the ratio of the work output of a heat engine to the heat input expressed in the same units of energy.
Origin of thermal efficiency
First recorded in 1905–10
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British Dictionary definitions for thermal efficiency
the ratio of the work done by a heat engine to the energy supplied to itCompare efficiency
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