Engineering Questions with Answers - Multiple Choice Questions
Separation Processes MCQ’s – Mass Transfer in Laminar Flow
1 - Question
The equation of motion for the liquid film in fully developed laminar flow in y-direction is:
a) µd2uy/dx2 + ρg =0
b) µd2uy/dy2 + ρg =0
c) µd2uy/dz2 + ρg =0
d) µd2uy/dx2 = 0
View Answer
Explanation: Flow is in y direction but changes with respect to z-direction. Hence the equation of motion is µd2uy/dz2 + ρg =0.
2 - Question
Which two forces is the reynold’s number a ratio of?
a) Gravitational force and interfacial force
b) Interfacial force and viscous force
c) Thermal conductivity and electrical conductivity
d) Conduction and convection
View Answer
Explanation: The reynold’s number Nre = 4τ/µ is the ratio of interfacial and viscous force.
3 - Question
What value of Reynold’s number is obtained with water?
a) 8
b) 16
c) 25
d) 50
View Answer
Explanation: The value of 25 is obtained with water.
4 - Question
What value of reynold’s number represents a laminar flow?
a) 3
b) 2500
c) 5000
d) 78
View Answer
Explanation: Only the value of 78 lies between 8 and 1200. SO it represents a laminar flow.
5 - Question
Which of the following is correct about Reynold’s number?
a) 3less thanNreless than1200
b) 3less thanreless than1600
c) 25less thanreless than1200
d) 8less thanreless than1200
View Answer
Explanation: 8less thanreless than1200 are the correct boundary conditions for Reynold’s number.
6 - Question
Prandtl’s number is the ratio of which two quantities?
a) Momentum conductivity and thermal conductivity
b) Coefficient of convection to thermal conductivity
c) Momentum diffusivity and thermal diffusivity
d) Interfacial force and viscous force
View Answer
Explanation: Prandtl’s number is the ratio of Momentum diffusivity and thermal diffusivity.
7 - Question
Which of the following is true about prandtl’s number?
a) Npr = Cpµ/k
b) Npr = Cpk/µ
c) Npr = Cvµ/k
d) Npr = Cpµ
View Answer
Explanation: Prandtl’s number is the ratio of Momentum diffusivity and thermal diffusivity. Hence the formula is Npr = Cpµ/k.
8 - Question
What is the physical significance of nusselt’s number?
a) Ratio of convective heat transfer to conductive heat transfer
b) Ratio of convective heat transfer to conductive heat transfer
c) Ratio of total heat transfer to conductive heat transfer
d) Ratio of total transfer to convective heat transfer
View Answer
Explanation: Nusselt number is the Ratio of convective heat transfer to conductive heat transfer.
9 - Question
What is the correct formula for nusselt’s number?
a) hµ/k
b) hρ/k
c) hL/k
d) hΔTL/k
View Answer
Explanation: The nusselt number hL/k is the ratio of total heat transfer to onductive heat transfer.
10 - Question
Which of the following is most true?
a) Na = kcA(cai – ca)
b) Na = kcAΔc
c) Na = kcA(cai – ca)mean
d) Na = kcA(cai – ca)log mean
View Answer
Explanation: Δc is taken as the driving force and is true every time. It’s expression will change depending upon the conditions