Liquid chillers are refrigeration systems that chill liquids such as
water, oil, brine, alcohol, coolants, chemicals and beverage or food
ingredients for industrial applications. Their design and construction
are very similar to air conditioners, and they range vastly in size.
They may be fabricated as small, localized units for small applications
or as large central chiller systems combining many heat exchangers and
external cooling towers that span an entire facility.
Industrial liquid chillers are built for industrial cooling, where they cool products, mechanisms and factory machinery in processes such as plastic injection molding, blow molding, metalworking, welding, die casting, chemical and pharmaceutical processing, food and beverage processing, lab equipment and lasers. Others are built for gas cooling and air conditioning for commercial and industrial facilities. Types of liquid chillers include absorption chillers, air cooled chillers, water cooled chillers, evaporation cooled chillers, recirculating chillers, centrifugal chillers and screw chillers.
Liquid chillers have four main stages: the evaporator, the vapor compressor, the condenser and the expansion valve. These stages are designed to re-circulate the refrigerant through gas and liquid stages. Initially, a cold refrigerant in gas form passes over heat exchanger tubes containing the hot liquid which needs to be chilled. The refrigerant absorbs the heat lost by the liquid, cause some of the liquid to evaporate. A gas compressor then compresses the vaporized refrigerant into a high pressure, high temperature gas. The gas then moves into the condenser coil over which ambient air blows. The air, moved by one or more fans, removes heat from the gas, which causes it to condense into a high pressure, moderate temperature liquid. The liquid then passes through an expansion valve where a large pressure drop occurs, so that some of the liquid evaporates into a very cold mist and the refrigerant becomes cold. Finally, the cold refrigerant returns to the heat exchanger, and the whole process begins again. Many types of toxic and non-toxic refrigerants may be used in chillers; toxic refrigerants include chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs) and halomethanes such as R-22; these substances have very low boiling points, enabling them to change their physical state from liquid to vapor easily. Non-toxic refrigerants include water, brine, liquefied propane gas and CO2.