20551. Why vortexing is undesirable in the agitation of biological systems?
20552. The rate limiting step in the movement of oxygen from the gas phase in a bubble to the cell is the movement of oxygen molecules through
20553. Penetration theory assumes that turbulent eddies travel from the bulk of the phase to the interface where they remain constant for a constant exposure time (te). The model correlating KL, mass transfer coefficient and DAB, diffusivity can be expressed as
20554. The oxygen uptake requirements of a microbial population is characterized by the following parameters: μm = 0.2 h-1, K0 = 0.2 mg O2.l-1, Y0 = 0.5 mg dry weight/mg O2 and C0,crit=0.8 mg.l-1 The required concentration of cells is 1000 mg.l-1 and the saturation oxygen concentration of the medium is 5.8 mg.l-1. The required KLa must be greater than
20555. Which have the maximum resistance while transferring carbon dioxide from the bulk liquid to an air bubble?
20556. If liquid density and viscosity remains constant, then the Reynolds number in a stirred tank reactor will vary with the
20557. What is the ratio of depth of liquid in vessel to the diameter of tank (H:Dt)?
20558. Radial flow impellers
20559. Transient flow range of mixing speed is obtained for
20560. A typical ceiling fan would be best described as a(n)
20561. What is the ratio of diameter of impeller to the diameter of tank (Da:Dt)?
20562. The reason of using a flat disk in a Turbine is
20563. Which of the following is not considered among the three best-known theories of interphase mass transfer?
20564. Which of the following is most likely to cause an increase in the rate of oxygen transfer into a particular aerated fermentation system?
20565. At 25°C, the saturation concentration of oxygen in water is 1.26 mmol/l and the partial pressure of oxygen is 1 atm. The Henry's law constant will be
20566. Gas hold up, characterizing the hydrodynamics in a fermenter, mainly depends on the
20567. Turbine impeller consists of flat impeller blades with
20568. An aerated bioreactor will increase oxygen transfer rates with the addition of detergents because it
20569. Vortexing in stirred tank reactors can be prevented by
20570. Which of the following would be best described as an axial flow impeller?
20571. Henry's law relates
20572. Power number is ratio of
20573. The volume of liquid (VL) in a cylindrical reactor can be calculated from the liquid height (HL) and tank diameter (Dt) using the following equation
20574. The average fractional gas hold up (H) can be given as (where Zf and Zl are the level of aerated and clear liquid respectively)
20575. Which of the following(s) is/are non-mechanically agitated reactors?
20576. Which of the following best explains the reasons for using axial flow impellers in crystallization and precipitation reactions?
20577. Which of the following will have the highest surface area available for oxygen transfer?
20578. A flooded impeller will lead to poor oxygen transfer rates because
20579. Power consumption by agitation is
20580. Which of the following impellers will provide radial flow?
20581. When liquid is pumped through cooling coil in a stirred tank reactor to cool. Which of the following is not correct?
20582. When the height of an aerated bioreactor is increased, it will increase the oxygen transfer rate by
20583. Which of the following is correct for the off-centre impellers?
20584. The power required by an impeller in a gas sparged system compare to the power required by impeller operating at same speed in a gas free liquid is usually
20585. Which of the following stirrer requires least amount of energy for same yield?
20586. A reactor has a total volume of 50,000 litres. If it has a headspace volume of 10,000 litres, then volume of liquid in the reactor will be
20587. Pure oxygen, if used instead of air will increase oxygen transfer rates because
20588. For aerated mixing vessels in an aqueous solution, the mass transfer coefficient (kL) co-relating power consumption (Pm) and fermenter volume (V) can be expressed as
20589. Higher temperatures affect oxygen transfer rates by
20590. The Intermig impeller is
20591. Main reason for using baffles in stirred tank reactors are
20592. Which of the following is not classified as an axial flow impeller?
20593. Flooding is a condition/phenomenon which occur in a bioreactor when
20594. A cylindrical reactor has a liquid volume of 100,000 litres. It has an aspect ratio the ratio of the channel height to width of 1:1. The height of the liquid in the reactor will be approximately:
20595. Detergent like substances produced by microorganisms during a fermentation will lead to
20596. A cylindrical reactor fitted with Rushton Turbine has a liquid volume of 100,000 litres. It has an aspect ratio (the ratio of the channel height to the width) of 2:1. The diameter of the impeller should be approximately:
20597. In the bubble boundary layer, oxygen concentration can be determined by measuring
20598. Impeller damage can be minimized by
20599. To increase the oxygen transfer rate in a shake flask culture system, which of the following (s) is/are followed?
20600. What is/are the major difference(s) between disc and turbine type stirrer?
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