Water is the working fluid in a reheat-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 is reheated to 900°F before entering the second-stage turbine, where it expands to 120 lbf/in.2 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 2 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, steam generator, and reheater is at constant pressure. The net power output of the cycle is 1.5 x 109 Btu/h. Let T0 = 60°F, p0 = 14.7 lbf/in.2 The table below provides steady-state operating data for the cycle. 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 exergy input, in Btu/h, to the working fluid passing through the steam generator. (c) the magnitude of the exergy output, in Btu/h, of the net power output.
Water is the working fluid in a reheat-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 is reheated to 900°F before entering the second-stage turbine, where it expands to 120 lbf/in.2 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 2 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, steam generator, and reheater is at constant pressure. The net power output of the cycle is 1.5 x 109 Btu/h. Let T0 = 60°F, p0 = 14.7 lbf/in.2 The table below provides steady-state operating data for the cycle.
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 exergy input, in Btu/h, to the working fluid passing through the steam generator.
(c) the magnitude of the exergy output, in Btu/h, of the net power output.
(d) the magnitude of the exergy loss in the condenser, in Btu/h.
(e) the exergy destroyed in the tubine, in Btu/h.
(f) the exergy destroyed in the open feedwater heater, in Btu/h.
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