INVESTIGATIONS OF TEMPERATURE-FLUCTUATION HISTORY RECORDS OF GAS-SOLID FLUIDIZED-BEDS

An experimental technique has been developed to delineate the differen t hydrodynamic regimes of a gas-solid fluidized bed, each regime signi fying a characteristic type of fluidization. The technique involves th e measurement and statistical analysis of temperature-history records of an element of the heat-transfer surface immersed in a fluidized bed in which different regimes are brought about by changing gas velocity . The experiments were conducted in a 0.153-m square fluidized bed of 2093-mu m average diameter spherical glass beads at ambient conditions . The statistical functions computed at each gas velocity were the sta ndard deviation, probability density function, autocorrelation functio n, and power spectral density function. The standard deviation and the major frequency defined from the power spectral density function were found to represent characteristically the bubbling, transitional and turbulent hydrodynamic regimes. The bed voidage and the local heat-tra nsfer coefficient were also measured as functions of gas velocity. The ir appropriateness to represent the quality of bed fluidization has be en examined. (C) 1998 Elsevier Science Ltd. All rights reserved.