• The volumetric efficiency represents the efficiency of a compressor cylinder to compress gas.
• It may be defined as the ratio of the volume of gas actually delivered to the piston displacement, corrected to suction temperature and pressure.

where,

P_H = Higher  Pressure

P_L = Lower Pressure

C = Clearance Ratio

n = Polytropic index of expansion

η_{v  =} volumetric efficiency

Hence, the correct option is (C).