Chillers Industry Information
Liquid chillers are refrigeration systems that chill liquids such as
water, oil, brine, alcohol, chemicals and beverage or food ingredients
for industrial applications. With design and construction very similar
to that of air conditioners, liquid chillers range vastly in size and
design and may be fabricated as small, localized units for small
applications or as large central chillers combining many heat
exchangers and external cooling towers which span an entire facility.
These
industrial chillers
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, gas cooling and lasers. Chocolate, for
example, may be run through a liquid cooler to in order to regulate the
chocolate`s temperature for the next stage of processing, or to keep it
from burning.
Water chillers continually cool water which is used in turn to cool laser equipment, while
portable chillers and
air cooled chillers are used in a variety of facility
cooling systems
depending on specific design requirements. Liquid coolers are typically
recirculating chiller systems which recycle the same refrigerant liquid
within a closed loop.
Liquid chillers have
four main stages: the evaporator, the vapor compressor, the condenser
and the expansion valve. These stages are designed to recirculate 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, condensing some of the vapor into a liquid. A vapor
compressor compresses the liquid-gas 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,
warm temperature liquid. The liquid passes through the expansion valve
where a large pressure drop occurs, turning the liquid into a very cold
mist. The mist 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.
Four
styles of vapor compressors are used: reciprocating, or piston, style
compressors; scroll compressors; screw driven compressors and
centrifugal compressors. A scroll style compressor uses two interleaved
scrolls, one which is stationary and one which rotates about the other
to create a pump. A piston style, or reciprocating compressor rotates a
shaft that is curved like a crankshaft, creating pressure in the piston
cylinder. Screw compressors contain a single rotating screw element
which creates a vacuum as it rotates. Centrifugal compressors use
inertia to separate vapor molecules from the air. Scroll compressors
are usually more efficient than piston compressors, but both are very
reliable and widely used in the refrigeration industry. Condensers come
in three types. In air cooled condensers, air circulates around tubes
containing the refrigerant, contributing to the condensation of the
refrigerant. These condensers are used in instances where water is
unavailable. Water cooled condensers, also called "shell" or "tube"
condensers, utilize water to condense the refrigerant. Water circulates
through the tubes around which the refrigerant is introduced, causing
condensation of the refrigerant on the outside of the tubes. In
evaporative cooled condensers, water is sprayed onto tubes containing
the refrigerant. The evaporation of the water causes the condensation
of the refrigerant within the tube. Large liquid chillers used for
high-volume industrial applications often include a cooling tower at
this stage, allowing condensed liquid refrigerant to cool in a tank by
various means of air and water cooling.
Halomethanes
R-12 and R-22 were the most commonly used refrigerants up until the
1980`s, and other similarly toxic refrigerants such as Freon, CFCs and
HCFCs continue to be used today. As concern has risen in manufacturing
and legislative sectors over global warming, ozone-depleting substances
such as Freon, halomethanes and CFCs have been banned or discouraged.
Disposal of toxic substances such as Freon is hazardous to the
environment, and CFCs used in refrigeration have contributed to
significant depletion of the Earth`s ozone layer. As the refrigeration
and liquid chiller industry advances, more liquid chiller manufacturers
are using non-toxic refrigerants such as ammonia, brine and pure water.
Centrifugal vapor compressor technology and other types of high
efficiency vaporizing coolant systems achieve more efficient cooling
physically, without as great a need for low-boiling chemicals.
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Liquid Chillers and Liquid Chiller Manufacturers Image Provided by Tempest
Inc.
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