Name Sadi Carnot often sounds in different classrooms of our university. "The ideal Carnot engine", "Carnot cycle", "Carnot's principle", "Carnot's theorem" ... And when you consider that he was an engineer and graduated from the Ecole Polytechnique, of course, it would be appropriate to be noted in the newspaper "Kiev Polytechnic "210th anniversary of his birth, turned this year.

Nicolas Léonard Sadi Carnot was born June 1, 1796 in a family of Lazare Carnot (1753-1823) - one of the most prominent political figures of the French Revolution. In different years Lazare Carnot was a member of the Legislative Assembly, of the Convention, the Committee of Public Safety, the director, and he was known as the organizer of victory decisive contribution to the revolutionary armies in 1793.

Lazare Carnot was also an outstanding scientist. He has left a legacy in different theoretical sciences - Applied Mechanics ("Study of machines in general", 1783), mathematical analysis ("Reflections on the metaphysics of the infinitesimal calculus", 1797). He was one of the founders of projective geometry. In 1810 he published a three-volume work on the fortifications "On defense of fortresses." In a year when his son Sadi was born, Lazare Carnot was elected a member of the Paris Academy of Sciences.

Life Sadi Carnot proceeded in a quite different historical period than the life of his father, and was not rich in bright events. And a little of news of him reached us. It is known that in the years 1812-1814 Sadi Carnot studied at the famous Ecole Polytechnique, then in the School of Engineering in the city Metz, and in 1816 he was assigned to the Army Corps of Engineers. In 1819 after passing the relevant examinations he won the competition and was moved to the Corps headquarters in Paris. He continued his studies, attended lectures at the Sorbonne, the College de France, the Conservatory of Arts and Crafts. In the Conservatory Carnot met with N.Kleman – the physicist who investigated the properties of gases, and then became interested in the problem of improving the steam engines. In 1824 he published his only job - memoir, "Reflections on the driving force of fire and machines, able to develop this power." In 1828 Carnot left the army and went on their own to do science. August 24, 1832, at 36 years of age, Sadi Carnot died of cholera. His stuff was, by law, burned. It was miraculously survived a notebook, which was saved by his brother Hippolyte.

The scientific legacy of Sadi Carnot cannot compare with the scientific legacy of his father. But to influence the further development of science ... Today Lazare Carnot is remembered, perhaps, only by mechanics and only when studying the impact theory (there Carnot's theorem about the lost kinetic energy in an inelastic collision). But the ideas of Sadi Carnot are known worldwide. Although they were not recognized immediately.

For a long time, "Reflections" of Carnot were ignored by physicists. Only ten years after its publication, and two years after the author's death, another Frenchman - B.Klapeyron - repeated considerations of Carnot, follow the steps according to the calculations and processes depicted in the diagram. Three years later, an article Clapeyron was translated and published in England. After another nine years, the article Clapeyron was published by the German physicist and publisher I.H.Poggendorf in his "Annals of physics and chemistry." And only after that - 22 years after the publication of the memoir - Carnot ideas became the basis of research R. Clausius and V.Tomson. They created on this basis the second law of thermodynamics. A memoir of Carnot became the reference point for the classical thermodynamics.

Carnot’s memoir is considered to be a classic. Comprehensive review of the issues, discussion of related issues, the sequence of presentation, as well as the beautiful language in which it was written - it is interesting to read today. And yet - when you read, you feel that the author - well-educated and erudite engineer who was interested in the machines, and the purpose of theoretical research is to solve practical problems - improvement of steam (and wider - thermal) machines.

"No one doubts that the heat may be the cause of motion (mechanical – V.I.) that it has a large driving force: steam engines, now very common, this is a clear proof" – this way it begins his work.

He further describes the action of heat, "it is the excitement of the atmosphere, increasing clouds, falling rain and other precipitation causes flow streams of water on the surface of the globe, a small part of which a person was able to use to their advantage, and finally earthquakes and volcanic eruptions are also the cause of heat.

Of these huge reservoirs, we can provide the driving force necessary for our needs; nature, everywhere providing combustible material, allowed us to always and everywhere to get heat and momentum that accompanies it. To develop this power and use it for our needs - such is a goal of heat engines. "

Carnot characterizes the value of thermal machines for various industries, lists of their application and expressed the opinion that once these machines become universal, getting an advantage over the power of animals with falling water and wind engines.

He further notes that the theory of heat engines is poorly developed.

"It is often raised the question: driving force of heat is infinite or limited (by Carnot, the driving force is the quantity of work – V.I.), is there a limit for the possible improvements, the border, the nature of things interfere to cross or otherwise, - or, alternatively, is there an endless improvement? Also there was and is the search for the agent better than steam, the driving force for the development of a fire, or prevents, for example, atmospheric air advantages in this respect. We set ourselves the task to expose here these questions to careful consideration. "

Carnot notes: "The phenomenon of getting movement from the heat was not considered sufficiently from the general point of view. It was investigated only in machines, nature and mode of action which did not allow to take full development to which it is able to ...

To consider the principle of obtaining the movement of heat in its entirety, it is necessary to study it independently of any mechanism, any specific agent; it is necessary to carry out the arguments applicable not only to the steam engines, but also to all conceivable heat engines, whatever substance was used in them. "

Such an approach of Carnot to solve the problem was praised by the great thinker Friedrich Engels, whose works criticisms of the conventional ways of thinking among physicists are much more common than positive evaluations.

Carnot writes: "Getting movement in steam engines is always accompanied by one circumstance to which we should pay attention. This circumstance is the restoration of caloric balance, that is, the transition the heat from the body with a higher temperature, to another, where it is below .. . The appearance of the driving force in steam engines is going not due to loss of the heat, but due to transition from hot to cold. There is a restoration of its balance - balance, which was initiated some reason, the chemical action as burning, or something else. We see that this principle applies to all vehicles powered by heat.

According to this principle, it is not enough to create the heat to cause a driving force: you still get the cold; without it the heat would be unnecessary. "

These provisions are the essence of the theory of Carnot, which took place on the basis of further development of thermodynamics.

Next Carnot proves that the driving force of the heat does not depend on the nature of the working fluid, and is determined only by the temperature of bodies, between which the transition of heat occurs. He comes from the impossibility of perpetual motion, that is, getting a job out of nothing. It was quite a bold move. Although the Paris Academy of Sciences recognized the impossibility of mechanical perpetual motion machines in 1785, but, as Max Planck noted, Carnot first extended out the impossibility of perpetual motion on non-mechanical processes.

Carnot addresses many issues related to the heat engine. In particular, referring to the possibility of using as the working medium in heat engines of liquids and solids, Carnot draw correct conclusions about their unsuitability, justifying this conclusion a small change in the volume of these bodies with the temperature change.

For engines which use gases, Carnot formulates the following principles of economy: temperature of the working fluid must first be as high as possible, cooling - at the lowest possible temperature. Transition from high to low temperature should occur only when the expansion of the working body. One should avoid body contact with different temperatures.

These principles are used also today.

Criminal reviews also the machines in which hot air is used. He describes their advantages over steam engines in the field of high pressure, as well as expresses the idea of heat recovery, which is very relevant today. There is an interesting observation about internal combustion engines. He knew Niepce experiments that suggested the engine had to work from the combustion of the powder in the cylinder.

At the end of the book Criminal notes that, in practice, one should take into account not only fuel economy, but also the reliability of the machine, durability, maintenance costs, and others.

Although an ideal heat engine can not be created, and there are no heat engines, which use the Carnot cycle, the ideal Carnot engine has been widely used in the theory - in most sections of thermodynamics. Actually, as befits to the ideal car. It is necessary to imagine that the working fluid in the car Carnot is a substance or a thermodynamic system in equilibrium (gas, liquid, saturated steam, a mixture of reacting gases, electromagnetic radiation, or anything else). Then one need to perform the appropriate calculations, based on the fact that the thermal efficiency of this machine is the same as the machine, which uses an ideal gas - and theoretically can bring a lot of laws and equations - Clausius-Clapeyron equation, the mass action law, Stefan-Boltzmann law, and others.

The memoir of Carnot is rightly called a classic. A classic - it is not just a product that does not age with time, but the one in which time discovers new aspects, new content, that was long time remained outside the field of view of researchers.

At the end of the XIX century, when classical thermodynamics received classical form, when questions which interested Sadi Carnot, seemed to have been completely resolved, V.Ostvald publishing the work of Carnot in its series Ostvald's Klassiker, drew attention to the fact that in definition of the heat Carnot used two terms - chaleur and calorique - «heat" and "caloric". and noted that speaking about the origin of the driving force of heat Carnot writes about the transition from the body Caloric more heated to a less heated body.

Later known at the time English scientist N.L.Kalendar claimed that entropy - is another name for Caloric, described in the Carnot work. This view was criticized O.O. Radtsig. But later a number of other authors - I.N.Brensted, La Mer, L.Brillyuen - again claimed that calorique (Caloric) should be read as "entropy". The grounds for this view are: Carnot cycle in the coordinates of entropy - the temperature has the same form as in the coordinates Caloric - temperature. A well-known expert in the field of thermodynamics professor O.A.Guhman expressed the opinion that Carnot felt the need to share complex concept amount of heat on two values - a quantitative measure of the impact of chaleur and coordinate state calorique. Corresponding Member of the Academy of Sciences of the Byelorussian SSR A.Y.Veynik more than forty years ago, created a new system of classical thermodynamics, which refused to entropy, replacing it with the value of the thermal charge - analog electric charge. He expressed the opinion that the thermal charge could be called caloric, if before that date do not have such a negative attitude. That is, in fact he made an attempt to return to the ideas of Carnot. Debate over how to treat Caloric that appears in the work of Carnot, has not ended yet.

Thus, today the product of Sadi Carnot not only serves as the basis of modern theories in different sections of thermodynamics, but remains a source of complex theoretical problems. One can express confidence that no matter how the science and technology will develop, "Reflections on the driving force of fire" for a long time do not lose their scientific value and relevance.

Author: V.Ignatovich, Ph.D.