Problem
A boiler generates 10,000 kg/h of steam. Enthalpy of steam is 2,780 kJ/kg, feedwater enthalpy is 420 kJ/kg, fuel consumption is 750 kg/h and calorific value is 42,000 kJ/kg. Calculate efficiency.
Given Data
Write all quantities in consistent SI units before substitution.
Formula and Solution
Useful heat = 10,000 × (2,780 − 420) = 23,600,000 kJ/h. Heat input = 750 × 42,000 = 31,500,000 kJ/h. Efficiency = 23,600,000 / 31,500,000 × 100 = 74.92%.
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.