Agitation and Aeration – Section 1

6. Which of the following impellers are used for a wide range of viscosities?

A. paddles
B. turbines
C. propellers
D. none of these

Correct Answer: B. turbines

7. Which of the following type(s) of the stirrer can be used for microbiological processes?

A. Mig
B. Intermig
C. Turbine
D. All of these

Correct Answer: D. All of these

8. The range of width for the baffle in the fermenter is __________ times of vessel diameter

A. 1/10 to 1/12
B. 1/8 to 1/10
C. 1/5 to 1/8
D. none of these

Correct Answer: A. 1/10 to 1/12

9. The average concentration of oxygen in the boundary layers surrounding the bubbles (C0*) in a reactor is normally determined by

A. ultra-small dissolved oxygen probes
B. laser-based photographic systems
C. measuring the steady-state concentration of oxygen in the bulk liquid prior to inoculation of the reactor
D. measuring the steady-state concentration of oxygen in the bulk liquid after inoculation of the reactor

Correct Answer: C. measuring the steady-state concentration of oxygen in the bulk liquid prior to inoculation of the reactor

10. Why vortexing is undesirable in the agitation of biological systems?

A. The collision between the cells, impeller and air bubbles will lead to cell damage
B. Poor mixing despite the use of high stirrer speeds
C. Mixing will not be in the turbulent region
D. All of the above

Correct Answer: D. All of the above

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