Agitation And Aeration

Question: Which of the following is not considered among the three best-known theories of interphase mass transfer?
[A].

two-film theory

[B].

penetration theory

[C].

surface renewal theory

[D].

Calderbank and Moo-Young theory

Answer: Option D

Explanation:

No answer description available for this question.

Question: Main reason for using baffles in stirred tank reactors are
[A].

baffles permit turbulence conditions to arise at low stirrer speed

[B].

baffles will allow axial mixing to occur even with radial flow impellers

[C].

both (a) and (b)

[D].

baffles prevent turbulent conditions in stirred tank reactors

Answer: Option C

Explanation:

No answer description available for this question.

Question: The effect of increasing the stirrer speed in an unbaffled stirred tank reactor is that
[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

Answer: Option C

Explanation:

No answer description available for this question.

Question: If the stirrer speed is too slow, bubbles will accumulate and coalescese under the impeller. This phenomenon is known as a
[A].

coalesced impeller

[B].

flooded impeller

[C].

river impeller

[D].

dry impeller

Answer: Option B

Explanation:

No answer description available for this question.

Question: 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: Option A

Explanation:

No answer description available for this question.

Question: Detergent like substances produced by microorganisms during a fermentation will lead to
[A].

decrease the surface tension of the liquid

[B].

accumulate at the gas liquid interface

[C].

decrease the rate of bubble coalescence

[D].

all of the above

Answer: Option D

Explanation:

No answer description available for this question.

Question: During aeration, a cylindrical reactor had a height of 10 m. Without aeration, the height was 7.5 m. Under these aeration and mixing conditions, the gas hold up in the reactor is
[A].

100%

[B].

75%

[C].

50%

[D].

25%

Answer: Option D

Explanation:

No answer description available for this question.

Question: A higher liquid height will lead to a higher gas hold up by which the oxygen transfer rate will be
[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

Answer: Option C

Explanation:

No answer description available for this question.

Question: In the bubble boundary layer, oxygen concentration can be determined by measuring
[A].

the steady state oxygen concentration in a mixed aerated reactor before inoculation

[B].

the steady state oxygen concentration in a mixed aerated reactor after inoculation

[C].

the steady state oxygen concentration in the boundary layer using a micro-probe

[D].

volume of oxygen supplied

Answer: Option A

Explanation:

No answer description available for this question.

Question: 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].

0.793atml/mmol

[B].

0.207atml/mmol

[C].

1.26 atml/mmol

[D].

8.74 atml/mmol

Answer: Option A

Explanation:

No answer description available for this question.