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- Question
The effect of increasing the stirrer speed in an unbaffled stirred tank reactor is that
Options- A. a small increase in stirrer speed will cause the liquid to enter the turbulent flow regime
- B. as the stirrer speed increases, the liquid will continue to circulate and then become turbulent
- C. as the stirrer speed increases, the liquid will continue to circulate. Eventually a vortex will form.
- D. A vortex will form at low stirrer speeds. As the stirrer speed increases the liquid will start to circulate
- Correct Answer
- as the stirrer speed increases, the liquid will continue to circulate. Eventually a vortex will form.
- 1. Which of the following will have the largest interfacial area per unit volume?
Options- A. A bubble with a diameter of 1 mm
- B. A bubble with a diameter of 5 mm
- C. A bubble with a diameter of 15 mm
- D. A bubble with a diameter of 50 mm Discuss
- 2. For turbulent flow, Reynolds number is correlated with power number as (where K, a constant which depends on the container geometry and shape of stirrer; Rei, is Reynolds number for agitator; Di, stirrer diameter and N, stirrer speed)
Options- A. Np = K(Rei)-1
- B. Np = N2Di(Rei)-1
- C. Np = K
- D. Can't be correlated Discuss
- 3. In a two-phase system where the continuous phase remains in place, the gas hold up can be expressed as (where Vs and Vt are the superficial gas velocity and bubble rise velocity)
Options- A. H = Vs/(Vs-Vt)
- B. H = Vs/(Vs+ Vt)
- C. H = Vs/(Vs.Vt)
- D. H = (Vs+Vt)/Vs Discuss
- 4. In a bioreactor, if at a particular time the oxygen transfer rate is 23 kg.h-1, then the oxygen uptake will be
Options- A. 23 kg.h-1
- B. less than 23 kg.h-1
- C. greater than 23 kg.h-1
- D. 2.3 kg.h-1 Discuss
- 5. The advantage of axial flow impellers over radial flow impellers is that axial flow impellers
Options- A. provide better lift of solids
- B. provide high shear conditions
- C. provide low shear conditions
- D. are cheaper to build Discuss
- 6. Bioreactors, where vortex is formed, another dimensionless number, __________ is useful.
Options- A. Stanton
- B. Rayleigh
- C. Bond
- D. Froude Discuss
- 7. Turbulent flow range of mixing speed is obtained for
Options- A. Rei<10
- B. 10<Rei<104
- C. Rei>104
- D. None of these Discuss
- 8. Which device is commonly used for measuring the rate of rotation (rpm) of the stirrer shaft?
Options- A. Anemometer
- B. Manometer
- C. Tachometer
- D. Barometer Discuss
- 9. Axial flow impellers
Options- A. provide high shear conditions for breaking up bubbles
- B. provide low shear conditions and are suited for use in shear sensitive procesess
- C. provide direct flow towards the walls of the reactor
- D. none of the above Discuss
- 10. If the stirring speed increased from 300 to 500 rpm leads to an increase in the reaction rate by two folds. Then it may be concluded that
Options- A. the reaction was mass transfer limited at 300 rpm
- B. the reaction was mass transfer limited at 500 rpm
- C. the reaction did not involve any mass transfer step
- D. the movement of molecules in the reactor at 300 rpm occurred due to diffusion alone Discuss
Agitation and Aeration problems
Search Results
Correct Answer: A bubble with a diameter of 1 mm
Correct Answer: Np = K
Correct Answer: H = Vs/(Vs+ Vt)
Correct Answer: 23 kg.h-1
Correct Answer: provide better lift of solids
Correct Answer: Froude
Correct Answer: Rei>104
Correct Answer: Tachometer
Correct Answer: provide low shear conditions and are suited for use in shear sensitive procesess
Correct Answer: the reaction was mass transfer limited at 300 rpm
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