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Agitation And Aeration Online Exam Quiz

Important questions about Agitation And Aeration. Agitation And Aeration MCQ questions with answers. Agitation And Aeration exam questions and answers for students and interviews.

1. 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

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. Which of the following impellers generate a flow parallel to the axis of shaft?

Options

A : Axial flow

B : Radial flow

C : Both (a)and(b)

D : None of these

10. What is the effect of the concentration of dissolved salts and sugars on the oxygen transfer rate?

Options

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 K L a of the medium decreases with the concentration of dissolved salts and sugars, leading to a lower oxygen transfer rate

C : The K L a of the medium increases with the concentration of dissolved salts and sugars, leading to a lower oxygen transfer rate

D : None of the above

1. Which of the following impellers will provide radial flow?

Options

A : Paddles

B : Flat blade turbines

C : Disk flat blade turbines

D : All of the above

2. The average concentration of oxygen in the boundary layers surrounding the bubbles ( C o * ) in a reactor is normally determined by

Options

A : ultra-small dissolved oxygen probes

B : laser based photographic systems

C : measuring the steady state concentration of oxygen in the bulk liquid prior to inoculation of the reactor

D : measuring the steady state concentration of oxygen in the bulk liquid after inoculation of the reactor

3. Which of the following best explains the reasons for using axial flow impellers in crystallization and precipitation reactions?

Options

A : Crystal and precipitates are not too small, so as to ensure easy separation of the solids from the mother liquor

B : Crystals and precipitates are thoroughly broken down, so as to ensure easy separation of the solids from the mother liquor

C : Both (a) and (b)

D : Axial flow impellers provide low shear, energy efficient mixing conditions

4. What is the ratio of depth of liquid in vessel to the diameter of tank ( H:D t )?

Options

A : 1 : 1

B : 2 : 1

C : 4 : 1

D : none of these

5. Power number is ratio of

Options

A : imposed forced to intertial force

B : bouyant force to inertial force

C : gravitation force to inertial force

D : imposed force to gravitational force

6. Power consumption by agitation is

Options

A : a function of physical properties

B : a function of operating conditions

C : a function of vessel and impeller geometry

D : all of the above

7. The reason of using a flat disk in a Turbine is

Options

A : to create high shear conditions

B : to break up bubbles more efficiently than the impeller blades

C : to ensure that the bulk of the energy consumption occurs at the blades

D : all of the above

8. Why vortexing is undesirable in the agitation of biological systems?

Options

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

9. The range of width for the baffle in the fermenter is __________ times of vessel diameter

Options

A : 1/10 to 1/12

B : 1/8 to 1/10

C : 1/5 to 1/8

D : none of these

10. Which of the following(s) is/are non-mechanically agitated reactors?

Options

A : Stirrer tank reactor

B : Bubble column

C : Air lift reactor

D : Both (b) and (c)

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