泡沫镍孔隙尺度光谱辐射特性的实验与数值研究

Experimental and Numerical Study on Pore-Scale Spectral Radiative Properties of Ni Foam

实验测量了不同厚度的泡沫镍在0.4~2.2μm波长的法向-半球反射率/透射率,采用蒙特卡罗法对泡沫镍的计算机断层扫描结构进行孔隙尺度辐射传输建模,对比研究了泡沫镍辐射特性随入射光谱和样品厚度的变化,计算得到了泡沫镍辐射特性的孔隙尺度分布特征。结果表明:所建立的泡沫镍孔隙尺度辐射传输模型在计算其光谱辐射特性方面具有正确性。波长增长,吸收率逐渐降低,反射率逐渐升高;样品厚度增加,吸收率逐渐升高并趋于稳定,透射率逐渐降低至0。孔隙尺度辐射特性分布强烈依赖于局部纹理结构,波长1.5μm时,泡沫孔隙中的平均吸收率是肋筋上的1.5倍,而肋筋上的平均反射率则达到孔隙中平均反射率的3.7倍。

The experiment involves normal-hemisphere reflectance/transmittance from foam slices with different thickness at incident wavelength of 0.4-2.2 μm. The pore-scale radiative transfer simulation is modeled with Monte Carlo method applied in foam reconstruction from computed tomography. The radiative properties of Ni foam obtained from experiment and simulation are compared and the pore-scale distributions of radiative properties are analyzed. The results show that the pore-scale radiative transfer model is valid to simulate the radiative properties of Ni foam. The absorptance decreases and reflectance increases as the incident wavelength becomes longer. With samples thick enough, the absorptance increases to a stable value, while the transmittance decreases to zero. In addition, the pore-scale distributions of radiative properties are strongly dependent on the local structure. With incident wavelength of 1.5 μm, the absorptance in void pores is 1.5 times of that on solid skeletons. However, the reflectance on solid skeletons is 3.7 times of that in void pores.