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Q3. A single acting, 2 -stage reciprocating air compressor is designed with some intercooling. The compressor has equal stage pressure ratios and delivers air from initial conditions of 0.95 bar and 285 K.

At the entrance to the second stage the temperature is 300 K. The index of both compression and expansion is 1.29 and it applies to both stages. The final delivery pressure is 12.90 bar.

a) Draw the p-V diagram of the compressor. (3)

b) Calculate EACH of the following:

i) The specific work required by the compressor; (10)

ii) The thermal efficiency. (3)

Note: For Air C_p = 1005 J/kgK, C_v = 718 J/kgK