Mass of air, m = 1 kg

Initial temperature, T_{1} = T0 = 290 K

Final temperature, T_{2} = 400 K

Initial pressure, p_{1} = p_{0} = 1 bar

Final pressure, p_{2} = 6 bar.

**(i) The irreversibility, I : **

We know that reversible work,

W_{rev.} = Change in internal energy – T_{0} × Change in entropy

= 134.37 kJ/kg (–) [–ve sign indicates that work is done on the air] Actual work is given by

**The index n for the compression is given by :**

(–ve sign means that the work is done on the air)

Now, irreversibility = W_{rev} – W_{actual}

= – 134.37 – (– 144.8) = 10.43 kJ.

**(ii) The effectiveness, ∈ :**

∈ = \(\cfrac{W_{rev}}{W_{actual}}\)= \(\cfrac{-134.37}{-144.8}\) = 0.928 or 92.8%.