CPC热管式真空管集热器传热模型的分析

【作者】 石玲；

【导师】 胡亚才； 洪荣华；

【作者基本信息】 浙江大学 ， 工程热物理， 2007， 硕士

【摘要】 本论文对CPC型热管式真空管集热器进行了理论研究，得出了复合抛物面的系统方程，构建了复合抛物面对太阳辐射的吸收模型和热管式真空管的传热模型，并通过计算分析得出了CPC型热管式真空管集热器瞬时集热效率与流体温差的变化关系。文章首先简要介绍了目前我国的能源状况，我国太阳能开发利用的优势，以及太阳能的热利用状况，在此基础上提出了本文的研究课题。CPC型热管式真空管集热器将复合抛物面和热管式真空管技术相结合，作为创新点，本文采用的热管式真空管中的热管为分离式热管。第二个创新点是将太阳能选择性吸收涂层涂在热管外表面和肋片表面，不同于以前涂在真空管内管表面。其次，根据杭州市的地理位置计算得出了杭州市的太阳辐照强度，可以看出杭州一年中7月份的太阳辐射最强，每小时太阳辐照强度的月平均值达到了819.63W／m~2，平均每天日照时间最长为13.95h。然后根据CPC型热管式真空管集热器复合抛物面的结构、安装位置和传热学基本原理，建立了CPC复合抛物面的系统方程以及对太阳辐射的吸收模型，最后计算出了7月份到达CPC型热管式真空管集热器接收器上的太阳辐射量。最后，应用传热学基本原理，构建了CPC型热管式真空管集热器中热管式真空管的传热模型。热管式真空管的内、外管之间是真空状态，所以对流和导热可以忽略不计。但是真空管内管与热管都存在着对流换热和热辐射。本文分析了CPC热管式真空管集热器的传热模型，并对CPC热管式真空管集热器进行了光学分析和传热学分析，最终得出了集热器的效率公式以及集热器瞬时集热效率与流体温差的变化关系。由于真空管内部采用分离式热管后，管内强制对流沸腾，过程很复杂，通常采用试验数据拟合的方法给出对应沸腾换热系数的关系式。计算结果表明根据CPC型热管式真空管集热器充分发挥了聚焦后能量密度提高的优势，适合在类似杭州这种江南典型气候地区使用，这种集热器在今后的发展中将有很大的潜力。更多还原

【Abstract】 CPC heat pipe evacuated tubular collector was studied in this thesis. The system equation of the compound parabolic was obtained, the solar radiation absorption model of the compound parabolic and the heat transfer model of the heat pipe evacuated tubular were constructed. The relationship of the instantaneous collector efficiency of CPC heat pipe evacuated tubular collector and the temperature difference of the fluid was solved.Firstly, the current situation of the energy development and the advantages to exploit solar energy in China were briefly introduced, the heat utilization condition of the solar is also expounded, which is the basis of this study. CPC heat pipe evacuated tubular collector integrate the compound parabolic and the heat pipe evacuated tubular technology, as an innovation, the separated type heat pipe was used in the heat pipe evacuated tubular in this paper. The other innovation is that the selective coating was covered on the surface of the heat pipe and the fins, not on the surface of inner tube of the evacuated tubular as before.Secondly, according to the location of Hangzhou, the solar radiation intensity in Hangzhou was obtained, and it is obvious that the solar radiation of July is the strongest in Hangzhou, Hourly average intensity of solar radiation reaches 819.63 W/m~2 in every month. The daily average sunshine which is the longest time in a year is 13.95h. According to the compound parabolic structure of CPC heat pipe evacuated tubular collector, the installation location and the heat transfer theory, the solar radiation absorption model was established. Then the amount of solar radiation of the receiver in CPC heat pipe evacuated tubular collector in July in Hangzhou was calculated.Finally, according to the basic principles of heat transfer, the heat transfer model of heat pipe evacuated tubular was proposed. For the heat pipe evacuated tubular, because it is vacuum between the inner and the outer tube, the convection and conduction can be neglected, but there is convective and radiation for the inner tube of the evacuated tubular and the heat pipe. The heat transfer model of CPC heat pipe evacuated tubular collector was studied, then the instantaneous collector efficiency equation was obtained through the optical analysis and heat transfer analysis for the collector, as well as the relationship of the instantaneous collector efficiency of CPC heat pipe evacuated tubular collector and the temperature difference of the fluid. The evaporation section of the separated type heat pipe is vertical, when the forced convection boiling is occurred in the heat pipe, the process is very complicated, what we can do is to fit the corresponding boiling heat transfer relationship according to the previous experimental data.The calculated results indicated that CPC heat pipe evacuated tubular collector fully played the advantages of enhancing energy density after focusing, meanwhile it is easy to combine with the construction in Hangzhou, therefore there will be great potential for CPC heat pipe evacuated tubular collector in the future.更多还原