Glossary

absorbent A substance used to absorb refrigerant and transport it from the low-pressure to the high-pressure side of the absorption refrigeration cycle. In absorption water chillers, the absorbent is commonly lithium bromide.

absorber A component of the absorption refrigeration system where refrigerant vapor is absorbed by the absorbent solution and rejects heat to cooling water.

adjustable-frequency drive (AFD) A device used to control the capacity of a pump by varying the speed of the pump motor.

ARI Air Conditioning & Refrigeration Institute.

ARI Standard 560 A publication, titled “Absorption Water Chilling and Water Heating Packages,” used to promote consistent rating methods for many types and sizes of absorption water chillers, using water as the refrigerant and lithium bromide as the absorbent. It covers single-effect chillers operating on steam or a hot fluid; indirect-fireddouble-effect chillers operating on steam or a hot fluid; and direct-fireddouble-effect chillers operating on natural gas, oil, or liquid petroleum (LP).

ASHRAE American Society of Heating, Refrigerating and Air-Conditioning Engineers.

ASHRAE Standard 15 A publication, titled “Safety Code for Mechanical Refrigeration,” that specifies safe design, construction, installation, and operation of refrigerating systems.

auxiliary heating bundle A separate heat exchanger added to a direct-fired absorption chiller to allow it to provide simultaneous cooling and heating.

chilled water The cold water produced by the chiller (flowing through the tubes in the evaporator) and pumped to the air-handler coils throughout the building.

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. For an absorption water chiller, it is defined as the ratio of evaporator cooling capacity divided by the heat energy required by the generator, excluding the electrical energy needed to operate the pumps, purge, and controls. A higher COP designates a higher efficiency.

compressor A mechanical device used in the vapor-compression refrigeration cycle to increase the pressure and temperature of the refrigerant vapor.

concentrated absorbent solution A mixture of refrigerant and absorbent that has a relatively low refrigerant content and high absorbent content.