els, solar energy, geothermal energy and nuclear energy, etc. Human being can not survive and develop without fuels. The exploration and utilization of various kinds of energy resources prompt the development of social productivities of human being. And the energy consumption condition indicates the situation of productivities to some extent. Wind Water Chemical Nucle power energv energy IsSIon Heat windmi combustio transfer Waterwheel Fusion Thermal energy eaction echanical engine difference Thermal Ener Electrical energy Fig0-1 Utilization of energy resources At present, to maintain sustainable development, wind resources, solar energy and tidy energy technologies are encouraged to be used at home and abroad. However, in a very long term, the mineral fuels such as coal, crude oil and natural gases will be in domination at domestic. And the exploration of nuclear energy will be strengthened. Fig O-l tells us the energy conversion from various kinds of energies into thermal energy is a very important step before they are finally used. Therefore, it is a very important to use the thermal energy emitted by combustion of fuels or by fission or fusion of nuclear energy efficiently to achieve a sustainable utilization of energy resources There are two ways to use the thermal energy emitted by fuel combustion. One is indirect utilization, that is, to converse the thermal energy into mechanical energy or electricity through turbines and power generators. For example, equipment in steam power plants, gas-turbine, engine of rocket, internal combustion engines, etc. can be used to accomplish energy conversion. Most of thermal energy is used indirectly. Since the first industrial revolutionary aroused by the invention of steam engines, the productivities have developed greatly. Another way is using thermal energy directly For example, during the process of melting, heating, drying and fractionating, etc, thermal energy is used directly. There are many facilities, in which thermal energies are used, such as, furnaces, boilers heaters, condensers, evaporators and chillers, and so on An important issue is how to efficiently converse thermal energy into mechanical energy or electricity during indirect use of thermal energy. For instance, only 25% of thermal energy can be transformed into power in simple thermal power plants. Even in large installations, the energy transformation rate can only reach about 40%. There is still 60%-75%of thermal energy can not be used but discharged to rivers, lakes, seas and atmospheric air. This part of thermal energy which is not used effectively is called waste heat. Another example, the effectiveness of thermal energy utilization is even less in vehicles, locomotives, aircrafts and steamboats, etc. The exhaust gases from these
11 Wind Energy Water power Chemical energy Nuclear energy Geothermal energy Solar energy combustion Fusion Fission Heat transfer Mechanical Energy windmill Waterwheel Hydraulic machinery Electrical energy Temperature Difference power Magnetic Fluid power Photoelectric reaction Thermal user Fuel cell Heat Transfer heat engine Thermal Energy fuels, solar energy, geothermal energy and nuclear energy, etc. Human being can not survive and develop without fuels. The exploration and utilization of various kinds of energy resources prompt the development of social productivities of human being. And the energy consumption condition indicates the situation of productivities to some extent. Fig.0-1 Utilization of energy resources At present, to maintain sustainable development, wind resources, solar energy and tidy energy technologies are encouraged to be used at home and abroad. However, in a very long term, the mineral fuels such as coal, crude oil and natural gases will be in domination at domestic. And the exploration of nuclear energy will be strengthened. Fig.0-1 tells us the energy conversion from various kinds of energies into thermal energy is a very important step before they are finally used. Therefore, it is a very important to use the thermal energy emitted by combustion of fuels or by fission or fusion of nuclear energy efficiently to achieve a sustainable utilization of energy resources. There are two ways to use the thermal energy emitted by fuel combustion. One is indirect utilization, that is, to converse the thermal energy into mechanical energy or electricity through turbines and power generators. For example, equipment in steam power plants, gas-turbine, engine of rocket, internal combustion engines, etc. can be used to accomplish energy conversion. Most of thermal energy is used indirectly. Since the first industrial revolutionary aroused by the invention of steam engines, the productivities have developed greatly. Another way is using thermal energy directly. For example, during the process of melting, heating, drying and fractionating, etc., thermal energy is used directly. There are many facilities, in which thermal energies are used, such as, furnaces, boilers, heaters, condensers, evaporators and chillers, and so on. An important issue is how to efficiently converse thermal energy into mechanical energy or electricity during indirect use of thermal energy. For instance, only 25% of thermal energy can be transformed into power in simple thermal power plants. Even in large installations, the energy transformation rate can only reach about 40%. There is still 60%~75% of thermal energy can not be used but discharged to rivers, lakes, seas and atmospheric air. This part of thermal energy which is not used effectively is called waste heat. Another example, the effectiveness of thermal energy utilization is even less in vehicles, locomotives, aircrafts and steamboats, etc. The exhaust gases from these
equipments include a large amount of harmful substances. This has brought severe pollution on the environment. Thus, how to improve thermal efficiency of these equipments is the most important thing we should pay attention to The amount of fuels burned when thermal energy is used directly is also very huge. Thus, it is very important to save fuels. Thus, how to effectively accomplish heat transfer in heat exchangers is another key topic we are facing. This topic will be introduced in the branch of Heat Transfer Economy can not develop without the direct and indirect use of thermal energy. However, the amount of mineral fuels is limited. Thus, how to improve thermal efficiency and how to save energy are critical research topics worldwide. Therefore, it is necessary to study thermodynamic properties of substances and the rules which govern thermal energy transformation and transfer 0. 2 The studies and main Contents of Engineering Thermodynamics Statistics reveals that the amount of natural energy resources used through the step of conversion into thermal energy counts to more than 85% of the total world energy consumption. Thermal energ. is the most widely used energy o indicates that other kinds of energy resources can easily transformed into thermal energy. However, is it very easy to converse thermal energy into mechanical energy, electricity or other forms of energy at very low cost? This is a problem met in practice which is needed to be solved. Engineering thermodynamics is a branch of science which studies the rule governing the transformation between thermal energy and mechanical energy. It also explores how to use energy feasibly and efficiently Mechanical energy is the result of macroscopic motions of substances. The motion is orderly movement. However, thermal energy is the result of random motion of large amount of molecules They are different from each other in nature. The conversion from thermal energy to mechani energy is different from the conversion between other forms of energy, say, the conversion between kinetic energy and potential energy. It is found that organized energy can be conversed into disorganized energy very easily. The converse transformation is not so easy. Only part of thermal energy can be conversed into mechanical energy, while the other part can not be transformed but discharged as thermal energy to the environment. This non-equivalence among different kinds of energy indicates energy possesses the property of quantity as well as quality. The first and second laws of thermodynamics reveals the rule of energy conversion between thermal energy and mechanical energy, that is between organized and disorganized energy from these two aspects of the energy properties, respectively. They are the fundamental theory for studying thermal phenomena. It is indispensible to converse thermal energy to mechanical energy without some installations and working medium. The working medium can flow through the installations and output expansion work through volume changes to obtain work continuously. Therefore, the generally used working mediums are gaseous substances In the course of Engineering Thermodynamics, it is to study thermodynamic systems, thermal equilibrium state, thermodynamic processes, thermodynamic cycle and working medium to better the performance of heat engines, refrigerators and heat pumps and improve the thermal efficiency and energy utilization effectiveness. Therefore, the characteristics of thermodynamic processes will be studied based on the fundamental laws of thermodynamics. And thermo-physical properties of gases and fluids will be introduced as well as the law governs phase change processes, such as evaporatio and condensation. Chemical reaction processes, such as combustion, melting and resolving are involved in practice. These may concerns some basic knowledge of Chemical Thermodynamics. Thus, the following three parts will be introduced in Engineering Thermodynamics
12 equipments include a large amount of harmful substances. This has brought severe pollution on the environment. Thus, how to improve thermal efficiency of these equipments is the most important thing we should pay attention to. The amount of fuels burned when thermal energy is used directly is also very huge. Thus, it is very important to save fuels. Thus, how to effectively accomplish heat transfer in heat exchangers is another key topic we are facing. This topic will be introduced in the branch of Heat Transfer. Economy can not develop without the direct and indirect use of thermal energy. However, the amount of mineral fuels is limited. Thus, how to improve thermal efficiency and how to save energy are critical research topics worldwide. Therefore, it is necessary to study thermodynamic properties of substances and the rules which govern thermal energy transformation and transfer. 0.2 The Studies and Main Contents of Engineering Thermodynamics Statistics reveals that the amount of natural energy resources used through the step of conversion into thermal energy counts to more than 85% of the total world energy consumption. Thermal energy is the most widely used energy. It also indicates that other kinds of energy resources can easily transformed into thermal energy. However, is it very easy to converse thermal energy into mechanical energy, electricity or other forms of energy at very low cost? This is a problem met in practice which is needed to be solved. Engineering thermodynamics is a branch of science which studies the rule governing the transformation between thermal energy and mechanical energy. It also explores how to use energy feasibly and efficiently. Mechanical energy is the result of macroscopic motions of substances. The motion is orderly movement. However, thermal energy is the result of random motion of large amount of molecules. They are different from each other in nature. The conversion from thermal energy to mechanical energy is different from the conversion between other forms of energy, say, the conversion between kinetic energy and potential energy. It is found that organized energy can be conversed into disorganized energy very easily. The converse transformation is not so easy. Only part of thermal energy can be conversed into mechanical energy, while the other part can not be transformed but discharged as thermal energy to the environment. This non-equivalence among different kinds of energy indicates energy possesses the property of quantity as well as quality. The first and second laws of thermodynamics reveals the rule of energy conversion between thermal energy and mechanical energy, that is between organized and disorganized energy from these two aspects of the energy properties, respectively. They are the fundamental theory for studying thermal phenomena. It is indispensible to converse thermal energy to mechanical energy without some installations and working medium. The working medium can flow through the installations and output expansion work through volume changes to obtain work continuously. Therefore, the generally used working mediums are gaseous substances. In the course of Engineering Thermodynamics, it is to study thermodynamic systems, thermal equilibrium state, thermodynamic processes, thermodynamic cycle and working medium to better the performance of heat engines, refrigerators and heat pumps and improve the thermal efficiency and energy utilization effectiveness. Therefore, the characteristics of thermodynamic processes will be studied based on the fundamental laws of thermodynamics. And thermo-physical properties of gases and fluids will be introduced as well as the law governs phase change processes, such as evaporation and condensation. Chemical reaction processes, such as combustion, melting and resolving are involved in practice. These may concerns some basic knowledge of Chemical Thermodynamics. Thus, the following three parts will be introduced in Engineering Thermodynamics:
(1)Two fundamental laws of thermodynamics---The first law and the second law of thermodynamics (2)Thermodynamic properties of working mediums commonly used (3)Thermodynamic processes and cycles are analyzed and the ways to improve thermal efficiency are 0.3 Engineering Thermodynamics Approaches Engineering thermodynamics is a branch of fundamental science which studies the general principles of thermodynamics and their applications in engineering practice. Therefore, macroscopic thermodynamics (classical thermodynamics) methods are adopted. Classical thermodynamics concerned primarily with the macrostructure of matter. It treats substances as continuums and addresses the gross characteristics of large aggregations of molecules but not the behavior of individual molecules. Starting from the laws of thermodynamics, which are derived from some abstract concepts, large number of observations and practical summarization, it analyzes the macroscopic properties of substances and macroscopic phenomena by rigorous methods of logical reasoning. And then the conclusions are made, which are guides for practices. That is, it is to provide various schemes to use energy resources effectively, based on general principles of classical thermodynamics. The laws of thermodynamics are summarized from large amount of practices. They are very reliable and universal. However, classical thermodynamics has its limitations. It does not deep into the micro-structure of substances, for example, it can not provide the theory for specific heat and can not explain why macroscopic thermodynamic properties rise and drop lowever, in calculations and analysis based on thermodynamic theories, it needs to know detaile thermodynamic properties of related substances, such as equation of state, specific heat of substances Based on classical thermodynamic theories, it can not deduce these macroscopic properties. It needs experimental data or to takes advantage of the results of statistical thermodynamics research. The statistical approach is to derive all macroscopic properties( temperature, volume, pressure, energy entropy, etc. from the properties of moving constituent particles and the interactions between them (including quantum phenomena). The microstructure of matter is studied in kinetic theory and statistical mechanics. It can reveal the nature of thermal phenomena and explain thermodynamic theories from the viewpoint of microscopic mechanism. It can make clear the microscopic factors which determine the macroscopic properties. It plays a guidance role in theory. However, statistical thermodynamics is unavoidably based on some assumptions and simplifications. The results obtained may deviate from practical situation by somewhat Chapter 1 Basic Concepts 1.1 Thermodynamic Systemm d work chapa h and conversion. There are many Thermodynamics is the science about energy utilizatio concepts and special terminologies. We start this ter with a discussion on some basic cone such as sy stem, state, property, equilibrium, process and cycles. We al so introduce the basic properties including temperature, pressure, heat 1. 1.1 Thermodynamic System A thermodynamic system, or simply a system, is defined as a quantity of matter or a region in space chosen for study. The purpose of choosing system is to make certain what the analytic targets are
13 (1) Two fundamental laws of thermodynamics---The first law and the second law of thermodynamics； (2) Thermodynamic properties of working mediums commonly used. (3) Thermodynamic processes and cycles are analyzed and the ways to improve thermal efficiency are also explained. 0.3 Engineering Thermodynamics Approaches Engineering thermodynamics is a branch of fundamental science which studies the general principles of thermodynamics and their applications in engineering practice. Therefore, macroscopic thermodynamics (classical thermodynamics) methods are adopted. Classical thermodynamics is concerned primarily with the macrostructure of matter. It treats substances as continuums and addresses the gross characteristics of large aggregations of molecules but not the behavior of individual molecules. Starting from the laws of thermodynamics, which are derived from some abstract concepts, large number of observations and practical summarization, it analyzes the macroscopic properties of substances and macroscopic phenomena by rigorous methods of logical reasoning. And then the conclusions are made, which are guides for practices. That is, it is to provide various schemes to use energy resources effectively, based on general principles of classical thermodynamics. The laws of thermodynamics are summarized from large amount of practices. They are very reliable and universal. However, classical thermodynamics has its limitations. It does not deep into the micro-structure of substances, for example, it can not provide the theory for specific heat and can not explain why macroscopic thermodynamic properties rise and drop. However, in calculations and analysis based on thermodynamic theories, it needs to know detailed thermodynamic properties of related substances, such as equation of state, specific heat of substances. Based on classical thermodynamic theories, it can not deduce these macroscopic properties. It needs experimental data or to takes advantage of the results of statistical thermodynamics research. The statistical approach is to derive all macroscopic properties (temperature, volume, pressure, energy, entropy, etc.) from the properties of moving constituent particles and the interactions between them (including quantum phenomena). The microstructure of matter is studied in kinetic theory and statistical mechanics. It can reveal the nature of thermal phenomena and explain thermodynamic theories from the viewpoint of microscopic mechanism. It can make clear the microscopic factors which determine the macroscopic properties. It plays a guidance role in theory. However, statistical thermodynamics is unavoidably based on some assumptions and simplifications. The results obtained may deviate from practical situation by somewhat. Chapter 1 Basic Concepts Thermodynamics is the science about energy utilization and conversion. There are many basic concepts and special terminologies. We start this chapter with a discussion on some basic concepts such as system, state, property, equilibrium, process and cycles. We also introduce the basic properties including temperature, pressure, heat and work. 1.1 Thermodynamic System 1.1.1 Thermodynamic System A thermodynamic system, or simply a system, is defined as a quantity of matter or a region in space chosen for study. The purpose of choosing system is to make certain what the analytic targets are
This means that the system can be an object, a set of objects, or part of a object, or a given region The mass or region outside the system is called the surroundings. The surface that separates the system from its surroundings is called the boundary. Note that the boundary is the contact surface shared by both the system and its surroundings thermodynamic system and the boundary Considering a piston-cylinder device shown in Fig. 1-1, there is a gas of fixed mass enclosed in the cylinder. As it is heated, the piston may move. There is no mass crossing the boundary. This means that the system works with a fixed amount Figure 1-1 Closed system volume is variable. That is, the boundary of a system can be fixed Fig 1-2 shows a water heater. We can choose the volume er occupied by the heater for study. The inner surfaces of the water heater form the real part of the boundary. And the entrance and exit areas form the imaginary part, since there are no physical surfaces there. The fluid enters the system from section 1-1, and Figure 1-2 Open system exits from 2-2. And the mass in the system may be variable. The boundary of a system can be physical In general, any arbitrary region in space can be selected as a control volume. There are no concrete rules for the selection of control volumes, but the proper choice certainly makes the analysis much easier. After the system is properly chosen, we will begin to study the interactions between the system and its surroundings, including the energy and mass interactions 1.1.2 Categories of Systems Generally the system is al ways in interactions with its surroundings. Energy and mass can cross the boundaries in the form of heat, work or mass. Based on the different interactions, systems can classified as following Closed system: A closed system consists of a fixed amount of mass, and mass cannot cross its boundary. And it is also known as a control mass. The volume of a closed system does not have to be fixed. Everything outside the boundary is the surroundings. There is no mass can enter or leave the system. But energy, in the form of heat or work, can cross the boundary Open system: An open sy stem is a properly selected region in space. Mass flowing through such device as a compressor, turbine, or nozzle is encountered in engineering These devices are also known as control volumes. There is mass flowing in and out of the system. The boundaries of a control olume are called a control surface, and they can be real or imaginary. Both mass and energy can cross the boundary of a control volume Adiabatic system: If there is no heat entering and exiting a system, the system is called adiabatic system. It is an idealized system. In an engineering analysis, if the heat transferred compared with other forms of energy exchange is sufficiently small, it can be regard as an adiabatic system. Such as for a steam turbine, the heat loss from it is far less than its work output. Thus the heat emission can be ignored and the system can be deemed as an adiabatic system Isolated system: If there are no any interactions between a system and its surroundings, the system is called isolated sy stem. No mass and energy is allowed to cross the boundary. An isolated system
14 Figure 1-1 Closed system Figure 1-2 Open system This means that the system can be an object, a set of objects, or part of a object, or a given region. The mass or region outside the system is called the surroundings. The surface that separates the system from its surroundings is called the boundary. Note that the boundary is the contact surface shared by both the system and itssurroundings. There are several examples to illustrate the features of thermodynamic system and the boundary. Considering a piston-cylinder device shown in Fig. 1-1, there is a gas of fixed mass enclosed in the cylinder. As it is heated, the piston may move. There is no mass crossing the boundary. This means that the system works with a fixed amount of mass. We choose the fixed mass in space for study. But the volume is variable. That is, the boundary of a system can be fixed or movable. Fig.1-2 shows a water heater. We can choose the volume occupied by the heater for study. The inner surfaces of the water heater form the real part of the boundary. And the entrance and exit areas form the imaginary part, since there are no physical surfaces there. The fluid enters the system from section 1-1, and exits from 2-2. And the mass in the system may be variable. The boundary of a system can be physical or imaginary. In general, any arbitrary region in space can be selected as a control volume. There are no concrete rules for the selection of control volumes, but the proper choice certainly makes the analysis much easier. After the system is properly chosen, we will begin to study the interactions between the system and its surroundings, including the energy and mass interactions. 1.1.2 Categories of Systems Generally the system is always in interactions with its surroundings. Energy and mass can cross the boundaries in the form of heat, work or mass. Based on the different interactions, systems can be classified as following. Closed system：A closed system consists of a fixed amount of mass, and mass cannot cross its boundary. And it is also known as a control mass. The volume of a closed system does not have to be fixed. Everything outside the boundary is the surroundings. There is no mass can enter or leave the system. But energy, in the form of heat or work, can cross the boundary. Open system: An open system is a properly selected region in space. Mass flowing through such device as a compressor, turbine, or nozzle is encountered in engineering. These devices are also known as control volumes. There is mass flowing in and out of the system. The boundaries of a control volume are called a control surface, and they can be real or imaginary. Both mass and energy can cross the boundary of a control volume. Adiabatic system：If there is no heat entering and exiting a system, the system is called adiabatic system. It is an idealized system. In an engineering analysis, if the heat transferred compared with other forms of energy exchange is sufficiently small, it can be regard as an adiabatic system. Such as for a steam turbine, the heat loss from it is far less than its work output. Thus the heat emission can be ignored and the system can be deemed as an adiabatic system. Isolated system: If there are no any interactions between a system and its surroundings, the system is called isolated system. No mass and energy is allowed to cross the boundary. An isolated system
must be a closed system. Apparently, it is an idealized system too. Sometime for the convenience of solving problems, we choose all objects in the system and surroundings as a new system. This system is an isolated system. Within the system, each subsystem can have interactions with each other, but this new system has no interactions with its surrounding n engineering analysis, the system under study must be defined carefully. In most cases, the system investigated is quite simple and obvious. It may seem like a tedious and unnecessary task to define the system. In other cases, however, the system under study may be rather involved, and a proper choice of the system may greatly simplify the analysis The internal condition and substances in a system is closely related to the interaction between the system and it surroundings. Systems can also be categorized in terms of its internal conditions, such as system with single substance, system with multiple kinds of substances, even system and uneven system, or single phase system and multi-phase systems, and so on 1.1.3 Working Fluid Energy transformations are al ways fulfilled by some substances. The substance is called"working fluid"or"working medium". For example in combustion engines, heat is transformed into work by virtual of gas expansion and the working fluid is gas. In steam power plant, steam(water) is the In general, all matters can be working fluids. And heat is al ways transformed into work by means of expansion of the working fluid. Because gas(or vapor)can change state sensitively and rapidly, the working fluids involved in practical applications are mainly gases(or vapors) As working fluid has an immediate impact on energy conversion, the characteristics of the working fluid are also important contents to study in thermodynam 1.2 Thermodynamic states and Basic properties 1. 2.1 States and States Properties The thermodynamic state is the condition of a system. a system not undergoing any change gives a set of properties that completely describes the condition of that system. a property is a characteristic that helps to describe the state of a system. At this point, all the properties can be measured or calculated throughout the entire system. Some familiar properties include pressure p, temperatureT, volume The state of a system is described by its properties. For example, at present indoor air temperature is 20C, and outdoor air temperature is 12C. That is, the air inside and outside are in different states. If the state is specified, all properties that describe the state are also identified State properties are point functions. At a given state, all the properties of a system have fixed alues. This is an important basic characteristic of state properties. They are determined by the state only, but not related to how a system reaches this state. During any change from the same initial state I to final state 2, the changes in a certain state property are the same, as shown in Fig. 1-3. It is only related to the state I and 2, but △K=3m3,w=8 regardless of the path followed. Namely, A n-3 m A,2=x2-x=∫d processes, and returns to its initial state at the end of the process total change in its state properties is zero Figure 1-3 State 15
15 Figure 1-3 State must be a closed system. Apparently, it is an idealized system too. Sometime for the convenience of solving problems, we choose all objects in the system and surroundings as a new system. This system is an isolated system. Within the system, each subsystem can have interactions with each other, but this new system has no interactions with its surrounding. In engineering analysis, the system under study must be defined carefully. In most cases, the system investigated is quite simple and obvious. It may seem like a tedious and unnecessary task to define the system. In other cases, however, the system under study may be rather involved, and a proper choice of the system may greatly simplify the analysis. The internal condition and substances in a system is closely related to the interaction between the system and it surroundings. Systems can also be categorized in terms of its internal conditions, such as system with single substance, system with multiple kinds of substances, even system and uneven system, or single phase system and multi-phase systems, and so on. 1.1.3 Working Fluid Energy transformations are always fulfilled by some substances. The substance is called “working fluid” or “working medium”. For example in combustion engines, heat is transformed into work by virtual of gas expansion and the working fluid is gas. In steam power plant, steam (water) is the working fluid. In general, all matters can be working fluids. And heat is always transformed into work by means of expansion of the working fluid. Because gas (or vapor) can change state sensitively and rapidly, the working fluids involved in practical applications are mainly gases (or vapors). As working fluid has an immediate impact on energy conversion, the characteristics of the working fluid are also important contents to study in thermodynamics. 1.2 Thermodynamic States and Basic Properties 1.2.1 States and States Properties The thermodynamic state is the condition of a system. A system not undergoing any change gives a set of properties that completely describes the condition of that system. A property is a characteristic that helps to describe the state of a system. At this point, all the properties can be measured or calculated throughout the entire system. Some familiar properties include pressure p , temperature T , volume V . The state of a system is described by its properties. For example, at present indoor air temperature is 20℃, and outdoor air temperature is 12℃. That is, the air inside and outside are in different states. If the state is specified, all properties that describe the state are also identified. State properties are point functions. At a given state, all the properties of a system have fixed values. This is an important basic characteristic of state properties. They are determined by the state only, but not related to how a system reaches this state. During any change from the same initial state 1 to final state 2, the changes in a certain state property are the same, as shown in Fig.1-3. It is only related to the state 1 and 2, but regardless of the path followed. Namely, 2 1 2 2 1 1 = − = x x x x → d When a thermodynamic system goes through a series of processes, and returns to its initial state at the end of the process, the total change in its state properties is zero: