A supply of steam at a pressure of 4 MPa and a temperature of 332°C (state 1) is used to do mechanical work as it expands to a pressure of 100 kPa and a quality of 90% (state 2). During the expansion process, 60 kJ/kg of heat is removed from the water. Two different designs are to be analysed.
a) The water expands upwards against a piston in a vertical cylinder of diameter 150 mm with an initial height of 17 mm. The water is initially at rest, and comes to rest again after the expansion. Neglecting potential energy effects, calculate the specific work done by the water.
b) For the process described in (a) above, calculate the potential energy change of the water as a fraction of the work, and comment.
c) In the second design, the steam expands in a steady-flow turbine. It enters the turbine at 150 m/s and leaves at 45 m/s. The entrance and exit are at the same height above ground. Calculate the specific work done by the water. Calculate the kinetic energy change of the water as a fraction of the work, and comment.