engleski

Heat Transfer Coefficients at a Pipe Coil Submerged to the Fluidized Bed

The values of heat transfer coefficients at the surface of a pipe coil horizontally submerged to a fluidized bed, obtained by combining experimental measurements and computation, are presented in the paper. The fluidized system is air to quartz sand. The experiments were performed with three sand granulations: 0.358 ; 0.630 and 0.800 mm. The fluidized bed, agitated with air at room temperature, is used to cool a flow of hot water streaming through a submerged pipe coil probe. The mass flow rates of the hot water and fluidizing air are varied and their intensities, input and output temperatures measured. A computational algorithm is developed to calculate the heat transfer coefficient between the coil surface and the fluidized bed from the measured data. The results are presented using the nondimensional relation: Nu = f ( ƒŐmf , Re, Ar ) The functional relation is obtained by applying the least squares method. The measured values apply to the fluidized bed working points in the vicinity of the optimum fluidization velocity of the air. The obtained values of the heat transfer coefficients are in fair accordance with those derived from the Zabrodsky formula.

heat transfer coefficients; fluidized bed

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