Experimental study on the radiative properties of open-cell porous ceramics

Open-cell porous ceramic is an ideal volumetric heat absorbing material, and understanding in detail the thermal properties of the material, particularly its radiative properties, is of primary importance for the design and improvement of volumetric solar receivers. This work investigates the radiative properties of open-cell porous ceramic through experiment. Fourier transform infrared spectroscopy (FTIR) was applied to measure the spectral transmittance of open-cell porous ceramic samples with different porosities and cell densities in infrared wavelengths between 2.5 and 25 μm. The results were analyzed to determine the spectral extinction coefficient and Rosseland extinction coefficient, which showed that the radiative properties of porous ceramic are strongly dependent on its microstructure parameters, while the type of material has little influence. The spectral extinction coefficient and Rosseland extinction coefficient both increased with increasing cell density and decreasing porosity. Based on the experimental results, two empirical correlations related to the window diameter and porosity were proposed to predict the Rosseland extinction coefficient of open-cell porous ceramics. Finally, the radiative thermal conductivities of different porous ceramics were studied.