313D Refrigeration Cycle Fundamentals Questions and Answers

Question 1

In a standard refrigeration cycle, what is the primary function of the compressor?

Accepted Answer

To increase the pressure and temperature of the refrigerant vapor.

Answer

The compressor acts as the heart of the system, taking in low-pressure, low-temperature refrigerant vapor and compressing it into a high-pressure, high-temperature vapor. This process is essential for moving the refrigerant through the cycle and enabling heat transfer in the condenser.

Question 2

A residential air conditioning system is running, but the indoor unit is not blowing cold air. A technician measures the refrigerant state at the outlet of the evaporator coil and finds it is a saturated mixture. What does this condition most likely indicate?

Accepted Answer

The metering device is allowing too much refrigerant into the evaporator.

Answer

The refrigerant should leave the evaporator as a superheated vapor, meaning it has absorbed enough heat to completely boil off and then some. A saturated mixture (part liquid, part vapor) at the outlet indicates that not all the liquid refrigerant has boiled off, a condition known as 'flooding.' This is often caused by an overfeeding metering device or a severely restricted airflow over the evaporator.

Question 3

Which of the following describes the state of the refrigerant as it enters the metering device in a properly functioning air conditioning system?

Accepted Answer

High-pressure, warm liquid

Answer

After leaving the condenser, the refrigerant has rejected heat to the outdoors and has condensed from a high-pressure vapor into a high-pressure, warm liquid. This subcooled liquid then flows to the metering device.

Question 4

What is the primary purpose of the subcooling process that occurs in the condenser?

Accepted Answer

To prevent flash gas from forming before the metering device.

Answer

Subcooling is the process of cooling the liquid refrigerant below its saturation temperature after it has fully condensed. This ensures that a solid column of liquid refrigerant reaches the metering device, preventing bubbles of vapor (flash gas) from forming prematurely, which would reduce the efficiency of the metering device and the evaporator.

Question 5

During the refrigeration cycle, where does the refrigerant absorb heat from the space being cooled, causing it to change from a liquid to a vapor?

Accepted Answer

In the evaporator

Answer

The evaporator is the component located inside the space being cooled. As the low-pressure, low-temperature liquid refrigerant flows through the evaporator coil, it absorbs heat from the indoor air, causing the refrigerant to boil and change into a low-pressure vapor.

(313D) Residential Air Conditioning Systems Mechanic Certification Practice Test

(313D) Residential Air Conditioning Systems Mechanic Certification Practice Test

313D Refrigeration Cycle Fundamentals Questions and Answers