Heat Transfer between Fluidized Bed and Horizontal Bundle of Tubes in a Vertical Channel

Abstract

The present work aims to study the fluidization and heat transfer characteristics around a single horizontal heated tube, in-line tubes arrangement and staggered tubes arrangement immersed in a gas fluidized bed. The experiments were carried out on a square test section column (16 cm x 16 cm x 95 cm) from a steel sheet of 3 mm thickness. Each arrangement of the tubes is installed in a separate test section. The plane tube bank for both in-line and staggered tubes arrangement consists of 5 rows and four tubes per row in equal vertical and horizontal pitch arrangement. The experimental setup has a transition channel with the same square section and 30 cm height. The other side of the transition channel has one hole of 5 mm inside diameter and 30 mm long to measure the pressure before the distributor plate. The bed material used is sand particles of different sizes (1400 µm, 1600 µm, and 1850 µm). For the tested arrangements, the results show that the average heat transfer coefficient increases with the increase of the fluidizing velocity and with the decrease in particle diameter. Also, the comparison between the in-line and staggered tube arrangement showed that, the average heat transfer coefficient in case of staggered is higher than that of the in-line tube arrangement. Moreover, empirical correlations for the average Nusselt number of the tested arrangements using the experimental data are presented.