26. Turbine impeller consists of flat impeller blades with

A. a vertical pitch welded directly to the shaft
B. a angled pitch welded directly to the shaft
C. a vertical pitch welded to a horizontal disk
D. a angled pitch welded to a horizontal disk

27. An aerated bioreactor will increase oxygen transfer rates with the addition of detergents because it

A. enhances bubble coalescence
B. causes bubbles to expand
C. discourages bubble coalescence
D. increases the surface tension of the liquid

28. Vortexing in stirred tank reactors can be prevented by

A. installing baffles in the reactor
B. shifting the impeller to an off-center position
C. Both (a) and (b)
D. using axial flow impellers

29. Which of the following would be best described as an axial flow impeller?

A. An impeller with blades pitched at 45° to the vertical
B. An impeller which directs liquid flow towards the base of the reactor
C. Both (a) and (b)
D. An impeller with blades pitched at 75° to the vertical

30. Henry’s law relates

A. the partial pressure of oxygen and the saturation concentration of oxygen in the liquid
B. the oxygen transfer rate and the bubble size
C. the oxygen transfer rate and the temperature
D. the oxygen transfer rate to the partial pressure of oxygen in the liquid