Water is maintained at a constant pressure of 400 kPa while

Water is maintained at a constant pressure of 400 kPa while the temperature changes from 30degreeC to 400degreeC. Calculate (a) the heat transfer in kJ/kg and (b) the change in specific entropy in kJ/kg-K.

Solution

solution

At 400 kpa and 30 C

h1 = 126.106 KJ/kg

S1 = 0.43667 KJ/kg.k

At 400 kpa and 400 C

h2 = 3067.1123 KJ/kg

S2 = 7.5677 KJ/kg.k

a) heat transfer = 3067.1123 - 126.106

= 2941 KJ/ kg

b) entropy =  7.5677 - 0.43667

= 7.13103 KJ/kg.k