ASF Refrigeration Systems and Heat Transfer 1 — Questions and Answers
Question 1: What is the primary function of a refrigerant in a cooling system?
- To lubricate compressor components
- To absorb heat from the refrigerated space and release it outside (Correct answer)
- To prevent frost buildup on the evaporator
- To regulate electrical current to the compressor
Correct answer: To absorb heat from the refrigerated space and release it outside
Refrigerant absorbs heat in the evaporator and releases it in the condenser, effectively transferring heat out of the refrigerated space.
Question 2: In a refrigeration cycle, where does the refrigerant absorb heat from the surrounding environment?
- Condenser
- Compressor
- Evaporator (Correct answer)
- Expansion valve
Correct answer: Evaporator
The evaporator is the component where the refrigerant absorbs heat from the surrounding air or food, causing it to evaporate into a gas.
Question 3: What is the primary role of the compressor in a refrigeration system?
- To cool the refrigerant by expanding it
- To filter contaminants from the refrigerant
- To increase the pressure and temperature of the refrigerant vapor (Correct answer)
- To condense the refrigerant from gas to liquid
Correct answer: To increase the pressure and temperature of the refrigerant vapor
The compressor raises the pressure and temperature of the refrigerant vapor so it can effectively release heat in the condenser.
Question 4: What happens to refrigerant as it passes through the expansion valve?
- Its pressure and temperature increase significantly
- Its pressure and temperature decrease rapidly (Correct answer)
- It converts from gas to liquid immediately
- It absorbs heat from the condenser coils
Correct answer: Its pressure and temperature decrease rapidly
As refrigerant passes through the expansion valve, its pressure and temperature drop rapidly, preparing it to absorb heat in the evaporator.
Question 5: Which refrigerant is commonly used in modern household refrigerators due to its low global warming potential?
- R-12
- R-22
- R-134a
- R-600a (isobutane) (Correct answer)
Correct answer: R-600a (isobutane)
R-600a (isobutane) has a very low global warming potential and is widely used in modern energy-efficient household refrigerators as an eco-friendly alternative.
Question 6: What is 'superheat' in the context of a refrigeration system?
- The temperature increase of the refrigerant in the condenser
- The additional heat in refrigerant vapor above its saturation temperature at a given pressure (Correct answer)
- The maximum operating temperature the compressor can safely sustain
- The heat released by the condenser coils to the surrounding air
Correct answer: The additional heat in refrigerant vapor above its saturation temperature at a given pressure
Superheat is the additional temperature above the boiling point of the refrigerant at a given pressure, ensuring only vapor enters the compressor to prevent damage.
Question 7: What is 'subcooling' in a refrigeration system?
- Cooling the refrigerant vapor below the evaporator temperature
- Reducing the condenser temperature below ambient air temperature
- Cooling liquid refrigerant below its condensing saturation temperature (Correct answer)
- The process of intentionally freezing the evaporator coils
Correct answer: Cooling liquid refrigerant below its condensing saturation temperature
Subcooling is the process of cooling liquid refrigerant below its saturation temperature after the condenser, which improves system efficiency and prevents flash gas.
ASF Refrigeration Systems and Heat Transfer 1
What is the primary function of a refrigerant in a cooling system?