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Q3.A gaseous fuel has a volumetric composition of 60% methane (CH₄) and 40% ethane (C₂H₆) and is completely burned in 20% excess air.

The combustion gases are at a pressure and temperature of 3.346 bar and 400℃ respectively and are cooled at constant pressure to 100℃.

(a) Determine the combustion equation in kmols per kmol of fuel. (6)

(b) Calculate EACH of the following:

(i) the mean value of C_p for the dry gas; (4)

(ii) the dew point temperature of the gas; (3)

(iii) the quantity of heat removed from the dry gas per kmol of fuel. (3)

Note: atomic mass relationships H = 1, C = 12, O = 16, N = 14

air contains 21% oxygen by volume

Values of C_p: CO₂ = 1.113 kJ/kg K, O₂ = 1.024 kJ/kg K, N₂ = 1.091 kJ/kg K