200 Best MCQs on Agitation and aeration- biochemical engineering
Q73). Bioreactors, where vortex is formed, another dimensionless number, __________ is useful.
a).Stanton
b).Rayleigh
c).Bond
d).Froude
Correct Answer:
Froude
Explaination:
Q74). 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
Correct Answer:
all of the above
Explaination:
Q75). 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
Correct Answer:
the reaction was mass transfer limited at 300 rpm
Explaination:
Q76). 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
Correct Answer:
higher stirrer speed
Explaination:
Q77). 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 Kl of the medium decreases with the concentration of dissolved salts and sugars, leading to a lower oxygen transfer rate
c).The Kl of the medium increases with the concentration of dissolved salts and sugars, leading to a lower oxygen transfer rate
d).None of the above
Correct Answer:
The saturation concentration of oxygen in the medium decreases with the concentration of dissolved salts and sugars, leading to a lower oxygen transfer rate
Explaination:
Q78). Which of the following impellers generate a flow parallel to the axis of shaft?
a).Axial flow
b).Radial flow
c).Both (a)and(b)
d).None of these
Correct Answer:
Axial flow
Explaination:
Q79). In a tall reactor, oxygen transfer rates will be
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
Correct Answer:
highest at the base of the reactor
Explaination:
Q80). Which of the following impeller is used in situation where strong vertical currents are desirable for suspending heavily particles?
a).Propeller
b).Paddle
c).Turbine
d).None of these
Correct Answer:
Propeller
Explaination: