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.
8 Key excerpts on "Closed System Thermodynamics"
eBook - ePub- Richard Gentle, Peter Edwards, William Bolton(Authors)
- 2001(Publication Date)
- Newnes(Publisher)
...2 Thermodynamics Summary Thermodynamics is an essential part of the study of mechanical engineering. It involves knowledge basic to the functioning of prime movers such as petrol and diesel engines, steam turbines and gas turbines. It covers significant operating parameters of this equipment in terms of fuel consumption and power output. In industrial and domestic heating systems, refrigeration, air conditioning and in thermal insulation in buildings and equipment, the understanding of basic thermodynamic principles allows effective systems to be developed and applied. In almost all manufacturing industry there are processes which involve the use of heat energy. This chapter imparts the fundamentals of thermodynamics in the major fields and then applies them in a wide range of situations. The basis is therefore laid for further study and for the understanding of related processes in plant and equipment not covered here. Objectives By the end of this chapter, the reader should be able to: • understand the principle of specific and latent heat and apply it to gases and vapours; • appreciate the processes which can be applied to a gas and the corresponding heat and work energy transfers involved; • relate the gas processes to power cycles theoretical and actual; • understand the processes relating to steam and apply them in steam power plant; • apply the vapour processes to refrigeration plant, and establish refrigeration plant operating parameters; • understand the principles of heat transfer by conduction through plane walls and pipework. 2.1 Heat energy This chapter introduces heat energy by looking at the specific heat and latent heat of solids and gases. This provides the base knowledge required for many ordinary estimations of heat energy quantities in heating and cooling, such as are involved in many industrial processes, and in the production of steam from ice and water...
eBook - ePub- Mike Pauken(Author)
- 2011(Publication Date)
- For Dummies(Publisher)
...See, you’ve used thermodynamics without even realizing it! This chapter introduces you to thermodynamic analysis of some simple processes involving heat and work for open systems. The concepts using the first law of thermodynamics I discuss here are similar to the ones presented in Chapter 5 for closed systems. The difference between an open system and a closed system is whether or not a fluid is allowed to flow into or out of a system. You may be able to guess by their names that a fluid can’t flow in a closed system, but it can flow in an open system. Some examples of simple open systems include heat exchangers, pumps, compressors, turbines, and nozzles. These devices are used in more complicated systems such as power plants, air-conditioning systems, and jet engines, which I discuss in Chapters 10–13. Conserving Mass in an Open System The best way to begin every thermodynamic analysis is by defining a system. A system describes a region enclosed by an imaginary boundary (which may be fixed or flexible) that contains a mass or volume to use for analysis. A system that doesn’t allow mass to enter or leave is called a closed system. The mass inside a closed system is often called the control mass. A system that allows mass to enter and leave is called an open system. The volume of an open system is often called the control volume. This chapter focuses on thermodynamic analysis using the conservation of mass and conservation of energy for open systems. Conservation of mass means that the mass flow rate of material entering a system minus the mass flow rate leaving equals the mass that may accumulate within the system, as described by this equation: When you see a “dot” over a variable like mass (), the dot means that the variable is on a rate basis or per unit time...
eBook - ePub- Tangellapalli Srinivas(Author)
- 2021(Publication Date)
- Bentham Science Publishers(Publisher)
...A typical thermal power plant consists of four thermodynamic systems viz. turbine, condenser, pump, and boiler. The feedwater is heated with a heat source and turned into superheated steam. In the condenser, the vapour is condensed into a saturated liquid state by air circulation or water circulation. The power plant handles various fluid lines such as fuel, air, cooling oil, steam, circulating water, feedwater, and hot gas. Similarly, the systems also involve heat and work transfers. Therefore, the thermodynamic system can be described with mass and energy transactions. To understand the nature of system, it is required to define the terminology used in the system, and they are surroundings, boundary, control surface, control volume, etc. The space outside the system is called as surroundings. Boundary is the enclosure that separates the system from the surroundings. The boundary may be real or imaginary. It is a stationary boundary or moving boundary. The system and its surroundings together are called as the universe. Thermodynamic systems can be grouped into an open system, closed system, and isolated system. In an open system, the mass and energy cross the boundary. In this system, the fixed region in space is the control volume, and the surface of the control volume is called as the control surface. For example, in a steam boiler, feedwater enters into the system and leaves as a superheated steam (mass transfer) by absorbing heat (energy interaction). Compresser, turbine, nozzle, diffuser, steam engine, boiler, etc., are the open systems. If a system allows mass without energy transfer, such as steam flowing in an insulated pipe, that is also an open system. In this case, even though there are no energies crossing the boundary, because of insulated pipe, the fluid carries energy along with the flow, which is called kinetic energy. In addition to this kinetic energy, it also possesses flow work...
eBook - ePub- H. W. Liepmann, A. Roshko(Authors)
- 2013(Publication Date)
- Dover Publications(Publisher)
...Thermodynamics predicts the pressure and temperature in this final state easily. Fluid mechanics of a real fluid should tackle the far more difficult task of computing the pressure, temperature, etc., as a function of time and location within the container. For large times, pressure and temperature will approach the thermodynamically given values. Sometimes we need only these final, equilibrium values and hence can make very good use of thermodynamic reasoning even for problems that involve real fluid flow. In fluid mechanics of low-speed flow, thermodynamic considerations are not needed: the heat content of the fluid is then so large compared to the kinetic energy of the flow that the temperature remains nearly constant even if the whole kinetic energy is transformed into heat. In modern high-speed flow problems, the opposite can be true. The kinetic energy can be large compared to the heat content of the moving gas, and the variations in temperature can become very large indeed. Consequently the importance of thermodynamic concepts has become steadily greater. The chapter therefore includes material that is more advanced and not needed for the bulk of the later chapters. Articles that are starred can be omitted at first reading without loss of continuity. 1.2 Thermodynamic Systems A thermodynamic system is a quantity of matter separated from the “surroundings” or the “environment” by an enclosure. The system is studied with the help of measurements carried out and recorded in the surroundings. Thus a thermometer inserted into a system forms part of the surroundings. Work done by moving a piston is measured by, say, the extension of a spring or the movement of a weight in the surroundings. Heat transferred to the system is measured also by changes in the surroundings, e.g., heat may be transferred by an electrical heating coil...
eBook - ePub- Jeffrey R. S. Brownson(Author)
- 2013(Publication Date)
- Academic Press(Publisher)
...Appendix A Energy Conversion Systems Energy Conversion Systems (ECS) are our bread and butter. You can read much more about ECS in the US Department of Energy’s Energy Information Administration site online: Energy Explained. Much of what we have used for common terminology (such as non-equilibrium conditions, steady state conditions), will involve language from Modern Thermodynamics developed by Ilya Prigogine and Lars Onsager, expanded by Ji-Tao Wang. 1 Robot Monkey’s Last Stand: Heat Pumps, Heat Engines, Entropy, and Modern Thermodynamics Modern Thermodynamics is concerned with both spontaneous processes, and the direction opposite of the spontaneous process (what is not forbidden is allowable). Energy systems and materials get very interesting, and permit innovation when you begin to couple heat engines with heat pumps. 2 In the end, we are essentially talking about coupling of the solar pump to numerous heat engines that will provide work for use in the environment, to the additional benefit of society. Transformation : The First Law of Thermodynamics delineates a conservation of Energy. Systems can only undergo transformations from an initial state (Form 1) to a final state (Form 2). Given transformations of states of Heat and states of Work, the summed total energy (here, labeled U) is said to be independent of the path (meaning the types of transformation). In a hypothetical cyclic process, the integral of the energy change is zero (Eq. (A.1)). (A.1) Form : A state of energy derived from Sources like photons coming as an electromagnetic form of energy from the Solar resource of our nearest star (93 million miles away). Source 1 : A phenomenological manifestation (observable) of a state of energy. This use of the term includes a force combined either with mass (matter) or electromagnetism (light). Heat : Not a term of thermal energy or energy content...
eBook - ePubBiothermodynamics
Principles and Applications
- Mustafa Ozilgen, Esra Sorguven Oner(Authors)
- 2016(Publication Date)
- CRC Press(Publisher)
...Later it entered into the chemical engineering curricula especially to study hydrocarbon separation processes. The concept of entropy was used in electrical engineering as a measure of information content. Thermodynamics was used to be one of the technological sciences taught in engineering and science curricula. The technological sciences, according to Hansson (2007): Have human-made rather than natural objects as their ultimate study objects, like a steam engine Include the practice of engineering design, like designing a power plant to achieve a predetermined capacity of electric power production Define their study objects in functional terms, like enthalpy and entropy Evaluate these study objects with category-specified value statements, like calculation of coal required to produce predetermined amount of electricity, then relating these numbers with the efficiency of the plant Employ less far-reaching idealizations than the natural sciences, like using block diagrams of the equipment, rather than detailed sketches Do not need an exact mathematical solution when a sufficiently close approximation is available “The development that meets the needs of the present generations without compromising the ability of the future generations to meet their own needs” is referred to as the sustainable development (Borland et al., 1987). In the assessment of new energy sources, sustainability, that is, renewability, is an important concern. Sustainability depends both on the energy content of the input materials and the process pathways (Thamsiriroj and Murphy, 2009). A successful energy source has to be sustainable in economic, social, environmental, and thermodynamic aspects, including—among other criteria—minimization of the net carbon dioxide emission, and to be complementary with the food supply and waste management programs (Cramer et al., 2006; Worldwatch Institute, 2007; Goldemberg et al., 2008)...
eBook - ePubEssentials of Energy Technology
Sources, Transport, Storage, Conservation
- Jochen Fricke, Walter L. Borst(Authors)
- 2013(Publication Date)
- Wiley-VCH(Publisher)
...Stirling engines are being used very successfully in refrigeration systems, for instance, in infrared cameras. 3.3 Irreversibilities The Carnot and idealized Stirling processes apply to infinitely slow, reversible processes. But technical processes generally have to run rather fast. This leads to irreversibilities associated with an increase in entropy. Important examples are the walls of heat exchangers (Figure 3.8) that are present in all power plants and heating systems. Figure 3.8 Infinitely large planar wall of a heat exchanger with surface temperatures T and T − Δ T and surrounding temperature T surr. Heat d Q enters and leaves the wall. Associated with d Q is the entropy d S h on the hot side and d S c on the cold side. Under stationary conditions, energy conservation implies that d Q entering the left is the same as d Q leaving the right side. As the heat enters the wall at the temperature T and leaves it at T − Δ T, an entropy increase has occurred: 3.5 This shows that the greater the temperature change Δ T in the wall for a given d Q, the larger the entropy increase. In order to reduce the entropy production, one therefore would have to reduce Δ T and/or raise the temperature T. But keeping the throughput d Q the same with a smaller Δ T would require a larger surface of the heat exchanger. This is not practical in most cases and corresponding entropy increases hence are unavoidable. Actually, heat exchangers are built as compact as possible in order to minimize the amount of steel and the required building volume, irrespective of entropy considerations. 3.4 Exergy and Anergy In addition to the concept of entropy, engineers have used a quantity named exergy in order to characterize the efficiency of devices. By using the Carnot efficiency in Eq. (3.1), the exergy E x, measured in joules, is related to the heat Q at temperature T h as follows: 3.6 where T surr is the temperature of the surroundings in which the device works, for instance, T surr ≈ 300 K...
eBook - ePub- Andrè Garcia McDonald, Hugh Magande(Authors)
- 2012(Publication Date)
- Wiley(Publisher)
...6 Performance Analysis of Power Plant Systems Power plant systems are used to generate electrical power and heat. Power plants are multicomponent systems with turbines, compressors, steam boilers (steam generators), condensers, other heat exchangers, pumps, and combustion burners, to name a few. Although this type of system operates on a thermodynamic (power) cycle to produce electrical power, other fundamental concepts from fluid mechanics (pipe and duct sizing, pump sizing) and heat exchanger design (design of condensers, feedwater heaters, reheaters) may be needed. Due to the multicomponent nature of power plant systems, their design can be laborious, especially when control system design is included. In addition, significant analysis must be conducted to determine the most economical power plant that will yield the greatest efficiency and performance to deliver a required amount of power. In performance analysis of power plant systems, the design engineer will analyze existing power plants and their components to make recommendations for improvement of the systems. 6.1 Thermodynamic Cycles for Power Generation—Brief Review 6.1.1 Types of Power Cycles The thermodynamic (power) cycles are categorized into two groups: gas cycles and vapor cycles. In a gas (power) cycle, the working fluid remains as a gas throughout the entire cycle. An example is a gas-turbine system based on the Brayton cycle with air or combustion gas as the working fluid. In a vapor (power) cycle, the working fluid is a gas in one part of the cycle and is a liquid in another part of the system. An example is a steam-turbine system based on the Rankine cycle with pressurized, superheated steam entering a steam turbine and liquid water leaving a condenser. 6.1.2 Vapor Power Cycles—Ideal Carnot Cycle The Carnot cycle is an ideal reversible cycle that can operate between two constant temperature reservoirs...
