Question

Problem 8.044 Water is the working fluid in a regenerative Rankine cycle with one closed feedwater heater and one open feedwater heater. Steam enters the turbine at 1400 lbf/in.2 and 1000°F and expands to 500 lbf/in.2, where some of the steam is extracted and diverted to the closed feedwater heater. Condensate exiting the closed feedwater heater as saturated liquid at 500 lbf/in.2 undergoes a throttling process to 120 lbf/in.2 as it passes through a trap into the open feedwater heater. The feedwater leaves the closed feedwater heater at 1400 lbf/in.2 and a temperature equal to the saturation temperature at 500 lbf/in.2 The remaining steam expands through the second-stage turbine to 120 lbf/in.2, where some of the steam is extracted and diverted to the open feedwater heater operating at 120 lbf/in.2 Saturated liquid exits the open feedwater heater at 120 lbf/in.2 The remaining steam expands through the third-stage turbine to the condenser pressure of 3.5 lbf/in.2 The turbine stages and the pumps each operate adiabatically with isentropic efficiencies of 85%. Flow through the condenser, closed feedwater heater, open feedwater heater, and steam generator is at constant pressure. The net power output of the cycle is 1 x 109 Btu/h. Determine for the cycle: (a) the mass flow rate of steam entering the first stage of the turbine, in lb/h. (b) the rate of heat transfer, in Btu/h, to the working fluid passing through the steam generator. (c) the percent thermal efficiency

Answer 1