Development of a High-Speed Reflectometer for Measuring Hemispherical Reflection Characteristics

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A new reflectometer has been developed for measuring thermal radiation characteristics of real surfaces, which are rough and/or contaminated in thermal engineering environments. This reflectometer uses two ellipsoidal mirrors and a semi-transparent mirror, and measures a spectrum of hemispherical reflectance for perfect-diffuse hemispherical irradiation R_<HH> in the visible through nearinfrared spectral region of 0.35-1.1mum. The reflectometer also measures the spectra of the normal-incident hemispherical reflectance R_<NH> and the oblique ring-incident hemispherical reflectance R_<ObH>. This reflectometer is the first instrument to measure the reflectances directly related to the absorptances for heat transfer engineering.Experimental verification has been made on some real surfaces, and theoretical/ modelling studies have been made to back up the principles of the developed measuring technique. Expansion of the measuring spectral region to the infrared , development of the hemispherical transmittance measurement technique and advanced systematic modelling works are recommended for the future study.