This set of Food Processing Unit Operations Multiple Choice Questions & Answers (MCQs) focuses on “Fluid Flow Applications – Pumps and Fans”.
1. In a __________ pump, the fluid is drawn into pump and is then forced through outlet.
a) positive displacement
b) jet
c) airlift
d) propeller pumps
View Answer
Explanation: In a positive displacement pump, the fluid is drawn into pump and is then forced through outlet. These pumps can develop high pressure heads but they cannot stand blockages and throttling in the discharge outlet.
2. In _________pumps, the energy of the fluid is converted into velocity energy.
a) positive displacement
b) jet
c) airlift
d) propeller pumps
View Answer
Explanation: In jet pumps, a high velocity jet is produced in a nozzle where the energy of the fluid is converted into velocity energy. Jet pumps have low efficiencies but they have no moving parts and therefore have low initial costs.
3. Which of the following pumps can be used as vacuum pumps?
a) Positive displacement
b) Jet
c) Airlift
d) Propeller pumps
View Answer
Explanation: The jet pumps are used as vacuum pumps.A high velocity jet converts the energy of the fluid into velocity energy in the nozzle. This produces a low pressure area causing the surrounding fluid to be sucked into the pipe.
4. Are these statements about the propeller pumps true?
Statement 1: Propellers are used to impart energy to the fluids.
Statement 2: They have low efficiency.
a) True, False
b) True, True
c) False, True
d) False, False
View Answer
Explanation: Propellers are used to impart energy to the fluids. They are widely used to mix the contents of tanks and in pipes and convey the fluids. They have high efficiency and are used for low heads.
5. The _________pump converts rotational energy of the fluid to velocity and pressure.
a) centrifugal
b) jet
c) airlift
d) propeller pumps
View Answer
Explanation: The centrifugal pumps convert rotational energy of the fluid to velocity and pressure. The fluid to be pumped is taken at the center of the rotor and is passed along the spinning rotor thus producing rotational energy. This rotational energy is then converted into velocity and pressure at the periphery of the disc.
6. Which of the following statements about airlift pumps are correct?
Statement 1: In airlift pumps, the air is introduced above a liquid in pressure level and that pressure is used to discharge the liquid.
Statement 2: Airlift pumps are used to convey powders in fluidized form.
a) True, False
b) True, True
c) False, True
d) False, False
View Answer
Explanation: In airlift pumps, the air is introduced above a liquid in pressure level and that pressure is used to discharge the liquid. In case of powders, air is blown up through a bed of powder to convey it in the fluidized form. They are convenient for the materials which cannot be passed easily through valves and ports.
7. What is significance of fan law?
a) It deals with pressure and velocity of the fan
b) It deals with pressure and power consumption of the fan
c) It deals with performance of the fan and power consumption of the fan
d) It deals with performance of the fan velocity of the fan
View Answer
Explanation: Fan law gives the relationship between performance of the fan and power consumption of the fan. This estimates the operation conditions of the fan under different speeds, fluid density, impeller diameter.
8. The efficiency of the pump is ratio of ____________
a) energy to velocity and pressure
b) energy to velocity
c) energy to pressure
d) velocity and pressure to energy
View Answer
Explanation: The efficiency of the pump is the ratio of the energy supplied by the motor to the increase in velocity and pressure energy given to the fluid. Propellers pumps and centrifugal pumps have high efficiency. Jet pumps and airlift pumps are less efficiency.
9. What are the factors to be considered for designing a centrifugal pump?
a) Capacity, Rotational speed only
b) Rotational speed only
c) Pump, Rotational speed only
d) Capacity, rotational speed and pump
View Answer
Explanation: Capacity, rotational speed and pump are the factors to be considered for designing a centrifugal pump. The capacity of the pump varies with its rotational speed, the pressure developed by pump varies as the square of the rotational speed and power required by pump varies as the cube of the rotational speed. These relationships are called as Fans Laws.
10. Are pumps and fans used for conveying gases?
a) True
b) False
View Answer
Explanation: True, both pumps and fans are used for conveying materials. A fan moves large amount of gas with low increase in pressure. It pushes the volume of gas with the help of its blades. Pumps are the machines that are used for raising liquid or a relatively incompressible fluid to a higher pressure or higher level.
Sanfoundry Global Education & Learning Series – Food Processing Unit Operations.
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