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Q2. A two-stage, single acting, water cooled, reciprocating air compressor is designed for minimum work and fitted with an after cooler.

It delivers air at the rate of 17 m³/min at free air conditions of 1.01325 bar 0℃.

The air is compressed from a pressure and temperature of 1 bar 33℃ to a pressure of 30 bar and the air leaves the after cooler at a temperature of 45℃.

The law for all expansion and compression processes is pV^1.3 = constant.

(a) Sketch the cycle on a Pressure–Volume diagram. (2)

(b) Calculate EACH of the following:

(i) the stage power; (4)

(ii) the enthalpy rise of the air in each stage; (4)

(iii) the total heat removed by the cooling water. (6)

Note:  for air R = 0.287 kJ/kg K, C_p =1.005 kJ/kg K