Engineering Questions with Answers - Multiple Choice Questions

# Mechanical Operations MCQ’s – Critical Speed

1 - Question

If a small diameter column is used with deep bed through solids, this is called _____
a) Sledging
b) Slugging
c) Skipping
d) Centering

Explanation: Travel of successive bubbles up through the column separated by slug cause the phenomenon of slugging

2 - Question

What does the below equation represent?
ub = 0.7√(gDb )
a) Bed velocity
b) Bubble velocity
c) Bank velocity
d) Bishop velocity

Explanation: The following empirical relation for follows for bubble velocity in the fluidized bed, this equation holds well if Db taken as equivalent diameter

3 - Question

At what temperature fluidized bed operates?
a) 1075 to 1225 K
b) 555 to 4555 K
c) 100 to 500 K
d) 500 to 1500 K

Explanation: Fluidized bed furnace operates at a temperature of range of 1075 to 1225 K but most close to 1175 K to be precise.

4 - Question

What are the velocities of pneumatic conveying?
a) 45 to 60 m/s
b) 50 to 45 m/s
c) 15 to 30 m/s
d) 1 to 10 m/s

Explanation: The suspending fluid in a pneumatic conveyer is a gas, usually air flowing at velocities between 15 and 30 m/s in pipes from 50 to 400 mm in diameter.

5 - Question

What does the below equation represent? a) Final velocity
b) Approach velocity
c) Carry velocity
d) Critical velocity

Explanation: When the mass ratio of solid to gas (r) is usually less than 5, for such suspensions the critical velocity may be estimated from the empirical relation.

6 - Question

What does the below equation represent? b) Drag force
c) Final force
d) Diagonal force

Explanation: The drag force upon a particle is given by the above relation, where C is the drag coefficient which is dimensionless.

7 - Question

What is the unit of dimensional constant?
a) lb. ft. / lb. force sec
b) lb. ft. / lb. force sec2
c) lb. ft. / lb. force sec-1
d) lb. ft2. / lb. force sec

Explanation: The value of dimensional constant is 32.17 and its units as in FPS system is given by lb. ft. / lb. force sec2.

8 - Question

What does the below equation represent? a) Settling Velocity
b) Terminal settling velocity
c) Final settling velocity
d) Medium velocity

Explanation: The above relation represents the terminal settling velocity, where g is acceleration due to gravity and mp is the mass of particle.

9 - Question

Mixing of liquids and suspension of solids may be accomplished by ______
a) Dryer
b) Sparger
c) Clamper
d) Bolder

Explanation: Mixing of liquids and suspension of solids may be accomplished by bubbling with an inert gas introduced uniformly at the bottom of the tank.

10 - Question

When _______ occurs below a critical power input the gas bubbles are not affected laterally but move upward.
a) Weeping
b) Flooding
c) Mixing
d) Entrainment