Nota: sinaisde entradae saidade energiade acordoshapiro

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1 Nota: sinaisde entradae saidade energiade acordoshapiro

2 An air compressor operates at steady state with air entering at p1 =1 bar, T1 = 20ºC, and exiting at p2 = 5 bar. Determine the work and heat transfer per unit of mass passing through the device, in kj/kg, if the air undergoes a polytropicprocess with n= 1.3. Neglect changes in kinetic and potential energy between the inlet and the exit. Use the ideal gas model for air. W = n n Const n n n n vdp= dp= Const P 1 = n 1 n n 1 P ( Pv Pv )

3 Balanço energético da turbina Turbina adiabática Rendimento isentrópico da turbina Turbina de vapor Turbina com G.P.

4 Compressor adiabático

5 Balançode energia 0= W bomba -W turbina +Q caldeira -Q condensador W util = = W bomba -W turbina

6 Segunda Lei da Termodinâmica Enunciado de Kelvin-Planck. Estaé umamáquinatérmicaqueviola o enunciado de Kelvin-Plank da segunda Lei É impossível a construção de um dispositivo que, por si só, isto é, sem intervenção do meio exterior, consiga transformar integralmente em trabalho o calor absorvido de uma fonte a uma dada temperatura uniforme.

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9 Earliest heat engine operated on steam: Process I - add steam into the piston-cylinder to raise the pressure above atmospheric pressure and thus push the piston down Process II - add water to condense the steam and lower the pressure below atmospheric pressure so the piston is pulled back up

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19 Ciclo de vapor Consider each process separately applying conservation of energy For steady-state, neglecting KE and PE effects, conservation of energy applied to a CV yields Q& m& W& m& 1 de CV CV 2 = + + ( h ) 1/ 2( 2 in hout + Vin Vout m& dt ) + g( z in z out ) Q& CV W& CV 0= + + ( hin hout) m& m&

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32 Ciclo de Rankine com sobreaquecimento Qualo efeitono trabalhoespecificodo cicloe no seurendimento?

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34 turbina bomba

35 Ciclo de Rankine

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40 The Organic Rankine cycle (ORC) is named for its use of an organic, high molecular mass fluid with a liquid-vaporphase change, or boiling point, occurring at a lower temperature than the water-steam phase change. The fluid allowsrankine cycle heat recovery from lower temperature sources such as biomass combustion, industrial waste heat, geothermal heat, solar ponds etc. The low-temperature heat is converted into useful work, that can itself be converted into electricity. A prototype was first developed and exhibited in 1961 by solar engineers Harry Zvi Tabor and Lucien Bronicki. Examples of working fluids[edit] CFCs: Banned by Montreal Protocol due to ozone depletion(e.g R-11 R-12) HCFCs: Phasing out due to Copenhagen Amendment to Montreal Protocol(e.g. R-22 R-123) HFCs(e.g R134a R245fa) HCs: Flammable, common by-products of gas processing facilities (e.g. isobutane, pentane, propane)

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47 Entrada em serviço 1985 Potência total instalada (MW) 1192 Número de grupos 4 Combustível Carvão Gerador de Vapor Tipo Circulação natural Capacidade vaporização (t/h) 950 Temperatura (ºC) 535 Pressão vapor (Pa) 16,7 x 106 4,7 x 106 Rendimento (%) 87 Consumo (máx. carga) (t/h) 106 Chaminé (m) 225 Turbina Tipo Fluxo axial Velocidade (r.p.m.) Nº de corpos AP 1 MP 1 BP 2 Pressão de vapor (Pa) AP 16,7 x 106 MP 4,7 x 106 Rendimento (%) 45

48 Caldeiras Fabricante: Mague/Foster Wheeler EC Modelo: circulação natural Combustível: carvão pulverizado Consumo de combustível: 108 ton/h Temperatura da água de alimentação: 256 C Produção de vapor a M.C.R.: 264 kg/s Temperatura de saída de vapor sobreaquecido: 535 C Pressão de saída de vapor sobreaquecido: 167 bar Eficiência: 87,8 %.

49 Turbinas Fabricante: Mague/Asea Brown Boveri Modelo: D4Y450 (4 cilindros, veio único, acção-reacção) Velocidade nominal: 3000 rpm Temperatura do vapor à entrada do cilindro de AP: 530 C Pressão do vapor à entrada do cilindro de AP: 162 bar Temperatura do vapor à entrada do cilindro de MP: 530 C Pressão do vapor à entrada do cilindro de MP: 43 bar

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52 Funcionamento da central do PEGO

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54 Diagram of a water-tube boiler.

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62 Reactor Plant

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64 Main Condenser

65 Steam is the working fluid in an ideal Rankinecycle. Saturated vapor enters the turbine at 8.0 MPaand saturated liquid exits the condenser at a pressure of MPa. The net power output of the cycle is 100 MW. Determine for the cycle (a) The thermal efficiency, (b) the back work ratio, (c) the mass flow rate of the steam, in kg/h, (d) the rate of heat transfer,, into the working fluid as it passes through the boiler, in MW, (e) the rate of heat transfer, from the condensing steam as it passes through the condenser, in MW, (f) the mass flow rate of the condenser cooling water, in kg/ h, if cooling water enters the condenser at 15C and exits at 35C.

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67 Reconsider the vapor power cycle of Example 8.1, but include in the analysis that the turbine and the pump each have an isentropic efficiency of 85%. Determine for the modified cycle (a) the thermal efficiency, (b) the mass flow rate of steam, in kg/h, for a net power output of 100 MW, (c) the rate of heat transfer into the working fluid as it passes through the boiler, in MW, (d) the rate of heat transfer from the condensing steam as it passes through the condenser, in MW, (e) the mass flow rate of the condenser cooling water, in kg/h, if cooling water enters the condenser at 15C and exits as 35C. Discuss the effects on the vapor cycle of irreversibilities within the turbine and pump.

68 Central nuclear