Recuperator

A recuperator is a counter-flow heat exchanger built to recover waste heat from an industrial process or a building's exhaust air stream and use it to preheat incoming air. In industrial furnaces it recovers 70 to 80 percent of waste heat from flue gases to preheat combustion air, reaching temperatures of 850 to 900 degrees Celsius, while ventilation recuperators can recover up to 95 percent of the heat that would otherwise be expelled from a building. In gas turbines, recuperators preheat compressed air before combustion, which can roughly double the efficiency of smaller microturbines that would otherwise run at low pressure ratios. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/