Which of the following is not considered a rotary refrigeration compressor design?

The answer identifies centrifugal compressors as not being a type of rotary refrigeration compressor design. In refrigeration systems, rotary compressors typically involve mechanisms where rotating parts generate compression within the system. These include designs that utilize moving elements like scrolls, vanes, and certain types of reciprocating mechanisms that act in a rotary fashion.

Centrifugal compressors, on the other hand, function based on a different principle. They utilize a rotating impeller to increase the velocity of the refrigerant, converting that velocity into pressure as the refrigerant moves through a diffuser. This design is characterized as a dynamic compression process rather than a rotary compression process seen in the other types mentioned.

Understanding this distinction helps clarify why centrifugal compressors are categorized separately from the various types of rotary compressors, which rely more on direct rotary movements of components to increase pressure and facilitate the refrigeration cycle.