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4 TRG-TRC016-EN
notes
period one
Types of Water Chillers
The type of compressor used generally has the greatest impact on the efficiency
and reliability of a vapor-compression water chiller. The improvement of
compressor designs and the development of new compressor technologies
have led to more-efficient and -reliable water chillers.
The reciprocating compressor was the workhorse of the small chiller market
for many years. It was typically available in capacities up to 100 tons [350 kW].
Multiple compressors were often installed in a single chiller to provide chiller
capacities of up to 200 tons [700 kW].
Scroll compressors have emerged as a popular alternative to reciprocating
compressors, and are generally available in hermetic configurations in
capacities up to 15 tons [53 kW] for use in water chillers. As with reciprocating
compressors, multiple scroll compressors are often used in a single chiller to
meet larger capacities. In general, scroll compressors are 10 to 15 percent more
efficient than reciprocating compressors and have proven to be very reliable,
primarily because they have approximately 60 percent fewer moving parts than
reciprocating compressors. Reciprocating and scroll compressors are typically
used in smaller water chillers, those less than 200 tons [700 kW].
Helical-rotary (or screw) compressors have been used for many years in
air compression and low-temperature-refrigeration applications. They are now
widely used in medium-sized water chillers, 50 to 500 tons [175 to 1,750 kW].
Like the scroll compressor, helical-rotary compressors have a reliability
advantage due to fewer moving parts, as well as better efficiency than
reciprocating compressors.
Centrifugal compressors have long been used in larger water chillers.
High efficiency, superior reliability, reduced sound levels, and relatively low
cost have contributed to the popularity of the centrifugal chiller. Centrifugal
compressors are generally available in prefabricated chillers from 100 to
3,000 tons [350 to 10,500 kW], and up to 8,500 tons [30,000 kW] as built-up
machines.
centrifugal
scroll
reciprocating
helical-rotary
Compressor Types
Figure 6