Study on Reduction Effect of Natural Convection in a Horizontal Porous Media with High Density Layer at the Middle

( Evaluation with Aiming at Effective Density )

Abstract

Light-weight and high-performance thermal insulator made of fibrous porous media has been developed. But, when its density is too low, natural convection occurs in it and its performance decreases. In order to reduce weight moreover and suppresses natural convection, inserting high-density layer in a thermal insulator at the middle seems to be promising. However, it is not clear what high-density layer is effective. Therefore, in this study, fluid flow and temperature distribution in a horizontal porous layer with high-density or impermeable layer at the middle were investigated numerically. The porous layer was heated from below and the optimum combination of densities was examined from the viewpoint of weight. The arithmetic expression by the fiber model of Cho et.al. was applied to estimate the permeability of porous layer.