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Home Biochemical Engineering Fluid Flow Comments

  • Question
  • A viscoelastic fluid is one in which the viscosity


  • Options
  • 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
  • changes during mixing but returns to its original state after mixing 


  • Fluid Flow problems


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    • 1. If the viscosity of a fluid decreases with the length of time that it is being mixed, then this fluid is

    • Options
    • A. newtonian
    • B. rheopectic
    • C. viscoelastic
    • D. thixotropic
    • Discuss
    • 2. Bubble free aeration systems requires

    • Options
    • 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
    • Discuss
    • 3. A liquid is flowing at 11,400 l.h-1 along a pipeline having a diameter of 4 cm. If the liquid has a density of 1 g.ml-1 and viscosity of 0.001kg.m-1.s-1, then the liquid would be in the

    • Options
    • A. laminar phase
    • B. transient phase
    • C. turbulent phase
    • D. any of the phase
    • Discuss
    • 4. 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

    • Options
    • A. newtonian
    • B. rheopectic
    • C. viscoelastic
    • D. thixotropic
    • Discuss
    • 5. The medium will have the highest viscosity (considering that the cells do not secrete gums) with the presence of

    • Options
    • A. single celled bacteria
    • B. filamentous fungi that form pellets
    • C. filamentous fungi that grow as long poorly branched chains
    • D. yeast
    • Discuss
    • 6. Which of the following is correct?

    • Options
    • A. The viscosity of liquids and gases decrease with increasing temperature
    • B. The viscosity of liquids and gases increase with increasing temperature
    • C. the viscosity of gases increases with increasing temperature, but decreases in liquids
    • D. the viscosity of gases decreases with increasing temperature, but decreases in liquids.
    • Discuss
    • 7. Pluronic F68 protects mammalian cells from damage stems as it is a/an

    • Options
    • A. surface active agent which stabilizes foams
    • B. surface active agent which destabilizes foams
    • C. excellent source of vitamins
    • D. coagulant
    • Discuss
    • 8. Mixing in stirred tank reactors can

    • Options
    • 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
    • Discuss
    • 9. If the viscosity of a fluid decreases with increasing stirrer speed, then the nature of the fluid is

    • Options
    • A. newtonian
    • B. pseudoplastic
    • C. dilatant
    • D. thixotropic
    • Discuss
    • 10. Pluronic F68 is added to cell culture media as

    • Options
    • A. a nutrient
    • B. a shear protectorant
    • C. to increase oxygen transfer rates
    • D. all of these
    • Discuss


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