The use of materials in high temperature environments is required in a variety of applications such as re-entry vehicles, jet propulsion systems, hypersonic tunnels, nuclear reactors, solar energy, and the like. Thermal analysis in these areas requires a knowledge of the surface radiative properties of the materials at high temperatures. The accurate retrieval of surface temperatures, as well as radiative heat losses, requires knowledge of the spectral emissivity of these materials at corresponding temperatures. These emissivity measurements depend on parameters such as the temperature of the surface, geometry of the surface, chemical composition of the sample, state of the sample environment and the direction, wavelength and polarization of incoming thermal radiation.
The spectral emissivity of a surface, with values varying from zero to unity, is defined as the ratio of the radiation emitted from a surface to that of a blackbody at the same temperature and wavelength. Various emissivity measurement systems, including the use of a coated integrating sphere, are well documented in the literature. The integrating sphere has the ability of collecting all reflected radiation, while removing any directional preferences, and presenting an integrated signal to the detector.
In the present invention an improved emissivity measurement system employing a novel integrating sphere has been developed.
Accordingly, one object of the present invention is to provide a novel emissivity measurement system.
Another object of the present invention is a high temperature directional spectral emissivity measurement system for opaque surfaces employing an integrating sphere.
A further object of the present invention is an improved accuracy directional spectral emissivity measurement system employing a monochromatic light source.
An additional object of the present invention is a novel sample heating and placement system for use with an integrating sphere emissivity measurement system.
Another object of the present invention is a novel movable monochromatic light assembly for use with an integrating sphere.
A further object of the present invention is a system for measuring the surface emissivity of a high temperature test sample at any elevated temperature, at any wavelength and at any angle.