Experimental And Theoretical Studies On Turbulent Fluidization

Hydrodynamics of turbulent fluidization, specifically, concerning the flow regimes and their transitions, phase-distribution, overall circulation of solids and Bass transfer in fluidized beds, was investigated experimentally and theoretically.It was confirmed from the analyzed results that the flow characteristics in turbulent fluidized bed (TFB) is non-uniform.The measurements of phase fraction were conducted by means of an optical fiber probe. It was indicated that the marked phase -distribution exists radially and axially because of the wall effect and the end effect.Results from the gas tracer experiments showed that there exists the solid circulation, due to solids movement downwards along the wall and upwards through a inner core. The annular and core regions were characterized by the much more difference between their transfer efficiencies.The onset and the end of turbulent fluidization and related criteria were also examined experimentally.The flow transitions take ptace within a local region at first and then spread out in the bed. A modified Richardson-Zaki relation was found to adequately describethe local voidage in the fluidized bed,and the experimental criterion from the bubbling (or slugging)to the turbulent regime can be thus obtained for the local region. Furthermore, results obtained from experiments proved that the transition criteria would be given by the pressure fluctuation and the " local" Richardson-Zaki relation in different manner.It was also found that the dense phase readily undergoes the strong shearing stress of the gas phase with high velocity and this consequently results in the unstable structure of continuous dense phase, which could be recognized as the end of turbulent fluidization...