Properties of an optical fluid filter: Theoretical evaluations and measurement results

Abstract
The DLR solar furnace in Cologne has been working successfully since 1994 to allow high flux tests in the field of solar chemistry and materials research. Sophisticated measurement technique like the Flux and Temperature Measurement System (FATMES) and the High Flux Spectrometer (HIS) support the evaluation of measurement results. The efficiency of the DLR measurement equipment is demonstrated by means of determination optical properties of a fluid filter. Additionally obtained measurement results are compared with theoretical calculations. The fluid filter was designed, constructed and tested to absorb undesired radiation before entering photochemical reactors. As a first application the filter was filled with water to absorb the IR part of the solar spectrum. Due to the changes in the spectral content of the concentrated radiation the flux measurement system had to be calibrated especially for the employment of the water filter. Each filter thickness requires its own calibration. This lead to an intensive measurement campaign to determine the optical properties of the fluid filter and the efficiency of the measurement equipment.