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 . 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 length spectrometer, 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 . Surface roughness increased emissivity significantly in comparison to polished samples. The actual roughness values only had minor effects. Preoxidation of the samples caused a significant increase in emissivity for polished surfaces but had only minor effects for rough samples. The measured emissivities show only a weak variation with temperature.
Spectral, Directional Emittance of Stainless Steel at Elevated Temperatures
Journal of Thermophysics and Heat Transfer ; 33 , 2 ; 495-507
2018-12-12
13 pages
Article (Journal)
Electronic Resource
English
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