Sadi Carnot (physicist)

Nicolas Léonard Sadi Carnot, wire of Lazare Carnot

See also: Lazare Nicolas Marguerite Carnot, Carnot

Family context

Sadi Carnot, of the name of the Persan poet Saadi of Shiraz very admired of his/her father, is the oldest son of Lazare Nicolas Marguerite Carnot says the Grand Carnot , then 43 years old and the top of its career. Mathematician and engineer shining, raise Gaspard Monge, author of a Essai on the machines in general (1754), Lazare Carnot was also soldier, born leader and patriot. He was elected with the constituent Assembly of 1789 then to the Convention, and voted the death of the king Louis XVI. During the wars of the French revolution, within the Committee of Public Hello, he is the Organizer of the Victoire. Member of the Directory, he was Minister for the War of Napoleon Bonaparte from April at October 1800 then Minister of Interior Department at the time of the Hundred Days, in 1815. In October of the same year, after the defeat of Napoleon, it is exiled in Belgium, then in Poland, finally in Germany and never returned to France.

He comprehensible that any wire was dominated, would have been even crushed by the personality of such a father to make known itself by the only virtue of his name, to even take refuge in the revolt. With Nicolas Léonard Sadi Carnot, it was different: although his/her father, after having been success, politically fell in disgrace, Sadi Carnot overcame not only the difficulties of this situation, but he managed by his work to acquire a durable fame where his/her father had his apartments of function. His/her mother, Sophie Dupont, are resulting from an easy family of Saint-Omer. Following the coup d'etat of September 4th, 1797, Lazare Carnot had expatrier until January 1800 when it was pardoned by Bonaparte; during this period Sadi lived with his/her mother in the family home of Saint-Omer. In August 1807 Lazare Carnot, returned to the private life by the suppression of the Tribunat, decides to deal itself with the education of its two sons; he teaches mathematics, sciences, the languages and the music to them. Of this first formation, Sadi undoubtedly kept the influence of certain designs of his/her father as well as a practice of talks on the contents of its courses and later of its personal work. In 1811, Sadi Carnot enters to the Lycée Charlemagne the preparatory class of Pierre-Louis Marie Bourdon to prepare the contest of the Polytechnic school. Having reached on June 1st 1812 16 years the necessary minimum age, Sadi can next in August arise to the contest where it is received 24e on 179 and is incorporated in the second division on November 2nd.

A military career without real glory

Training of polytechnician (November 1812 - September 1814)

In 1812-1813, the courses functioned normally in spite of the reverses undergone by the imperial armies. Its professors are called Reynaud for the analysis, Poisson for mechanics, Hachette for the descriptive geometry, Louis Jacques Thénard for chemistry general and applied, Jean Henri Hassenfratz for physics and François Arago for the Infinitesimal calculus and the theory of machines. During this first year, it also had as a repeater of the men such as Alexis Petit for physics or Pierre Louis Dulong for the chemistry of which it used work later on. The appreciations, results with the interrogations as its row with the examination of passage in second year (20th on 179) show that Sadi worked well during this first year. It even seems that it was proposed in October 1813 for an immediate passage in the artillery section of the School of Metz but finally considered to be too young, it inspects Fortification S, trace of the plans and writes many reports/ratios. It seems that it is not well treated and that its recommendations are ignored; its career stagnates.

The ordinance of May 6th, 1818 carries formation of a royal body staff and a school of application for the service of the general staff. September 15th, 1818 Sadi Carnot profits from a six months leave to prepare the examination of entry in Paris

The installation in Paris

By ordinance of January 20th 1819, it is allowed with the state major de Paris, with the rank of lieutenant and placed of availability, it perceives two thirds of the pay rough as of the scientific title of worker. Placing close to his/her uncle Joseph in a small apartment of the popular quarters of the Marsh which it occupied until worms the middle of 1831, Sadi Carnot follows courses to the Sorbonne and the Collège de France but not to the School of the mines, for which one needed an authorization of the administration higher than it solicited forever, and where he could have become acquainted with the young person Emile Clapeyron. It regularly goes to the Conservatoire national Arts and Trades where Clement-Désormes exempts a course of chemistry applied to the Art S and Jean-Baptiste Say a course of industrial economy. He attends also the Botanical garden and the Bibliothèque of the King but also the Musée of Louvre and the Italian Théâtre of Paris}} Sadi are allowed in the 8th artillery company with at most the rank of warrant officer or corporal.

In August 1831, the publication of two memories of Pierre Louis Dulong encourages it to resume its work on the physical properties of the Gaz. This same year, it had an access of Fièvre Scarlatine and fell seriously sick, with crises of is delirious during a certain time. In April 1832, the encyclopedic Revue gives an account of work of the baron Blein in an article signed S.C, probably Sadi Carnot. The portrait that Despoix at that time traces of Sadi watch the face of a tired man, with the anxious glance, which the mental equilibrium does not appear assured any more.

Condenser and high pressure or the research of the optimal output

Approximately 50 years later, and in order to remove the wasting of heat related on the warming and the alternative cooling of the cylinder, James Watt condensed the vapor in a separated cold cylinder, or condenser , while the principal cylinder was maintained hot permanently. In addition, it used hot vapor to reduce the piston in the cylinder, thus reducing still the loss of heat. Watt noticed that a considerable economy could be carried out if the arrival of the vapor were cut before the piston did not move in the cylinder: the vapor locked up would continue to reduce the piston with a slightly decreasing pressure. When the vapor would pass in the condenser, there would remain to him a little “elasticity” (of pressure): one spoke then about action by expansion . From 1811 to 1840, art to pump the water of the mines of Cornouailles was regularly reported in the Monthly Engine to defer published by Thomas and John Lean and taken again by publications such as the Annales of chemistry and physics . These statements established in an unquestionable way the superiority of the machines with high pressure. Moreover, since 1820, the majority of the engineers seemed convinced that there was a limit determined with the quantity of work which could be obtained with a quantity of heat given.

These data, true éphémérides, had the advantage of translating the action of the various machines of pumping of way simple and directly in work units (weight water and height to which it was high). Sadi Carnot was inspired some in its reflection on the basic principles by the heat engines.

This preliminary part of the Réflexions contains the fundamental idea that everywhere where there is a difference in temperature, there exists the possibility of generating horse-power , idea which plays a central role in thermodynamics. And its corollary is not less important: it is impossible to produce horse-power unless one does not have at the same time of a cold body and a hot body . That perhaps regarded as the first statement of the second law of thermodynamics also called principle of Carnot, even if it revêt still a form inaccurate, usually called machine of Carnot , and being able alternatively to exchange easily heat with a hot body and a cold body ( Figure 6 ). In its study, the Thermal engine is strictly tiny room to its essential components:

a Cylinder closed, filled up of an acting substance which can be vapor or a gas
a mobile Piston moving without friction
a hot body which represents the equivalent of the Foyer of a real steam engine
a cold body, are equivalent of the Condenseur

Carnot confirms that it is the difference in temperature between the hot body and the cold body, and not the difference in pressure which undergoes the acting substance, which determines the work provided by the engine. It seems that he is indebted of this important idea to his friends Clément and Desormes ( Figure 3 ). The cylinder is finally separated from the cold body; and compression is continued so that the acting substance is heated Adiabatique lies ( Figure 4 ). The cycle is completed when the acting substance is brought back to its pressure, its volume and its temperature of origin ( Figure 5 ).
Le bottom line was only one transfer of body heat hot to the cold body and production of an external work; the acting substance returned in its country of origin and there was no wasting of heat.

The reversibility of the cycle is possible because there is no useless heat flow in any point of the cycle and if that occurred, the engine would not be reversible. However the reversible engine is that which gives the best possible output and Carnot to conclude, like consequence of the impossibility of the Perpetual motion, which the vapor is at least as satisfactory as any other substance acting as with a real thermodynamic advantage. It is thus not rightly that Sadi Carnot called upon the superiority of the steam engines with high pressure to support its fundamental theories

Among its posthumous writings, a manuscript entitled Search for a formula suitable to represent the horse-power of the steam , written between November 1819 and March 1827 but probably after the Reflections , was preserved. In this one it outlined the first law of thermodynamics, while trying to specify the bond between work and heat. This note was finally published in 1878, i.e. too tardily to be able to influence the development of science, by Hippolyte in a volume published in homage to his/her brother in whom it inserted a “ Biographical note on Sadi Carnot ”. It seems that he had admitted that heat is nothing more than of the horse-power (we would say energy today), proposing with ten years in advance on Julius Robert von Mayer a numerical value of the mechanical equivalent of heat with 2% near and obtained it with more scientific rigor seems.

To validate its projections, it had outlined detailed experiments, which we would say today to constant Enthalpie, and similar to those of Benjamin Thompson. But with the difference of this one, it intended to measure the provided work and produced heat, while varying the Matériaux used. In this direction, he firmly hoped to find a constant mechanical equivalent of the heat and which would have had the same value for all the experiments. It considered also measurements using of gases and the liquids to calculate the mechanical equivalent of heat.

It is difficult to know if it could have carried out these experiments in a satisfactory way. The history of thermodynamics was still long to arrive at the theory, so that one can hardly underestimate the difficulties which it should have overcome.

It would have also been necessary to convince, in particular the large body of the chemists and those which made research on the electricity: all were deeply attached to the Théorie of heating the. Lastly, it is necessary to await James Prescott Joule to see the dynamic theory of finally formulated heat. Seven years still separate its first publication (1843) and the publication from Rudolf Clausius which put in agreement the dynamic theory of heat (Joule) and the theories of Sadi Carnot. In parallel this horse-power of fire will distend the thousand-year-old bond between technique and immediate geographical environment, with the development without precedent of the Réseaux and the Flux and the geographical concentration of the equipment which becomes possible by the delocalization of this power .

In the form of assessment

Sadi Carnot discovered the two laws on which all the science of energy in spite of obstacles rests which appeared insurmountable. It gave a measurement of the exceptional power of its intuition by stating its laws when the facts were of insufficient number, their coarse precision and especially when the incipient advances in knowledge were slowed down by the erroneous theory of heating indestructible.

It has intuitively decided that the steam engine resembled to the old man Water mill, which produces energy by making fall from the water of an elevated level on a lower level, that it produces of energy while making fall from the heat of the high temperature of the boiler to that lower of the condenser. It felt that this difference in temperature was a clear phenomenon, but that the fall of heat itself was it much less and it had care in its law to make play the crucial role with the fall of temperature. We would say today that he guessed that there was a difference between the heat-form in energy and heat-falling it like water from the mill. We know that it took 40 years after its book to define the Entropie starting from the quantity of heat as being the equivalent of the water of the mill and we admire that it avoided these delicate problems and finally rejected the first the theory of the heating one. “ the death of the great men leaves as many regrets as of new hopes ”.

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