ANALYSIS OF THE VARIABLES CONTROLLING GAS-JET EXPANSION ANGLES IN FLUIDIZED-BEDS

The expansion angle theta of gas jets issuing in fluidized beds is one of the parameters necessary for the application of hydrodynamic model s of the jet region. A limited body of experimental data is available in the literature so that a method of prediction is still lacking. The phenomena associated with the formation of a jet above an upward gas discharging nozzle in a fluidized bed have been analysed with particul ar reference to the influence that the operating variables and the geo metric configuration have on theta. The analysis allowed the relevant variables concerned with these phenomena to be found and their connect ion with the dynamic features of the jet and of the bed, contrasting w ith the current viewpoint that considers theta as a parameter dependen t only on the static characteristics of the system. The dimensional an alysis yielded a set of relevant dimensionless groups among which the two-phase Froude number provides a good correlation of most of the lit erature data.