How is boiler efficiency defined, and what are two common methods to improve it?

• A. Efficiency is the ratio of useful steam energy to energy input; improve with proper combustion control and improved feedwater/insulation to minimize heat losses.
• B. Efficiency equals energy input.
• C. Efficiency is unrelated to heat losses.
• D. Efficiency is the ratio of water to steam mass.

Answer: (A)

Boiler efficiency measures how effectively the fuel’s energy is turned into useful steam energy. It’s defined as the ratio of useful energy output (the energy in the steam delivered) to the energy input (the energy in the fuel burned). Two common ways to improve it are boosting combustion efficiency (tuning burners and controlling the air-fuel mix to ensure complete, clean combustion) and reducing heat losses (improving feedwater heating, using economizers, and insulating surfaces to keep heat from escaping). This combination increases the fraction of fuel energy that actually becomes useful steam. The other definitions—like equating efficiency to energy input or to mass ratios, or ignoring heat losses—don’t describe how boiler efficiency works.