Optical parameters for characterization of thermal radiation in ceramic sponges - Experimental results and correlation

In this publication, experimental results for the spectral transmittance and reflectance obtained by Fourier transform infrared spectrometry (FTIR) for different ceramic sponges (variations of material, porosity and cell density) are presented. Within these parameters, the total extinction coefficient (here: Rosseland extinction coefficient) and the total emissivity of the different sponges investigated are determined. The total extinction coefficient reveals a strong dependency on cell size and porosity while the total emissivity only depends on porosity. These optical parameters allow the estimation of radiative heat transfer in ceramic sponges. Furthermore, an empirical correlation for predicting the total extinction coefficient from the window diameter is proposed. The radiative part of the thermal conductivity of ceramic sponges can be estimated using the Rosseland extinction coefficients obtained.