槽式太阳能热发电双罐式熔融盐间接储热系统设计研究

在槽式太阳能热发电储热系统的作用及特点基础上,综述了几种主要储热形式,双罐式熔融盐间接储热系统在槽式太阳能热发电中应用最为广泛。通过对比各种储热介质的配比成分、物理特性和成本,确定了用于槽式太阳能热发电双罐式熔融盐间接储热系统的熔融盐介质,并给出了该熔融盐的物理性质及品质要求。提出储热系统设备选型原则及槽式太阳能双罐式熔融盐间接储热系统设备布置的推荐意见,并进一步提出储热系统的运行模式及运行要求。     

现场测试地下岩土平均热物性参数方法

平均热物性参数的大小对钻孔的数量及钻孔的深度具有显著的影响,进而影响地源热泵系统的初投资。为了能够在现场测量地下岩土的平均热物性参数,利用一套现场测量设备测量了对地下埋管回路施加的热流与回路中循环水温度随时间的变化,使用自行开发的软件,采用参数估计方法,计算并确定了地下岩土的平均热物性参数。     

低熔点四元混合硝酸盐的开发与实验研究

优选出一种熔点较低、分解温度较高的新型低成本四元混合硝酸盐,对其熔点、分解温度、潜热、比热、密度、热扩散系数、导热系数以及热稳定性进行实验与分析,并基于实验数据对于优选的混合熔盐的显热蓄热成本进行计算,结果表明该低成本四元混合硝酸盐在熔点、分解温度、成本、热稳定性等方面都具有显著优势,有作为中高温传热蓄热介质在太阳能热...     

Li2CO3/Na2CO3/K2CO3及其混合熔融盐储热材料热物性分子动力学研究

对Li₂CO₃/Na₂CO₃/K₂CO₃及其二元和三元混合熔融盐的密度、比热容、黏度、热导率进行分子动力学模拟(MD),对比得出模拟结果与现有的实验数据和模拟值相近。结果表明：随着温度的升高,密度逐渐减小,离子之间的距离增加,导致对剪切应力的抵抗力变小,这说明单组分、二元和三元熔融盐黏度的负温度依赖性。对于熔融盐的热导率,单组分和二元熔融盐也呈现出负温度依赖性,而三元熔融盐趋势是随温度的升高呈上升状态。     

应用于储热领域的混合钠基废盐热物性分析

近年来工业废盐的堆积量剧增引发一系列环境问题。废盐的处置方法已成为制约废盐资源化利用的瓶颈。针对以NaCl和Na₂SO₄为主要成分的工业废盐(杂质离子包含钙、镁、钾等金属离子),本工作提出利用钠基废盐作为储热材料的处置思路并对其热性能进行分析。采用分子动力学方法,分析废盐中主要杂质对钠基盐体系热物性影响。进一步通过高温熔融法制备二元钠基共晶盐NaCl-Na₂SO₄,分别添加质量分数为1%和5%的KCl模拟含有微量K+废盐,研究其对混合盐热物性影响。结果表明K⁺对钠基盐的热物性有显著提升,含有1%和5%KCl的混合钠基盐相比二元钠基共晶盐的相变潜热分别提高了64%和60%,导热系数提高了2～3倍。K⁺的存在有利于废盐热物性改善,为该类固废资源化利用提供了途径。     

塔式太阳能热发电吸热器技术进展

文中介绍了现有塔式太阳能热发电吸热器技术,针对不同吸热器结构和传热介质,结合国内外现有主要塔式太阳能热发电站,对吸热器性能进行比较研究。结果表明,外露管式吸热器结构简单、造价低,应用广泛;而熔盐作为传热和蓄热介质具有较好的性能,系统无压运行且能承受高热流密度,是将来的研究方向。     

新型相同钠离子混合熔盐相图预测及物性测量

为了提高第三代聚光式太阳能热发电技术的效率,降低系统的运行成本,需要开发出具有更高使用温度的新型高温储热/蓄热材料.本文基于相同阳离子的原则,选取3种相同钠离子熔盐NaNO3、NaCl、Na2CO3作为基盐,借助相图原理指导混合熔盐的配制,通过FactSage软件对NaNO3-NaCl-Na2CO3三元体系进行相图热力...     

氯化物熔盐单质及其混合物热物性子动力学模拟研究

采用分子动力学模拟的方法对3种常用的氯化物熔盐单质（KCl、NaCl和LiCl）、二元混合氯化物熔盐（LiCl-KCl和 LiCl-NaCl）和三元混合氯化物熔盐（KCl-LiCl-NaCl）的比热容、粘度和热导率进行系统研究。研究中粘度采用平衡分子动力学方法进行计算,而热导率采用非平衡分子动力学方法进行计算。结果表明,3种氯化物熔盐单质的比热容模拟值与实验值相比误差均在6.8%以内;NaCl、KCL、LiCl熔盐单质的粘度平均误差分别为5.3%、10.9%以及11.7%;热导率除了LiCl外,其余两种氯化物熔盐的热导率误差均在9%以下。与文献不同混合比例的NaCl-KCl的热导率平衡分子动力学方法模拟值比较,偏差均在12.5%以内。综合结果表明模拟结果均与实验值表现出较好的一致性。为了更好地从微观结构上理解氯化物熔盐的热物性,通过计算径向分布函数对熔融盐体系及局部结构进行分析。     

三元混合碳酸熔盐热物性实验研究

为满足超临界二氧化碳太阳能光热发电系统高温传热储热的要求,对3种不同比例的高温混合碳酸熔盐的热物性进行研究.实验结果表明,1号、2号、3号混合碳酸熔盐的熔点分别为388.7、337.9、391.3℃;初晶点分别为454.9、639.7、535.4℃;1号、3号混合碳酸熔盐的分解温度分别为916.2、920.4℃.通过分...     

单相电极盐浴炉熔盐电阻计算及电极尺寸设计

本文研究了单相马蹄形、平行板形(相对或同侧)电极盐浴炉熔盐电阻的计算及电极尺寸的设计方法。实践表明,文中的计算方法可满足工程要求。     

Gasification characteristics of organic waste by molten salt

Recently, along with the growth in economic development, there has been a dramatic accompanying increase in the amount of sludge and organic waste. The disposal of such is a significant problem. Moreover, there is also an increased in the consumption of electricity along with economic growth. Although new energy development, such as fuel cells, has been promoted to solve the problem of power consumption, there has been little corresponding promotion relating to the disposal of sludge and organic waste. Generally, methane fermentation comprises the primary organic waste fuel used in gasification systems. However, the methane fermentation method takes a long time to obtain the fuel gas, and the quality of the obtained gas is unstable. On the other hand, gasification by molten salt is undesirable because the molten salt in the gasification gas corrodes the piping and turbine blades. Therefore, a gasification system is proposed by which the sludge and organic waste are gasified by molten salt. Moreover, molten carbonate fuel cells (MCFC) are needed to refill the MCFC electrolyte volatilized in the operation. Since the gasification gas is used as an MCFC fuel, MCFC electrolyte can be provided with the fuel gas. This paper elucidates the fundamental characteristics of sludge and organic waste gasification. A crucible filled with the molten salt comprising 62 Li₂CO₃/38 K₂CO₃, is installed in the reaction vessel, and can be set to an arbitrary temperature in a gas atmosphere. In this instance, the gasifying agent gas is CO₂. Sludge or the rice is supplied as organic waste into the molten salt, and is gasified. The chemical composition of the gasification gas is analyzed by a CO/CO₂ meter, a HC meter, and a SO_x meter gas chromatography. As a result, although sludge can generate CO and H₂ near the chemical equilibrium value, all of the sulfur in the sludge is not fixed in the molten salt, because the sludge floats on the surface of the carbonate by the specific gravity of sludge lighter than the carbonate, and is not completely converted into CO and H₂. Moreover, the rice also shows good characteristics as a gasifying agent. Consequently, there is high expectation to using the organic waste as a molten salt gasifying agent. However, this requires lengthening the contact time between the organic waste and the molten salt.     

Thermal characteristics and performance of salt gradient solar ponds

A mathematical model with various parameters such as effective absorptivity-transmitivity product and total heat loss factor, including ground losses and angle of refraction, which are related to the physical properties and dimensions of the pond, is developed to study the thermal behaviour of salt gradient solar ponds at different operational conditions. A linear relation is found between the efficiency of the solar pond and the function (ΔT/H ). The convective heat loss, the heat loss to the atmosphere due to evaporation through the surface of the pond and ground heat losses have been accounted for in finding out the efficiency of the pond. The dependence of the thermal performance of the solar pond on the ground heat losses is investigated and minimized using low cost loose and insulating building materials such as dry dunes and, Mica powder and loose asbestos at the bottom of the pond. The ground heat losses are considerably reduced with the asbestos (loose) and the retention power of solar thermal energy of the pond increases.     

Transient characteristics of small molten salt reactor during blockage accident

This paper reports the results from a transient core analysis of a small molten salt reactor (MSR) when a duct blockage accident occurred. The focus of this study is a numerical model employed in order to consider the interaction among fuel salt flow, heat transfer, and nuclear reactions. The numerical model comprises continuity and momentum conservation equations for fuel salt flow, two‐group neutron diffusion equations for fast and thermal neutron fluxes, transport equations for six‐group delayed neutron precursors, and energy conservation equations for fuel salt and graphite moderators. The analysis results show the following: (1) the effect of the self‐control performance of the MSR on the effective multiplication factor and thermal power output of the reactor after the blockage accident is insignificant, (2) fuel salt and graphite moderator temperatures increase drastically but locally at the blockage area and its surroundings, (3) the highest fuel salt temperature after the blockage accident is 1,363 K; this value is lower than the boiling point of fuel salt and the melting temperature of the reactor vessel, (4) the change in the distributions of fast and thermal neutron fluxes after the blockage accident when compared with the distributions at the rated condition is very slight, and (5) delayed neutron precursors, especially the first delayed neutron precursor, accumulate at the blockage area due to its large decay constant. These results imply that the safety of the MSR is assured in the case of a blockage accident. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(6): 434–450, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20123     

Thermovoltaic properties of technical silicon melted by solar radiation

The thermovoltaic characteristics of the p-n junction fabricated on the basis of technical silicon melted by means of solar radiation have been measured. The thermovoltaic effect that becomes apparent at temperatures T ≥ 60°C has been detected. This effect is evidently associated with the thermal generation of electron-hole pairs with the participation of impurities and surface states of intergrain boundaries.     

Solidification and melting behaviors and characteristics of molten salt in cold filling pipe

The solidification and melting phenomena and performances of molten salt during cold filling process in a straight pipe are numerically investigated using volume of fluid model. As the molten salt is filled into a cold pipe, the molten salt adjacent to the cold wall is rapidly cooled, and the solidification phenomena appears. After the whole pipe is filled, the solidification layer begins to melt by high temperature fluid heating. Because of the solidification layer, the flow section obviously shrinks, and the pressure loss remarkably increases. During the solidification and melting processes, the fluid temperature in the region with phase change only varies near the freezing point, and it quickly rises after the melting process. Because of the absorption or release of latent heat, the boundary heat flux of molten salt is increased in the solidification region, while it will be decreased in the melting region. As the inlet temperature rises, the pressure loss apparently decreases with the thickness of solidification layer decreasing. However, when the inlet flow velocity increases, the thickness of solidification layer decreases, but the flow resistance without phase change increases, so the pressure loss has a maximum at moderate flow velocity.     

Acoustic emission characteristics of steels part 1: Acoustic measurements from tensile tests

Acoustic emission measurements have been made in conjunction with ambient temperature tensile tests on nine structural steels with yield strengths ranging from 247–1606 MNm^?2 (16–104 t/in²). The acoustic activity is shown to be associated with initial yielding of the steels. The relative amounts of emission monitored during the tests have permitted an ‘emission’ rating of the steels to be made. Acoustic emission has been shown to increase with increasing strength and decreasing ductility of the steels. Tests to check ‘recovery’ phenomena have confirmed the absence of significant acoustic emission on second loading until the initial load has been attained—the Kaiser effect.