RADIATION TRANSFER IN FIBROUS MEDIA WITH LARGE SIZE PARAMETER

DOI: 10.1615/ICHMT.1995.RadTransfProc.240

Jun Yamada
Dep. of Mech. Eng. SIT, Tokyo, Japan

Yasuo Kurosaki
Department of Mechanical Engineering and Intelligent Systems, University of Electro-Communications; and Tokyo Institute of Technology, Japan

Abstract

This paper numerically investigates radiation transfer in fibrous media with a large size parameter using a pseudo-continuous model. Radiation scattering from a single fiber is first approximated by summing the specular reflection on the fiber surface and the Fraunhofer diffraction of a rectangular aperture that is considered to be a single fiber. Next, the obtained radiation diffraction and reflection are used to derive approximate solutions for estimating the optical characteristics of fibers which are required in this model, i.e., the extinction and scattering efficiencies. By comparing the approximate and conventionally used exact solutions, the utility of the approximate solutions is verified for a size parameter over than 50 and absorption index more than 0.1. In addition, using the optical characteristics obtained by the approximate solutions in combination with the exact solutions, radiation transfer is estimated in two types of planar fibrous media with a typical fiber orientation. Such methodology is shown to determine how the radiation transfer in media is effected by the optical constant of fibers, fiber diameter, and orientation of the media.