The economizer is a device installed in the lower part of the flue of the boiler for recovering the waste heat of the exhaust smoke. The boiler feed water is heated to the heating surface of the saturated water under the steam pressure, because it absorbs the heat of the high temperature flue gas The smoke exhaust gas temperature, saving energy, improve the efficiency, so called the economizer.

The steel pipe economizer is not subject to pressure restrictions and can be used as a boiling type, typically made of carbon steel pipe having an outside diameter of 32 to 51 mm. Sometimes in the tube plus fins and fins to improve the heat transfer effect. The steel pipe economizer consists of a horizontally arranged parallel elbow pipe (formerly known as a serpentine tube).

Economizer is mainly applicable to industry, in recent years also spread to agriculture and some related industries on the business.