A power plant operates on a regenerative vapor power cycle w

A power plant operates on a regenerative vapor power cycle with one open feedwater heater. Steam enters the first turbine stage at 12 MPa, 560degreeC and expands to 1 MPa, where some of the steam is extracted and diverted to the open feedwater heater operating at 1 MPa. The remaining steam expands through the second turbine stage to the condenser pressure of 6 kPa. Saturated liquid exits the open feedwater heater at 1 MPa. The net power output for the cycle is 330 MW. For isentropic processes in the turbines and pumps, determine the cycle thermal efficiency. the mass flow rate into the first turbine stage, in kg/s.the rate of entropy production in the open feedwater heater, in kW/K.

Solution

For boiler, the steady flow energy equation (SFEE):

h₈ + Q₁ = h₁

Mass balance of feed water heater,

mh₂ + (1 -m)h₆ = h₇ = 762

Where, w = mass flow rate in kg/s.