Reciprocating Compressor

Multistage Reciprocating Compressor

it is seen from this equation that as the pressure ratio increases the volumetric efficiency decreases. This is illustrated in the next Figure.

Effect of delivery pressure on the volumetric efficiency  

Effect of intercooling on the compression work

Example 6

In a single-acting, two-stage reciprocating air compressor 4.5 kg of air per minute are compressed from 1.013 bar and 15°C through a pressure ratio of 9 to 1. Both stages have the same pressure ratio, and the law of compression and expansion in both stages is pV1.3 = constant. If intercooling is complete, calculate the indicated power and the cylinder swept volumes required. Assume that the clearance volumes of both stages are 5% of their respective swept volumes and that the compressor runs at 300 rev/rnin.

Plan showing intercooling between compressor stages

T-s diagram showing intercooling and aftercooling

The ideal intermediate pressure

= 0