Document information
- University
- Politecnico di Milano
- Degree programme
- Mechanical Engineering
- Subject
- Energy Systems LM
- Academic year
- 2017-2018
- Classification
- Exam · Full exam
- Content
- Exam paper only
- Original format
- Text
- Searchable text
Full exam for Energy Systems LM in the Mechanical Engineering degree programme at Politecnico di Milano. The document covers: PROBLEM 1: Data Net electric power 500 kW fuel consumptio rate 200 l/h fuel density 0.789 kg/litro LHV ethanol 26.952 MJ/kg Molcular mass ethanol 46 kg/kMole Fluegases Cp 1.10 kJ/kg-K Fluegases temperature 450.00 °C Pinch point temp. Difference 10.00 °C air composition molar MM,
Full exam for Energy Systems LM in the Mechanical Engineering degree programme at Politecnico di Milano. The document covers: PROBLEM 1: Data Net electric power 500 kW fuel consumptio rate 200 l/h fuel density 0.789 kg/litro LHV ethanol 26.952 MJ/kg Molcular mass ethanol 46 kg/kMole Fluegases Cp 1.10 kJ/kg-K Fluegases temperature 450.00 °C Pinch point temp. Difference 10.00 °C air composition molar MM,
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PROBLEM 1: Data Net electric power 500 kW fuel consumptio rate 200 l/h fuel density 0.789 kg/litro LHV ethanol 26.952 MJ/kg Molcular mass ethanol 46 kg/kMole Fluegases Cp 1.10 kJ/kg-K Fluegases temperature 450.00 °C Pinch point temp. Difference 10.00 °C air composition molar MM, kg/kmol N2 0.770 28 O2 0.206 32 Ar 0.009 39.944 H2O gas 0.015 18 total 1.000 28.78 steam pressure 5.00 bar Cp air 1.01 kJ/kg‐K heat losses from HRSG walls 0.02 air temperature 1 °C referemce boiler efficiency 90% reference power plant effiicenc y 45% Afinned external / A internal tubes 10.00 flue gas side heat transfer coeff, W/m2‐K 40.00 steam side heat transfer coeff, W/m2‐K 90000.00 fin efficiency 60% Results Fuel mass flow rate 0.043833 kg/s calculated as fuel volumetric flow rate * density C atoms per mole of ethanol 2 H atorms per mole of ethanol 6 O atorms per mole of ethanol 1 stoichiom O2/fuel molar ratio 3 calculated with the relation derived from the atomic balance e q: nC+nH/4‐nO/2 stoichim air/fuel molar ratio 14.56311 O2_fuel ratio / X_air_O2 air/fuel mass ratio 9.111913 air_fuel_molar_ratio * Mmair/Mmfuel air mass flow rate, kg/s 0.399406 fuel mass flow rate * aòèha fuel chemical power, kW 1181.396 fuel mass flow rate * LHV flue gases mass flow rate, kg/s 0.443239 fuel + air mass flow rate evaporation temperature, °C 151.836 from tables of saturated H2O propertie s sat. Steam enthalpy, kJ/kg 2748.108 from tables of saturated H2O propertie s sat. Liquid enthalpy, kJ/kg 640.183 from tables of saturated H2O propertie s steam mass flow rate, kg/s 0.065319 from energy balance equation between HRSG inlet and pin ch point at evaporator inlet: (1‐loss)*mFG*CpFG*(TFG‐Teva‐DT_ stack temperature 161.84 Teva + DTpinch point useful thermal power, kW 137.6881 msteam*(h_OUT‐h_IN) thermal…
First page of the document.