Technology & Engineering
Open System Thermodynamic
An open system in thermodynamics refers to a system that can exchange both energy and matter with its surroundings. This means that the system is not isolated and can interact with its environment. Open systems are commonly found in various engineering and technological applications, allowing for the transfer of energy and materials, making them important for understanding real-world processes.
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9 Key excerpts on "Open System Thermodynamic"
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)
national power transmission grid is in place. 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
- 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.
- John Reisel(Author)
- 2021(Publication Date)
- Cengage Learning EMEA(Publisher)
Thermodynamics is the power of heat, or the movement of heat. As our understanding of energy has evolved, we recognize that energy involves more than just heat, and, as such, thermody- namics is considered the science of all energy. In engineering, we use thermo- dynamics to understand how energy is transformed from one form to another to accomplish a given purpose. Thus, we will be exploring not only the basic laws that describe thermodynamics but also the technology that is employed to accomplish tasks using energy. FIGURE 1.2 A cutaway image of an internal-combustion engine cylinder. FIGURE 1.3 Examples of lighting technology: an incandescent light bulb, a compact fluorescent fixture, and an LED bulb. erashov/Shutterstock.com Polryaz/Shutterstock.com Roman Samokhin/Shutterstock.com 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. Chapter 1 Introduction to Thermodynamics and Energy 4 Figure 1.4 shows many applications in the world today, developed by engineers, that use energy and for which thermodynamics is an integral design component. Turbines are used to transform the energy in a working fluid into a rotational motion of a shaft that in turn produces electricity in a generator. The turbines take in a high-energy gas or vapor (which generally has a high temperature and pressure) and extract energy from that fluid to produce the work FIGURE 1.4 Cutaway images of common energy-related technology: a gas turbine engine, a reciprocating engine, and a refrigerator.
eBook - PDFTowards an Environment Research Agenda
A Third Selection of Papers
- A. Winnett(Author)
- 2004(Publication Date)
- Palgrave Macmillan(Publisher)
Widespread concern about resource depletion and environmental degradation are common to them all. It has been argued that these consequences of human development are reflected in thermodynamic ideas and methods of analysis (see, for example, the early work of Mueller (1971) at the US Goddard Space Flight Center); they are said to mirror energy transform- ations within society. Mueller (1971) draws a parallel between the resource flows in economics and energy (as well as implicitly exergy) flows in thermodynamics. This leads him to an analogy, arguably rather dubious, between the ‘technology of man’ and heat engines. Such ideas have inspired the environmental campaigner Sara Parkin (2000) (a co-founder with Jonathan Porritt of the sustainable development charity Forum for the Future) and others to believe that thermodynamic principles or laws may act as a guide for engineers in the quest for envir- onmental sustainability. In the context of ‘The Natural Step’, energy and matter are seen as having a tendency to disperse. Entropy (another second-law extensive property of matter, that is related to exergy via equation (8.10) or (8.11)) is regarded as a measure of this disorder in a closed or isolated system. The earth is such a closed system in terms of matter, but an open one from the perspective of the incoming solar energy that drives living plants via photosynthesis. This underpins the notion of ‘capital’ and ‘income’ energy resources for the planet (such as fossil fuels and solar energy respectively), and is behind the first of the TNS system conditions. Outside the realm of energy systems, thermodynamic concepts are typically employed in terms of an analogy with, or resem- blance to, physical processes.
- Daniel Walgraef, J Martinez-mardones, Carlos Hernan Worner(Authors)
- 2000(Publication Date)
- World Scientific(Publisher)
PHYSICO-CHEMICAL THERMODYNAMICS OF MATERIAL SYSTEMS: A REVIEW OP BASIC CONCEPTS AND RESULTS ARMANDO FERNANDEZ GUILLERMET Consejo National de Investigaciones Cientificas y Ttcnicas Centra Atomico Bariloche-Instituto Balseiro 8400 San Carlos de Bariloche-Argentina. E-mail: [email protected] 1 Introduction 1.1 General Considerations Thermodynamics developed from the study of heat-engines and the relations between heat and work. However, after some time, it was recognized that the study of the effects of the thermal and mechanical interactions between the system and the surroundings provides valuable information on the equilibrium properties of the material systems, and on the reactions or transformations which occur. Today, thermodynamics might be considered as a discipline which deals with (i) a wide class of macroscopic properties of material sys-tems, (ii) the way in which these properties are influenced by the thermal, mechanical and chemical interactions with other systems, and (iii) the reac-tions or transformations involved. One of the key variables in the thermodynamic approach is temperature, and, in a certain sense, thermodynamics may be defined as the science dealing with the forms in which the properties of matter are modified by the changes in temperature. In particular, for material systems, it is interesting to determine the effects of temperature upon the equilibrium properties of a given structure, and to explore the possibility of inducing changes of structure by suitable temperature variations. The question of identifying the most stable structure for given external conditions is usually known as the Phase Stability Problem, which is often considered as a central problem in the study of material systems. Classical thermodynamics developed without referring to any particular model of the structure of matter.
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 - PDFThermo and Fluid Dynamics
Recent Advances
- Dritan Hoxha(Author)
- 2019(Publication Date)
- Arcler Press(Publisher)
Here I will make a parenthesis. People often confuse heat and thermal energy or worse, they consider them as the same thing. Heat and thermal energy, earlier, used to be considered as synonyms. But they differ as follows: Heat is the thermal energy transferred across a boundary of one region of matter to another. As a process variable, heat is a characteristic of a process, not a property of the system. Thermal energy is the internal energy present in a system by virtue of its temperature. The average kinetic energy (translational) possessed by free particles in a system of free particles under thermodynamic equilibrium. One of the most important objectives when dealing with thermodynamics is to measure the amount of thermal energy involved in a certain situation. However, this is a very complicated process because the systems we consider when considering a thermodynamic related situation have a very large number of particles which interact with each other in many ways. Thus, we must have any facility when dealing with these situations in order to make them easier to study. Hence, if these systems are more or less balanced a situation known as equilibrium then it is possible to describe it through a small number of measurements or as otherwise known, “system parameters” [1]. Such a situation exists only in theory and it may occur only when the system is idealized as well as all quantities involved in this system such as the mass, pressure, and volume, or any other equivalent set of numbers. These numbers describe a very large number of variables ranging from 10 26 to 10 30 nominal independent variables. A General View on Thermodynamics 3 Below a map showing several branches of Physics is shown. It will help the reader to understand the place and importance of Thermodynamics as one of key Physics branches. 1.2. ETYMOLOGY OF THERMODYNAMICS It has not been so easy to determine the name of this branch of Physics, although it is relatively a new one.
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.
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