基于太阳能热发电系统的纳米颗粒提升熔盐储热特性的研究

发布时间：2018-10-18 08:34

【摘要】：太阳能热发电技术是一种非常有潜力的新能源发电技术,太阳能热发电是太阳能利用的高品位方式,太阳能通过热的形式转换成电能需要经过多个能量转换过程,而其中对热能合理储存和利用是太阳能热发电技术成功与否的关键。相对于太阳能光伏发电方式电负荷的随机性和不可控,导致对电网的稳定不利来说,太阳能热发电技术加入大容量储能系统后将具有类似于常规水电、火电等可控负荷能力,便于调峰,有利于电网稳定。在太阳能热发电系统中,传热储热介质的选择要面对许多苛刻的要求,包括高能量密度、良好的稳定性、高热容量、良好的导热性,同时还要可以多次重复利用。熔盐作为非常有前景的储热介质得到了工业界的广泛关注。本文受到各国学者对纳米流体强化传热研究的启发。提出大胆假设,如果将碳纳米管加入盐类等固体介质中所形成的复合结构应该能大幅提升新型混合物热物性。因此率先提出了一种新型储热材料：多壁碳纳米管—熔盐复合材料。通过本文的研究,不仅提出一种新型、有潜力的储热纳米材料,并通过对其热物性提升机理和影响因素的研究,为纳米复合材料的传热换热提供一定的理论依据。在本文中,首先对多壁碳纳米管一熔盐复合材料强化热物性的影响因素进行分析。主要分析了的影响因素包括纳米颗粒浓度、分散性、纳米颗粒性质、粒径、不同盐种对效果的影响等。通过分析可发现,多壁碳纳米管以及纳米金颗粒都对熔盐的热物性有改善,这种改善与盐种无关、颗粒种类无关,主要取决于纳米颗粒的小尺寸效应以及分散程度和形貌特征。对热物性强化有较为明显影响的因素主要作用效果为提升复合材料的界面热阻,界面热阻是两相复合材料的热物性改变的最主要影响因素。进而提出用界面热阻理论来解释熔盐热物性的强化效果。为了进一步验证界面热阻的实用性,分别采用了模拟、实验两种手段尝试验证该理论。发现了界面热阻的存在证据并加以分析。
[Abstract]:Solar thermal power generation technology is a very potential new energy generation technology. Solar thermal power generation is a high-grade way of solar energy utilization. The conversion of solar energy to electric energy through the form of heat requires a number of energy conversion processes. The reasonable storage and utilization of thermal energy is the key to the success of solar thermal power generation technology. Compared with the randomness and uncontrollable load of solar photovoltaic power generation mode, solar thermal power generation technology will be similar to conventional hydropower, thermal power and other controllable load capacity when it is added to large capacity energy storage system. It is convenient to adjust the peak and is beneficial to the stability of power grid. In the solar thermal power generation system, the choice of heat transfer and heat storage medium must face many harsh requirements, including high energy density, good stability, high thermal capacity, good thermal conductivity, and can be reused many times. Molten salt, as a very promising heat storage medium, has attracted wide attention in industry. This paper is inspired by the research of nanofluid enhanced heat transfer. The bold assumption is that the composite structure formed by adding carbon nanotubes into solid media such as salts should greatly improve the thermal properties of the new mixture. Therefore, a new heat storage material, multi-wall carbon nanotube-molten salt composite, was proposed. Through the research in this paper, not only a new type of potential thermal storage nanomaterials are proposed, but also the mechanism of thermal properties enhancement and the influencing factors are studied, which provides a certain theoretical basis for the heat transfer and heat transfer of nanocomposites. In this paper, the factors affecting the thermal properties of multiwalled carbon nanotubes / molten salt composites are analyzed. The main influencing factors are the concentration of nanoparticles, dispersion, properties of nanoparticles, particle size and the effect of different salt species on the effect. It is found that both multi-walled carbon nanotubes and gold nanoparticles can improve the thermal properties of molten salt, which is independent of salt type and particle type, and mainly depends on the small size effect, dispersion degree and morphology of the nanoparticles. The main effect of these factors is to raise the interfacial thermal resistance of the composites, and the interfacial thermal resistance is the most important influence factor for the change of the thermo-physical properties of the two-phase composites. Furthermore, the theory of interfacial thermal resistance is proposed to explain the strengthening effect of molten salt thermal properties. In order to verify the practicability of interface thermal resistance, simulation and experiment are used to verify the theory. The existence evidence of interfacial thermal resistance was found and analyzed.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM615;TB383.1

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