What is forced up and down in the cylinder of a reciprocating compressor?

In a reciprocating compressor, the piston is the key component that moves up and down within the cylinder. This motion is crucial for the compression process. When the piston moves down, it creates a vacuum that allows gas to enter the cylinder through the intake valve. As the piston moves back up, it compresses the gas, increasing its pressure, before it is expelled through the discharge valve.

The design of the cylinder and piston ensures efficient gas compression and can handle varying pressures and volumes of gas. This principle of reciprocating motion is what differentiates reciprocating compressors from other types, such as rotary compressors, where a rotor might be involved. The functionality of the piston is vital for ensuring that the compressor operates effectively, making it the correct choice in this scenario. Other components mentioned, such as a rotor or fan, do not perform the same function in the context of a reciprocating compressor.