“ Trends in the Development of Machinery and Associated Technology ” TMT 2008 , Istanbul , Turkey , 26-30 August , 2008 NUMERICAL ANALYSIS OF THE EFFECT OF OPERATIONAL PARAMETERS OF HEAT TRANSFER SURFACES IN CFBS
The design or scale-up of heat transfer systems in fluidized beds require estimation of the effective heat transfer coefficient on heat transfer surfaces in contact with the fluidized medium. In this study, the effects of operational parameters on bed-to-wall heat transfer in CFBs is investigated such as solids volume fraction, particle diameter, suspension density, superficial velocity and solid circulation rate, using modified cluster renewal model. In the modified cluster renewal model, the gas phase properties are used for the dilute phase and similarly the solid phase properties are used for the cluster phase. The gas phase and the solid phase properties are considered in the control volume which is in the vicinity of the heat transfer surface.
Heat transfer in circulating fluidized beds
Circulating fluidized beds involving combustion or exothermic reaction commonly require heat transfer to the bed walls. The heat transfer helps to control the bed temperature and serves as a primary means to generate steam or hot water from the bed.
Emulsion layer model for wall heat transfer in a circulating fluidized bed
In this paper, an emulsion layer model is presented which predicts the thickness of a downward-moving emulsion layer along the wall of a circulating fluidized bed, the mean solids velocity, and the solids flux in the layer. Also presented is a heat transfer model which, in combination with the emulsion layer model, predicts the low-temperature data very well. An alternate slab model proposed for the radiative component in a high-temperature circulating fluidized bed agrees well with experimental data. The heat transfer predictions of the overall model for such operating parameters as solid circulation flux, suspension temperature, length of the heat transfer surface, superficial gas velocity, and mean particle size are in good agreement with the published data for long surfaces.