Abstract
A pulsating fluidized bed is operated with two sequential durations designated as an onβperiod with injecting fluidization gas and an offβperiod without it. The heat transfer coefficient between a vertically immersed heater and bed in a pulsating fluidized bed is measured under various pulse cycles and fluidized particles. The obtained results are compared with those in a normal fluidized bed with continuous fluidization air injection. The relationship between heat transfer coefficients and bubble characteristics, evaluated using a digital video camera, has also been investigated. For certain fluidized particles and operating pulse cycles, the fluidization of particles and the increment of heat transfer coefficients can be obtained under a mean air velocity based on a pulse cycle duration smaller than the minimum fluidization air velocity in a normal fluidized bed. Under the pulse cycles where a static bed through the whole bed is formed in the offβperiod duration, the improved heat transfer rate over that in a normal fluidized bed can be measured. This may be attributed to large bubble formation. As heat transfer in the pulsating fluidized bed is obstructed with increasing time to keep a static bed due to the excessive offβperiod duration, it is indicated that there is an optimum offβperiod duration based on the heat transfer rate. Β© 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 31(4): 307β319, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.10038