Which of the following compressors does not require inlet or discharge valves?

The sliding vane compressor does not require inlet or discharge valves due to its design and operational principles. This type of compressor utilizes a series of sliding vanes that move within a cylindrical housing, creating variable volume pockets that trap and compress air or other gases as they move towards the discharge end.

As the vanes slide in and out of their slots during rotation, they continuously seal the compression chambers without the need for separate valve mechanisms to control airflow. This design allows for a smooth and efficient compression process, eliminating the potential for valve-related issues such as wear or malfunction.

In contrast, reciprocating compressors use piston mechanisms that rely on inlet and discharge valves to function by cycling the pistons in and out of the cylinder. Similarly, screw compressors utilize rotors that require valves to manage the intake and expulsion of air. Centrifugal compressors, while not employing traditional valves, still use diffusers and guide vanes to manage airflow but do not match the unique operational characteristics of the sliding vane type.