Q1. In a single acting two stage reciprocating air compressor, air is compressed from an inlet pressure and temperature of 0.9 bar and 20ºC respectively to a delivery pressure of 12 bar. The low-pressure cylinder has a bore of 250 mm, stroke of 160 mm and the clearance volume is 2.5% of the swept volume. The air enters the second stage at a pressure and temperature of 3 bar and 35ºC respectively. The compressor speed is 300 rev/min. The index of compression and expansion in both stages is 1.25. The mechanical efficiency is 0.85.
(a) Sketch the process on a p-V diagram.
(b) Calculate EACH of the following:
(i) The free air delivered per hour at free air conditions of 1 bar and 15℃
(ii) The input power required to drive the compressor
(iii) The heat removed in the inter-cooler.
Note: for air R = 0.287 kJ/kg K Cp = 1.005 kJ/kg K
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