ASF Refrigeration Systems and Heat Transfer 2 — Questions and Answers
Question 1: Which type of heat transfer is primarily responsible for distributing cold temperatures inside a refrigerator through air circulation?
- Conduction
- Radiation
- Convection (Correct answer)
- Sublimation
Correct answer: Convection
Convection involves heat transfer through the movement of air; cold air circulating inside the refrigerator removes heat from food items through convection currents.
Question 2: What is the main purpose of the condenser in a refrigeration system?
- To expand the refrigerant and lower its temperature
- To compress the refrigerant vapor to high pressure
- To reject heat from the refrigerant to the surrounding environment (Correct answer)
- To filter moisture and debris from the refrigerant
Correct answer: To reject heat from the refrigerant to the surrounding environment
The condenser removes heat from the high-pressure refrigerant vapor, causing it to condense into a liquid while releasing that heat to the surrounding environment.
Question 3: In a frost-free refrigerator, what component initiates the automatic defrost cycle to remove ice from the evaporator?
- The defrost timer or control board (Correct answer)
- The condenser fan motor
- The thermistor temperature sensor
- The capillary tube metering device
Correct answer: The defrost timer or control board
The defrost timer or electronic control board activates the defrost heater on a timed or adaptive schedule to melt accumulated frost from the evaporator coils.
Question 4: What is the primary function of the filter-drier in a refrigeration system?
- To increase refrigerant pressure before the evaporator
- To remove moisture and contaminants from the refrigerant (Correct answer)
- To regulate refrigerant flow rate to the compressor
- To cool refrigerant vapor before it enters compression
Correct answer: To remove moisture and contaminants from the refrigerant
The filter-drier removes moisture, acid, and debris from the refrigerant to prevent ice blockages at the expansion device and protect system components from corrosion.
Question 5: What is the function of a capillary tube in a refrigeration system?
- To measure refrigerant temperature and pressure
- To act as a fixed metering device controlling refrigerant flow (Correct answer)
- To connect the compressor outlet to the condenser inlet
- To vent excess pressure from the high side of the system
Correct answer: To act as a fixed metering device controlling refrigerant flow
A capillary tube is a fixed-restriction metering device that controls the flow rate of liquid refrigerant from the high-pressure side to the low-pressure side.
Question 6: What does 'COP' stand for when describing refrigeration system efficiency?
- Cooling Output Parameter
- Coefficient of Performance (Correct answer)
- Condenser Outlet Pressure
- Compressor Operating Point
Correct answer: Coefficient of Performance
COP (Coefficient of Performance) is the ratio of useful heat removed from the refrigerated space to the work input required by the compressor, indicating overall system efficiency.
Question 7: Which refrigerant was phased out under the Montreal Protocol due to its ozone-depleting properties?
- R-134a
- R-410A
- R-12 (Freon) (Correct answer)
- R-600a
Correct answer: R-12 (Freon)
R-12 (Freon) is a CFC refrigerant that was phased out under the Montreal Protocol because its chlorine content severely depletes the stratospheric ozone layer.
ASF Refrigeration Systems and Heat Transfer 2
Which type of heat transfer is primarily responsible for distributing cold temperatures inside a refrigerator through air circulation?