炼钢电炉余热发电技术的研究与应用

结合炼钢电炉饱和蒸汽余热发电的工程实例,介绍炼钢电炉的余热统计情况和余热发电系统的技术方案。余热发电技术在炼钢电炉的成功应用,开辟了电炉节能减排的新途径,取得了显著的经济效益和社会效益。     

Exergy analysis of a 1.2 MW waste heat power generation project

According to systematic features, analysis method based on exergy balance is established. Basic indicators in the system, the subsystem, and facilities are put forward in this paper. By using this method to analyze the generation system of megawatt‐scale in one chemical enterprise, it is found that the objective exergy efficiency of the system is 35.67%, and exergy loss of organic Rankine cycle (ORC) is the highest. The thermal efficiency of the total system is 9.61%. For the condenser, the thermal efficiency is 91.18%, and the exergy efficiency is only 23.44%. The objective exergy efficiency of the evaporator is 74.04%. The influence coefficient of exergy loss of condenser is higher than that of pump and expander, but input exergy of the condenser is lower than that of the expander. It is revealed that ORC subsystem is the part which needs to be focused on, and the condenser is the most important component of ORC subsystem which should be optimized firstly.     

中低温废热发电的思路与方法

在工业生产过程中,存在着大量具有一定温度品质的热能被放散。实践中,可以通过某种设备系统将其回收利用,既节约了宝贵的一次能源,又改善了环境质量。中低温废热发电就是回收废热而生产二次优质能源的一种方法。     

垃圾焚烧热电联产蒸汽参数选择

针对垃圾焚烧热电联产时,采用中温中压及中温次高压蒸汽参数对全厂投资及经济性的影响进行研究。以日处理规模为600 t·d^-1的生活垃圾焚烧设施作为研究对象,从主机设备参数、主机设备投资额、经济指标、营业收入及投资回收期等5个方面进行分析。研究结果表明,采用中温次高压参数时,垃圾焚烧设施热电联产全厂热效率较采用中温中压参数时提高1.7%,热电联产时全年总收入较采用中温中压参数时提高11.5%,且经济性更好,静态投资回收期约为4.73年。     

Performance effect on the TEG system for waste heat recovery in automobiles using ZnO and SiO2 nanofluid coolants

Enhancement in heat transfer of the cold side is vital to amplify the performance of a thermoelectric generator (TEG). With enriched thermophysical properties of nanofluids, significant improvement in heat transfer process can be obtained. The current study concerns the performance comparison of an automobile waste heat recovery system with EG‐water (EG‐W) mixture, ZnO, and SiO₂ nanofluid as coolants for the TEG system. The effects on performance parameters, that is, circuit voltage, conversion efficiency, and output power with exhaust inlet temperature, the total area of TEG, Reynolds number, and particle concentration of nanofluids for the TEG system have been investigated. A detailed performance analysis revealed an increase in voltage, power output, and conversion efficiency of the TEG system with SiO ₂ nanofluid, followed by ZnO and EG‐W coolants. The electric power and conversion efficiency for SiO ₂ nanofluid at an exhaust inlet temperature of 500K were enhanced by 11.80% and 11.39% respectively, in comparison with EG‐W coolants. Moreover, the model speculates that an optimal total area of TEGs exists for the maximum power output of the system. With SiO ₂ nanofluid as a coolant, the total area of TEGs can be diminished by up to 34% as compared with EG‐W, which brings significant convenience for the placement of TEGs and reduces the cost of the TEG system.     

Modelling of heat transfer and fluid flow in the hot section of gas turbines used in power generation: A comprehensive survey

Power generation is one of the major industries or businesses globally. Although, at present, a major attention has been paid towards the sustainable energy technologies, both gas and steam turbines are still heavily used in the power generation sector worldwide. Usually, gas turbines are used to drive an electrical power generator in simple systems, or they are used in combined cycle plants together with steam turbines. This paper presents a comprehensive review on modelling of heat transfer and fluid flow in hot section of gas turbines used in the power generation sector. Visibly, heat transfer and fluid flow characteristics directly affect the thermal efficiency and the overall performance of the gas turbines. Hence, existing models relating to heat transfer and fluid flow inside gas turbines are discussed in detail. Primarily, methods relating to the first principle modelling, empirical modelling, and finite element modelling are reviewed comprehensively, and then, a discussion is provided together with a comparison among models in terms of their advantages and disadvantages. Moreover, some existing issues such as the environmental impact are discussed which still remain as challenges to the power generation industry together with some of the possible future directions for improvements.     

水泥厂余热利用研究

本文论述了焦作水泥厂中温烟气余热发电方案研究。讨论了设计方案、设备选型并进行了技术经济分析。本文结论对同类型余热利用工程具有参考价值。     

Exploring the heat transfer performance of nanofluid as a coolant for power battery pack

Nanofluids with high thermal conductivity coefficient are introduced to the thermal management system of power battery packs for electric vehicles and hybrid electric vehicles. Two typical cooling structures of cylindrical and square battery packs are described, and their flow models are established. By similarity transformations, the nonlinear system of partial differential equations is reduced and then solved numerically by the shooting method. The heat transfer properties of three types of nanofluids, that is, CuO‐EG, Al₂O₃‐EG, TiO₂‐EG, are analyzed in detail. It is found that CuO‐EG nanofluid is the best coolant for the cylindrical battery pack, whereas Al₂O₃‐EG nanofluid is the best choice for square battery pack cooling.     

回收工业废热的吸收式热变换器技术

介绍了提升工业废热温位的吸收式热变换器的工作原理 ,工质的热力循环过程。应用热力学第二定律和工质的热力学性能数据 ,分别对工质的理论循环过程与实际循环过程的性能系数进行了理论分析和计算 ,研究了操作参数对性能系数和温升的影响规律     

Performance assessment of steam Rankine cycle and sCO2 Brayton cycle for waste heat recovery in a cement plant: A comparative study for supercritical fluids

The main objective of this study is to investigate the feasibility of a waste heat recovery (WHR) closed Brayton cycle (BC) working with supercritical carbon dioxide (sCO₂). For this aim, an actual WHR steam Rankine cycle (RC) in a cement plant was evaluated thermodynamically. After, a sCO₂-BC was theoretically adapted to the actual WHR system for the performance assessment. Both systems were analyzed comparatively in terms of energy and exergy. According to the results, the sCO₂-BC showed higher performance than the actual steam RC with a net electricity generation of 9363 kW where it was calculated as 8275 kW for the actual cycle. In addition, the energy efficiencies were found to be 27.6% and 24.18% where the exergy efficiencies were calculated as 58.22% and 51.39% for sCO₂-BC and steam RC, respectively. In the following part of the study, the closed BC was examined for different supercritical working fluids, namely, CO₂, pentafluoroethane (R125), fluoromethane (R41), and sulfur hexafluoride (SF6). Parametrical analyses were conducted to determine the effects of the system parameters such as turbine inlet temperature, compressor inlet temperature, and pressure ratio on the cycle performance. The simulation results of the comparative study showed that, among the supercritical fluids, the CO₂ demonstrated a higher performance for the closed BC with an energy efficiency of 27.9% followed by R41, SF6, and R125. As a result, the utilization of sCO₂-BC for WHR can be sustainably adapted and extended for environmentally friendly energy generation.     

Design of electric power generation systems using waste heat energy

The recent energy crisis forces engineers to take into account reduction of electricity consumption as well as heat energy consumption in industry. As it is very difficult to save the amount of electricity, they have tried to recover electric power using waste heat energies. In this paper, the possibilities of electric power recovery from waste heat energies are discussed based on the relationship between supply heat sources and demand heat sources in chemical process systems. In solving such problems, the following difficulties appear: calculation of maximum quantity of generated electric power, determination of a suitable working fluid and its temperatures in the Rankine cycle, and so on. The proposed method can solve them using the temperature-enthalpy diagram and, furthermore, has the advantage of being able to design a final heat exchanger network with heat exchangers in a power plant by means of a synthesis method using the same diagram.     

MHD heat transfer and entropy production of an Al2O3-water nanofluid in a horizontal cylinder

This paper deals with the effect of magnetic fields (B_r, B_θ, B_z) applied in r-, θ-, z-directions, respectively, on entropy production and heat transfer and in a horizontal cylinder filled with an Al₂O₃-water nanofluid. The results are verified using literature data. For different Richardson, Ri, and Hartmann numbers, Ha, the nanoparticles (NP) ϕ, and magnetic field orientation combined effect provide a better understanding of heat transfer and entropy optimization. The results indicate that entropy production and heat transfer and rates depend on magnetic field intensity and direction. Also, increasing Ri and NP increases entropy generation and heat transfer. Finally, applying a radial magnetic field promotes a better convective heat transfer and minimizes entropy production.     

纯低温余热发电的动力利用分析

对低温余热资源量的统计与评价,除了用热力学第一定律分析其所含的资源量以外,还必须用热力学第二定律（（火用）分析法）对低温余热资源的作功能力及其动力利用的理论限度进行分析。根据余热资源的总量以及载热介质的比（火用）,可以科学地判断低温余热的作功能力及其动力利用的理论限度,从而合理地配置装机容量。     

水泥窑纯低温余热发电有机工质循环技术的应用探讨

针对目前水泥工艺的余热情况及我国水泥窑余热发电的技术现状，提出了采用以有机烷类和有机热载体为循环工质的纯低温发电系统进行纯低温余热回收的方案，以达到节能降耗的目的。     

Numerical analysis of MHD nanofluid flow over a wedge,including effects of viscous dissipation and heat generation/absorption,using Buongiorno model

The key purpose of this article is to examine magnetohydrodynamics flow, generative/absorptive heat, and mass transfer of nanofluid flow past a wedge in the presence of viscous dissipation through a porous medium. The investigation is completely theoretical, and the present model expresses the influence of Brownian motion and thermophoresis using the nanofluid Buongiorno model. The fundamental model of partial differential equations is reframed into the structure of ordinary differential equations implementing the nondimensional similarity transformation, which are tackled through the fourth–fifth-order Runge–Kutta–Fehlberg algorithm together with the shooting scheme. The analysis of sundry nondimensional controlling parameters, such as magnetic parameter, Eckert number, heat generation/absorption parameter, porosity parameter, Brownian motion parameter, and thermophoresis parameter on velocity, temperature, and concentration profiles are discussed graphically. The effects of the physical factors on the rate of momentum and heat and mass transfer are also determined with appropriate analysis in terms of skin friction, Nusselt number, and Sherwood number. The outcomes illustrate that the local Nusselt number and local Sherwood number are reduced for higher values of the thermophoresis parameter. Besides, it is found that higher estimations of heat generation/absorption and viscous dissipation parameters increase temperature. Moreover, it is found that the temperature profile increases with the involvement of the Brownian motion parameter, while an opposite trend is observed in the concentration profile. A comparison is also provided for limiting cases to authenticate our obtained results.     

Experimental investigation of a novel heat pipe thermoelectric generator for waste heat recovery and electricity generation

Waste heat recovery helps reduce energy consumption, decreases carbon emissions, and enhances sustainable energy development. In China, energy-intensive industries dominate the industrial sector and have significant potential for waste heat recovery. We propose a novel waste heat recovery system assisted by a heat pipe and thermoelectric generator (TEG) namely, heat pipe TEG (HPTEG),to simultaneously recover waste heat and achieve electricity generation. Moreover, the HPTEG provides a good approach to bridging the mismatch between energy supply and demand. Based on the technical reserve on high-temperature heat pipe manufacturing and TEG device integration, a laboratory-scale HPTEG prototype was established to investigate the coupling performances of the heat pipes and TEGs. Static energy conversion and passive thermal transport were achieved with the assistance of skutterudite TEGs and potassium heat pipes. Based on the HPTEG prototype, the heat transfer and the thermoelectric conversion performances were investigated. Potassium heat pipes exhibited excellent heat transfer performance with 95% thermal efficiency. The isothermality of such a heat pipe was excellent, and the heat pipe temperature gradient was within 15°C. The TEG's thermoelectric conversion efficiency of 7.5% and HPTEG's prototype system thermoelectric conversion efficiency of 6.2% were achieved. When the TEG hot surface temperature reached 625°C, the maximum electrical output power of the TEG peaked at 183.2 W, and the open-circuit voltage reached 42.2 V. The high performances of the HPTEG prototype demonstrated the potential of the HPTEG for use in engineering applications.     

齐鲁石化丙烯腈厂废水焚烧炉余热锅炉改造方案研究

简述了原有火管式废水焚烧炉余热锅炉的结渣原因 ,提出了改造方案 ,介绍了改造方案的结渣周期计算和技术经济分析 ,证明其在理论上有效可行 ,节能和经济效益显著.     

Flow and heat transfer in a porous medium saturated with a Sisko nanofluid over a nonlinearly stretching sheet with heat generation/absorption

This work is focused on steady flow and heat transfer in a porous medium saturated with a Sisko nanofluid (non‐Newtonian power‐law) over a nonlinearly stretching sheet in the presence of heat generation/absorption. Nonlinear PDEs are transformed into a system of coupled nonlinear ODEs with related boundary conditions using similarity transformation. The reduced equations are then solved numerically using the Runge–Kutta–Fehlberg fourth–fifth order method (RKF45) with Maple 14.0 software. The solutions depend on the power‐law index n and the effect of pertinent parameter such as the Brownian motion parameter, thermophoresis parameter, Lewis number, the permeability, and the heat generation/absorption on the dimensionless velocity, temperature, and nanoparticles volume fraction and also on the skin friction, local Nusselt, and Sherwood numbers are produced for values of the influence parameter. A rapprochement of the numerical results of the actual study with formerly published data detected an excellent agreement.     

纳米流体在螺旋通道中数值模拟的研究进展

纳米流体作为一种新型高效的换热介质,其在螺旋通道中的应用被广泛研究。尤其是通过单相和两相模型对其流动及传热特性进行数值模拟,是研究热点。介绍了单相模型中纳米流体物理参数的计算关联式,包括密度、比热、黏度及导热系数等,并分析了不同关联式对同一参数计算结果的影响;总结了单相模型下纳米流体在螺旋通道中的流动及传热特性,并与两相Lagrangian-Eulerian及Mixture模型下得到的结论进行对比分析;展望了未来研究的发展趋势。