Experimental studies of heat transfer between a bundle of horizontal tubes and a gas-solid fluidized bed of small particles

Abstract

Experimental data were obtained for the heat transfer coefficient between electrically-heated horizontal tube bundles and square fluidised beds of silica sand and alumina as a function of air fluidising velocity. Heat transfer data for a bundle of tubes are compared with a single tube under otherwise identical conditions, and are compared with existing correlations and theoretical models in the literature for maximum heat transfer coefficient. A correlation for the maximum heat transfer coefficient between horizontal tube bundles and a gas-solid fluidised bed of small particles is proposed which includes the influence of tube pitch in the bundle. This correlation will be particularly useful in the design of a low-rank coal fluidised-bed combustor where crushed coal is burnt in an inert bed of silica sand or alumina of particle size less than 1 mm.