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98 Chiller System Design and Control SYS-APM001-EN
Glossary
COP. Coefficient of Performance; cooling effect divided by heat input
(dimensionless); the reciprocal of efficiency.
direct digital control. Programming used by building control systems to
control variable outputs, such as valves or actuators. In the HVAC industry,
DDC means direct digital control by a microprocessor controller with no
intermediate device.
evaporator. The region in the chiller where the system chilled water is
continuously cooled down by flashing the refrigerant to vapor in a deep
vacuum as it picks up heat from the returning system water.
fouling. Deposits of foreign material in the water side of tubing in
refrigeration condensers or chillers that affect the transfer of heat.
heat exchanger. A device used to transfer heat between two physically
separated fluids.
heat transfer. The movement of heat from one body or substance to another.
The three methods of heat transfer are conduction, convection, and radiation.
load. Any one of several output devices that are to be controlled by a
building management panel.
mechanical-compression refrigeration cycle. The electrically driven chiller
makes use of an electric motor, driving a compressor to produce chilled
water for cooling. It does this via a mechanical process that uses a refrigerant
for a working fluid. Inside the vessel are pressure and temperature
differentials, where heat is absorbed at a low temperature and then rejected
at a higher temperature.
psychrometric chart. A chart that shows the relationship between the
temperature, pressure, and moisture content of the air.
psychrometric measurement. The measurement of temperature, pressure,
and humidity of air using a psychrometric chart.
pumps (system)
chilled water. Circulates the chilled water through the evaporator
section of the chiller and then through the building coils.
cooling water. Circulates the cooling water from the source through
the chiller, condenser, and back to the source.
shell-and-tube. A designation for a type of heat exchangers consisting of a
tube bundle within a shell or casing. Often used in chiller condensers and
evaporators.
shell-and-tube flooded evaporators. Evaporators that use water flow through
tubes built into a cylindrical evaporator with refrigerant on the outside of the
tubes.