Agitation and Aeration problems
- 1. An aerated bioreactor will increase oxygen transfer rates with the addition of detergents because it
Options- A. enhances bubble coalescence
- B. causes bubbles to expand
- C. discourages bubble coalescence
- D. increases the surface tension of the liquid Discuss
Correct Answer: discourages bubble coalescence
- 2. The average fractional gas hold up (H) can be given as (where Zf and Zl are the level of aerated and clear liquid respectively)
Options- A. H = (Zf-Zl)/Zf
- B. H = Zf/Zl
- C. H = Zf/ZfZl
- D. H =(Zf+Zl)/Zf Discuss
Correct Answer: H = (Zf-Zl)/Zf
- 3. Vortexing in stirred tank reactors can be prevented by
Options- A. installing baffles in the reactor
- B. shifting the impeller to an off-centre position
- C. Both (a) and (b)
- D. using axial flow impellers Discuss
Correct Answer: Both (a) and (b)
- 4. A typical ceiling fan would be best described as a(n)
Options- A. radial flow impeller
- B. axial flow impeller
- C. intermig impeller
- D. Rushton turbine Discuss
Correct Answer: axial flow impeller
- 5. Which of the following is not considered among the three best-known theories of interphase mass transfer?
Options- A. two-film theory
- B. penetration theory
- C. surface renewal theory
- D. Calderbank and Moo-Young theory Discuss
Correct Answer: Calderbank and Moo-Young theory
- 6. Henry's law relates
Options- A. the partial pressure of oxygen and the saturation concentration of oxygen in the liquid
- B. the oxygen transfer rate and the bubble size
- C. the oxygen transfer rate and the temperature
- D. the oxygen transfer rate to the partial pressure of oxygen in the liquid Discuss
Correct Answer: the partial pressure of oxygen and the saturation concentration of oxygen in the liquid
- 7. Transient flow range of mixing speed is obtained for
Options- A. Rei<10
- B. 10<Rei<104
- C. Rei>104
- D. None of these Discuss
Correct Answer: 10<Rei<104
- 8. A flooded impeller will lead to poor oxygen transfer rates because
Options- A. bubbles tend to coalesce under the impeller
- B. bubbles tend to break down too rapidly under high shear conditions
- C. bubbles tend to move too quickly through the bulk liquid
- D. the cells clog up the surface of the bubble Discuss
Correct Answer: bubbles tend to coalesce under the impeller
- 9. Turbine impeller consists of flat impeller blades with
Options- A. a vertical pitch welded directly to the shaft
- B. a angled pitch welded directly to the shaft
- C. a vertical pitch welded to a horizontal disk
- D. a angled pitch welded to a horizontal disk Discuss
Correct Answer: a vertical pitch welded to a horizontal disk
- 10. The power consumption in a stirring vessel can be assessed by using a
Options- A. dynamometer
- B. strain gauge attached to agitator shaft
- C. watt meter attached to agitator motor
- D. all of these Discuss
Correct Answer: all of these
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