Q8. A single acting, two stage reciprocating compressors is designed for minimum work with perfect intercooling.
The low-pressure cylinder contains a mass of 0.02 kg of air when the piston is at bottom dead centre.
The air is compressed from a pressure and temperature of 0.95 bar and 25℃ respectively through an overall pressure ratio of 16 :1.
The index of expansion and compression in both stages is 1.28. The clearance volume in each stage is 5 % of the respective swept volume and the compressor runs at a speed of 500 rev/min.
(a) Sketch the cycle on a pressure-Volume diagram. (2)
(b)Calculate EACH of the following.
(i) The compressor indicated power; (6)
(ii) The heat rejected during the compression process; (4)
(iii) The rate of heat rejection in the intercooler. (4)
Note: for air γ = 1.4, Cp = 1.005 kJ⁄(kg K) and R = 0.287 kJ⁄(kg K)
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