Question

A Rankine cycle uses water as its working fluid. The mass flow rate of water through the cycle is 150 kg/s. Superheated vapour exits the boiler at 8 MPa and 560 °C. The condenser pressure is 8 kPa. The water at the pump inlet is 35 °C. The isentropic efficiency of the pump is 75% and the isentropic efficiency of the turbine is 91%. The turbine and pump can be treated as adiabatic. The pressure drops of the working fluid as it follows through the boiler and through the condenser are negligible. Kinetic and potential energy effects can also be ignored. For your analysis use the state point numbering scheme indicated in the following schematic: Do the following:

I. Draw the state points on a T-s diagram. Take care to locate each point in the correct region: superheated, mixed and subcooled.

II. Calculate the power developed in by the turbine.

III. Calculate the rate of heat transfer to the steam passing through the boiler.

IV. Calculate the power consumed by the pump in MW.

V. Calculate the rate of heat transfer from the cycle to the cooling water in the condenser in MW.

VI. Calculate the cycle’s back work ratio.

BONUS: Comment on state 2, what kind of effect can this have on the turbine performance?

Answer 1