Diameter surface-volume

The definition of the surface-volume mean diamefer given by equation 1.11 must be modified for use wifh dafa from a sieve analysis. By assuming that the shape and density of fhe particles are constant for all size fractions, a number distribution can be transformed fo a mass distribution (Smith, 2003) and therefore the surface-volume diameter becomes... 

Abbreviations, d y, surface volume diameter dy, volume diameter dp, projected diameter = 0.99y/L.W. S, surface area of pellet V, volume of pellet R, ratio of max. diameter dmax to min. diameter dmin- M, ratio of width (W) to depth (X) of particle K-S,y, specific surface area , obtained by microscopy. 

Geldart found that the above classification could be charted quantitatively by two variables the effective density of the particles (ps — p ), and their average surface-volume diameter dav, as shown in Fig. 63a. In Geldart s original chart for air, the boundary between Groups A and C is empirically determined and consists of a rather diffuse belt. The boundary between A and B is defined by the relation... 

Since the surface-volume diameter is inversely proportional to S, the constant of proportionality being a minimum of six for spherical particles, Martin s diameter is systematically different to the surface-volume diameter. Experiments confirm that, on the whole, d/ shape function. For example dp/dj = 1.2 for Portland cement and 1.3 for ground glass [65]. 

Vice versa, starting from the specific surface of a foamed polymer one can find the geometrical size of the constituent cells. Indeed, in those rare cases where the real cellular foam structure may be represented by sphere of the same size, the diameter of the spheres can be easily calculated from Eq. (58) . In the case of more irregular structures, the diameter given by this formular is a mean surface-volume diameter . 

There is a wide variety of methods for particle size measurement which measure different types of particle size. When selecting a method, it is best to take one that measures the type of size which is most relevant to the property or the process which is under study. Thus, for example, in powder elutriation, pneumatic conveying or gas cleaning, it is most relevant to use one of the sedimentation methods which measure the Stokes diameter, i.e. the diameter of a sphere of the same density as the particle itself, which would fall in the gas at the same velocity as the real particle (assuming Stokes law). In flow through packed or fluidized beds, on the other hand, it is the surface-volume diameter (or diameter... 

SPHERICITY is the ratio of the surface area of a sphere having the same volume as the particle, to the actual particle surface area the reciprocal is known as the coefficient of rugosity or angularity. It can be shown that sphericity is also equal to the ratio of the surface-volume diameter to the equivalent volume diameter this makes sphericity a useful conversion factor between... 

Surface Volume Diameter Diameter of a sphere having the same external surface area to volume ratio as the particle... 

What is the surface area of coal with a sphericity of 0.75 and a volume of 1.5 mm Calculate the surface-volume diameter (A. Benamer). 

Typical distribution of droplet size for anticorrosive paint based on zinc phosphate is shown in Figure 10.6. The symbol da identifies here the median diameter (midpoint of the size distribution) and dsv is the surface volume diameter, i.e., diameter of the sphere having the same ratio of surface area-to-volume as the droplet, and calculated as... 

The validity of Princen s theory for concentrated water-in-oil emulsions was also investigated by Ponton et al. (2001), using the droplet size distribution determined by laser diffractometry based on the Mie theory model. Comparing the surface-volume diameter and the mass fractions of emulsions depicted an increase in the particle size with the volume fraction reduction. They showed that their experimental data (as obtained by oscillatory measurements and droplet-size distribution) corroborated the expression of the elastic shear modulus for the two-dimensional model proposed by Princen and Kiss (1986). In this model, G is proportional to (a/Rsv) l v ( l v- l c) where a is the interfacial tension, Rsv is the volume-surface radius (as obtained by laser diffractometry), and Oy and Oc are the volume fraction and the critical volume fraction, respectively (Ponton et al. 2001). The latter was found to be 0.714 experimentally, which is close to the value obtained by Princen ( 0.712) (Ponton et al. 2001). 

Av Surface volume diameter Surface-to-volume ratio... 

In cake filtration, where the surface volume diameter is of interest, methods for surface area determination are relevant (these measure only mean sizes) particularly, permeametry, gas diffusion and hindered settling methods. 

The volume equivalent sphere diameter or equivalent volume sphere diameter is a commonly used equivalent sphere diameter. We will see later in the chapter that it is used in the Coulter counter size measurements technique. By definition, the equivalent volume sphere diameter is the diameter of a sphere having the same volume as the particle. The surface-volume diameter is the one measured when we use permeametry (see Section 1.8.4) to measure size. The surface-volume (equivalent sphere) diameter is the diameter of a sphere having the same surface to volume ratio as the particle. In practice it is important to use the method of... 

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