tailieunhanh - Chương 1: Engineering Thermodynamics

Our modern technological society is based largely on the replacement of human and animal labor by animate, power-producing machinery. Examples of such machinery are steam power plants that generate electricity, locomotives that pull freight and passenger trains, and internal combustion engines that power automobiles. In each of these examples, working fluids such as steam and gases are generated by combustion of a fuel-air mixture and then are caused to act upon mechanical devices to produce power. Predictions of how much energy can be obtained from the working fluid and how well the extraction of energy from the working fluid can. | NHA TRANG UNIVERSITY Faculty of Mechanical Engineering Assoc. Prof. Nguyễn Văn Nhận Engineering Thermodynamics Textbook Compiled for Students at the Faculty of Mechanical Engineering NHA TRANG - 2008 - 2 - Our modern technological society is based largely on the replacement of human and animal labor by animate power-producing machinery. Examples of such machinery are steam power plants that generate electricity locomotives that pull freight and passenger trains and internal combustion engines that power automobiles. In each of these examples working fluids such as steam and gases are generated by combustion of a fuel-air mixture and then are caused to act upon mechanical devices to produce power. Predictions of how much energy can be obtained from the working fluid and how well the extraction of energy from the working fluid can be accomplished are the province of an area of engineering called thermodynamics. Thermodynamics is based on two experimentally observed laws. The first is the law of conservation of energy familiar to the student from the study of classical mechanics. Whereas in mechanics only potential and kinetic energies are involved in thermodynamics the law of conservation of energy is extended to include thermal and other forms of energy. When an energy transformation occurs the same total energy must be present after the transformation as before in other words according to the first law all the different types of energy must be accounted for and balanced out when a transformation occurs. For example in an internal combustion engine a specific quantity of thermal energy is released due to the combustion of gasoline in the engine cylinders. Some of this energy goes out the tailpipe as heated exhaust gases and is lost some is converted to useful work in moving the car and some is dissipated to the air via the cooling system. Whereas the distribution of these various types of energy is clearly of important to the engineer who wants to obtain as much .