Biochemical Engineering

Question: In aerobic microorganisms cultures radial flow impellers are used because
[A].

they provide energy efficient high turbulent mixing conditions

[B].

they provide low shear mixing conditions

[C].

they provide high shear mixing conditions

[D].

they ensure that bubble size is maximized leading to high oxygen transfer rates

Answer: Option C

Explanation:

No answer description available for this question.

Question: The advantage of axial flow impellers over radial flow impellers is that axial flow impellers
[A].

provide better lift of solids

[B].

provide high shear conditions

[C].

provide low shear conditions

[D].

are cheaper to build

Answer: Option A

Explanation:

No answer description available for this question.

Question: Radial flow impellers
[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

Answer: Option C

Explanation:

No answer description available for this question.

Question: Axial flow impellers
[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

Answer: Option B

Explanation:

No answer description available for this question.

Question: Which of the following would be best described as an axial flow impeller?
[A].

An impeller with blades pitched at 45° to the vertical

[B].

An impeller which directs liquid flow towards the base of the reactor

[C].

Both (a) and (b)

[D].

An impeller with blades pitched at 75° to the vertical

Answer: Option C

Explanation:

No answer description available for this question.

Question: Which of the following would be best described as a radial flow impeller?
[A].

An impeller with blades pitched at 45° to the vertical

[B].

A Rushton turbine

[C].

Both (a) and (b)

[D].

An impeller which directs liquid flow towards the base of the reactor

Answer: Option B

Explanation:

No answer description available for this question.

Question: A flooded impeller will lead to poor oxygen transfer rates because
[A].

bubbles tend to coalesce under the impeller

[B].

bubbles tend to break down too rapidly under high shear conditions

[C].

bubbles tend to move too quickly through the bulk liquid

[D].

the cells clog up the surface of the bubble

Answer: Option A

Explanation:

No answer description available for this question.

Question: Why vortexing is undesirable in the agitation of biological systems?
[A].

The collision between the cells, impeller and air bubbles will lead to cell damage

[B].

Poor mixing despite the use of high stirrer speeds

[C].

Mixing will not be in the turbulent region

[D].

All of the above

Answer: Option D

Explanation:

No answer description available for this question.

Question: Vortexing in stirred tank reactors can be prevented by
[A].

installing baffles in the reactor

[B].

shifting the impeller to an off-centre position

[C].

Both (a) and (b)

[D].

using axial flow impellers

Answer: Option C

Explanation:

No answer description available for this question.

Question: Bioreactors, where vortex is formed, another dimensionless number, __________ is useful.
[A].

Stanton

[B].

Rayleigh

[C].

Bond

[D].

Froude

Answer: Option D

Explanation:

No answer description available for this question.