Which refrigerant is used in smaller centrifugal compressors?

• A. R-12
• B. R-11
• C. R-22
• D. R-134a

Answer: (B)

Smaller centrifugal compressors are designed to run efficiently at high speeds and with compact hardware, so the refrigerant chosen needs thermodynamic properties that suit that setup. R-11 has characteristics that fit well with the high-speed, high-pressure ratios of small centrifugal machines, making it the traditional choice for those units. The other refrigerants listed are more commonly used in different compressor types or larger systems, or were developed to replace older CFCs in newer designs. Although R-11 is largely phased out today for environmental reasons, its historical use in smaller centrifugal compressors is why it’s the correct answer in this context.