Diffusion and Mass Transfer Coefficients

Finally, the liquid-phase diffusivities and mass-transfer coefficients are related, as a consequence of equation 9.2-7, by... 

In order to calculate the multicomponent diffusion matrices [D], the binary diffusivities in both phases should be known. The him thickness representing an important model parameter is estimated via the mass transfer coefficients (57,83). The binary diffusivities and mass transfer coefficients were calculated from the correlations summarized in Table 3. 

Table 9.3. Binary diffusion and mass transfer coefficients.

Of the parameters making up the Hatta number, liquid diffusivity and mass-transfer coefficient data and measurement methods are well reviewed in the literature. 

This part of Sec. 5 provides a concise guide to solving problems in situations commonly encountered by chemical engineers. It deals with diffusivity and mass-transfer coefficient estimation and common flux equations, although material balances are also presented in typical coordinate systems to permit a wide range of problems to be formulated and solved. 

Johansson L and Lofroth JE. Diffusion and interactions in gels and solution. I. Method. J. Colloid Interface Sci. 1991 142 116-120. Inoue SK, Guenther RB, and Hoag SW. Algorithm to determine diffusion and mass transfer coefficients. Proceedings of the Conference on Advances in Controlled Delivery, Baltimore (USA), August 19-20, 1996, pp. 145-146. 

Solute Diffusion and Mass-Transfer Coefficients For a binary system consisting of components A and B, the overall rate of mass transfer of component A with respect to a fixed coordinate is the sum of the rates due to diffusion and bulk flow ... 

The pore diffusivity and mass transfer coefficient are constant... 

Since in the limit of infinite dilution Ya = EQs. fl5-59i require that the infinite dilution limits of the Maxwell-Stefan and the Fickian diffusivities and mass-transfer coefficients are equal. 

If pore diffusion affects the reaction rate and Rj in Equation 6.14 is replaced by r ejRp the effectiveness factor, ejy can be obtained the same way as in the case of catalytic two-phase reactions (Section 5.2.2). Equations developed for two-phase reactions in Section 5.2.2 are also valid for three-phase cases, provided that the catalyst particles are completely wetted by the liquid. In this case, we only have one phase a liquid present inside the catalyst pores. Using the formulae introduced in Section 5.22, the diffusion and mass transfer coefficients of the gas phase are, of course, replaced by those of the liquid phase. 

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