Mixing tank internals: as a preliminary design rule for baffled cylindrical vessels, the total baffle width is typically selected as what fraction of the tank diameter?

Introduction / Context:Baffles suppress vortex formation and convert swirling into efficient top-to-bottom circulation in stirred tanks. Correct baffle sizing is essential to achieve target mixing times and reliable scale-up. A common rule-of-thumb specifies baffle width as a fraction of tank diameter.

Given Data / Assumptions:

• Baffled, cylindrical stirred tank with four flat baffles.
• General-purpose mixing (not special viscous or gas–liquid exceptions).
• Looking for standard preliminary proportioning.

Concept / Approach:Standard practice sets individual baffle width at roughly 0.1–0.12 of the tank diameter. This provides strong flow disruption without excessive blockage or power draw. Smaller baffles may permit vortexing; much larger baffles can increase power requirements and hinder flow around the tank periphery.

Step-by-Step Solution:

Verification / Alternative check:Vendor guidelines and mixing handbooks align with w/d ≈ 0.1–0.12 for standard turbulent mixing.

Why Other Options Are Wrong:

• 0.2–0.45 or higher values are unusually large and increase blockage and power.
• Very small values (0.02–0.05) are ineffective at suppressing swirl.

Common Pitfalls:Using the same baffle width for highly viscous systems; not accounting for nozzle intrusions or internals that already impede swirl.

Final Answer:0.1–0.12