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International Heat Transfer Conference 11

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

Solid Flow Patterns and Heat Transfer Characteristics in a Pulsated Fluidized Bed with Flowing Large Bubbles

Akira Nishimura
Department of Energy Engineering and Science Nagoya University Furo-cho, Chikusa-ku, Nagoya, 464-01, JAPAN

Seiichi Deguchi
Centerfor Integrated Research in Science and Engineering Nagoya University Furo-cho, Chikusa-ku, Nagoya, 464-01, JAPAN

Hitoki Matsuda
Reseach Center for Advanced Waste and Emission Management Nagoya University Furo-cho, Chikusa-ku, Nagoya, 464-8603 Japan

Masanobu Hasatani
Department of Energy Engineering and Science Reseach Center for Advanced Waste and Emission Management Nagoya University Furo-cho, Chikusa-ku, Nagoya, 464-8603 Japan

Arun S. Mujumdar
Department of Chemical Engineering, McGill University, Montreal, Canada; National University of Singapore 9 Engineering Drive 1 Singapore 117576

DOI: 10.1615/IHTC11.4150
pages 485-490

Аннотация

Enhancement of bed-to-surface heat transfer and particle mixing rates is still needed in pulsated fluidized bed technology, in which fluidizing gas is regulated periodically for applications in drying, catalytic reaction and heat exchanging systems. It is believed that mass and heat transfer rates in radial direction of pulsated fluidized bed could be promoted by passing large bubbles through the bed. Measurements of pressure drop and heat transfer coelficient between an immersed heater and the bed along the riser and observation of the fluidization mode with large bubbles were carried out. The results were compared with conventional fluidized beds with continuous gas flow to investigate the hydrodynamic and heat transfer characteristics in pulsated fluidized bed.
Peculiar fluidizing conditions for the pulsated fluidized bed, such as existence of larger bubbles and higher pressure drops as compared with conventional fluidized bed, were obtained when the oft-period ( no fluidizing air ) was longer than the bubble transit time through the bed. It is noted that the enhancing effect of pulsating operation on the heat transfer rate can be obtained with higher bed height. When the oft-period duration was sufficiently short (in the order of 0.5 or 1.0 s ), there were no significant differences in the heat transfer rates between pulsated and conventional fluidized beds. On the other hand, the pulsated fluidized bed showed good heat transfer characteristics for longer off-period duration up to 4.0 s. This may result of the enhancing effect on the heat transfer rate by particle mixing with penetrating large bubbles through the riser overshooting the obstructing effect owing to static bed formation during the off-period.

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