Analysis on radiative energy transfer through fibrous layer considering fibrous orientation

By using the Monte Carlo method, radiative energy transfer through fibrous layer is analyzed. For the material of the layer, glass and nickel fibers are assumed. Mie scattering is assumed for the scattering mechanism by the fibers. The validity of these method is shown by comparing the results with the experiment obtained by Tong et al.. The heat fluxes through the layer for various temperature differences over the layer and for different thicknesses are predicted well by the method. In the present study, the directional profiles of the scattered radiative energy are obtained to study the effect of multiple-scattering. Two types of fiber orientations are considered: a three-dimensionally randomly oriented layer, and a layer which is oriented randomly in two-dimension and is parallel to the bounding surface. From the analysis, following results are obtained. (1) The heat flux through the layer with three-dimensionally randomly oriented fibrous layer is about 1.3 times larger than that with two-dimensionally randomly oriented layer. (2) The directional profile of scattered energy within the layer changes when the number of scattering is increased. (3) The average extinction efficiency for the radiative energy which has the above mentioned directional profile is almost the same for the layers with the two types of orientations. (4) The difference in the directional profile of scattered energy is the main cause to give the difference in the heat flux passes through the layer with different fiber orientations.