Computer-Controlled Apparatus for the Measurement of the Normal Spectral Emissivity of Materials

摘要

A need exists for the measurement of the thermal radiative properties of materials, especially in the infrared region of the electromagnetic spectrum at moderate to high temperatures. To meet this need, an automated apparatus for the measurement of the normal spectral emissivity from 2-15 microns in the temperature range of 500 C to incandescence has been designed, fabricated and tested. The integral blockbody method was chosen whereby a metallic foil or ribbon is formed into a tube shape and is heated by the passage of direct current. The system is described, and sources of error are briefly outlined. Most materials used in engineering systems do no have atomically clean surfaces but come with 'as is' surfaces. Hence, one needs to investigate the radiative properties of these real surfaces. Results of the measurement of the normal spectral emissivity of an 'as is' tungsten surface from 2-6 microns at 700 C and 900 C are given. The present data is compared with literature values on annealed tungsten samples. These results demonstrate that the present system functions properly and will provide a valuable tool for the rapid assessment of the emissive properties of materials.