FDNY Z-51 Refrigeration Exam 2026/2027 | Complete RSOE
Fundamentals Study Guide – 350+ Actual Questions with
Verified Answers & Detailed Rationales | Graded A+
Questions 1–100: Refrigeration Fundamentals, Theory & Calculations
1. What is the primary purpose of a refrigeration system?
A. Add heat to a space
B. Transfer heat from a lower-temperature area to a higher-temperature
area
C. Produce electricity
D. Increase humidity
Answer: B
Rationale: Refrigeration systems remove heat from a low-temperature
region and reject it to a higher-temperature environment.
2. Which four components form the basic vapor-compression
refrigeration cycle?
A. Boiler, pump, turbine, condenser
B. Compressor, condenser, expansion device, evaporator
C. Cooling tower, pump, boiler, receiver
D. Evaporator, cooling tower, fan, heater
Answer: B
Rationale: These four components provide compression, heat rejection,
pressure reduction, and heat absorption.
3. What is the primary function of a compressor?
A. Lower refrigerant pressure
B. Raise refrigerant vapor pressure
,C. Remove oil
D. Store liquid refrigerant
Answer: B
Rationale: The compressor raises the pressure and usually temperature
of refrigerant vapor before condensation.
4. What occurs in the condenser?
A. Refrigerant absorbs heat
B. Refrigerant rejects heat
C. Refrigerant pressure drops through a metering device
D. Refrigerant is compressed
Answer: B
Rationale: The condenser rejects heat from the refrigerant to air, water,
or another heat-transfer medium.
5. What occurs in the evaporator?
A. Refrigerant rejects heat
B. Refrigerant absorbs heat
C. Refrigerant is compressed
D. Oil is separated
Answer: B
Rationale: Evaporation allows refrigerant to absorb heat from the
refrigerated or conditioned space.
6. What is the purpose of an expansion device?
A. Increase liquid pressure
B. Reduce refrigerant pressure
C. Compress vapor
D. Remove noncondensables
Answer: B
,Rationale: The expansion device creates a pressure drop that reduces
the refrigerant saturation temperature.
7. Refrigerant entering an evaporator is generally at what condition?
A. High-pressure liquid only
B. Low-pressure liquid-vapor mixture
C. High-pressure superheated vapor
D. Atmospheric air
Answer: B
Rationale: Pressure reduction causes part of the liquid to flash into
vapor, producing a cold mixture entering the evaporator.
8. What is superheated vapor?
A. Vapor below saturation temperature
B. Vapor at saturation temperature
C. Vapor above its saturation temperature at a given pressure
D. Liquid above boiling point
Answer: C
Rationale: Superheat is the temperature of vapor above its saturation
temperature at the same pressure.
9. What is subcooled liquid?
A. Liquid below its saturation temperature at a given pressure
B. Vapor below saturation
C. Liquid above saturation
D. Gas mixed with oil
Answer: A
Rationale: Subcooling indicates liquid has been cooled below its
saturation temperature.
, 10. What does saturation temperature represent?
A. The temperature at which a substance changes phase at a specified
pressure
B. Room temperature
C. Compressor discharge temperature only
D. Ambient temperature only
Answer: A
Rationale: Saturation temperature and pressure are directly related for
a refrigerant.
11. What happens to refrigerant saturation temperature when
pressure increases?
A. It generally increases
B. It always decreases
C. It becomes zero
D. It is unaffected
Answer: A
Rationale: For a given refrigerant, higher pressure corresponds to
higher saturation temperature.
12. What is latent heat?
A. Heat associated with temperature change only
B. Heat associated with phase change without temperature change
C. Electrical heat
D. Friction heat only
Answer: B
Rationale: Latent heat causes a substance to change phase while its
temperature remains essentially constant during the phase change.
Fundamentals Study Guide – 350+ Actual Questions with
Verified Answers & Detailed Rationales | Graded A+
Questions 1–100: Refrigeration Fundamentals, Theory & Calculations
1. What is the primary purpose of a refrigeration system?
A. Add heat to a space
B. Transfer heat from a lower-temperature area to a higher-temperature
area
C. Produce electricity
D. Increase humidity
Answer: B
Rationale: Refrigeration systems remove heat from a low-temperature
region and reject it to a higher-temperature environment.
2. Which four components form the basic vapor-compression
refrigeration cycle?
A. Boiler, pump, turbine, condenser
B. Compressor, condenser, expansion device, evaporator
C. Cooling tower, pump, boiler, receiver
D. Evaporator, cooling tower, fan, heater
Answer: B
Rationale: These four components provide compression, heat rejection,
pressure reduction, and heat absorption.
3. What is the primary function of a compressor?
A. Lower refrigerant pressure
B. Raise refrigerant vapor pressure
,C. Remove oil
D. Store liquid refrigerant
Answer: B
Rationale: The compressor raises the pressure and usually temperature
of refrigerant vapor before condensation.
4. What occurs in the condenser?
A. Refrigerant absorbs heat
B. Refrigerant rejects heat
C. Refrigerant pressure drops through a metering device
D. Refrigerant is compressed
Answer: B
Rationale: The condenser rejects heat from the refrigerant to air, water,
or another heat-transfer medium.
5. What occurs in the evaporator?
A. Refrigerant rejects heat
B. Refrigerant absorbs heat
C. Refrigerant is compressed
D. Oil is separated
Answer: B
Rationale: Evaporation allows refrigerant to absorb heat from the
refrigerated or conditioned space.
6. What is the purpose of an expansion device?
A. Increase liquid pressure
B. Reduce refrigerant pressure
C. Compress vapor
D. Remove noncondensables
Answer: B
,Rationale: The expansion device creates a pressure drop that reduces
the refrigerant saturation temperature.
7. Refrigerant entering an evaporator is generally at what condition?
A. High-pressure liquid only
B. Low-pressure liquid-vapor mixture
C. High-pressure superheated vapor
D. Atmospheric air
Answer: B
Rationale: Pressure reduction causes part of the liquid to flash into
vapor, producing a cold mixture entering the evaporator.
8. What is superheated vapor?
A. Vapor below saturation temperature
B. Vapor at saturation temperature
C. Vapor above its saturation temperature at a given pressure
D. Liquid above boiling point
Answer: C
Rationale: Superheat is the temperature of vapor above its saturation
temperature at the same pressure.
9. What is subcooled liquid?
A. Liquid below its saturation temperature at a given pressure
B. Vapor below saturation
C. Liquid above saturation
D. Gas mixed with oil
Answer: A
Rationale: Subcooling indicates liquid has been cooled below its
saturation temperature.
, 10. What does saturation temperature represent?
A. The temperature at which a substance changes phase at a specified
pressure
B. Room temperature
C. Compressor discharge temperature only
D. Ambient temperature only
Answer: A
Rationale: Saturation temperature and pressure are directly related for
a refrigerant.
11. What happens to refrigerant saturation temperature when
pressure increases?
A. It generally increases
B. It always decreases
C. It becomes zero
D. It is unaffected
Answer: A
Rationale: For a given refrigerant, higher pressure corresponds to
higher saturation temperature.
12. What is latent heat?
A. Heat associated with temperature change only
B. Heat associated with phase change without temperature change
C. Electrical heat
D. Friction heat only
Answer: B
Rationale: Latent heat causes a substance to change phase while its
temperature remains essentially constant during the phase change.
