Modeling of a Fluidized Bed Combustor with Immersed Tubes: Quarterly Report

S. C. Saxena · N. S. Grewal · University of Illinois at Chicago Circle. Department of Energy Engineering

jan. 1977 · U.S. Government Printing Office

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Progress is reported in the development of a mathematical model of a fluidized-bed combustor. The model will include coal combustion phenomena and will incorporate basic mass transport relationships, bubble mechanics, heat transfer and configuration effects. A cold model test bed will be designed, constructed and operated to generate data in support of the effort in developing the mathematical model. In particular, experiments will provide data concerning heat transfer effects of tubes and tube bundles in fluidized beds, bubble formation, dispersion etc. Experiments have been carried out to measure the total heat transfer coefficient between 12.7 mm diameter copper tubes with different surface roughness and glass beads of different sizes. The comparison of results for the rough and technically smooth tubes revealed that the heat transfer coefficient strongly depends on the ratio of pitch (P) to particle diameter anti d/sub p/). By the proper choice of this ratio, P/anti d/sub p/, the total maximum heat transfer coefficient could be increased by as much as 40% over the value for a smooth tube with the same outside diameter. However, if P/anti d/sub p/ ratio is less than unity, the maximum heat transfer coefficient for rough tube is smaller as compared to the smooth tube. The design of the two end plates of the fluidized bed for mounting tube bundles of varying configuration and pitches has been completed and is currently under fabrication in the departmental workshop.