Carnot Efficiency

Thermodynamics · 1824

Equation: η_max = 1 − T_c/T_h
Field: Thermodynamics
Named After: Sadi Carnot
Symbols: η_max the greatest possible efficiency of any heat engine · T_h temperature of the hot reservoir · T_c of the cold, both in kelvin
Year: 1824

Significance

The ceiling on every engine ever built, set in 1824 before anyone knew what heat was. Only the two temperatures matter — not the fluid, not the design. A car engine at 2,000 K exhausting to 300 K could at best reach 85 %; the second law, and metallurgy, keep it near a third of that.

Machines

Stirling Engine Steam Turbine Vapour-Compression Refrigerator

Requires

Second Law of Thermodynamics Thermal Efficiency

Required By

Coefficient of Performance

Referenced by

equation

Coefficient of Performance Second Law of Thermodynamics Thermal Efficiency

machine

Steam Turbine Stirling Engine Vapour-Compression Refrigerator

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From the Equations database in Notion, last edited 2026-08-18. This page is the row, rendered by the build; nothing on it is written by hand.