有机朗肯循环与再热式循环低温热源发电系统热力性能研究

针对120℃以下的低温余热热源,探讨了基本有机郎肯循环发电系统和再热式有机朗肯循环发电系统模型的基本原理.从热力学第一定律角度出发,研究了纯工质R245fa和非共沸混合工质R21/R245fa在基本有机郎肯循环系统中,以及纯工质R245fa在再热式有机郎肯循环系统中,三种形式的有机郎肯循环系统热力性能随蒸发温度的变化情况.与纯工质基本有机郎肯循环系统相比,再热式有机郎肯循环最大可提高系统净输出功7.08％,而混合工质对提高整个系统热力性能具有较大的优势,净输出功和热效率最大可提高4.67％和2.91％.     

不同工况下非共沸混合工质有机朗肯循环系统性能研究

采用MATLAB软件模拟非共沸混合工质在不同冷热源条件下对有机朗肯循环(ORC)系统性能的影响。选取R245fa/R1234ze和R245fa/R600a作为混合工质,热源温度取120和200℃,分别在冷凝露点温度为40℃和冷却水温升为5,10,15℃的工况条件下,利用热力学第一定律和火积理论对系统性能进行分析。结果表明：热源温度为200℃时,R245fa, R1234ze和R600a系统净输出功率分别为89.83,61.87和77.74 kW,使用R245fa系统性能优于其混合工质;热源温度为120℃、固定冷凝露点温度时,混合工质R245fa/R600a(90%∶10%)净输出功率比R245fa和R600a分别提高了27.6%和27%,R245fa/R1234ze(60%∶40%)净输出功率比R245fa和R600a分别提高了26%和20.5%;火积耗散和单位面积做功量与净输出功率变化相反,提高冷却水温升时,增大了系统火积耗散,且流向环境中的火积耗散在总火积耗散中占比增大,导致系统的传热不可逆损失增加。     

车用内燃机变工况下有机朗肯循环系统性能的分析

通过试验和理论研究,得出了一台车用柴油机在全工况范围内可用排气能量的变化规律,据此设计了一套有机朗肯循环余热回收系统,分别采用纯工质R245fa和非共沸混合工质R416A作为系统的工作介质。针对车用柴油机有机朗肯循环联合系统,提出了有用功提升率评价指标。通过数值计算,研究了不同柴油机工况下,有机朗肯循环系统和联合系统工作性能的变化规律,得出了有机工质质量流量与柴油机可用排气能量的对应关系。研究结果表明:随着柴油机转速和转矩的增加,两种工质(纯工质R245fa和非共沸混合工质R416A)的有机朗肯循环系统的净输出功率均逐渐增加,最大值分别为30.39kW和28.03kW;两种工质的车用柴油机有机朗肯循环联合系统的有用功提升率最大分别为9.00%(纯工质R245fa)和9.70%(非共沸混合工质R416A);采用非共沸混合工质R416A的性能优于采用纯工质R245fa。     

地热驱动非共沸工质有机闪蒸循环的热性能分析

非共沸工质具有变温相变特性,可有效改善有机闪蒸循环系统与冷源温度匹配差的问题,进而提高系统的循环性能。文章构建了有机闪蒸循环系统模型,其中,循环工质为R245fa/R601a混合物,热源温度为150℃。文章以净输出功率作为目标函数对有机闪蒸循环系统进行优化,研究了R245fa/R601a混合物的组分变化对有机闪蒸循环系统的闪蒸压力、质量流量、净输出功率和热效率的影响,并比较了以非共沸工质与纯工质作为循环工质时,有机闪蒸循环系统的净输出功率。模拟结果表明:当R245fa/R601a混合物的摩尔组分为3∶7时,有机闪蒸循环系统的净输出功率最大,为25.21 kW,与纯工质R245fa和R601a作为循环工质的有机闪蒸循环系统相比,分别增大了4.39%和5.66%,但以非共沸工质作为循环工质的有机闪蒸循环系统的热效率并不一定大于以纯工质作为循环工质;当R601a的摩尔组分为0～0.6时,以非共沸工质作为循环工质的有机闪蒸循环系统的热效率大于以纯工质作为循环工质;当R601a的摩尔组分为0.7～1时,以R245fa作为循环工质的有机闪蒸循环系统的热效率大于以非共沸工质作为循环工质。     

中低温热水发电系统循环参数和工质的选择

针对热源为80～150℃热水的有机朗肯循环（ORC）发电系统,以发电功率和效率为评价指标,分别分析了以R134a、R123和R245fa三种工质为循环介质时的系统,确定了最佳循环参数和工质。一般来说,最佳蒸发温度对应着最大的输出电功,且随着热流体温度的升高而升高;当热源温度大于120℃时,R134a的系统不存在最佳蒸发温度,此时输出电功随着蒸发温度的升高而增大。对于80～135℃的热水,工质R245fa的发电功率最大;当热水温度超过135℃时,工质R134a的发电功率最大。工质R245fa的发电效率始终是最大的。     

新型梯级换热有机朗肯循环系统热力性能分析

为了充分提高低品位能源利用过程中的回收利用率,降低热源排放温度,本研究提出一种基于热源分流的新型梯级换热、梯级发电的有机朗肯循环系统。系统以地热水为热源,分析了在给定热源工况时,蒸发温度对系统性能的影响以及在不同热源工况下,采用R123、R245fa及R152a3种工质互相组合时,系统性能的变化规律。结果表明,梯级ORC(有机朗肯循环)存在最佳蒸发温度,且其性能优于单级ORC循环,在T_g=373 K时,其输出功增加59.12 k W。随热源工况变化,两级循环中最佳工质分别变化,若两级循环均在亚临界区工作,则一级循环工质临界温度越低、二级循环工质临界温度越高系统性能越好;若两级循环中存在近临界运行工况,则应选择可使系统在近临界下运行工质。根据不同运行工况,合理选择最佳工质,对提高该梯级换热ORC系统性能具有重要意义。     

热源温度对有机朗肯循环发电特性的影响

基于搭建的以R245fa为工质的有机朗肯循环发电系统,通过调节电加热器功率来研究热源温度对有机朗肯循环发电特性的影响。研究表明:当冷凝温度不变时,随着热源温度的升高,蒸发压力升高,冷凝压力基本不变;膨胀机的压比和压差都增大;当热源温度由86℃升到99℃时,净输出电功率从4.7 kW增加到8 kW,发电效率由7.55%升至8.4%,功率和效率都近似线性增加。     

非共沸混合工质用于C-ORC系统的热力学分析

以低温烟气为热源,以R245fa、R152a及不同比例R245fa/R152a混合物为工质,提出新型的再热-抽汽-内回热联合有机朗肯循环(C-ORC)系统,基于美国NIST提供的制冷剂物性参数查询软件(REFPROP)及数学处理软件(MATLAB)混合编程,以净输出功和热效率为主要目标参数,分析系统性能随抽汽回热器出口温度、再热温度、不同比例混合工质的变化关系。结果表明,相同蒸发温度下纯工质R245fa的热力性能优于R152a,其最佳的抽汽回热器出口温度分别为70和55℃,抽汽回热器出口温度对系统的影响要大于再热温度的影响;混合工质分析中,在70℃抽汽回热器出口温度、105℃再热温度下,存在R245fa/R152a最佳质量分数比0.85/0.15,对应的净输出功为37.18 k W、热效率为18.52%、火用损为30.08 k W,其中蒸发器、冷凝器所占的火用损最大。     

R245fa、R123对太阳能有机朗肯循环系统性能的影响

为提高系统单位输出功率和循环效率,选择合适的工质至关重要。建立系统集热循环和发电循环二者之间参数耦合及能量匹配的数学模型。利用此模型,以北京夏至日太阳辐照度数据为基础,分别以R245fa、R123为工质的太阳能有机朗肯循环系统进行分析,结果表明:R245fa和R123工质对应的最佳蒸发压力分别为2.294、2.154MPa,最佳的导热油温度分别为188.04、233.18℃,最佳导热油与工质的流量比分别为0.89∶1、0.59∶1;在相同冷热源条件下,当两个系统达到各自的最佳性能时,使用R123为有机工质的系统输出功和效率更高,且要求系统的承压能力更低。     

R1234yf有机朗肯循环系统热力学性能研究

为提高有机朗肯循环（Organic Rankine Cycle, ORC）在中低温地热发电领域的效率,本文以R1234yf为工质,依据热力学第一定律与第二定律分析了系统单位质量热水净发电功率和系统?效率,并与目前应用广泛的R245fa工质进行了性能对比。研究结果表明,存在最佳蒸发温度和最佳冷凝温度,使得ORC发电系统单位质量热水净发电功率、?效率最大。对于热源温度为110℃ ~ 150℃的ORC发电系统,R1234yf对应的最大系统单位质量热水净发电功率和最大?效率均大于R245fa     

Experimental comparison of R245fa and R245fa/R601a for organic Rankine cycle using scroll expander

An experimental test was conducted to compare R245fa with R245fa/R601a on the organic Rankine cycle performance. The major objective of this paper is to ascertain the highest thermal efficiency and the optimal dimensionless volume ratio using the two working fluids. The experimental system consists of an electrically heated boiler, a vapor generator, a scroll expander, a condenser, a working fluid pump, and so on. For the typical weather conditions of May in Tianjin, the experiment results show that the working fluid charge has an important influence on the organic Rankine cycle performances. The optimal isentropic efficiency of the scroll expander corresponds to the design expansion ratio. Underexpanded and overexpanded processes result in the decline of the isentropic efficiency of the scroll expander, with the former playing a major role. R245fa/R601a improves the heat transfer performance in the vapor generator because of the nonisothermal phase change. The highest thermal efficiency for R245fa and R245fa/R601a is 4.38% and 4.45%, thereby illustrating that R245fa/R601a precedes R245fa. The optimal dimensionless volume ratios for R245fa and R245fa/R601a are 0.38 and 0.41, respectively. The experimental test lays foundation of the 500‐kW geothermal plant for demonstration in the next step. Copyright © 2014 John Wiley & Sons, Ltd.     

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.     

基于有机朗肯循环低温余热利用研究

文章应用PR方程编制了有机工质热物性计算程序,对多种有机工质的朗肯循环进行了热力计算,研究了各主要参数对朗肯循环性能影响的规律。在给定余热条件下,采用模拟退火算法对循环的主要参数进行优化,得出了整个循环在净输出功率最大时的最优参数值,并比较了以R236fa为工质的有机朗肯循环和常规朗肯循环的对外做功能力。     

亚临界有机朗肯循环系统的热经济分析与优化

以系统发电成本(electricity production cost,EPC)为评价指标,对用于回收工业锅炉烟气余热的有机朗肯循环(ORC)系统进行了热经济分析与优化。结果表明,随着蒸发器和冷凝器节点温差的增大,系统发电成本先减小、再增大,即存在一组最优的蒸发器和冷凝器节点温差使发电成本最小。分别以纯工质R245fa和R236ea、非共沸混合工质R141b/RC318和乙烷/丁烷为循环工质,得到了最小发电成本时有机朗肯循环系统的最优工作参数,以及对应的系统净输出功、热效率和火用效率。     

Comparison of a Basic Organic Rankine Cycle and a Parallel Double-Evaporator Organic Rankine Cycle

ABSTRACT

The applications of zeotropic mixtures and multi-evaporator systems are two viable options to improve the performance of the organic Rankine cycle (ORC). This paper conducts the thermo-economic comparison of a basic ORC with R245fa/R600a and a parallel double-evaporator organic Rankine cycle (PDORC) with R245fa. Four indicators are used to evaluate the system performance: net power, cycle efficiency, area of heat exchangers, and area of heat exchangers per net power output. Submodels of condensers and evaporators are established specially for pure organic fluids and zeotropic mixtures. The performance optimization using genetic algorithm is conducted to compare the two systems quantitatively. The optimization indicates a zeotropic mixture is more profitable than a pure work fluid in a basic ORC with a worthy additional investment of heat exchanger. Though PDORC can increase net power obviously, it would decrease the thermo-economic performance 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%。     

Optimum composition ratios of multicomponent mixtures of organic Rankine cycle for engine waste heat recovery

With the temperature glide in saturation states, the mixture working fluids have the advantages in thermal energy conversion. In this study, through the investigation in optimum mass fractions of multicomponent mixture working fluids, the economic performance enhancement of the organic Rankine cycle system is obtained for recovering waste heat from engine. The zero ozone-depletion-potential and dry working fluids of R236fa, R245fa, and R1336mzz(Z) are selected as the components of multicomponent mixtures in the system. The net power output, heat transfer calculation, and apparatus cost evaluation are employed to evaluate the power cost of the organic Rankine cycle system. Parameters of temperatures of waste heat sources and efficiencies of expanders are taken into account. The comparisons of economic performances for single-component working fluid and multicomponent mixtures with optimum mass fractions are proposed. The results show that R245fa, having a levelized cost of energy, LCOE, of 8.75 × 10⁻² $/kW-h, performs the best for single-component working fluids, better than R236fa by 1.6% and R1336mzz(Z) by 8.3%. All the two-component mixtures are superior to their single-component working fluids in economic performance. Among the three two-component mixture working fluids, R1336mzz(Z)/R236fa has the lowest LCOE_min, 8.57 × 10⁻² $/kW-h, followed by R236fa/R245fa and R245fa/R1336mzz(Z). In addition, R236fa/R245fa/R1336mzz(Z) mixture, which has a LCOE_min of 8.47 × 10⁻² $/kW-h, economically outperforms all other working fluids and has a lower LCOE_min than R236fa/R245fa by 1.7% and R245fa/R1336mzz(Z) by 2%.     

跨临界-亚临界复叠式有机朗肯循环性能分析

热源温度高于473.15 K时,复叠式有机朗肯循环(organic Rankine cycle,ORC)可避免高温下工质热分解、膨胀比过大等缺点,相对单级ORC更具优势.跨临界循环相较常规亚临界具有更高的吸热压力及更好的热源匹配性,其与复叠式ORC耦合有望获得更优的热力性能.因此,构建了跨临界-亚临界复叠式ORC(TS...     

Thermodynamic investigation of solar energy-based triple combined power cycle

The present work deals with the thermodynamic analysis of a solar-powered triple combined power cycle to generate emission-free power. The triple combined cycle comprises one topping cycle as Brayton cycle and two bottoming cycles, namely, steam Rankine cycle (SRC) and organic Rankine cycle (ORC). The Brayton cycle employs double-stage compression with intercooling. During intercooling, heat energy rejected by the compressed air was further utilized in the ORC. The energy carried away after the turbine exit was used in the SRC. The proposed cycle performance is investigated for three working fluids to use with the bottoming ORC. Results showed that the maximum overall thermal efficiency and work output of solar energy-based triple combined cycle are found 21.89% and 218.98 kJ/kg air, respectively, for organic fluid R245fa at the topping cycle pressure ratio of 31.