Nicolas Leonard Sadi Carnot

Carnot's 1824 book Reflections on the Motive Power of Fire analyzed ideal heat engines. It helped found thermodynamics by asking how much work a heat engine can produce.

The Carnot cycle is an idealized heat-engine cycle with reversible steps. It sets a theoretical upper limit on efficiency based on the temperatures of the hot and cold reservoirs.

Yes, Carnot wrote before the mature 19th-century formulation of energy conservation. His analysis still became central once later physicists reframed heat in thermodynamic terms.

Carnot gave the first deep analysis of engine efficiency in relation to heat flow. His 1824 work influenced later figures such as Rudolf Clausius and William Thomson.