EXPERIMENTAL EVALUATION OF RADIATION REFLECTION CHARACTERISTICS OF REAL SURFACES FOR HEAT TRANSFER COMPUTATION

This paper aims to clarify thermal radiation reflection characteristics of rough surfaces and to establish a technique for determining the parameters for heat transfer computation of radiation energy exchange among surfaces. Directional distribution of bidirectional reflectance ρ of metallic surfaces of root-mean-square roughness Σ=0-1~1 to the irradiation of a visible laser of wavelength λ=0.6328 µm and to that of an infrared laser of λ=3.39 µm is investigated experimentally. The optical roughness (Σ/λ) ranges from 0.028 to 1.27. A measure of specular reflection is presented. A model for describing the ρ -distribution is presented, and the experimental results of the ρ -distribution are analyzed to drive the values of input parameters for heat transfer computation quantitatively and systematically.