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A steam turbine inlet is at 1200 kPa, 500°C. The actual exit is at 300 kPa, 300°C with an actual work of 407 kJ/kg. What is its reversible work output if ambient temperature is at 25°C?

A steam turbine inlet is at 1200 kPa, 500°C. The actual exit is at 300 kPa, 300°C with an actual work of 407 kJ/kg. What is its reversible work output if ambient temperature is at 25°C? Correct Answer 414.9 kJ/kg

T0 = 250C = 298.15 K The turbine is assumed to be adiabatic, so q = 0. Inlet state: hi = 3476.28 kJ/kg; si = 7.6758 kJ/kg K he = hi – w(ac) = 3476.28 – 407 = 3069.28 kJ/kg Actual exit state: Pe = 300 kPa, Te = 300 0C; se = 7.7022 kJ/kg K w(rev) = (hi – Tosi) – (he – Tose) + q(T0/TH) = (hi – he) + To(se – si) = (3476.28 – 3069.28) + 298.15(7.7022 – 7.6758) + 0 = 407 + 7.87 = 414.9 kJ/kg.

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