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Who Invented Thermodynamics? Biography of Sadi Carnot – Part 3

written by: Haresh Khemani • edited by: Swagatam • updated: 5/4/2010

Sadi Carnot's book, Reflections on the Motive Power of Fire, set the foundation for the laws of thermodynamics. Unfortunately, he was unappreciated in his own time. He died at the young age of 36.

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    Discussions on Ideal Engine

    With his discussions on the ideal engine, Carnot made two points very clear to the readers:

    1) The engine working on Carnot cycle is the most efficient engine because in this engine there is no friction at and no exhaust gases are emitted. In the ideal engine there is no conduction of heat between different parts of the engine, which are at different temperatures. This clearly shows that Carnot knew the conduction of heat between different parts of the engine was responsible for reduction in efficiency of the steam engine and that to increase the efficiency of engine this wasteful heat transfer should be reduced.

    2) He also made it clear that the maximum efficiency of the engine was dependent not the type of fluid used by the engine, but on the temperatures between which the engine is operating, which he considered the motive power of heat.

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    Path breaking findings for the Second Law of Thermodynamics

    With these discoveries Carnot made two conclusions:

    1) The production of motive power is then due in steam engines not to actual consumption of the caloric but to its transportation from a warm body to a cold body.

    2) In the fall of caloric the motive power evidently increases with the difference of temperature between the warm and cold bodies, but we do not know whether it is proportional to this difference.

    These findings were the foundation for the second law of thermodynamics, which states that the natural tendency of heat is to flow from high temperature reservoir to low temperature reservoir.

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    Attitude toward Carnot and his Untimely Death

    Unfortunately, his contemporaries gave Carnot very little attention in the beginning. His researches started receiving importance only after 1834, when it was further elaborated and modernized by likes Emile Clapeyron, Clausius and Kelvin.

    Carnot died at the young age of 36 years in 1832 in a cholera epidemic. His belongings and large number of papers were buried with him; fortunately the important book was left for the world.

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    Carnot’s Legacy

    In his book Carnot had made it very clear that the higher the temperature of hot temperature reservoir of the engine, the higher is the efficiency of the engine. This implied that the engine working on superheated steam gives more efficiency. These concepts were better understood towards the end of nineteenth century and were used to improve the efficiency of the steam engine and later for the diesel and petrol engines.

    Back: Biography of Sadi Carnot Part 2

    Back: Biography of Sadi Carnot Part 1