有机工质朗肯循环发电技术在钢铁行业中的应用

采用低沸点双工质有机朗肯循环余热发电系统来回收钢铁生产过程中产生的的低品位余热。本文阐述目前我国低温余热回收状况,介绍有机工质的物理性质、化学性质、热力学性质等,分析运用朗肯循环余热发电的经济性和解决低沸点双工质发电系统的关键技术,结合实际工程经验对该系统进行分析。     

Dynamic modeling and optimal control strategy of waste heat recovery Organic Rankine Cycles

Organic Rankine Cycles (ORCs) are particularly suitable for recovering energy from low-grade heat sources. This paper describes the behavior of a small-scale ORC used to recover energy from a variable flow rate and temperature waste heat source. A traditional static model is unable to predict transient behavior in a cycle with a varying thermal source, whereas this capability is essential for simulating an appropriate cycle control strategy during part-load operation and start and stop procedures. A dynamic model of the ORC is therefore proposed focusing specifically on the time-varying performance of the heat exchangers, the dynamics of the other components being of minor importance. Three different control strategies are proposed and compared. The simulation results show that a model predictive control strategy based on the steady-state optimization of the cycle under various conditions is the one showing the best results.     

有机朗肯循环的研究进展

有机朗肯循环是一种被认为能有效利用低温热能的技术。科研工作者在不同方面（包括工质、膨胀机、换热器的影响、系统的优化）对有机朗肯循环系统效率的影响进行了大量的研究。本文针对不同热源的工质筛选、膨胀机的特点、系统循环优化以及换热器的影响方面进行了讨论和总结,为有机朗肯循环系统的实际应用提供参考。     

Experimental study and modeling of an Organic Rankine Cycle using scroll expander

This paper presents both a numerical model of an Organic Rankine Cycle (ORC) and an experimental study carried out on a prototype working with refrigerant HCFC-123, and whose heat sources consist in two hot air flows. The ORC model is built by interconnecting different sub-models: the heat exchanger models, a volumetric pump model and a scroll expander model. Measured performance of the ORC prototype is presented and used to validate the ORC model. This model is finally used to investigate potential improvements of the prototype.     

Analysis of exhaust waste heat recovery from a dual fuel low temperature combustion engine using an Organic Rankine Cycle

This paper examines the exhaust waste heat recovery potential of a high-efficiency, low-emissions dual fuel low temperature combustion engine using an Organic Rankine Cycle (ORC). Potential improvements in fuel conversion efficiency (FCE) and specific emissions (NO_x and CO₂) with hot exhaust gas recirculation (EGR) and ORC turbocompounding were quantified over a range of injection timings and engine loads. With hot EGR and ORC turbocompounding, FCE improved by an average of 7 percentage points for all injection timings and loads while NO_x and CO₂ emissions recorded an 18 percent (average) decrease. From pinch-point analysis of the ORC evaporator, ORC heat exchanger effectiveness (?), percent EGR, and exhaust manifold pressure were identified as important design parameters. Higher pinch point temperature differences (PPTD) uniformly yielded greater exergy destruction in the ORC evaporator, irrespective of engine operating conditions. Increasing percent EGR yielded higher FCEs and stable engine operation but also increased exergy destruction in the ORC evaporator. It was observed that hot EGR can prevent water condensation in the ORC evaporator, thereby reducing corrosion potential in the exhaust piping. Higher ? values yielded lower PPTD and higher exergy efficiencies while lower ? values decreased post-evaporator exhaust temperatures below water condensation temperatures and reduced exergy efficiencies.     

基于有机朗肯循环的APU余热回收系统性能分析

为有效利用飞机辅助动力装置（Auxitlary Power Unit , APU）排气余热,基于有机朗肯循环（Organic Rankine Cycle, ORC）发电系统,构建了APU余热回收系统。系统以APU排气余热为输入,驱动ORC做功,输出电能,为机载设备提供二次能源。结合工程热力学原理,建立系统热力学模型,并通过Matlab编程对余热回收系统进行了仿真计算及性能分析。仿真结果表明,系统功率及效率随飞行马赫数增加而降低;APU余热回收系统在飞机低音速飞行时有良好的性能;马赫数小于1时,系统功率在12 kW以上,效率在11%以上,耗气率低于0.0262 kg/kJ。     

不同工质对内置换热器有机朗肯循环系统热性能的影响

有机朗肯循环(Organic Rankine Cycle,ORC)可实现中低温热能的有效利用,但其热利用效率仍可进一步提高,而内置换热器的使用可有效提高循环的热利用效率。因此,文章构建了内置换热器ORC系统的热力学模型。研究了当蒸发温度变化时,R600,R601a,R236ea,R245fa,R245ca,R123,R600a,R114和R142b对内置换热器ORC系统性能的影响,并比较了内置换热器ORC系统与传统ORC系统的净输出功率和热效率。结果表明:在最优蒸发温度下,采用R236ea的内置换热器ORC系统净输出功率大于其余工质,为32.40 kW,其比第二最大净输出功率R600a系统相对增大1.16%;采用R601a的内置换热器ORC系统的热效率最大。内置换热器ORC系统的最大净输出功率及热效率均较传统ORC系统显著增大。     

Internal Combustion Engine (ICE) bottoming with Organic Rankine Cycles (ORCs)

This paper describes a specific thermodynamic analysis in order to efficiently match a vapour cycle to that of a stationary Internal Combustion Engine (ICE). Three different working fluids are considered to represent the main classes of fluids, with reference to the shape of the vapour lines in the T–s diagram: overhanging, nearly isoentropic and bell shaped. First a parametric analysis is conducted in order to determine optimal evaporating pressures for each fluid. After which three different cycles setups are considered: a simple cycle with the use of only engine exhaust gases as a thermal source, a simple cycle with the use of exhaust gases and engine cooling water and a regenerated cycle.     

A supercritical Rankine cycle using zeotropic mixture working fluids for the conversion of low-grade heat into power

A supercritical Rankine cycle using zeotropic mixture working fluids for the conversion of low-grade heat into power is proposed and analyzed in this paper. Unlike a conventional organic Rankine cycle, a supercritical Rankine cycle does not go through the two-phase region during the heating process. By adopting zeotropic mixtures as the working fluids, the condensation process also happens non-isothermally. Both of these features create a potential for reducing the irreversibilities and improving the system efficiency. A comparative study between an organic Rankine cycle and the proposed supercritical Rankine cycle shows that the proposed cycle can achieve thermal efficiencies of 10.8-13.4% with the cycle high temperature of 393 K-473 K as compared to 9.7-10.1% for the organic Rankine cycle, which is an improvement of 10-30% over the organic Rankine cycle. When including the heating and condensation processes in the system, the system exergy efficiency is 38.6% for the proposed supercritical Rankine cycle as compared to 24.1% for the organic Rankine cycle.     

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     

Parametric optimization and performance analysis of a waste heat recovery system using Organic Rankine Cycle

Parametric optimization and performance analysis of a waste heat recovery system based on Organic Rankine Cycle, using R-12, R-123 and R-134a as working fluids for power generation have been studied. The cycles are compared with heat source as waste heat of flue gas at 140 °C and 312 Kg/s/unit mass flow rate at the exhaust of ID fans for 4 × 210 MW, NTPC Ltd. Kahalgaon, India. Optimization of turbine inlet pressure for maximum work and efficiencies of the system along the saturated vapour line and isobaric superheating at different pressures has been carried out for the selected fluids. The results show that R-123 has the maximum work output and efficiencies among all the selected fluids. The Carnot efficiency for R-123 at corrected pressure evaluated under similar conditions is close to the actual efficiency. It can generate 19.09 MW with a mass flow rate of 341.16 Kg/s having a pinch point of 5 °C, First law efficiency of 25.30% and the Second law efficiency of 64.40%. Hence selection of an Organic Rankine Cycle with R-123 as working fluid appears to be a choice system for utilizing low-grade heat sources for power generation.     

Thermodynamic analysis of double‐stage biomass fired Organic Rankine Cycle for micro‐cogeneration

A biomass fired double‐stage Organic Rankine Cycle (ORC) for micro‐cogeneration is studied. Focus is laid on optimizing thermal efficiency in summer mode by appropriate working fluid and pressure level selection. Simulation and thermodynamic analysis show that in double‐stage ORC, the working fluid in the low‐temperature circuit (LTC) effects total efficiency more than the working fluid in the high‐temperature circuit (HTC). Within the chosen boundary conditions, isopentane gives best thermal efficiency, whereas R227ea is the least efficient in the LTC. Among the working fluids for the HTC, maximum total efficiency is similar for several working fluids. Simulations demonstrate that a prediction of thermal efficiencies with respect to physico‐chemical characteristics of different working fluids is only feasible within certain chemical classes. In the HTC, low critical temperature, low molar mass, and high critical pressure increase the efficiency, whereas in the LTC, condensation pressure is most crucial for high efficiency. Constructional analysis indicate that in the majority of cases, an increase in thermal efficiency is connected with high‐volume flow rates at the outlet of the turbine, which leads to voluminous expansion units and high investment costs, respectively. Appropriate working fluid combinations within a double‐stage ORC reach total efficiencies of up to 35% at flue gas temperatures from 950 to 150 °C. Copyright © 2012 John Wiley & Sons, Ltd.     

非共沸工质与纯工质在ORC系统中的特性比较研究

工质的特性是影响ORC(有机朗肯循环)系统性能的重要因素之一。建立了65~100℃低温地热水有机朗肯循环发电系统数学模型,将R245fa分别与R601a和R227ea以不同比例混合作为ORC系统的工质,比较了非共沸混合物和纯物质两类工质对ORC系统循环净功、热效率和火用效率的影响。研究结果表明:无论是纯工质还是非共沸工质,系统的循环净功、热效率和火用效率都随着热源温度的升高而增大。工质在相变过程中是否存在温度滑移,是影响ORC系统性能的重要因素之一。在65~100℃的热源条件下,综合考虑3个评价指标,当R245fa配比为0.1~0.7时,R245fa/R601a混合物的循环净功、热效率和火用效率分别提升0.012~2.48 k W、0.005%~1.15%和0.08%~10.7%;当R245fa配比为0.5~0.9时,R245fa/R227ea混合物的循环净功、热效率和火用效率分别提升0.049~4.25 k W、0.057%~1.75%和0.21%~16.1%。     

子宫肌瘤数字化三维动脉血管网的构建和意义

【摘要】 目的 探讨构建基于CTA数据的子宫肌瘤数字化三维动脉血管网的方法,并通过其观察肌瘤的血供来源和血供分布类型?方法 选取子宫肌瘤患者64例行双源CTA扫描,获取CT原始图像后利用Mimics10.01软件对子宫肌瘤动脉血管网进行数字化三维重建,并作分析。结果 (1)构建了64例患者的子宫肌瘤数字化三维动脉血管网,可清晰的显示盆腔大动脉。子宫动脉及肌瘤的主要供血血管和血供分布情况。(2)患者肌瘤的血供来源分别为子宫动脉(81.25%)。子宫动脉和单侧卵巢动脉(10.9%)、子宫动脉和双侧卵巢动脉(4.69%)及卵巢动脉(3.1%)。(3)子宫肌瘤血供的分布类型可分为4型:①Ⅰ型:一侧动脉供血为主型(一侧子宫动脉伴/不伴同侧卵巢动脉的供血量显著超过子宫肌瘤瘤体的1/2),占35.9%(23/64);②Ⅱ型:双侧动脉供血均衡型(双侧子宫动脉伴/不伴同侧卵巢动脉的供血量分别约为子宫肌瘤瘤体的1/2),占53.1%(34/64);③Ⅲ型:单纯一侧子宫动脉供血型,占7.8%(5/64);④Ⅳ型:卵巢动脉供血型,占3.1%(2/64)。结论 利用CTA和重建软件可以构建出数字化三维的子宫肌瘤动脉血管网,并可进行血供来源及分布的分析,为手术方案的制定和临床教学提供参考。     

有机朗肯循环低品位能回收技术

有机朗肯循环是回收低品位能的有效途径,对有机朗肯循环的工质、膨胀机等关键技术及实际应用情况进行了介绍。     

Working fluids for low-temperature organic Rankine cycles

A thermodynamic screening of 31 pure component working fluids for organic Rankine cycles (ORC) is given using BACKONE equation of state. The fluids are alkanes, fluorinated alkanes, ethers and fluorinated ethers. The ORC cycles operate between 100 and 30 °C typical for geothermal power plants at pressures mostly limited to 20 bar, but in some cases supercritical pressures are also considered. Thermal efficiencies η_th are presented for cycles of different types. In case of subcritical pressure processes one has to distinguish (1) whether the shape of the saturated vapour line in the T,s-diagram is bell-shaped or overhanging, and (2) whether the vapour entering the turbine is saturated or superheated. Moreover, in case that the vapour leaving the turbine is superheated, an internal heat exchanger (IHE) may be used. The highest η_th-values are obtained for the high boiling substances with overhanging saturated vapour line in subcritical processes with an IHE, e.g., for n-butane η_th=0.130. On the other hand, a pinch analysis for the heat transfer from the heat carrier with maximum temperature of 120 °C to the working fluid shows that the largest amount of heat can be transferred to a supercritical fluid and the least to a high-boiling subcritical fluid.     

Parametric optimisation of the organic Rankine cycle for power generation from low-grade waste heat

This research work deals with the optimisation of controllable parameters of the organic Rankine cycle (ORC) run by waste heat. Performance measures have been evaluated for different waste heat temperatures, condenser temperatures, refrigerants and mass flow rate. The design of experiment was performed on the L9 orthogonal array of Taguchi's method. Three performance measures such as thermal efficiency, exergy destruction rate and the work output were used for the assessment and optimisation of the cycle. An optimum combination of parameters obtained by Taguchi's method is compared with analytical results. The comparison suggests that the variance of results is within the desired level of confidence. Individual effect of parameters on the performance of ORC is also estimated using analysis of variance. Turbine inlet temperature has large effects on efficiency and work output. Mass flow rate of the refrigerant has the largest effect on the exergy destruction rate.     

Performance of a combined organic Rankine cycle and vapor compression cycle for heat activated cooling

Heat activated cooling has the potential of utilizing thermal sources that currently go unused such as engine exhaust heat or industrial waste heat. Using these heat sources can provide enhanced energy utilization and reduced fuel usage in applications where cooling is needed. The concept developed here uses waste heat from stationary and mobile engine cycles to generate cooling for structures and vehicles. It combines an organic Rankine cycle (ORC) with a conventional vapor compression cycle. A nominal 5 kW cooling capacity prototype system was developed based on this concept and tested under laboratory conditions. In order to maintain high system performance while reducing size and weight for portable applications, microchannel based heat transfer components and scroll based expansion and compression were used. Although the system was tested off of its design point, it performed well achieving 4.4 kW of cooling at a measured heat activated COP of 0.48. Both the conversion and 2nd law efficiencies were close to the model results, proving it to be an attractive technology. The measured isentropic efficiency of the scroll expander reached 84%, when the pressure ratio was close to the scroll intrinsic expansion ratio. The reduced cooling capacity was attributed to off design operation.     

Optimization of low temperature solar thermal electric generation with Organic Rankine Cycle in different areas

The presented low temperature solar thermal electric generation system mainly consists of compound parabolic concentrators (CPC) and the Organic Rankine Cycle (ORC) working with HCFC-123. A novel design is proposed to reduce heat transfer irreversibility between conduction oil and HCFC-123 in the heat exchangers while maintaining the stability of electricity output. Mathematical formulations are developed to study the heat transfer and energy conversion processes and the numerical simulation is carried out based on distributed parameters. Annual performances of the proposed system in different areas of Canberra, Singapore, Bombay, Lhasa, Sacramento and Berlin are simulated. The influences of the collector tilt angle adjustment, the connection between the heat exchangers and the CPC collectors, and the ORC evaporation temperature on the system performance are investigated. The results indicate that the three factors have a major impact on the annual electricity output and should be the key points of optimization. And the optimized system shows that: (1) The annual received direct irradiance can be significantly increased by two or three times optimal adjustments even when the CPC concentration ratio is smaller than 3.0. (2) Compared with the traditional single-stage collectors, two-stage collectors connected with the heat exchangers by two thermal oil cycles can improve the collector efficiency by 8.1–20.9% in the simultaneous processes of heat collection and power generation. (3) On the use of the market available collectors the optimal ORC evaporation temperatures in most of the simulated areas are around 120 °C.     

低温太阳能热力发电有机朗肯循环工质的选择

为了筛选出适宜于低温太阳能热力发电有机朗肯循环的工质,根据 PR 状态方程计算和分析了采用 11 种低沸点有机流体工质的低温太阳能发电朗肯循环的热力性能.结果表明:随着工质临界温度的升高,有机透平进口处的最大蒸发压力基本呈下降趋势;在凝结温度与有机透平进口温度一定的情况下,临界温度越高的流体,其循环热效率越高;使用正已烷和正戊烷能获得较高的循环热效率,凝汽器中的凝结压力比较适中,是比较适合用作低温太阳能热力发电有机朗肯循环的工质.