Fluid Flow – Section 1

31. A Newtonian 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: A. is constant regardless of the stirrer speed or mixing time

32. Which pattern of mixing is preferred in stirred tank reactors during the culture of aerobic microorganisms?

A. Laminar flow
B. Transient flow
C. turbulent flow
D. all of these

Correct Answer: C. turbulent flow

33. Animal cell cultures do not have much effect on shear forces because

A. the cell size is generally smaller than the critical eddy size at which shear will have an effect
B. cells are larger than the critical eddy size at which shear will have an effect
C. animal cells have cell walls
D. animal cells have cell membranes

Correct Answer: A. the cell size is generally smaller than the critical eddy size at which shear will have an effect

34. The viscosity of the culture fluid is classified as both pseudoplastic and thixotropic which indicates that the viscosity

A. increases with stirring speed but decreases with mixing time
B. increases with stirring speed and increases with mixing time
C. decreases with stirring speed but increases with mixing time
D. decreases with stirring speed and decreases with mixing time

Correct Answer: D. decreases with stirring speed and decreases with mixing time

35. Pluronic F68 is added to cell culture media as

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

Correct Answer: B. a shear protectorant

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