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高温热泵作为一种有效的节能技术可以满足大多数的工业用热需求,遴选安全、环保、高效的制冷剂是当前高温热泵技术研究的重要工作之一。针对闪蒸补气式高温热泵,基于EES(Engineering Equation Solver)软件建立系统数学模型,以性能系数(COP)、制热量、单位容积制热量、冷凝压力、压缩比以及压缩机排气温度为性能指标,在冷凝温度 ≥ 100℃,温升分别为40℃、50℃和60℃工况下,对R1224yd(Z)、R1233zd(E)、R1336mzz(Z)和R1234ze(Z) 四种氢氟烯烃制冷剂在闪蒸补气式热泵系统中的应用潜力进行分析,并与R245fa比较。结果表明,R1336mzz(Z) 的COP最大、冷凝压力最低,但单位容积制热量最小,相对适用于小容量供热系统;R1234ze(Z)的单位容积制热量最大,且COP与R245fa相当,是R245fa的良好替代工质,尤其适用于大容量高温升供热系统;R1233zd(E) 虽然单位容积制热量偏低,但其COP、制热量和冷凝压力相对R245fa具有显著优势,亦可作为R245fa的替代工质;与R245fa相比,R1224yd(Z) 的热力性能无明显优势。 相似文献
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针对中温地热能的利用,建立了有机朗肯-复叠式制冷系统的热力学模型,其中高温部分分别采用R245fa,R600a,R141b做工质,低温部分利用R744做工质。通过热力学模拟计算,分析了该系统性能系数COPs在低温级冷凝温度、高温级冷凝温度、低温级蒸发温度改变时的变化规律,并以系统性能系数COPs及高低温级质量流量比G作为评价指标,优选出最佳工质。分析表明:系统存在一个最佳低温级冷凝温度,使系统性能系数COPs最大;在一定运行工况下,系统的COPs随着蒸发冷凝器传热温差的加大而逐渐减小,随着高温级冷凝温度的升高而降低,随着低温级蒸发温度的升高而增高;高低温级质量流量比G随着低温级蒸发温度的升高而逐渐降低。为提高系统性能和保证系统的安全运行,应尽可能提高低温级蒸发温度、降低高温级冷凝温度和减小蒸发冷凝器传热温差。综合比较,以R141b/R744为工质的有机朗肯-复叠式制冷循环具有很好的发展前景。 相似文献
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热泵开水器具有较高的能源利用效率,是公共场所电加热开水装置的理想替代品。从提高能源效率和一机两用的角度,构建了一种高温复合热泵开水器系统。建立了系统热力学模型,选R236fa、R245fa、R365mfc、R245ca、RC318和R236ea等6种较高临界温度的制冷工质,通过能量分析和[火用]分析的方法,探讨了不同制冷工质对高温复合热泵开水器系统性能的影响。研究结果表明:R245fa作为工质的高温复合热泵开水器系统具有最佳的性能,而以RC318作为工质的系统性能最差。在给定工况下,R245fa作为工质系统制热性能系数(COPh)为2.47,而其制冷性能系数(COPc)为3.37,[火用]损失和[火用]效率分别为9.47 kW和49.07%;与R245fa相比,RC318作为工质系统的总能耗增加了39.53%。 相似文献
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《太阳能学报》2020,(5)
计算单工质R124、R152a、R245fa和混合工质R152a/R124、R152a/R245fa的理论循环性能,并实验对比。实验工况为蒸发侧进口水温40~50℃,冷凝测进口水温70~85℃,热泵机组额定输入功率4.5 kW,2种混合物质量配比分别为50/50、30/70、20/80和30/70、50/50、70/30,其中R152a/R124(30/70)和R152a/R245fa(30/70)的制热功率和循环效能综合表现较优;在50℃热源进水和75℃高温进水工况下,二者电力循环性能系数在3.0以上,后者稍高;但在制热功率方面前者比后者高出19.0%,可达15.2 kW。 相似文献
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针对热源为80~150℃热水的有机朗肯循环(ORC)发电系统,以发电功率和效率为评价指标,分别分析了以R134a、R123和R245fa三种工质为循环介质时的系统,确定了最佳循环参数和工质。一般来说,最佳蒸发温度对应着最大的输出电功,且随着热流体温度的升高而升高;当热源温度大于120℃时,R134a的系统不存在最佳蒸发温度,此时输出电功随着蒸发温度的升高而增大。对于80~135℃的热水,工质R245fa的发电功率最大;当热水温度超过135℃时,工质R134a的发电功率最大。工质R245fa的发电效率始终是最大的。 相似文献
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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。 相似文献
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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%。 相似文献
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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. 相似文献
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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。 相似文献
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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。 相似文献
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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. 相似文献
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High temperature solar heated seasonal storage system for low temperature heating of buildings 总被引:1,自引:0,他引:1
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. 相似文献
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Mixtures of cyanogen and nitrous oxide diluted in argon were shock heated to measure the ratio of the rate constants for
(3)
and (4)
The diagnostic was narrow-line absorption of NCO at 440.479 nm using a remotely located cw ring dye laser source. By varying the mole fraction of nitrous oxide in the initial mixture and conducting otherwise identical experiments, we inferred at 2240°K Utilizing a recent determination of k3 and previous measurements of the ratio , we recommend over the temperature range 2150 ? T ? 2400°K An additional mixture of cyanogen, oxygen, hydrogen, and nitrous oxide diluted in argon was shock heated and NCO was monitored to infer the rate constant for (5)
and the ratio : (6)
(7)
We found near 1490°K and These experiments also led to an estimate of the rate constant for (8)
with the result, near 1490°K, 相似文献
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为了解决储煤筒仓因煤体发生自燃而引发事故的难题,采用实验研究的方法,搭建储煤筒仓实验台,利用人工热源模拟自燃高温热源,对松散煤体温度场进行研究,分析不同测点距离、热源强度和热源相对位置对温度场的影响。结果表明:储煤筒仓内松散煤体温度场与热源强度、时间、距离等多种因素相关,其中,受热源强度影响更加明显;当热源温度低于150℃时,对流影响区域远小于导热影响区域;当热源温度高于200℃时,导热因素对温度场的影响占主要地位;对比筒仓壁面同层以及同列温度测点之间的温度变化趋势,可以推出高温热源的位置并监测筒仓储煤温度场,有利于预防储煤自燃。 相似文献