Fluids such as air and water exert pressure,introduced in Sec.1.6.Jeffrey Warrington/Alamy ENGINEERING CONTEXT Although aspects of thermodynamics have been studied since ancient times,the formal study of thermodynamics began in the early nineteenth century through consideration of the capacity of hot objects to produce work.Today the scope is much larger.Thermodynamics now provides essential concepts and methods for addressing critical twenty-first-century issues,such as using fossil fuels more effectively,fostering renewable energy technologies,and developing more fuel-efficient means of trans- portation.Also critical are the related issues of greenhouse gas emissions and air and water pollution. Thermodynamics is both a branch of science and an engineering specialty.The scientist is normally interested in gaining a fundamental understanding of the physical and chemical behavior of fixed quantities of matter at rest and uses the principles of thermodynamics to relate the properties of matter.Engineers are generally interested in study- ing systems and how they interact with their surroundings.To facilitate this,thermodynamics has been extended to the study of systems through which matter flows,including bioengineering and biomedical systems. The objective of this chapter is to introduce you to some of the fundamental concepts and definitions that are used in our study of engineering thermodynamics.In most instances this introduction is brief,and further elaboration is provided in subsequent chapters. 2
2 ENGINEERING CONTEXT Although aspects of thermodynamics have been studied since ancient times, the formal study of thermodynamics began in the early nineteenth century through consideration of the capacity of hot objects to produce work. Today the scope is much larger. Thermodynamics now provides essential concepts and methods for addressing critical twenty-first-century issues, such as using fossil fuels more effectively, fostering renewable energy technologies, and developing more fuel-efficient means of transportation. Also critical are the related issues of greenhouse gas emissions and air and water pollution. Thermodynamics is both a branch of science and an engineering specialty. The scientist is normally interested in gaining a fundamental understanding of the physical and chemical behavior of fixed quantities of matter at rest and uses the principles of thermodynamics to relate the properties of matter. Engineers are generally interested in studying systems and how they interact with their surroundings. To facilitate this, thermodynamics has been extended to the study of systems through which matter flows, including bioengineering and biomedical systems. The objective of this chapter is to introduce you to some of the fundamental concepts and definitions that are used in our study of engineering thermodynamics. In most instances this introduction is brief, and further elaboration is provided in subsequent chapters. Fluids such as air and water exert pressure, introduced in Sec. 1.6. © Jeffrey Warrington/Alamy c01GettingStarted.indd Page 2 5/26/10 7:39:26 PM user-s146 /Users/user-s146/Desktop/Merry_X-Mas/New
Getting Started Introductory Concepts and Definitions LEARNING OUTCOMES When you complete your study of this chapter,you will be able to... demonstrate understanding of several fundamental concepts used throughout the book... including closed system,control volume,boundary and surroundings,property,state, process,the distinction between extensive and intensive properties,and equilibrium. apply SI and English Engineering units,including units for specific volume,pressure,and temperature. work with the Kelvin,Rankine,Celsius,and Fahrenheit temperature scales. apply the problem-solving methodology used in this book. 3
Getting Started Introductory Concepts and Definitions 1 When you complete your study of this chapter, you will be able to... c demonstrate understanding of several fundamental concepts used throughout the book . . . including closed system, control volume, boundary and surroundings, property, state, process, the distinction between extensive and intensive properties, and equilibrium. c apply SI and English Engineering units, including units for specific volume, pressure, and temperature. c work with the Kelvin, Rankine, Celsius, and Fahrenheit temperature scales. c apply the problem-solving methodology used in this book. LEARNING OUTCOMES 3 c01GettingStarted.indd Page 3 5/26/10 7:39:39 PM user-s146 /Users/user-s146/Desktop/Merry_X-Mas/New
Chapter 1 Getting Started Using Thermodynamics Engineers use principles drawn from thermodynamics and other engineering sciences, including fluid mechanics and heat and mass transfer,to analyze and design things intended to meet human needs.Throughout the twentieth century,engineering applica- tions of thermodynamics helped pave the way for significant improvements in our quality of life with advances in major areas such as surface transportation,air travel,space flight,electricity generation and transmission,building heating and cooling,and improved medical practices.The wide realm of these applications is suggested by Table 1.1. In the twenty-first century,engineers will create the technology needed to achieve a sustainable future.Thermodynamics will continue to advance human well-being by address- ing looming societal challenges owing to declining supplies of energy resources:oil,natural gas,coal,and fissionable material;effects of global climate change;and burgeoning popula- tion.Life in the United States is expected to change in several important respects by mid- century.In the area of power use,for example,electricity will play an even greater role than today.Table 1.2 provides predictions of other changes experts say will be observed. If this vision of mid-century life is correct,it will be necessary to evolve quickly from our present energy posture.As was the case in the twentieth century,thermodynamics will contribute significantly to meeting the challenges of the twenty-first century.includ- ing using fossil fuels more effectively,advancing renewable energy technologies,and developing more energy-efficient transportation systems,buildings,and industrial prac- tices.Thermodynamics also will play a role in mitigating global climate change,air pollution,and water pollution.Applications will be observed in bioengineering,bio- medical systems,and the deployment of nanotechnology.This book provides the tools needed by specialists working in all such fields.For nonspecialists,the book provides background for making decisions about technology related to thermodynamics-on the job,as informed citizens,and as government leaders and policy makers. 1.2 Defining Systems The key initial step in any engineering analysis is to describe precisely what is being stud- ied.In mechanics,if the motion of a body is to be determined,normally the first step is to define a free body and identify all the forces exerted on it by other bodies.Newton's second law of motion is then applied.In thermodynamics the term system is used to iden- tify the subject of the analysis.Once the system is defined and the relevant interactions with other systems are identified,one or more physical laws or relations are applied. system The system is whatever we want to study.It may be as simple as a free body or as complex as an entire chemical refinery.We may want to study a quantity of matter contained within a closed,rigid-walled tank,or we may want to consider something such as a pipeline through which natural gas flows.The composition of the matter inside the system may be fixed or may be changing through chemical or nuclear reac- tions.The shape or volume of the system being analyzed is not necessarily constant, as when a gas in a cylinder is compressed by a piston or a balloon is inflated. surroundings Everything external to the system is considered to be part of the system's surroundings. boundary The system is distinguished from its surroundings by a specified boundary,which may be at rest or in motion.You will see that the interactions between a system and its surroundings,which take place across the boundary,play an important part in engi- neering thermodynamics. Two basic kinds of systems are distinguished in this book.These are referred to,respec- tively,as closed systems and control volumes.A closed system refers to a fixed quantity of matter,whereas a control volume is a region of space through which mass may flow. The term control mass is sometimes used in place of closed system,and the term open system is used interchangeably with control volume.When the terms control mass and control volume are used,the system boundary is often referred to as a control surface
4 Chapter 1 Getting Started 1.1 Using Thermodynamics Engineers use principles drawn from thermodynamics and other engineering sciences, including fluid mechanics and heat and mass transfer, to analyze and design things intended to meet human needs. Throughout the twentieth century, engineering applications of thermodynamics helped pave the way for significant improvements in our quality of life with advances in major areas such as surface transportation, air travel, space flight, electricity generation and transmission, building heating and cooling, and improved medical practices. The wide realm of these applications is suggested by Table 1.1 . In the twenty-first century, engineers will create the technology needed to achieve a sustainable future. Thermodynamics will continue to advance human well-being by addressing looming societal challenges owing to declining supplies of energy resources: oil, natural gas, coal, and fissionable material; effects of global climate change; and burgeoning population. Life in the United States is expected to change in several important respects by midcentury. In the area of power use, for example, electricity will play an even greater role than today. Table 1.2 provides predictions of other changes experts say will be observed. If this vision of mid-century life is correct, it will be necessary to evolve quickly from our present energy posture. As was the case in the twentieth century, thermodynamics will contribute significantly to meeting the challenges of the twenty-first century, including using fossil fuels more effectively, advancing renewable energy technologies, and developing more energy-efficient transportation systems, buildings, and industrial practices. Thermodynamics also will play a role in mitigating global climate change, air pollution, and water pollution. Applications will be observed in bioengineering, biomedical systems, and the deployment of nanotechnology. This book provides the tools needed by specialists working in all such fields. For nonspecialists, the book provides background for making decisions about technology related to thermodynamics—on the job, as informed citizens, and as government leaders and policy makers. 1.2 Defining Systems The key initial step in any engineering analysis is to describe precisely what is being studied. In mechanics, if the motion of a body is to be determined, normally the first step is to define a free body and identify all the forces exerted on it by other bodies. Newton’s second law of motion is then applied. In thermodynamics the term system is used to identify the subject of the analysis. Once the system is defined and the relevant interactions with other systems are identified, one or more physical laws or relations are applied. The system is whatever we want to study. It may be as simple as a free body or as complex as an entire chemical refinery. We may want to study a quantity of matter contained within a closed, rigid-walled tank, or we may want to consider something such as a pipeline through which natural gas flows. The composition of the matter inside the system may be fixed or may be changing through chemical or nuclear reactions. The shape or volume of the system being analyzed is not necessarily constant, as when a gas in a cylinder is compressed by a piston or a balloon is inflated. Everything external to the system is considered to be part of the system’s surroundings. The system is distinguished from its surroundings by a specified boundary, which may be at rest or in motion. You will see that the interactions between a system and its surroundings, which take place across the boundary, play an important part in engineering thermodynamics. Two basic kinds of systems are distinguished in this book. These are referred to, respectively, as closed systems and control volumes . A closed system refers to a fixed quantity of matter, whereas a control volume is a region of space through which mass may flow. The term control mass is sometimes used in place of closed system, and the term open system is used interchangeably with control volume. When the terms control mass and control volume are used, the system boundary is often referred to as a control surface . system surroundings boundary c01GettingStarted.indd Page 4 6/26/10 12:11:20 PM user-s146 /Users/user-s146/Desktop/Merry_X-Mas/New
1.2 Defining Systems TABLE 1.1 Selected Areas of Application of Engineering Thermodynamics Aircraft and rocket propulsion Alternative energy systems Fuel cells Geothermal systems Magnetohydrodynamic (MHD)converters Ocean thermal,wave,and tidal power generation Solar-activated heating,cooling,and power generation Solar-cell arrays Thermoelectric and thermionic devices Wind turbines Automobile engines Bioengineering applications Biomedical applications Combustion systems Compressors,pumps Cooling of electronic equipment Cryogenic systems,gas separation,and liquefaction Fossil and nuclear-fueled power stations Heating,ventilating,and air-conditioning systems Surfaces with thermal Absorption refrigeration and heat pumps control coatings Vapor-compression refrigeration and heat pumps Interational Space Station Steam and gas turbines Power production Propulsion Steam generator Electric Combustion power gas cleanup Turbine Coal Air Cooling Generator tower Condenser Ash Condensate Cooling water Refrigerator Electrical power plant Vehicle engine Trachea、 ung Fuel in Compressor Combustor Turbine Air in Hot gases out He Turbojet engine Biomedical applications
1.2 Defining Systems 5 TABLE 1.1 Refrigerator Turbojet engine Compressor Turbine Air in Hot gases out Combustor Fuel in Coal Air Condensate Cooling water Ash Stack Steam generator Condenser Generator Cooling tower Electric power Electrical power plant Combustion gas cleanup Turbine Steam Vehicle engine Trachea Lung Heart Biomedical applications International Space Station control coatings International Space Station Solar-cell arrays Surfaces with thermal control coatings Refrigerator Coal Air Condensate Cooling water Ash Stack Steam generator Condenser Generator Cooling tower Electric power Electrical power plant Combustion gas cleanup Turbine Steam International Space Station control coatings Selected Areas of Application of Engineering Thermodynamics Aircraft and rocket propulsion Alternative energy systems Fuel cells Geothermal systems Magnetohydrodynamic (MHD) converters Ocean thermal, wave, and tidal power generation Solar-activated heating, cooling, and power generation Thermoelectric and thermionic devices Wind turbines Automobile engines Bioengineering applications Biomedical applications Combustion systems Compressors, pumps Cooling of electronic equipment Cryogenic systems, gas separation, and liquefaction Fossil and nuclear-fueled power stations Heating, ventilating, and air-conditioning systems Absorption refrigeration and heat pumps Vapor-compression refrigeration and heat pumps Steam and gas turbines Power production Propulsion c01GettingStarted.indd Page 5 4/26/10 11:55:02 AM users-133 /Users/users-133/Desktop/Ramakant_04.05.09/WB00113_R1:JWCL170/New
6 Chapter 1 Getting Started TABLE 1.2 Predictions of Life in the United States in 2050 At home Homes are constructed better to reduce heating and cooling needs Homes have systems for electronically monitoring and regulating energy use. Appliances and heating and air-conditioning systems are more energy-efficient. Use of solar energy for space and water heating is common. More food is produced locally. Transportation Plug-in hybrid vehicles and all-electric vehicles dominate. Hybrid vehicles mainly use biofuels. Use of public transportation within and between cities is common. An expanded passenger railway system is widely used. Lifestyle Efficient energy-use practices are utilized throughout society. Recycling is widely practiced,including recycling of water. Distance learning is common at most educational levels. Telecommuting and teleconferencing are the norm. The Internet is predominately used for consumer and business commerce. Power generation Electricity plays a greater role throughout society. Wind,solar,and other renewable technologies contribute a significant share of the nation's electricity needs. A mix of conventional fossil-fueled and nuclear power plants provide a smaller,but still significant,share of the nation's electricity needs. A smart and secure national power transmission grid is in place. 1.2.1t Closed Systems closed system A closed system is defined when a particular quantity of matter is under study.A closed system always contains the same matter.There can be no transfer of mass across its boundary.A special type of closed system that does not interact in any way isolated system with its surroundings is called an isolated system. Figure 1.1 shows a gas in a piston-cylinder assembly.When the valves are closed, we can consider the gas to be a closed system.The boundary lies just inside the piston and cylinder walls,as shown by the dashed lines on the figure.Since the portion of Gas Boundary the boundary between the gas and the piston moves with the piston,the system vol- ume varies.No mass would cross this or any other part of the boundary.If combustion occurs,the composition of the system changes as the initial combustible mixture becomes products of combustion. 1.2.2t Control Volumes In subsequent sections of this book,we perform thermodynamic analyses of devices such as turbines and pumps through which mass flows.These analyses can be con- ducted in principle by studying a particular quantity of matter,a closed system,as it passes through the device.In most cases it is simpler to think instead in terms of a given region of space through which mass flows.With this approach,a region within Fig.1.1 Closed system:A gas a prescribed boundary is studied.The region is called a control volume.Mass may cross in a piston-cylinder assembly. the boundary of a control volume. A diagram of an engine is shown in Fig.1.2a.The dashed line defines a control control volume volume that surrounds the engine.Observe that air,fuel,and exhaust gases cross the boundary.A schematic such as in Fig.1.2b often suffices for engineering analysis
6 Chapter 1 Getting Started closed system isolated system control volume Fig. 1.1 Closed system: A gas in a piston–cylinder assembly. Gas Boundary 1.2.1 Closed Systems A closed system is defined when a particular quantity of matter is under study. A closed system always contains the same matter. There can be no transfer of mass across its boundary. A special type of closed system that does not interact in any way with its surroundings is called an isolated system. Figure 1.1 shows a gas in a piston–cylinder assembly. When the valves are closed, we can consider the gas to be a closed system. The boundary lies just inside the piston and cylinder walls, as shown by the dashed lines on the figure. Since the portion of the boundary between the gas and the piston moves with the piston, the system volume varies. No mass would cross this or any other part of the boundary. If combustion occurs, the composition of the system changes as the initial combustible mixture becomes products of combustion. Predictions of Life in the United States in 2050 At home c Homes are constructed better to reduce heating and cooling needs. c Homes have systems for electronically monitoring and regulating energy use. c Appliances and heating and air-conditioning systems are more energy-efficient. c Use of solar energy for space and water heating is common. c More food is produced locally. Transportation c Plug-in hybrid vehicles and all-electric vehicles dominate. c Hybrid vehicles mainly use biofuels. c Use of public transportation within and between cities is common. c An expanded passenger railway system is widely used. Lifestyle c Efficient energy-use practices are utilized throughout society. c Recycling is widely practiced, including recycling of water. c Distance learning is common at most educational levels. c Telecommuting and teleconferencing are the norm. c The Internet is predominately used for consumer and business commerce. Power generation c Electricity plays a greater role throughout society. c Wind, solar, and other renewable technologies contribute a significant share of the nation’s electricity needs. c A mix of conventional fossil-fueled and nuclear power plants provide a smaller, but still significant, share of the nation’s electricity needs. c A smart and secure national power transmission grid is in place. TABLE 1.2 1.2.2 Control Volumes In subsequent sections of this book, we perform thermodynamic analyses of devices such as turbines and pumps through which mass flows. These analyses can be conducted in principle by studying a particular quantity of matter, a closed system, as it passes through the device. In most cases it is simpler to think instead in terms of a given region of space through which mass flows. With this approach, a region within a prescribed boundary is studied. The region is called a control volume. Mass may cross the boundary of a control volume. A diagram of an engine is shown in Fig. 1.2 a . The dashed line defines a control volume that surrounds the engine. Observe that air, fuel, and exhaust gases cross the boundary. A schematic such as in Fig. 1.2 b often suffices for engineering analysis. c01GettingStarted.indd Page 6 7/1/10 10:35:38 AM user-s146 /Users/user-s146/Desktop/Merry_X-Mas/New