Packing coefficient, geometrical

The resistance coefficient i[f for a given packed bed, whose packing-specific geometric data a and e is known, can be determined for any given experimental data Apo/H and factor Fv using the transposed Eq. (3-8) ... 

The numerical Examples 3.2 and 4.2 illustrate how the approximation correlations (3-17) to (3-19) for converting the resistance coefficient and determining the pressure drop of MeUapak 250 Y can be applied to larger columns. In order to apply Eqs. (3-17), (3-18) and (3-19) to other packings, the geometric data of the respective packing, seal ring and column must be known. 

The other important factor is a, the geometric surface area exposed to gas per volume of reactor, which depends on the void fraction and the dimension of the packing. The product of the transfer coefficient and the surface-to-volume ratio governs the rate of heat and mass transfer per... 

The SEC partition coefficient [6] (.K sec) was measured on a Superose 6 column for three sets of well-characterized symmetrical solutes the compact, densely branched nonionic polysaccharide, Ficoll the flexible chain nonionic polysaccharide, pullulan and compact, anionic synthetic polymers, carboxylated starburst dendrimers. All three solutes display a congruent dependence of K ec on solute radius, R. In accord with a simple geometric model for SEC, all of these data conform to the same linear plot of i sEc versus R. This plot reveals the behavior of noninteracting spheres on this column. The mobile phase for the first two solutes was 0.2M NaH2P04-Na2HP04, pH 7.0. In order to ensure the suppression of electrostatic repulsive interactions between the dendrimer and the packing, the ionic strength was increased to 0.30M for that solute. 

The extended Navier-Stokes equation is solved on the geometrical domain illustrated in Fig. 5.12. Since the packed bed, the membrane, and the shell side are included in the calculation, boundary conditions do not have to be formulated explicitly at the interface (Goyeau et al, 2003). To account for the friction forces the following coefficients were substituted in Eq. (5.6) ... 

Stokes-Einstein relationship. Henry s law constant for CO2 in H2O equals 48.6 bar/kmol at 315 K [Danckwerts and Sharma, 1966]. This coefficient is corrected for the ionic strength of the solution [Danckwerts, 1970 Danckwerts and Sharma, 1966]. The geometric specific surface of the packing equals 105 mVmL The calculated results are summarized in Table 14.3.1.B-2. 

The interfacial area (a) is not the geometric surface area of the packing, but it is the mass transfer area between the gas and liquid phases. Thus, the product of a and AZ represents the total interfacial area within the entire packed bed. As stated in Chapter 3, the value of this interfacial area can be influenced by gas and liquid flow rates as well as the type and size of tower packing employed therefore, overall terms have been used. The interfacial area is combined with the liquid-phase mass transfer coefficient to produce an overall volumetric coefficient (Kj a). 

The method is developed in two variants differing in the kind of the laboratory column used. In die first one, this is a column with a single sphere [35, 36], and in the second - with a vertical column of spheres [37]. In both oases the mass transfer process is liquid-side controlled absorption. The method accepts that the mass transfer coefficients in a packing and on spheres are the same, and that the effective surfiice of the spheres is equal of dieir geometrical surfiice. Because the mass transfer coefficient depends on the hjrirodynamics of the liquid phase, and die hydrodynamics - on of die form of the packing, the first acceptation is doubtfiil. 

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