Steam enters a turbine operating at steady state at 4 MPa, 500°C with a mass flow rate of 50 kg/s. Saturated vapor exits at 10 kPa and the corresponding power developed is 42 MW. The effects of motion and gravity are negligible.

(a) For a control volume enclosing the turbine, determine the rate of heat transfer, in MW, from the turbine to its surroundings. Assuming an average turbine outer surface temperature of 50°C, determine the rate of exergy destruction, in MW.

(b) If the turbine is located in a facility where the ambient temperature is 27°C, determine the rate of exergy destruction for an enlarged control volume including the turbine and its immediate surroundings so heat transfer takes place at the ambient temperature. Explain why the exergy destruction values of parts (a) and (b) differ.
Let T0 5 300 K, p0 5 100 kPa.

modeled as an ideal gas with cp 5 1.01 kJ/kg ? K. Stray heat transfer can be ignored. Determine, in kJ per kg of air flowing,

(a) the power required by the compressor and

(b) the rate of exergy destruction within the compressor. Let T0 5 300 K, p0 5 1 bar. Ignore the effects of motion and gravity.