Automatic Expansion Valve
Metering device that maintains a constant evaporator pressure
Bubble Point
for blended refrigerants, the temperature used to calculate condenser subcooling
Bulb Pressure
Pressure that facilitates the opening of the thermostatic expansion valve
Capillary Tube
a fixed bore metering device
Compression
the portion of the compression process in which the refrigerant is compressed
Compressor
the component of an air conditioning system that pumps refrigerant through the system by increasing the pressure of the vapor refrigerant
Condenser
a heat transfer surface in an air conditioning system that rejects heat
Condenser Saturation Temperature
the temperature at which system refrigerant will condense in the condenser; this temperature corresponds to the high side pressure in the system on a pressure/temperature chart
Condensing Medium
The medium, usually air or water, that absorbs the heat that is rejected by the system condenser.
Critically charged system
a system that requires an exact quantity of refrigerant; all of the refrigerant is moving through the system at all times.
Cylinder
the component part of a reciprocating compressor that houses the piston
Dehumidifying
the process of removing humidity from the air
Desuperheating
the process by which the discharge refrigerant from the compressor is cooled down to the condenser saturation temperature
Dew Point
the temperature at which air reaches 100% humidity; for blended refrigerants, the temperature used to calculate evaporator superheat
Discharge
the portion of the compression process when the refrigerant is discharged from the compressor
Discharge line
the refrigerant line that carries the discharge refrigerant from the compressor to the condenser
Discharge valve
the component part of a reciprocating compressor that opens to discharge refrigerant from the compressor into the discharge line
Dry type evaporator
an evaporator that is designed to have all of the refrigerant boil off into a vapor before leaving the coil
Evaporator
the component part of an air conditioning system that is responsible for absorbing heat from the space to be cooled
Evaporator pressure
the pressure that corresponds to the temperature at which refrigerant vaporizes in the evaporator on a pressure/temperature chart
Externally equalized tev
a thermostatic expansion valve that measures the evaporator pressure at the outlet of the coil
Fixed bore metering device
a metering device that does not open or close in response to changes in the load on the system; examples are the capillary tube and the piston
Flash gas
the process by which some of the liquid refrigerant instantly vaporizes upon entering the evaporator
Internally equalized tev
a thermostatic expansion valve that measures the evaporator pressure at the inlet of the coil
Liquid line
the refrigerant carrying line that connects the condenser to the metering device
Metering device
the component of an air conditioning system that controls the flow of refrigerant to the evaporator
Outside ambient temperature
the temperature of the air that surrounds the outdoor coil of an air conditioning system
Piston
the component part of the reciprocating compressor that moves back and forth within the cylinder to compress or expand the refrigerant in the cylinder
Pressure temperature chart
shows the relationship that exists between the temperatures and pressures of saturated refrigerants
Psig
pounds per square inch gauge; pressure readings taken from a gauge manifold
Reexpansion
In a reciprocating compressor, the process by which the refrigerant trapped in the cylinder at the end of a cycle is expanded to reduce the pressure in the cylinder
Repeating cycle
a process that can repeat itself indefinitely without depleting resources
Return air
air that is brought from the conditioned space to the evaporator
Saturated
Refrigerant that is a mixture of liquid and vapor; saturated refrigerants follow a pressure/temperature relationship
Spring pressure
one of the closing pressures on the thermostatic expansion valve; also the opening pressure on the automatic expansion valve
Subcooling
the process by which the refrigerant in the condenser is cooled below the condenser saturation temperature
Suction
in a reciprocating compressor, the process by which refrigerant in the suction line is pulled into the compression chamber prior to being compressed
Suction line
the refrigerant-carrying line that connects the outlet of the evaporator to the compressor
Suction pressure
the pressure of the low side of the system; also called low-side or back pressure
Suction valve
the component part of a reciprocating compressor that opens to pull refrigerant from the evaporator into the compressor for compression
Superheat
the process by which vapor refrigerant is heated above its evaporator saturation temperature
Supply air
the air that is returned to the conditioned space after it has passed through the evaporator
Thermal bulb
TEV component that senses the temperature at the outlet of the evaporator and converts this temperature to the valve's opening pressure
Thermostatic Expansion Valve
Metering device designed to maintain a constant evaporator superheat
Total system charge
the amount of refrigerant a system contains
Transmission line
the small diameter tube that connects the thermal bulb to the body of a thermostatic expansion valve
Discharge pressure
the pressure of the refrigerant in the high-pressure side of the air conditioning system; also referred to as the high-side or head pressure