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Biochemical Engineering Objective Questions { Agitation and Aeration }

36. Which of the following will have the highest surface area available for oxygen transfer?
A.A shake flask
B.A standing test tube
C.A non-sparged stirred tank reactor agitated at 400 rpm
D.A sparged stirred tank reactor agitated at 400 rpm
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37. 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
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38. Power consumption by agitation is
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
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39. Which of the following impellers will provide radial flow?
B.Flat blade turbines
C.Disk flat blade turbines
D.All of the above
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40. When liquid is pumped through cooling coil in a stirred tank reactor to cool. Which of the following is not correct?
A.If the stirrer speed is increased, the rate will be faster
B.Baffles in the tank will increase the rate of cooling
C.Faster cooling rates at a slower rate of pumping
D.Faster cooling rates at a faster rate of pumping
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41. When the height of an aerated bioreactor is increased, it will increase the oxygen transfer rate by
A.increasing the partial pressure of oxygen at the base of the reactor
B.decreasing the saturation concentration of oxygen in the reactor
C.decreasing the gas-holdup
D.all of the above
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42. Which of the following is correct for the off-centre impellers?
A.Off-centre impellers can be used with any size reactor
B.Off-centre impellers should only be used with reactors with volumes less than 10 m3
C.The impeller should never be placed in an off-centre position
D.Off-centre impellers can be used when volume is greater than 10 m3
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