Biochem - Agitation and Aeration [S1] Flashcards
(40 cards)
1
Q
- Swirling and vortex formation can be prevented by
A
- Using baffles
2
Q
- Power number is expressed as
A
- P0N3D02PN3D02PP0
3
Q
- The power consumption in a stirring vessel can be assessed by using a
A
- All of these
4
Q
- Surface renewal theory predicts that the mass transfer coefficient is
A
- Directly proportional to the square root of the molecular diffusivity
5
Q
- The oxygen transfer rate in a bioreactor will increase if
A
- Detergent-like molecules are added
6
Q
- Which of the following impellers are used for wide range of viscosities?
A
- Turbines
7
Q
- Which of the following type(s) of stirrer can be used for microbiological processes?
A
- All of these
8
Q
- The range of width for the baffle in the fermenter is times of vessel diameter.
A
- 1/10 to 1/12
9
Q
- The average concentration of oxygen in the boundary layers surrounding the bubbles (C0C0) in a reactor is normally determined by
A
- Measuring the steady state concentration of oxygen in the bulk liquid prior to inoculation of the reactor
10
Q
- Why vortexing is undesirable in the agitation of biological systems?
A
- All of the above
11
Q
- 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
A
- Bubble boundary layer
12
Q
- Penetration theory assumes that turbulent eddies travel from the bulk of the phase to the interface where they remain constant for a constant exposure time (tctc). The model correlationKLKLmass transfer coefficient andDABDAB, diffusivity can be expressed as
A
- KL=2(DABπtc)0.50KL=2(πtcDAB)0.50
13
Q
- The oxygen uptake requirements of a microbial population is characterized by the following parameters:μm=0.2 h−1μm=0.2h−1,K0=0.2 mgO2 L−1K0=0.2mgO2L−1,Y0=0.5 mgdryweight/mgO2Y0=0.5mgdryweight/mgO2andCocrit=0.8 mgL−1Cocrit=0.8mgL−1. The required concentration of cells is 1000 mg L−1−1and the saturation oxygen concentration of the medium is 5.8 mg L−1−1. The requiredKLaKLamust be greater than
A
- 64 h-1
14
Q
- Which have the maximum resistance while transferring carbon dioxide from the bulk liquid to an air bubble?
A
- Moving through the bubble boundary layer
15
Q
- If liquid density and viscosity remains constant, then the Reynolds number in a stirred tank reactor will vary with the
A
- Square of the impeller diameter
16
Q
- What is the ratio of depth of liquid in vessel to the diameter of tank (H:Dii)?
A
- 2:1
17
Q
- Radial flow impellers
A
- Both (a) and (b)
18
Q
- Transient flow range of mixing speed is obtained for
A
- 10<Ret<10410<Ret<104
19
Q
- A typical ceiling fan would be best described as a(n)
A
- Axial flow impeller
20
Q
- What is the ratio of diameter of impeller to the diameter of tank (Dss:Dii)?
A
- 1:3
21
Q
- The reason of using a flat disk in a Turbine is
A
- All of the above
22
Q
- Which of the following is not considered among the three best-known theories of interphase mass transfer?
A
- Calderbank and Moo-Young theory
23
Q
- Which of the following is most likely to cause an increase in the rate of oxygen transfer into a particular aerated fermentation system?
A
- Increase in stirrer speed
24
Q
- At 25°C, the saturation concentration of oxygen in water is 1.26 mmol/L and the partial pressure of oxygen is 1 atm. The Henry’s law constant will be
A
- 0.793 atm-L/mmol
25
25. Gas hold up, characterizing the hydrodynamics in a fermenter, mainly depends on the
25. Both (a) and (b)
26
26. Turbine impeller consists of flat impeller blades with
26. A vertical pitch welded to a horizontal disk
27
27. An aerated bioreactor will increase oxygen transfer rates with the addition of detergents because it
27. Discourages bubble coalescence
28
28. Vortexing in stirred tank reactors can be prevented by
28. Both (a) and (b)
29
29. Which of the following would be best described as an axial flow impeller?
29. Both (a) and (b)
30
30. Henry’s law relates
30. The partial pressure of oxygen and the saturation concentration of oxygen in the liquid
31
31. Power number is ratio of
31. Imposed forced to inertial force
32
32. The volume of liquid (VL) in a cylindrical reactor can be calculated from the liquid height (HL) and tank diameter (Dtt) using the following equation.
32. VL=HL×π×Dt24VL=HL×π×4Dt2
33
33. The average fractional gas hold up (H) can be given as (where Zff and Zll are the level of aerated and clear liquid respectively)
33. H=(Zf−Zl)/ZfH=(Zf−Zl)/Zf
34
34. Which of the following(s) is/are non-mechanically agitated reactors?
34. Both (b) and (c)
35
35. Which of the following best explains the reasons for using axial flow impellers in crystallization and precipitation reactions?
35. Axial flow impellers provide low shear, energy efficient mixing conditions
36
36. Which of the following will have the highest surface area available for oxygen transfer?
36. A sparge stirred tank reactor agitated at 400 rpm
37
37. A flooded impeller will lead to poor oxygen transfer rates because
37. Bubbles tend to coalesce under the impeller
38
38. Power consumption by agitation is
38. All of the above
39
39. Which of the following impellers will provide radial flow?
39. All of the above
40
40. When liquid is pumped through cooling coil in a stirred tank reactor to cool. Which of the following is not correct?
40. Faster cooling rates at a slower rate of pumping
