1. Q: What is the primary function of a refrigeration system? ANSWER To
remove heat from a space or substance and transfer it to another location,
maintaining a lower temperature than the surroundings.
2. Q: What are the four main components of a basic refrigeration cycle?
ANSWER Compressor, condenser, expansion device (metering device), and
evaporator.
3. Q: What is the purpose of the compressor in a refrigeration system?
ANSWER To increase the pressure and temperature of refrigerant vapor and
circulate refrigerant through the system.
4. Q: What occurs in the condenser of a refrigeration system? ANSWER
The high-pressure, high-temperature refrigerant vapor releases heat and
condenses into a liquid.
5. Q: What is the function of the expansion device? ANSWER To reduce the
pressure and temperature of the liquid refrigerant before it enters the evaporator.
6. Q: What happens in the evaporator? ANSWER Low-pressure liquid
refrigerant absorbs heat from the surrounding air or substance and evaporates
into a vapor.
7. Q: What is superheat? ANSWER The temperature of refrigerant vapor
above its saturation temperature at a given pressure.
8. Q: What is subcooling? ANSWER The temperature of liquid refrigerant
below its saturation temperature at a given pressure.
9. Q: What is the saturation temperature? ANSWER The temperature at
which a refrigerant changes state (boils or condenses) at a given pressure.
,10. Q: What is the pressure-temperature relationship in refrigerants?
ANSWER As pressure increases, the saturation temperature increases; as
pressure decreases, the saturation temperature decreases.
11. Q: What is latent heat? ANSWER The heat absorbed or released during a
change of state without a change in temperature.
12. Q: What is sensible heat? ANSWER Heat that causes a change in
temperature without a change in state.
13. Q: What is a ton of refrigeration? ANSWER The amount of heat
required to melt one ton (2,000 pounds) of ice in 24 hours, equal to 12,000
BTU/hr.
14. Q: What is the purpose of refrigerant oil in a compressor? ANSWER
To lubricate moving parts, seal clearances, cool components, and reduce noise.
15. Q: What is the difference between high-pressure and low-pressure sides
of a refrigeration system? ANSWER The high-pressure side extends from the
compressor discharge to the expansion device; the low-pressure side extends
from the expansion device through the evaporator to the compressor inlet.
16. Q: What is a hermetic compressor? ANSWER A compressor with the
motor and compressor sealed together in a welded shell.
17. Q: What is a semi-hermetic compressor? ANSWER A compressor with
the motor and compressor in a bolted housing that can be opened for service.
18. Q: What is an open-drive compressor? ANSWER A compressor with an
external motor connected by a belt or direct coupling.
19. Q: What is a reciprocating compressor? ANSWER A compressor that
uses pistons moving in cylinders to compress refrigerant vapor.
20. Q: What is a scroll compressor? ANSWER A compressor using two
spiral-shaped scrolls, one stationary and one orbiting, to compress refrigerant.
21. Q: What is a rotary compressor? ANSWER A compressor using rotating
vanes or a rolling piston to compress refrigerant.
22. Q: What is a screw compressor? ANSWER A compressor using
intermeshing helical rotors to compress refrigerant, typically used in large
systems.
23. Q: What is a centrifugal compressor? ANSWER A compressor that uses
a rotating impeller to increase refrigerant velocity and convert it to pressure.
, 24. Q: What is the purpose of a crankcase heater? ANSWER To prevent
refrigerant from condensing in the compressor crankcase during off cycles,
which could cause oil dilution and compressor damage upon startup.
25. Q: What is refrigerant migration? ANSWER The movement of
refrigerant from warmer to cooler parts of the system during off cycles.
26. Q: What is an accumulator? ANSWER A device installed in the suction
line to prevent liquid refrigerant from entering the compressor.
27. Q: What is a receiver? ANSWER A storage tank for liquid refrigerant on
the high-pressure side of the system, typically after the condenser.
28. Q: What is a thermostatic expansion valve (TXV)? ANSWER A
metering device that controls refrigerant flow based on superheat at the
evaporator outlet.
29. Q: What is a capillary tube? ANSWER A fixed-orifice metering device
consisting of a small-diameter tube that restricts refrigerant flow.
30. Q: What is an electronic expansion valve (EEV)? ANSWER A metering
device controlled by electronic signals from system sensors for precise
refrigerant flow control.
31. Q: What is a sight glass used for? ANSWER To visually check the
condition of refrigerant in the liquid line, indicating proper charge and moisture
content.
32. Q: What do bubbles in a sight glass indicate? ANSWER Typically
indicates low refrigerant charge, restriction in the liquid line, or excessive
pressure drop.
33. Q: What is a filter-drier? ANSWER A device that removes moisture,
acid, and contaminants from refrigerant.
34. Q: When should a filter-drier be replaced? ANSWER After system
contamination, compressor burnout, excessive pressure drop, or as
recommended by manufacturer (typically during major service).
35. Q: What is a suction line filter-drier used for? ANSWER To remove
contaminants after a compressor burnout or system contamination, installed
temporarily in the suction line.
36. Q: What is the purpose of a service valve? ANSWER To allow
connection of gauges and equipment for service, charging, and evacuation
procedures.
remove heat from a space or substance and transfer it to another location,
maintaining a lower temperature than the surroundings.
2. Q: What are the four main components of a basic refrigeration cycle?
ANSWER Compressor, condenser, expansion device (metering device), and
evaporator.
3. Q: What is the purpose of the compressor in a refrigeration system?
ANSWER To increase the pressure and temperature of refrigerant vapor and
circulate refrigerant through the system.
4. Q: What occurs in the condenser of a refrigeration system? ANSWER
The high-pressure, high-temperature refrigerant vapor releases heat and
condenses into a liquid.
5. Q: What is the function of the expansion device? ANSWER To reduce the
pressure and temperature of the liquid refrigerant before it enters the evaporator.
6. Q: What happens in the evaporator? ANSWER Low-pressure liquid
refrigerant absorbs heat from the surrounding air or substance and evaporates
into a vapor.
7. Q: What is superheat? ANSWER The temperature of refrigerant vapor
above its saturation temperature at a given pressure.
8. Q: What is subcooling? ANSWER The temperature of liquid refrigerant
below its saturation temperature at a given pressure.
9. Q: What is the saturation temperature? ANSWER The temperature at
which a refrigerant changes state (boils or condenses) at a given pressure.
,10. Q: What is the pressure-temperature relationship in refrigerants?
ANSWER As pressure increases, the saturation temperature increases; as
pressure decreases, the saturation temperature decreases.
11. Q: What is latent heat? ANSWER The heat absorbed or released during a
change of state without a change in temperature.
12. Q: What is sensible heat? ANSWER Heat that causes a change in
temperature without a change in state.
13. Q: What is a ton of refrigeration? ANSWER The amount of heat
required to melt one ton (2,000 pounds) of ice in 24 hours, equal to 12,000
BTU/hr.
14. Q: What is the purpose of refrigerant oil in a compressor? ANSWER
To lubricate moving parts, seal clearances, cool components, and reduce noise.
15. Q: What is the difference between high-pressure and low-pressure sides
of a refrigeration system? ANSWER The high-pressure side extends from the
compressor discharge to the expansion device; the low-pressure side extends
from the expansion device through the evaporator to the compressor inlet.
16. Q: What is a hermetic compressor? ANSWER A compressor with the
motor and compressor sealed together in a welded shell.
17. Q: What is a semi-hermetic compressor? ANSWER A compressor with
the motor and compressor in a bolted housing that can be opened for service.
18. Q: What is an open-drive compressor? ANSWER A compressor with an
external motor connected by a belt or direct coupling.
19. Q: What is a reciprocating compressor? ANSWER A compressor that
uses pistons moving in cylinders to compress refrigerant vapor.
20. Q: What is a scroll compressor? ANSWER A compressor using two
spiral-shaped scrolls, one stationary and one orbiting, to compress refrigerant.
21. Q: What is a rotary compressor? ANSWER A compressor using rotating
vanes or a rolling piston to compress refrigerant.
22. Q: What is a screw compressor? ANSWER A compressor using
intermeshing helical rotors to compress refrigerant, typically used in large
systems.
23. Q: What is a centrifugal compressor? ANSWER A compressor that uses
a rotating impeller to increase refrigerant velocity and convert it to pressure.
, 24. Q: What is the purpose of a crankcase heater? ANSWER To prevent
refrigerant from condensing in the compressor crankcase during off cycles,
which could cause oil dilution and compressor damage upon startup.
25. Q: What is refrigerant migration? ANSWER The movement of
refrigerant from warmer to cooler parts of the system during off cycles.
26. Q: What is an accumulator? ANSWER A device installed in the suction
line to prevent liquid refrigerant from entering the compressor.
27. Q: What is a receiver? ANSWER A storage tank for liquid refrigerant on
the high-pressure side of the system, typically after the condenser.
28. Q: What is a thermostatic expansion valve (TXV)? ANSWER A
metering device that controls refrigerant flow based on superheat at the
evaporator outlet.
29. Q: What is a capillary tube? ANSWER A fixed-orifice metering device
consisting of a small-diameter tube that restricts refrigerant flow.
30. Q: What is an electronic expansion valve (EEV)? ANSWER A metering
device controlled by electronic signals from system sensors for precise
refrigerant flow control.
31. Q: What is a sight glass used for? ANSWER To visually check the
condition of refrigerant in the liquid line, indicating proper charge and moisture
content.
32. Q: What do bubbles in a sight glass indicate? ANSWER Typically
indicates low refrigerant charge, restriction in the liquid line, or excessive
pressure drop.
33. Q: What is a filter-drier? ANSWER A device that removes moisture,
acid, and contaminants from refrigerant.
34. Q: When should a filter-drier be replaced? ANSWER After system
contamination, compressor burnout, excessive pressure drop, or as
recommended by manufacturer (typically during major service).
35. Q: What is a suction line filter-drier used for? ANSWER To remove
contaminants after a compressor burnout or system contamination, installed
temporarily in the suction line.
36. Q: What is the purpose of a service valve? ANSWER To allow
connection of gauges and equipment for service, charging, and evacuation
procedures.
