Jet-loop reactor hydrodynamics — The contents of a jet-loop (loop) bioreactor are primarily mixed by which means?

Introduction:
Jet-loop (also called jet-mixed or loop) reactors recirculate liquid through a nozzle to produce a high-velocity jet that entrains surrounding fluid, driving circulation through a draft tube or loop. The question checks recognition of the primary mixing mechanism.

Given Data / Assumptions:

• Jet created by external pump; optional gas entrainment.
• Loop or draft-tube geometry forms a defined circulation path.
• No central impeller is required in canonical designs.

Concept / Approach:
The key to a jet-loop reactor is momentum input from a pumped jet, not from a rotating impeller or mere aeration. The jet provides shear and bulk circulation, enhancing mass transfer while maintaining relatively simple internals.

Step-by-Step Solution:
1) A pump forces liquid through a nozzle, producing a jet at high velocity.2) The jet entrains surrounding liquid and gases (if present), increasing mixing and gas–liquid contact.3) The draft tube or loop geometry channels the flow, establishing a strong circulation pattern.4) Result: effective mixing and transfer without a mechanical agitator.

Verification / Alternative check:
Pilot designs demonstrate scalable circulation numbers tied to jet momentum rather than impeller tip speed, matching the description of externally pumped jets.

Why Other Options Are Wrong:

• (a) Pure aeration defines air-lift, not jet-loop, mixing.
• (b) Jet-loop reactors typically avoid impellers.
• (d) Designs are not agnostic; pumped jets are defining.
• (e) Thermal convection is negligible for industrial mixing needs.

Common Pitfalls:
Confusing jet-loop with air-lift; assuming any looped vessel uses an impeller; overlooking nozzle design and recirculation ratio roles.

Final Answer:
External liquid pumping through a nozzle to create a high-velocity jet