【摘要】：太陽能熱發(fā)電技術(shù)是一種非常有潛力的新能源發(fā)電技術(shù),太陽能熱發(fā)電是太陽能利用的高品位方式,太陽能通過熱的形式轉(zhuǎn)換成電能需要經(jīng)過多個能量轉(zhuǎn)換過程,而其中對熱能合理儲存和利用是太陽能熱發(fā)電技術(shù)成功與否的關(guān)鍵。相對于太陽能光伏發(fā)電方式電負(fù)荷的隨機(jī)性和不可控,導(dǎo)致對電網(wǎng)的穩(wěn)定不利來說,太陽能熱發(fā)電技術(shù)加入大容量儲能系統(tǒng)后將具有類似于常規(guī)水電、火電等可控負(fù)荷能力,便于調(diào)峰,有利于電網(wǎng)穩(wěn)定。 在太陽能熱發(fā)電系統(tǒng)中,傳熱儲熱介質(zhì)的選擇要面對許多苛刻的要求,包括高能量密度、良好的穩(wěn)定性、高熱容量、良好的導(dǎo)熱性,同時還要可以多次重復(fù)利用。熔鹽作為非常有前景的儲熱介質(zhì)得到了工業(yè)界的廣泛關(guān)注。 本文受到各國學(xué)者對納米流體強(qiáng)化傳熱研究的啟發(fā)。提出大膽假設(shè),如果將碳納米管加入鹽類等固體介質(zhì)中所形成的復(fù)合結(jié)構(gòu)應(yīng)該能大幅提升新型混合物熱物性。因此率先提出了一種新型儲熱材料：多壁碳納米管—熔鹽復(fù)合材料。通過本文的研究,不僅提出一種新型、有潛力的儲熱納米材料,并通過對其熱物性提升機(jī)理和影響因素的研究,為納米復(fù)合材料的傳熱換熱提供一定的理論依據(jù)。 在本文中,首先對多壁碳納米管一熔鹽復(fù)合材料強(qiáng)化熱物性的影響因素進(jìn)行分析。主要分析了的影響因素包括納米顆粒濃度、分散性、納米顆粒性質(zhì)、粒徑、不同鹽種對效果的影響等。通過分析可發(fā)現(xiàn),多壁碳納米管以及納米金顆粒都對熔鹽的熱物性有改善,這種改善與鹽種無關(guān)、顆粒種類無關(guān),主要取決于納米顆粒的小尺寸效應(yīng)以及分散程度和形貌特征。對熱物性強(qiáng)化有較為明顯影響的因素主要作用效果為提升復(fù)合材料的界面熱阻,界面熱阻是兩相復(fù)合材料的熱物性改變的最主要影響因素。 進(jìn)而提出用界面熱阻理論來解釋熔鹽熱物性的強(qiáng)化效果。為了進(jìn)一步驗證界面熱阻的實用性,分別采用了模擬、實驗兩種手段嘗試驗證該理論。發(fā)現(xiàn)了界面熱阻的存在證據(jù)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.
【學(xué)位授予單位】：華北電力大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TM615;TB383.1

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