内可逆回热式燃气轮机热电联产装置的(火用)经济性能优化

应用有限时间热力学方法,研究了恒温热源条件下内可逆回热式燃气轮机热电联产装置的(火用)经济性能,导出了利润率及(火用)效率的解析式.利用数值计算方法,以利润率为目标,对热导率的分配和压比的选取进行了优化,研究了最优利润率及相应(火用)效率特性,并分析了各种联产设计参数对联产优化性能的影响.改进了以往文献中热量(火用)的计算方法,发现了存在最佳的用户侧温度.     

GAX循环的α-h图热力学分析

本文分别对单级氨水吸收式制冷循环和GAX循环进行了计算机模拟,在热源温度TH为120℃、TM为25℃、TL为5℃的情况下,两个循环的制冷系数分别为0.589和0.776,GAX循环高出31.8%。(火用)效率分别为15.4%和27.4%,GAX循环高出77.9%。在α-h图上别对两个循环的热力学结构进行了比较分析,认为循环的改进取决于热机子循环的热力学完善程度,GAX循环与单级循环内部的热泵子循环的(火用)需求是相同的,只是由于GAX循环改善了热机子循环的过程耦合结构,减少了(火用)的消耗而获得了整个循环的增益。     

结合ORC和ARC的中温余热回收系统

中温余热回收过程中传热温差大,系统(火用)效率较低,本文提出一种结合有机朗肯循环和单效吸收式制冷系统的中温烟气余热回收系统。利用热力学第一定律和第二定律对系统建立了数学模型,分析了新系统中有机朗肯循环蒸发温度、冷凝温度等参数对系统性能的影响。同时对系统各主要部件进行了(火用)分析,并与双效溴化锂吸收式制冷系统进行了比较,通过T-Q图分析了新系统及参考系统的换热过程。结果表明新系统的(火用)损失从139.19 kW降低到93.18 kW,(火用)损失减少机理在于换热温差降低。     

水煤浆与干粉给料方式两种IGCC系统的(火用)分析

通过将煤气化过程与联合循环系统相结合,IGCC成为目前最有发展前途的洁净煤技术之一.但以往对IGCC系统的研究多集中联合循环或气化过程本身,而忽略了气化效率对系统整体性能的影响.为揭示气化过程与系统性能之间联系,本文对Texaco与Shell公司的两个IGCC系统实例分别进行了流程模拟和(火用)分析,并着重从热力学角度比较了系统煤气化部分的差异对系统整体性能的影响,得出结论:Shell煤气化技术与Texaco煤气化技术相比,气化过程的(火用)损失相对减小15%,冷煤气效率提高2.6个百分点,系统热转功效率上升2.1个百分点.本文研究成果为IGCC系统进一步改进提供了热力学基础理论支撑.     

涡流管性能的热力学分析

涡流管是一种新型的能量分离装置,热力学参数和几何参数对其的性能影响很大。该文依据热力学第一、第二定律,建立了涡流管能量分离过程热力学模型,将不可逆过程可用能损失归结为热量火用收益和压力损失两部分,获得了一种基于热力学火用分析的涡流管性能优化新途径。结合不同进气压力、喷嘴数和冷端出口直径的涡流管能量分离性能实验,得到上述诸因素对涡流管能量分离过程中火用变化的影响,通过对能量分离过程中热量火用收益和压力损失的比较,实现了涡流管能量分离性能的优化设计。     

基于实际换热的ORC亚/跨临界综合评价

本文以有机朗肯循环(ORC)跨临界与亚临界工质换热特性最新研究成果为基础,采用热力学指标热源回收(火用)效率,以及经济学中的净现值(NPV)概念,结合换热面积分析,建立了考虑实际换热情况的热力学及经济性模型,更合理、更全面地对亚临界循环与跨临界循环的热力学性能和经济性进行了统一分析,为工程实际中亚临界和跨临界的选择提供...     

混合制冷剂循环液化天然气流程(火用)分析

带丙烷预冷的混合制冷剂循环液化天然气流程具有高效及流程相对简单的优点.本文在对流程进行热力学分析的基础上,对流程进行(火用)分析.计算了流程中各设备的(火用)损失,计算结果表明,压缩机的(火用)损失约占整个流程(火用)损失的50%,换热器的(火用)损失约占总(火用)损失的26%.本文还分析了产生(火用)损失的原因,提出降低(火用)损失的措施.     

多元混合工质内复叠节流结合涡流管复合循环的热力分析

针对多元混合工质内复叠节流循环和涡流管的特点 ,提出了一种新的复合循环流程 ,以期达到液氮以下的制冷温度。建立了适当的涡流管热力学模型 ,采用火用分析方法对复合制冷循环各部件进行了分析。在相同的条件下 ,对复合循环和内复叠循环的热力特性进行对比 ,结果表明 ,采用复合循环可以提高整个循环的火用效率 ,完全可能达到液氮以下的制冷温度     

新型氨吸收式动力/制冷复合循环的热力学分析

在Kalina循环的基础上,本文提出了一个改进的吸收式动力/制冷复合循环,在logp-T图上分析了该循环的热力学原理,基于综合热效率η和（火用）效率ψ两个评价指标,通过模拟计算,研究了新循环的热力学原理和能量特性,发现新循环与Kalina循环的η分别为19.50％和14.54％,新循环比Kalina循环提高34.10％;两个循环的ψ分别为31.60％和31.19％。本文还研究了新循环的精馏塔进料浓度、透平出口压力对η和ψ的影响。     

工质变比热对不可逆Otto循环性能的影响

用有限时间热力学的方法分析空气标准Otto循环,由数值计算给出了存在不可逆损失和工质变比热时循环功率与压缩比、效率与压缩比以及功率和效率的特性关系,分析了工质变比热对不可逆Otto循环性能的影响特点,通过分析可知工质变比热特性对不可逆Otto循环性能有较大影响,在实际循环分析中应该予以考虑,本文所得结果对实际内燃机的设计有一定的指导意义。     

Exergy-Based Multi-Objective Optimization of an Organic Rankine Cycle with a Zeotropic Mixture

In this paper, the performance of an organic Rankine cycle with a zeotropic mixture as a working fluid was evaluated using exergy-based methods: exergy, exergoeconomic, and exergoenvironmental analyses. The effect of system operation parameters and mixtures on the organic Rankine cycle’s performance was evaluated as well. The considered performances were the following: exergy efficiency, specific cost, and specific environmental effect of the net power generation. A multi-objective optimization approach was applied for parametric optimization. The approach was based on the particle swarm algorithm to find a set of Pareto optimal solutions. One final optimal solution was selected using a decision-making method. The optimization results indicated that the zeotropic mixture of cyclohexane/toluene had a higher thermodynamic and economic performance, while the benzene/toluene zeotropic mixture had the highest environmental performance. Finally, a comparative analysis of zeotropic mixtures and pure fluids was conducted. The organic Rankine cycle with the mixtures as working fluids showed significant improvement in energetic, economic, and environmental performances.     

Energy,Exergy, Exergoeconomic and Exergoenvironmental Impact Analyses and Optimization of Various Geothermal Power Cycle Configurations

Energy, exergy, and exergoeconomic evaluations of various geothermal configurations are reported. The main operational and economic parameters of the cycles are evaluated and compared. Multi-objective optimization of the cycles is conducted using the artificial bee colony algorithm. A sensitivity assessment is carried out on the effect of production well temperature variation on system performance from energy and economic perspectives. The results show that the flash-binary cycle has the highest thermal and exergy efficiencies, at 15.6% and 64.3%, respectively. The highest generated power cost and pay-back period are attributable to the simple organic Rankine cycle (ORC). Raising the well-temperature can increase the exergy destruction rate in all configurations. However, the electricity cost and pay-back period decrease. Based on the results, in all cases, the exergoenvironmental impact improvement factor decreases, and the temperature rises. The exergy destruction ratio and efficiency of all components for each configuration are calculated and compared. It is found that, at the optimum state, the exergy efficiencies of the simple organic Rankine cycle, single flash, double flash, and flash-binary cycles respectively are 14.7%, 14.4%, 12.6%, and 14.1% higher than their relevant base cases, while the pay-back periods are 10.6%, 1.5% 1.4%, and 0.6% lower than the base cases.     

Green and double-win planning for IP over WDM optical networks

Saving the electrical requirements of network operators around the world makes power costs show a continuously decreasing trend. However, reducing the power costs is not only one way of gaining the marginal profit, a network operator also needs providing high-level quality of service (QoS), as well as employs effective strategies of pricing and hybrid grooming (i.e., integration of traffic grooming with an optical bypass) to make more users wish to pay the expense for their applications. In the final, users enjoy their services meanwhile operators obtain high profit in a power-efficient way, i.e., “double-win”. Accordingly, we propose the fast sub-optimal heuristics including Single-hop and Power-efficient Grooming algorithm based on Game theory (SPG2) as well as Multi-hop and Power-efficient Grooming algorithm based on Game theory (MPG2). Simulation results demonstrate that, compared with SPG2, MPG2 has the better comprehensive performance of both power efficiency and double-win between user and network operator in IP over WDM networks.     

Conversion of low-grade heat from FCC absorption-stabilization system to electricity by organic Rankine cycles: Simulation and optimization

In this study, the organic Rankine cycle (ORC) is applied to be integrated into the fluid catalytic cracking (FCC) absorption-stabilization system to extract and convert the low-grade process heat to electricity. This newly integrated system is simulated by the Aspen Plus software. For the simulation, eleven different dry and isentropic working fluids are selected to investigate the energy conversion performance of the incorporated ORC system. It is found that, the performance depends highly on the operational parameters, such as mass flow rate and the evaporation pressure of the working fluids, outlet temperature of the process stream. After optimization, the working fluids R124 and R227ea are determined to be the best candidates due to their highest output net work in HCT (high critical temperature) and LCT (low critical temperature) working fluids, respectively. A further optimization has been conducted based on the economic evaluations (i.e., electricity production cost (EPC) and total annual profit (TAP)). Results show that, for the HCT working fluids, the use of working fluid of R245fa allows the EPC to be the lowest, while the application of R124 obtains the highest TAP. For the LCT working fluids, R227ea is the best choice due to its lowest EPC and highest TAP.     

以低温热为热源的再沸器(火用)经济优化与传热强化

精馏塔再沸器是炼油、化工、轻工等行业中非常重要的换热设备,这种再沸器的优化和传热强化对热能的优化利用具有重要意义.本文运用经济学方法和传热强化技术,对以低温热为热源的再沸器进行优化设计,建立了同时考虑传热损、流动损和传热强化的再沸器经济优化目标函数和约束条件.并给出了应用实例.     

Enhanced bimodal distributions facilitate the learning of second language vowels

This study addresses the questions of whether listening to a bimodal distribution of vowels improves adult learners' categorization of a difficult L2 vowel contrast and whether enhancing the acoustic differences between the vowels in the distribution yields better categorization performance. Spanish learners of Dutch were trained on a natural bimodal or an enhanced bimodal distribution of the Dutch vowels /ɑ/ and /a?/, with the average productions of the vowels or more extreme values as the endpoints respectively. Categorization improved for learners who listened to the enhanced distribution, which suggests that adults profit from input with properties similar to infant-directed speech.     

考虑环境成本的能量系统(火用)经济学分析模型

随着可持续发展战略的实施,对传统的(火用)经济学提出了新的挑战。本文在传统佣经济学分析的基础上,将环境成本引入到(火用)经济学分析中,首先提出了“广义子系统”的概念,建立了包括(火用)环境成本平衡在内的各种平衡方程;在系统生产结构的描述中,将系统中的(火用)流划分成外界输入(火用)流、内部(火用)流以及向外界输出(火用)流三类,最终建立了以矩阵形式表示的各种平衡方程,用于求解系统中各股(火用)流的单位(火用)成本、单位(火用)经济成本、单位环境成本、单位综合(火用)经济成本等性能参数。最后针对某国产200MW机组进行了实例计算。     

Modeling of price and profit in coupled-ring networks

We study the behaviors of magnetization, price, and profit profiles in ring networks inthe presence of the external magnetic field. The Ising model is used to determine thestate of each node, which is mapped to the buy-or-sell state in a financial market, where+1 is identified as the buying state, and ?1 as the selling state. Price and profit mechanisms are modeled basedon the assumption that price should increase if demand is larger than supply, and itshould decrease otherwise. We find that the magnetization can be induced between two ringsvia coupling links, where the induced magnetization strength depends on the number of thecoupling links. Consequently, the price behaves linearly with time, where its rate ofchange depends on the magnetization. The profit grows like a quadratic polynomial withcoefficients dependent on the magnetization. If two rings have opposite direction of netspins, the price flows in the direction of the majority spins, and the network with theminority spins gets a loss in profit.     

The string prediction models as invariants of time series in the forex market

In this paper we apply a new approach of string theory to the real financial market. The models are constructed with an idea of prediction models based on the string invariants (PMBSI). The performance of PMBSI is compared to support vector machines (SVM) and artificial neural networks (ANN) on an artificial and a financial time series. A brief overview of the results and analysis is given. The first model is based on the correlation function as invariant and the second one is an application based on the deviations from the closed string/pattern form (PMBCS). We found the difference between these two approaches. The first model cannot predict the behavior of the forex market with good efficiency in comparison with the second one which is, in addition, able to make relevant profit per year. The presented string models could be useful for portfolio creation and financial risk management in the banking sector as well as for a nonlinear statistical approach to data optimization.     

Relationships between temperature differences in heat exchangers of heat transformation devices

The temperatures which are present in a heat transformation device play a very important part: at first, the temperatures determine the maximum performance or efficiency of the cycle via the first and second laws of thermodynamics. Secondly, the temperatures determine the heat transfer area which is required to put a given heat flux through the system. Consequently, they relate power to investment cost. In order to elaborate further on these interdependencies, in this paper basic relationships between technically and thermodynamically relevant temperatures, as they are present in the heat exchangers, are being derived. To this end, we will define several temperature differences as usual: the temperature glide, the driving mean temperature difference and the thermodynamic or entropic mean temperature difference. The logarithmic temperature mean is significant for determining the heat transfer. It will be shown that, as long as the temperature gradient between external and internal fluids is larger than the difference in glide of both fluids, the log-mean can be substituted by the difference of the arithmetic mean temperatures. Consequently, it is almost identical to the entropic temperature difference. The entropic temperature difference is a measure of efficiency whereas the logarithmic temperature difference is a measure of first cost. As both temperature differences deviate only marginally from each other in most technical applications it will easily be possible to establish a relationship between performance and investment.