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Q8. In a two-stage single acting reciprocating compressor, air is compressed from suction conditions of 0.9 bar, 20℃ to a delivery pressure of 12 bar.

The second stage entry conditions are 3 bar and 35℃.

The low-pressure cylinder has a bore of 300 mm, a stroke of 150 mm and a clearance volume of 2.5 % of swept volume.

The index of expansion and compression in both stages is 1.25.

The compressor speed is 300 rev/min

(a) Sketch the cycle on a pressure-Volume diagram. (2)

(b) Calculate EACH of the following:

(i) The free air delivered per hour at conditions of 1 bar and 0℃: (6)

(ii) The indicated power required to drive the compressor. (8)

Note : for air R = 287J⁄(kg K)  and C_p = 1005 J⁄(kg K).