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TRG-TRC010-EN 19
period two
Refrigeration Cycle
notes
Refrigerants
When selecting which refrigerant to use in a centrifugal water chiller, the
manufacturer considers efficiency, operating pressures, compatibility with
materials, heat transfer properties, stability, toxicity, flammability, cost,
availability, and environmental impact.
Refrigerants commonly used in centrifugal chillers can be classified as low,
medium, or high pressure based on the normal operating pressures in the
refrigeration cycle.
Chillers using a high-pressure refrigerant like HCFC-22, or a medium-pressure
refrigerant like HFC-134a, operate at pressures that are well above atmospheric
pressure. As we are about to see, some sections of chillers that use a low-
pressure refrigerant such as HCFC-123 operate at below-atmospheric pressure.
pressure
pressure
temperature
temperature
HCFC-22
HCFC-22
HCFC-123
HCFC-123
atmospheric
atmospheric
pressure
pressure
Refrigerant Operating Pressures
HFC-134a
HFC-134a
Figure 27
trgtrc010_book.book Page 19 Wednesday, September 1, 1999 10:39 AM