Spectral, Directional Emittance of Stainless Steel at Elevated Temperatures

Stainless steel material samples with different surface roughness values were investigated to determine their spectral directional emissivity at elevated temperatures up to 1200 K in the visible to near-infrared wavelength range and in the infrared around 4  μm. The emissivity measurements were accomplished by measuring the radiation from an appropriately designed test specimen in a furnace heating facility with optical access. Blackbody radiation, needed to determine the emissivity, was generated through a cavity in the specimen itself. During the time of measurement, the sample was shielded from the furnace radiation through a retractable cold radiation shield. In the visible to near-infrared wavelength range, the specimen was imaged on the entrance slit of a 500 mm focal lengthspectrometer, enabling simultaneous measurement of a sample normal to the viewing direction, the blackbody cavity, and a tilted sample. In the infrared, a FLIR camera was used to image filtered radiation around 4  μm. Surface ro...