有机朗肯循环系统损实验研究

可再生能源及余热发电是低品位能源一种高效利用模式,有机朗肯循环发电系统比水蒸气发电机组更适用于低温热源发电。设计并搭建了热源功率为100kW的导热油模拟热源的有机朗肯循环发电系统,研究冷热源参数恒定不变、膨胀机转速变化时发电系统主要设备的损失和所占比例。主要结论为:当膨胀机转速增加时,蒸发器、膨胀机和工质泵的损失增大,而冷凝器设备损失减少;定量分析膨胀机转速为3000r/min时,蒸发器损失为51.8%,占有机朗肯循环系统损失的1/2以上,工质泵损失最小,仅为1.8%。     

低温余热有机朗肯循环发电系统热经济性分析

针对工业中排放的低温烟气,建立有机朗肯循环发电系统的热经济分析模型,分析蒸发压力、热源温度及蒸发器最小传热温差对系统经济性能的影响。分析结果表明:热源温度为140℃,循环采用R123的经济性最佳,相应的发电成本与动态投资回收期分别为0.142元(/kW.h)与3.68年。余热发电系统存在一个经济性最高的蒸发压力,不同工质对应的最佳蒸发压力也不同。蒸发器内最小传热温差为15℃时,系统的经济性较好。烟气温度在100～180℃时,系统采用R123的投资回收期最短,而烟气温度高于180℃时,R141b的经济性更高;不宜采用有机朗肯循环发电技术回收温度低于100℃的低温烟气。     

有机工质低温余热发电系统多目标优化设计

针对现有有机朗肯循环单目标优化设计的局限性,从热力性、经济性等多方面对有机工质低温余热发电系统进行多目标优化设计.以系统效率最大和总投资费用最小为目标函数,选取透平进口温度、透平进口压力、余热锅炉节点温差、接近点温差和冷凝器端差等5个关键热力参数作为决策变量,利用非支配解排序遗传算法(NSGA-II)分别对采用R123、R245fa和异丁烷的有机工质余热发电系统进行多目标优化,获得不同工质的多目标优化的最优解集(Pareto最优前沿),并采用理想点辅助法从最优解集中选择出最优解及相应的系统最佳热力参数组合.结果表明:在给定余热条件下,从热力性能和经济性两方面考虑,R245fa是最优的有机工质,从多目标优化的最优解集中选择出的最佳效率为10.37%,最小总投资费用为455.84万元.     

有机工质低温余热发电系统多目标优化设计

针对现有有机朗肯循环单目标优化设计的局限性,从热力性和经济性等多方面对有机工质低温余热发电系统进行多目标优化设计.以系统效率最大和总投资费用最小为目标函数,选取透平进口温度、透平进口压力、余热锅炉节点温差、接近点温差和冷凝器端差等5个关键热力参数作为决策变量,利用非支配解排序遗传算法(NSGA-II)分别对采用R123、R245fa和异丁烷的有机工质余热发电系统进行多目标优化,获得不同工质多目标优化的最优解集(Pareto最优前沿),并采用理想点辅助法从最优解集中选择出最优解及相应的系统最佳热力参数组合.结果表明:在给定余热条件下,从热力性能和经济性两方面考虑,R245fa是最优的有机工质,从多目标优化的最优解集中选择出的最佳效率为10.37%,最小总投资费用为455.84万元.     

太阳能超临界有机朗肯循环的工质选择和性能分析

选取R123、R134a、R152a、R22和R245fa 5种有机工质作为候选工质进行太阳能超临界有机朗肯循环的计算和分析。结果表明:当膨胀机出口工质过热度一定时,太阳能超临界有机朗肯循环的热效率高于亚临界工况,且R123在系统热效率方面表现出比其他工质更加明显的优势,是一种较理想的有机工质。以R123为例,蒸发器出口温度一定时,随着蒸发压力的升高,有机朗肯循环的工质流量不断增大。蒸发压力一定时,随着蒸发器出口温度的升高,工质流量不断减小,循环热效率先增后减,存在一个最佳的蒸发器出口温度,此时循环热效率最大。     

浅析有机朗肯循环研究现状

有机朗肯循环(ORC)是国内外学者公认的对中低品位能源回收的有效技术,能很好地缓解人类与能源之间的矛盾。有机朗肯循环主要由蒸发器、膨胀机、发电机、冷凝器、工质泵组成。研究者从各个方面对如何提高有机朗肯循环系统的效率进行研究。在对工质的研究中主要包括纯工质和混合工质,其中纯工质主要是研究其与热源匹配问题,而混合工质主要是对混合比的探究以及窄点温差的研究。在有机朗肯循环系统中,板式蒸发器是最理想的蒸发器。新型冷凝器可以获得更好的冷却效果和经济性。工质泵的腐蚀导致流量减少是研究重点,通过增加前置泵或选用往复泵都能有效改善这一问题。膨胀机是系统的关键部件,涡旋式膨胀机的特点使其最适合于小型ORC系统,而螺杆式膨胀机是目前最成熟的膨胀机。目前对有机朗肯循环系统的研究还存在着许多问题,如研究大多都是偏理论的,具体的实验研究太少;对单一部件单一目标的研究过多,对整个系统的研究相对较少。     

基于分析的再热/抽气回热/内回热有机朗肯循环的优化

提出一种具有再热/抽气回热/内回热的联合有机朗肯循环(CRORC)系统。该系统以低温热能作为驱动热源,以R245fa为循环工质。基于分析,对CRORC系统进行了优化。蒸发器、冷凝器、膨胀机II是CRORC系统损失的主要来源,随着抽气压力及再热压力的升高,CRORC系统的效率呈现先增大后减小的趋势,并存在最佳抽气压力/再热压力组合,使系统效率最高。相对于基本回热/抽气回热以及抽气回热/内回热结合的有机朗肯循环,CRORC有更高的效率。     

基于低品位余热驱动的正逆耦合空调系统性能分析

针对低品位余热的利用,将有机朗肯系统与复叠式制冷系统耦合,建立了热力学模型;采用R141b作为朗肯循环系统制冷工质,分别采用R22/R23、R404A/R23、R290/R744、R717/R744四种工质对作为复叠式制冷系统高低温级循环的制冷工质;基于EES软件编写了循环性能计算程序,研究了低温级冷凝温度T_(10)、低温级蒸发温度T_e、蒸发冷凝传热温差ΔT对系统性能COPs以及高低温级质量流量比G的影响,并以COPs与G为评价指标选出最佳工质。结果表明系统的COPs会随着低温级冷凝温度的升高而先增大后减小,并存在一个最佳值;系统COPs随着低温级蒸发温度的升高而增大,随着蒸发冷凝传热温差的增大而减小;高低温级质量流量比随着低温级冷凝温度的增大而减小;R717/R744最适合作为有机朗肯-复叠制冷系统复叠制冷部分工质。     

电石炉烟气余热回收双回路ORC系统性能分析

有机朗肯循环(ORC)系统在回收余热方面具有较大优势.本文采用双回路有机朗肯循环(DORC)系统回收电石炉烟气余热.对比了不同工质组合、不同循环结构下,高温循环的蒸发温度与冷凝温度对系统输出功率、效率和发电成本的影响.结果表明:与基础DORC相比,回热式DORC系统性能更佳,其中以甲醇与R123工质组合的系统净功率与效率最大,水作为高温循环工质在无回热的基础DORC系统中经济性优势明显.恒定热源条件下增大高温循环蒸发温度,对所有工质组合下同性能均有明显改善,增大高温循环冷凝温度则降低系统性能.     

钢铁企业中低温烟气发电系统的比较和优化

为高效利用钢铁厂200～450℃烟气余热,利用EES软件模拟计算了水蒸气朗肯循环(SRC)4种有机朗肯循环(ORC)和水蒸气-有机物联合双循环(S-ORC)的热效率、火用效率和单位质量工质的发电能力。通过比较各发电系统的性能,探讨了低温发电系统的优化措施。为进一步利用ORC系统透平机乏汽余热,针对300℃以上的热源设计了梯级有机朗肯循环(CORC)。综合考虑各发电系统的性能,得出:对于200～300℃的烟气,可采用以R141b为工质的ORC发电系统;对于300～450℃的烟气,可采用CORC发电系统。由于S-ORC的热效率、火用效率、发电功率比传统SRC的高,且能有效减小工质在冷凝器的负压,对于450℃以上的热源,可用S-ORC代替传统的SRC。     

Performance analysis of organic Rankine cycle based on location of heat transfer pinch point in evaporator

The location of heat transfer pinch point in evaporator is the base of determining operating parameters of organic Rankine cycle (ORC). The physical mathematical model seeking the location of pinch point is established, by which, the temperature variations both of heat source and working fluid with UA can be obtained. Taking heat source with inlet temperature of 160 °C as example, the matching potentials between heat source and working fluid are revealed for subcritical and supercritical cycles with the determined temperature difference of pinch point. Thermal efficiency, exergy efficiency, work output per unit area and maximum work outputs are compared and analyzed based on the locations of heat transfer pinch point either. The results indicate that supercritical ORC has a better performance in thermal efficiency, exergy efficiency and work output while outlet temperature of heat source is low. Otherwise, subcritical performs better. Small heat transfer coefficient results in low value of work output per unit area for supercritical ORC. Introduction of IHX may reduce the optimal evaporating pressure, which has a great influence on heat source outlet temperature and superheat degree. The analysis may benefit the selection of operating parameters and control strategy of ORC.     

新型城市低温地热冷热电联产系统热力性能分析

为节约及合理利用能源,提高城市能量总能系统利用率,基于有机朗肯循环(ORC)和冷热电联产(CCHP),提出了一种新型的城市低温地热冷热电联产系统(以下简称ORC-CCHP系统)。根据热力学第一、第二定律,建立了热力学模型,编写计算机程序进行了系统的热力性能分析。结果表明:采用R245fa、LiBr溶液作为ORCCCHP系统循环工质时,选择窄点温差较小蒸发器可获得更高火用效率;增加太阳能集/蓄热系统,提高热流参数,减小换热温差,可进一步提升系统热力学性能;系统分别采用5种不同有机工质时,R236fa使系统的热力性能达到最佳,并在蒸发压力为0. 62 MPa、窄点温差为0 K时,ORC-CCHP系统获得最大净输出功为1 948 kW,系统火用效率为19. 28%,系统火用效率最高值为85. 78%。     

Energetic and exergetic analysis of waste heat recovery from a microturbine using organic Rankine cycles

This article examines the exhaust waste heat recovery potential of a microturbine (MT) using an organic Rankine cycle (ORC). Possible improvements in electric and exergy efficiencies as well as specific emissions by recovering waste heat from the MT exhaust gases are determined. Different dry organic working fluids are considered during the evaluation (R113, R123, R245fa, and R236fa). In general, it has been found that the use of an ORC to recover waste heat from MTs improves the combined electric and exergy efficiencies for all the evaluated fluids, obtaining increases of an average of 27% when the ORC was operated using R113 as the working fluid. It has also been found that higher ORC evaporator effectiveness values correspond to lower pinch point temperature differences and higher exergy efficiencies. Three different MT sizes were evaluated, and the results indicate that the energetic and exergetic performance as well as the reduction of specific emissions of a combined MT‐ORC is better for small MT power outputs than for larger MTs. This article also shows how the electric efficiency can be used to ascertain under which circumstances the use of a combined MT‐ORC will result in better cost, primary energy consumption, or emission reduction when compared with buying electricity directly from electric utilities. Copyright © 2012 John Wiley & Sons, Ltd.     

Performance assessment and optimization of a biomass-based solid oxide fuel cell and micro gas turbine system integrated with an organic Rankine cycle

Rice straw is a potential energy source for power generation. Here, a biomass-based combined heat and power plant integrating a downdraft gasifier, a solid oxide fuel cell, a micro gas turbine and an organic Rankine cycle is investigated. Energy, exergy, and economic analyses and multi-objective optimization of the proposed system are performed. A parametric analysis is carried out to understand the effects on system performance and cost of varying key parameters: current density, fuel utilization factor, operating pressure, pinch point temperature, recuperator effectiveness and compressors isentropic efficiency. The results show that current density plays the most important role in achieving a tradeoff between system exergy efficiency and cost rate. Also, it is observed that the highest exergy destruction occurs in the gasifier, so improving the performance of this component can considerably reduce the system irreversibility. At the optimum point, the system generates 329 kW of electricity and 56 kW of heating with an exergy efficiency of 35.1% and a cost rate of 10.2 $/h. The capability of this system for using Iran rice straw produced in one year is evaluated as a case study, and it is shown that the proposed system can generate 6660 GWh electrical energy and 1140 GWh thermal energy.     

R245fa有机朗肯循环余热发电系统火用分析

以低品位热能驱动的有机朗肯循环发电系统,是实现将低品位热能转变为电能,进而提高热力系统总体热效率,降低污染排放的有效途径之一。本文建立了低品位热能发电系统火用分析模型,对以R245fa为工质的温度低于383.15 K的低品位热能有机朗肯循环余热发电系统进行了火用分析,得到了各环节的能量转换效率并确定了对系统性能影响最大的环节;通过改变蒸发器和冷凝器的压降和传热系数值,分析了主要换热设备的设计和运行性能参数对系统火用效率、热效率和发电量的影响趋势,提出了低品位热能发电系统的优化方向。     

Thermodynamic,exergoeconomic and exergoenvironmental analyses and optimization of a solid oxide fuel cell-based trigeneration system

This study proposes a trigeneration system based on solid oxide fuel cell (SOFC) for generating power, cooling and heating simultaneously. The system mainly contains a SOFC, a gas turbine (GT), an organic Rankine cycle (ORC), a steam ejector refrigerator (SER) and a heat exchanger. The thermodynamic, exergoeconomic and exergoenvironmental models of proposed trigeneration system are developed, and the effects of design parameters on system performances are analyzed. The results indicate that the system average product cost and environmental impact per unit of exergy increase with SOFC inlet temperature and working pressure, the pinch point temperature difference and evaporating pressure of Generator, while decrease with the current density of fuel cell. Finally, optimization is performed to achieve the optimal exergy-based performance. It is revealed that though the system exergy efficiency is decreased by 7.64% after optimization, the system average product cost and environmental impact per unit of exergy are significantly reduced.     

低温地热发电有机朗肯循环的优化

采用(火用)分析方法及PR状态方程,建立了低温地热发电有机朗肯循环的工质优选及主要参数优化热力学方法.比较计算了以10种干流体有机工质为循环工质的低温地热发电有机朗肯循环的输出功率、(火用)效率及其余主要热力性能.结果表明,低温地热发电有机朗肯循环的性能极大地受工质的物性及蒸发温度的影响.总体来看,随着工质临界温度的升...     

Thermal matching performance of a geothermal ORC system using zeotropic working fluids

The thermal matching performance analysis is conducted for a geothermal organic Rankine cycle system using zeotropic mixtures as working fluids. The constant isentropic efficiency is replaced by internal efficiency of an axial flow turbine with given size for each condition, and the zeotropic mixtures of isobutane and isopentane is used as working fluids of the organic Rankine cycle, in order to improve thermal match in evaporator and condenser. The results showed the use of zeotropic mixtures leads to the prominent thermodynamic first law and second law efficiencies, especially at high minimum temperature difference in evaporator (Δt₁), and there exists an optimal thermal performance at some certain mole fraction of isopentane in zeotropic mixtures (x) and Δt₁. The geothermal organic Rankine cycle with x of 0.2 and Δt₁ of 16 K shows the maximal thermodynamic first law and second law efficiency in this research. The geothermal organic Rankine cycle system using zeotropic mixtures shows the optimal overall thermal performance at some certain x, which is not necessary to be the point with the maximal temperature glide. The use of zeotropic mixtures is not always lead to a high thermal to electricity efficiency compared to the pure working fluid, and its overall net power output of P_ORC is even lower than the pure working fluids compositions at some certain x.     

Multigeneration system exergy analysis and thermal management of an industrial glassmaking process linked with a Cu–Cl cycle for hydrogen production

A multigeneration system for hydrogen production linked with a glassmaking process via thermal management is examined in this study. The exhaust gas is interconnected with a Rankine cycle and the copper-chlorine (Cu–Cl) cycle for hydrogen production. The present system consists of a steam Rankine cycle, Cu–Cl cycle with multistage compression, double-stage organic Rankine cycle, and multi-effect desalination system. A Cu–Cl cycle based on the four-step model is employed with the proposed system. The useful system outputs are electricity, hydrogen, and fresh water. The simulation software packages utilized in the analysis and modeling are Engineering Equation Solver and Aspen Plus. The energy efficiency of the overall system is 36.5% while 38.1% is the exergy efficiency. The parametric studies are conducted to investigate the system performance. In addition, the effects of exhaust gas variables, such as flow rate, temperature, and pressure are examined to investigate the system performance.     

Energy,exergy, and exergoeconomics (3E) analysis and multi-objective optimization of a multi-generation energy system for day and night time power generation - Case study: Dezful city

The present study aimed to investigate a multi-generation energy system for the production of hydrogen, freshwater, electricity, cooling, heating, and hot water. Steam Rankine cycle (SRC), organic Rankine cycle (ORC), absorption chiller, Parabolic trough collectors (PTCs), geothermal well, proton exchange membrane (PEM) electrolyzer, and reverse osmosis (RO) desalination are the main subsystems of the cycle. The amount of exergy destruction is calculated for each component after modeling and thermodynamic analysis. The PTCs, absorption chiller, and PEM electrolyzer had the highest exergy destruction, respectively. According to meteorological data, the system was annually and hourly tested for Dezful City. For instance, it had a production capacity of 13.25 kg/day of hydrogen and 147.42 m³/day of freshwater on 17th September. Five design parameters are considered for multi-objective optimization after investigating objective functions, including cost rate and exergy efficiency. Using a Group method of data handling (GMDH), a mathematical relation is obtained between the input and output of the system. Next, a multi-objective optimization algorithm, a non-dominated sorting genetic algorithm (NSGA-II), was used to optimize the relations. A Pareto frontier with a set of optimal points is obtained after the optimization. In the Pareto frontier, the best point is selected by the decision criterion of TOPSIS. At the TOPSIS point, the exergy efficiency is 31.66%, and the total unit cost rate is 21.9 $/GJ.