Q8. A single acting, two stage reciprocating air compressors, takes in air at a pressure and temperature of 0.95 bar and 15℃ respectively and delivers it at 30 bars. The low-pressure cylinder has a bore of 300 mm and a stroke of 450 mm with a volumetric efficiency of 82 %.
The air enters the second stage at a pressure and temperature of 6 bar and 25℃ respectively.
The compressor speed is 200 rev/min.
The index of compression and expansion in both stages is 1.3.
(a) Sketch the process on a Pressure-Volume diagram. (2)
(b) Calculate EACH of the following:
(i) The compressor power; (4)
(ii) The heat removed in the inter-cooler; (4)
(iii) The heat removed by the cooling water in the low- and high-pressure cylinders. (6)
Note: for air R = 0.287 kJ⁄(kg k); Cp=1.005 kJ⁄(kg K.)
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