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Transport Phenomena in Thermal Engineering. Volume 2

ISBN:
1-56700-015-0 (Print)

HEAT TRANSFER TO HORIZONTAL FINNED TUBE BUNDLES IN THE FREEBOARD REGION OF FLUIDIZED BED

Y. Katoh
Department of Mechanical Engineering, Yamaguchi University Tokiwadai, Ube 755, Japan

Masahide Miyamoto
Department of Mechanical Engineering, Yamaguchi University Tokiwadai, Ube 755, Japan

Y. Idei
UBE Industry Co. Ltd., 1980 Okinoyama, Ube 755, JAPAN

Abstract

This study was carried out on the heat transfer of horizontal finned tube bundles in the freeboard region of fluidized bed experimentally. The bed consisted of a cross sectional area of 400×400 mm and a height of 1020mm. Each finned tube arrangement in the staggered two rows had a spiral welded fin that had a height of 19.4mm, a thickness of 2mm and a pitch of 9mm, around a 34mm diameter steel tube. Two kinds of the mean diameters of the fluidized particles were used; dp=0.86mm and 0.45mm.
Consequently, it was found that the average heat transfer coefficient of finned tube was smaller than that of bared one because those finned tubes prevented the particle behavior from becoming in the more activity and then taking the higher expansion bed height of the particles. It was also found that the ratio of heat transfer on finned tube to that on bared tube approached to the value of 0.6 when those whole tubes completely were immersed in the bed. Furthermore, the volume goodness factors (VGF) such as the Estd and Hstd were taken account of estimating the present data. The Estd and Hstd meant the work of efficiency and the standard heat transfer coefficient, respectively. As a result, it was clarified that the smaller diameter of particles, the lower height of tubes and the appropriate height of the static bed as the bed conditions should be chosen, though there are some kinds of limitation to obtain the higher heat transfer coefficient.