Problem
A furnace burns 1,000 kg/h fuel with 18,000 kg/h actual air. Calculate actual air-fuel ratio. If theoretical air is 14 kg/kg fuel, calculate excess air.
Given Data
Write all quantities in consistent SI units before substitution.
Formula and Solution
Actual A/F = 18,000/1,000 = 18 kg/kg. Excess air = (18−14)/14 ×100 = 28.57%.
Engineering Check
Check units, magnitude and physical meaning. State any simplifying assumptions and avoid mixing mass flow per hour with energy per second.
Practice Variation
Repeat the problem after changing one input by 10% and explain how the answer responds.