A natural gas containing 82.0 mole% CH4 and the balance C2H6 is burned with 20% excess air in a boiler furnace. The fuel gas enters the furnace at 298 K, and the air is preheated to 423 K. The heat capacities of the stack gas components may be assumed to have the following constant values:

(a) Assuming complete combustion of the fuel, calculate the adiabatic flame temperature.

(b) How would the flame temperature change if the percent excess air were increased? How would it change if the percentage of methane in the fuel increased? Briefly explain both of youranswers.

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CO2: H₂O(v): C, = 50.0 J/(mol-K) C₂ = 38.5 J/(mol-K) O₂: Cp 33.1 J/(mol-K) N₂: Cp 31.3 J/(mol-K)