Thermal efficiency

Thermal efficiency is a dimensionless measure of how well a device makes use of thermal energy. For a heat engine it is the ratio of net work output to heat input, and because output can never exceed input this figure is always a fraction less than one. For a heat pump the equivalent figure is the coefficient of performance, the ratio of net heat output to energy input, which can exceed one. Both are bounded by the Carnot theorem's theoretical limit, and real devices such as internal combustion engines, steam turbines and refrigeration systems typically fall well short of that theoretical maximum. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/