Answer:
(a) 65.04%
(b) 16.91%
Solution:
As per the question:
At inlet:
Pressure of the compressor, P = 140 kPa
Temperature, T =
= 263 K
Isentropic work, W = 700 kPa
At outlet:
Pressure, P' = 700 kPa
Temperature, T' =
= 333 K
Now, from the steam table;
At the inlet , at a P = 700 kPa, T =
:
h = 243.40 kJ/kg, s = 0.9606 kJ/kg.K
At outlet, at P = 140 kPa, T =
:
h' = 296.69 kJ/kg, s' = 1.0182 kJ/kg.K
Also in isentropic process, s =
and
at 700kPa
(a) Isentropic efficiency of the compressor, 

(b) The temperature of the environment,
= 273 + 27 = 300 K
Availability at state 1, 
Similarly for state 2, 
Now, the efficiency of the compressor as per the second law;
= 67.57%