Which type of compressor is considered a non-positive displacement compressor?

A centrifugal compressor is classified as a non-positive displacement compressor because it operates based on the principle of converting kinetic energy from the motion of the impeller into pressure energy. This type of compressor uses high-speed rotation to impart velocity to the refrigerant, which is then converted to pressure through diffusion as it moves through a diffuser.

In contrast, positive displacement compressors, such as reciprocating and scroll compressors, operate by trapping a fixed amount of refrigerant and then reducing the volume to increase pressure. Hermetic compressors can come in both positive and non-positive displacement variations, but they are typically distinguished by their sealed construction rather than their compression mechanism.

Thus, the primary function of the centrifugal compressor, utilizing continuous flow and kinetic energy to generate pressure, solidifies its classification as a non-positive displacement compressor.