DieselShip's Online Content Library

Q8. A single acting, two stage reciprocating air compressors, takes in air at a pressure and temperature of 0.95 bar and 15℃ respectively and delivers it at 30 bars. The low-pressure cylinder has a bore of 300 mm and a stroke of 450 mm with a volumetric efficiency of 82 %.

The air enters the second stage at a pressure and temperature of 6 bar and 25℃ respectively.

The compressor speed is 200 rev/min.

The index of compression and expansion in both stages is 1.3.

(a) Sketch the process on a Pressure-Volume diagram. (2)

(b) Calculate EACH of the following:

(i) The compressor power; (4)

(ii) The heat removed in the inter-cooler; (4)

(iii) The heat removed by the cooling water in the low- and high-pressure cylinders. (6)

Note: for air R = 0.287 kJ⁄(kg k); C_p = 1.005 kJ⁄(kg K.)