Performance Analysis and Optimization of a Series Heat Exchangers Organic Rankine Cycle Utilizing Multi-Heat Sources from a Marine Diesel Engine

Organic Rankine Cycle (ORC) is an effective way to recycle waste heat sources of a marine diesel engine. The aim of the present paper is to analyze and optimize the thermoeconomic performance of a Series Heat Exchangers ORC (SHEORC) for recovering energy from jacket water, scavenge air, and exhaust gas. The three sources are combined into three groups of jacket water (JW)→exhaust gas (EG), scavenge air (SA)→exhaust gas, and jacket water→scavenge air→exhaust gas. The influence of fluid mass flow rate, evaporation pressure, and heat source recovery proportion on the thermal performance and economic performance of SHEORC was studied. A single-objective optimization with power output as the objective and multi-objective optimization with exergy efficiency and levelized cost of energy (LCOE) as the objectives are carried out. The analysis results show that in jacket water→exhaust gas and jacket water→scavenge air→exhaust gas source combination, there is an optimal heat recovery proportion through which the SHEORC could obtain the best performance. The optimization results showed that R245ca has the best performance in thermoeconomic performance in all three source combinations. With scavenge air→exhaust, the power output, exergy efficiency, and LCOE are 354.19 kW, 59.02%, and 0.1150 $/kWh, respectively. Integrating the jacket water into the SA→EG group would not increase the power output, but would decrease the LCOE.     

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.     

Exergy analysis for greener gas turbine engine arrangements

Exergy analysis is a method that uses the conservation of mass and conservation of energy principles together with the second law of thermodynamics for the analysis, design, and improvement of energy and other systems. The exergy method is a useful tool for furthering the goal of more efficient energy-resource use, for it enables the locations, types, and magnitudes of wastes and losses to be identified and meaningful efficiencies to be determined. The exergy analysis of two-shaft gas turbine arrangements is presented and discussed in this paper. Two configurations (in parallel and series free turbine) are presented here and analyzed separately to identify and quantify the energy and exergy losses. Comparison between the two configurations is presented in terms of work output, efficiency, SFC, exergy destruction, and second-law efficiency for the design conditions. The percentage ratio of the exergy destruction in the individual components to total exergy destruction was found maximum in the combustion chambers (above 90%). The second-law efficiency of series configuration is found to be higher than parallel.     

燃气-蒸汽联合循环余热回收系统性能研究

燃气发电是我国城市供电的主要形式之一,针对LNG接收站一体的电厂发电模式进行研究,提出一种新型燃气-蒸汽联合循环热电联供系统,利用超临界CO2布雷顿循环结合有机朗肯循环(ORC)辅助发电,将LNG作为冷源,对烟气余热进行三级利用.通过构建热力学和经济模型,以Aspen Plus软件模拟值为基础,结果表明:在消耗燃料1....     

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.     

Thermodynamic Analysis and Optimization of a Novel Power-Water Cogeneration System for Waste Heat Recovery of Gas Turbine

A power-water cogeneration system based on a supercritical carbon dioxide Brayton cycle (SCBC) and reverse osmosis (RO) unit is proposed and analyzed in this paper to recover the waste heat of a gas turbine. In order to improve the system performance, the power generated by SCBC is used to drive the RO unit and the waste heat of SCBC is used to preheat the feed seawater of the RO unit. In particular, a dual-stage cooler is employed to elevate the preheating temperature as much as possible. The proposed system is simulated and discussed based on the detailed thermodynamic models. According to the results of parametric analysis, the exergy efficiency of SCBC first increases and then decreases as the turbine inlet temperature and split ratio increase. The performance of the RO unit is improved as the preheating temperature rises. Finally, an optimal exergy efficiency of 52.88% can be achieved according to the single-objective optimization results.     

Exergetic efficiency optimization for an irreversible heat pump working on reversed Brayton cycle

This paper deals with the performance analysis and optimization for irreversible heat pumps working on reversed Brayton cycle with constant-temperature heat reservoirs by taking exergetic efficiency as the optimization objective combining exergy concept with finite-time thermodynamics (FTT). Exergetic efficiency is defined as the ratio of rate of exergy output to rate of exergy input of the system. The irreversibilities considered in the system include heat resistance losses in the hot- and cold-side heat exchangers and non-isentropic losses in the compression and expansion processes. The analytical formulas of the heating load, coefficient of performance (COP) and exergetic efficiency for the heat pumps are derived. The results are compared with those obtained for the traditional heating load and coefficient of performance objectives. The influences of the pressure ratio of the compressor, the allocation of heat exchanger inventory, the temperature ratio of two reservoirs, the effectiveness of the hot- and cold-side heat exchangers and regenerator, the efficiencies of the compressor and expander, the ratio of hot-side heat reservoir temperature to ambient temperature, the total heat exchanger inventory, and the heat capacity rate of the working fluid on the exergetic efficiency of the heat pumps are analysed by numerical calculations. The results show that the exergetic efficiency optimization is an important and effective criterion for the evaluation of an irreversible heat pump working on reversed Brayton cycle.     

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...     

低品位热能有机朗肯循环发电技术进展

有机朗肯循环发电技术是基于有机朗肯循环(Organic Rankine Cycle, ORC),利用低沸点有机工质,将低品位的余热资源转换为高品位的电能的先进技术,能够有效提高能源的利用率,减少能源损失。针对工业过程中大量中低温余热受到各种限制难以回收利用难题,全面综述了有机工质朗肯循环低温余热发电技术现状和进展,具体包括循环工质、关键设备、系统优化以及产业应用等。分析表明,该技术可广泛用于地热能、生物质能、太阳热能等领域的低品位热能开发与利用,其产业化推广将有效提高普遍存在的低温余热利用效率。     

混合工质中低温热力循环特性研究

本文从热力学第二定律角度出发,对氨水混合工质中低温动力循环进行了分析。通过与简单蒸汽循环的比较,揭示了混合工质热力循环的特性及本质,指出工质蒸发换热过程的匹配及冷凝过程是混合工质循环高效的关键。为了改善冷凝过程,可采用分馏冷凝系统取代传统的冷凝方式。同时,本文还探讨了一些基本规律,明确了余热回收过程中中低温段换热匹配的重要性     

Comparison of NETD performance of staring and partial-scanning infrared focal plane arrays

The NETD performance of two main configurations are compared: a staring matrix and a partial-scanning system in which a number of vectors, equally-spaced along the image width, are scanning in parallel with a smaller amplitude. The comparison is systematically derived and is valid for both the hybrid and monolithic approaches. The derivation leads to an optimal design procedure for the partial-scanning configuration, based on the optimization of the direct integration time. Several numerical examples relevant to current technologies are presented. In cases characterized by high photon flux levels or 2-D cold shield with low efficiency, the partial-scanning configuration may yield better NETD values compared to a staring system. In addition, it usually has a better spatial resolution and hence may result in superior MRTD performance.     

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.     

正、反向两源热力循环有限时间热力学性能优化的研究进展

有限时间热力学所得结果具有普适性,其研究结果已成为热物理学的一个重要基础.许多学者利用有限时间热力学方法对单级和多级正、反向两热源热力循环最优性能和最优构型进行了大量研究,获得了一些比经典热力学对于工程设计和优化更具有实际指导意义的新结论.综述了利用有限时间热力学理论对不同传热规律下单级和多级正、反向两热源热力循环最优性能和最优构型研究的最新进展,包括不同传热规律下内可逆和不可逆卡诺热机、制冷机和热泵循环的最优性能研究进展,两热源热机、制冷和热泵循环最优构型及多级复杂热力系统最优构型研究进展.     

利用LNG冷能的混合工质中低温热力循环开拓研究

为提高中低温余热回收动力系统性能,本文在常规混合工质热力循环（火用）分析基础上,提出了结合LNG冷能利用的新型混合工质热力循环。通过与LNG的有机结合,混合工质热力循环热效率提高14.5个百分点,（火用）效率达到53.6％。为进一步揭示效率提高的原因,我们比较了常规混合工质热力循环与LNG-混合工质热力循环的（火用）损失变化情况。结果表明:LNG-混合工质热力循环高效的关键在于循环平均放热温度的降低以及工质蒸发过程与冷凝过程换热的合理匹配。而LNG冷能的梯级利用则是系统具有较高（火用）效率的根本原因。     

小型低温余热发电系统性能分析

采用R123作为循环工质,建立了小型低温余热回收系统的理论模型和试验系统,分析了膨胀机转速对容积效率、热电效率、系统不可逆损失的影响.研究结果表明,在试验转速范围内,涡旋膨胀机容积效率随着转速的增加而增加,计算值高于试验值;系统热电效率的计算值随着转速的增加而降低,试验值先增加后减小,并低于理论值;系统不可逆损失随着转...     

Optimal working conditions for an absorption heat transformer—analysis of the H2O/LiBr theoretical cycle

This article studies the optimal working conditions of an absorption heat transformer based on a theoretical cycle using the H₂O/LiBr working pair. The efficiency parameters of the system are discussed and a new parameter, namely the exergetic index, directly related to the exergetic efficiency but more significant for evaluating the performance of the system, is introduced. Distinction is made between energetic optimisation—which involves maximal thermodynamic efficiency—and economic optimisation—for which the knowledge of both the energy and equipment costs are necessary. The existence of two kinds of decision variables related to each type of optimisation are discussed. Four criteria for energetic optimisation are defined from which simple prediction equations are obtained. These equations enable us to predict for a given pair, a range of energetically optimal working conditions, valid for a large number of cold and waste energy source temperatures. Finally, practical applications of the proposed predictions are given.     

有机朗肯循环系统及其透平设计研究

本文对可用于工业低温余热回收的有机朗肯循环(ORC)热力系统进行简述,采用热力学第一定律、热力学第二定律分析ORC热力系统及其效率,并对有机工质动力透平的特点及设计造型进行概述。最后采用F11,R123,R245ca,R600和R600a为工质,设计有机朗肯系统回收某一工业余热,并以R123为工质进行有机工质透平的气动设计、造型设计和CFD模拟计算研究,并对透平进行造型优化。研究表明,以R123为工质的有机朗肯循环系统能有效可靠利用该工业余热,所设计的有机工质透平基本达到设计要求,透平造型的优化设计能有效改善透平叶轮内部流动。     

利用重力增压的新型有机工质热力发电循环

与水蒸气朗肯循环给水泵相比,有机朗肯循环工质泵存在技术难度大、效率低、易气蚀和单位功率成本高等问题。本文提出了一种利用重力增压的新型有机工质热力发电循环,冷凝器出口工质不经过泵而依靠重力增压,然后进入蒸发器气化。分别采用R113、R123和R245fa三种干工质分析了不同蒸发温度和冷凝温度下循环所需的重力增压高度。并基于泵的实验数据,比较了该热力循环与泵增压有机朗肯循环的性能。结果表明,相同工作温度下沸点和密度越高的工质所需的重力增压高度越小。在蒸发温度100℃和冷凝温度50℃时,若采用R113,新型循环所需的重力增压高度为22.2 m,热效率为8.1%,比泵增压循环效率高约0 8%。该重力增压循环显示了应用于热电联供领域的潜力。     

发动机余热利用蒸气动力循环的工质筛选

本文针对汽油发动机余热温度的特点,采用有机Rankine循环(Organic Rankine Cycle,ORC)回收发动机的排气和冷却水废热。利用计算机程序对循环中各主要状态点的热力参数和热力性能进行了理论计算,确定了最佳参数值,进行了有机工质的筛选。最终选定环戊烷和R113作为发动机余热回收利用蒸气动力循环的工质。     

两级中冷回热再热布雷顿热电联产装置的性能

应用有限时间热力学理论和方法建立了恒温热源不可逆两级中冷回热再热布雷顿热电联产装置模型,基于分析的观点,导出了装置无量纲输出率和效率的解析式。在给定总压比的情形下,通过数值计算分别研究了输出率和效率与两个中冷压比和两个再热压比的关系,当总压比变化时,发现输出率和效率对总压比存在最大值,并分别求出了两个相应的最佳的中冷压比和再热压比。分析了回热度、中冷度、再热度、压气机和涡轮机效率、压降损失等特征参数对装置性能的影响。最后发现分别存在最佳的用户侧温度使输出率和效率取得双重最大值。