# Separation Processes Questions and Answers – Mass Transfer in Turbulent Flow

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This set of Separation Processes Multiple Choice Questions & Answers (MCQs) focuses on “Mass Transfer in Turbulent Flow”.

1. 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

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

2. Which of the following reynold’s number represents a turbulent flow?
a) 500
b) 700
c) 2500
d) 6000

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

3. 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

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

4. 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

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

5. 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

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

6. 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

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

7. What is the Sherwood number analogous to?
a) Schmidt number
b) Lewis number
c) Nusselt number
d) Prandtl number

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

8. 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

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

9. 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

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

10. 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 