Economiser effect on boiler output: complete the sentence with the correct engineering impact. An economiser __________ the steam-raising capacity of a boiler by preheating the incoming feedwater using waste flue-gas heat. Choose the correct word to complete the statement.

Concept
An economiser transfers residual heat from flue gases to the feedwater. This raises feedwater temperature before it enters the boiler, which reduces the fuel required per kg of steam and effectively increases the steam-raising capacity for a given firing rate.

Why 'increases'

• Lower enthalpy rise needed in the boiler proper.
• Improved overall efficiency allows higher evaporation rate with the same fuel input.

Final Answer
increases