A chiller is a machine that removes heat from a liquid via a
vapor-compression or absorption refrigeration cycle. The liquid can
then be circulated through a heat exchanger to cool equipment, or
another process stream(such as air or process water). As a necessary
by product, refrigeration create waste heat that must be exhausted
to ambience, or for grater efficiency, recovered for heating purpose.

Chiller water is used to cool and dehumidify air in mid to large size
commercial, industrial, and institutional facilities. Water chillers can
be water-cooled, air-cooled, or evaporative cooled. Water cooled
systems can provide efficiency and environmental impact
advantage over air-cooled systems.