Agitation and Aeration problems
- 1. The rate limiting step in the movement of oxygen from the gas phase in a bubble to the cell is the movement of oxygen molecules through
Options- A. gas-liquid interface
- B. bubble boundary layer
- C. bulk liquid
- D. gas phase Discuss
Correct Answer: bubble boundary layer
- 2. Swirling and vortex formation can be prevented by
Options- A. using baffles
- B. using diffusion ring with turbines
- C. both (a) and (b)
- D. none of these Discuss
Correct Answer: both (a) and (b)
- 3. Gas hold up, characterizing the hydrodynamics in a fermenter, mainly depends on the
Options- A. superficial gas velocity
- B. power consumption
- C. Both (a) and (b)
- D. gas concentration Discuss
Correct Answer: Both (a) and (b)
- 4. When liquid is pumped through cooling coil in a stirred tank reactor to cool. Which of the following is not correct?
Options- A. If the stirrer speed is increased, the rate will be faster
- B. Baffles in the tank will increase the rate of cooling
- C. Faster cooling rates at a slower rate of pumping
- D. Faster cooling rates at a faster rate of pumping Discuss
Correct Answer: Faster cooling rates at a slower rate of pumping
- 5. If liquid density and viscosity remains constant, then the Reynolds number in a stirred tank reactor will vary with the
Options- A. impeller diameter
- B. square root of the impeller diameter
- C. square of the impeller diameter
- D. cube of the impeller diameter Discuss
Correct Answer: square of the impeller diameter
- 6. The oxygen uptake requirements of a microbial population is characterized by the following parameters: ?m = 0.2 h-1, K0 = 0.2 mg O2.l-1, Y0 = 0.5 mg dry weight/mg O2 and C0,crit=0.8 mg.l-1 The required concentration of cells is 1000 mg.l-1 and the saturation oxygen concentration of the medium is 5.8 mg.l-1. The required KLa must be greater than
Options- A. 64 h-1
- B. 32 h-1
- C. 16 h-1
- D. 8h-1 Discuss
Correct Answer: 64 h-1
- 7. Radial flow impellers
Options- A. provide high shear conditions for breaking up bubbles
- B. direct flow towards the walls of the reactor
- C. Both (a) and (b)
- D. provide low shear conditions and are suited for use in shear sensitive procesess Discuss
Correct Answer: Both (a) and (b)
- 8. What is the ratio of diameter of impeller to the diameter of tank (Da:Dt)?
Options- A. 1 : 3
- B. 2 : 1
- C. 4 : 1
- D. 1 : 5 Discuss
Correct Answer: 1 : 3
- 9. The volume of liquid (VL) in a cylindrical reactor can be calculated from the liquid height (HL) and tank diameter (Dt) using the following equation
Options- A. VL = 4/3 x ? x HL x Dt3/8
- B. VL= HL x ? x Dt2/4
- C. VL= HL x ? x Dt2
- D. VL = 4 x ? x Dt2 Discuss
Correct Answer: VL= HL x ? x Dt2/4
- 10. Which of the following impellers are used for wide range of viscosities?
Options- A. paddles
- B. turbines
- C. propellers
- D. none of these Discuss
Correct Answer: turbines
Programming
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