Analysis of gas flow through erupting bubbles in a gas fluidized bed
As bubbles erupt from the surface of a gas fluidized bed, particles are projected upwards into the freeboard. Some are subsequently carried from the bed by their initial momentum and by the gas motion and others fall back onto the bed surface. In order to relate the design and operating characteristics of the fluidized bed to elutriation rate, it is necessary to have information on quantities such as the rate of flow of gas across the free surface of the bed in the vicinity of the erupting bubble and the variation of gas velocities at the free surface during the course of the bubble eruption. As a bubble moves upward towards the free surface, it carries gas with it, but there can also be a net flow of gas through the bubble. During the period of the actual eruption, vertical gas velocities in excess of those in the surrounding emulsion phase occur, resulting in a brief transient vertical flow of gas through the site of the erupting bubble. Precisely when this burst of gas flow begins and how long it lasts during a typical bubble eruption are not known. Only very limited quantitative information is available on the nature of the gas flow patterns which issue from the top of an erupting bubble. Measurements previously made using hot film probes, a laser Doppler anemometer and with flow visualization techniques show that the burst of gas flowing through the site of the erupting bubble forms a vortex motion at the free surface. The vortex has also been linked to the turbulent fluctuation patterns occurring in the freeboard above the surface of the bed.
- Research Organization:
- Energy Research Center, Packard Lab. number19, Lehigh Univ., Bethlehem, PA 18015
- OSTI ID:
- 6507467
- Report Number(s):
- CONF-861146-; TRN: 87-023668
- Resource Relation:
- Conference: AIChE winter annual meeting, Miami, FL, USA, 2 Nov 1986
- Country of Publication:
- United States
- Language:
- English
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