Number-based mean particle radius

Jeffrey remarks that Kohlman (KlOa) also confirmed the correctness of Eq. (253) for Re,(a/ffo) < 0.25. (This is a particle Reynolds number based on sphere radius and mean shear rate, 1VJR , in the tube.)... 

The number-based mean radius 7p of the particle population is obtained by using the zerom and the first moment. 

This physical picture is reasonably consistent with the TEM micrograph shown in Fig. 11, although the estimate of the particle size is somewhat high. An overestimate of the particle size, based on Eq. 1, means that the surface area is less than that expected for particles of the equivalent spherical diameter observed by TEM. This indicates that the interparticle contacts are necked or deformed. According to Meissner et at. [14] the ratio of cavity radius to throat radius should equal about 1.4 for spheres compacted to a coordination number of about 8. The ratio obtained from values of the average pore sizes derived from the adsorption and desorption branches of the nitrogen isotherm was closer to 1.3, consistent with some interparticle neck formation. 

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