Packings porosity

Fig. 22. Performance cut diameter predictions for typical dry packed bed particle collectors as a function of bed height or depth, packing diameter and packing porosity (void area) S. Bed irrigation increases collection efficiency or decreases cut diameter (271). SoHd lines, = 25 mm dashed lines,...

Together with u, and Ap, the specific permeability, K°, is also linked with the solvent viscosity, p, and the column packing porosity, s. ... 

This value of u was additionally corrected by some authors [8,23] to account for the nonuniformity of packing porosity and for the wakes that packing elements produce in the gas stream, especially in organized packing with free space between the packing elements. Verver and van Swaaij [8] introduced an effective packing porosity, while Kiel and van Swaaij [23] defined an effectiveness factor. Both of these empirical parameters have to be determined from experimental data. 

A serious limitation in the data collected by these researchers was the ct that a was measured in permeation rather than in filtration conditions the packing (porosity) and the resistance of newly formed filter cake under the dynamic ccmditions obtaining during filtration may be e ected (in general) to be different fi om those applying after prolonged rotation The latter results in the densest packing and hipest a values. 

The A, B and C terms are related to flow anisotropy, molecular longitudinal diffusion and mass transfer processes, respectively. The theoretical support for the Knox equation was derived by Horvath [12]. The A term cannot be expressed simply. The theoretical treatment links A to structural parameters of the column packing, porosity, pore volume, pore diameter and tortuosity [12]. A is related to the flow pattern and the general band spreading due to "eddy" diffusion [13]. The B term (longitudinal molecular diffusion) was written as [13] ... 

Fig. 3. shows the axial voidage distribution in the packing with 3 different stiffness coefficients (spring constants). Each dot represents the simulation result of one slice. Fig. 4. plots the bed depth for the reassembled slices. Fig. 5. and 6. present the corresponding results for case 2, which has a slightly denser initial packing porosity. 

Naturally, it is of interest to find out what this maximum packing porosity implies. For convenience, let us consider the binary packing mixtures of particles... 

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