Abstract The reflectance losses are the predominate energy losses in solar radiation transfer process for the porous volumetric solar receiver. However, few studies pay attention to the influence of geometrical parameters of porous media on the reflectance losses, and the data of reflectance losses of porous volumetric solar receiver in solar spectrum is not complete. In this paper, both experimental and numerical simulation methods are applied to comprehensively investigate the reflectance losses of the porous volumetric solar receiver. A series of silicon carbide reticulated porous ceramics (SiC RPCs) is fabricated by replica method and recoating technique. The reflectance losses are measured based on UV-VIS-NIR spectrophotometer. Meanwhile, porous models with different geometrical parameters are artificially reconstructed. Monte Carlo Ray Tracing method is used to calculate the total reflectance. The results present that the SiC RPCs exhibit small reflectance losses in the solar spectrum with a peak at about 420 nm. The geometrical parameters, such as porosity and pore diameter do not change the spectral behavior but only influence the magnitude of the reflectance. Larger porosity and larger pore diameter are beneficial for reducing the reflectance losses. The correlation of the reflectance losses as functions of pore density and porosity has been developed. Furthermore, the influence of the incident angle of radiation on reflectance losses is studied. Relatively large increase is observed as the incident angle is larger than 30°. This phenomenon becomes more obvious for the porous media with larger porosity or larger pore diameter.

中文翻译：

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多孔体积太阳能接收器反射损失的实验和数值研究

摘要 反射损失是多孔体积太阳能接收器在太阳辐射传递过程中的主要能量损失。然而，很少有研究关注多孔介质的几何参数对反射率损失的影响，并且太阳光谱中多孔体积太阳能接收器的反射率损失数据并不完整。在本文中，应用实验和数值模拟方法来综合研究多孔体积太阳能接收器的反射损失。采用复制法和重涂技术制备了一系列碳化硅网状多孔陶瓷（SiC RPCs）。基于UV-VIS-NIR分光光度计测量反射损失。同时，人工重建具有不同几何参数的多孔模型。Monte Carlo Ray Tracing方法用于计算总反射率。结果表明，碳化硅 RPC 在太阳光谱中表现出小的反射损失，峰值在 420 nm 左右。孔隙率和孔径等几何参数不会改变光谱行为，而只会影响反射率的大小。较大的孔隙率和较大的孔径有利于减少反射损失。已经开发了作为孔隙密度和孔隙度函数的反射损失的相关性。此外，研究了辐射入射角对反射损失的影响。当入射角大于 30° 时，观察到相对较大的增加。对于孔隙率较大或孔径较大的多孔介质，这种现象更为明显。