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Home
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Biochemical Engineering
‣
Agitation and Aeration
Comments
Question
The main function of the dimples provided in the cooling jacket is to
Options
A. increase the level of turbulence of the cooling water in the jacket
B. increase the residence time of the cooling water in the jacket
C. increase the cooling water-jacket wall boundary layer size
D. all of the above
Correct Answer
increase the level of turbulence of the cooling water in the jacket
Agitation and Aeration problems
Search Results
1. Which of the following number is calculated from the diameter and peripheral speed of the impeller?
Options
A. Reynolds number
B. Froude number
C. Power number
D. None of these
Show Answer
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Discuss
Correct Answer: Reynolds number
2. Which of the following impeller is used in situation where strong vertical currents are desirable for suspending heavily particles?
Options
A. Propeller
B. Paddle
C. Turbine
D. None of these
Show Answer
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Correct Answer: Propeller
3. 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
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Correct Answer: the reaction was mass transfer limited at 300 rpm
4. 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
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Correct Answer: provide low shear conditions and are suited for use in shear sensitive procesess
5. 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
Show Answer
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Correct Answer: Tachometer
6. A higher liquid height will lead to a higher gas hold up by which the oxygen transfer rate will be
Options
A. higher throughout the reactor
B. lower throughout the reactor
C. higher at the base of the reactor
D. lower at the base of the reactor
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Correct Answer: higher at the base of the reactor
7. In a tall reactor, oxygen transfer rates will be
Options
A. highest at the surface of the reactor
B. highest at the base of the reactor
C. highest in the middle of the reactor
D. the same throughout the reactor
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Correct Answer: highest at the base of the reactor
8. Oxygen transfer rate is increased with an increase in the stirrer speed in aerated bioreactor because
Options
A. it decrease the bubble size
B. it decreases the size of the boundary layer surrounding a bubble
C. it increases the rate of movement of oxygen molecules through the bulk liquid
D. all of the above
Show Answer
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Correct Answer: all of the above
9. An increase in the heat transfer in the stirred tank reactor will be observed at
Options
A. higher cooling water temperature
B. higher stirrer speed
C. the removal of baffles from the reactor
D. slower stirrer speed
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Correct Answer: higher stirrer speed
10. For laminar flow, Reynolds number is correlated with power number as (where
K
, a constant which depends on the container geometry and shape of stirrer;
Re
i
is Reynolds number for agitator;
D
i
, stirrer diameter and
N
, stirrer speed)
Options
A.
N
p
=
K(Re
i
)
-1
B.
N
p
=
N
2
D
i
(Re
i
)
-1
C.
N
p
=
K(Re
i
)
D.
N
p
=
KND
i
(Re
i
)
-2
Show Answer
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Discuss
Correct Answer:
N
p
=
K(Re
i
)
-1
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