1. The primary function of a refrigeration cycle is to:
A. Increase air pressure
B. Transfer heat from a low-temperature area to a high-temperature area
C. Produce mechanical power
D. Create combustion gases
Answer: B
Explanation: The refrigeration cycle absorbs heat from a low-temperature
environment (evaporator) and rejects it into a higher-temperature environment
(condenser).
2. In a basic refrigeration cycle, which component is the “heart” of the
system?
A. Evaporator
B. Compressor
C. Condenser
D. Metering device
Answer: B
Explanation: The compressor maintains refrigerant flow and pressure
difference, enabling heat transfer.
3. What does a TXV (Thermostatic Expansion Valve) regulate?
A. Compressor speed
B. Evaporator superheat
C. Condenser subcooling
D. Discharge pressure
,Answer: B
Explanation: TXVs control refrigerant flow based on evaporator outlet
superheat, ensuring proper cooling and preventing liquid refrigerant from
reaching the compressor.
4. Which refrigerant is commonly used in medium-temperature
commercial air conditioning?
A. R-134a
B. R-404A
C. R-717
D. R-744
Answer: A
Explanation: R-134a is widely used in AC systems. R-404A is for low-temp
refrigeration, R-717 (ammonia) for industrial, and R-744 (CO₂) for specialized
systems.
5. The “latent heat of vaporization” refers to:
A. Heat absorbed during phase change without temperature rise
B. Heat released when temperature decreases
C. Sensible heat absorbed during warming
D. Work done by compressor
Answer: A
Explanation: Latent heat allows refrigerant to change state (liquid ↔ vapor)
without changing temperature, critical to refrigeration.
6. What is the primary risk of liquid refrigerant entering the compressor?
A. Overheating
B. Liquid slugging
C. Excessive subcooling
D. Cavitation
,Answer: B
Explanation: Compressors are designed to compress vapor, not liquid. Liquid
slugging can damage valves, pistons, and bearings.
7. Which safety device protects against excessive high-side pressure?
A. Low-pressure switch
B. Expansion valve
C. High-pressure cutout
D. Crankcase heater
Answer: C
Explanation: A high-pressure cutout automatically stops the compressor when
discharge pressure is too high.
8. In psychrometrics, the term “relative humidity” means:
A. Actual humidity in grains per pound of air
B. Ratio of actual water vapor to maximum possible at that temperature
C. Total enthalpy of air-water mixture
D. Dew point temperature
Answer: B
Explanation: Relative humidity is a percentage comparing current water vapor
content to the maximum possible at the same temperature.
9. The dew point temperature is:
A. The point where sensible cooling begins
B. The temperature at which air is fully saturated and condensation starts
C. Always lower than dry bulb temperature
D. The difference between wet bulb and dry bulb
Answer: B
Explanation: Dew point is when air cannot hold more moisture, and
condensation occurs.
, 10. A centrifugal chiller uses which principle for compression?
A. Reciprocating action
B. Screw rotation
C. Dynamic impeller acceleration
D. Scroll movement
Answer: C
Explanation: Centrifugal chillers accelerate refrigerant vapor with an impeller,
converting velocity energy into pressure.
11. What is the function of an economizer in a cooling system?
A. Increases compressor speed
B. Enhances subcooling to improve efficiency
C. Provides emergency shutoff
D. Reduces condenser water flow
Answer: B
Explanation: Economizers use flash gas to subcool liquid refrigerant,
improving efficiency.
12. Which law states that “pressure of a gas is directly proportional to
temperature when volume is constant”?
A. Boyle’s Law
B. Dalton’s Law
C. Charles’ Law
D. Gay-Lussac’s Law
Answer: D
Explanation: Gay-Lussac’s Law defines the pressure-temperature relationship
at constant volume.
13. A chiller operating at too low suction pressure may indicate:
A. Dirty condenser tubes
B. Insufficient refrigerant charge
A. Increase air pressure
B. Transfer heat from a low-temperature area to a high-temperature area
C. Produce mechanical power
D. Create combustion gases
Answer: B
Explanation: The refrigeration cycle absorbs heat from a low-temperature
environment (evaporator) and rejects it into a higher-temperature environment
(condenser).
2. In a basic refrigeration cycle, which component is the “heart” of the
system?
A. Evaporator
B. Compressor
C. Condenser
D. Metering device
Answer: B
Explanation: The compressor maintains refrigerant flow and pressure
difference, enabling heat transfer.
3. What does a TXV (Thermostatic Expansion Valve) regulate?
A. Compressor speed
B. Evaporator superheat
C. Condenser subcooling
D. Discharge pressure
,Answer: B
Explanation: TXVs control refrigerant flow based on evaporator outlet
superheat, ensuring proper cooling and preventing liquid refrigerant from
reaching the compressor.
4. Which refrigerant is commonly used in medium-temperature
commercial air conditioning?
A. R-134a
B. R-404A
C. R-717
D. R-744
Answer: A
Explanation: R-134a is widely used in AC systems. R-404A is for low-temp
refrigeration, R-717 (ammonia) for industrial, and R-744 (CO₂) for specialized
systems.
5. The “latent heat of vaporization” refers to:
A. Heat absorbed during phase change without temperature rise
B. Heat released when temperature decreases
C. Sensible heat absorbed during warming
D. Work done by compressor
Answer: A
Explanation: Latent heat allows refrigerant to change state (liquid ↔ vapor)
without changing temperature, critical to refrigeration.
6. What is the primary risk of liquid refrigerant entering the compressor?
A. Overheating
B. Liquid slugging
C. Excessive subcooling
D. Cavitation
,Answer: B
Explanation: Compressors are designed to compress vapor, not liquid. Liquid
slugging can damage valves, pistons, and bearings.
7. Which safety device protects against excessive high-side pressure?
A. Low-pressure switch
B. Expansion valve
C. High-pressure cutout
D. Crankcase heater
Answer: C
Explanation: A high-pressure cutout automatically stops the compressor when
discharge pressure is too high.
8. In psychrometrics, the term “relative humidity” means:
A. Actual humidity in grains per pound of air
B. Ratio of actual water vapor to maximum possible at that temperature
C. Total enthalpy of air-water mixture
D. Dew point temperature
Answer: B
Explanation: Relative humidity is a percentage comparing current water vapor
content to the maximum possible at the same temperature.
9. The dew point temperature is:
A. The point where sensible cooling begins
B. The temperature at which air is fully saturated and condensation starts
C. Always lower than dry bulb temperature
D. The difference between wet bulb and dry bulb
Answer: B
Explanation: Dew point is when air cannot hold more moisture, and
condensation occurs.
, 10. A centrifugal chiller uses which principle for compression?
A. Reciprocating action
B. Screw rotation
C. Dynamic impeller acceleration
D. Scroll movement
Answer: C
Explanation: Centrifugal chillers accelerate refrigerant vapor with an impeller,
converting velocity energy into pressure.
11. What is the function of an economizer in a cooling system?
A. Increases compressor speed
B. Enhances subcooling to improve efficiency
C. Provides emergency shutoff
D. Reduces condenser water flow
Answer: B
Explanation: Economizers use flash gas to subcool liquid refrigerant,
improving efficiency.
12. Which law states that “pressure of a gas is directly proportional to
temperature when volume is constant”?
A. Boyle’s Law
B. Dalton’s Law
C. Charles’ Law
D. Gay-Lussac’s Law
Answer: D
Explanation: Gay-Lussac’s Law defines the pressure-temperature relationship
at constant volume.
13. A chiller operating at too low suction pressure may indicate:
A. Dirty condenser tubes
B. Insufficient refrigerant charge
