Which of the following is not a component of a reciprocating refrigeration compressor?

In a reciprocating refrigeration compressor, the primary components function together to compress the refrigerant gas and facilitate the refrigeration cycle. The compressor cylinder houses the piston, which moves up and down to compress the gas. The connecting rod links the piston to the crankshaft, enabling the reciprocating motion.

The impeller, however, is typically associated with centrifugal compressors, which use a different mechanism for gas compression. Unlike reciprocating compressors that rely on pistons and cylinders for direct gas compression, centrifugal compressors utilize rotating blades (impellers) to accelerate and compress the refrigerant gas. Thus, the impeller is not a component of a reciprocating refrigeration compressor. Understanding the specific roles of these components clarifies why the impeller is the correct answer in this context.