Fluid Flow – Section 1

6. Bubble free aeration systems require

A. silicone tubing or gas permeable membranes to facilitate gas transfer
B. carbon dioxide instead of air to supply oxygen
C. silicone tubing or gas permeable membranes to remove carbon dioxide by oxygen in the form of hydrogen peroxide
D. filled headspace of the reactor with carbon dioxide

Correct Answer: A. silicone tubing or gas permeable membranes to facilitate gas transfer

7. Non-linear relationship between shear stress and shear rate exists in

A. newtonian fluids
B. non-newtonian fluids
C. both (a) and (b)
D. none of these

Correct Answer: B. non-newtonian fluids

8. If the viscosity of a fluid decreases with increasing stirrer speed, then the nature of the fluid is

A. newtonian
B. pseudoplastic
C. dilatant
D. thixotropic

Correct Answer: B. pseudoplastic

9. A pseudoplastic fluid is one in which the viscosity

A. is constant regardless of the stirrer speed or mixing time
B. changes during mixing but returns to its original state after mixing
C. increases with increasing stirrer speed
D. decreases with increasing stirrer speed

Correct Answer: D. decreases with increasing stirrer speed

10. A viscoelastic fluid is one in which the viscosity

A. is constant regardless of the stirrer speed or mixing time
B. changes during mixing but returns to its original state after mixing
C. increases with increasing stirrer speed
D. decreases with increasing stirrer speed

Correct Answer: B. changes during mixing but returns to its original state after mixing

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