双工质循环发电系统换热器温度参数选择的研究

通过建立双工质循环发电系统的计算模型和理论分析系统热力过程,对双工质循环发电系统中蒸发器的最佳蒸发温度以及蒸发器和凝汽器的最佳端部温差进行了优化选择。计算结果表明,最佳蒸发温度除与热水初温和冷凝温度有关外,也与端部温差有关,并随之增加而减少。在热水初温130℃及冷凝温度48℃下,得到蒸发器及凝汽器的端部温差优化值均为6℃,对应的最佳蒸发温度为87℃。     

低温热源喷射式冷电联产系统经济性分析

建立了低温热源喷射式冷电联产系统热力学模型,提出以换热器的总面积与输出有效能之比值Rap以及膨胀机入口比体积与输出有效能之比值Rvp为目标函数,对系统的经济性进行了分析,并对所选5种有机工质进行比较筛选.结果表明:在电冷比r=0.5的情况下,存在最佳冷凝温度tc=30℃左右和最佳制冷蒸发温度te=8℃左右,且有机工质R600为最优工作工质;低温热源喷射式冷电联产系统适宜电冷比较低的场合.     

非共沸混合工质ORC对低焓地热能的深度利用

以低焓地热能的深度利用为目标,用异戊烷、6种丁烷/己烷和5种异丁烷/己烷不同质量配比的二元非共沸混合物共12种物质作为亚临界ORC工质,利用窄点分析方法分析循环性能。研究表明,地热水进口温度在120~150℃时,混合工质异丁烷/己烷(0.65/0.35)的综合性能最佳,地热水出口温度最低,其输出净功率比纯工质异戊烷提高6.56~6.77倍;在150~170℃时,混合工质异丁烷/己烷(0.6/0.4)的综合性能最佳,地热水出口温度最低,其输出净功率比纯质异戊烷提高5.44~5.97倍;蒸发器和冷凝器是系统可用能损失主要部件,热源温度低时冷凝器中的可用能损失最大,但随着热源温度的升高,蒸发器的可用能损失所占比重将逐渐提高。     

对流热采油页岩过程低温余热ORC系统热力分析

为回收利用对流热采油页岩过程中产生的低温余热蒸汽,提出并设计有机朗肯循环(ORC)系统进行热力发电。在特定余热蒸汽参数条件下,基于R245fa循环工质,编制计算程序模拟分析了ORC系统变工况参数对该系统热效率及输出功率的影响规律。数值模拟结果表明:设定汽轮机背压为0.25MPa时,工质最高蒸发压力为2.566MPa,在此范围内,系统热效率随蒸发压力升高单调增加,增幅减缓;取蒸发器出口温度85℃时,对于不同的蒸发压力系统允许运行工质流量范围不同,在同一蒸发压力下,由于热源限制导致系统热效率并未随工质流量增加显著提高,但可得到更多输出净功;蒸发压力为1.5 MPa时,随余热排放温度的降低,系统输出净功显著提高;随汽轮机背压的降低,系统热效率得到明显改善,但汽轮机背压的降低增加了工质冷凝的困难,合适的背压值取0.2MPa。     

汽车尾气热源半导体温差发电系统构想

发电模块在温差仅为几十摄氏度的低温余热条件下也可发电,非常适合于汽车尾气为热源的变工况条件的系统发电。研究半导体温差发电模块用于以汽车尾气为热源的发电系统输出电压、电流随热源温度变化的趋势。发电系统采用4块发电模块串联的方式,热源温度的变化范围为75~38℃,冷源恒定且为5℃。测试结果表明:随热源温度变化,系统输出的电压、电流随热源温度呈线性变化;冷热源温差为70℃时,系统输出电压为5.2V,电流为0.22A。     

基于电气体发电的ORC系统热力学分析

构建了含电气体发电的ORC系统并对比于传统的汽轮机-发电机的发电方式,以发电功率和火用效率作为目标函数,基于热力学和电学理论,计算分析了亚临界状态下7种不同工质相应目标。研究表明,蒸发温度升高,系统发电功率增加。相同条件下,R134a有较大的输出电功率;热源进口温度一定,窄点温差越小,系统火用效率越大;同一窄点温差,热源进口温度不高于临界温度约2倍的窄点温差时,火用效率存在最大值;反之,火用效率则随蒸发温度单调递增。本研究将为ORC新型发电技术在工质选择和性能优化方面提供理论指导。     

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。     

低温余热有机朗肯循环发电系统热经济性分析

针对工业中排放的低温烟气,建立有机朗肯循环发电系统的热经济分析模型,分析蒸发压力、热源温度及蒸发器最小传热温差对系统经济性能的影响。分析结果表明:热源温度为140℃,循环采用R123的经济性最佳,相应的发电成本与动态投资回收期分别为0.142元(/kW.h)与3.68年。余热发电系统存在一个经济性最高的蒸发压力,不同工质对应的最佳蒸发压力也不同。蒸发器内最小传热温差为15℃时,系统的经济性较好。烟气温度在100～180℃时,系统采用R123的投资回收期最短,而烟气温度高于180℃时,R141b的经济性更高;不宜采用有机朗肯循环发电技术回收温度低于100℃的低温烟气。     

海洋温差能ORC系统多目标函数优化研究

以系统净功、不可逆能量损失等作为目标参数,建立海洋温差能ORC系统多目标函数优化体系,研究蒸发温度、冷凝温度、工质流量、温海水出口温度等对系统性能的影响。研究结果表明:存在最优参数值使得系统性能最优;冷凝温度越高,最优蒸发温度越高,系统目标值越大,系统性能越差;文章所选取的6种工质中,R227ea能耗最低,R141b能耗最高;温海水的适宜出水温度为19~20℃。     

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。     

Computation of IR sky temperature and comparison with surface temperature

The effects of atmospheric IR radiation must be accounted for in energy budget computations of solar collectors. IR radiation is often parameterized by determining an equivalent sky temperature dependent on surface temperature. Hourly values of IR radiation were computed at eleven stations in the United States in 1971 and 1972 and the equivalent sky temperature obtained. The model used for these computations was verified by comparison with special observations in the Lake Ontario region taken during the International Field Year of the Great Lakes (IFYGL) in 1972. Differences between surface temperature and sky temperature ranged between 5 and 20°C and are a complex function of season (specifically of cloudiness, humidity, and surface temperature) and geographical location.     

Fluctuations de temperature dans un ecoulement turbulent a temperature elevee

The thermal fields are generally studied for only weakly heated turbulent flows.Presented here are thermal field measurements executed in a grid created turbulent air flow. heated to 400°C. The flow is established in a circular section cylindrical tube. The reference dynamic field is characterized by Re = 20. The obtained results indicate that the small eddies' dissipation increases with the mean temperature. The thermal field seems to be more and more structured by big eddies; it is observed that the dimensions of the most energetic eddies and the dissipation micro-scales of the thermal field are growing with the flow mean temperature.     

数字温度传感器在动车组轴承温度检测中的应用

介绍了单线数字式温度传感器DS18B20的工作原理以及使用方法。给出了基于单片机和DS18B20的单线多点动车组轴承温度检测系统的硬件原理和程序设计。     

High temperature solar heated seasonal storage system for low temperature heating of buildings

A preliminary study of a solar-heated low-temperature space-heating system with seasonal storage in the ground has been performed. The system performance has been evaluated using the simulation models TRNSYS and MINSUN together with the ground storage module DST. The study implies an economically feasible design for a total annual heat demand of about 2500 MWh. The main objective was to perform a study on Anneberg, a planned residential area of 90 single-family houses with 1080 MWh total heat demand. The suggested heating system with a solar fraction of 60% includes 3000 m² of solar collectors but electrical heaters to produce peak heating. The floor heating system was designed for 30°C supply temperature. The temperature of the seasonal storage unit, a borehole array in crystalline rock of 60,000 m³, varies between 30 and 45°C over the year. The total annual heating costs, which include all costs (including capital, energy, maintenance etc.) associated with the heating system, were investigated for three different systems: solar heating (1000 SEK MWh⁻¹), small-scale district heating (1100 SEK MWh⁻¹) and individual ground-coupled heat pumps (920 SEK MWh⁻¹). The heat loss from the Anneberg storage system was 42% of the collected solar energy. This heat loss would be reduced in a larger storage system, so a case where the size of the proposed solar heating system was enlarged by a factor of three was also investigated. The total annual cost of the solar heating system was reduced by about 20% to about 800 SEK MWh⁻¹, which is lower than the best conventional alternative.     

超市室内温度分布测试与分区平衡温度分析

超市内陈列柜冷量的泄露容易引起其周边的气温下降,从而造成室内热舒适性降低,为此有必要详细分析陈列柜周边气温对超市室内温度分布的影响。选择典型超市,对其夏季室内温度分布进行了测量,发现超市环境中存在着明显的温度分布不均现象,进而导致电能的浪费。依据超市室内温度分布不均的特点,将其划分为三个区:陈列柜区、临近陈列柜区和远离陈列柜区。定义供冷与供热状态下陈列柜区的对比温度为陈列柜区温度与临近陈列柜区气温的比值,再根据热力学第一定律以及热传递原理,分别导出陈列柜区开始供冷与供热的对比温度计算表达式。引入分区平衡温度的概念,绘制出供冷与供热工况下,陈列柜区的两条分区平衡温度曲线。分析表明,陈列柜区的能耗控制需通过调整陈列柜泄露冷量与热回收量以及该区内空调或电加热开启之间的平衡来实现。     

Proton exchange membrane fuel cell from low temperature to high temperature: Material challenges

Proton exchange membrane fuel cell (PEMFC) is considered as one promising clean and highly efficient power generation technology in 21st century. Current PEMFC operating at low temperatures (<80 °C) encounters several difficulties, such as CO tolerance, heat rejection, which can be, to a great extent, surmounted at higher temperatures (120–150 °C). However, the higher temperature conditions are much more challenging to implement, particularly with regards to the durability of the cell component materials. This paper overviews the drivers behind the interest in high-temperature PEMFC, and the challenges in developing novel materials to enable high-temperature PEMFC, including cell component durability (catalysts, polymer, bipolar plates, etc.), candidate polyelectrolytes for the electrode catalyst layer, and material compatibility in novel membrane electrode assembly (MEA), and provides an insight into the material research and development for PEMFC.     

常温小温差下的分离式热管换热器充液率研究

分离式热管散热器具有小温差下的高效传热能力,可在一定条件下替代室内空调系统,以达到节能减排的目的。针对分离式热管散热器的应用之需,根据两相流理论和R22工质的热力学性质,建立了最佳充液率的理论模型,进行了最佳充液率的计算及实验研究,分析了不同充液率下蒸发器和冷凝器管壁温度分布的实验结果,讨论了在常温小温差条件下水平布置分离式热管散热器的最佳充液率范围。