Technology & Engineering
Closed System Thermodynamics
Closed system thermodynamics refers to the study of energy and heat transfer within a system that does not exchange matter with its surroundings. In this context, the focus is on understanding the internal energy changes and heat interactions within the system, without considering external influences. This approach allows for the analysis of energy transformations and the development of thermodynamic principles for various engineering applications.
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10 Key excerpts on "Closed System Thermodynamics"
- John Reisel(Author)
- 2021(Publication Date)
- Cengage Learning EMEA(Publisher)
These are technically open systems, but under what conditions do you think it is acceptable for engineers to treat them as closed systems? A special application of a closed system is a thermodynamic cycle, where a system will undergo a series of processes resulting in the final state being equal to the initial state. One type of cycle involves a fluid proceeding through several devices, eventually returning to its initial state so it can repeat the process of flowing through the devices. An example of this is the Rankine cycle, shown in Figure 4.23, which is used to model simple steam power plants. A second type of cycle consists of the fluid remaining in one device while undergoing several processes in that device. Figure 4.24 shows an example of this for a gas in a piston–cylinder device undergoing an Otto cycle; the Otto cycle is used to model a spark-ignition engine. If we consider the first law as applied over the entire cycle, we see that the initial internal energy is the same as the final internal energy (u 1 5 u 2 ) (the same is true of the kinetic and potential energies as well). So, applying Eq. (4.32), we see that for a thermodynamic cycle, the net heat transfer and the net work must be equal: Q cycle 5 W cycle (4.33) where these quantities are the summations of the individual process’s heat transfers and works. Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 149 4.4 First Law of Thermodynamics in Closed Systems Steam Generator Turbine Condenser Pump FIGURE 4.23 The four components of a simple Rankine cycle.
eBook - PDF- Bernard Desmet(Author)
- 2022(Publication Date)
- Wiley-ISTE(Publisher)
In technical thermodynamics, we are interested more often in the equipment (heat exchangers, turbines, compressors, etc.) through which one or more fluids flow. Generally, we look for characteristics (pressure, temperature, mass flow rate, etc.) in the fixed sections located on either side of the component being studied and defined as the inlet and output of this component. These sections are continuously crossed by the flowing fluids. A closed control surface that comprises the inlet and outlet sections of the component therefore does not determine a closed system. This is called an open system. In the case of an open system, the material contained within the boundaries of the control surface is constantly renewed. 1.2.2. First law For a closed system that evolves following a cyclic transformation (the final state coinciding with the initial state) by exchanging work W e and heat Q e with the exterior (Figure 1.1), the first law of thermodynamics expresses the equivalence between heat and work: W e + Q e = 0 [1.1] For a closed system that evolves from an initial state i into a final state f : W e + Q e = U f − U i = ΔU i−f [1.2] where U represents the internal energy of the considered system. U [J] is an extensive state quantity; therefore, it only depends on the state of the system. Figure 1.1. Closed system: first law Energy Conversion: Thermodynamic Basics 3 In the case when kinetic energy of the system plays a significant role, we can write: W e + Q e = ΔU i−f + ΔEc i−f [1.3] where ΔEc i−f represents the change in the kinetic energy of the system between the initial and final states. Now let us consider the case of a machine that functions in a steady state through which a flowing fluid of mass flow rate q m passes (Figure 1.2), comprising only a single inlet in and a single outlet out situated at the heights z in and z out , respectively.
eBook - PDF- Gerard Olivier, Vincent Lemort, Georges de Pelsemaeker(Authors)
- 2023(Publication Date)
- Wiley(Publisher)
1 1 Fundamentals 1.1 Introduction This textbook deals with the study of different vehicle thermal systems and components from an energy engineering point of view. It is therefore necessary to recall the fundamentals of heat trans- fer as well as thermodynamics and some elements of fluid mechanics for a good understanding of the content of the next Chapters 2, 3, and 4. This is the objective of the present chapter, the content of which has been largely summarized from major reference textbooks, especially those of Incropera and DeWitt (2002), Çengel and Boles (2006), Braun and Mitchell (2012), and Klein and Nellis (2016). 1.2 Fundamental Definitions in Thermodynamics Thermodynamics is the branch of physics that studies conversions between heat and work in one or the other direction. Thermodynamics is particularly useful for the analysis of components and systems presented in this book. Thermodynamics makes use of some important notions to which the reader should become familiar. 1.2.1 System, Surroundings, and Universe In thermodynamics, a system is defined as a delimited region of space or a quantity of matter that is investigated. The concept of “investigation” may still be a little bit fuzzy and will progressively develop. Let’s say that investigating a system means quantifying its energy performance and the relation between this performance and operating conditions. The system is delimited by a boundary (Figure 1.1). A boundary has neither mass nor thickness. The surroundings of the system are the region of space or the quantity of matter that is outside the system. Hence, the boundary is the sur- face that separates the system from its surroundings. The system and its surroundings constitute the universe. Among the systems, one can distinguish the closed systems and the open systems. A closed system does not exchange any mass with its surroundings.
eBook - PDFEntropy Generation Minimization
The Method of Thermodynamic Optimization of Finite-Size Systems and Finite-Time Processes
- Adrian Bejan(Author)
- 2013(Publication Date)
- CRC Press(Publisher)
1 THERMODYNAMIC CONCEPTS AND LAWS The subject of engineering thermodynamics revolves around two pivotal state-ments, the first and the second laws of thermodynamics. Both laws are old, relative to our lifetime experience, the first law being the product of a vehement debate started approximately 200 years ago. Because the objective of all introductory thermodynamics courses is to explain the meaning and usefulness of the two laws and their related concepts (Moran, 1989), in the present treatment it is assumed that the laws are known and accepted. However, in order to provide a common language and ground for the issues to be debated in this book, the basic concepts introduced in engineering through thermodynamics are reviewed in this chapter. The review is limited to the thermodynamics of a pure substance. 1.1 DEFINITIONS A key concept in thermodynamic analysis, often abused, is the concept of system. A thermodynamic system is the region or collection of matter in space that is selected for analysis. The concept of system requires the recognition of an envi-ronment, which is the space, or system, external to the system of interest. Separating the two systems is the system boundary (frontier), which, in general, is a real or imaginary surface delineating the contour of the system of interest. The system boundary may or may not possess special features that, as a matter of consequence, lead to a hierarchic ordering of thermodynamic systems for the purpose of analysis. For example, a boundary that is impermeable to mass flow defines a closed system. Naturally, in a closed system the matter (mass inventory) is conserved. On the other hand, a boundary that is permeable (has openings, ports) for mass transfer defines an open system. The flow of mass through the system boundary is only one of the three transfer effects (interactions) commonly encountered in engineering applications. The other two effects are heat transfer and work transfer.
eBook - ePub- Michael J. Moran, Howard N. Shapiro, Daisie D. Boettner, Margaret B. Bailey(Authors)
- 2018(Publication Date)
- Wiley(Publisher)
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.LEARNING OUTCOMES
When you complete your study of this chapter, you will be able to…- Explain 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.
- Identify SI and English Engineering units, including units for specific volume, pressure, and temperature.
- Describe the relationship among the Kelvin, Rankine, Celsius, and Fahrenheit temperature scales.
- Apply appropriate unit conversion factors during calculations.
- Apply the problem-solving methodology used in this book.
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 devices 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
- S. Bobby Rauf(Author)
- 2021(Publication Date)
- River Publishers(Publisher)
However, in this chapter we will focus on categorization of thermodynamic systems based on their interaction with the surroundings or environment. From thermodynamic system and environment interface perspective, thermodynamic systems can be categorized as follows: 91 92 Thermodynamics Made Simple for Energy Engineers I. Open Thermodynamic Systems II. Closed Thermodynamic Systems III. Isolated Thermodynamic Systems Open Thermodynamic Systems Open thermodynamic systems are systems in which, in addition to the exchange of heat energy with the surroundings, mass or matter are free to cross the system boundary. Also, in open thermodynamic systems, work is performed on or by the system. The type of open thermodynamic systems where entering mass fow rate is the same as the exiting mass fow rate is referred to as a Steady Flow Open System . Examples of Steady Flow Open Systems include pumps, compressors, turbines and heat exchangers. Closed Thermodynamic Systems Closed thermodynamic systems are systems in which no mass crosses the system boundary. Energy, however, can cross through the system boundary in form of heat or work. Examples of closed thermodynamic systems include: sealed pneumatic pistons and refrigerant in a refrigeration system. Isolated Thermodynamic Systems Isolated thermodynamic systems are systems in which no work is performed by or on the system; no heat is added or extracted from the system and no matter fows in or out of the system. Imagine a rigid sealed steel cylinder containing liquid nitrogen. This steel cylinder is heavily insulated and is placed inside another sealed steel container such that cylinder’s walls do not come in contact with the outside steel container. If vacuum is now created between the outer container and the inner gas cylinder, you would have a thermodynamic system that is “isolated” for most practical purposes.
eBook - PDFThermodynamics
A Smart Approach
- Ibrahim Dinçer(Author)
- 2020(Publication Date)
- Wiley(Publisher)
Between source and system, there is a need for storage, for example with solar energy as the energy source the sun does not shine all the time, so storage becomes a necessity. If after the system one produces more useful output than is needed, storage is required. This way the equation becomes 3S + 2S, which will become larger S, resulting in sustainability. This chapter aims to make a primary focus on system analysis as a critical step in ther-modynamics through the balance equations for mass, energy, entropy, and exergy for both types of closed and open systems in a more holistic manner. 5.2 Thermodynamic Laws Thermodynamics is defined as the science of energy. The word thermodynamics is thought to be derived from the Greek words therme, which means heat, and dynamis, that means power. The origin of the word thermodynamics is descriptive of many energy conversion processes, where heat (thermal energy) is converted to work or electrical energy. Numerous thermodynamic books define thermodynamics as the science of energy and entropy. How-ever, it is now introduced as the science of energy (which comes from the first law of MBE: m 4 = m 1 . . . . . EBE: m 4 h 4 + Q ev = m 1 h 1 . . . . EnBE: m 4 s 4 + S gen ,4 → 1 + Q ev = m 1 s 1 T ev . . . . ExBE: m 4 ex 4 + Ex Qev = m 1 ex 1 + Ex d, 4 → 1 Figure 5.1 A concept of illustrating how to go from analysis to energy system development for implementation in mimicking planting to harvesting. 234 5 System Analysis thermodynamics (FLT)) and exergy (which comes from the SLT). Technically, both the FLT and SLT become really the governing laws of thermodynamics while other laws (zeroth and third) are the policy type laws, which are specific to the conditions. As mentioned earlier, the principles of thermodynamics are best presented through its four main laws, i.e. the zeroth, first, second, and third laws of thermodynamics. Although each of these laws has its own significance, the prime focus will be on the FLT and SLT.
eBook - PDF- Donald Olander(Author)
- 2007(Publication Date)
- CRC Press(Publisher)
118 General Thermodynamics The table below shows several features of this process for T 20 / T 10 = 0.67. The middle column gives results for the heat exchange between the two blocks without the heat engine (Figure 1.16). The entropy changes for each block are computed using Equation (3.23). The final temperature of the blocks with the engine running is less than in the absence of the engine because energy is removed from the overall system in the form of work. The entropy change of the combined system without the engine increases, but there is no change in entropy with the heat engine. Other problems involving heat engines operating on the Carnot cycle include Problems 4.1 to 4.5, 4.11 and 4.12, and 4.15 and 4.16. 4.4 THERMODYNAMICS OF OPEN SYSTEMS Before embarking on analyses of practical power cycles, understanding of open (or flow) systems is necessary. The laws of thermodynamics can be applied to fluids flowing through devices that change the properties of the fluid by exchanging heat and/or work with the surroundings. Examples of such devices include pumps, boilers, turbines, valves, nozzles (used for increasing fluid velocity) and orifices in pipes. Some of these devices are included in the simple steam cycle shown in Figure 4.4. In this cycle, the components are connected in series with the working fluid circu-lating continuously through them. Each device in the cycle is subjected to a first law analysis, and in some, application of the second law provides additional information on their performance. 4.4.1 T HE F IRST L AW FOR O PEN (F LOW ) S YSTEMS All of the devices mentioned above can be represented by the schematic open system shown in Figure 4.9. This generalized device has a rigid casing forming a boundary that does no pV work. However, the unit may perform or accept shaft work, W g , as do the pump and turbine in Figure 4.4.
eBook - PDF- Myron Kaufman(Author)
- 2002(Publication Date)
- CRC Press(Publisher)
Thermo- dynamics is different from these other fields in that it considers the energy of entire systems, consisting of huge numbers of particles (and perhaps radiation fields). The approach of thermodynamics is totally macroscopic and its conclu- sions are not based on any particular model for the behavior and nature of the microscopic particles. 2.2 Systems We live in a very complicated universe. Clearly, not even with the most powerful computers would we be able to study the details of all parts of the universe. If we are to make any progress in thinking about energy, we must focus our attention on Copyright © 2002 by Taylor & Francis Group LLC only part of the universe. This part we call the system. The remainder of the universe is termed the surroundings. In some cases, it will be possible to consider the system as isolated (i.e., not interacting with the surroundings). In order to be isolated, the boundaries of a system must be impermeable to mass and energy. Such boundaries cannot allow any interaction with external mechanical or electrical forces. For example, if there is an external pressure, the walls of the system must be rigid so that they cannot be moved by the pressure. In addition, the system must also be adiabatic (i.e., not allowing any energy to flow through the walls in the absence of such forces). In most cases, we will be forced to define our system in such a way that it exchanges mass or energy with the surroundings. Systems that can exchange energy, but not mass, with the surroundings are called closed systems; those that can exchange both energy and mass are called open systems. It is not necessary to consider systems that exchange mass, but not energy, with the surroundings, because the transferring mass will bring its internal energy with it into the system. We will start by dealing exclusively with isolated and closed systems and then extend our considerations to open systems, beginning with Chapter 6.
- Lucien Borel, Daniel Favrat(Authors)
- 2010(Publication Date)
- PPUR(Publisher)
Closed system with fluid transfer and in steady-state operation With a similar reasoning as that in Subsection 13.3.2, we obtain the following exergy balance: (13.32) Here, and are, respectively, the heat power received from the source at temperature and the work power given by the system. To make things concrete, we assume that the temperature is higher than the temperature . Relations (13.31) and (13.32) lead to the same features, one in energy and the other in power units. For example, accounting for Equation (13.28), Relation (13.31) shows that • if is positive and if the entropy creation is not significant, it is possible to write the relation (13.28) E E Q Q E E Q Q a a a a b + + + + + + + + + + + = + + + = 0 Q a + Q b + T a T b dS Q T Q T S a a b b i = + + ∫ ∫ ∫ ∫ + + δ δ δ S i 0 = + + + + δ δ δ Q T Q T S a a b b i Q a + E a + E T T Q T S E L a b b a i qb − + + = − ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ − = − 1 T S a i E E L T T Q L T T qb a b b a b − + + = − = − ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ − = − ⎛ ⎝ ⎜ ⎞ 1 1 ⎠ ⎟ − + Q T S b a i Q b + E − T b T b T a Q b + Thermodynamic cycles 619 (13.33) • if is negative, we imperatively have the relation (13.34) Conclusions The results obtained above highlight the following: General relations Relations (10.113), (13.28) and (13.31) give, in specific units, the following general relations (13.35) (13.36) (13.37) in which • is the Carnot factor, related to the temperature of the thermal source, defined, according to Equation (10.36), by the relation (13.38) • is the entropy creation due to the irreversibilities of the system, positive or null according to the Second Law ( ). • A closed system, undergoing a bithermal cycle, can receive heat (or heat power) and supply work (or work power). Such a cycle is called a power cycle. • A closed system, undergoing a bithermal cycle, can also receive work (or work power) and supply heat (or heat power).
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