AR RF Refrigeration Contractor Exam
Questions and Correct Answers
(Verified Answers) Plus Rationale 2027
Q&A| Instant Download Pdf
Question 1
What is the primary function of the evaporator in a vapor-compression
refrigeration system?
A. To reject heat from the refrigerant to the outdoor air
B. To increase the refrigerant pressure
C. To absorb heat from the refrigerated space as the refrigerant
evaporates
D. To remove moisture from the compressor oil
Rationale: The evaporator absorbs heat from the space or product
being cooled. Low-pressure refrigerant enters the evaporator and
,absorbs energy as it changes from a liquid-vapor mixture into vapor.
This heat absorption produces the cooling effect. The condenser, by
contrast, rejects heat, while the compressor raises refrigerant
pressure.
Question 2
Which component raises the pressure and temperature of refrigerant
vapor before it enters the condenser?
A. Evaporator
B. Receiver
C. Expansion valve
D. Compressor
Rationale: The compressor draws low-pressure refrigerant vapor from
the evaporator and compresses it into a high-pressure, high-
temperature vapor. This pressure increase allows the refrigerant to
reject heat at a temperature above that of the surrounding air or
cooling water in the condenser.
Question 3
What is the primary purpose of the condenser?
A. To absorb heat from the refrigerated space
,B. To reject heat from the refrigerant to the surrounding environment
C. To reduce refrigerant pressure before the evaporator
D. To separate oil from the refrigerant
Rationale: The condenser removes heat from the hot, high-pressure
refrigerant vapor discharged by the compressor. The refrigerant first
desuperheats, then condenses into a liquid, and may undergo
additional subcooling. The heat rejected includes both the heat
absorbed in the evaporator and the heat added by compressor work.
Question 4
What is the primary function of a thermostatic expansion valve (TXV)?
A. To maintain a constant compressor discharge temperature
B. To regulate condenser fan speed
C. To regulate refrigerant flow into the evaporator in response to
superheat
D. To maintain a fixed refrigerant charge
Rationale: A TXV meters refrigerant into the evaporator to maintain a
target superheat at the evaporator outlet. It responds to sensing-bulb
temperature, evaporator pressure, and the valve's spring force.
Proper operation helps maintain effective evaporator utilization while
, preventing excessive liquid refrigerant from returning to the
compressor.
Question 5
What does superheat represent in a refrigeration system?
A. The temperature of liquid refrigerant above its condensing
temperature
B. The difference between outdoor temperature and evaporator
temperature
C. The pressure difference between the compressor inlet and outlet
D. The temperature of refrigerant vapor above its saturation
temperature at the same pressure
Rationale: Superheat is calculated by subtracting the saturation
temperature corresponding to the measured refrigerant pressure from
the actual vapor temperature. It indicates how much the vapor has
been heated beyond the point at which it finished evaporating.
Superheat measurements are useful for evaluating evaporator
feeding and protecting the compressor from liquid refrigerant return.
Question 6
What is subcooling in a refrigeration system?
Questions and Correct Answers
(Verified Answers) Plus Rationale 2027
Q&A| Instant Download Pdf
Question 1
What is the primary function of the evaporator in a vapor-compression
refrigeration system?
A. To reject heat from the refrigerant to the outdoor air
B. To increase the refrigerant pressure
C. To absorb heat from the refrigerated space as the refrigerant
evaporates
D. To remove moisture from the compressor oil
Rationale: The evaporator absorbs heat from the space or product
being cooled. Low-pressure refrigerant enters the evaporator and
,absorbs energy as it changes from a liquid-vapor mixture into vapor.
This heat absorption produces the cooling effect. The condenser, by
contrast, rejects heat, while the compressor raises refrigerant
pressure.
Question 2
Which component raises the pressure and temperature of refrigerant
vapor before it enters the condenser?
A. Evaporator
B. Receiver
C. Expansion valve
D. Compressor
Rationale: The compressor draws low-pressure refrigerant vapor from
the evaporator and compresses it into a high-pressure, high-
temperature vapor. This pressure increase allows the refrigerant to
reject heat at a temperature above that of the surrounding air or
cooling water in the condenser.
Question 3
What is the primary purpose of the condenser?
A. To absorb heat from the refrigerated space
,B. To reject heat from the refrigerant to the surrounding environment
C. To reduce refrigerant pressure before the evaporator
D. To separate oil from the refrigerant
Rationale: The condenser removes heat from the hot, high-pressure
refrigerant vapor discharged by the compressor. The refrigerant first
desuperheats, then condenses into a liquid, and may undergo
additional subcooling. The heat rejected includes both the heat
absorbed in the evaporator and the heat added by compressor work.
Question 4
What is the primary function of a thermostatic expansion valve (TXV)?
A. To maintain a constant compressor discharge temperature
B. To regulate condenser fan speed
C. To regulate refrigerant flow into the evaporator in response to
superheat
D. To maintain a fixed refrigerant charge
Rationale: A TXV meters refrigerant into the evaporator to maintain a
target superheat at the evaporator outlet. It responds to sensing-bulb
temperature, evaporator pressure, and the valve's spring force.
Proper operation helps maintain effective evaporator utilization while
, preventing excessive liquid refrigerant from returning to the
compressor.
Question 5
What does superheat represent in a refrigeration system?
A. The temperature of liquid refrigerant above its condensing
temperature
B. The difference between outdoor temperature and evaporator
temperature
C. The pressure difference between the compressor inlet and outlet
D. The temperature of refrigerant vapor above its saturation
temperature at the same pressure
Rationale: Superheat is calculated by subtracting the saturation
temperature corresponding to the measured refrigerant pressure from
the actual vapor temperature. It indicates how much the vapor has
been heated beyond the point at which it finished evaporating.
Superheat measurements are useful for evaluating evaporator
feeding and protecting the compressor from liquid refrigerant return.
Question 6
What is subcooling in a refrigeration system?
