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     

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。     

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％.     

低温地热有机朗肯循环(ORC)工质选择

对低温(60～150℃)地热有机朗肯循环(ORC)系统,以净输出电功和系统能量损失作为评价指标,分析不同地热流体温度下有机工质R290,R134a,R600a,R600,R601a的做功能力,确定最佳循环工质.分析结果表明:对于湿流体工质,由于临界温度较低,当地热流体温度高于其临界温度20℃时,不存在最佳蒸发温度:对于60～80℃的地热流体,工质R601a的最大净输出电功最大;对于90～120℃的地热流体,工质R134a的最大净输出电功最大;对于125～150℃的地热流体,工质R290的净输出电功最大.这些结果为中低温地热利用提供设计依据.     

太阳能有机朗肯循环发电系统模拟优化研究

针对低温太阳能集热器出水温度为65～90℃的特点，根据有机朗肯循环发电原理，选取R134a、R152a、R600a、RC318、R600、R245fa共6种工质，利用EES平台进行仿真模拟和比较分析。分析结果表明：在此温度范围内，蒸发压力、蒸发温度、系统净发电功率、热电效率及系统吸热量与热源温度变化呈正比关系，且当热源温度为90℃时，RC318系统净发电功率与热电效率最高，分别为12.27 kW、15.42%。当热源温度为85℃时，RC318系统效率达到最高值82.52%。     

应用热力学分析方法与AHP_熵值法对ORC的工质比较及优化

选取4种有机工质R245fa、R123、R600和R141b做为循环工质,采用火用分析方法在烟气入口温度为150℃、出口温度为75℃的条件下,在蒸发温度为80-140℃范围内对4种有机工质的亚临界有机朗肯循环进行分析,发现系统各设备的火用效率、系统总的火用效率、热效率、净输出功随蒸发温度的升高而升高,火用损失随蒸发温度的升高而降低。当蒸发温度达到140℃时,系统各设备的火用效率、系统总的火用效率、热效率、净输出功均达到最大值,而火用损失达到最小值。因此,4种有机工质蒸发温度在80-140℃范围内的最佳蒸发温度都为140℃,且4种工质中R141b的有机朗肯循环系统各设备的火用效率、系统总的火用效率、热效率、净输出功最大,火用损失最少,所以R141b为该系统的最适合工质,R123、R600和R245fa依次次之。以系统总火用损失、热效率、火用效率和净输出功为评价指标,采用层次分析法(The Analytic Hierarchy Process,AHP),通过熵值法确定权重因子,得到R600和R245fa的综合评价指标ξ,发现R600比R245fa更优。     

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。     

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。     

芳烃蒸馏过程低温余热发电系统影响因素分析

针对以芳烃蒸馏过程余热为热源的有机物工质朗肯循环(Organic Rankine Cycle,ORC)发电系统,建立了数学模型,计算并比较了包括R600a、R601及R245fa在内的几种工质的工作压力、膨胀比、系统效率等参数,分析并验证了工质流动阻力和常见几种冷却方式对系统工作参数、系统效率等的影响。研究表明:在工质蒸发温度为90-130℃,冷凝温度45℃的条件下,流动阻力损失导致系统发电功率和效率分别降低约1.5%-9.2%和1.7%-9.3%;循环水冷却系统耗功占系统发电功率比(即耗功比)最大,达到7.6%-13.7%,直流水冷却系统耗功比最小,约3.6%-4.9%;与直接空气冷却方式相比,湿式空气冷却方式在环境温度高于30℃时可使系统发电效率提高40.4%-47.7%。     

利用地热能的双压有机朗肯循环性能分析

根据地热利用系统回灌的要求,对热源在系统出口处的温度进行限制,研究了双压有机朗肯循环（DPORC）中的热量分配以及随运行时间的系统性能变化,针对5种不同的有机工质进行了计算分析。研究表明：系统热力学性能的最大值和有机工质流量的最小值在同样的k值（热源提供给高压循环的热量与热源为DPORC提供的热量比）处获得。而采用R600和R245fa系统的净输出功率较大;相比R601,采用R245fa可以将系统的净输出功率提高168.06 kW（5.55%）,热效率和效率分别可提高0.70%和2.86%。相比于单压有机朗肯循环（SPORC）,DPORC可以有效减小系统随运行时间净输出功率降低的幅度。经过40 a的运行,采用R601的系统净输出功率降低幅度最低（428.11 kW, 14.14%）,而采用R600系统的净输出功率降低幅度最大（526.75 kW, 16.55%）。     

Candidate radial-inflow turbines and high-density working fluids for geothermal power systems

Optimisation of Organic Rankine Cycle (ORCs) for binary-cycle geothermal applications could play a major role in determining the competitiveness of low to moderate temperature geothermal resources. Part of this optimisation process is matching cycles to a given resource such that power output can be maximised. Two major and largely interrelated components of the cycle are the working fluid and the turbine. Both components need careful consideration: the selection of working fluid and appropriate operating conditions as well as optimisation of the turbine design for those conditions will determine the amount of power that can be extracted from a resource. In this paper, we present the rationale for the use of radial-inflow turbines for ORC applications and the preliminary design of several radial-inflow machines based on a number of promising ORC systems that use five different working fluids: R134a, R143a, R236fa, R245fa and n-Pentane. Preliminary meanline analysis lead to the generation of turbine designs for the various cycles with similar efficiencies (77%) but large differences in dimensions (139-289 mm rotor diameter). The highest performing cycle, based on R134a, was found to produce 33% more net power from a 150 °C resource flowing at 10 kg/s than the lowest performing cycle, based on n-Pentane.     

低温地热双循环式发电系统横管喷淋降膜蒸发器传热性能实验研究

以R245fa为工质,搭建有机朗肯循环（ORC）发电系统横管喷淋降膜蒸发器传热测试平台,研究有机工质喷淋密度,地热水初温及流率等因素对管外换热系数的影响。实验结果表明：随着有机工质喷淋密度、地热水初温、地热水流率的增大,传热系数均先增大后减小。最后,根据实验结果,对现有横管喷淋降膜蒸发器的管外传热系数经验公式的参数进行修正。     

Working fluids for low-temperature heat source

The performance of different working fluids to recover low-temperature heat source is studied. A simple Rankine cycle with subcritical configuration is considered. This work is to screen working fluids based on power production capability and component (heat exchanger and turbine) size requirements. Working fluids considered are R134a, R123, R227ea, R245fa, R290, and n-pentane. Energy balance is carried out to predict operating conditions of the process. Outputs of energy balance are used as input for exergy analysis and components (heat exchanger and turbine) design. The heat exchanger is divided into small intervals so that logarithmic mean temperature difference (LMTD) method is applicable. R227ea gives highest power for heat source temperature range of 80–160 °C and R245fa produces the highest in the range of 160–200 °C. There is optimal pressure where the heat exchanger surface area is minimum. This optimal pressure changes with heat source temperature and working fluid used. The least heat exchanger area required at constant power rating is found when the working fluid is n-pentane. At lower heat source temperature (80 °C), the maximum power output and minimum heat exchanger surface area for different working fluids is comparable.     

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%.     

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...     

分液冷凝有机朗肯循环系统R245fa/HFOs工质选择研究

有机朗肯循环是中低品位热能高效利用的有效技术之一,分液冷凝有机朗肯循环（LSCORC）是基于分液冷凝传热强化的新型热力循环。为寻找新型环保替代工质,建立LSCORC系统的热力学模型,以最大化净输出功为目标,重点考虑了雅各布数、冷热源换热匹配对系统性能的影响,对R245fa/HFOs工质进行了对比筛选。结果表明：工质的雅各布数越大,其净输出功越小;在基础工况下,R245fa/R1336mzz(Z)的热力性能及热经济性表现最佳;当热源参数变化时,雅各布数较小工质的性能表现普遍优于雅各布数较大的工质组合;当冷源参数变化时,在分液冷凝器两个流程中温度滑移和冷源温升匹配越好的工质组合,其系统净输出功越大。     

Analysis of optimization in an OTEC plant using organic Rankine cycle

This study quantified the effects of evaporation temperature, condensation temperature, and the inlet- and outlet-temperature differences of deep cold seawater and warm seawater on the performance of an ocean thermal energy conversion (OTEC) plant using an organic Rankine cycle (ORC), and also investigated the optimal operations required for the performance. A finite-temperature-difference heat transfer method is developed to evaluate the objective parameter, which is the ratio of net power output to the total heat transfer area of heat exchanger in the system, and R717, R600a, R245fa, R152a, and R134a were used as the working fluids. The optimal evaporation and condensation temperatures were obtained under various conditions for maximal objective parameters in an OTEC system.The results show that R717 performed optimally in objective parameter evaluation among the five working fluids, and that R600a performed better than other fluids in thermal efficiency analysis. The optimal seawater temperature differences between the inlet and outlet of the evaporator and condenser are proposed. Furthermore, the influences of inlet temperatures of warm and cold seawater in the ORC are presented for an OTEC plant. The simulation results should enable the performance of an ORC system to be compared when using various organic working fluids.