Directional Characteristics of Radiation Reflection on Rough Metal Surfaces with Description of Heat Transfer Parameters

Abstract

In this paper we clarify directional characteristics of thermal radiation reflection on rough metal surfaces and establish a technique for determining the parameters for heat transfer computation of radiation energy exchange among surfaces. Directional distribution of bidirectional reflectance ρ of surfaces of root-mean-square roughness Σ=0.1∼1μm to te irradiation of a visible laser of wavelength λ=0.6328μm and to that of an infrared laser of λ=3.39μm is investigated experimentally. The optical roughness (Σ/λ) ranges from 0.028 to 1.27. A measure of an order of specular reflection is presented. A model for describing the ρ-distribution is presented, and the experimental results of the ρ-distribution are analyzed quantitatively and systematically to determine the values of the specular reflection component R_s and the perfect-diffuse reflection component R_d of the hemispherical reflectance R_H, which are input parameters for radaiation heat transfer computation.