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为分析注蒸汽燃气轮机(STIG)循环余热锅炉回热限制,本文对STIG循环在1000~1300℃的温域,8~42的压比范围进行了仿真计算。计算表明:余热锅炉首先达到哪一种回热限制,取决于具体的给定条件;它受回汪蒸汽温度的影响,并且与最小允许节点温差值的选择有关。 相似文献
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蒸汽冷却及其在先进热力联合循环中的应用 总被引:2,自引:0,他引:2
本文介绍了展高性能燃气轮机采用先进冷却技术的必要性,并就现有的实际燃气轮机蒸汽冷却方案作了介绍,提出了STIG的闭路蒸汽冷却方案,并计算分析了STIG和ISTIG等先进的双工质燃气轮机联合循环中采用蒸汽冷却的可行性及其潜在优势。 相似文献
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运用热力学火用分析的方法,分别考虑了高低温侧换热器、热回收装置侧换热器和中冷器的热阻损失,以及压缩机和涡轮机中的内不可逆损失,以无因次总输出火用和火用效率为目标函数,借助数值分析的方法,研究了恒温热源条件下不可逆中冷焦耳—布雷顿功热并供系统的火用性能,分析了主要特征参数对无因次总输出火用及火用效率的影响。分析结果表明,当中间压比不变而总压比变化时,存在一组最佳运行参数,使无因次总输出火用达到最大,还存在最大的总输出火用和火用效率以及相对应的一组最佳运行参数。提高中冷器换热有效度可以增加无因次总输出火用和火用效率。 相似文献
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燃煤气的闭式 STIG 循环的热力学分析 总被引:3,自引:3,他引:3
本文将煤气化技术用于闭式注蒸汽燃气轮机循环,对以煤气化产物为燃料的闭式注蒸汽循环进行了热力学分析,并与燃煤气的开式STIG循环做了比较,同时分析了回收水量的影响因素。 相似文献
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《Exergy》2001,1(1):41-45
An exergy analysis has been carried out for an irreversible Braysson cycle. The analytical formulae of power output and exergy efficiency are derived. The influences of various parameters on the exergy performance are analyzed by numerical calculation, and the results obtained have been compared with those of Brayton cycle under the same conditions. It is shown that the exergy loss in the combustion is the largest in the Braysson cycle, and both specific work and exergy efficiency of the cycle are larger than those of Brayton cycle. 相似文献
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《International Journal of Hydrogen Energy》2020,45(60):34579-34586
The present study is related with the thermodynamic performance assessment of renewable hydrogen production through Boron thermochemical water splitting cycle. Therefore, all step efficiencies and overall cycle efficiency are calculated based on complete reaction. Additionally, a parametric study is conducted to determine the effect of the reference environment temperature on the overall cycle efficiency. In this regard, exergy efficiencies, exergy destruction rates and also inlet and outlet exergy rates of the cycle are calculated and presented for various reference temperatures. The exergy efficiency of the cycle is calculated as 0.4393 based on complete reaction and occurs at 298 K. This study has shown that Boron thermochemical water splitting cycle has a great potential due to cycle performance. As a result, Boron based thermochemical water splitting cycle can help achieve better environment and sustainability due to high exergetic efficiency. By the way, economic and technical issues of the storage and transportation of the hydrogen can find a proper solution if the hydrogen production reaction of the Boron thermochemical water splitting cycle takes place on-board of a vehicle. 相似文献
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Farrukh Khalid Ibrahim Dincer Marc A. Rosen 《International Journal of Hydrogen Energy》2018,43(41):18783-18789
A new three step high temperature Cu-Cl thermochemical cycle for hydrogen production is presented. The performance of the proposed cycle is investigated through energy and exergy approaches. Furthermore, the effects of various parameters, such as the temperatures of the steps of the cycle and power plant efficiency, on various energy and exergy efficiencies are assessed with parametric studies. The results show that the exergy and energy efficiencies of the proposed cycle are 68.3% and 32.0%, respectively. In addition, the exergy analysis results reveal that the hydrogen production step has the maximum specific exergy destruction with a value of 150.9 kJ/mol. The results suggest that proposed cycle may provide enhanced options for high temperature thermochemical cycles by improving thermal management without causing a sudden temperature jump/fall between the hydrogen production step and other steps. 相似文献
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In this paper, exergy method is applied to analyze the ejector expansion Joule–Thomson (EJT) cryogenic refrigeration cycle. The exergy destruction rate in each component of the EJT cycle is evaluated in detail. The effect of some main parameters on the exergy destruction and exergetic efficiency of the cycle is also investigated. The most significant exergy destruction rates in the cycle are in the compressor and ejector. The ejector pressure ratio and compressor isothermal efficiency have a significant effect on the exergetic efficiency of the EJT cycle. The exergy analysis results show the EJT cycle has an obvious increase in the exergetic efficiency compared to the basic Joule–Thomson refrigeration cycle. A significant advantage from the use of the ejector is that the total exergy destruction of the EJT cycle can be reduced due to much more decreasing of the exergy destruction rates in the compressor and expansion valve. The exergy analysis also reconfirms that applying an ejector is a very important approach to improve the performance of the Joule–Thomson cryogenic refrigeration cycle. 相似文献
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In this work exergetical performance analysis is carried out based on the second law of thermodynamics for organic flash cycle(OFC) using a two-phase expander instead of throttle expansion in order to recover efficiently finite thermal reservoirs.The exergy destructions(anergies) at various components of the system are theoretically investigated as well as the exergy efficiency.Results show that the anergy of heat exchanger or two-phase expander decreases while the anergy of throttle valve increases with increasing flash temperature,and the exergy efficiency has an optimum value with respect to the flash temperature.Under the optimal conditions with respect to the flash temperature,exergy efficiency increases with the heating temperature and the component having the largest exergy destruction varies with the flash temperature or heating temperature. 相似文献
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In this paper, exergy method is applied to analyze the gas turbine cycle cogeneration with inlet air cooling and evaporative aftercooling of the compressor discharge. The exergy destruction rate in each component of cogeneration is evaluated in detail. The effects of some main parameters on the exergy destruction and exergy efficiency of the cycle are investigated. The most significant exergy destruction rates in the cycle are in combustion chamber, heat recovery steam generator and regenerative heat exchanger. The overall pressure ratio and turbine inlet temperature have significant effect on exergy destruction in most of the components of cogeneration. The results obtained from the analysis show that inlet air cooling along with evaporative aftercooling has an obvious increase in the energy and exergy efficiency compared to the basic gas turbine cycle cogeneration. It is further shown that the first-law efficiency, power to heat ratio and exergy efficiency of the cogeneration cycle significantly vary with the change in overall pressure ratio and turbine inlet temperature but the change in process heat pressure shows small variation in these parameters. 相似文献
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D. H. Johnson 《Energy》1983,8(12):927-946
We develop a fomula here to compute the maximum amount of work which can be extracted from a given combined mass of warm and cold ocean water (a quantity called the exergy of the ocean thermal resource). We then compare the second-law efficiencies of various proposed ocean thermal energy conversion power cycles to determine which best utilizes the exergy of the ocean thermal resource. The second-law efficiencies of the multicomponent working fluid cycle, the Beck cycle, and the open and closed single- and multiple-stage Rankine cycles are compared. These types of OTEC power plants are analyzed in a consistent manner, which assumes that all deviations from a plant making use of all the exergy (one with a second-law efficiency of 100%) occur because of irreversible transfer of heat across a finite temperature difference. Conversion of thermal energy to other forms is assumed to occur reversibly. The comparison of second-law efficiencies of various OTEC power cycles shows that the multistage Rankine open cycle with just three stages has the potential of best using the exergy of the ocean thermal resource. 相似文献
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The selection of working fluid and working conditions of the Organic Rankine Cycle (ORC) has a great effect on the system operation, and its energy efficiency and impact on the environment. The main purpose of this study is to develop a procedure to compare capabilities of working fluids when they are employed in solar Rankine cycles with similar working conditions. The Refprop 8.0 database with 117 organic fluids has been considered as the reference in this study. A procedure to compare ORC working fluids based on their molecular components, temperature–entropy diagram and fluid effects on the thermal efficiency, net power generated, vapor expansion ratio, and exergy efficiency of the Rankine cycle has been proposed. Fluids with the best cycle performance have been recognized in two different temperature levels within two different categories of fluids: refrigerants and non-refrigerants. Based on categories of solar collectors, 11 fluids have been suggested to be employed in solar ORCs that use low or medium temperature solar collectors. Collector efficiency improvement and use of the regenerative ORC instead of the basic cycle reduce irreversibility of a solar ORC. Calculation results show that for selected fluids, the theoretical limits for irreversibility reduction and exergy efficiency enhancement through collector efficiency improvement are 35% and 5% respectively, when the collector efficiency increases from 70% to 100%. The effect of regeneration on the exergy efficiency of the cycle is fluid dependent while the effect of collector efficiency improvement on the exergy efficiency of the cycle is nearly independent of fluid type. At the two temperature levels studied, higher molecular complexity results in more effective regenerative cycles except for Cyclohydrocarbons. 相似文献
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《International Journal of Hydrogen Energy》2021,46(56):28370-28386
One of the essential steps to design energy conversion-based systems is choosing an efficient working fluid under the design goals to access stable products with high efficiency and overcome environmental issues. In this regard, the current paper is motivated to devise and evaluate a novel geothermal-driven multigeneration system under the effect of various working fluids. The proposed system consists of a flash-binary geothermal power plant, an organic flash cycle (OFC), a power/cooling subsystem (an organic Rankine cycle (ORC) and a thermoelectric generator incorporated with a compression refrigeration cycle), and freshwater and hydrogen production units utilizing a humidification-dehumidification desalination unit and a low-temperature electrolyzer. Considering the design potential of the OFC and ORC, four different environmentally-friendly working fluids, i.e., R123 and R600 in the OFC and R1234yf and R1234ze(e) in the ORC are selected and classified in four groups to introduce the best one, under the energy, exergy, and economic (3E analysis) approaches. Also, the whole system is optimized through a genetic algorithm, respecting the optimal solution for the energy efficiency and unit exergy cost of the products. According to the results, R123/R1234ze(e) shows the highest cooling, hydrogen, freshwater production rates, and energy efficiency. Likewise, the maximum power generation and exergy efficiency belong to R600/R1234ze(e). Moreover, R600/R1234yf has the lowest unit exergy cost of products. 相似文献