Reynolds spouted beds

Kishan B. Mathur and Norman Epstein, Dynamics of Spouted Beds W. C. Reynolds, Recent Advances in the Computation of Turbulent Flows R. E. Peck and D. T. Wasan, Drying of Solid Particles and Sheets... 

The mixing characteristics of the fluid in a spouted bed of solids have not been studied. Since the particle Reynolds numbers involved in both the annulus and the spout are relatively high, the extent of any axial mixing experienced by the fluid in either channel is likely to be small, especially for the more common case of gas spouting. For the bed as a whole, however, it could be significant due to the very uneven velocity distribution as between spout and annulus, which would cause an effect akin to Taylor diffusion. 

Figure 51.15 presents the relationship between Re and the Reynolds number for the settling velocity of grain R yas well as various operating zones of spouted beds. To estimate the pressure drop across a spouted bed, one can use the approximate formula ... 

The previously explained method for the determination of the minimally required gas volume flow rate is of general applicability, but approximate. Alternatively, correlations that refer to a speciflc type of spouted bed may be used. A number of correlations of this type for conical and conical-cylindrical spouted beds are summarized in Tab. 4.1, based on an evaluation by Piskova (2002). The geometric quantities involved are illustrated in Fig. 4.10. All correlations of Tab. 4.1 lead to the minimal value of a Reynolds number ... 

Reynolds numbers - as defined by Eq. 4.8 - that correspond to the lower limit of the stable operating regimes of Fig. 4.13 may be denoted by Re n,sf Correlations developed for RCjn.st are summarized in Tab. 4.5. However, it should be noted that Fig. 4.13 and Tab. 4.5 provide only coarse estimates for the stable operation ranges of different types of spouted bed. The reason for this is that even small variations in the apparatus geometry - especially variations in the construction of the gas entrance - can have a significant influence on the fluid dynamics of the spouted... 

Tab. 4.5 Correlations for the Reynolds number at the lower limit of the stable operating region for various types of spouted bed equipment.

Figure 21 CDimensionless spout diameters as a function of dimensionless height for small columns. Case A, test case Case B, all dimensionless parameters matched, bed diameter halved Case C, particle Reynolds number mismatched Case D, Froude number mismatched Case E, density ratio, Reynolds number mismatched Case F, bed Reynolds number mismatched Case G, internal friction angle, loose packed voidage mismatched. (From He et al. 1995.)...

---