A New Spectrophotometer System for Measuring Hemispherical Reflectance and Normal Emittance of Real Surfaces Simultaneously

A new spectrophotometer system is developed for the study of thermal radiation characteristics of real surfaces in thermal engineering environments. The system measures spectra of normal incidence hemispherical reflectance RNH and normal emittance EN in the near-ultraviolet through infrared region of wavelength of 0.30 μm to 11 μm simultaneously and repeatedly with a cycle time of 4 s. The system enables evaluation of the normal incidence absorptance AN in this wide spectral region. Transitions of spectra of specular-finished and rough-finished nickel surfaces in a high-temperature air-oxidation process are measured to demonstrate the performance of the system. Clear interference behaviors are found even in the spectra of hemispherical reflectance RNH and emittance EN of a rough-finished surface

New Spectrophotometer System for Measuring Thermal Radiation Characteristics of Real Surfaces of Thermal Engineering Entirely

In this work we develop a new spectrophotometer system for measuring thermal radiation characteristics of real surfaces of thermal engineering. This system measures transition of spectra of normal incidence hemispherical reflectance RNH, normal incidence specular reflectance RNN, normal incidence diffuse reflectance RND, normal incidence absorptance AN and normal emittance εN of real surfaces in a near-ultraviolet through infrared region of wavelength 0.30∼11 µm simultaneously and repeatedly with a cycle time of 6 s. The system is applied to measure the spectrum transition of the reflectances, absorptance and emittance of a nickel surface which is prepared as a clean optically smooth surface and is oxidized in high-temperature air to be changed to an oxidized rough real surface. Microscopic mechanisms of the spectrum transition are discussed, to illustrate the performance of the developed spectrophotometer system for thermal engineering applications

Interference of spherical wave of thermal radiation emitted by a film system

This paper deals with the interference of spherical waves of thermal radiation emitted by a surface film system which consists of a metal substrate and a semi-transparent film. A spectroscopic experiment is made to reconfirm the clear interference in emission spectra of the film system. We present a theoretical model in which an electromagnetic theory for a spherical wave is combined with Planck’s theory of thermal radiation. The mechanism of interference of spherical waves is discussed, and it is suggested that thermal radiation waves emitted by a number of dipoles of the metal might be coherent among each other