Investigations of temperature fluctuation history records of gas-solid fluidized beds

An experimental technique has been developed to delineate the different hydrodynamic regimes of a gas-solid fluidized bed, each regime signifying a characteristic type of fluidization. The technique involves the 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-μm average diameter spherical glass beads at ambient conditions. The statistical functions computed at each gas velocity were the standard deviation, probability density function, autocorrelation function, 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-transfer coefficient were also measured as functions of gas velocity. Their appropriateness to represent the quality of bed fluidization has been examined.