Review Flashcards
What kind of metering devices are in refrigeration systems?
TXV
Automatic expansion valve
Capillary tubes
What are the three main functions of a TXV?
- prevent floodback to the compressor
- provide a constant amount of superheat
- keep entire evaporator full of refrigerant
If there is contamination from a compressor burnout, the refrigerant may…
not be reused
If the orifice of capillary tubes are too small, it will ______ the evaporator.
starve
Why is it necessary to have superheat in a refrigeration system?
to ensure all the refrigerant is in a vapor state
What are the four stages of the refrigeration system?
- compression
- condensation
- expansion
- evaporation
The heat energy that causes a state change at a constant pressure is called…
latent heat
True or False:
Condensing pressure is the pressure at which refrigerant changes state from a vapor to a liquid.
True
True or False:
Evaporating pressure is the pressure at which refrigerant changes state from a liquid to a vapor.
True
What is the function of the compressor?
to circulate refrigerant
What is the function of the discharge line?
convey the refrigerant from the compressor to the condenser
In what types of systems do we see receivers and why?
In TXV systems to store refrigerant and act as a surge tank
What does the liquid line do in a refrigerant system?
carries high pressure liquid to the metering device
Where do the high side and low side of a refrigeration system divide?
Metering device
Superheat on a system is divided into what two parts?
- evaporator superheat
- compressor superheat
Name four situations that can cause low evaporator loads.
- iced up/dirty coil
- evaporator fan motor not working
- defrost circuit malfunction causes icing
- end of refrigeration cycle
- low air flow across evaporator coil
- low refrigerant charge
What is the difference between flooding and migration?
For migration the unit is off, flooding the unit is running.
What are the reasons for slugging?
- bad TXV
- low load
- dirty evaporator
- overcharge
What does the evaporator act as?
A heat exchanger
True or False:
The suction line transports superheated vapor from the evaporator to the compressor.
True
True or False:
If a capillary tube system is overcharged, it will back up excess liquid in the condenser.
True
True or False:
If a capillary tube system is overcharged, it will cause high head pressure.
True
Where do we install a filter/dryer in a capillary tube system and why?
Before the capillary tubes to catch foreign objects
What is the color code for R-11, R-12, and R-134a?
R-11 is orange
R-12 is yellow
R-134a is blue
