Explanation:

The clearance volume in a reciprocating compressor is the volume remaining in the cylinder at the end of the compression stroke when the piston is at top dead center. This volume is necessary in order to accommodate the valves in the cylinder head of the compressor.

Accommodate valves in the cylinder head:
The clearance volume is required to provide space for the valves in the cylinder head of the compressor. In a reciprocating compressor, there are typically two valves - the suction valve and the discharge valve. These valves allow the flow of air into and out of the cylinder. The clearance volume ensures that there is enough space for these valves to open and close properly without interfering with the movement of the piston.

Importance of valves:
The valves play a crucial role in the operation of a reciprocating compressor. The suction valve opens during the suction stroke, allowing the air to enter the cylinder. The discharge valve opens during the compression stroke, allowing the compressed air to be delivered. These valves ensure the proper flow of air and help in maintaining the desired pressure levels.

Volumetric efficiency:
The clearance volume does not directly contribute to the volumetric efficiency of the compressor. Volumetric efficiency is a measure of how well a compressor can deliver the desired volume of air. It is determined by factors such as the compression ratio, clearance volume, and valve design. However, the clearance volume does indirectly affect the volumetric efficiency by influencing the flow of air into and out of the cylinder through the valves.

Work input per kg of air delivered:
The clearance volume does not directly affect the work input per kg of air delivered. The work input is primarily determined by the compression ratio, which is the ratio of the volume of air at the beginning of compression to the volume of air at the end of compression. The clearance volume does not have a direct impact on this ratio.

Conclusion:
In conclusion, the clearance volume in a reciprocating compressor is provided to accommodate the valves in the cylinder head. It ensures that there is enough space for the valves to open and close properly, allowing for the proper flow of air into and out of the cylinder. The clearance volume does not directly affect the volumetric efficiency or the work input per kg of air delivered.