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# Separation Processes MCQ’s – Mass Transfer in Turbulent Flow

1 - Question

Which of the following is true about turbulent flow?

a) Nre greater than 2000

b) Nre greater than 4000

c) Nre greater than 5000

d) Nre greater than 6000

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Answer: aExplanation: The flow becomes turbulent for a reynold’s number above 4000.

2 - Question

Which of the following reynold’s number represents a turbulent flow?

a) 500

b) 700

c) 2500

d) 6000

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Answer: dExplanation: The flow becomes turbulent for a reynold’s number above 4000.

3 - Question

Which of the following is present in turbulent flow mass transfer?

a) Slow mass transfer

b) Less mass transfer

c) Eddy currents

d) Eddy diffusion

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Answer: dExplanation: Eddy diffusion is created due to the turbulent flow because of which mass transfer is fast.

4 - Question

What is the physical significance of drag coefficient?

a) It is drag force divided by projected area and velocity head

b) It is the ratio of pipe wall shear stress and velocity head

c) It is the ratio of inertial forces to viscous force

d) It is the ratio of inertial force to surface tension force

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Answer: aExplanation: The drag coefficient Cd=2FD/Au2ρ is drag force divided by projected area and velocity head.

5 - Question

What is the physical significance of weber number?

a) It is drag force divided by projected area and velocity head

b) It is the ratio of pipe wall shear stress and velocity head

c) It is the ratio of inertial forces to viscous force

d) It is the ratio of inertial force to surface tension force

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Answer: dExplanation: The weber number is the ratio of inertial force to surface tension force.

6 - Question

What is the physical significance of lewis number?

a) It is the ratio of bulk transfer mass and molecular diffusion

b) It is the ratio of thermal diffusivity to mass diffusivity

c) It is the ratio of conductive mass transfer to molecular diffusion

d) It is the ratio of mass transfer to mass capacity

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Answer: bExplanation: Lewis number is the ratio of thermal diffusivity to mass diffusivity.

7 - Question

What is the Sherwood number analogous to?

a) Schmidt number

b) Lewis number

c) Nusselt number

d) Prandtl number

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Answer: cExplanation: The Sherwood number Nsh =KcL/Dab is analogous to nusselt number.

8 - Question

Which of the following equations is referred as reynold’s analogy?

a) f/c = kc/ux

b) f/c = kcux

c) f/2 = kcux

d) f/2 = kc/ux

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Answer: dExplanation: The equation f/2 = kc/ux is referred to as reynold’s analogy.

9 - Question

For what condition does the equation for reynold’s analogy equals to equation by Chilton-colburn analogy.

a) Npr=Nre=1

b) Npr=Nse=1

c) Npr=Nsc=1

d) Nsc=Nse=1

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Answer: cExplanation: For Npr=Nsc=1 the equation for reynold’s analogy equals to equation by Chilton-colburn analogy.

10 - Question

What is the significance of fanning friction factor?

a) It is the ratio of pipe wall shear stress to velocity head

b) It is drag force divided by projected area and velocity head

c) It is the ratio of inertial forces to viscous force

d) It is the ratio of inertial force to surface tension force

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Answer: aExplanation: The fanning friction factor is the ratio of pipe wall shear stress to velocity head.