🔍 Key Concepts

• Centrifugal compressor capacity control methods in HVAC/refrigeration systems • Difference between bypassing gas, throttling/controlling inlet flow, and changing compressor speed • How each method affects mass flow rate and pressure ratio

💭 Think About

• For each option, ask yourself: does this method actually change how much refrigerant the compressor effectively handles, or does it just redirect it? • Think about which method(s) are commonly used in large centrifugal chillers to match cooling load while maintaining stable compressor operation. • Consider how changing inlet guide vanes versus changing speed impacts compressor efficiency and surge margin.

✅ Before You Answer

• Verify which methods are recognized as practical, standard capacity control techniques for centrifugal refrigeration compressors. • Check whether hot gas bypass alone is typically described as a "capacity control" method for centrifugal machines or more for other compressor types. • Confirm whether more than one of the listed methods can legitimately control capacity, and whether the exam is likely focusing on a single standard method or all applicable ones.