Q8. A water cooled two stage single acting reciprocating compressor is designed for minimum work with perfect intercooling. A total mass of 9 kg/min of air is compressed from a pressure and temperature of 0.9 bar and 27℃ respectively, through a pressure ratio of 25:1.
The clearance volume of each stage 5% of the respective swept volume.
The polytropic index of expansion and compression in both stages is 1.28.
The compressor speed is 400 rev/ min and the mechanical efficiency of the compressor drive is 85%.
(a) Sketch the cycle on a pressure-Volume diagram. (2)
(b) Calculate EACH Of the following:
(i) the input required to drive the compressor. (6)
(ii) the total heat removed by the jacket cooling water. (8)
Note: for air R = 287 J⁄(kg K) and Cp=1005 J⁄(kg K)
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