Mechanical Operations Multiple Choice Questions on “Materials Of Construction”.
1. _____are commonly used to control product on a horizontal or inclined conveyor.
a) Magnet
b) Cleated
c) Clamped
d) Stock
Answer: b
Clarification: Cleated belt conveyors are commonly used to control product on a horizontal or inclined conveyor, the key attributes for cleated conveyors are the accuracy.
2. What does the below equation represent?
a) Froude number
b) Reynold’s number
c) Sherwood number
d) Kick’s number
Answer: a
Clarification: The type of fluidization can be predicted by criteria of Froude number, where Vmf is minimum velocity of flow over the whole cross section area.
3. Fluidization occurs when, Fr is _____
a) 1.5
b) Zero
c) Infinite
d) Unity
Answer: d
Clarification: When the Froude number is less than unity, particulate fluidization occurs and at higher values aggregative fluidization takes place.
4. If the particle are small, the flow is ______
a) Transient
b) Laminar
c) Turbulent
d) Eddy
Answer: b
Clarification: If the particles is very small, the flow through the channels between the particles will be laminar and pressure drop increases.
5. As the velocity increases, pressure drop ____
a) Increases
b) Decreases
c) Is constant
d) Diverted
Answer: a
Clarification: As the velocity is gradually increased, the pressure drop increase but the particles do not move and the bed height remains same.
6. At the fluidizing point, pressure gradient _____
a) Falls
b) Increases
c) Is zero
d) Is unity
Answer: a
Clarification: At the fluidizing point, the pressure gradient begins to fall because the porosity of the bed increases.
7. Minimum fluidization velocity is calculated by _____
a) Reynold’s equation
b) Dom’s equation
c) Crump equation
d) Ergun’s equation
Answer: d
Clarification: An equation for the minimum fluidization velocity can be obtained by settling the pressure drop across the bed equal to weight of the bed per unit area.
8. What does the below equation represent?
a) Reynold’s equation
b) Schmidt equation
c) Ergun’s equation
d) Froude’s equation
Answer: c
Clarification: The above equation is called as the Ergun’s equation, where the dependence of minimum fluidization velocity on Dp.
9. For low Reynold’s number, the terminal velocity ____
a) Falls
b) Increases
c) Is zero
d) Is unity
Answer: a
Clarification: The terminal velocity for individual particles falling in the still air shows that, for low Reynold’s number.
10. The following equation depends upon ______
a) Void fraction
b) Velocity gradient
c) Entropy
d) Enthalpy
Answer: a
Clarification: The ratio of the terminal velocity and the fluidization velocity mainly depend mainly on the void fraction at minimum fluidization.