Exercise: Agitation And Aeration
Questions for: Agitation And Aeration
What is the effect of the concentration of dissolved salts and sugars on the oxygen transfer rate?
A:
The saturation concentration of oxygen in the medium decreases with the concentration of dissolved salts and sugars, leading to a lower oxygen transfer rate
B:
The KLa of the medium decreases with the concentration of dissolved salts and sugars, leading to a lower oxygen transfer rate
C:
The KLa of the medium increases with the concentration of dissolved salts and sugars, leading to a lower oxygen transfer rate
D:
None of the above
Answer: A
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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)
A:
H = Vs/(Vs-Vt)
B:
H = Vs/(Vs+ Vt)
C:
H = Vs/(Vs.Vt)
D:
H = (Vs+Vt)/Vs
Answer: B
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An increase in the heat transfer in the stirred tank reactor will be observed at
A:
higher cooling water temperature
B:
higher stirrer speed
C:
the removal of baffles from the reactor
D:
slower stirrer speed
Answer: B
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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
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
Answer: A
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Oxygen transfer rate is increased with an increase in the stirrer speed in aerated bioreactor because
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
Answer: D
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