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Q1. A two stage, single acting reciprocating air compressor is designed for minimum work and has perfect inter-cooling. The pressure and temperature at inlet are 1 bar and 20ºC respectively, the discharge pressure is 36 bar. The swept volume of the first stage is 0.01 m³ and the clearance volume is 3% of the swept volume.

The polytrophic index for all the expansion and compression processes is 1.2, the mechanical efficiency of the compressor is 0.8 and the speed is 240 rev/min.

(a) Sketch the processes on a p-V diagram indicating the pressures and volumes.

(b) Calculate EACH of the following:

(i) The first stage volumetric efficiency

(ii) The mass of air delivered per second

(iii) The input power.

Note: For air R = 0.287 kJ/kgK