FDNY Z-51 WRITTEN EXAM PRACTICE QUESTIONS.LATEST UPDATES
ALREADY GRADED A+|2026/2027
Section 1: Refrigeration Cycle Theory & Thermodynamics (Questions 1-15)
Question 1
What are the four primary components of a vapor-compression refrigeration
cycle?
A. Compressor, receiver, expansion valve, accumulator
B. Compressor, condenser, expansion valve, evaporator
C. Condenser, evaporator, filter-drier, receiver
D. Compressor, condenser, filter-drier, accumulator
Correct Answer: B
Rationale: The four essential components of a vapor-compression refrigeration
cycle are the compressor, condenser, expansion valve (metering device), and
evaporator. These components work together to circulate refrigerant, absorb
heat from the conditioned space, and reject it to the environment. The receiver,
,accumulator, and filter-drier are auxiliary components that support the cycle but
are not considered primary components .
Question 2
What is the primary function of the compressor in a refrigeration system?
A. To absorb heat from the refrigerated space
B. To remove heat from the refrigerant
C. To increase the pressure and temperature of the refrigerant vapor
D. To reduce the pressure of the refrigerant liquid
Correct Answer: C
Rationale: The compressor's primary function is to draw low-pressure, low-
temperature refrigerant vapor from the evaporator and compress it, significantly
increasing both its pressure and temperature. This high-pressure, high-
temperature vapor is then discharged to the condenser where heat is rejected .
Question 3
In which component of the refrigeration cycle does the refrigerant change from a
liquid to a vapor?
,A. Compressor
B. Condenser
C. Evaporator
D. Expansion valve
Correct Answer: C
Rationale: The evaporator absorbs heat from the space or product being cooled.
Low-pressure liquid refrigerant enters the evaporator and boils, changing to vapor
while absorbing latent heat from the surroundings .
Question 4
The heat removed from the refrigerant in a condenser is:
A. Sensible heat only
B. Latent heat only
C. Sensible and latent heat
D. Neither sensible nor latent heat
Correct Answer: C
, Rationale: The condenser removes both sensible and latent heat from the
refrigerant. Desuperheating removes sensible heat, condensing removes latent
heat, and subcooling removes additional sensible heat .
Question 5
What is the primary purpose of subcooling refrigerant in the condenser?
A. To increase compressor discharge temperature
B. To ensure pure liquid refrigerant enters the metering device
C. To reduce condenser water flow
D. To increase evaporator pressure
Correct Answer: B
Rationale: Subcooling ensures that a pure liquid refrigerant (with no flash gas)
enters the metering device. This prevents vapor from entering the expansion
valve, which would reduce its capacity and efficiency .
Question 6
ALREADY GRADED A+|2026/2027
Section 1: Refrigeration Cycle Theory & Thermodynamics (Questions 1-15)
Question 1
What are the four primary components of a vapor-compression refrigeration
cycle?
A. Compressor, receiver, expansion valve, accumulator
B. Compressor, condenser, expansion valve, evaporator
C. Condenser, evaporator, filter-drier, receiver
D. Compressor, condenser, filter-drier, accumulator
Correct Answer: B
Rationale: The four essential components of a vapor-compression refrigeration
cycle are the compressor, condenser, expansion valve (metering device), and
evaporator. These components work together to circulate refrigerant, absorb
heat from the conditioned space, and reject it to the environment. The receiver,
,accumulator, and filter-drier are auxiliary components that support the cycle but
are not considered primary components .
Question 2
What is the primary function of the compressor in a refrigeration system?
A. To absorb heat from the refrigerated space
B. To remove heat from the refrigerant
C. To increase the pressure and temperature of the refrigerant vapor
D. To reduce the pressure of the refrigerant liquid
Correct Answer: C
Rationale: The compressor's primary function is to draw low-pressure, low-
temperature refrigerant vapor from the evaporator and compress it, significantly
increasing both its pressure and temperature. This high-pressure, high-
temperature vapor is then discharged to the condenser where heat is rejected .
Question 3
In which component of the refrigeration cycle does the refrigerant change from a
liquid to a vapor?
,A. Compressor
B. Condenser
C. Evaporator
D. Expansion valve
Correct Answer: C
Rationale: The evaporator absorbs heat from the space or product being cooled.
Low-pressure liquid refrigerant enters the evaporator and boils, changing to vapor
while absorbing latent heat from the surroundings .
Question 4
The heat removed from the refrigerant in a condenser is:
A. Sensible heat only
B. Latent heat only
C. Sensible and latent heat
D. Neither sensible nor latent heat
Correct Answer: C
, Rationale: The condenser removes both sensible and latent heat from the
refrigerant. Desuperheating removes sensible heat, condensing removes latent
heat, and subcooling removes additional sensible heat .
Question 5
What is the primary purpose of subcooling refrigerant in the condenser?
A. To increase compressor discharge temperature
B. To ensure pure liquid refrigerant enters the metering device
C. To reduce condenser water flow
D. To increase evaporator pressure
Correct Answer: B
Rationale: Subcooling ensures that a pure liquid refrigerant (with no flash gas)
enters the metering device. This prevents vapor from entering the expansion
valve, which would reduce its capacity and efficiency .
Question 6
