Steam enters an engine at a pressure of 10 bar and 400°C. It is exhausted at 0.2 bar. The steam at exhaust is 0.9 dry. Find the change in entropy (in J/kg K).
Properties of steam and water is given as:
At 10 bar: Tsat = 179.91°C, vf = 0.001127 m3/kg, vg = 0.19444 m3/kg, uf = 761.67 kJ/kg, ufg = 1822 kJ/kg, hf = 762.79 kJ/kg, hfg = 2015.3 kJ/kgm, sf = 2.1386 kJ/kg K, sfg = 6.5864 kJ/kg K
At 0.2 bar: hf = 251.5 kJ/kg, hfg = 2358.4 kJ/kg, sf = 0.8321 kJ/kg K, sg = 7.9094 kJ/kg K
At 10 bar and 400°C : h = 3263.9 kJ/kg, s = 7.465 kJ/kg K
Correct answer is between '-265,262'. Can you explain this answer?