Fluid Flow – Section 1

11. Mixing in stirred tank reactors can

A. be described as either laminar, transient or turbulent
B. achieve turbulent conditions by increasing the stirrer speed
C. induce laminar flow conditions by the addition of baffles
D. all of the above

Correct Answer: A. be described as either laminar, transient or turbulent

12. In animal cell bioreactor, bubble damage can be minimized by

A. the addition of a shear protectorant
B. using a bubble-free oxygen delivery system
C. headspace aeration
D. all of the above

Correct Answer: D. all of the above

13. The viscosity of a fluid changes with either stirrer speed or mixing time. But when mixing ceases, the viscosity returns to its original state. This fluid is best described as

A. newtonian
B. rheopectic
C. viscoelastic
D. thixotropic

Correct Answer: C. viscoelastic

14. In sparged mammalian cell bioreactors, the cell damage is caused because of

A. shear stress arising during mixing of the cell culture fluid
B. shear stresses arising from the breakup of bubbles at the liquid surface
C. shear stresses between bubbles in foam at the liquid surface
D. all of the above

Correct Answer: A. shear stress arising during mixing of the cell culture fluid

15. The SI unit for viscosity is

A. kg.m-1.s-1
B. kg.m-2.s-2
C. kg.m-3.s-1
D. kg.m-1.s-2

Correct Answer: A. kg.m-1.s-1

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