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TRG-TRC010-EN 55
adjustable-frequency drive (AFD) A device used to vary the capacity of a
centrifugal compressor by varying the speed of the motor that rotates the
impeller(s).
air-side economizer A method of free cooling that involves using cooler
outdoor air for cooling instead of recirculating warmer indoor air.
ARI Air Conditioning & Refrigeration Institute
ARI Standard 550/590 A publication titled
“Standard for Water Chilling
Packages Using the Vapor-Compression Cycle,”
used to promote consistent
rating and testing methods for all types and sizes of water chillers. It covers
factory-designed, prefabricated water chillers, both air-cooled and water-
cooled, using the vapor-compression refrigeration cycle.
ASHRAE American Society of Heating, Refrigerating and Air Conditioning
Engineers
ASHRAE Guideline 3 A publication titled
“Reducing Emission of Halogenated
Refrigerants in Refrigeration and Air Conditioning Equipment and Systems,”
that includes a recommended list of data points to be logged daily for each
water chiller.
compressor The mechanical device used by the chiller to increase the
pressure and temperature of the refrigerant vapor.
condenser The region of the chiller where refrigerant vapor is converted to
liquid as it rejects heat to water or air.
control panel The microprocessor-based panel that monitors the chiller’s
operation, protects it from damage, provides the operator with data and
diagnostic messages, and permits interfacing with a building automation
system.
diffuser passages Passages inside the centrifugal compressor that start out
small and become larger as the refrigerant travels through them. As the size of
the diffuser passages increases, the velocity, and therefore the kinetic energy, of
the refrigerant decreases. This kinetic energy is converted to static energy or
static pressure.
direct-drive motor A type of motor that is connected directly to the
compressor shaft, in which the impeller rotates at the same speed as the motor.
direct expansion (DX) shell-and-tube evaporator A type of evaporator where
refrigerant flows through the tubes and water fills the surrounding shell.
dynamic compression A method of compression that involves converting
energy from one form to another to increase the pressure and temperature of
the refrigerant vapor.
Glossary
trgtrc010_book.book Page 55 Wednesday, September 1, 1999 10:42 AM