Glossary
chilled-water system Uses water as the cooling media. The refrigerant inside the evaporator absorbs heat from the water, and this water is pumped to coils in order to absorb heat from the air used for space conditioning.
coefficient of performance (COP) A dimensionless ratio used to express the efficiency of a refrigeration machine. A higher COP designates a higher efficiency. For an electric chiller, it is defined as evaporator cooling capacity divided by the electrical energy input. For an absorption water chiller, it is defined as evaporator cooling capacity divided by the heat energy required by the generator, excluding the electrical energy needed to operate the pumps, purge, and controls.
compressor A mechanical device used in the vapor-compression refrigeration cycle to increase the pressure and temperature of the refrigerant vapor.
condenser A component of the refrigeration cycle in which refrigerant vapor is converted to liquid as it rejects heat to air, water, or some other fluid.
cooling tower A device used to reject the heat from a water-cooled condenser by spraying the condensing water over the fill while drawing outdoor air upward through the fill.
decoupled system See primary-secondary system.
deficit flow A condition in a primary-secondary chilled-water system in which the production loop provides less flow than is required by the distribution loop. To make up for this deficit, water travels from the return side of the distribution loop, through the bypass pipe, and mixes with the water supplied by the production loop.
direct-firedA type of absorption chiller that uses the combustion of a fossil fuel (such as natural gas or oil) directly to provide heat to the high-temperature generator.
double-effectA type of absorption chiller that uses two generators, a high-temperature generator and a low-temperature generator.
evaporator A component of the refrigeration cycle where cool, liquid refrigerant absorbs heat from air, water, or some other fluid, causing the refrigerant to boil.
excess flow A condition in a primary-secondary chilled-water system in which the production loop is providing more flow than is required by the distribution loop. This excess water travels from the supply side of the production loop, through the bypass pipe, and mixes with the water returning from the distribution loop.
expansion device A component of the refrigeration cycle used to reduce the pressure and temperature of the refrigerant to the evaporator conditions.
