313D Fundamentals of Air Conditioning Systems 2 — Questions and Answers
Question 1: What is the primary purpose of a metering device in a refrigeration circuit?
- To compress the refrigerant vapor
- To reduce refrigerant pressure and control flow into the evaporator (Correct answer)
- To transfer heat from the refrigerant to outdoor air
- To filter moisture from the refrigerant
Correct answer: To reduce refrigerant pressure and control flow into the evaporator
The metering device drops refrigerant pressure and regulates flow into the evaporator, enabling it to absorb heat effectively.
Question 2: Which refrigerant cycle process occurs in the condenser?
- Evaporation at low pressure
- Heat absorption from indoor air
- Condensation and heat rejection to outdoor air (Correct answer)
- Pressure reduction through a fixed orifice
Correct answer: Condensation and heat rejection to outdoor air
In the condenser, high-pressure refrigerant vapor releases heat to the outside air and condenses into a liquid.
Question 3: What does superheat measure in an air conditioning system?
- Temperature of liquid refrigerant leaving the condenser
- Temperature rise of refrigerant vapor above its saturation temperature (Correct answer)
- Pressure difference across the compressor
- Subcooling of liquid refrigerant before the metering device
Correct answer: Temperature rise of refrigerant vapor above its saturation temperature
Superheat is the number of degrees the refrigerant vapor has risen above its boiling point at a given pressure.
Question 4: A residential split system has the evaporator coil located in the:
- Outdoor condenser cabinet
- Compressor compartment
- Indoor air handler or furnace plenum (Correct answer)
- Condensate drain pan only
Correct answer: Indoor air handler or furnace plenum
In a split system, the evaporator coil is installed indoors in the air handler or above the furnace to cool circulating air.
Question 5: What is subcooling in a refrigeration system?
- Cooling the compressor discharge gas below ambient
- Chilling the refrigerant liquid below its condensing saturation temperature (Correct answer)
- Reducing suction pressure at the compressor inlet
- Lowering indoor humidity below the dew point
Correct answer: Chilling the refrigerant liquid below its condensing saturation temperature
Subcooling is the number of degrees the liquid refrigerant is cooled below its saturation condensing temperature, improving system efficiency.
Question 6: In a vapor-compression cycle, which component raises refrigerant pressure and temperature?
- Evaporator
- Thermostatic expansion valve
- Compressor (Correct answer)
- Filter-drier
Correct answer: Compressor
The compressor draws in low-pressure vapor and raises it to high pressure and temperature before sending it to the condenser.
Question 7: What effect does a dirty evaporator coil have on system performance?
- Increases suction pressure and improves cooling capacity
- Reduces airflow and causes low suction pressure and possible coil freezing (Correct answer)
- Raises condenser pressure and lowers superheat
- Has no measurable effect on operating pressures
Correct answer: Reduces airflow and causes low suction pressure and possible coil freezing
A dirty evaporator restricts airflow, which lowers heat absorption, reduces suction pressure, and can cause ice formation on the coil.
313D Fundamentals of Air Conditioning Systems 2
What is the primary purpose of a metering device in a refrigeration circuit?