【作者】 张志强；

【导师】 左然；

【作者基本信息】 江苏大学 ， 工程热物理， 2008， 硕士

【摘要】 太阳能是最重要的可再生能源,它具有分布广泛、利用方便等优点。太阳能热利用的关键是太阳能集热器,如何减少其热损失是该领域研究的重点。透明蜂窝材料既能透过太阳辐射又具有优良的隔热性能,在太阳能集热器中有广阔的应用前景。本课题研究一种具有薄壁玻璃管透明蜂窝盖板的太阳能空气集热器,主要包含以下内容:1.设计制作了以薄壁玻璃管为蜂窝单元的透明蜂窝盖板,应用于平板型太阳能空气集热器,并对其进行了试验和模拟分析。对五种具有不同尺寸的透明蜂窝盖板的太阳能集热器进行试验研究。重点研究在小高宽比(L/D＜3)下,蜂窝的孔径、高宽比等因素对阳光透过率和集热效率的影响。结果显示:在试验条件下,当蜂窝直径相同,高宽比不同时,集热器出口温度相差较大,高宽比小的温度高,最大温差约为10℃;当蜂窝直径不同,高宽比相同时,集热器出口温度相差不大。有蜂窝与无蜂窝,最大温差约为12℃。2.透过率是影响透明蜂窝性能的重要指标之一。针对现有计算关系式较为复杂的问题,作者通过对玻璃管蜂窝单元的分析,推导出关于蜂窝结构透过率的简单计算式。该计算式仅于蜂窝的高宽比L/D以及材料的光学性质有关,而与蜂窝的具体尺寸无关。3.利用FLUENT软件,对不同直径、不同高宽比的多种蜂窝进行了数值模拟,研究蜂窝高宽比、直径、放置角度等因素对蜂窝内流场及温场的影响。结果表明:试验所采用的几种玻璃管蜂窝,因几何尺寸较大,内部的自然对流都没有被抑制住。只有当蜂窝垂直放置、且直径较小≤10mm时才能抑制住自然对流。倾斜放置的蜂窝,内部均有自然对流。蜂窝内流场强度随蜂窝直径的增大而增强。对相同直径的蜂窝,内部对流强度随其高宽比的增大而减弱。模拟结果对实际应用时,选用透明蜂窝结构有一定的指导意义。4.对平板式太阳能空气集热器的有效得热及各部分散热做了详细分析与理论计算,并在此基础上计算出试验用集热器的热效率,得出了与试验测试结果基本一致的结论。5.最后,作者对V型槽聚光器的聚光特性进行了详细分析,并推导出不同情况下聚光度与几何聚焦比、光线入射角的计算关系式。通过计算表明,V型槽聚光器的最大聚光倍数为3。并给出适合应用的V型槽的仰角及几何聚焦比的取值范围,用于指导其在聚光型太阳能集热器以及聚光型太阳能光伏系统中的应用。更多还原

【Abstract】 Solar energy is the most important energy of all sorts of renewable ones. It’s widely distributed and convenient for use. Solar collector is one of the most important components in the utilization of solar thermal technology. How to reduce the heat loss is the important subject of this field. Transparent honeycomb is a new kind of transparent insulation materials, which allows the solar radiation go through into the reactor, at the same time, it reduces the heat loss. In this thesis, we study the flat-plate solar air collector with transparent honeycomb cover made of thin-walled glass tube. The thesis includes following aspects.1. Transparent honeycomb structure with thin-walled glass tube as the honeycomb unit is designed and applied to a flat-plate solar air collector. Experiments are performed for the solar collectors with six different honeycomb sizes. The emphasis is to study the effects of diameter and aspect ratio of the honeycomb unit to the transmittance and efficiency of the solar collector. The results show that, for the same diameter but different aspect ratios, there are large temperature differences between the collector’s exits; the smaller the aspect ratio, the larger the exit temperature, with maximum difference of 10℃; for the same aspect ratio but different diameters, the temperature differences are small; the maximum temperature difference between the collectors with and without honeycombs is 12℃.2. Transmittance of transparent honeycomb is one of the important performance index.The existing calculation formula is rather convoluted, and a theoretical expression for the honeycomb transmittance is derived with a simplified method. The result shows that the honeycomb transmittance is only related with the aspect ratio and the materials’ optical properties, but not related with the honeycomb actual size.3. Using the FLUENT Software in numerically simulating the transparent honeycomb of different aspect ratio. To investigate the effect of aspect ratio of honeycomb on velocity field and temperature field inside. The results show that: the internal natural convection have not been effectively suppressed because of relatively larger geometr of the honeycomb made of glass tube using in experiment. In addition, the numerically simulation analysis of several honeycombs with different diameters and aspect ratio, the results indicat that natural convection can be effectively suppressed while the diameter of honeycomb smaller than 10mm . The natural convection inside could not be suppressed While the honeycomb diameter larger than 20 mm. The strength of flow field increase with cellular’ diameter, and decrease with aspect ratio. The results give a guideline of choice of transparent honeycomb structure in practical application.4. A detailed thermal analysis of the solar air collector have been achieved and its theoretical thermal efficiency also be calculated which gives good predictions for the experimental results.5. Finally, a detailed concentration ratio analysis and calculation of a kind of low rate concentrators have been carried out which supplies guidance for the focussing type solar collectors and Photovoltaic System.更多还原