AECH 4210 Mass Transfer Fundamentals

What does interphase mass transfer depend on?

Which of the following is an example of interphase mass transfer?

What is typically assumed at the interface during steady-state conditions?

What does the Lewis-Whitman two-film model describe?

In the context of interphase mass transfer, what happens to gas molecules at the interface?

Which process illustrates how language barriers can resemble gas-liquid transfer?

Which scenario best depicts the concentration gradient concept in mass transfer?

During the mass transfer process, what is mainly transported through the two layers in the Lewis-Whitman model?

What primarily drives mass transfer through diffusion?

Which of the following is an example of eddy diffusion?

What distinguishes convection mass transfer from diffusion mass transfer?

What is a key characteristic of forced convective mass transfer?

How does the rate of diffusion mass transfer compare to convection mass transfer?

Which scenario best exemplifies free convective mass transfer?

What analogy is used to describe the relationship between diffusion and convection mass transfer processes?

What role does turbulence play in mass transfer processes?

Modes of Mass Transfer

Mass transfer occurs through diffusion, which can be molecular or eddy-based, driven by concentration differences.
Molecular diffusion involves the transfer of substances through a stagnant layer of fluid, whereas eddy diffusion happens in a turbulent flow.
Eddy diffusion is generally more efficient than molecular diffusion, as seen in example scenarios like the dispersion of purple dye in water or smoke from a stack.

Mass Transfer by Convection

Convection refers to large-scale mass transfer resulting from the bulk movement of fluids, influenced by transport properties and flow dynamics.
Free convective mass transfer occurs due to buoyancy, such as ether evaporation.
Forced convective mass transfer is enhanced by external forces (e.g., fans or pumps), exemplified by wind rapidly transporting water particles on a lake's surface.

Comparisons of Mass Transfer Processes

Diffusion mass transfer operates slowly, limiting its effectiveness for large-scale processes.
In contrast, convection mass transfer is much faster and suitable for significant transfers, akin to a train's speed compared to a turtle's.
Both convection and diffusion processes coexist, with convection overshadowing diffusion.

Interphase Mass Transfer

Interphase transfer relies on molecules migrating between distinct phases, influenced by disparities in physical and chemical properties like vapor pressure or solubility.
A concentration gradient exists between the bulk fluid and the interface, with equilibrium often assumed at steady states.
Examples include the absorption of ammonia by water, CO2 from flue gas by amine solvents, and H2S from natural gas.

Two-Film Theory

The Lewis-Whitman two-film model describes mass transfer with gas-liquid interfaces, highlighting double layers through which diffusion occurs.
This model illustrates the complexities of communication between two languages, where barriers slow down interaction, analogous to gas transferring through molecular layers at an interface.

Explore the principles of mass transfer and separation processes in this quiz based on AECH 4210. Topics include modes of mass transfer such as molecular and eddy diffusion, as well as the significance of concentration differences. Test your understanding of how these processes operate at both microscopic and macroscopic levels.