THERMOREGULATED FIBEROPTIC PROBE VALIDATION FOR TEMPERATURE DETERMINATION IN SPITE OF RADIATION DISTURBANCES

A methodology has been developed for measuring surface temperatures at high temperature in highly hostile environments, in spite of material thermoradiative properties and radiation interferences. The measurement technique is bichromatic optical pyrometry. The radiometer is connected to a fiber-optic probe coupled with a reflecting hemisphere head. When reducing the distance between probe and target, the correction on measured temperature improves but meanwhile the thermal disturbance on target increases. The purpose of this work consists in a complete analysis of this process. Experiments were performed on platinum and graphite. The samples were submitted to high flux obtained from concentrated solar energy or Joule effect. The measured temperatures are analyzed to get meaningful temperatures and thermal disturbances variation versus the distance between probe and target at various temperature levels. Experimental and theoretical results are compared. Temperature evolutions are concordant with literature emissivity data. As for thermal disturbance, the concordance is very good at an optimal distance of 1 mm, somewhat worse at longer distances and worse at very short distances. Nevertheless, these first tests results and simulation prove that great confidence could be accorded to this methodology provided other experiments and calculation with different boundary conditions are performed.