What is the ideal tubular-flow fermenter model (no radial gradients, no axial mixing) commonly called in biochemical engineering?

Introduction / Context:
Fermenter hydrodynamics are frequently idealized as either perfectly mixed tanks or plug flow tubes. The chosen model affects predicted conversions, selectivities, and scale-up strategies.

Given Data / Assumptions:

• Tubular flow without radial gradients.
• Negligible axial dispersion (no backmixing).
• Steady operation.

Concept / Approach:
These assumptions define a plug flow device. In biochemical engineering contexts, the term “plug flow fermenter” mirrors the chemical engineering “PFR” and is contrasted with the “CSTR” (continuous stirred tank fermenter).

Step-by-Step Solution:

Verification / Alternative check:
Residence-time distribution tests for an ideal PFR yield a narrow distribution; CSTRs show exponential RTD, confirming model differences.

Why Other Options Are Wrong:

• CSTF: represents perfect mixing, not plug flow.
• Column fermenter: geometry only; flow may be mixed or dispersed.
• High-dilution/washout: an operating condition, not a hydrodynamic model.
• Batch bubble column: unsteady, gas–liquid mixing; not plug flow by default.

Common Pitfalls:
Equating vessel geometry with hydrodynamics; true plug flow is a kinetic idealization, not guaranteed by a cylindrical shape.

Final Answer:
Plug flow fermenter