Experimental Determination of the Extinction Coefficient for a Packed-Bed Particulate Medium

The extinction coefficient of a powder mixture of ZnO and beech charcoal is determined at ambient temperature using two experimental set-ups: (a) radiation in the range 500–1000 nm is captured by a 200 μm-diameter fiber optic and sent to a spectrometer equipped with a Si/PbSe detector; (b) radiation in the range 350–1100 nm is captured by a 5 mm-diameter Si-photodiode. Both set-ups measure the attenuation of intensity from a 3273 K blackbody source. The experimental results are implemented in the numerical solution of the equation of radiative transfer, using the Monte-Carlo ray-tracing technique. The extinction coefficient is determined to be 10103 ± 615 m⁻¹ at 1000 nm using set up (a), and 7850 ± 337 m⁻¹ for the range 350–1100 nm using the more accurate set-up (b).

Keywords:

• thermal radiation
• extinction coefficient
• Monte Carlo
• porous media
• packed bed

This study was performed within the framework of the European Union research project SOLZINC. The authors gratefully acknowledge the financial support from the EU and the BBW-Swiss Federal Office of Education and Science.