Which statement about centrifugal compressors is true?

• A. They operate at much higher temperatures.
• B. They are not a positive displacement type.
• C. They require no lubrication.
• D. They use pistons for compression.

Answer: (B)

Centrifugal compressors are dynamic (turbomachinery) compressors. They raise gas pressure by spinning an impeller to fling the gas outward, then using a diffuser to slow it down and convert the resulting velocity into pressure. Because there’s no trapped chamber where a fixed volume is repeatedly compressed, they are not positive-displacement devices. That’s the key idea: compression comes from imparting kinetic energy and then converting that energy to pressure, not from squeezing a fixed volume.

This is why the statement that they are not a positive-displacement type is the best description. Other choices aren’t defining traits: they don’t inherently run at much higher temperatures by design, they do rely on lubrication for bearings and seals, and they don’t use pistons for compression.