Operation strategies of axial flow fans in a direct dry cooling system under various meteorological conditions

For a direct dry cooling system, the turbine back pressure fluctuates with the meteorological conditions. Moreover, the operation of axial flow fans plays an important role in the cooling performance of air-cooled condensers (ACC). It is of significant use to study the operation strategies of axial flow fans under various ambient conditions. Based on typical 2 × 660 MW direct dry cooling power generating units, the ACC model coupled with the turbine thermodynamic characteristics is developed, by which the thermo-flow performances of the ACC are predicted in the dominant wind direction, and then the standard coal consumption is calculated. The results show that the increased ambient temperature and wind speed, or the reduced fan rotational speed leads to the high turbine back pressure. At the low ambient temperature and wind speed, the standard coal consumption rate of the unit can be reduced by reducing the speed of axial flow fans appropriately, with the maximum drop in coal consumption rate reached 0.734 g/(kWh) when the ambient temperature is 10°C without wind. If the wind speed exceeds 12 m/s or the ambient temperature reaches 25°C, 110% of the rated fan rotational speed is recommended.     

冬季自然通风状态下直接空冷凝汽器的性能

直接空冷电厂的安全运行与空冷凝汽器在冬季自然通风条件下的换热性能有着密切的联系.依托实际工程项目,确定了某135MW直接空冷凝汽器(ACC)冬季自然通风下的热压.利用计算传热学(NHT)软件FLUENT,对不同迎面风速下,直接空冷凝汽器双排管换热元件的冬季性能进行了数值模拟、分析和研究.根据空气的作用压力与流经空冷凝汽器时所产生阻力之间的对应关系,确定了冬季自然通风状态下空冷凝汽器性能.它为直接空冷系统的优化设计提供帮助.     

变容量家庭能源中心单独制热水模式的实验研究

提出了可全年供应空调和热水需要的变容量家庭能源中心系统,并提出单独制热水模式下的性能系数计算方法。通过对该模式瞬时动态特性的研究,指出变容量压缩机可以有效地保证机组的安全可靠运行。实验研究了单独制热水模式在不同环境温度、不同压缩机负荷条件下的性能。结果表明,在同一压缩机负荷条件下,热水性能系数均随环境温度的升高而升高,与传统热泵热水器的变化趋势相同。而压缩机负荷变化对机组热水性能系数的影响在不同的环境温度下呈现不同的规律,因此,可根据不同的环境温度优化控制压缩机负荷,以提高制热水效率,节约能源。     

火电机组直接空冷系统初始温差的优选

分析了影响火电机组直接空冷系统初始温差优选的主要因素,阐述了初始温差优选的原理和计算步骤,讨论了空冷凝汽器管束迎面风速选定的依据;结合某电厂的厂址气象条件和运行要求,对300MW机组直接空冷系统的年总费用进行经济性分析,给出直接空冷系统初始温差优选的计算结果。     

环境因素对直接空冷机组的影响

直接空冷机组的运行状况受周围环境的影响很大,不同的风速、风向不仅会影响到机组运行的经济性,甚至还会造成掉闸停机事故。本文在总结火力发电厂空冷系统特点的基础上,对现场环境及所采集数据进行了系统分析,重点研究了环境作用对直接空冷机组空冷风机吸入风量和入口温度以及空冷机组背压影响,同时分析了环境温度的变化对空冷机组供电煤耗的影响。     

太阳能中温集热利用制蒸汽系统性能研究

构建了一套供热功率为310kW的太阳能中温集热利用制蒸汽系统,建立了系统主要模块——太阳能集热器与热変换器的热力学模型,研究了变工况下太阳辐射强度、凝水回收比、环境温度对系统效率和供热功率的影响,探讨了不同运行参数条件下集热温度与系统性能之间的关系。研究结果表明:增大辐射强度对系统性能提升显著;回收凝水对系统效率的影响不大,但对制热功率的提升较为明显;系统性能随环境温度升高呈先上升后下降的趋势;系统存在最佳集热温度,最佳集热温度随辐射强度和环境温度的增大而升高。     

Influence of ambient temperature on combined-cycle power-plant performance

Thermal-power electricity are important mainly because of the need for diversified power-generation and the availability of natural gas, the main fuel used in this type of electricity-generating system. With the implementation of the priority plan for thermal-power plants in Brazil, dozens of units will be installed which will make it possible to transform the Brazilian electric system, today mainly based in hydraulic principles, into a hydro-thermal system. The operation of a combined cycle thermal-power plant is influenced by the conditions that are present at the place where it is installed, mainly ambient temperature, atmospheric pressure and the air's relative-humidity. These parameters affect the generated electric-power and the heat-rate during operation. Among these variables, the ambient temperature causes the greatest performance variation during operation. That is the reason why the influence of this variable on this type of generating unit is studied. The plant selected for this study has a multiple-shaft configuration and is composed of two Siemens AG 501F gas-turbines, coupled to three pressure levels HRSGs and re-heating with supplementary firing and a steam-turbine. The most relevant results obtained from a thermodynamic simulation, in which the Gate Cycle Software version 5.51.0.r was used, are the curves of generated power, as well as the heat rate and thermal efficiency as functions of ambient temperature and the supplementary firing.     

Thermal modeling and cooling analysis of high-power lithium ion cells

The heat generation model and three-dimensional computational fluid dynamics model for lithium ion cells were established with boundary conditions defined.In order to provide a better insight about the behaviors of high-power lithium ion cells under realistic discharge conditions,the temperature difference of the cells and an active thermal management system with a pure air-cooling mode were analyzed and predicted with the factors affecting the unevenness of temperature field discussed.The results show a significant effect of the cooling flow rate on the temperature rise of the cells for all discharge rates.Average surface temperatures are relatively uniform at lower discharge rate that makes it easier to control the temperature of the pack.Cell temperatures are expected to rise significantly toward the end of discharge and they show non-uniformity at higher discharge rates.Adequate air flow rate of active cooling is required at high discharge rate and high ambient temperature for practical pack thermal management system.     

垃圾焚烧炉炉排风量测量方法的比较研究

自动燃烧控制(ACC)系统是垃圾焚烧自动控制的核心技术。基于ACC系统原理,并结合垃圾焚烧炉在不同场景下的风量测量特点,分析了均速管流量计、双文丘里流量计、热式质量流量计等主流流量计的测量原理和优缺点,为垃圾焚烧发电厂流量计选型提供依据。     

Active (air-cooled) vs. passive (phase change material) thermal management of high power lithium-ion packs: Limitation of temperature rise and uniformity of temperature distribution

The effectiveness of passive cooling by phase change materials (PCM) is compared with that of active (forced air) cooling. Numerical simulations were performed at different discharge rates, operating temperatures and ambient temperatures of a compact Li-ion battery pack suitable for plug-in hybrid electric vehicle (PHEV) propulsion. The results were also compared with experimental results. The PCM cooling mode uses a micro-composite graphite–PCM matrix surrounding the array of cells, while the active cooling mode uses air blown through the gaps between the cells in the same array. The results show that at stressful conditions, i.e. at high discharge rates and at high operating or ambient temperatures (for example 40–45 °C), air-cooling is not a proper thermal management system to keep the temperature of the cell in the desirable operating range without expending significant fan power. On the other hand, the passive cooling system is able to meet the operating range requirements under these same stressful conditions without the need for additional fan power.     

太阳能光伏光热一体化系统运行实验研究

太阳能光伏光热一体化系统（hybrid photovoltaic-thermal solar system—PVT系统）作为一种利用太阳能同时获得电收益和热收益的新型能源利用方式,近年来受到学者的广泛关注。本文搭建了PVT系统电、热性能综合实验台,通过全天实验,分别研究和分析了系统的温度特性与相对电效率的关系。结果袁明,在日照条件较好,系统循环水温较低的情况下,PVT系统的电效率与普通光伏电池相比可以提高约7％。同时,文章还分析了PVT系统内水的温度一天内的变化情况,提出了在午后太阳辐射强度逐渐减弱,环境温度逐渐升高时如何保持PVT系统较高电效率的方法。     

Transient analysis of integrated Shiraz hybrid solar thermal power plant

Shiraz solar thermal power plant is designed for 250 kW power supply during available sun radiation. It is decided to promote the field of collectors by installing a large parabolic collector and combining the system with a 500 kW hybrid boiler. For the new integrated configuration, thermodynamic analysis is required for engineering design and evaluating thermal performance.For the new system, transient simulation is performed under different working conditions. In the plant, each component is simulated transiently, by considering initial condition and capacity rate of the component as well as all the connecting pipes and instruments. Results of the simulation for thermal performance are compared with field experimental measurements for several periods. Taking into account the thermodynamic concepts and the results of numerical and experimental analysis, the best operation strategies are selected for optimum performance and control philosophy based on the new integrated collector.     

Effects of ambient conditions on the thermodynamic performance of hybrid nuclear‐combined cycle power plant

This paper provides a theoretical study of the effects of ambient conditions on the thermodynamic performance of a hybrid combined‐nuclear cycle power plant. The operational parameters investigated are based on the first and second laws of thermodynamics, which include the ambient air temperature and ambient relative humidity (Φ). The results obtained for the gas turbine model are shown to agree very well with operational data from the Al‐Zour Emergency power plant in Kuwait. The ambient temperature was studied within the range of 0–55 °C. The analysis shows that the ambient air temperature has strong effects on plant performance and that operating the system at a high temperature will degrade the performance. Power output is reduced when the temperature is above the standard ambient temperature of 15 °C, and this loss rate is about 17% at 55 °C. The effect of ambient relative humidity (Φ) becomes significant only at higher temperatures. The ambient temperature has a large effect on the exergy destruction of the heat recovery steam generator exhaust, but it has little effect on other components of the plant. The analysis also indicates that reducing the temperature from 55 to 15 °C could help decrease the total exergy destruction of the plant by only 2%. Copyright © 2011 John Wiley & Sons, Ltd.     

直接空冷系统风机转速的优化研究

为了更好的调节直接空冷系统的风机转速以提高机组经济性,选取空冷岛冷却单元为研究对象,综合考虑冷却单元内蒸汽压力、风机转速和环境温度对机组功率增量的影响,并建立了相关的数学模型。进而以机组功率增量与风机耗电量之间的差值最大为目标进行优化,得出不同工况下最佳冷却单元内蒸汽压力和风机转速,为直接空冷机组的经济运行提供了参考。     

300MW燃煤电厂热力系统仿真研究

基于过程系统工程的建模和仿真原则,针对某电厂300MW燃煤机组开发了一套稳态热力学仿真系统,并详细阐述了模型建立的基本思路和方法,通过改变输入参数、负荷和环境条件,仿真电厂在不同工况下的运行特性．结果表明：系统仿真所获得的结果与实际电厂的性能测试数据相比误差不超过2％;通过仿真可获得主要物流、能流的热力学参数（包括质量流量、温度、压力、比焓、比熵等）和主要设备的运行参数（包括汽轮机和泵的等熵效率、加热器端差、热传导系数等）,为燃煤电厂的实际运行优化、炯分析、热经济学分析等提供基础数据．     

用于联合循环机组的复合循环间接空冷系统设计及分析

论述了联合循环机组发展前景,阐述燃气-蒸汽联合循环采用间接空冷系统的重要性。介绍了发电厂空冷系统,分析了各种空冷技术应用于生产实际的优缺点,提出联合循环采用复合循环间接空冷系统模式,分别对其设计计算过程进行了讨论,对压缩机-空冷凝汽器性能影响因素进行了分析,对性能变化规律进行了研究。结果表明：复合循环间接空冷系统设计要综合考虑气象条件,尤其是环境风速、制冷量和空冷电站平面布局的影响。     

建三江热电厂首站改造及运行方案

通过分析建三江热电厂现有供热系统存在的问题,提出对首站进行改造方案,解决供热存在的问题.改造方案既考虑近远期供热需求,也保证电厂出现最不利情况的供热要求.同时提出随着供热面积的增加,供热方式也由直供调整为混水直供的方式的运行方案,在满足城市供热的基础上,最大限度利用热电厂热源的余热.     

火电厂低低温烟气处理系统烟气余热利用研究

低低温烟气处理系统与传统的除尘、脱硫工艺相比,具有良好的节能环保性能。从热力学性能和经济效益两方面分析比较了低低温高效烟气处理系统中两种烟气余热利用的方案,并以国产600 MW空冷机组为例,进行了定量分析比较。定量计算结果得出的结论对低低温烟气处理系统在中国火电厂推广使用具有一定的指导意义。     

Performance evaluation of a thermodynamic solar power plant: fifteen years of operation history

The thermodynamic solar power plant of the National Institute for Scientific Research in Tunisia has been in operation since 1984. The plant served as a pilot unit for exploring the technical reliability and evaluating the economic feasibility of the process of converting solar thermal energy into electricity. This paper consists of a close evaluation and analysis of the long-term performance of the system and a review of 15 years of successful operation. The aim of this study was to go over the main problems and technical difficulties encountered and pinpoint the major factors affecting the plant operation in order to identify the optimal operating policies toward the enhancement of the plant efficiency. Even though the thermal performance of the plant was relatively low, the impact of such a plant on the energy sector of the country was significant in terms of energy saving and environmental protection. In regions with high solar radiation such as Tunisia with a daily mean insolation of 4.8 kWh m⁻², the use of solar power plants — similar to this one — essentially for heat production prove to be a good alternative especially for remote and rural areas.