Thermodynamics

water leaves the heater at the condensation temperature of theextracted steam and that the extracted steam leaves the heateras a saturated liquid and is pumped to the line carrying thefeedwater.BoilerMixingchamber4 910P II1 – y7yClosedFWH8Condenser10–51E A steam power plant operates on an idealreheat–regenerative Rankine cycle with one reheater and twoopen feedwater heaters. Steam enters the high-pressure turbineat 1500 psia and 1100°F and leaves the low-pressure turbineat 1 psia. Steam is extracted from the turbine at 250 and40 psia, and it is reheated to 1000°F at a pressure of 140 psia.Water leaves both feedwater heaters as a saturated liquid.Heat is transferred to the steam in the boiler at a rate of 4 10 5 Btu/s. Show the cycle on a T-s diagram with respect tosaturation lines, and determine (a) the mass flow rate ofsteam through the boiler, (b) the net power output of theplant, and (c) the thermal efficiency of the cycle.6BoilerP IIIReheatery7OpenFWHII535FIGURE P10–504P IIHigh-Pturbine8 yOpenFWHI1 – y3FIGURE P10–51EHigh-Pturbine69210zP I2zP ILow-Pturbine1Low-Pturbine111 – y – z12Condenser1Chapter 10 | 59510–52 A steam power plant operates on the reheatregenerativeRankine cycle with a closed feedwater heater.Steam enters the turbine at 12.5 MPa and 550°C at a rate of24 kg/s and is condensed in the condenser at a pressure of20 kPa. Steam is reheated at 5 MPa to 550°C. Some steam isextracted from the low-pressure turbine at 1.0 MPa, is completelycondensed in the closed feedwater heater, and pumpedto 12.5 MPa before it mixes with the feedwater at the samepressure. Assuming an isentropic efficiency of 88 percent forboth the turbine and the pump, determine (a) the temperatureof the steam at the inlet of the closed feedwater heater,(b) the mass flow rate of the steam extracted from the turbinefor the closed feedwater heater, (c) the net power output, and(d) the thermal efficiency. Answers: (a) 328°C, (b) 4.29 kg/s,(c) 28.6 MW, (d) 39.3 percent4BoilerMixingchamber1156ClosedFWH10 23P II7FIGURE P10–52High-Pturbine8P IyLow-Pturbine191 – yCondenserSecond-Law Analysis of Vapor Power Cycles10–53C How can the second-law efficiency of a simpleideal Rankine cycle be improved?10–54 Determine the exergy destruction associated witheach of the processes of the Rankine cycle described in Prob.10–15, assuming a source temperature of 1500 K and a sinktemperature of 290 K.10–55 Determine the exergy destruction associated witheach of the processes of the Rankine cycle described in Prob.10–16, assuming a source temperature of 1500 K and a sinktemperature of 290 K. Answers: 0, 1112 kJ/kg, 0, 172.3 kJ/kg10–56 Determine the exergy destruction associated with theheat rejection process in Prob. 10–22. Assume a source temperatureof 1500 K and a sink temperature of 290 K. Also,determine the exergy of the steam at the boiler exit. Take P 0 100 kPa.10–57 Determine the exergy destruction associated witheach of the processes of the reheat Rankine cycle describedin Prob. 10–32. Assume a source temperature of 1800 K anda sink temperature of 300 K.