Question

Terminal velocity of the material is an important property for the design of

• A. Bucket elevators
• B. Belt conveyors
• C. Pneumatic conveyors
• D. Screw conveyors

Hint:

Conveying air velocity must be $1.5$ to $2.5$ times the particle terminal velocity in pneumatic conveying pipelines.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Terminal velocity is the steady-state settling velocity attained by a particle falling through a fluid when the net gravitational force equals the aerodynamic drag force.
Key Formula or Approach:
\[ v_t = \sqrt{\frac{2 m g (\rho_p - \rho_f)}{\rho_p \rho_f A C_d}} \]
\[ v_{\text{air, conveying}} > v_t \quad \text{(for vertical pneumatic transport)} \]

Step 2: Detailed Explanation:
In pneumatic conveying systems (and air aspirators winnowers), grain and particulate materials are transported suspended in high-velocity air streams.
The superficial air velocity in the duct must strictly exceed the terminal velocity (\(v_t\)) of the heaviest grain particle to ensure positive vertical transport and prevent clogging.

Step 3: Final Answer:
Thus, terminal velocity is an essential property for designing Pneumatic conveyors, corresponding to option (C).