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1、Part 1 Thermodynamics and Heat TransferThis unit introduces the basic and elementary knowledge of thermodynamics and heat transfer. After learning, you will be able to understand: l The basic concepts and terminology in thermodynamics and heat transfer l The three ways of thermal transmission l The
2、composition of thermal systems l The thermodynamic cycle principleReturn to contentsPart 1 Thermodynamics and Heat TransferText 1 Thermodynamic SystemText 2 General Characteristics of Heat TransferText 3 ConductionText 4 ConvectionReturn to contentsText 1 Thermodynamic System l In the thermal engine
3、ering, the studied objects normally are isolated from one another and then we try to analysis the change and interaction, the studied objects isolated is named thermodynamic system.1 l The boundary of a system can be either real or imaginary, and either fixed or movable. If the gas in a cylinder is
4、the studying object, then it is the thermodynamic system. 2 l There may be many objects in an engineering problem. The solution of a system is dependent on which objects are under consideration. In a thermodynamics system, we can do it either by placing an imaginary envelope around the objects under
5、 consideration or by using an actual envelope if it exists. 3contentsUnit 1New wordsl For example, when dealing with a gas in the cylinder where the boundaries are located on the outside of the cylinder, 4 the system includes both the cylinder and its contained gas. On the other hand, when the bound
6、aries are placed at the inner face of the cylinder, the system consists solely of the gas itself. So it is very important and essential for us to specify the boundaries of the system carefully. 5 l The boundaries of a closed system may be either rigid or may expand or contract, 6 but its mass will n
7、ot change. When the energy crossing the boundaries of a closed system is zero, the system may be treated as an isolated system.l Based on the difference of the characteristic of the systems, the different systems are named. (1) When the boundaries of a system would not exchange with the surroundings
8、, then can said that it is a closed system. However, it may exchange energy in any form of heat or work with the surroundings.(2) Conversely, if there are any matter exchange between the system and the surroundings, then it is an open system. The quantity of the matter in an open system may be eithe
9、r variable or constant. The boundaries of an open system are so placed that their location does not change with time. Thus, the boundaries enclose a fixed volume, commonly known as the control volume. l Sometimes a system may be a closed system at one moment and an open one the next. For example, co
10、nsider we would study a cylinder of an internal combustion engine, when the valves close, the system is a closed system. And when either or both of the valves open, the system will become an open system.l In most cases, a studied object would be a large and very complex system. We can break down it
11、into a lot of component parts and analyze every component parts. Then the performance of the entire system can be determined by the summation of the performance of the individual component systems. 7 l For example, consider the liquid-vapor part of a steam power plant as a total system. This closed
12、system contains the steam generator, the steam turbine, the steam condenser, the feed-water pumps, and the feed -water heaters. All of these units may be considered separately by throwing a boundary around them. Since a fluid enters and leaves each of these smaller systems, each one is an open syste
13、m and must be analyzed .boundaryn.边界, 分界线consideration n.体谅,考虑,需要考虑的事项,报酬cylinder n.圆筒, 圆柱体, 汽缸, 柱面envelopen.信封,封袋,天包层,数包迹,生包膜imaginarya.假想的,想象的,虚构的Solely ad. 独自地, 单独地solutionn.解答,解决办法,溶解,溶液,解决方案be isolated from被与隔绝either or或（者）或（者）for example 例如be dependent on依靠, 依赖 New Words and ExpressionsText 2l
14、 Technical Termsl a steam power plant蒸汽发电厂l an internal combustion engine 内燃机l the feed-water heater给水加热器l the feed-water pump(给水)泵l the steam condenser蒸汽冷凝器l the steam generator蒸汽发生器（锅炉）l the steam turbine蒸汽轮机 Exercise(1)l Answer the following questions according to the text. (1) How do we usually
15、do when studying a thermal engineering? (2) How can be the boundary of a system? (3) What is the solution of a system dependent on? (4) Based on the difference of the characteristic of the systems, how many the different systems are named? (5) How do we usually do when a studied object is a large an
16、d very complex system? (6) What is the boundary of a studying object?Exercise(2)l Decide whether the following statements is true or false according to the text. (1) In the thermal engineering, the studied objects normally are isolated from one another and then try to analysis the change and interaction. (2) The boundary of a system can be either real or imaginary, but it can not be either fixed
