04, Vol.122 (1), p.245-261
• Main Authors: RAINBOLT, ROBERT, GLASGOW, LARRY A.
• Format: Article
• Language: English
• Subjects: Applied sciences; Bubble formation; Bubbling mode; Cellular viability; Chaotic dynamics; Chemical engineering; Exact sciences and technology; Reactors; Sparged reactors
• ISSN: 0098-6445; 1563-5201
• DOI: 10.1080/00986449308936160

Evidence has been presented in the literature suggesting that certain interracial phenomena may produce cellular damage in culture operations. In an earlier study of bubble-driven fluid motions in a sparged bioreactor reported by Glasgow et al. (1992), some energetic transitions associated with the bubble formation process were observed at sieve plate spargers. These transitions, involving both the active hole location and mode, were found to be independent of gas supply pressure fluctuations but quite sensitive to gas chamber volume. In the present study, five different experimental techniques have been employed in an effort to better characterize these transitions. Macrovideography and photographic flow visualization were initially used to record, classify, and count the transitions and it was discovered that frequency of transition was a qualitatively reproducible function of superficial gas velocity. A light-scattering experiment was then devised in which fluctuations in received light intensity were used to develop phase-space representations of the system dynamics. The resulting two-dimensional phase-space portraits revealed clearly distinct patterns with increasing gas velocities. A similar procedure was carried out at low superficial gas velocities with a pressure transducer connected to one of the sieve plate holes. Laser-Doppler velocimetry was also employed to characterize the cumulative probability functions for velocity at specific points in the vicinity of the sieve-plate sparger, in this part of the investigation, the photomultiplier signal was sampled directly with a digital storage oscilloscope and the data were processed off-line for determination of the Doppler burst frequencies. Additional data were collected using a commercial frequency tracker in order to obtain time series data that could be Fourier transformed, revealing the evolution of significant periodicities.