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International Heat Transfer Conference 6

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

AN ANALYSIS ON THE RADIATIVE AND FREE CONVECTIVE HEAT TRANSFER IN A HORIZONTAL ANNULUS WITH PERMEABLE INSULATOR

Ryozo Echigo
Department of Mechanical Engineering and Science, Tokyo Institute of Technology, Meguro-ku, Tokyo, Japan

Shu Hasegawa
Department of Nuclear Engineering, Faculty of Engineering, Kyushu University, Fukuoka 812, Japan

S. Tottori
Kyushu University, Fukuoka 8l2 JAPAN

H. Shimomura
Japan Atomic Energy Research Institute, Ibaragi 319-11 JAPAN

Yoshizo Okamoto
Japan Atomic Energy Research Institute, Ibaragi 319-11 JAPAN

DOI: 10.1615/IHTC6.4260
pages 385-390

Abstract

This paper presents an analytical procedure for predicting the heat transfer characteristics on the simultaneous radiation and free convection in permeable insulator. The momentum and energy equations are formulated by taking account of the radiative propagation based on the Rosseland (opaque) approximation and solved numerically by finite difference schemes under two different boundary conditions for the outer shell, that is, one is the case of assuming the inner surface temperature of the outer shell to be uniform and the other is the problem in which the angular profile of the heat transfer coefficients of the outer surface is given. In case of uniform temperature boundary the effects of dimensionless parameters such as Rayleigh number Ra, Darcy number Da and the radiation-conduction parameter NR on the flow fields and the temperature profiles are examined in detail, particularly, the thermal radiation effects on the commencement of the convective flow and the resulting heat transfer characteristics are discussed quantitatively. Concerning the latter boundary condition a new analytical method is developed for the continuation of the analytical solution obtained in the outer shell to the numerical one in the permeable medium by eliminating the undetermined constants based on the boundary conditions at the porous-solid interface and also at the outer boundary of outer shell. The validity of this approach is confirmed by executing the numerical calculations for typical dimensionless parameters relevant to practical purposes.

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