waste heat recovery
noun
the use of heat that is produced in a thermodynamic cycle, as in a furnace, combustion engine, etc, in another process, such as heating feedwater or air
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012