Birth of Thermodynamics — Benôit Paul Émile Clapeyron

Benôit Paul Émile Clapeyron was one of the three C’s — Carnot, Clapeyron, and Clausius — who created the field of thermodynamics. This new field of science gave engineers the conceptual and quantitative tools to build the heat engines — steam engines, locomotives, turbines, and (later) the internal combustion engines — that powered the industrial revolution with.

Clapeyron was among a “lost generation” of French engineering graduates who launched their careers during the difficult time around Napoleon Bonaparte’s defeat and the Restoration of the French monarchy. Suddenly, the meritocratic path to promising careers in the military and government service was closed. Frustrated, Clapeyron joined fellow Polytechnique alum Gabriel Lame in Russia. There, they trained engineering students and helped modernize Russian transportation systems and infrastructure.

At the same time, English engineers were experimenting with a brand new technology — steam-powered railways. The progress of the English engineers was watched closely by Clapeyron and Lame and their colleagues in France, with whom they keep in touch. Everyone was keen to know what role steam-powered railroads might play in establishing transportation networks at the national, continental, and even intercontinental scales. In 1830, political changes in Russia brought Clapeyron back to France, where he joined a loose association of engineers responsible for designing and building the first railroads in France.

Even while he was caught up in the frenzy of railroad building, Clapeyron continued research and teaching on a broad number of topics in the area of applied mechanics. One of the most important questions facing engineers and industrialists, early in the 19th century, was how much mechanical work can be produced from a ton of coal. Sadi Carnot, son of Lazare Carnot, took the first step by outlining guiding principles in a pamphlet published in 1824. It was Clapeyron who translated Carnot’s theory of an ideal heat engine into terms that practicing engineers could apply.

Much earlier, James Watt had introduced the practice of plotting steam pressure versus volume inside the cylinder in order to better understand the work produced by the piston during a cycle. This helped engineers understand and refine the operation of steam engines. Clapeyron used the same approach to interpret Carnot’s theoretical results. Later, Rudolf Clausius, a German physicist, brought the work of Carnot and Clapeyron to completion by articulating the Second Law of thermodynamics.

Based on Clapeyron’s work engineers understand how, by adjusting the timing of the steam intake and exhaust to the cylinder they could increase the power produced from one ton of coal by 50%.

Benôit Paul Émile Clapeyron is one of the 72 engineers named on the Eiffel Tower.