Study On Solar Air Collector With Transparent Honeycomb Made Of Glass Tube

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.