CPC内的漫反射及对能量收集的影响
CPC内的漫反射及对能量收集的影响
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DOI：
10.1016/j.solener.2015.07.016
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发表时间：
2015
期刊：
影响因子：
6.7
通讯作者：
唐润生
中科院分区：
文献类型：
--
作者：
余亚梅;唐润生
在实际应用中，复合抛物面聚光器（CPC）由于反射面形状不理想、表面粗糙、灰尘沉积等原因，部分入射到反射面上的太阳光线发生漫反射而不是镜面反射，导致相当一部分太阳光线从聚光器腔体中逃逸，使聚光器的光学性能下降。本文基于二维辐射传输理论，建立了计算半漫反射体和单面平板吸收体复合光子晶体光学效率因子的数学模型，并从理论上分析了复合光子晶体内部漫反射对能量收集的影响。光线追迹分析表明，半漫反射器的使用只能使吸收体上的太阳辐射更加均匀，而完全漫反射器的使用则会导致聚光效率的降低。理论预期和光线追迹模拟得到的光学效率因子之间的比较表明，在这项工作中提出的数学模型可以准确地估计这种CPC的光学性能。理论计算表明，由于从反射体到吸收体的漫辐射传输形状因子很小，CPC内部的漫反射对CPC辐射收集的贡献很有限;对于给定的总反射率，CPC的年平均光学浓度随反射体漫反射率的增大而减小。
In practical applications, part of solar rays incidence on reflectors of compound parabolic concentrators (CPC, in short) undergoes diffuse reflections instead of specular reflections due to imperfect reflector profile, rough surface and dust deposition, leading a considerable fraction of solar rays escape from the cavity of CPCs and making their optical performance decrease. In this article, a detailed mathematical procedure to estimate the optical efficiency factor of CPCs with semi-diffuse reflectors and one-sided flat absorber is developed based on the knowledge of two-dimensional radiation transfer, and the effect of diffuse reflections within the CPC on its energy collection is theoretically investigated. Ray-tracing analysis shows that the use of semi-diffuse reflectors in CPCs can not make solar flux on the absorber more uniform except using perfect diffuse reflectors, in turn leads the optical efficiency decrease. Comparisons of the optical efficiency factors between theoretically expected and those obtained by ray-tracing simulation indicate that the mathematical model proposed in this work can accurately estimate the optical performance of such CPC. Theoretical calculations show that the contribution of diffuse reflections within CPCs to the radiation collection of CPCs is limited as a result of the fact that the diffuse radiation transfer shape factor from the reflectors to the absorber is very small, and the annual average optical concentration decreases with the increase of diffuse reflectivity of reflectors for CPCs with a given total reflectivity.