Question

In pneumatic conveying and separation processes, the material is lifted only when the air velocity is greater than its

• A. Drag coefficient
• B. Bulk density
• C. Angle of repose
• D. Terminal velocity

Hint:

In pneumatic conveying, air velocity must be greater than the terminal velocity of the material to lift it.

Answer 1

The Correct Option is D

Step 1: Pneumatic conveying uses air stream to move agricultural materials like grains, seeds, and powders.

Step 2: For a particle to be lifted by air, the upward force due to air must overcome the downward weight of the particle.

Step 3: Terminal velocity is the air velocity at which the drag force on the particle balances its effective weight.

Step 4: If air velocity is less than terminal velocity, the particle will not be lifted properly.

Step 5: If air velocity is greater than terminal velocity, the particle can be lifted and conveyed by the air stream.

Step 6: Hence, in pneumatic conveying, material is lifted only when air velocity is greater than terminal velocity. \[ \boxed{\text{Terminal velocity}} \]