FILM THEORY

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Facultad de Ingeniería Química Fenómenos de Transporte I FILM THEORY Alcalá García Edghar Enrique 201515099 Profr. Rafael Flores García Cuarentena 2020

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Índice

Contenido Aplicaciones de la difusión molecular ........................ ¡Error! Marcador no definido. Ejemplo: ......................................................................... ¡Error! Marcador no definido. Consideración: .............................................................. ¡Error! Marcador no definido. BIBLIOGRAFÍA .............................................................. ¡Error! Marcador no definido.

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INTRODUCTION TO FILM THEORY 3|Page

GRAPHIC PROCESS DESCRIPTION

Film model for transfer in phase x. Turbulent eddies wipe out composition gradients in the bulk fluid phase. Composition variations are restricted to a layer (film) of thickness

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FILM MODEL FOR BINARY MASS TRANSFER Considering a planar film between the position coordinates r = r0 and r = r8. Mass transfer between the two edges of the film occurs purely by molecular diffusion under steady-state conditions. The thickness of the film is f = r8 - r0. The equation of continuity of moles of species, can be written for species 1 and 2 as:

showing that Nv N2, and Nt (= Nx + N2) are r invariant. The generalized Maxwell-Stefan diffusion equations (Eq. 2.2.1) simplify to

where D = BY is the Fick diffusion coefficient. Re writting

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To carry out the hydrodynamic resolution we must consider the following points:

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A dimensionless distance

Where ℓ is the thickness of the diffusion layer or "film"

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A dimensionless mass transfer rate factor

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With these definitions Equatión may be written as

The linear differential equation can be integrated to give the composition profiles:

The diffusion flux at η = 0, J10, is given by

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Correction Factors

High flux correction factor from film theory

with the correction factors given by

The final equation for solve cases is:

Various special cases of this result can now be identified.

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