Analysis on spectral radiative properties of micro-scaled rough ligament surface inside open-cell nickel foam

Abstract

Accurately predicting the spectral radiative properties of ligament surface is vital for exploring the heat transfer inside open-cell foam materials. In this work, the complex morphology of ligament surface in open-cell nickel foam is reconstructed by analyzing the SEM scanning pictures of ligament surfaces. Then, the radiative parameters including the directional-hemispherical reflectivity, directional-directional reflectivity and proportion of specular reflection of rough ligament surface in the waveband from visible to near infrared light are numerically predicted by applying the FDTD method. Furthermore, the effects of incident angle and wavelength on the predicted radiative properties are compared and summarized. Besides, a fifth-degree polynomial is put forward for characterizing the directional-hemispherical reflectivities under different incident angles and wavelengths. The distributions of directional-directional reflectivities of ligament surface are compared and analyzed in order to predict the various value and dominated scope of reflection peak in the specular reflection direction. Additionally, the proportions of specular reflection under different incident conditions are achieved properly and characterized by proposed mathematical formulas. This work is helpful for the multi-scale numerical prediction of radiative transfer inside open-cell nickel foams, which is beneficial to further researches about engineering applications of open-cell foam materials.