Question is ⇒ If liquid density and viscosity remains constant, then the Reynolds number in a stirred tank reactor will vary with the, Options are ⇒ (A) impeller diameter, (B) square root of the impeller diameter, (C) square of the impeller diameter, (D) cube of the impeller diameter, (E) , Leave your comments or Download question paper.

Question is ⇒ If liquid density and viscosity remains constant, then the Reynolds number in a stirred tank reactor will vary with the, Options are ⇒ (A) impeller diameter, (B) square root of the impeller diameter, (C) square of the impeller diameter, (D) cube of the impeller diameter, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	If liquid density and viscosity remains constant, then the Reynolds number in a stirred tank reactor will vary with the
A.	impeller diameter [Wrong Answer]
B.	square root of the impeller diameter [Wrong Answer]
C.	square of the impeller diameter [Correct Answer]
D.	cube of the impeller diameter [Wrong Answer]
View Answer 1 -1 Explanation:- Answer : C Discuss it below : !! OOPS Login [Click here] is required to post your answer/result Help other students, write article, leave your comments

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⇒ For aerated mixing vessels in an aqueous solution, the mass transfer coefficient (k_L) co-relating power consumption (P_m) and fermenter volume (V) can be expressed as
k_L ∝ (P_m/V)^0.33
k_L ∝ (P_m/V)^0.66
k_L ∝ (P_m/V)^0.50
k_L ∝ (P_m/V)

⇒ Radial flow impellers
provide high shear conditions for breaking up bubbles
direct flow towards the walls of the reactor
Both (a) and (b)
provide low shear conditions and are suited for use in shear sensitive procesess

⇒ What is the ratio of depth of liquid in vessel to the diameter of tank (H:D_t)?
0.0423611111111111
0.0840277777777778
0.167361111111111
none of these

⇒ Power consumption by agitation is
a function of physical properties
a function of operating conditions
a function of vessel and impeller geometry
all of the above

⇒ 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
gas-liquid interface
bubble boundary layer
bulk liquid
gas phase

⇒ An increase in the heat transfer in the stirred tank reactor will be observed at
higher cooling water temperature
higher stirrer speed
the removal of baffles from the reactor
slower stirrer speed

⇒ Which of the following number is calculated from the diameter and peripheral speed of the impeller?
Reynolds number
Froude number
Power number
None of these

⇒ Bioreactors, where vortex is formed, another dimensionless number, __________ is useful.
Stanton
Rayleigh
Bond
Froude

⇒ The range of width for the baffle in the fermenter is __________ times of vessel diameter
1/10 to 1/12
1/8 to 1/10
1/5 to 1/8
none of these

⇒ Power number is expressed as
P₀ / N²D_i³ρ
P₀ / N³D_i⁵ρ
P₀ / N³D_i³ρ
P₀ / N²D_i²ρ

⇒ Swirling and vortex formation can be prevented by
using baffles
using diffusion ring with turbines
both (a) and (b)
none of these

⇒ The effect of increasing the stirrer speed in an unbaffled stirred tank reactor is that
a small increase in stirrer speed will cause the liquid to enter the turbulent flow regime
as the stirrer speed increases, the liquid will continue to circulate and then become turbulent
as the stirrer speed increases, the liquid will continue to circulate. Eventually a vortex will form.
A vortex will form at low stirrer speeds. As the stirrer speed increases the liquid will start to circulate

⇒ A fermentation system has a K_La of 3 s^-1 and a C₀^* of 5 ppm of O₂. If the bulk liquid is saturated with oxygen then the oxygen transfer rate will be equal to
zero
3 mg.l^-1.s^-1
5 mg.l^-1.s^-1
15 mg.l^-1.s^-1

⇒ A higher liquid height will lead to a higher gas hold up by which the oxygen transfer rate will be
higher throughout the reactor
lower throughout the reactor
higher at the base of the reactor
lower at the base of the reactor

⇒ The oxygen transfer rate in a bioreactor will increase if
oil is added
antifoam is added
detergent like molecules are added
increase in the reactor temperature

⇒ The volume of liquid (V_L) in a cylindrical reactor can be calculated from the liquid height (H_L) and tank diameter (D_t) using the following equation
V_L = 4/3 x π x H_L x D_t³/8
V_L= H_L x π x D_t²/4
V_L= H_L x π x D_t²
V_L = 4 x π x D_t²

⇒ Froude number is avoided in calculation of power requirements for low viscosity liquid mixing systems when
baffled systems are used
Reynolds number is less than 300
both (a)and(b)
none of these

⇒ If the stirring speed increased from 300 to 500 rpm leads to an increase in the reaction rate by two folds. Then it may be concluded that
the reaction was mass transfer limited at 300 rpm
the reaction was mass transfer limited at 500 rpm
the reaction did not involve any mass transfer step
the movement of molecules in the reactor at 300 rpm occurred due to diffusion alone

⇒ Impeller damage can be minimized by
using specially designed axial flow impellers
using radial flow impellers
using Intermig impellers
all of the above

⇒ Which of the following impellers will provide radial flow?
Paddles
Flat blade turbines
Disk flat blade turbines
All of the above

⇒ Detergent like substances produced by microorganisms during a fermentation will lead to
decrease the surface tension of the liquid
accumulate at the gas liquid interface
decrease the rate of bubble coalescence
all of the above

⇒ Oxygen transfer rate is increased with an increase in the stirrer speed in aerated bioreactor because
it decrease the bubble size
it decreases the size of the boundary layer surrounding a bubble
it increases the rate of movement of oxygen molecules through the bulk liquid
all of the above

⇒ Power number (N_p) is also known as
Froude's number
Bond's number
Newton's number
Rayleigh's number

⇒ The dynamic technique is based on the
oxygen material balance in an aerated batch fermenter during the growth of microorganisms
change of the oxygen concentration
oxidation of the sodium sulfite to sodium sulfate
oxygen material balance in a fermenter

⇒ Which of the following is not classified as an axial flow impeller?
A propeller
A marine impeller
A Rushton turbine
A hydrofoil impeller

⇒ Which of the following impeller is used in situation where strong vertical currents are desirable for suspending heavily particles?
Propeller
Paddle
Turbine
None of these

⇒ Which of the following will have the highest surface area available for oxygen transfer?
A shake flask
A standing test tube
A non-sparged stirred tank reactor agitated at 400 rpm
A sparged stirred tank reactor agitated at 400 rpm

⇒ Pure oxygen, if used instead of air will increase oxygen transfer rates because
the saturation concentration of oxygen is higher
the bubble size is smaller
the oxygen transfer coefficient is larger
the partial pressure of oxygen in the gas phase is lower

⇒ 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
10,000 l
20,000 l
30,000 l
40,000 l

⇒ Which have the maximum resistance while transferring carbon dioxide from the bulk liquid to an air bubble?
Moving through the gas liquid interface
Moving through the bubble boundary layer
Moving across the cell membrane
Moving through the bulk liquid