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Avoiding Centrifugal Chiller Surge
ASHRAE Journal, November 2018
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Centrifugal chiller surge puts strain on many parts of the compressor (e.g., seal, bearing, blades). Severe damage can occur if the compressor is unable to handle it. Eventually, if no actions are taken, surge will result in chiller damage. Most designers and operators that have worked around centrifugal chillers have experienced the violent nature of a surge condition in the compressor. This month, I provide some background on this operating condition and discuss what causes surge and ways to avoid it in your chiller plant design and operation.
Chiller Refrigeration Basics
It is important to have a basic understanding of what is happening inside a centrifugal chiller. A centrifugal chiller uses the vapor compression cycle to chill water and reject the heat through a condenser. The condenser could be air-cooled or water-cooled. Figure 1 shows a basic refrigeration cycle consisting of an evaporator, compressor, condenser and expansion device. Normal refrigerant flow through the system should be from compressor to condenser to evaporator and back to the compressor.