Ekonomiser

Ekonomiser is a term used in Danish and Norwegian for devices or systems designed to save energy by recovering or using heat that would otherwise be wasted. In general, an economiser refers to a heat exchanger or control system that reduces fuel or energy consumption by making use of residual or outside heat.

In boiler and power plant applications, a boiler economiser is a heat exchanger placed in the path of flue gases after the furnace. It uses the remaining heat in exhaust gases to preheat the feedwater entering the boiler. This raises steam temperatures, improves thermal efficiency, and lowers fuel use. Common designs include coil-type and shell-type economisers. Key considerations include corrosion, fouling, temperature limits of the exhaust, water treatment to prevent scaling, and the need for regular maintenance to avoid leaks and efficiency losses.

In building HVAC, an economizer (often called an outside-air economizer) uses outdoor air to meet part of the cooling load when outdoor conditions are favorable. By admitting cooler ambient air instead of running cooling equipment, energy consumption can be reduced. Modern systems employ sensors for temperature or enthalpy, dampers, and control logic to prevent excessive humidity or poor indoor air quality. Limitations include humidity control requirements, potential for poor air quality if not well managed, and climate regions where outdoor air is rarely advantageous.

Overall, economisers contribute to energy efficiency by recovering heat or exploiting favorable ambient conditions, and their adoption depends on system type, climate, and careful control and maintenance.