This set of Fluid Mechanics Multiple Choice Questions & Answers (MCQs) focuses on “Effect of Acceleration in Suction and Delivery Pipes on Indicator Diagrams”.
1. What is the full form of NPSH?
a) Net pipe suction head
b) Net positive suction head
c) Non-positive suction head
d) Non-polar suction head
View Answer
Explanation: The full form of NPSH is net positive suction head. It is defined as the margin of pressure over vapour pressure. It happens at the pump suction nozzle.
2. What is the formula for NPSH?
a) Ps-Pvap
b) Vs-Vvap
c) Ts-Tvap
d) Ms-Mvap
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Explanation: NPSH is defined as the margin of pressure over vapour pressure. It happens at the pump suction nozzle. It is the difference between the suction pressure and vapour pressure. Thus, the correct option is Ps-Pvap.
3. What is absolute pressure?
a) Momentum pressure to thermal pressure
b) Thermal pressure to momentum pressure
c) Atmospheric pressure plus gauge pressure
d) Atmospheric pressure by gauge pressure
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Explanation: Absolute pressure is defined as the summation of Atmospheric pressure plus gauge pressure. This equation provides the answer in units of pressure. The obtained psi can be converted to units of head.
4. What is the unit of NPSH?
a) kPa
b) kgm
c) kg/m
d) kg
View Answer
Explanation: Unit of NPSH can be expressed as units of specific energies. All the units in NPSH are psi units. The psi units are kilopascal, bar, pounds per square inch etc. So, kPa is the correct option.
5. What does ‘g’ in psig mean?
a) Pressure is measured below absolute pressure
b) Pressure is measured above absolute pressure
c) Pressure is measured below absolute zero
d) Pressure is measured above absolute zero
View Answer
Explanation: All the units in NPSH are psi units. The psi units are kilopascal, bar, pounds per square inch etc. The ‘g’ in psig indicates that the pressure is measured above the absolute pressure.
6. What does ‘a’ in psia mean?
a) Pressure is measured below absolute pressure
b) Pressure is measured above absolute pressure
c) Pressure is measured below absolute zero
d) Pressure is measured above absolute zero
View Answer
Explanation: All the units in NPSH are psi units. The psi units are kilopascal, bar, pounds per square inch etc. The ‘a’ in psia indicates that the pressure is measured above absolute zero which is a perfect vacuum.
7. Which among the following happens at the first half of NPSH?
a) Vapour pressure
b) Atmospheric pressure
c) Suction pressure
d) Discharge pressure
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Explanation: During the first half of the NPSH, the suction of air takes place. For the suction of an air, a strong suction pressure is required. Sometimes, the elevation of gauge must also be added. But, most of the times it is considered negligible.
8. Which among the following happens in the second half of NPSH?
a) Vapour pressure
b) Atmospheric pressure
c) Suction pressure
d) Discharge pressure
View Answer
Explanation: During the second half of the NPSH, vapour pressure is more difficult to determine. It is a measure of the desire of liquids. Cool water has a low vapour pressure. Thus, the option is Vapour pressure.
9. Vapour pressure depends on_______
a) Pressure
b) Temperature
c) Density
d) Viscosity
View Answer
Explanation: Vapour pressure depends on temperature only. With the increase in temperature, the vapour pressure increases. It increases until it reaches the critical temperature. At the critical temperature, the vapour pressure tends to slowly vanish.
10. Which among the following is not a type of pipe?
a) Stainless steel pipes
b) PVC piping
c) Brass pipes
d) Wooden pipes
View Answer
Explanation: Wooden pipes for transportation and other important facilities is not feasible. Wood has various properties against water. Water flowing through the wooden pipe will slowly reduce the strength of the wood which may lead to cracks.
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