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WRITTEN TEST ENERGY SYSTEMS 08 SEPTEMBER 2020 - PROF. S. CONSONNI Data Values from tables/Mollier charts Data from person code Person code: 12345678 1 2 3 49999 X4 6 Y 360 Problem 1 x LHV, MJ/kg MM, kg/kmole fuel CH4 0.72 50 16 CO 0.09 10 28 CO2 0.19 0 44 air xN2 0.79 xO2 0.21 air temperature °C 25 molar mass air 28.84 flue gases xO2 0.05 stack temperature °C 150 Cp flue gases kJ/kgK 1.10 heat losses from boiler, % of LHV thermal power percentage 1% a) MM fuel 22.368 kg/kmole mass fractions yCH4 0.515 yCO 0.115 yCO2 0.370 LHV fuel = yCH4*LHV,CH4 + yCO*LHV,CO = 26.90 MJ/kg b) xCH4 + xCO + xCO2 + (1+ ε)*(2 xCH4 + 1/2 xCO)*(O2 + 3.76 N2) --> (xCH4 + xCO + xCO2) CO2 + 2xCH4 H2O + ε*(2 xCH4 + 1/2 xCO) O2 + 3.76*(1+ ε)*(2 xCH4 + 1/2 xCO) N2 xO2 = ε*(2 xCH4 + 1/2 xCO) / [xCH4 + xCO + xCO2 + 2xCH4 + ε*(2 xCH4 + 1/2 xCO) + 3.76*(1+ ε)*(2 xCH4 + 1/2 xCO)] ε = [xO2*(xCH4 + xCO + xCO2 + 2xCH4 + 3.76*(2 xCH4 + 1/2 xCO))]/[(2 xCH4 + 1/2 xCO - xO2*(1 + 3.76*(2 xCH4 + 1/2 xCO)))] = 0.354 c) stoichiometric air/fuel mole ratio, beta_stoich (mole air/mol fuel) 7.08 computed as xCH4 * 2 (stoichiom ratio for CH4)+ xCO * 0.5 ( stoichiom ratio for CO) air/fuel mole ratio, beta (mole air/mole fuel) 9.584 beta = beta_ stoich*(1+eps) air/fuel mass ratio, alfa 12.35760341 alfa = beta * Mmair/Mmfuel boiler efficiency 0.92 from energy balance of boiler: boiler eff = 1 - heat losses - (alfa +1) Cpflue (Tstack-25) / LHV Problem 2 pcond,des = 0.1 bar Tain,des = 25 °C Taout,des = 35 °C Tcond,des = 45.81 °C DTa = 10 °C ε,des = DTa,des / (Tcond-Tain,des) = 0.481 condensing fluid (CC infinite) --> NTU,des = 0.655 Tain = 35 °C NTU = cost --> ε = cost Q = cost, ma = cost --> DTa = cost --> Tcond = Ta,in + DTa / ε = 55.81 °C pcond = 0.164 ba r Q = 0.5 Qdes, ma = cost --> DTa = DTa,des/2 = 5 °C NTU = cost…