Number Stokes

Stokes number Stokes shift Stokes shifts Stone... 

D Roll diameter cm in St - Critical Stokes number representing ... 

Sfo is the Stokes number based on initial nuclei diameter do [Adetayo et al.. Powder Tech., 82, 37 (1995)]. Extent (/cf), depends logarithmically on binder viscosity and inversely on agitation velocity. Maximum granule size depends hnearly on these variables. Also, (/cf ), has been observed to depend hnearly on liquid loading y. Therefore, the maximum granule size depends exponentially on liquid loading. Fig. 20-73 illustrates this normahzation of extent (/cf), for the drum granulation of hmestone and fertilizers. 

This response time should be compared to the turbulent eddy lifetime to estimate whether the drops will follow the turbulent flow. The timescale for the large turbulent eddies can be estimated from the turbulent kinetic energy k and the rate of dissipation e, Xc = 30-50 ms, for most chemical reactors. The Stokes number is an estimation of the effect of external flow on the particle movement, St = r /tc. If the Stokes number is above 1, the particles will have some random movement that increases the probability for coalescence. If St 1, the drops move with the turbulent eddies, and the rates of collisions and coalescence are very small. Coalescence will mainly be seen in shear layers at a high volume fraction of the dispersed phase. 

Figure 8B shows the characteristic theoretical and practical collection efficiency curve. The x-axis may be plotted as particle diameter, in which case a series of curves at ever-decreasing sizes representing different stages of the impactor would exist. Converting the data to the square root of Stokes number overlays each of the particle size curves. The characteristic Stokes number for circular jets is 0.22. 

A similar approach to the analysis of hydrocyclones was presented by Svarovsky (1984, 1990). He deduced that the system can be described in terms of three dimensionless groups in addition to various dimensionless geometric parameters. These groups are the Stokes number,... 

Conditions of Coalescence. The outcome of the collision of two binder-covered particles is determined by the ratio of the initial kinetic energy of the system and the energy dissipated in the liquid bridge and in the particles. This can be expressed analytically by the definition of a so called Stokes number, St... 

The trajectory calculations mentioned above also yield analytical expressions for the critical Stokes number... 

Regimes of Granulation. In a real granulator, a spatial distribution of particle velocities and hence of Stokes numbers almost always exists, as... 

As granules grow still further, local Stokes numbers exceed the critical value St or St/St — co (see Fig. 23c), so that granule growth is no longer... 

Combining the previous two relationships allows us to estimate the extent of granulation as a function of the governing group of the Stokes number, or... 

The definition of a fine particle can be made more quantitative by introducing the article Stokes number St, which measures the particle-to-fluid response-time ratio to changes in the velocity (Fuchs, 1964) ... 

Note that we have used the fluid velocity U to describe convection of particles, which is valid for small Stokes number. In most practical applications, / is a highly nonlinear function of c. Thus, in a turbulent flow the average nucleation rate will depend strongly on the local micromixing conditions. In contrast, the growth rate G is often weakly nonlinear and therefore less influenced by turbulent mixing. 

Stokes number (Stk), 22 57, 23 184, 190 in depth filtration theory, 77 340 Stokes Raman scattering, 27 322 Stokes scatter, 76 485-486 Stokes shifts, 20 512 Stomach poison insecticides, 74 339... 

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