Economisers are used to heat: (a) condensed steam (b) air (c) steam (d) feed water

By BYJU'S Exam Prep

Updated on: September 25th, 2023

Economisers are used to heat the feed water. It also goes by the name of the feed water heater. It is a device that heats the feed water using the waste heat from the flue gases. The power plant’s efficiency is increased by the economist.


It is a heat exchanger mechanism in a steam boiler that, in a thermal power plant, heats fluids or recovers leftover heat from the combustion byproduct, i.e. flue gases, before being expelled by the chimney. In the flue gas stream, the economizer is located before the air pre-heater.

Air preheater

  • Large boilers found in thermal power plants that generate electricity require air preheaters.
  • Any device created to heat air before another process (such as combustion in a boiler) with the primary goal of improving the process’ thermal efficiency is referred to as an air preheater or air heater.
  • The air preheater’s function is to recover heat from boiler flue gas, which raises the boiler’s thermal efficiency by minimizing the amount of heat that is lost in the flue gas.


  • Using a superheater, wet or saturated steam is transformed into superheated or dry steam.
  • Steam turbines and steam engines, as well as procedures like steam reforming, all employ superheated steam.
  • Although the steam in the superheater is getting hotter, the pressure is staying the same as it was in the boiler.


Economisers are used to heating: (a) condensed steam (b) air (c) steam (d) feed water

Water used as feed is heated by economisers. It heats the feed water with the help of waste heat from flue gas.

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