Refrigeration and Air Conditioning Mechanic Red Seal Exam
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Sample Refrigeration and Air Conditioning Mechanic Red Seal Exam Practice Questions
This section covers "Compressor"
1. What is the term for the ratio of work done per cycle to the stroke volume of the compressor?
a) Compressor capacity
b) Compression ratio
c) Compressor efficiency
d) Mean effective pressure
2. If the capacity of a compression is 10 m³/minute, what does 10 m³/minute refer to?
a) Standard air
b) Free air
c) Compressed air
d) Compressed air at delivery pressure
3. There is high suction pressure on a heat pump. What is the cause?
a) Low refrigerant charge.
b) Leaking reversing valve.
c) Leaking liquid line solenoid.
d) Restricted liquid line filter-drier.
4. In multi-stage compression compared to single-stage compression, which statement is true?
a) Improves volumetric efficiency for the given pressure ratio
b) Reduces work done per kg of air
c) Reduces cost of compressor
d) Gives more uniform torque
e) All of the above
5. Compression efficiency is compared against which type of compression?
a) Ideal compression
b) Adiabatic compression
c) Both isothermal and adiabatic compression
d) Isothermal compression
6. What is the term for the volume of air delivered by the compressor?
a) Free air delivery
b) Compressor capacity
c) Swept volume
d) None of the above
7. What is the most efficient method of compressing air?
a) Isothermal
b) Adiabatically
c) Isentropically
d) Isochronically
8. The ratio of indicated HP to break HP is known as:
a) Mechanical efficiency
b) Volumetric efficiency
c) Isothermal efficiency
d) Adiabatic efficiency
9. When is the maximum work done in compressing air?
a) Improves volumetric efficiency for the given pressure ratio
b) Isothermal
c) Adiabatic
d) Polytropic
10. What is the term for the value of air sucked by the compressor during its suction stroke?
a) Free air delivery
b) Compressor capacity
c) Swept volume
d) None of the above
11. The ratio of indicated HP to shaft HP is known as:
a) Compressor efficiency
b) Isothermal efficiency
c) Volumetric efficiency
d) Mechanical efficiency
12. What does the volumetric efficiency of air compressors measure?
a) The ratio of stroke volume to clearance volume
b) The ratio of the air delivered to the amount of piston displacement
c) Reciprocal of compression ratio
d) Index of compressor performance
13. What is the typical range of volumetric efficiency for air compressors?
a) 20 to 30%
b) 40 to 50%
c) 60 to 70%
d) 70 to 90%
14. At the beginning of the compression stroke, the pressure of air is compared to atmospheric pressure as:
a) Equal to
b) Less than
c) More than
d) None of the above
15) Why is inter-cooling done in multistage compressors?
a) To cool the air during compression
b) reduce the temperature of the air between stages
c) To enable compression in two stages
d) To minimize the work of compression
16. A manual pump down is required. How is the king valve adjusted?
a) By turning the stem clockwise to the front seat.
b) By turning the stem clockwise to the back seat.
c) By turning the stem counter-clockwise to the front seat.
d) By turning the stem counter-clockwise to the back seat
17. The ratio of compression is the ratio of:
a) Gauge discharge pressure to gauge intake pressure
b) Absolute discharge pressure to absolute intake pressure
c) Stroke volume and clearance volume
d) None of the above
18. What should the cylinder clearance in a compression be?
a) As large as possible
b) As small as possible
c) About 50% of swept volume
d) About 100% of swept volume
19. Where are separators generally installed in compressors?
a) After the intercooler
b) Before the intercooler
c) Before the receiver
d) After the intercooler
20) Euler's equation is applicable for:
Centrifugal compressor
Axial compressor
Pumps
All of the above
a) Compressor capacity
b) Compression ratio
c) Compressor efficiency
d) Mean effective pressure
2. If the capacity of a compression is 10 m³/minute, what does 10 m³/minute refer to?
a) Standard air
b) Free air
c) Compressed air
d) Compressed air at delivery pressure
3. There is high suction pressure on a heat pump. What is the cause?
a) Low refrigerant charge.
b) Leaking reversing valve.
c) Leaking liquid line solenoid.
d) Restricted liquid line filter-drier.
4. In multi-stage compression compared to single-stage compression, which statement is true?
a) Improves volumetric efficiency for the given pressure ratio
b) Reduces work done per kg of air
c) Reduces cost of compressor
d) Gives more uniform torque
e) All of the above
5. Compression efficiency is compared against which type of compression?
a) Ideal compression
b) Adiabatic compression
c) Both isothermal and adiabatic compression
d) Isothermal compression
6. What is the term for the volume of air delivered by the compressor?
a) Free air delivery
b) Compressor capacity
c) Swept volume
d) None of the above
7. What is the most efficient method of compressing air?
a) Isothermal
b) Adiabatically
c) Isentropically
d) Isochronically
8. The ratio of indicated HP to break HP is known as:
a) Mechanical efficiency
b) Volumetric efficiency
c) Isothermal efficiency
d) Adiabatic efficiency
9. When is the maximum work done in compressing air?
a) Improves volumetric efficiency for the given pressure ratio
b) Isothermal
c) Adiabatic
d) Polytropic
10. What is the term for the value of air sucked by the compressor during its suction stroke?
a) Free air delivery
b) Compressor capacity
c) Swept volume
d) None of the above
11. The ratio of indicated HP to shaft HP is known as:
a) Compressor efficiency
b) Isothermal efficiency
c) Volumetric efficiency
d) Mechanical efficiency
12. What does the volumetric efficiency of air compressors measure?
a) The ratio of stroke volume to clearance volume
b) The ratio of the air delivered to the amount of piston displacement
c) Reciprocal of compression ratio
d) Index of compressor performance
13. What is the typical range of volumetric efficiency for air compressors?
a) 20 to 30%
b) 40 to 50%
c) 60 to 70%
d) 70 to 90%
14. At the beginning of the compression stroke, the pressure of air is compared to atmospheric pressure as:
a) Equal to
b) Less than
c) More than
d) None of the above
15) Why is inter-cooling done in multistage compressors?
a) To cool the air during compression
b) reduce the temperature of the air between stages
c) To enable compression in two stages
d) To minimize the work of compression
16. A manual pump down is required. How is the king valve adjusted?
a) By turning the stem clockwise to the front seat.
b) By turning the stem clockwise to the back seat.
c) By turning the stem counter-clockwise to the front seat.
d) By turning the stem counter-clockwise to the back seat
17. The ratio of compression is the ratio of:
a) Gauge discharge pressure to gauge intake pressure
b) Absolute discharge pressure to absolute intake pressure
c) Stroke volume and clearance volume
d) None of the above
18. What should the cylinder clearance in a compression be?
a) As large as possible
b) As small as possible
c) About 50% of swept volume
d) About 100% of swept volume
19. Where are separators generally installed in compressors?
a) After the intercooler
b) Before the intercooler
c) Before the receiver
d) After the intercooler
20) Euler's equation is applicable for:
Centrifugal compressor
Axial compressor
Pumps
All of the above
Answers
- B
- B
- B
- D
- B
- A
- A
- B
- C
- D
- B
- D
- B
- D
- B
- A
- B
- A
- D
- D
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