实验和理论方法研究ZnO粒子系的光谱辐射特性

Experiment and Theoretical Method Study of the Spectral Radiative Characteristics of ZnO Particles

在太阳能热化学两步法制氢过程中,金属氧化物颗粒物性随着体积分数、光程厚度的改变,对反应腔内颗粒系发生化学反应过程中辐射能量传递起着重要作用。为了获得ZnO颗粒系的光谱辐射特性,首先,实验方面采用悬浮液法测试了ZnO金属氧化物颗粒在300~1200nm下的光谱透射率。其次,理论研究了体积平均粒径d_(43)=13.9μm、面积平均粒径d_(32)=7.71μm表示下的ZnO金属氧化物颗粒的辐射特性。结果可知:对于d_(32)=7.71μm,其衰减系数、吸收系数、散射系数值分别约为2cm^(-1)、0.8cm^(-1)、1.2cm^(-1);d_(43)=13.9μm其衰减系数、吸收系数、散射系数值分别约为1.1cm^(-1)、0.5cm^(-1)、0.6cm^(-1)。通过对散射相函数以及散射不对称因子分析可知,光在传播中以前向散射为主,这样使太阳光更可能穿入粒子系内部。进而通过Mie理论结合比尔定律计算出两种粒径下的光谱透射率,通过与实验进行对比可知面积平均粒径d_(32)表示的粒子系透射率与实验结果更接近。最后采用面积平均粒径d_(32)并使用蒙特卡洛法模拟出不同厚度以及不同体积分数下的半球透射率、半球吸收率以及半球反射率。

In the two step hydrogen process of solar thermochemistry,with the change of volume fraction and thickness of optical path,the physical properties of metal oxide particles play an important role in the transmission of radiation energy in the reaction process of particles.In order to obtain the spectral radiation characteristics of ZnO particles,firstly,the spectral transmittance of ZnO metal oxide particles at 300~1200 nm was measured by suspension method.Secondly,the radiation characteristics of ZnO metal oxide particles with volume average size d 43=13.9 0x0E?SymbolmA@0x0Fm and area average particle size d 32=7.71 0x0E?SymbolmA@0x0Fm are studied theoretically.The results show that for d 32=7.71 0x0E?SymbolmA@0x0Fm,its attenuation,absorption and scattering coefficients are about 2 cm-1,0.8 cm-1 and 1.2 cm-1 respectively,and for d 43=13.9 0x0E?SymbolmA@0x0Fm,its attenuation,absorption and scattering coefficients are close to 1.1 cm-1,0.5 cm-1 and 0.6 cm-1 respectively.By analyzing the scattering phase function and the scattering asymmetry factor,it is known that the light is dominated by the forward scattering in the propagation,so that the sunlight is more likely to penetrate into the inner part of the particles.Then the spectral transmittance of two kinds of particles is calculated by Mie theory and BEER’s law.By comparing with the experimental results,it is found that the transmittance of the particle system represented by the area average size d 32 is closer to the experimental results.Finally,using the average particle size and Monte Carlo method to simulate the hemispherical transmittance,hemispherical absorption rate and hemispherical reflectivity of different thickness and volume fraction.