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Logical and mathematical aspects of the basic concepts of thermodynamics are considered. Discussion of the fundamentals of a theory can bear fruit only if led with competent enough people.
Principles of control thermodynamics
The author starts with a premise that the Reader embarking on a study of this book has a general knowledge of this theory within the program of the course of General physics offered at a Physical Faculty of a University . The major motivation that has prompted the Author to write this book was the inconsistency of the second law of thermodynamics as a law of Nature .
The logical structure of thermodynamics is often compared to that of geometry in the consistent and strict way it emerges from the two postulates laws of thermodynamics. The conclusions drawn in thermodynamics found convincing support in the truly immense variety of observations and deductions, so that one could hardly find today a physicist, chemist or biologist who would question the validity of thermodynamics.
Rather than being only a subject of scientific studies, thermal processes truly pervade all aspects of our life. Thermodynamics is generally considered to be a scientific basis underpinning heatpower engineering, and conversion of heat to work, the main problem facing thermodynamics. Conversion of heat to work by various heat engines had been enjoying worldwide industrial application long before thermodynamics was formulated.
PRINCIPLES OF GENERAL THERMODYNAMICS - George N. Hatsopoulos, Joseph H. Keenan - Google книги
From the very beginning, the major motivation underlying thermodynamics had been a search for the most efficient methods that could be applied to this conversion. But it is thermodynamics that grew to become an insurmountable monolithic wall separating the truly inexhaustible ocean of thermal energy surrounding us from the possibility of its use in technology. Abandoning the second postulate as a universal law of Nature would at first glance seem to imply a revision of all already well-established conceptions about the world surrounding us.
In actual fact, however, the situation is not that tragic.
Indeed, the overwhelming majority if not all of the processes converting heat to work which were considered in thermodynamics relate to single-parameter systems. For these processes, the second law certainly does hold. General differential equations are derived for the time history of a thermodynamic system undergoing irreversible transformations. This is done by using Onsager's principle, and introducing generalized concepts of free energy and thermodynamic potentials.
From these equations it is shown that the instantaneous evolution of the system satisfies a principle of minimum rate of entropy production.
It is also shown how Prigogine's theorem for the stationary state fits into the present theory. Another variational principle is established for the case where certain variables are ignored in analogy with the methods of virtual work in mechanics. This principle which applies to complex physical-chemical systems is developed more specifically for viscoelastic phenomena, and as an example the differential equations for the deflection of a viscoelastic plate is derived.
Abstract Authors References. Abstract General differential equations are derived for the time history of a thermodynamic system undergoing irreversible transformations. When gas is heated, it expands; however, when that gas is confined, it increases in pressure.
If the bottom wall of the confinement chamber is the top of a movable piston, this pressure exerts a force on the surface of the piston causing it to move downward. There are numerous variations on the basic heat engine. The water is converted to steam, and the pressure is then used to drive a piston that converts heat energy to mechanical energy. Refrigerators and heat pumps are heat engines that convert mechanical energy to heat.
Most of these fall into the category of closed systems. When a gas is compressed, its temperature increases.
This hot gas can then transfer heat to its surrounding environment. Then, when the compressed gas is allowed to expand, its temperature becomes colder than it was before it was compressed because some of its heat energy was removed during the hot cycle. This cold gas can then absorb heat energy from its environment. This is the working principal behind an air conditioner. The working fluid is transferred outdoors by a mechanical pump where it is heated by compression. Next, it transfers that heat to the outdoor environment, usually through an air-cooled heat exchanger.
Then, it is brought back indoors, where it is allowed to expand and cool so it can absorb heat from the indoor air through another heat exchanger. A heat pump is simply an air conditioner run in reverse.