Radiative heat transfer through opacified fibers and powders

Radiative heat transfer through opacified (metallic or metallized) cylindrical fibers and spherical powders is investigated theoretically. The radiative properties of these packed particles are evaluated by using the solutions of electromagnetic theory. The large optical constants and large particle size parameters require an improved numerical scheme for evaluation of these properties. The results show that fine metal fibers provide excellent thermal radiation resistance. For the packed spheres, the high solid volume fraction restricts the present model to the geometric scattering regime. The results in this regime indicate better radiation resistance for smaller spheres. It is also interesting to note that, relative to unopacified spheres, the opacified spheres have higher thermal radiation resistance only at high temperatures.