Heat transfer in gas-solid fluidized bed with various heater inclinations

The study explored the heat transfer properties in an air-fluidized bed of sand, heated with an immersed heat transfer tube positioned at several angles of inclination. Operating with fluidizing velocity up to 0.5 m/s: and particles of 150-350 mu m diameter, the effect of air velocity and particle size on the average and maximum achieved heat transfer coefficient was examined for the heat transfer tube at angles of inclination in the range 0-90 degrees. Experimental results showed that the angle of inclination altered the bubble size and behavior close to the heat transfer tube hence the expected heat transfer coefficient, with the influence of tube inclination being less pronounced for smaller particles. The optimum angle of inclination was in the range of 10-15 degrees relative to the direction of the flow, while the heat transfer coefficient had its lowest values at the angle of 45 degrees, and thereafter improved upon transition to 90 degrees. Upon comparison with existing correlations, a correction factor is proposed to account for the impact of the angle of inclination on the heat transfer coefficient calculated by the Molerus-Wirth semi-empirical correlation. (C) 2011 Elsevier Ltd. All rights reserved.