Transcription of Thermo 7e SM Chap10-1 - SFU.ca
1 PROPRIETARY MATERIAL. 2011 The McGraw-Hill Companies, Inc. Limited distribution permitted only to teachers and educators for course preparation. If you are a student using this Manual, you are using it without permission. 10-95 10-90 A combined gas-steam power plant is considered. The topping cycle is a gas- turbine cycle and the bottoming cycle is a nonideal reheat Rankine cycle . The moisture percentage at the exit of the low-pressure turbine , the steam temperature at the inlet of the high-pressure turbine , and the thermal efficiency of the combined cycle are to be determined. Assumptions 1 Steady operating conditions exist. 2 Kinetic and potential energy changes are negligible. 3 Air is an ideal gas with variable specific heats. Analysis (a) We obtain the air properties from EES. The analysis of gas cycle is as follows kJ/kg 100kJ/kg 700C950kJ/kg 700kJ/kg 100C15kJ/kg hThhhhhhhhhssPsPThThhhhhhhhhssPsPThTsTsT sCssCs From the steam tables (Tables A-4, A-5, and A-6 or from EES), kJ/kg.
2 1kJ 1kPa 106000/kgm ,1233121inpI,3kPa 10 @ 1kPa 10 @ 1 whhPPwhhpff vvv kJ/kg 10 KkJ/kg 166665665555 fgsfsfgfssshxhhsssxssPshTP 126ss T3 6 MPa 10 kPa 8sQout Qin 711 10s 9 GAS cycle STEAM cycle 950 C15 C541 MPa 1084s 63 6 12 Steam turbineGas turbineCondenserpump 5 4 78 9 1011 Combustion chamber Compressor Heat exchanger PROPRIETARY MATERIAL. 2011 The McGraw-Hill Companies, Inc. Limited distribution permitted only to teachers and educators for course preparation. If you are a student using this Manual, you are using it without permission. 10-96 10kJ/kg (b) Noting that0 pe ke WQ for the heat exchanger, the steady-flow energy balance equation yields kJ/kg ) )(10() () () (441110air4523outin hhhhmhhmhhmhmhmEEsseeii Also, sTsTsshhhhhhhhhssPshTP4334434343443333 MPa 1 ?MPa 6 The temperature at the inlet of the high-pressure turbine may be obtained by a trial-error approach or using EES from the above relations.
3 The answer is T3 = C. Then, the enthalpy at state 3 becomes: h3 = kJ/kg (c) kW 4328kJ/kg 10109airgasT, hhmW kW 2687kJ/kg 1078airgasC, hhmW kW 164126874328gasC,gasT,gasnet, WWW kW 1265kJ/kg , hhhhmW kW , pumpwmW kW ,steamT,steamnet, WWW kW 2897 12561641steamnet,gasnet,plantnet,WWW (d) kW 7476kJ/kg 1089airin hhmQ 7476kW 2897inplantnet,thQW
