ADVANCED MASS TRANSFER

Amirkabir University of Technology

(Tehran Polytechnic)

Winter 2009

Chemical Engineering Department

By: Dr. Frazin Zokaee

By Dr. Zokaee

Course Outline:

CHAPTER 1: FLUX DEFINITION• Flux Definition

• Mass and Molar Transport by Convection

• Summary of Mass and Molar Fluxes

• Fick’s Law

CHAPTER 2: DIFFERENTIAL EQUATIONS OF MASS TRANSFER• Differential equation for mass transfer

• Boundary conditions

CHAPTER 3: MOLECULAR DIFFUSIVITIES• Diffusivities in Gases

• Diffusivities in Liquids

CHAPTER 4: MOLECULAR DIFFUSION

• Steady-State Molecular Diffusion

• Steady-State Equimolal Counter Diffusion in Gases

• Steady-State Unimolal Unidirectional Diffusion in Gases

• Molecular Diffusion in Liquids

• Diffusion through a Stagnant Gas Film

• Diffusion with a Moving Interface

• Diffusion through a Nonisothermal Spherical Film

• Diffusion with a Heterogeneous Chemical Reaction

• Diffusion with a Slow Heterogeneous Reaction

• Diffusion with a Homogeneous Chemical Reaction

• Unsteady-State Diffusion in a Sphere

• Unsteady-State Diffusion in a Slab

• Unsteady-State Diffusion in a Cylinder

By Dr. Zokaee

CHAPTER 5: MECHANISMS OF MASS TRANSFER

• The Two-Film Theory

• The Penetration Theory

• The Theory of Penetration with Random Surface Renewal

CHAPTER 6: MASS TRANSFER IN LAMINAR FLOW

• Mass Transfer in the Laminar Boundary Layer on a Flat Plate (Integral Solution)

• Mass Transfer in Laminar Natural Convection on a Vertical Plate

• Mass Transfer in a Falling Liquid Film in Laminar Flow

o Mass Transfer Between a Gas Phase and a Falling Liquid Film (Gas Absorption)

o Mass Transfer Between an Inclined Plate and a Falling Liquid Film(Solid Dissolution)

o Gas Absorption with Rapid Reaction

By Dr. Zokaee

CHAPTER 7: MASS TRANSFER IN TURBULENT FLOW

• Mass Transfer in the Turbulent Boundary Layer on a Flat Plate

• Mass Transfer in Turbulent Natural Convection on a Vertical Plate

• Mass Transfer Between an Inclined Plate and a Falling Liquid Film in Turbulent Flow

• Analogies Between Momentum, Heat and Mass Transfer

o Reynolds Analogy: Analogy Assuming Only a Turbulent Core

o Prandtl Analogy: Analogy Assuming a Laminar Sublayer and a Turbulent Core

o Von karman Analogy: Analogy Assuming a Laminar Sublayer, a Buffer Zone and a Turbulent Core

o Analogies in terms of j Factors

By Dr. Zokaee

Text Book

• R.B. Bird, W.E. Steward and E.N. Lightfoot, Transport Phenomena, 2nd Ed.,

John Wiley and Sons (2002).

• J. R. Welty, C. E. Wicks, R. E. Wilson and G. Rorrer, Fundamentals of

Momentum, Heat, and Mass Transfer, 4th Ed., John Wiley & Sons (2001).

•A. H. P. Skelland, Diffusional Mass Transfer, John Wiley and Sons (1974).

By Dr. Zokaee

What is Mass Transfer?

• The transport of one component from one place to another is called Mass Transfer.

Must have a mixture of two or more species for mass transfer to occur.

• Diffusional Mass Transfer involves the migration of one substance through another under the influence of a concentration gradient .

• Motion of molecular or fluid elements caused by some form of potential or driving force is called Mass Transfer.

By Dr. Zokaee

• Separation processes

Single phase

Between two phase

Direct contact

Indirect contact

Gas - Liquid

Gas - Solid

Liquid - Liquid

Liquid - Solid

– Absorption– Stripping

– Distillation

– Evaporation

– Humidification

– Dehumidification

– Adsorption

– Desorption

– Drying

– Sublimation

– Adsorption

– Desorption

– Leaching

– Crystallization

– Liquid-Liquid Extraction

Membrane separation

By Dr. Zokaee

• Types of Membrane

Porous membrane Dense membrane

– Solid diffusion

i i iP D

iP Permeability

By Dr. Zokaee

• Driving force in Membrane separation

Pressure gradient (∆P)

Concentration gradient (∆C)

Electric gradient (∆E)

Temperature gradient (∆T)

– Microfiltration

– Ultrafiltration

– Reverse Osmosis

– Nanofiltration

– Dialysis

– Pervaporation

– Gas Permeation

– Liquid Membrane

– Electro Dialysis (ED)

– Membrane Distillation

By Dr. Zokaee

• Mechanical Separation

Mechanical work and calculations are according the fluid flow in porous media and centrifugal force and etc.

– Mixing

– Size reduction

– Sedimentation

– Centrifugation

– Filtration

By Dr. Zokaee

• Separation processes

Continues

Stage wise

– Packed towers

– Spray towers

– Bubble column

– Wetted wall column

– Tray towers

– Mixer and Settler

By Dr. Zokaee