Mass transfer in packed beds

Little work has been reported on mass transfer between non-Newtonian fluids and particles in a fixed bed. Kumar and Upadhyay [1981] measmed the rate of dissolution of benzoic acid spheres and cylindrical pellets in an aqueous carboxymethyl cellulose solution (n = 0.85) and, using the plug flow model, proposed the following correlation for mass transfer in terms of the jm factor  

No analogous heat transfer studies have been reported with non-Newtonian fluids. 

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N. Wakao, Heat and Mass Transfer in Packed Beds, Gordon Breach, New York, 1982. 

Effects of Temperature on tiQ and tii The Stanton-number relationship for gas-phase mass transfer in packed beds,... 

A. Heat or mass transfer in packed bed for gases and liquids... 

Glaser and Thodos [Am. Jn.st. Chem. Eng. J., 4, 63 (1958)] give a correlation involving individual particle shape and bed porosity. Kunii and Suzuki [Jnt. ]. Heat Mass Tran.sfer, 10, 845 (1967)] discuss heat and mass transfer in packed beds of fine particles. 

H. Martin 1978, (Low Peclet number particle-to-fluid heat and mass transfer in packed beds), Chem. Eng. Sci. 33, 913-919. 

Single-Phase Mass Transfer in Packed Beds... 

Equation 6.28 [8] can correlate well the data of many investigators for gas or liquid film mass transfer in packed beds for the ranges of (Re) from 10 to 2500, and of (Sc) from 1 to 10 000. 

Free Iiquid-to-gas mass-transfer in packed beds... 

N.Wakao and S.Kaguei, Heat and mass transfer in packed beds, Gordon and Breach, New york 1980... 

Heat and Mass Transfer in Packed Beds, NWakao S Kaguei Three-Phase Catalytic Reactors, P A Ramachandran R V Chaudari Drying Principles, Applications and Design, by Cz Strumillo T Kudra... 

Volume 1 HEAT AND MASS TRANSFER IN PACKED BEDS by N. Wakao and S. Kaguei... 

Empirical relationships of similar form for mass transfer in packed beds, to falling spheres, to flat plates, and other relevant geometries are given in several excellent text books [48-51]. 

Effects of Temperature on kG and k, The Stanton-number relationship for gas-phase mass transfer in packed beds, Eq. (5-301), indicates that for a given system geometry the rate coefficient kG depends only on the Reynolds number and the Schmidt number. Since the Schmidt number for a gas is approximately independent of temperature, the principal effect of temperature upon kG arises from changes in the gas viscosity with changes in temperature. For normally encountered temperature ranges, these effects will be small owing to the fractional powers involved in Reynolds-number terms (see Tables 5-17 to 5-24). It thus can be concluded that for all... 

External Fluid Film Resistance. A particle immersed in a fluid is always surrounded by a laminar fluid film or boundary layer through which an adsorbing or desorbing molecule must diffuse. The thickness of this layer, and therefore the mass transfer resistance, depends on the hydrodynamic conditions. Mass transfer in packed beds and other common contacting devices has been widely studied. The rate data are normally expressed in terms of a simple linear rate expression of the form... 

As explained above, cocurrent gas-liquid flow in packed beds, packing being either catalytic or inert, is advantageously employed in the petroleum and chemical industries. Successful modeling of mass transfer in packed-bed reactors requires careful study of the three-phase hydrodynamics— fluid flow patterns, pressure drops, and liquid holdup. 

P. W. Appel, Electrochemical Systems Impedance of a Rotating Disk and Mass Transfer in Packed Beds, Ph.D. dissertation. University of California, Berkeley, Berkeley, California (1976). 

MASS TRANSFER IN PACKED BEDS. There have been a great many studies of mass transfer and heat transfer from gases or liquids to particles in packed beds. The coefficients increase with about the square root of the mass velocity and the two-thirds power of the diffusivity, but the correlations presented by different workers differ appreciably, in contrast to the the close agreement found in studies of single spheres. An equation that fairly well represents most of the data is ... 

To compare mass transfer in packed beds with transfer to a single particle, Sherwood numbers calculated from Eq. (21.62) are plotted in Fig. 21.5 along with the correlation for isolated spheres. The coefficients for packed beds are two to three times those for a single sphere at the same Reynolds number. Most of this difference is due to the higher actual mass velocity in the packed bed. The Reynolds number is based for convenience on the superficial velocity, but the average mass velocity is Gfe, and the local velocity at some points in the bed is even higher. Note that the dashed lines in Fig. 21.5 are not extended to low values of since it is unlikely that the coefficients for a packed bed would ever be lower than those for single particles. 

The macroporous structure of monoliths allows the overcoming of some of the disadvantages of conventional affinity chromatographyt . Monoliths have lower mass transfer resistance and pressure drop than conventional random packed beds, and mass transfer within monolith channel rates can be substantially larger than mass transfer in packed beds used in conventional chromatography. 

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