Full exam for Energy Systems LM in the Mechanical Engineering degree programme at Politecnico di Milano. The document covers: Exam Energy Systems proff. Consonni, Martelli, Romano - 21 January 2019 Problem 1 LPG MM, kg/Mol 58.0 LHV of LPG, MJ/kg 45.75 O2 MM, kg/Mol 32 N2 MM, kg/Mol 28 Air MM, kg/Mol 28.840 C4H10 + 6.5O2 ‐‐> 4CO2 + 5H2O stoichiometric excess air 30% mols of O2 in stoich air per Mol of
Full exam for Energy Systems LM in the Mechanical Engineering degree programme at Politecnico di Milano. The document covers: Exam Energy Systems proff. Consonni, Martelli, Romano - 21 January 2019 Problem 1 LPG MM, kg/Mol 58.0 LHV of LPG, MJ/kg 45.75 O2 MM, kg/Mol 32 N2 MM, kg/Mol 28 Air MM, kg/Mol 28.840 C4H10 + 6.5O2 ‐‐> 4CO2 + 5H2O stoichiometric excess air 30% mols of O2 in stoich air per Mol of
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Exam Energy Systems proff. Consonni, Martelli, Romano - 21 January 2019 Problem 1 LPG MM, kg/Mol 58.0 LHV of LPG, MJ/kg 45.75 O2 MM, kg/Mol 32 N2 MM, kg/Mol 28 Air MM, kg/Mol 28.840 C4H10 + 6.5O2 ‐‐> 4CO2 + 5H2O stoichiometric excess air 30% mols of O2 in stoich air per Mol of C4H10 6.5 8.45 mols of N2 in stoich air per Mol of C4H10 24.440 31.772 kg of air per Mol of C4H10 892.320 1160.016 kg of air per kg of C4H10 15.385 20.000 kg of flue gases per kg of C4H10 16.385 21.000 (1 + kg of air per kg of C4H10) 1) water flow rate, m3/h 1.25 water flow rate, kg/s 0.347 T water in, °C 35.0 T water out, °C 60.0 water DT, °C 25.00 water cp, kJ/kg‐K 4.186 power to water, kW 36.34 (water flow rate * cp of water * DTwater ) boiler efficiency 0.9200 combustion power, kW 39.497 (Power to water/boiler eff) Fuel flow rate, kg/s 0.000863312 (Combustion power / LHVfuel) kgcombproducts/kgfuel 21.000 total flow of comb products, kg/s 0.0181 2) cp comb products, kJ/kg‐K 1.100 thermal capacity of comb products, kW/°C 0.01994 (total flow of c omb products * cp comb products) losses due to dissipation, % of LHV 0.600 losses due to dissipation, kW 0.2370 (combustion power * losses d ue to dissipation) power available in comb products, kW 39.260 (combustion power ‐ l osses) DT comb products, °C 1968.61 (power in comb products)/(thermal ca pacity of comb products) T flame, °C 1993.61 (Tref + DT of comb products) 3) power lost at stack, kW 2.923 (power available in comb products ‐ power to water) DT at stack, °C 146.56 (power lost at stack)/(thermal capacity of comb products) T stack, °C 171.56 (Tref + DT at stack) 5) effectiveness HE, % 93.03 (Tflame‐Tstack)/(Tflame‐Twater in) 6) Tflame' ‐ Tflame, °C 800 Tflame', °C 1193.61 T stack', °C 171.56 (unchanged) DT' comb products, °C 1022.05 power…
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