General Introduction and the Concept of Finite Time Thermodynamics
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Thermodynamics is an important branch of Applied Thermal Science and Engineering in which the effects of heat and mass transfer, transformation of energy, etc. are studied. It is based on two basic laws, i.e. the first law and second law of thermodynamics. The first law of thermodynamics is one of the most fundamental laws and is of special importance for the energy conversion processes and also called as the ‘Law of Conservation of Energy’. According to this law, energy is always conserved, neither can it be produced nor it can be destroyed; however, it can be converted from one form to another. All the energy that goes into the system comes out somewhere, in some form or the other which is true for all energy conversion systems. Thus, the first law of thermodynamics can be used in the form of energy conservation equation to solve the problem of various devices like heat engines, refrigerators, airconditioners, heat pumps, and other energy conversion systems. However, it tells nothing about how much heat can be converted into useful work and also it does not place restrictions on the conversion of heat into work and vice versa. Thus, as far as the first law of thermodynamics is concerned, all the heat transferred from a heat source to a heat engine could conceivably be converted into useful work, which is not true as shown by the experiments. It is also impossible to predict from the first law of thermodynamics whether a process is physically possible or not. Until now it has been assumed that energy change in thermodynamics can proceed in either direction, which is not true.