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Renin Angiotensin Mechanism.

Mixing: Mechanisms of Mixing.

 

Definition

  • Mixing is defined as an unit operation in which two or more components are treated in such a way  that each particle / molecule of the components lies as nearly as possible in contact with a particle / molecule of the other components.

  • If this is achieved it produces a theoretical ‘ideal’ situation, called a perfect mix.


Mechanisms of mixing:

Mechanisms of Solid Mixing:

  • Solids are mixed using three mechanisms as follows,

    1. Convective Mixing.

    2. Shear Mixing.

    3. Diffusive Mixing.

  1. Convective Mixing:

  1. Also called “Macromixing”.

  • Involves transfer of a group of particles from one part of a powder bed to another part.

  1. Shear Mixing:

    • Formation of shear forces by using an agitator arm or a blast of air causes movement of particles.

  2. Diffusive Mixing: 

    • Also called “Micromixing”.

    • Involves distribution of particles over a newly formed surface.

    • In this the material is tilted causing the upper surface to come down due to gravity while smaller particles diffuse to the upper layer.

Mechanisms of Liquid Mixing:

  • The liquids are mixed by one or more than one of the following mechanisms,

    1. Bulk Transport.

    2. Turbulent Mixing.

    3. Laminar Mixing.

    4. Molecular Diffusion.

  1. Bulk Transport:

    • Involves movement of a large part of the system to another part.

    • Can be achieved using paddles and blades.

  2. Turbulent Mixing:

    • Mixing takes place due to the formation of turbulent flow.

    • In turbulent flow various smaller currents of different velocities are formed which further form smaller currents.

    • Due to this formation of dividing currents, the particle mixing takes place very efficiently.

    • Highly effective mechanism of mixing.

  3. Laminar Mixing:

    • Associated with highly viscous liquids.

    • The shear force is created which breaks the liquid interface allowing movement of particles between the liquid bodies.

  4. Molecular Diffusion:

    • Mixing takes place at molecular levels.

    • Diffusion of molecules takes place due to thermal motions of the particles.

    • This process can be described quantitatively by “Fick’s Law of Diffusion” which depends on the concentration gradient at different points.

Mechanisms of Semisolid Mixing:

  • The mechanisms involved depend on the nature of materials.

  • The more liquid material will follow mechanisms of liquid mixing while more solid material will follow mechanisms of solid mixing.

Commonly Asked Questions.

  1. Define Mixing. Write a note on mechanisms of Mixing.
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