The economizer is a heat recovery device that heats the boiler feed water with the waste heat of the flue gas. This tool calculates the heat recovered by the economizer and the corresponding fuel savings .
Formula
Q = ṁ × (h₂ − h₁) ÷ 3600
Fuel economy = Q × 3600 ÷ (η × Hu)
Fuel economy = Q × 3600 ÷ (η × Hu)
h₁ and h₂: enthalpy of water at economizer inlet and outlet (at boiler pressure, IAPWS-IF97).
Example
An economizer that heats 5,000 kg/h of feed water from 80 °C to 110 °C recovers around 175.4 kW of heat. With a 90% efficient natural gas boiler, this saves approx. 20.3 Sm³ of natural gas per hour and approx. 121,900 Sm³ per 6,000 hours of operation per year.
For details, you can see our article on fuel savings with economizers .